NASA TECHNICAL NOTE · ERRATA NASA Technical Note D-5131 &,#a&? s-& EFFECT OF ULTRASONIC VIBRATION...

NASA TECHNICAL NOTE

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EFFECT OF ULTRASONIC VIBRATION O N PRECIPITATION HARDENING OF STEELS AND SUPERALLOYS

by Stanley GI Young and LaLeonard Lewis Research Center CZeveZand, Ohio

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. MARCH 1969

NASA TECHNICAL NOTE NASA TN D-5131

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LOAN COPY: RETURN TO AFWl (WLll-2)

KIRTLAND AFB, N MEX

EFFECT OF ULTRASONIC VIBRATION ON PRECIPIT ATION HARDENING OF STEELS AND SUPERALLOYS

by Stanley G. Young and L. Leonard

Lewis Research Center

Cleveland, Ohio

"

NATIONAl AERONAUTICS AND SPACE ADMINISTRATION • WASHINGTON, D. C. • MARCH 1969

https://ntrs.nasa.gov/search.jsp?R=19690012452 2020-03-18T11:08:25+00:00Z

ERRATA

NASA Technical Note D-5131

&,#a&? s-& EFFECT OF ULTRASONIC VIBRATION ON PRECIPITATION

HARDENING OF STEELS AND SUPERALLOYS


March 1969

The following references should be added at the end of the report:

15. Decker, R. F.; Eash, J. T. ; and Goldman, A. J.: 18%Nickel Maraging Steel. Trans. ASM, vol. 55, no. 1, Mar . 1962, pp. 58-76.

16. Contractor, G. P.: The Marvel of Maraging. J. Metals, vol. 18, no. 8, Aug. 1966, pp. 938-946.

17. Anon. : Precipitation Hardenable Stainless Steels. Bull. 1223R4 75 C 1262, Republic Steel Corp. , 1962.

18. Anon. : Haynes Alloy No. R-41. Haynes Stellite Bull. No. F-30, 155 B, Union C a r bide Stellite Co., Apr. 1963.

19. Sandrock, Gary D. ; and Leonard, L. : Cold Reduction as a Means of Reducing Embrittlement of a Cobalt-Base Alloy (L-605). NASA TN D-3528, 1966.

20. Young, Stanley G. ; and Johnston, James R. : Accelerated Cavitation Damage of Steels and Superalloys in Liquid Metals. NASA TN D-3426, 1966.

21. Smith, Jack L. : Use of Phase-Locked-Loop Control for Driving Ultrasonic Transducers. NASA TN D-3567, 1966.

22. Neppiras, E. A. : Techniques and Equipment for Fatigue Testing at Very High Frequencies. Proc. ASTM, vol. 59, 1959, pp. 691-710.

23. Thiruvengadam, A. : High Frequency Fatigue of Metals and their Cavitation Damage Resistance. Rep. TR-233-6, Hydronautics, Inc. , Dec. 1964. (Available from DDC as AD-456365.)

24. Zemskov, G. V.; Dombrovksaya, E. V.; Yarkina, V. T . ; Gushchin, L. K.; and Parfenov, A. K. : Nitriding of Steel Intensified by Ultrasound. Henry Brutcher Translation no. 6183, 1964.

I

.. " .

ERRATA

NASA Technical Note D-5131

EFFECT OF ULTRASONIC VIBRATION ON PRECIPITATION



March 1969

The following references should be added at the end of the report:

~ILPIt. 6t:!

~)r/tLiPi~ :5tV

15. Decker, R. F.; Eash, J. T.; and Goldman, A. J.: 18% Nickel Maraging Steel.

Trans. ASM, vol. 55, no. 1, Mar. 1962, pp. 58-76.

16. Contractor, G. P.: The Marvel of Maraging. J. Metals, vol. 18, no. 8, Aug. 1966, pp. 938-946.

17. Anon.: Precipitation Hardenable Stainless Steels. Bull. 1223R4 75 C 1262, Republic

Steel Corp., 1962.

18. Anon.: Haynes Alloy No. R-41. Haynes Stellite Bull. No. F-30, 155 B, Union Carbide Stellite Co., Apr. 1963.

19. Sandrock, Gary D.; and Leonard, L.: Cold Reduction as a Means of Reducing Em

brittlement of a Cobalt-Base Alloy (L-605). NASA TN D-3528, 1966.

20. Young, Stanley G.; and Johnston, James R.: Accelerated Cavitation Damage of

Steels and Superalloys in Liquid Metals. NASA TN D-3426, 1966.

21. Smith, Jack L.: Use of Phase-Locked-Loop Control for Driving Ultrasonic Transducers. NASA TN D-3567, 1966.

22. Neppiras, E. A.: Techniques and Equipment for Fatigue Testing at Very High

Frequencies. Proc. ASTM, vol. 59, 1959, pp. 691-710.

23. Thiruvengadam, A.: High Frequency Fatigue Of. Metals and their Cavitation Damage

Resistance. Rep. TR-233-6, Hydronautics, Inc., Dec. 1964. (Available from

DDC as AD-456365.)

24. Zemskov, G. V.; Dombrovksaya, E. V.; Yarkina, V. T.; Gushchin, L. K.; and

Parfenov, A. K.: Nitriding of Steel Intensified by Ultrasound. Henry Brutcher

Translation no. 6183, 1964.

25. Anon. : Vasxomax 300 CVM. Data Sheet 2000-1-62 FL, Vanadium-Alloy Steels C o . , 1962.

26. Anon. : Haynes Alloy No. 25. Haynes Stellite Bull. F30-041D, Union Carbide Stellite Co. , Feb. 1967.

Issued Date - 6-26-69 NASA-Langley. 1969

~ . - _..- ..... .. .._......

· .

25. Anon.: Vasxomax 300 CVM. Data Sheet 2000-1-62 FL, Vanadium-Alloy Steels Co. ,

1962.

26. Anon.: Haynes Alloy No. 25. Haynes Stellite Bull. F30-041D, Union Carbide Stel

lite Co., Feb. 1967.

Issued Date - 6-26-69 NASA-Langley. 1969

TECH LIBRARY KAFB. NM

I1111111111111111111111111111111lllllill1111 013L89L

NASA TN D-5131



By Stanley G. Young and L. Leonard

Lewis Research Center Cleveland, Ohio

NATIONAL AERONAUTICS AND SPACE ADMlN ISTRATION

For sale by the Clearinghouse for Federal Scient i f ic and Technical Information Springfield, V i rg in ia 22151 - CFSTl pr ice $3.00

TECH LlI;IRARY KAFB, NM

111111111111111111111111111111111111111111111 0131891

NASA TN D-5131

EFFECT OF ULTRASON1C VIBRATION ON PRECIPITATION

HARDEN1NG OF STEELS AND SUPERALLOYS

By Stanley G. Young and L. Leonard

Lewis Research Center Cleveland, Ohio

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

For sale by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151 - CFSTI price $3.00

ABSTRACT

Specimens of a 300 g r a d e maraging s tee l , 17-4 PH s t ee l , A-286, Re& 41, and L-605 w e r e subjected to ultrasonic vibration during aging. Ultrasonic vibration i n -creased the hardening r a t e but did not increase the maximum hardness above that of statically aged specimens. The heat treating environment (which included sodium, chloride sa l t s , and air) w a s found to influence the observed hardening r a t e s of vibrated aged specimens.

ii

ABSTRACT

Specimens of a 300 grade maraging steel, 17-4 PH steel, A-286, Rene 41, and

L-605 were subjected to ultrasonic vibration during aging. Ultrasonic vibration in

creased the hardening rate but did not increase the maximum hardness above that of

statically aged specimens. The heat treating environment (which included sodium,

chloride salts, and air) was found to influence the observed hardening rates of vibrated

aged specimens.

ii



by Stanley G. Young and L. Leonard*


SUMMARY

Effects of ultrasonic vibration on the precipitation hardening of a 300 grade maraging steel, 17-4 PH steel , A-286, Ren6 41, and L-605, were studied. A magnetostrictive vibrator was coupled directly to specimens of these alloys and they were vibrated at their natural resonant frequency while undergoing standard aging heat treatments.

Specimen peak-to-peak vibration displacements ranged from 0 . 8 to 6 . 4 mils (2. OX10-2 to 16. 3X10-2 mm) at a frequency of 25 000 hertz. Material properties were compared with those of nonvibrated specimens given s imilar aging treatments.

Application of ultrasonic vibration resulted in some increase in the hardening rate for most of the alloys tested; however, the maximum hardness obtained by ultrasonic vibration did not exceed that obtainable by statically aging any of the alloys. The tensile and yield strengths of vibrated specimens of the 300 grade maraging s teel increased by approximately 1 and 2 percent above their values in the static aged condition at the recommended aging temperatures and t imes. S t ress level did not consistently o r appreciably affect the aging results.

Metallographic examination of precipitates in vibrated L -605 specimens showed no differences from the precipitate distribution in statically aged specimens.

The observed increase in hardening ra te due to vibration was l e s s than that reported by previous investigators. It is believed that the heat-treating environments used in the ear l ie r investigations permitted the vibrated specimens to reach temperatures in excess of the desired heat-treating temperature and that is the most likely cause of the increased hardening ra tes reported previously.

* Assistant Professor, Department of Metallurgy, Case Western Reserve University, Cleveland, Ohio.

II~

If I


HARDENING OF STEELS AND SU PERALLOYS

by Stanley G. Young and L. Leonard*


SUMMARY

Effects of ultrasonic vibration on the precipitation hardening of a 300 grade maraging

steel, 17 -4 PH steel, A -286, Rene 41, and L-605, were studied. A magnetostrictive

vibrator was coupled directly to specimens of these alloys and they were vibrated at their

natural resonant frequency while undergoing standard aging heat treatments.

Specimen peak-to-peak vibration displacements ranged from 0.8 to 6.4 mils

(2.0><10-2 to 16. 3XlO-2 mm) at a frequency of 25 000 hertz. Material properties were

compared with those of nonvibrated specimens given similar aging treatments.

Application of ultrasonic vibration resulted in some increase in the hardening rate

for most of the alloys tested; however, the maximum hardness obtained by ultrasonic

vibration did not exceed that obtainable by statically aging any of the alloys. The tensile

and yield strengths of vibrated specimens of the 300 grade maraging steel increased by

approximately 1 and 2 percent above their values in the static aged condition at the recom

mended aging temperatures and times. Stress level did not consistently or appreciably

affect the aging results.

Metallographic examination of precipitates in vibrated L-605 specimens showed no

differences from the precipitate distribution in statically aged specimens.

The observed increase in hardening rate due to vibration was less than that reported

by previous investigators. It is believed that the heat-treating environments used in the

earlier investigations permitted the vibrated specimens to reach temperatures in excess

of the desired heat-treating temperature and that is the most likely cause of the increased

hardening rates reported previously.

* Assistant Professor, Department of Metallurgy, Case Western Reserve University,

Cleveland, Ohio.

INTROD UCTION

In alloy systems in which the solid solubility decreases with decreasing temperature, the precipitation of a second phase f rom a solid solution can be accompanied by a marked change in mechanical properties. In some alloys the hardness and strength decrease during precipitation but i n certain (age hardening) alloys there is a substantial increase in hardness and strength. The subject is extensively covered in references 1to 4.

Because precipitation is dependent to a large extent on diffusion, temperature is very important in determining the rate and amount of precipitation hardening. If the temperature is very high, precipitate growth is rapid and alloys overage quickly. If the temperature is low, diffusion is slow and longer aging t imes are required. Most alloy systems, however, have shown higher peaks in mechanical properties when aged at low temperatures for very long t imes (ref. 3). Alloy heat treatments usually are compromises between aging time and temperature to achieve a high hardness in a reasonably short time. Any process that can shorten the t ime of aging and yet provide optimum mechanical properties would obviously be of great value. The application of ultrasonic vibration to alloys during the aging treatment has been found by some (refs. 5 to 9) to be such a process; however, widely differing resul ts have been reported. Some investigators found that the application of ultrasonic energy to aluminum base alloys increased the rate of hardening by a factor of 1 2 to 80 t imes that observed in a n ordinary static aging procedure (refs. 5 and 6). Others have shown a 20 fold increase in the rate of hardening of a nickel base alloy (ref. 7). Still others found only slight increases in the ra te of hardening fo r aluminum alloys (ref. 8) and a beryllium-bronze alloy (ref. 9). Also, different maximum hardness values have been reported fo r vibrated specimens as compared to statically aged specimens. Thus, higher, s imilar , and even lower hardness peaks have been r e ported fo r vibrated specimens than for statically aged specimens (refs. 5, 8, 10, and 11). It should be noted, however, that the alloys and types of equipment used varied among these investigations and this could account fo r the large differences in the reported effects of ultrasonic vibration. In general, most previous investigators found that ultrasonic vibration applied during the aging of mater ia ls increased the aging ra te and improved the mechanical properties of alloys. These improvements can be attributed to lattice stretching and increased diffusion (refs. 5 and 11 to 14).

The purposes of this investigation were: (1)to apply ultrasonic vibration during the aging of certain s tee ls and superalloys, in order to determine if their hardening and strengthening responses were influenced by vibration, and (2)to attempt to explain the wide differences in resul ts reported by various investigators. A magnetostrictive apparatus was used to vibrate specimens at a frequency of 25 000 her tz while they were being subjected to age hardening heat treatments. The mater ia ls studied were a 300 grade maraging steel, 17-4 P H steel, A-286, Ren6 41, and L-605. Heat treating temperatures

2

INTRODUCTION

In alloy systems in which the solid solubility decreases with decreasing temperature,

the precipitation of a second phase from a solid solution can be accompanied by a marked

change in mechanical properties. In some alloys the hardness and strength decrease

during precipitation but in certain (age hardening) alloys there is a substantial increase

in hardness and strength. The subject is extensively covered in references 1 to 4.

Because precipitation is dependent to a large extent on diffusion, temperature is very

important in determining the rate and amount of precipitation hardening. If the tempera

ture is very high, precipitate growth is rapid and alloys overage quickly. If the tempera

ture is low, diffusion is slow and longer aging times are required. Most alloy systems,

however, have shown higher peaks in mechanical properties when aged at low tempera

tures for very long times (ref. 3). Alloy heat treatments usually are compromises be

tween aging time and temperature to achieve a high hardness in a reasonably short time.

Any process that can shorten the time of aging and yet provide optimum mechanical prop

erties would obviously be of great value. The application of ultrasonic vibration to alloys

during the aging treatment has been found by some (refs. 5 to 9) to be such a process;

however, widely differing results have been reported. Some investigators found that the

application of ultrasonic energy to aluminum base alloys increased the rate of hardening

by a factor of 12 to 80 times that observed in an ordinary static aging procedure (refs. 5

and 6). Others have shown a 20 fold increase in the rate of hardening of a nickel base

alloy (ref. 7). Still others found only slight increases in the rate of hardening for alumi

num alloys (ref. 8) and a beryllium-bronze alloy (ref. 9). Also, different maximum

hardness values have been reported for vibrated specimens as compared to statically

aged specimens. Thus, higher, Similar, and even lower hardness peaks have been re

ported for vibrated specimens than for stati~ally aged specimens (refs. 5, 8, 10, and 11).

It should be noted, however, that the alloys and types of equipment used varied among

these investigations and this could account for the large differences in the reported effects

of ultrasonic vibration. In general, most previous investigators found that ultrasonic

vibration applied during the aging of materials increased the aging rate and improved the

mechanical properties of alloys. These improvements can be attributed to lattice

stretching and increased diffusion (refs. 5 and 11 to 14).

The purposes of this investigation were: (1) to apply ultrasonic vibration during the

aging of certain steels and superalloys, in order to determine if their hardening and

strengthening responses were influenced by vibration, and (2) to attempt to explain the

wide differences in results reported by various investigators. A magnetostrictive appa

ratus was used to vibrate specimens at a frequency of 25 000 hertz while they were being

subjected to age hardening heat treatments. The materials studied were a 300 grade

maraging steel, 17-4 PH steel, A-286, Rene 41, and L-605. Heat treating temperatures

2

were in the range of the manufacturer's recommended optimum aging temperatures for each material. The effects of vibration on hardness, tensile properties, and distribution of precipitates within the structure, were determined for specific alloys. The effect of heat treating environments was a l so considered. In all cases, resul ts obtained from statically aged control specimens were compared with resul ts obtained with vibrated specimens.

MATER IA LS, A PPARAT US , AND PROCEDURE

Materia Is

Specimens. - The mater ia ls investigated were the iron-base alloys, 300 grade maraging steel, 17-4 PH steel, and A-286; the nickel-base alloy Re& 41; and the cobalt-base alloy L-605. The nominal chemical composition of each alloy is listed in table I. The recommended heat treatments and nominal mechanical properties of these alloys a r e listed in table II.

The 300 grade maraging s teel has demonstrated a very wide range in degree of age hardening (refs. 15 and 16). The hardness of this alloy can increase on aging from approximately Rockwell C 30 to 50 or higher. 17-4 PH steel is a martensitic precipitation hardening steel and A-286 a highly alloyed precipitation hardenable iron-base material with an austenitic s t ructure (ref. 17). Ren6 41 is a precipitation hardening nickel-base alloy that has high strength at temperatures in the range of 1200' to 1800' F (922 to 1255 K) (ref. 18). L-605 is a cobalt-base alloy and was included because the precipitate in this alloy can normally be seen by optical microscopy after relatively short aging t imes (ref. 19) and was, therefore, considered to be particularly useful for metallographic study.

Heat treating environments. - Three different environments were used f o r heat-treatment of the alloy specimens both statically and while they were subjected to ul t rasonic vibration: a sodium bath, a commercial chloride salt bath, and air.

The sodium bath was used to heat t rea t the 300 grade maraging and 17-4 PH steels in the temperature range of 800' to 1000° F (700 to 811 K). Sodium was selected as a heat-treating solution because a facility f o r handling liquid alkali metals was available and because of its desirable properties compared to other media. Lead, which has been used as a heat-treating medium by other investigators, has a high density which would significantly dampen the vibration of the ultrasonically treated specimens. Sodium with a density of only 0.97 gram per cubic centimeter was much more advantageous in this respect. The high heat conductivity of sodium also helped to reduce local temperature gradients that resulted from specimen vibration.

3

-_._--_ .... _._-,--------_._---

were in the range of the manufacturer's recommended optimum aging temperatures for each material. The effects of vibration on hardness, tensile properties, and distribution

of precipitates within the structure, were determined for specific alloys. The effect of

heat treating environments was also considered. In all cases, results obtained from statically aged control specimens were compared with results obtained with vibrated specimens.

MATERIALS, APPARATUS, AND PROCEDURE

Materials

Specimens. - The materials investigated were the iron-base alloys, 300 grade

mara,ging steel, 17-4 PH steel, andA-286; the nickel-base alloy Rene 41; and the cobalt

base alloy L-605. The nominal chemical composition of each alloy is listed in table I. The recommended heat treatments and nominal mechanical properties of these alloys are listed in table II.

The 300 grade maraging steel has demonstrated a very wide range in degree of age hardening (refs. 15 and 16). The hardness of this alloy can increase on aging from approximately Rockwell C 30 to 50 or higher. 17-4 PH steel is a martensitic precipitation hardening steel and A-286 a highly alloyed precipitation hardenable iron-base material with an austenitic structure (ref. 17). Rene 41 is a precipitation hardening nickel

base alloy that has high strength at temperatures in the range of 12000 to 18000 F (922 to 1255 K) (ref. 18). L-605 is a cobalt-base alloy and was included because the precipitate in this alloy can normally be seen by optical microscopy after relatively

short aging times (ref. 19) and was, therefore, considered to be particularly useful for metallographic study.

Heat treating. environments. - Three different environments were used for heat treatment of the alloy specimens both statically and while they were subjected to ultra

sonic vibration: a sodium bath, a commercial chloride salt bath, and air. The sodium bath was used to heat treat the 300 grade maraging and 17 -4 PH steels

in the temperature range of 8000 to 10000 F (700 to 811 K). Sodium was selected as a heat-treating solution because a facility for handling liquid alkali metals was available and because of its desirable properties compared to other media. Lead, which has been

used as a heat-treating medium by other investigators, has a high denSity which would Significantly dampen the vibration of the ultrasonically treated specimens. Sodium with

a density of only 0.97 gram per cubic centimeter was much more advantageous in this

respect. The high heat conductivity of sodium also helped to reduce local temperature gradients that resulted from specimen vibration.

3

----

---- --

---- --

--

TABLE I. - NOMINAL COMPOSITIONS OF ALLOYS TESTED, WEIGHT PERCENT

Material Cobalt 'itanium Alumi- Boron Carbon Silicon Manganum nese

300 Grade Balance 18. 5 4.8 1 0.60 1 0.10 10.003 I 03 1 10 1 10 maraging steel' 1 . 0 5 Ca

17-4 PH steel' Balance. 4 16.5 I 1 I

i I

.3 Cb + Tai

A -286' Balance! 25.5 I 15.0 j 1.25 2.15 b.35 .006 b.08 . 7 1.5 b.03 b.04 . 3 Va Re& 41d b5 !Balance' 11 L-605 (HS-25)e b3 1 10 I Balance 20

3.15 1 . 5 .007 '. 12 b . 5 b.10

aRef. 25. bMaximum. 'Ref. 17. dRef. 18. eRef. 26.

I I

I i i

TABLE I. - NOMINAL COMPOSITIONS OF ALLOYS TESTED, WEIGHT PERCENT

Material Iron Nickel C0balt

300 Grade Balance 18.5 9.0

maraging steela '! ,

17 -4 PH steelc : Balance , 4 ----

I , I )

A-286c I Balance i 25.5 1----

Chro- Molyb- Tung- Titanium Alumi- Boron Carbon Silicon Manga- Sulfur Phospho- Other

mium denum sten num nese rus

---- 4.8 0.60 O. 10 0.003 bO. 03 bOo 10 bOo 10 bO. 010 bO. 010 0.2 Zr

!

116.5

15.0

19

I -- \ ---- i ----

i ' I I ' I ' : 1. 25 : -- I :.!: b. 35

: ---- I I

1 ____ - ,.

, 006 b. 08 . 7 1. 5 b, 03 .007 b. 12 b. 5 b. 10 b 015

.05 Ca b4 Cu

b. 04 N

.3Cb+Ta ,3 Va

Rene 41d I b 5 i Balance \' 11 L-605 (HS-25)e I b3 I 10 ,Balance 20 I :~~~ ~I ~.-=- I-----.~I __ ._10_~~, _1_._5 __ II~b_:0_3_0_i~ __ b_.0_3_0 ___ --_-_-_--_-_-_--_

aRef. 25. bM . runmum. cRef. 17.

dRef. 18.

eRef. 26.

--

--

--

TABLE II. - RECOMMENDED HEAT TREATMENTS AND NOMINAL MECHANICAL

PROPERTIES OF ALLOYS AT ROOM TEMPERATURE

IMaterial Heat treatment Aging Nominal mechanical properties as received

Temperature, Time, Condition Hardness Yield strength Tensile strength Elonga- Reduc-O F (K) h r (0.2 percent) tion, tion

percent in area,psi N/m2 psi N/m2 percent

300 Grade Solution annealed at 875 to 925 3 to 6 Annealed RC-31 110 000 7. 6x1O8 150 000 1 . 0 3 ~ 1 0 ~18 maraging 1475' to 1525' F (741 to 769)) (as received) steel' (1074 to 1102 K) for air cool

1hour, air cool Aged RC-54.3 283 000 1.95X10 I 55

17-4 PH Solution annealed a t 900 (755)) 1 Annealed BHN 332 110 000 7. 6X108 150 000 1.03X10 45 steel 1900' F (1311 K), air cool (as received) (RC-36) ~

air cool Aged RC-44 170 000 1.17X10g i 190 000

~

1.3lX1011 1: 40

A -286b Solution annealed at 1300 (977), 16 Annealed RB-75 36 000 2. 48X108 93 000 6. 41X108 70 1800' F (1255 K) for air cool (as received) 1 hour, water/oil quench I Aged RC-29 1 100

~

000 1 6. 9X108 1 145 000 1 l.OXl0 g i :: 37 ~~ ~~

/Re& 41' Solution annealed a t 1400 (1033), 16 Annealed dRC-21 90 000 6.&108 _ _ _ _ _ _ _ -_______1950' F (1339 K) for air cool (as received) 4 hours, air cool

Aged dRC-40 154 000 1.06X109 206 000 1.4at109 14cSolution annealed a t (f) (f) Annealed RC-24 70 000 4.8%108 150 000 1 . 0 3 ~ 1 0 ~65.0L-605

(HS-25)e 2250' to 2265' F (as received) (1505 to 1513 K), water quench

%ef. 25. bRef. 17. %ef. 18. k e a s u r e d on round specimen. eRef. 26. fGenerally used in the annealed condition.

TABLE II. - RECOMMENDED HEAT TREATMENTS AND NOMINAL MECHANICAL

PROPERTIES OF ALLOYS AT ROOM TEMPERATURE

Material Heat treatment

as received

300 Grade Solution annealed at

maraging

steela

17-4 PH

steelb

A-286b

Rene 41c

L-605 (HS-25)e

~ef. 25. bRef. 17.

~ef. 18.

14750 to 15250 F

(1074 to 1102 K) for

1 hour, air cool

Solution annealed at

19000 F (1311 K),

air cool


18000 F (1255 K) for

11 hour, water/oil quench


19500 F (1339 K) for

4 hours, air cool


2250° to 2265° F

(1505 to 1513 K),

water quench

~easured on round specimen.

eRef. 26.

Aging

Temperature, of (K)

875 to 925

(741 to 769),

air cool

900 (755),

air cool

1300 (977),

air cool

1400 (1033),

air cool

(f)

fGenerally used in the annealed condition.

-----"1 Time,

hr

3 to 6

1

16

~

16

(f)

Nominal mechanical properties

Condition Hardness Yield strength Tensile strength (0.2 percent)

psi N/m2 psi N/m2

Annealed RC-31 110000 7.6X108 150000 1. 03X109

(as received)

Aged RC-54.3 283 000 1. 95X109 294 000 2.03Xl09

Annealed BHN 332 110000 7.6XI08 150000 1. 03X109

(as received) (RC-36)

Aged RC-44 170000 1. 17XI09 190000 1. 3lXl09

Annealed RB-75 36000 2.48x108 93000 6. 41X108

(as received)

Aged RC-29 100000 6.9X108 145000 1. OX109

Annealed dRC - 21 90000 6.2><108 ------ --------(as received)

Aged dRC -40 154 000 1. 06X109 206000 1. 42><109

Annealed RC-24 70000 4.82><108 150000 1. 03X109

(as received)

Elonga- Reduc-tion, tion

percent in area,

percent

18 72

12 55

10 45

10 40

48 70

24 37

-- --

14 --65.0 --

A commercial chloride salt bath was used to heat treat A-286, Ren6 41, and L-605 in the temperature range from 1300' to 1600' F (978to 1144 K). The melting point of the salt bath was approximately l l O O o F (856K). The chloride salt bath was chosen f o r the high temperature aging studies because it is relatively inert , nontoxic and has a wide temperature range between melting and boiling.

Finally, air was used as the heat-treating medium fo r the 300 grade maraging s teel at 800' F (700 K). The air test was conducted to determine the differences in aging r e sponse that could result f rom applying ultrasonic vibration to a specimen in an environment with relatively low heat t ransfer properties. A gas environment has previously been used by other investigators (refs. 6 and 7).

A ppar at us

A photograph of the facility used is shown in figure 1. This facility was originally constructed to investigate cavitation damage of mater ia ls in liquid metal environments (ref. 20). The photograph shows the vacuum dry box and associated electronics and control equipment.

A schematic diagram of the magnetostrictive vibration apparatus and heat treating test chamber is shown in figure 2. The dry box and test chamber were designed to be evacuated to a pressure of approximately torr (0.13 N/m 2). When sodium was used as the heat treating medium, the dry box was filled with high purity argon to prevent oxidation of the sodium. When chloride salt was used as the heat-treating solution, air was used as the cover gas. Glove ports were provided on the dry box to enable the operator to work within the argon atmosphere.

A schematic diagram of the transducer assembly is shown in figure 3. The specimen was attached to the end of the resonant system consisting of the transducer and amplifying horn. The transducer was a commercial unit modified for use within the vacuum dry box. The horn served as a displacement amplifier and provided a convenient attachment for a nodal flange vapor seal. All of the components of this system were designed so that at the test frequency the length of each par t was a multiple of one-half the wavelength. This design makes it possible for the entire system to vibrate as a standing wave of the resonant frequency.

The displacement and frequency of vibration were detected by a magnetic pickup indicated in figure 2. A sine wave signal was sent f rom the pickup to an oscilloscope and to an automatic feedback system that maintained a constant displacement irrespective of variations in the resonant frequency induced by temperature changes. The electronic drive feedback system is described in reference 21. A schematic diagram of the control system is shown in figure 4.

6

A commercial chloride salt bath was used to heat treat A-286, Rene 41, and L-605

in the temperature range from 13000 to 16000 F (978 to 1144 K). The melting point of the salt bath was approximately 11000 F (856 K). The chloride salt bath was chosen for

the high temperature aging studies because it is relatively inert, nontoxic and has a wide

temperature range between melting and bOiling. Finally, air was used as the heat-treating medium for the 300 grade maraging steel

at 8000 F (700 K). The air test was conducted to determine the differences in aging response that could result from applying ultrasonic vibration to a specimen in an environ

ment with relatively low heat transfer properties. A gas environment has previously been

used by other investigators (refs. 6 and 7).

Apparatus

A photograph of the facility used is shown in figure 1. This facility was originally

constructed to investigate cavitation damage of materials in liquid metal environments (ref. 20). The photograph shows the vacuum dry box and associated electronics and con

trol equipment. A schematic diagram of the magnetostrictive vibration apparatus and heat treating

test chamber is shown in figure 2. The dry box and test chamber were designed to be evacuated to a pressure of approximately 10-3 torr (0.13 N/m2). When sodium was used

as the heat treating medium, the dry box was filled with high purity argon to prevent oxidation of the sodium. When chloride salt was used as the heat-treating solution, air was

used as the cover gas. Glove ports were provided on the dry box to enable the operator

to work within the argon atmosphere.

A schematic diagram of the transducer assembly is shown in figure 3. The specimen

was attached to the end of the resonant system consisting of the transducer and ampli

fying horn. The transducer was a commercial unit modified for use within the vacuum

dry box. The horn served as a displacement amplifier and provided a convenient attach

ment for a nodal flange vapor seal. All of the components of this system were designed

so that at the test frequency the length of each part was a multiple of one-half the wavelength. This design makes it possible for the entire system to vibrate as a standing wave

of the resonant frequency. The displacement and frequency of vibration were detected by a magnetic pickup in

dicated in figure 2. A sine wave signal was sent from the pickup to an oscilloscope and to an automatic feedback system that maintained a constant displacement irrespective of

variations in the resonant frequency induced by temperature changes. The electronic

drive feedback system is described in reference 21. A schematic diagram of the control

system is shown in figure 4.

6

I i I

Figure 1. - Ultrasonic vibration heat treating facility.

n-~ Lift mechanism

Coolant outlet --l __ II ...... L- Coolant inlet

Vacuum dry box, /

I

Air jacket --~,

Amplifying hor~~" ,~Magnetostrictive LVacuum line

,/ transducer

\ , assembly

Nodal flange --, \ , \

Seal ing sleeve--'\ \ , , \

" ' Thermocouple__ ,,\~~.C::::iJ ", " ,

Ai r lock

CD-I0246-32

Figure 2. - Schematic diagram of magnetostrictive vibration apparatus and heat treating test chamber.

7

I i I

Figure 1. - Ultrasonic vibration heat treating facility.

n-~ Lift mechanism

Coolant outlet --l __ II ...... L- Coolant inlet

Vacuum dry box, /

I

Air jacket --~,

Amplifying hor~~" ,~Magnetostrictive LVacuum line

,/ transducer

\ , assembly

Nodal flange --, \ , \

Seal ing sleeve--'\ \ , , \

" ' Thermocouple__ ,,\~~.C::::iJ ", " ,

Ai r lock

CD-I0246-32

Figure 2. - Schematic diagram of magnetostrictive vibration apparatus and heat treating test chamber.

7

Displacement of

v ibrat ion

t CD-10247-32

Figure 3. - Schematic diagram of t ransducer assembly.

I Proport ional

Phase Automatic -demodulatoi Ultrasonic

and low-pass

Integrator osci l lator

f i l te r

t f reque ncyJPhase-locked loop

Mechanical posit ion

Displacement moni tor (oscilloscope)

F igure 4. - Block diagram of proport ional and phase-locked-loop contro l systems.

8

I ~-

8

t- -----t Magnetostrictive transducer

-Node X 2

t---X 2

1 Displacement

of f-vibration ____ + Amplifying horn - Node --

1- Seal ing sl eeve

-Node------pecimen

I- X

-Node--------

CD-I0247-32

Figu re 3. - Schematic diagram of transducer assembly.

Proportional

Phase ~ §tr ""A""lte-r-n---'at"'in-g-~A~tomaticl-- demodulator I Direct current Voltage Power Ultrasonic current signals gam and I--i voltage r-- controlled -,- ampli- , driver r--

control I-- low-pass I L oscillator' fier / filter Integrator I / I L-__ ------'

I f L Driving / frequencyJ

Phase-locked loop

I Magnetic I Mechanical position '----------.-I~~~~______ll pickup II---~~---'--'-'-=-'-'-=='---"--=---'~"------~~~----'

<!>Displacement monitor oscilloscope)

Figure 4. - Block diagram of proportional and phase-locked-loop control systems.

_J

The sine wave signal viewed on the oscilloscope was calibrated against optical measurements of the specimen displacement. A 200-power microscope with a split-image measuring eyepiece w a s used. The accuracy of measurement with this eyepiece was *to. 00002 inch (5. l X 1 0 - 4 mm).

Figure 5 is a schematic drawing of the relative positions of the heater, test chamber, heat-treating liquid, specimen, and thermocouples. Temperature profiles were taken both in the liquid baths and on the surface of statically aged specimens at all aging temperatures. These will be discussed in the section dealing with test conditions. The experimental setup for static aging in air is shown in figure 6. This photograph shows the 3 -zone resistance -heater furnace and a thermocoupled specimen used to measure the temperature gradients.

Thermocoupled specimens could not be used during any of the vibration tests because the thermocouples did not remain intact or in place while the specimen was vibrated. Under these circumstances only the furnace environment temperature was measured. An optical pyrometer was used to determine the temperature r i se in a specimen due to vibration when it was vibrated in air without the surrounding furnace.

Thermocouples (XI s)

cia 38 in. or +O. 97 cm)

L 5 in. (3.8 cm)

Spec imen- - - - -

Heat t rea t ing test chamber--.- Furnace windings

1.5 in. Air cooling jacket (3.8 cm)ti

Figure 5. - Schematic diagram showing relat ive positions of test components. specimen, and thermocouples.

9

The sine wave signal viewed on the oscilloscope was calibrated against optical

measurements of the specimen displacement. A 200-power microscope with a split

image measuring eyepiece was used. The accuracy of measurement with this eyepiece was ±O. 00002 inch (5. lXlO-4 mm).

Figure 5 is a schematic drawing of the relative positions of the heater, test chamber, heat-treating liquid, specimen, and thermocouples. Temperature profiles were taken both in the liquid baths and on the surface of statically aged specimens at all aging tem

peratures. These will be discussed in the section dealing with test conditions. The ex

perimental setup for static aging in air is shown in figure 6. This photograph shows the 3 -zone resistance -heater furnace and a thermocoupled specimen used to measure the

temperature gradients. Thermocoupled specimens could not be used during any of the vibration tests because

the thermocouples did not remain intact or in place while the specimen was vibrated.

Under these circumstances only the furnace environment temperature was measured. An optical pyrometer was used to determine the temperature rise in a specimen due to vi

bration when it was vibrated in air without the surrounding furnace.

l ~ I t~ ,""m=o,l" ~ ,1

Fluid level-- __ _ (±o. 38 in. or ±O. 97 cml

Heat treating _ -r ~~~~ ; .. :, ~ ~ , ,,,' 'h.mb" ~---- ~_- n~ _t>-FU rnace windings

- ,,: "., - 1 5 in Air cooling jacket ~ --,,'~-=':i- 6. 8 c~l

:~~~~-~~~~~"?~.~-:~-~-

CD-I0248-32

Figure 5. - Schematic diagram showing relative positions of test components, specimen, and thermocouples.

9

C-66-3750

Figure 6. - Relative vertical positions three-zone heat treating furnace and thermocoupled straight bar specimen used for air environment aging tests.

Specimen DeSign

Two types of specimens shown in figure 7 were used - a straight bar and a tapered

specimen. The bulk of tests were conducted with the straight bar specimen shown in

figure 7(a). This specimen was designed so that at 25 000 hertz a standing ultrasonic

wave was maintained during the test. The length of each straight bar specimen was de

termined by the wave length of the 25 000 hertz wave in each specific material. A sample

calculation of the wavelength of the 25 000 hertz wave in 300 grade maraging steel is

given in appendix A.

An idealized example of the displacement, stress, and strain relations for a straight

bar specimen is shown in figure 8. In the portions of the standing longitudinal wave

where the vibration is maximum, the strain and corresponding stress are minimum.

Wher'e the displacement is minimum (at the nodes) the stress and strain are maximum.

The equations for stress and strain based on displacement and distance from the node are

given in appendix B. A sample calculation of stress and strain for a straignt bar 300

10

C-66-3750

Figure 6. - Relative vertical positions three-zone heat treating furnace and thermocoupled straight bar specimen used for air environment aging tests.

Specimen DeSign

Two types of specimens shown in figure 7 were used - a straight bar and a tapered

specimen. The bulk of tests were conducted with the straight bar specimen shown in

figure 7(a). This specimen was designed so that at 25 000 hertz a standing ultrasonic

wave was maintained during the test. The length of each straight bar specimen was de

termined by the wave length of the 25 000 hertz wave in each specific material. A sample

calculation of the wavelength of the 25 000 hertz wave in 300 grade maraging steel is

given in appendix A.

An idealized example of the displacement, stress, and strain relations for a straight

bar specimen is shown in figure 8. In the portions of the standing longitudinal wave

where the vibration is maximum, the strain and corresponding stress are minimum.

Wher'e the displacement is minimum (at the nodes) the stress and strain are maximum.

The equations for stress and strain based on displacement and distance from the node are

given in appendix B. A sample calculation of stress and strain for a straignt bar 300

10

- -

.._.

0.44 in. 5/16 in. x 24 NF (1.12 cm)- 3 thread 7,

-\

t - A ,?7I1

0.5 in. /(1.27 cmIJ

(a) S t ra igh t ba r specimen.

Diameter. 5/16 in. x 24 NF

Constant diameter 0.44 in. thread -\ \

A, (1.12 cm)---- ‘\ -II

0. 19 in. ,f (0.483 c m ) l

~ -A - ,0. 5 in. (1.27 CD-10250-32

(b) Tapered specimen for h i g h displacement

Figure 7. - Specimen designs used for u l t rason ic v ibrat ion aging studies.

Node Node A A

I

Figure 8. - Specimen displacement, stress, and s t ra in profiles.

11

I

I I: ,-

I I~

0.44 in. n. 12 cm)-1

Constant diameter

0.19 in. ,t (0.483 cm).../

5/16 in. x 24 NF thread ---...,

--11----~ 0.5 in. " n.27 cm)--'

la) Straight bar specimen.

D• t 5/16 in. x 24 NF lame er, th d

O 44 'n rea -, . I. \

II. 12 cm)---_ \ "-------

---11 0.5 in. n.27 cm) I , I

0.5 in. : n.27 cm)--1

CD-J0250-32

Ib) Tapered specimen for high displacement

Figure 7. - Specimen designs used for ultrasonic vibration aging studies.

Node Node

t , -"-1II4 ~I- ---1II4 ~I .. --1II4 ~I~ 1II4 ~ -"" 11

Figure 8. - Specimen displacement, stress, and strain profiles.

11

TABLE IlI. - TEST CONDITIONS

Material remperatur lisplacemen Stress ( m a ) Test t imes, min0F K mil mm psi N/m2

100 Grade maraging stee: 80C 700 0 0 C 0 15, 60, 180, 360 2.0 .051 22 500 1. 55x10' 15, 60, 180, 360 3.0 .076 33 80C 2. 33x10' 15, 30 - ~

9oc 755 0 0 0 0 5, 60, 240, 360 2.0 .051 22 500 1. 55x10' 5, 60, 240, 360 0 0 0 0 16 6.4 .163 72 100 4.97X10' 16

1000 811 0 0 0 0 5, 30, 120, 240, 360 2.0 .051 22 500 1.55X108 5, 30, 120, 240, 360

17-4 PH steel 900 755 0 0 0 0 5 , 15, 30, 60, 120, 360 2.0 .051 22 950 1. 58X108 5 , 15, 30, 60, 120, 360 0 0 0 0 1

5.0 .127 57 400 3. 96x1O8 I

A-286 1300 978 0 0 0 D 5 , 30, 120 .8 .020 9 280 6. 40x107 i, 30, 120

1. 5 .038 17 400 1.2ox108 $0

2.0 .051 23 200 1. 6OX1O8 )

R e d 41 1400 1033 0 0 0 3 i, 18, 120, 240 1. 0 .025 12 250 3 . 4 5 ~ 1 0 ~i, 18, 120, 240 2.0 .051 24 500 1. 69X108 i, 18

L-605 (HS-25) 1600 1144 0 D 0 1 io0

. 8 .020 10 450 7 . 2 0 ~ 1 0 ~io0

1.4 .036 18 300 1. 26X108 .O (vibration), 600 (static)

grade maraging steel specimen with a 2-mil (5. 1X10-2 mm) peak-to-peak displacement is also included. All values of maximum cyclic stress for all the materials tested were calculated and a r e given in table III.

The second type of specimen used is shown in figure 7(b). In the tapered specimen the displacement d vibration was higher in the portion of the specimen with constant smaller diameter. High s t resses up to the fatigue failure level were generated in this portion of tapered specimens of the 300 grade maraging s teel and 17-4 PH steel. The design of ultrasonic fatigue specimens is discussed in references 22 and 23.

12

TABLE m. - TEST CONDITIONS

Material Temperature I of I K

Displacement I Stress (max) I Test times,

mils I mm I I N/m2 I min

psi

I BOO 700 300 Grade maraging stee 0 0 o 0 15, 60, 180, 360

2.0 .051 22500 1. 55XlOB 15, 60, lBO, 360

3.0 .076 33800 2. 33X10B 15, 30

900 755 0 0 o 0 5, 60, 240, 360

2.0 .051 22500 1. 55X10B 5, 60, 240, 360

0 0 o 0 16

6.4 .163 72 100 4. 97x108 16

1000 B11 0 0 o 0 5, 30, 120, 240, 360

2.0 .051 22500 1. 55X108 5, 30, 120, 240, 360

900 755 17 -4 PH steel 0 0 o 0 5, 15, 30, 60, 120, 360

2.0 .051 22950 1. 58X108 5, 15, 30, 60, 120, 360

0 0 o 0 5

5.0 .127 57400 3. 96x10B 5

1300 978 A-286 0 0 0 0 5, 30, 120

.8 .020 9280 6.40X107 5, 30, 120

1.5 .03B 17400 1. 2OX108 30

2.0 .051 23 200 1. 60X10B 5

1400 1033 Rene 41 0 0 o 0 5, 18, 120, 240

1.0 .025 12250 8.45Xl07 5, 18, 120, 240

2.0 .051 24 500 1. 69X108 5, 18

1600 1144 L-605 (HS-25) 0 0 o 0 600

.8 .020 10 450 7.20Xl07 600

1.4 .036 18300 1. 26X10B 10 (vibration), 600 (static)

grade maraging steel specimen with a 2-mil (5. lX10-2 mm) peak-to-peak displacement is

also included. All values of maximum cyclic stress for all the materials tested were

calculated and are given in table III. The second type of specimen used is shown in figure 7(b). In the tapered specimen

the displacement of vibration was higher in the portion of the specimen with constant

smaller diameter. High stresses up to the fatigue failure level were generated in this

portion of tapered specimens of the 300 grade maraging steel and 17 -4 PH steel. The

design of ultrasonic fatigue specimens is discussed in references 22 and 23.

12

l 4 O 0 l

Test Conditions

The test conditions fo r each material a r e listed in table III. For all materials that were subjected t o ultrasonic vibration a control sample was given a static aging treatment at an equivalent temperature in the heat-treating chamber (fig. 2). Both the static and vibrated specimens were heat treated for the time intervals shown, checked for hardness, and then returned to the heat-treating chamber fo r the next time interval. The specimens were heat treated separately so that vibration would not be transmitted from the ultrasonically vibrated specimen to the statically aged control specimen.

The test temperatures for the alloys were the manufacturers’ recommended aging temperatures. The 300 grade maraging steel was also heat treated 100’ F (55.6 K) above and 100’ F (55.6 K) below the recommended aging temperature.

Temperatures of the heat -treating bath were measured with thermocouples attached to the specimens during static tests (figs. 5 and 6), and also by several thermocouples in the bath during both the static and vibratory tests. Bath temperatures agreed to within *3 0 F (1.7 K) of the measured specimen temperatures in static tests. Typical temperature distributions along the lengths of static specimens a t the heat -treating temperatures considered a r e shown in figure 9.

Several different vibration displacements were applied to determine the effect of s t r e s s on aging. Specimens vibrated a t maximum displacements of more than 3 mils (7. 62x10-2 mm) were of the tapered type described in the previous section.

Furnace temperature, Salt level O F (K) I

16002 1600(1144) c v ”

1 1 0 o r r\ 1400 (1033) ~

U“ 1300 (978) v U Chlor ide

1200

lG0C2 v 1000 (811) Sodium level 1 b,J

? r\ 900 (745) LJ

600L 600I I I I I ~U 0 1 2 3 4 5 6 7

Distance from free end of specimen, in.

I I I I I I - I 0 2 4 6 8 10 12 14 16

Distance f rom free end of specimen, c m

Figure 9. - Typical temperature distr ibut ions in static specimens a t va r ious furnace chamber temperatures.

13

I

Test Conditions

The test conditions for each material are listed in table Ill. For all materials that

were subjected to ultrasonic vibration a control sample was given a static aging treatment

at an equivalent temperature in the heat-treating chamber (fig. 2). Both the static and vibrated specimens were heat treated for the time intervals shown, checked for hard

ness, and then returned to the heat-treating chamber for the next time interval. The

specimens were heat treated separately so that vibration would not be transmitted from

the ultrasonically vibrated specimen to the statically aged control specimen.

The test temperatures for the alloys were the manufacturers' recommended aging

temperatures. The 300 grade maraging steel was also heat treated 1000 F (55.6 K)

above and 1000 F (55.6 K) below the recommended aging temperature.

Temperatures of the heat-treating bath were measured with thermocouples attached

to the specimens during static tests (figs. 5 and 6), and also by several thermocouples in

the bath during both the static and vibratory tests. Bath temperatures agreed to within

±3° F (1. 7 K) of the measured specimen temperatures in static tests. Typical tempera

ture distributions along the lengths of static specimens at the heat-treating temperatures

considered are shown in figure 9.

Several different vibration displacements were applied to determine the effect of stress on aging. Specimens vibrated at maximum displacements of more than 3 mils

(7. 62xlO-2 mm) were of the tapered type described in the previous section.

1600 noo

1400 ~

1000 ~-~

ro 1200 900 ~

'" E -!'<

SOO c 1000 '" EO 'u '" c.

700 Vl SOO

600 600

Furnace temperature, Salt level OF (K)

~ 1600 (1144)

1400 (1033) '"' ~

1300 (97S) 0 0

~,' Chloride salt -

1000 (Sll) ~

900 (755) v "-} ~

SOO (700) :: Sodium ~

~

I I 0 2 3 4 5 6


0 2 4 6 S 10 12 14 16 Distance from free end of specimen, cm

Figure 9. - Typical temperature distributions in static specimens at various furnace chamber temperatures.

13

•

Test Procedure

The heat -treating bath was brought to the desired test temperature before inserting the test specimen. A temperature drop was observed in the bath upon immersion but the desired test temperature was usually attained in less than 10 minutes. The tes t t ime was measured from the t ime when the temperature of the lower 1/2 wavelength region of the specimen was within 20' F (11.1K) of the desired test temperature.

A hardness t raverse was made on each specimen in the solution treated condition for reference purposes. The hardness tester was equipped with an adapter to handle cylindr ical specimens. Measurements on tapered specimens were taken along the constant diameter portion using a s imilar type of adapter. Hardness measurements were reproducible within &O. 5 unit on the Rockwell C scale and r t l . 0 unit on the Rockwell B scale. After each incremental aging treatment (table 111) the specimen was removed, air cooled, cleaned, and hardness measurements were taken along the specimen length. Specimens heat treated in sodium were cleaned first with alcohol, then water, and dried with cleaning tissue. Specimens treated in salt were cleaned by polishing until all the salt scale was removed. Bearing surfaces were always polished to remove any metal raised by previous Rockwell impressions.

After aging for 6 hours, tensile tes t s were conducted with specimens cut from both static and vibrated 300 grade maraging s teel straight bar specimens. Figure 10 shows a drawing of the standard tensile specimen used for these tests. It was cut f rom the lower 1/2 wavelength portion of each b a r specimen in such a way that the nodal portion of the test b a r was approximately in the center of the tensile specimen.

Metallographic examinations were made of L-605 specimens to determine the dis t r i bution of visible precipitates resulting from both the static and the ultrasonic vibration aging.

3. 00 (7.62)-

CD-10249-32

Figure 10. - Standard tensi le specimen c u t f rom nodal po r t i on of aged straight bar specimens. (All dimensions in inches (cm).)

14

Test Procedure

The heat-treating bath was brought to the desired test temperature before inserting

the test specimen. A temperature drop was observed in the bath upon immersion but the

desired test temperature was usually attained in less than 10 minutes. The test time was

measured from the time when the temperature of the lower 1/2 wavelength region of the

specimen was within 200 F (11. 1 K) of the desired test temperature.

A hardness traverse was made on each specimen in the solution treated condition for

reference purposes. The hardness tester was equipped with an adapter to handle cylin

drical specimens. Measurements on tapered specimens were taken along the constant

diameter portion using a similar type of adapter. Hardness measurements were repro

ducible within ±O. 5 unit on the Rockwell C scale and ±1. 0 unit on the Rockwell B scale.

After each incremental aging treatment (table III) the specimen was removed, air cooled,

cleaned, and hardness measurements were taken along the specimen length. Specimens

heat treated in sodium were cleaned first with alcohol, then water, and dried with clean

ing tissue. Specimens treated in salt were cleaned by polishing until all the salt scale

was removed. Bearing surfaces were always polished to remove any metal raised by

previous Rockwell impressions. After aging for 6 hours, tensile tests were conducted with specimens cut from both

static and vibrated 300 grade maraging steel straight bar specimens. Figure 10 shows

a drawing of the standard tensile specimen used for these tests. It was cut from the

lower 1/2 wavelength portion of each bar specimen in such a way that the nodal portion of

the test bar was approximately in the center of the tensile specimen.

Metallographic examinations were made of L-605 specimens to determine the distri

bution of visible preCipitates resulting from both the static and the ultrasonic vibration

aging.

14

r 7116 in. -14 thread Gage length r Radius, r O. 44

1\ ~(~~6r L~'z~'-l =-1

0.

25(0.64) J\(L12)

~ I ~-- \ 11

I I ?:- 250 J 1· 0·.· 3"·8··· 1

0. 5 J -

~. 5 --Lo. 38 ~635)--' L 25 -l--

(L 27) (0.97) (3. 18) (0.97) (1.27) _ , 3.00 (7.62)

CD-10249-32

Figure 10. - Standard tensile specimen cut from nodal portion of aged straight bar specimens. (All dimensions in inches (cm). )

RESULTS AND DISCUSSION

Comparison of Hardness Af ter Static Aging

and Ultrasonic Vibrat ion Aging

The hardness distribution along the length of static and vibrated straight ba r specimens treated at different temperatures are presented in figures 11 to 14. The static and vibrated specimens are compared at various time intervals from 5 to 360 minutes. Solid lines represent specimens that were heat treated with no vibration, and the dotted lines represent specimens that were vibrated ultrasonically while they were being heat treated. Generally, the maximum hardness reached by vibrated specimens was the same as that reached by statically aged specimens. Also, the ultrasonically vibrated specimens usually reached maximum hardness sooner than specimens that were statically aged. Overaging was observed ear l ie r for ultrasonically vibrated than for statically aged alloys.

46 Vibrated at 25 000 Hz. 2 mils ( 5 . 1 ~ 1 0 - ~mm)

40 38

0 1 2 3 4 5 6 Distance from free end of specimen, in.

I I I I I I 1 - 1 0 2 4 6 8 10 12 14

Distance from free end of specimen, c m

(a) Temperature, 800' F (700 K). Hardness at 0 time: RC 29. 6 to 30.8.

Figure 11. - Comparison of hardness resu l t s between static aging and ul t rasonic v ibrat ion aging at var ious times for 300 grade maraging steel. Heat t reat ing medium, sodium.

15

RESULTS AND DISCUSSION

Comparison of Hardness After Static Aging

and U Itrason ic Vibration Aging

The hardness distribution along the length of static and vibrated straight bar speci

mens treated at different temperatures are presented in figures 11 to 14. The static and vibrated specimens are compared at various time intervals from 5 to 360 minutes. Solid

lines represent specimens that were heat treated with no vibration, and the dotted lines

represent specimens that were vibrated ultrasonically while they were being heat treated. Generally, the maximum hardness reached by vibrated specimens was the same as that reached by statically aged specimens. Also, the ultrasonically vibrated specimens usually reached maximum hardness sooner than specimens that were statically aged. Overaging was observed earlier for ultrasonically vibrated than for statically aged alloys.

u a; l; u 0

"'" :i Q.>

c "2 no :c

Time, Node Al2 Node min ~ ~ 52 360

50 --~- ----'-------I I Sodium + ,level

--, 48

46

'-

50~ ----------=-" 48 180

" 46 '\. ~ 44

'y -------.....---...... '- ------46 60 ~ 44 "-

~ I 42

:r 15 Vibrated at 25 000 Hz, 2 mils (5. lxlO-2 mm)

42 '---Static ---........ 40 ........

1 '-38

0 2 4 5 6 Distance from free end of specimen, in.

I I I_~ 0 4 6 8 10 12 14

Distance from free end of specimen, cm

(a) Temperature, 800 0 F (700 Kl. Hardness at 0 time: RC 29.6 to 30.8.

Figure 11. - Comparison of hardness results between static aging and ultrasonic vibration aging at various times for 300 grade maraging steel. Heat treating medium, sodium.

15

---

300 grade maraging steel. - The hardness curves for the 300 grade maraging steel -~

specimens aged at 800°,. 900°, and 1000° F (7'00, 755, and 811 K) a r e presented in figure 11. The distance from 0 to 3 inches (7.5 cm) from the free end of the specimen is the most significant portion of each of the hardness curves because the heat-treating bath temperature was most uniform in this zone. For the vibrated specimen treated at 800' F (700 K) (fig. ll(a)), a slight increase in hardness over the statically aged specimen was observed at 60 minutes, but after 180 minutes exposure, the two specimens exhibited nearly equal hardness values. The maximum increase in hardness of the vibrated over the static specimen was approximately 1. 5 points on the Rockwell C hardness scale at any specified time. At 900' F (755 K) (fig. l l (b)) , the vibrated specimen showed a slight (about 1point) hardness increase over the statically aged specimen f rom 5 to 60 minutes, but nearly the same hardness beyond 240 minutes.

A12 Time,

I.----\

I I I -hI

50r

/ ./-\

\46 44 I I I I I

16

~~ - . ..., ,, -..-. . . ...,. I.. .I I 1

300 grade maraging steel. - The hardness curves for the 300 grade maraging steel

specimens aged at 800°,. 900°, and 1000° F (700, 755, and 811 K) are presented in fig

ure 11. The distance from 0 to 3 inches (7. 5 cm) from the free end of the specimen is the most significant portion of each of the hardness curves because the heat-treating bath

temperature was most uniform in this zone. For the vibrated specimen treated at 800° F

(700 K) (fig. l1(a», a slight increase in hardness over the statically aged specimen was observed at 60 minutes, but after 180 minutes exposure, the two specimens exhibited nearly equal hardness values. The maximum increase in hardness of the vibrated over

the static specimen was approximately 1. 5 pOints on the Rockwell C hardness scale at any specified time. At 900° F (755 K) (fig. l1(b», the vibrated specimen showed a slight

(about 1 point) hardness increase over the statically aged specimen from 5 to 60 minutes,

but nearly the same hardness beyond 240 minutes.

16

Node N2 Node Time, min

52 360

! ~ I I Sodium , + level

=:==--~---

50

48'------~-

'F 240 ~--~ 50 ...... -----.,. u I I~ ~

48 .

;:§:M _________ --, ~ 46 ~ ~ 44 I. I I I I

46

44

5 ---.. Vibrated at 2 mils (5.1xlO-2 mm)

-- ----------- ..........

42

40'--------'-o 2

Static

3 4 Distance from free end of specimen, in.

o 2 4 6 8 10 12 Distance from free end of specimen, em

5

" \

I 14

6

(b) Temperature, 900° F (755 KL Hardness at 0 time: RC 28.9 to 30. O.

Figure 11. - Conti nued.

I I

0

52

48 ---I--

35 48-E

vi 46 1 I I

I I

At 1000° F (811 K) (fig. 1l(c))the vibrated specimen exhibited about a two-point increase in hardness af ter 5 minutes exposure over the statically aged specimen. However, at 30 and 120 minutes the two specimens were nearly equal in hardness. At 240 and 360 minutes the vibrated specimen decreased in hardness due to overaging compared to the statically aged specimen.

17-4 PH.stee1. - A comparison of hardness curves for vibrated and statically aged specimens of 17-4 PH s tee l is presented in figure 12. After 5 minutes the vibrated specimen showed a higher hardness than the statically aged specimen. A difference of about 2.5 Rockwell C scale units was noted.

The vibrated 17-4 PH s tee l specimen reached peak hardness in 15 minutes at 900' F (855 K) as compared to 30 minutes for the statically aged specimen. At 360 minutes the hardness of the vibrated specimen was as much as 2. 5 Rockwell C units below that of the statically aged specimen, but both specimens overaged.

17

I

u a; =: "'" u 0

"" ~-

'" c 1: '" :r:

Node N2 Node . ~ radiUm Time,

~ l min 52 360 50 -----....---1---48

52

50

48

46

T 50

48

46

--=--3_0 --=:,.... ____ ....:._-______ - __ ---..

46 _ -

48~ ___ ~ ____ V~ated~-=-m~: lxlO-2 ~~

44 Static -- ~ 42 I I I

level

" '\j

o 2 3 4 5 6 Distance from free end of specimen, in.

o 2 4 6 8 10 12 14 Distance from free end of specimen, cm

(cl Temperature, 10000

F (811 KI. Hardness at 0 time: RC 27.2 to 29. 1.

Figure 11. - Concluded.

At 10000 F (811 K) (fig. l1(c» the vibrated specimen exhibited about a two-point in

crease in hardness after 5 minutes exposure over the statically aged specimen. However,

at 30 and 120 minutes the two specimens were nearly equal in hardness. At 240 and 360

minutes the vibrated specimen decreased in hardness due to averaging compared to the

statically aged specimen.

17 -4 PH.steel. - A comparison of hardness curves for vibrated and statically aged

specimens of 17 -4 PH steel is presented in figure 12. After 5 minutes the vibrated

specimen showed a higher hardness than the statically aged specimen. A difference of

about 2.5 Rockwell C scale units was noted.

The vibrated 17 -4 PH steel specimen reached peak hardness in 15 minutes at 9000 F

(855 K) as compared to 30 minutes for the statically aged specimen. At 360 minutes the

hardness of the vibrated specimen was as much as 2. 5 Rockwell C units below that of the

statically aged specimen, but both specimens averaged.

17

0

U

a,

---

-- --

Time, m i n

38 I I I

40

- ZF =I--A------=60 -__---540 I I I I I 0

30

c

L

15 /----,---,

40 38 I

,-Vibrated at 2 m i l s 5 ,' (5 .1~10-2mm)

38 .-.-L---, \ I

36 r0 1 2 3 4 5 6


U I I I I I I 0 2 4 6 8 10 12 14


Figure 12. - Comparison of hardness resu l t s between static aging and u l t rason ic v ibrat ion aging at var ious t imes at 900' F (755 K) for 17-4 PH steel. Heat t reat ing medium, sodium. Hardness at 0 time: RC 31.9 to 32.6.

18 18

: j':;)J2 ~~I~:.ll b Time,

40 ----:- J: -------38 -1--1- I I I

42 ---- __ 44~ 120 _

40 - --+----r----t--i- J

4442l=L ~----------'---40 . I I I I I

:t-40

38 I

15 ,.",.----------------

"b I - ,~Vlb"t.d ,11 mIl, 40 - - ......... 5 " (5.1xl0-2 mml Static ---L. ___ _

~ ---36 I I I

o 1 3 4 5 6

o


2 4 8 10 12 14 Distance from free end of specimen, cm

Figure 12. - Comparison of hardness results between static aging and ultrasonic vibration aging at various times at 900" F (755 Kl for 17-4 PH steel. Heat treating medium, sodium. Hardness at o time: RC 31. 9 to 32.6.

A-286. - Hardness curves for statically aged and vibrated A-286 specimens are shown in figure 13. Vibration displacements of 0.8, 1. 5, and 2 mils (2. 0, 3.8, and 5.1X10- 2 mm) were used. Since these tes t s were run a t 1300' ?' (978 K) , which is near the upper limit of reasonable strength for this material, i t w a s necessary to go to reduced vibrational displacements to permit test operation for relatively long times. In each of these tests, the displacement decreased continuously during the last 4 to 5 minutes of the test. When the displacement decreased to about 30 percent of the original displacement, the test was terminated.

After 5 minutes no improvement was observed for the vibrated specimens over the statically aged specimen. But after 30 minutes, specimens vibrated at both 0.8 and 1. 5 mils showed an increase in hardness of about 2 Rockwell B scale units above the hardness of the statically aged specimen, and at the nodal point the increase w a s 4 Rockwell B units for 1.5 mil vibrated specimens. The specimen vibrated at 0 .8 mils (2. Ox10-2 mm) remained 1. 5 Rockwell B units harder than the statically aged specimen after 120 minutes.

Ren6 41. - Hardness curves for specimens of Ren6 41 a r e shown in figures 14(a) and (b). Figure 14(a) shows the hardness resul ts for the statically aged specimen and a specimen vibrated initially a t 2 mils (5. 1 ~ 1 0 - ~mm) and figure 14(b) shows a similar comparison f o r the statically aged specimen and a specimen vibrated a t 1 mil (2. 5x10-2 mm).

The specimen vibrated a t 2 mils (5. 1 ~ 1 0 - ~mm) failed after 18 minutes of testing. Failure w a s indicated by a gradual decrease in the vibration displacement from 2 mils (5. 1 X 1 O T 2 mm) to about 0. 2 mils (0. 5X10-2 mm) during the last 5 minutes of the 18 minute test. The vibrated specimen showed no improvement in the hardness over the static specimen. A zero time hardness plot is included in figure 14(a) to show that the two as-received specimens had a n initial hardness difference of about 2 Rockwell C units.

A hardness peak w a s observed in the curve f o r the specimen that was vibrated for 18 minutes near the upper node. This portion of the specimen was above the heat-treating fluid level. Consequently, the effects observed in this region a r e considered to be outside of the scope of this investigation. It is believed that the hardness peak observed with the vibrating specimen near the upper node is not particularly significant, but it may be indicative of a possible optimum combination of vibratory s t r e s s , environment, time, and temperature fo r this alloy. Severe cracking was also observed near the upper node of this specimen. The specimen vibrated at 1 mil (2. 5X10-2 mm), figure 14(b), showed no significant hardness increase over the statically aged specimen until after 120 minutes of vibration. At 240 minutes the vibrated specimen had a maximum hardness increase of 2 Rockwell C units above the hardness of the static specimen. The hardness (Rockwell C 40) reached by the vibrated specimen in 4 hours is equivalent to the optimum hardness that can be reached by statically aging this alloy for 16 hours.

19

A -286. - Hardness curves for statically aged and vibrated A -286 specimens are

shown in figure 13. Vibration displacements of 0.8, 1. 5, and 2 mils (2.0, 3.8, and

5. 1xlO-2 mm) were used. Since these tests were run at 13000 t" (978 K), which is near

the upper limit of reasonable strength for this material, it was necessary to go to reduced

vibrational displacements to permit test operation for relatively long times. In each of

these tests, the displacement decreased continuously during the last 4 to 5 minutes of the

test. When the displacement decreased to about 30 percent of the original displacement,

the test was terminated.

After 5 minutes no improvement was observed for the vibrated specimens over the

statically aged specimen. But after 30 minutes, specimens vibrated at both O. 8 and 1. 5

mils showed an increase in hardness of about 2 Rockwell B scale units above the hardness

of the statically aged specimen, and at the nodal point the increase was 4 Rockwell B

units for 1. 5 mil vibrated specimens. The specimen vibrated at 0.8 mils (2. OXlO-2 mm)

remained 1. 5 Rockwell B units harder than the statically aged specimen after 120 minutes.

Rene 41. - Hardness curves for specimens of Rene 41 are shown in figures 14(a)

and (b). Figure 14(a) shows the hardness results for the statically aged specimen and a

specimen vibrated initially at 2 mils (5. 1X10-2 mm) and figure 14(b) shows a similar com

parison for the statically aged specimen and a specimen vibrated at 1 mil (2. 5xl0-2 mm).

The specimen vibrated at 2 mils (5. lX10- 2 mm) failed after 18 minutes of testing.

Failure was indicated by a gradual decrease in the vibration displacement from 2 mils

(5. 1xlO-2 mm) to about 0.2 mils (0. 5X10-2 mm) during the last 5 minutes of the 18 minute

test. The vibrated specimen showed no improvement in the hardness over the static

specimen. A zero time hardness plot is included in figure 14(a) to show that the two as

received specimens had an initial hardness difference of about 2 Rockwell C units.

A hardness peak was observed in the curve for the specimen that was vibrated for

18 minutes near the upper node. This portion of the specimen was above the heat-treating

fluid level. Consequently, the effects observed in this region are considered to be out

side of the scope of this investigation. It is believed that the hardness peak observed

with the vibrating specimen near the upper node is not particularly significant, but it may

be indicative of a possible optimum combination of vibratory stress, environment, time,

and temperature for this alloy. Severe cracking was also observed near the upper node

of this specimen. The specimen vibrated at 1 mil (2. 5XIO- 2 mm), figure 14(b), showed

no significant hardness increase over the statically aged specimen until after 120 minutes

of vibration. At 240 minutes the vibrated specimen had a maximum hardness increase of

2 Rockwell C units above the hardness of the static specimen. The hardness (Rock-

well C 40) reached by the vibrated specimen in 4 hours is equivalent to the optimum hard

ness that can be reached by statically aging this alloy for 16 hours.

19

-------- 24r

96

94 1 2 L

90

0

20

Node N2 Node Time, Salt n i i n 120

/-

1.5 mi l s ( 3 . 8 ~ 1 0 - ~mm)

Static

0.8 mi ls (2. Oxlo-? m m ) P

I1- I . . I I

Distance f rom free end of specimen, in.

2 4 6 8 10 12 14 Distance f rom free end of specimen, cm

Figure 13. - Comparison of hardness resu l t s between static aging and ul t rasonic v ibrat ion aging at var ious times at 1300" F (978 K) fo r A-286. Heat t reat ing medium, ch lo r i de salts. Hardness at 0 time: R B 76.0 to 78.8.

I

~-~ 24E '" Q; 20 c ;;. "0 -'" ~ u :'J! ~ 16

12

20

Node IJ2 Node I Time, I Salt , min t level ------~--- ~

i 102

100

98

96

................... 0.8 mil '" (2. OxlO-2 mm)

94

92 -

90L---L~ - j

" \ \

~~~[ / ~~ 30 1. 5 mils (3. 8xl0-2 mm)

: 98 ~ ~~~~\ '" " ~ 96 Static / \ \

i- ::t 0.8 mils (2. Oxl0-2

mm)...l '\ \

:: '" 90 :r: 88 --..l~ I . . j

92

90

88

86

84

82

~ ......... __ 5

/"" -"\------~~ \- 0.8 mil (2. Oxl0-2 mm)

~ ~ 2.0 mil

~O

78'------'-

'-" (5. lxlO-2 mm)-;

---.,/..--~ .J __ I -.. 1

4 o

o

2 3 5 Distance from free end of specimen, in.

L _ . j _ 1 _I 2 4 6 8 10 12 14


Figure 13. - Comparison of hardness results between static aging and ultrasonic vibration agi ng at various times at 1300° F (978 K) for A-286. Heat treating medium, chloride salts. Hardness at 0 time: RB 76.0 to 78. 8.

6

-----.----.----••••••• ,-'~. _ .. __ •• ~.~. ~., •• =. _~.-----.---" ._-_ •• _-••••• 11. __ 11. 11, •••••••• _ ................... 1 I.I~_III 11.lllrl-----

28

26

24

22

20

0::I --t ---j----I----- 4 -3

18 --I-0 1 2 3 4 5 6


I II I 1' 0 2 4 6 8 10 12 14


(a) Ul t rasonic v ibrat ion at 2 mi ls (5. lxlO-' mm).

Figure 14. - Comparison of hardness results between static aging and ul t rasonic v ibrat ion aging at var ious times at 1400" F (1033 K) for Ren6 41. Heat t reat ing medium, chlor ide salts.

21

u

'" s: .><: u 0

C>::

~-

'" C ""0 ~

'" ::r::

38

36

34

32

30

28

26

24

22

20

32

30

28

26

24

22

20

18

Node

l Time, min

--_-.....,.,- ........... -----5

AI2 Node , Salt t level

~ / l

( \ I \

./ \ ............ \

\ \ \ \ \ \

:'--.., Vibrated at 25 000 Hz

\ \ \

" ........ -

22F 20

18

o ----------------------------,--- -1-----(- --,--------1---1

0

o

2 4 5 Distance from free end of specimen, in.

2 4 6 8 10 12 14 Distance from free end of specimen, cm

(a) Ultrasonic vibration at 2 mils (5. lxlO-2 mm).

Figure 14. - Comparison of hardness results between static aging and ultrasonic vibration agi ng at various times at 1400° F (1033 K) for Rene 41. Heat treating medium, chloride salts.

6

21

D

\I . ...j I . I

40

38

0 32

30 I . I

vi c 36

30 \ 28 \

\ 26 \

I I I 0 1 2 3 4 5 6

Distance f r o m free end of specimen, in.

I - . - I I I 1 I . I 0 2 4 6 a 10 12 14

Distance f r o m free end of specimen, c m

(b) Ul t rasonic v ib ra t ion at 1 nil (7. 5x10-' mm). Hardness at 0 time: RC 20.0 to 21. x.


22 22

Node

~ Time, Al2 ! Salt

42 min ~ level

40 _ ""'-.....//""" __ .l..4O ____ ,

38 "-\

36 ~ 34

32

30

28 . .1

40

38 120

~----"-,,-36

34

u 32

~ 30 .'" J ~ 28---~~

'" c 36

~ 34 r

32

30

28

26

24 -

22

20

30 . ~-------.. ------- ............

5 '-....

\ ~

~ \ I

3Z[ 28 \ Vibrated

26-

24--o

Static \

I \ 3 4


I~~I_. - I .1 o 2 4 6 8 10 12 14

Distance from free end of specimen, em

6

(bl Ultrasonic vibration at 1 r:1il (2. 5xlO-2 mm). Hardness at 0 time: RC 20. 0 to 21. R.


L-605. - Hardness curves are not shown for L-605 because no sign3ican.t change in hardness was observed on aging the annealed material. This material was tested primarily to make metallographic studies of the precipitate distribution..

Effect of Vibration Stress on Aging

When ultrasonic vibration is applied to a straight bar type specimen by direct coupling to the transducer, the specimen will vibrate most efficiently at a resonant frequency, determined by its length. The specimen length is usually chosen to be a multiple of 1/2 the wavelength of the applied frequency. When the specimen vibrates, s t r e s s within the specimen can vary from near zero at the free vibrating end to a maximum at the stationary nodes. Certain investigators considered the effect of this variable s t r e s s on diffusion of nitrogen in steel (ref. 24); and others showed that there was increased carburization of iron in the highly s t ressed nodal regions of their specimens (ref. 1.3). However, in most investigations of ultrasonic aging very little mention is made of the effect of variable stress in specimens. If applied s t r e s s were important in the aging process, it might be expected that large variations in the degree of age hardening shoilld occur within each specimen.

0 1 2 3 4 5 6 Distance f rom free end of specimen, in.

I I I I l l -0 2 4 6 8 10 12 14


Figure 15. - Comparison of hardness resu l t s between s!atic aging and u l t rason ic v ibrat ion aging at Val-ious times at 800' F ( io0 K I for 300 grade maraging steel. Heat t reat ing medium, sodium. Hardness at 0 time: RC 29. 6 to 30. 8.

23

L-605. - Hardness curves are not shown for L-605 because no significant change in

hardness was observed on aging the annealed material. This material was tested pri

marily to make metallographic studies of the precipitate distribution.

Effect of Vibration Stress on Aging

When ultrasonic vibration is applied to a straight bar type specimen by direct cou

pling to the transducer, the specimen will vibrate most efficiently at a resonant fre

quency, determined by its length. The specimen length is usually chosen to be a multi

ple of 1/2 the wavelength of the applied frequency. When the specimen vibrates, stress

within the specimen can vary from near zero at the free vibrating end to a maximum at

the stationary nodes. Certain investigators considered the effect of this variable stress

on diffusion of nitrogen in steel (ref. 24); and others showed that there was increased

carburization of iron in the highly stressed nodal regions of their specimens (ref. 1.3).

However, in most investigations of ultrasonic aging very little mention is made of the

effect of variable stress in specimens. If applied stress were important in the aging

process, it might be expected that large variations in the degree of age hardening should

occur within each specimen.

Node Node

, Time, 12 ~ 48 t min t Sodium

46-~">--~~ __ 'level ::;:._. -~-~-=--- +

~ :- --~~~\ ~40 I' ,'\~j ""

f :~=-........ ~:,...~-....~~ (7. 6xlO-2

mm) :I Static '---~ --_

42 --~ -2 / ~ 40 2 mils (5. lxID mm)-" ,,~

38 , , , , l .... ~ o 1 2 3 4 5 6

o


I 2 4 6 8 ID 12 14


Figure 15. - Comparison of hardness results between static aging and ultrasonic vibration aging at various times at 800

c F 000 K)

for 300 grade maraging steel. Heat treating medium, sodium. Hardness at 0 time: RC 29.6 to 30. 8.

23

Hardness curves for specimens vibrated at different displacements are shown in f igures 13 to 17. It was observed in general that s t r e s ses resulting from different ultrasonic vibration displacements ranging from 0.8 mi l (2. 0X1Ow2 mm) (straight ba r specimen) up to 6.4 mils (16. 3X10-2 mm) (tapered specimens) had no consistent and apparently no appreciable effect on the aging results. Also, at the nodal points where stress and s t ra in were maximum, essentially no difference was noted between the hardness at this part of the specimen and at other locations that were subjected to less stress and strain.

In the few cases where increased hardness was observed at nodes, cracks were also observed in the nodal region. The cracking may be due to a fatigue mechanism. This cracking may have also caused some scatter of hardness data in this region. Results for specific materials are discussed in the following sections:

300 grade maraging steel. - Specimens of the 300 grade maraging s teel were aged at._-

800' F (700 K), and the hardness curves for a statically aged specimen and straight bar specimens vibrated at 2 and 3 mils (5 .1 and 7 .6~10- ' mm) are shown in figure 15. The curves for the 2 - and 3-mil (5.1- and 7 . 6 ~ 1 0 - ~ - m m )vibration specimens are essentially the same and also overlap the static specimen hardness curves. Also, in this figure the hardness at the lower node is not significantly higher than the hardness at the antinode. These curves support the conclusion that during aging an increased vibration s t r e s s does not increase the hardness of the alloy.

Figure 16 shows the hardness curves for the 900' F (755 K) aging tes t s of tapered specimens of the 300 grade maraging steel. The vibrated specimen was run until fracture occurred near the node. This specimen was vibrated at 6.4 mils (16. 3X10-2 mm) and it

54l

0

- 4 4 ,Y

6,4 mi ls

fo r 16 m i n specimen

I

24

.----I- .11-1-.-11 11.1.11 1 . 1 1 I I l l 1 1 1 1 1 I 1111 I I I I I I I 11111111111 1111111 11111 11111111 I 1111 I 1 1 1 1 1 I

Hardness curves for specimens vibrated at different displacements are shown in

figures 13 to 17. It was observed in general that stresses resulting from different ultra

sonic vibration displacements ranging from 0.8 mil (2. OX10-2 mm) (straight bar speci

men) up to 6.4 mils (16. 3X10-2 mm) (tapered specimens) had no consistent and apparently

no appreciable effect on the aging results. Also, at the nodal points where stress and

strain were maximum, essentially no difference was noted between the hardness at this

part of the specimen and at other locations that were subjected to less stress and strain.

In the few cases where increased hardness was observed at nodes, cracks were also

observed in the nodal region. The cracking may be due to a fatigue mechanism. This

cracking may have also caused some scatter of hardness data in this region. Results

for specific materials are discussed in the following sections:

300 grade maraging st~~l. - Specimens of the 300 grade maraging steel were aged at

8000 F (700 K), . and the hardness curves for a statically aged specimen and straight bar

speCimens vibrated at 2 and 3 mils (5.1 and 7. 6XlO-2 mm) are shown in figure 15. The

curves for the 2 - and 3 -mil (5. 1- and 7. 6x10 -2 -mm) vibration specimens are essentially

the same and also overlap the static specimen hardness curves. Also, in this figure the hardness at the lower node is not Significantly higher than the hardness at the antinode.

These curves support the conclusion that during aging an increased vibration stress does

not increase the hardness of the alloy.

Figure 16 shows the hardness curves for the 9000 F (755 K) aging tests of tapered

specimens of the 300 grade maraging steel. The vibrated specimen was run until fracture occurred near the node. This specimen was vibrated at 6.4 mils (16. 3xlO-2 mm) and it

48 z

u '" "" a; = ~ 46 '" 3: u ."-' 0 U

0:: 0

44 0::

:i ~-

'" c: 42 '" 1:

c: 1:

'" '" ::r:: 40 ::r::

24

54

50 ~ ,....---- ............... -./ ~

/, Break LVibrated at

46 6.4mils tN d f·b t d (16. 3xlO-2 mm) 0 e.o VI ra e for 16 min specimen

42 I I I 0 2 3


I I I 0 2 4 6 8


Figure 16. - Hardness results from static aging and ultrasonic aging of tapered specimens of 300 grade maraging steel at 900° F (755 Kl. Heat treating medium, sodium. Hardness at 0 time; Rockwell 45N 26.5 to 29.6

-----_.--___ 1- 1 .. _1 ___ 11....... ._ •• I' •• UII. 11111 I 1111.1111111 •• 111 III .... IIIII 111 •••• 1 I 1111 I 111111

Node of

z 3

45

43

42

failed after approximately 16 minutes. After 16 minutes the hardness of this vibrated specimen was within 2 Rockwell 45 N units of the specimen statically aged for 16 minutes.

It is significant that the vibrated specimens showed no increase in hardness near the node as compared to the remaining portions of the specimen. Thus, in this case, u l t ra sonic vibration s t r e s s had no observable effect on the age -hardening reaction.

17-4PH Steel. - Hardness curves fo r tapered specimens of 17-4 PH steel are presented in figure 17. Static and vibrated specimens were aged fo r approximately 5 minutes a t 900' F (755 K). The vibrated specimen failed after 5 minutes. Although considerable scat ter is evident in the hardness data of the vibrated specimen, most hardness values of this specimen were approximately 2 units on the Rockwell 45 N scale above Ihose of the statically aged specimen. It was a l so noted that hardness values of the vibrated specimen were no higher in the highly s t ressed nodal region than they were in other parts of the specimen.

A-286 and Ren6 41. - The effects of increased vibration stress on hardness fo r A-286 and Re& 41 are presented in figures 13 and 14, respectively, and have been discussed previously. These resul ts a l so indicated that ultrasonic stress did not appreciably affect the hardness.

Comparison of Tensi le Test Data from Statically

Aged and Vibrated Aged Specimens

Tensile tests were made to determine if ultrasonic vibration of specimens during aging had any effect on tensile strength, yield strength, and ductility. The resul ts of

25

z 50 !;g

45~ ~ 49 g 48 44 "" 43 ~-

'" c

42 ~ :r: 45

a

Node of vibrated speci men

~ .-- Vibrated at 5 mils r\. II (12.7xlO-2 mml

1'-.//1\ I ./\\for 5 min '/ r--

~\ I f~reak [""Slatic a.ged

\ for 5 min

I I 123


I I I a 2 4 6 8


Figure 17. - Hardness results from static aging and ultrasonic aging of tapered specimens of 17-4 PH steel at 900° F (755 Kl. Heat treati ng medium, sodium. Hardness at a time: Rockwell 45N 38. 8 to 39.4.

failed after approximately 16 minutes. After 16 minutes the hardness of this vibrated

specimen was within 2 Rockwell 45 N units of the specimen statically aged for 16 minutes.

It is significant that the vibrated specimens showed no increase in hardness near the

node as compared to the remaining portions of the specimen. Thus, in this case, ultra

sonic vibration stress had no observable effect on the age -hardening reaction.

17-4 PH Steel. - Hardness curves for tapered specimens of 17-4 PH steel are pre

sented in figure 17. Static and vibrated specimens were aged for approximately 5 minutes

at 9000 F (755 K). The vibrated specimen failed after 5 minutes. Although consider.able

scatter is evident in the hardness data of the vibrated specimen, most hardness values of

this specimen were approximately 2 units on the Rockwell 45 N scale above those of the

statically aged specimen. It was also noted that hardness values of the vibrated specimen

were no higher in the highly stressed nodal region than they were in other parts of the

specimen. A-286 and Rene 41. - The effects of increased vibration stress on hardness for A-286

and Rene 41 are presented in figures 13 and 14, respectively, and have been discussed

previously. These results also indicated that ultrasonic stress did not appreciably affect

the hardness.

Comparison of Tensile Test Data from Statically

Aged and Vibrated Aged Specimens

Tensile tests were made to determine if ultrasonic vibration of specimens during

aging had any effect on tensile strength, yield strength, and ductHity. The results of

25

TABLE IV. - ROOM TEMPERATURE TENSILE PROPERTY DATA OF 300 GRADE MARAGING

STEEL SPECIMENS AFTER AGING AT VARIOUS TEMPERATURES FOR 6 HOURS

I"Specimen Aging tempera. Yield strength (0. 2 percent Ultimate strengtt E longation ReductionI ture percent in a rea ,

K psi N/m2 psi 1 - N/m2 percent

Static 700 260 500 1.80x1O9 267 700 1.84X10' 9.6 46. 1 Vibrateda 800 700 264 900 1.83 270 700 1.87 9 .6 47.1 Static 755 273 500 1.89 279 400 1.93 9.6 52.7 Vibrateda 900 755 277 000 1.91 281 900 1.94 9. 2 52.8 Static 1000 811 256 700 1.77 268 900 1.85 10. 0 52.4 Vibrateda 1000 811 241 400 1.67 255 900 1.77 11. 2 45. 2

"Node of vibrated specimen at center of tensile specimen.

the tensile tes ts of the 300 grade maraging s tee l specimens a r e presented in table IV and shown in figure 18. The solid line represents the statically aged specimens and the dotted lines the vibrated specimens. From figure 18 it can be seen that at 800' and 900' F (700 and 755 K), the tensile strengths and yield strengths of the vibrated specimens were higher than those of the static specimens by approximately 1and 2 percent, respectively. The effect of vibration on ductility, a t 900' F (755 K) was to decrease elongation from 9 . 6 to 9 . 2 percent. After aging at 1000° F (811 K) the tensile and yield strengths of the vibrated specimen decreased by approximately 5 and 6 percent, respectively, below the strengths of the statically aged specimen. This drop was due to overaging of the mater ial. The elongation increased by approximately 1 percent but the reduction in a r e a of this specimen a t f rac ture decreased from approximately 52 to 46 percent.

In general, changes in the tensile properties of specimens sugjected to ultrasonic vibration were slight; but these changes were consistent with the resul ts of hardness tes t s presented previously.

Metallograph ic Study of Precipitate in L-605

Most of the precipitates formed during the previous aging tes t s were submicroscopic in size and would have been visible only after overaging for very long times. L-605, however, is a n alloy which forms an observable precipitate near the grain boundaries in relatively short aging times. Investigators have found that working this alloy before aging can cause precipitates to nucleate and grow within the matrix (ref. 19). In the present investigation it was desirable to see if ultrasonic vibration could similarly inf luence the location of the precipitate.

26

TABLE IV. - ROOM TEMPERATURE TENSILE PROPERTY DATA OF 300 GRADE MARAGING

STEEL SPECIMENS AFTER AGING AT VARIOUS TEMPERATURES FOR 6 HOURS

Specimen Aging tempera-I Yield strength (0.2 percent)1 Ultimate strength I Elongation, Reduction

ture percent in area,

of 1 K psi 1 N/m2

1 1- N/m2 1 percent

psi

Static 800 700 260500 1. 80X109 267700 1. 84X109 9.6 46.1

Vib rate da 800 700 264 900 1. 83 270700 1. 87 9.6 47.1

Static 900 755 273 500 1. 89 279400 1. 93 9.6 52.7

Vibrateda 900 755 277000 1. 91 281900 1. 94 9.2 52.8

Static 1000 811 256700 1.77 268 900 1. 85 10.0 52.4

Vib rate da 1000 811 241400 1. 67 255900 1. 77 11.2 45.2

aNode of vibrated specimen at center of tensile specimen.

the tensile tests of the 300 grade maraging steel specimens are presented in table IV and

shown in figure 18. The solid line represents the statically aged specimens and the dot

ted lines the vibrated specimens. From figure 18 it can be seen that at 8000 and 9000 F

(700 and 755 K), the tensile strengths and yield strengths of the vibrated specimens were

higher than those of the static specimens by approximately 1 and 2 percent, respectively.

The effect of vibration on ductility, at 9000 F (755 K) was to decrease elongation from

9. 6 to 9. 2 percent. After aging at 10000 F (811 K) the tensile and yield strengths of the

vibrated specimen decreased by approximately 5 and 6 percent, respectively, below the

strengths of the statically aged specimen. This drop was due to overaging of the mater

ial. The elongation increased by approximately 1 percent but the reduction in area of

this specimen at fracture decreased from approximately 52 to 46 percent.

In general, changes in the tensile properties of specimens sugjected to ultrasonic

vibration were slight; but these changes were consistent with the results of hardness

tests presented previously.

Metallograph ic Study of Precipitate in L -605

Most of the precipitates formed during the previous aging tests were submicroscopic

in size and would have been visible only after overaging for very long times. L-605,

however, is an alloy which forms an observable precipitate near the grain boundaries in

relatively short aging times. Investigators have found that working this alloy before

aging can cause precipitates to nucleate and grow within the matrix (ref. 19). In the

present investigation it was desirable to see if ultrasonic vibration could similarly in

fluence the location of the precipitate.

26

1

1 . 7 5 L 5 m

mL“l

25 I I

7 I I -144 I I -1 800 900 1000 800 900 1000

Aging temperature, “F

I -1 !I 700 800 700 800

Aging temperature, K

Figure 18. - Room temperature tensile property data of 300 grade maraging steel after aging for 6 hours. Heat treating medium, sodium.

Figure 19(a) shows the microstructure of the cobalt-base alloy, L-605, in the as-received, solution heat-treated condition. Figure 19(b) shows the structure of the alloy as aged statically at 1600’ F (1144 K) for 10 hours. Most of the precipitate is observed in or near the grain boundaries. Figure 19(c) shows the structure of the alloy that was subjected to vibration of 1.4 mils (3. 6X10-2 mm) for 10 minutes at 1600’ F (1144 K), and then statically aged at 1600’ F (1144 K) for 10 hours. The precipitates were still seen to form at or near the grain boundaries. Figure 19(d) shows the structure of the L-605 that was vibrated at 0.8 mi l (2. oX10-2 mm) for 10 hours while it was being heat treated at 1600’ F (1144 K). Again, as in the case of the other two aged specimens, most of the precipitates formed at o r near the grain boundaries. Thus optical microscopy indicates that ultrasonic vibration did not induce nucleation s i tes for precipitates within the matrix of this alloy.

27

1.75

~ 15 27 ~ ~ ~

N 26 8 .c 0. ~ 25 ~

",

a;

'\ , , , \ \ \

\

2.00x109 29xl04 N

E Z .~

~ .c- 28 ~ ~ ~ ~ ..9! ..9! 27 'v; 'v; c: c: E ..9! E 2

~ ~ 26 , :::> 1.75 :::>

'tb ~ 24~------~------~ 25

12

11

110 c:- CD=-_=--_---U-/ ! ---cf c: o W

54

I 52

~~ 50

c:

~ 48

:::l "0

'" '" 46

7 800 900 1000 44800

Aging temperature, of

_-----.J 700 800 700

Aging temperature, K

I. /

/ /

a /,

\

" \ ", " "

Static

\ \ \ \ \ ,

\

\ \ o I

\ Vibrated at 25 000 HZ,' 2 mils (5. lxW-2 mm) \0

.---.l 900 1000

800

Figure 18. - Room temperature tensile property data of 300 grade maraging steel after aging for 6 hours. Heat treating medium, sodium.

Figure 19(a) shows the microstructure of the cobalt-base alloy, L-605, in the as

received, solution heat-treated condition. Figure 19(b) shows the structure of the alloy

as aged statically at 16000 F (1144 K) for 10 hours. Most of the precipitate is observed

in or near the grain boundaries. Figure 19( c) shows the structure of the alloy that was

subjected to vibration of 1. 4 mils (3. 6X10- 2 mm) for 10 minutes at 16000 F (1144 K), and

then statically aged at 16000 F (1144 K) for 10 hours. The precipitates were still seen

to form at or near the grain boundaries. Figure 19(d) shows the structure of the L-605

that was vibrated at 0.8 mil (2. OXlO-2 mm) for 10 hours while it was being heat treated

at 16000 F (1144 K). Again, as in the case of the other two aged specimens, most of the precipitates formed at or near the grain boundaries, Thus optical microscopy indi

cates that ultrasonic vibration did not induce nucleation sites for precipitates within the

matrix of this alloy.

27

~ 00

~~', ::.~

0' \ ' ~ .,' .. \ '} ":.'" t· \ . --\_ .. ,..,.

1\ '.

( l r)

I

\ ;'\ I 1\ \ I , . I

• \ \ ,\ v \\ \ ~ \

\

\ . '\ '-.' L~

;--

(a) L -605 as received.

-.~

'-..

~

r---

(c) Vibrated at 1.4 mils (3.6xl0-2 mm) for 10 minutes and statically aged for 10 hours at 16000 F (1]44 Kl.

(b) Aged statically at 16000 F (1144 K) for 10 hours.

(d) Vibrated at 0.8 mil (2.0xl0-2 mm) at 1600 F (1144 K) for 10 hours.

Figure 19. - Microstructure of L-605 after various aging treatments. Etchant, as received . (Electrolyt ic etched in 100 cc ono percent Hel + a few drops of H202; others etched in

30 cc boric ac id + 70 cc of 5 percent H2S04,) X250.

I

'.

·'

, ,

>1-.

} . J /

-

.' \ . .-----.. - .

,

\' ~ .

Ic) Vibrated at 1.4 mils 13.6xlO-2 mm) for 10 minutes and statically aged for 10 hours at 16000 F 11144 Kl.

Ib) Aged stat ically at 16000 F 11144 K) for 10 hours.

Id) Vibrated at 0.8 mil 12 .0xIO-2 mm) at 1600 F 11144 K) for 10 hours.

Figure 19. - Microstructure of L-605 after var ious aging treatments. Etchant, as rece ived. IElectrolytic etched in 100 cc 01"30 percent Hel + a few drops of H202; others etched in

30 cc boric ac id + 70 cc of 5 percent H2S04,) X250.

Effect of Heat-Treating Environme nt

The present investigation has shown a relatively smal l improvement in the hardening rate of alloys due to ultrasonic vibration as compared with some other investigations (refs. 5 and 7). Many previous investigators did not consider the heat added to the system by the ultrasonic vibration itself. If specimens become heated from vibration and no provision is made to ca r ry away the excess heat, diffusion will be accelerated. The resulting increases in hardening rates and changes in mechanical properties would then be due pr i marily to the temperature increase and not to some other aspect of the ultrasonic vibration. It is, therefore, not surprising that previous investigators who used liquid heat-treating baths (refs. 8 and 9) showed smaller increases in hardening ra tes and less diffusion effects than those who used powder o r gas environments (refs. 7 and 13).

The heating that can develop from vibration alone is shown in figure 20 which presents the resul ts of an infrared temperature scan of a specimen vibrated in air. No heat was supplied to the specimen except fo r the heat generated internally by the vibration of the specimen itself. The specimen was vibrated at approximately 2 mils (5. 1 ~ 1 0 - ~mm). Within 10 minutes the lower node of the specimen reached 310' F (428 K). After 30 minutes the lower node reached 395' F (475 K). This heating due to vibration would considerably influence resul ts of ultrasonic aging tests if s teps were not taken to remove the added heat, especially for mater ia ls such as aluminum that age harden at low temperatures.

To further demonstrate this heating effect, specimens of 300 grade maraging s teel were heat treated in an air furnace at 800' F (700 K). A static and vibrated specimen were subjected to the 800' F (700 K) temperature for 5 minutes. Only the lower half of the specimen was located in the furnace (see fig. 6). After the 5 minute aging tests, hardness measurements were made. The resul ts of the hardness measurements are shown in figure 21. From the figure, it can be seen that the vibrated specimen was unquestionably harder than the statically aged specimen, and a possible nodal effect was observed. The hardness of this vibrated specimen aged in air at 800' F (700 K)for 5 minutes compares closely with the hardness of the vibrated specimen aged in sodium at 1000° F (811 K)for 5 minutes (fig. ll(c)). These resul ts emphasize that the effects of ultrasonic vibration on aging can only be meaningfully evaluated if specimens are heat treated in a medium in which it can be assured that a fa i r ly constant specimen temperature (close to the nominal desired heat-treating temperature) can be maintained.

29

I'· j'

Effect of Heat-Treating Environment

The present investigation has shown a relatively small improvement in the hardening

rate of alloys due to ultrasonic vibration as compared with some other investigations (refs. 5 and 7). Many previous investigators did not consider the heat added to the system by the ultrasonic vibration itself. If specimens become heated from vibration and no pro

vision is made to carry away the excess heat, diffusion will be accelerated. The resulting increases in hardening rates and changes in mechanical properties would then be due primarily to the temperature increase and not to some other aspect of the ultrasonic vibra

tion. It is, therefore, not surprising that previous investigators who used liquid heattreating baths (refs. 8 and 9) showed smaller increases in hardening rates and less dif

fusion effects than those who used powder or gas environments (refs. 7 and 13).

The heating that can develop from vibration alone is shown in figure 20 which presents

the results of an infrared temperature scan of a specimen vibrated in air. No heat was supplied to the specimen except for the heat generated internally by the vibration of the specimen itself. The specimen was vibrated at apprOXimately 2 mils (5. 1xlO-2 mm). Within 10 minutes the lower node of the specimen reached 3100 F (428 K). After 30 min

utes the lower node reached 3950 F (475 K). This heating due to vibration would considerably influence results of ultrasonic aging tests if steps were not taken to remove the added heat, especially for materials such as aluminum that age harden at low tempera

tures. To further demonstrate this heating effect, specimens of 300 grade maraging steel

were heat treated in an air furnace at 8000 F (700 K). A static and vibrated specimen were subjected to the 8000 F (700 K) temperature for 5 minutes. Only the lower half of the

specimen was located in the furnace (see fig. 6). After the 5 minute aging tests, hard

ness measurements were made. The results of the hardness measurements are shown in figure 21. From the figure, it can be seen that the vibrated specimen was unquestionably

harder than the statically aged specimen, and a possible nodal effect was observed. The hardness of this vibrated specimen aged in air at 8000 F (700 K) for 5 minutes compares closely with the hardness of the vibrated specimen aged in sodium at 10000 F (811 K) for

5 minutes (fig. ll(c». These results emphasize that the effects of ultrasonic vibration on aging can only be meaningfully evaluated if specimens are heat treated in a medium in

which it can be assured that a fairly constant specimen temperature (close to the nominal desired heat-treating temperature) can be maintained.

29

L

--

Node Node

450 - 1 Time, m i n

400 -

a,

a,

a 300

400 250

200 I I I I I 0 1 2 3 4 5 6

Distance f r o m free end of specimen, in.

1 1 I I I II0 2 4 6 8 10 12 14


Figure 20. - Temperature prof i le of 300 grade maraging steel specimen vibrated in a i r at 25 000 hertz, 2 m i l s (5.1~10'2 mm). Temperature measured by i n f ra red pyrometer (lower l imi t : 200" F o r 366 K).

I Node N2 Node1 1 i

50

:&--,--\ \\ Ultrasonic v ibrat ion in a i r for \\ Y44 5 m i n at 800" F (700 K). 25 000 Hz. \

\\

Static aged in a i r for \ \

3032tI ~ I I I 0 1 2 3 4 5 6


- 1 I 1 1 I 1 I 0 2 4 6 8 10 12 14 16


Figure 21. - Comparison of hardness resu l t s between static aging and ul t rasonic v ibrat ion aging in a i r env i ronmen t for 300 grade maraging steel. Hardness at 0 time: RC 28.2 to 30.8.

30

500

"'" ~-

.2 450 E Q) Co

E Q)

I-

400

u

w 3<

.><: u 0 0::

~-

'" c 1: '" :r:

30

Node Al2 Node

450 ! Time, ~ ! min

~

~-

~ Q) Co

E Q)

I-

50

48

46

44

42

40

38

36

34

32

30 0

o

5 Distance from free end of specimen, in.

o 2 4 6 8 10 12 14 Distance from free end of specimen, cm

Figure 20. - Temperature profile of 300 grade maragi ng steel specimen vibrated in air at 25 000 hertz, 2 mils (5.1x10-2 mml. Temperature measured by infrared pyrometer (lower limit: 200

0 F

or 366 Kl.

Node

! Node

~ /---....._-

;---"'- --:/ Ultrasonic vibration in air for ""

5 min at 800 0 F (700 K), 25000 Hz, \ 2 mils (5.1x10-2 mm) \

\ \

\ "-

'" "-"-2 3 4 5


2 4 6 8 10 12 14 Distance from free end of specimen, cm

Figure 21. - Comparison of hardness results between static aging and ultrasonic vibration aging in air environment for 300 grade maraging steel. Hardness at 0 time: RC 28. 2 to 30.8.

6

I 16

6

CONCLUDING REMARKS

Energy developed by ultrasonic vibration can heat specimens above the nominal des i red temperature of the heat-treating medium. This, in effect, is equivalent to statically aging at a higher temperature. It is believed that certain beneficial effects previously attributed to ultrasonic vibration during aging may in fact be due to such heating.

Any attempts to fur ther evaluate the true effects of ultrasonic vibration on precipitation hardening of a mater ia l require the use of heat-treating media with good heat t ransfer properties so as to car ry away heat generated internally by vibration, and more closely maintain the desired specimen temperature.

In this study ultrasonic vibration was found to cause some increase in hardening rate for the materials studied. However, it is possible that this increase was due to unmeasured specimen temperature increases caused by vibration ( less than those observed in air) even though the high heat transfer liquid media were used.

SUMMARY OF RESULTS

The effect of ultrasonic vibration at a frequency of 25 000 hertz on the aging process was investigated over a range of temperatures for a 300 grade maraging steel, 17-4P H steel , A-286, Re& 41, and L-605, using a magnetostrictive vibratory apparatus. The following resul ts were obtained:

1. Ultrasonic vibration superimposed on alloys during aging increased the hardening rate for most of the alloys tested. For example, the vibrated 17-4PH steel specimen reached peak hardness in 15 minutes at 900' F (855 K) compared to 30 minutes for the statically aged specimen.

2. The maximum hardness obtained by ultrasonic vibration, although reached at an ear l ier time, did not exceed that obtainable by statically aging any of the alloys.

3. Room temperature tensile tes ts of ultrasonically vibrated 300 grade maraging s teel at 800' and 900' F (700 and 755 K) showed slight improvements in mechanical strength after 6 hours of aging. The tensile strength increased by about 1 percent and the yield strength increased by about 2 percent.

4. For all mater ia ls tested, variations in vibration s t r e s s had no consistent o r appreciable effect on the aging results.

5. Metallographic examination of precipitates in vibrated L-605 specimens showed no differences from the precipitate distribution in statically aged specimens.

6. An ultrasonically vibrated specimen of a 300 grade maraging s tee l aged in a n air furnace showed a considerable increase in the age hardening rate over that of a static

31

I

CONCLUDING REMARKS

Energy developed by ultrasonic vibration can heat specimens above the nominal de

sired temperature of the heat-treating medium. This, in effect, is equivalent to stati

cally aging at a higher temperature. It is believed that certain beneficial effects pre

viously attributed to ultrasonic vibration during aging may in fact be due to such heating.

Any attempts to further evaluate the true effects of ultrasonic vibration on precipita

tion hardening of a material require the use of heat-treating media with good heat trans

fer properties so as to carry away heat generated internally by vibration, and more

closely maintain the desired specimen temperature.

In this study ultrasonic vibration was found to cause some increase in hardening rate

for the materials studied. However, it is possible that this increase was due to unmeas

ured specimen temperature increases caused by vibration (less than those observed in

air) even though the high heat transfer liquid media were used.

SUMMARY OF RESULTS

The effect of ultrasonic vibration at a frequency of 25 000 hertz on the aging process

was investigated over a range of temperatures for a 300 grade maraging steel, 17 -4 PH

steel, A -286, Rene 41, and L-605, using a magnetostrictive vibratory apparatus. The

following results were obtained:

1. Ultrasonic vibration superimposed on alloys during aging increased the hardening

rate for most of the alloys tested. For example, the vibrated 17 -4 PH steel specimen

reached peak hardness in 15 minutes at 9000 F (855 K) compared to 30 minutes for

the statically aged specimen. 2. The maximum hardness obtained by ultrasonic vibration, although reached at an

earlier time, did not exceed that obtainable by statically aging any of the alloys.

3. Room temperature tensile tests of ultrasonically vibrated 300 grade maraging

steel at 8000 and 9000 F (700 and 755 K) showed slight improvements in mechanical

strength after 6 hours of aging. The tensile strength increased by about 1 percent and

the yield strength increased by about 2 percent.

4. For all materials tested, variations in vibration stress had no consistent or

appreciable effect on the aging results. 5. Metallographic examination of preCipitates in vibrated L-605 specimens showed

no differences from the preCipitate distribution in statically aged specimens.

6. An ultrasonically vibrated specimen of a 300 grade maraging steel aged in an

air furnace showed a considerable increase in the age hardening rate over that of a static

31

specimen aged in air at 800' F (700 K). This increase was due to the increased specimen temperature induced by the ultrasonic vibration.

Lewis Research Center, National Aeronautics and Space Administration,

Cleveland, Ohio, November 18, 1968, 129-03-03-03-22.

32

. ...

I I

specimen aged in air at 8000 F (700 K). This increase was due to the increased specimen temperature induced by the ultrasonic vibration.

Lewis Research Center,

32

National Aeronautics and Space Administration,

Cleveland, Ohio, November 18, 1968,

129 -03 -03 -03 -22.

APPENDIX A

CALCULATION OF WAVELENGTH OF 25 000 HERTZ

WAVE IN A 300 GRADE MARAGING STEEL

Wavelength = h = c/f

f frequency = 25 000 H z

velocity of sound in metal = d a E modulus of elasticity

g acceleration of gravity = 32.2 ft/sec 2 (980 cm/sec 2)

p density

From reference 25 - for 300 grade maraging steel:

E 27. %lo6 Ib/ia2 ( 1 . 8 9 5 ~ 1 0 ~ ~N/m2)

p 0. 289 (8. 0 g/cm3)

Then:

= 1 . 9 2 ~ 1 05 in./sec (4.88XlO5 cm/sec)

And:

= 7.68 in. (19. 5 cm)

33

c

APPENDIX A

CALCULATION OF WAVELENGTH OF 25 000 HERTZ

WAVE IN A 300 GRADE MARAGING STEEL

Wa velength = I\. = c/f

f frequency = 25 000 Hz

c velocity of sound in metal = VEg/p

E modulus of elasticity

g acceleration of gravity = 32.2 ft/sec 2 (980 cm/sec2)

p density

From reference 25 - for 300 grade maraging steel:

E 27.5><106 lb/in. 2 (1. 895X1011 N/m2)

p

Then:

And:

O. 289 lb/in. 3 (8. 0 g/ cm 3)

c= (2. 75X107

)(32. 2)(12) in./sec O. 289

= 1. 92X105 in./sec (4. 88X105 cm/sec)

5 I\. = £ = 1. 92X10

f 2.5><104

= 7.68 in. (19.5 cm)

33

APPENDIX B

EQUATIONS OF STRESS AND STRAIN BASED ON DISPLACEMENT FOR STRAIGHT BAR SPECIMENS SUBJECTED TO ULTRASONIC

VIBRATION AT 25 000 HERTZ

(A) Derivation of s t r e s s and strain relations:

From reference 22:

displacement at any point of straight bar:

2a f6 = 60

sin kx, where k = -= h c

6O maximum displacement

X distance from stationary node of specimen

A wavelength of sound in specimen material

f frequency = 25 000 H z

C velocity of sound in material

Boundary conditions:

(1)At point of maximum displacement, x = h / 4 , therefore

7r6 = 6 s i n -27r -x = 6 s i n - = 6 O A 4 O 2 O

(2) At point of minimum displacement, x = 0

6 = 6, sin o = 0

By definition: Strain (E) = a6/ax

27rx6 = 6 sin 0 h

34

APPENDIX B

EQUATIONS OF STRESS AND STRAIN BASED ON DISPLACEMENT

FOR STRAIGHT BAR SPECIMENS SUBJECTED TO ULTRASONIC

VIBRATION AT 25 000 HERTZ

(A) Derivation of stress and strain relations:

From reference 22:

displacement at any point of straight bar:

27T f 0:::: 00

sin kx, where k:::: -:::: -A c

00

maximum displacement

x distance from stationary node of specimen

A wavelength of sound in specimen material

f frequency = 25 000 Hz

c velocity of sound in material

34

Boundary conditions:

(1) At point of maximum displacement, x = A/4, therefore

2 /l o = 0 sin ~ = 0 sin!!.. = 0 o A 4 0 2 0

(2) At point of minimum displacement, x = 0

By definition: Strain (E) = ao/ax

0= 0 sin 0:::: 0 o

0= 0 sin 21TX o A

E = ~ = 0 27T cos 27TX ax 0 A A

~___--__

‘max occurs at point of minimum displacement, x = 0

271 27r= 60-(cos O), E m a x = 6 ‘max h O x

St re s s - maximum can be calculated f rom

where

CTmax maximum s t r e s s


‘max maximum strain f o r displacement

Then, substituting for cmaX:

CT = E 6 , - 27l max x

(B) Calculation of maximum stress for a 300 grade maraging s tee l straight bar specimen with a %mil (5. lX10-2-mm)(peak-to-peak) maximum displacement:

From reference 25:

E 27. 5X1O6 lb/in.2 (1.895X1Ol1 N/m2)

A 7.68 in. (19. 5 cm)

Displaceiment of 2 mils (5. 1X10q2”)(peak-to-peak) = 1mil (2. 5X10e2 mm) displacement from zero, then, f rom

= E G O -211 Omax x

-- (27. 5X1O6)(O. 001)(2)(a) 7.68

= 22 500 lb/in.2 (1.6X108 N/m2)

35

€max occurs at point of minimum displacement, x:::: 0

Emax 00 217 (cos 0), E :::: 0 217 A max 0 A

Stress - maximum can be calculated from

0" max E E max

where

maximum stress


maximum strain for displacement

Then, substituting for E max:

(B) Calculation of maximum stress for a 300 grade maraging steel straight bar specimen with a 2-mil (5. lXlO-2-mm)(peak-to-peak) maximum displacement:

From reference 25:

E 27. 5xI06 lb/in. 2 (1. 895x1011 N/m2)

A 7.68 in. (19.5 em)

Displacement of 2 mils (5. lXlO-2 mm)(peak-to-peak) :::: 1 mil (2. 5X10-2 mm) dis

placement from zero, then, from

== (27. 5X106)(0. 001)(2)(17)

7.68

== 22 500 lb/in. 2 (1. 6X108 N/m2)

35

REFERENCES

1. Kelley, A. ; and Nicholson, R. B. : Precipitation Hardening. Progress in Materials Science. Vol. 10, no. 3. Pe rgamonPress , 1963.

2. Lyman, Taylor, ed. : Heat Treating, Cleaning and Finishing. Vol. 2 of Metals Handbook. Eighth ed. , Am. SOC. Metals, 1964.

3. Mehl, R. F. , et al. : Precipitation from Solid Solution. American Society fo r Metals, 1959.

4. Thomas, G. ; and Nutting, J. : The Aging Characterist ics of Aluminum Alloys. J. Inst. Metals, vol. 88, 1959-1960, pp. 81-90.

5. Pogodina-Alekseeva, K. M. ; and Eskin, G. I. : Effect of Ultrasonic Vibrations on the Precipitation Hardening and Tempering of Some Alloys. Henry Brutcher Translat ionno. 4551, Jan. 1956.

6. Gorskiu, F. K. ; and Efremov, V. I. : Influence of Ultrasonic Vibrations on the Decomposition of Solid Solutions. Izvest. Akad. Nauk Beloruss. SSR, no. 3, 1953, pp. 155-164. Translation by H. E. Nowottny, Aluminum Labs. Ltd. , Banbury.

7. Ermakov, V. S. ; and Al'ftan, E. A. : Aging of Creep-Resisting Nickel-Base Alloy E1 437 B Accelerated by Ultrasonic Vibrations. Henry Brutcher Translation no. 4278, 1958.

8. Anon. : Investigation of the Effects of Ultrasonics on the Deformation Characterist ics of Metals. Wien Univ. , Austria, 1964. (Available f rom DDC as AD-600383. )

9. Mes'kin, V. S. ; and Al'ftan, E. A. : Investigation of the Effect of Ultrasonics on the Results of the Heat Treatment of Alloys. Phys. Metals Metallography, vol. 11, no. 4, 1961, pp. 53-62.

10. Lee, Won Kak: Ultrasonic Treatment of Alloys to Produce Dispersion Strengthening. M. S. Thesis, West Virginia Univ., 1966.

11. Fairbanks, H. V. : Effect of Insonation During the Precipitation-Hardening of Alloys. Sound, vol. 1, no. 6, Nov. -Dec. 1962, pp. 35-39.

12. Fairbanks, H. V. ; and Dewez, F. J . , Jr. : Effects of Acoustical Waves on the Annealing of Steels. J. Acoust. SOC. Am., vol. 29, no. 5, May 1957, pp. 588-592.

13. Rozanski, W. : Effect of Ultrasonic Vibrations upon Carburization of Steel. Henry Brutcher Translation no. 4860, 1958.

14. Pogodin-Alekseev, G. I. : Effect of Ultrasonic Vibrations on Diffusion in Steels and Alloys at Elevated Temperatures. Henry Brutcher Translation, no. 4247, 1958.

#-NASA-Langley, 1969 -32 E-4151

REFERENCES

1. Kelley, A.; and Nicholson, R. B.: Precipitation Hardening. Progress in Materials

Science. Vol. 10, no. 3. Pergamon Press, 1963.

2. Lyman, Taylor, ed.: Heat Treating, Cleaning and Finishing. Vol. 2 of Metals Hand

book. Eighth ed., Am. Soc. Metals, 1964.

3. Mehl, R. F., et al.: Precipitation from Solid Solution. American Society for Metals, 1959.

4. Thomas, G.; and Nutting, J.: The Aging Characteristics of Aluminum Alloys. J.

Inst. Metals, vol. 88, 1959 -1960, pp. 81-90.

5. Pogodina-Alekseeva, K. M.; and Eskin, G. 1.: Effect of Ultrasonic Vibrations on the

Precipitation Hardening and Tempering of Some Alloys. Henry Brutcher Transla

tion no. 4551, Jan. 1956.

6. Gorskiu, F. K.; and Efremov, V. 1.: Influence of Ultrasonic Vibrations on the Decomposition of Solid Solutions. Izvest. Akad. Nauk Beloruss. SSR, no. 3, 1953,

pp. 155-164. Translation by H. E. Nowottny, Aluminum Labs. Ltd., Banbury.

7. Ermakov, V. S.; and Al'ftan, E. A.: Aging of Creep-Resisting Nickel-Base Alloy

EI 437 B Accelerated by Ultrasonic Vibrations. Henry Brutcher Translation no.

4278, 1958.

8. Anon.: Investigation of the Effects of Ultrasonics on the Deformation Characteristics

of Metals. Wien Univ., Austria, 1964. (Available from DDC as AD-600383.)

9. Mes'kin, V. S.; and AI'ftan, E. A.: Investigation of the Effect of Ultrasonics on the

Results of the Heat Treatment of Alloys. Phys. Metals Metallography, vol. 11,

no. 4, 1961, pp. 53 -62.

10. Lee, Won Kak: Ultrasonic Treatment of Alloys to Produce Dispersion Strengthening.

M. S. Thesis, West Virginia Univ., 1966.

11. Fairbanks, H. V.: Effect of Insonation During the Precipitation-Hardening of Alloys.

Sound, vol. 1, no. 6, Nov. -Dec. 1962, pp. 35-39.

12. Fairbanks, H. V.; and Dewez, F. J., Jr.: Effects of Acoustical Waves on the An

nealing of Steels. J. Acoust. Soc. Am., vol. 29, no. 5, May 1957, pp. 588-592.

13. Rozanski, W.: Effect of Ultrasonic Vibrations upon Carburization of Steel.

Henry Brutcher Translation no. 4860, 1958.

14. Pogodin-Alekseev, G. 1.: Effect of Ultrasonic Vibrations on Diffusion in Steels and

Alloys at Elevated Temperatures. Henry Brutcher Translation, no. 4247, 1958.

I NASA-Langley, 1969 - 32 E -4151

NATIONAL AERONAUTICSAND SPACE ADMINISTRATION POSTAGE AND FEES PAID

D. C. 20546 NATIONAL AERONAUTICS A N DWASHINGTON, SPACE ADMINISTRATION OFFICIAL BUSINESS FIRST CLASS MAIL

POSTMASTER :

“The aeronautical and space activities of the United States shall be coizdzuted so as to contribute . . . t o the expansiofa of hz” knowledge of phenoinena in the atmosphere and space. T h e Administration shall provide for the widest pmcticable and appropriate dissenzinatioia of informziion concerning its activities and the res& thereof.”

-NATIONALAERONAUTICSAND SPACE ACT OF 1958 .... ..*

If Undeliverable (Section 158 Postal Manual) Do Not Return

NASA SCIENTIFIC AND TECHNICAL PUBLICATIONS

TECHNICAL REPORTS: Scientific and technical information considered important, complete, and a lasting contribution to existing knowledge.

TECHNICAL NOTES: Information less broad in scope but nevertheless of importance as a contribution to existing knowledge.

TECHNICAL MEMORANDUMS : Information receiving limited distribution because of preliminary data, security classification, or other reasons.

CONTRACTOR REPORTS: Scientific and technical information generated under a NASA contract or grant and considered an important contribution to existing knowledge.

TECHNICAL TRANSLATIONS: Information published in a foreign language considered to merit NASA distribution in English.

SPECIAL PUBLICATIONS: Information derived from or of value to NASA activities. Publications include conference proceedings, monographs, data compilations, handbooks, sourcebooks, and special bibliographies.

TECHNOLOGY UTILIZATION PUBLICATIONS: Information on technology used by NASA that may be of particular interest in commercial and other non-aerospace applications. Publications include Tech Briefs, Technology Utilization R~~~~~~and N ~ ~ ~ ~ , and Technology Surveys.

Details on the availability of these publications may be obtained from:

SCIENTIFIC AND TECHNICAL INFORMATION DIVISION

NATIONAL AERON AUT1C S AND SPACE ADM I NISTRATION. Washington, D.C. PO546

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

WASHINGTON, D. C. 20546

OFFICIAL BUSINESS

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FIRST CLASS MAIL

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POSTAGE AND FEES PAID NATIONAL AERONAUTICS AND

SPACE ADMINISTRATION

POSTMASTER: If Undeliverable (Section 158 Postal Manual) Do Not Return

"The aeronautical and space activities of the United States shall be conducted so as to contribute ... to the expansion of human knowledge of phenomena in the atmosphere and space. The Administration shall provide for the widest practicable a1~d appropriate dissemination of information concerning its activities and the reslllts thereof."

-NATIONAL AERONAUTICS AND SPACE ACT OF 1958 ... ', ......

i

NASA SCIENTIFIC AND TECHNICAL PUBLICATIONS

TECHNICAL REPORTS: Scientific and technical information considered important, complete, and a lasting contribution to existing knowledge.

TECHNICAL NOTES: Information less broad in scope but nevertheless of importance as a contribution to existing knowledge.

TECHNICAL MEMORANDUMS: Information receiving limited distribution because of preliminary data, security classification, or other reasons.

CONTRACTOR REPORTS: Scientific and technical information generated under a NASA contract or grant and considered an important contribution to existing knowledge.

TECHNICAL TRANSLATIONS: Information published in a foreign language considered to merit NASA distribution in English.

SPECIAL PUBLICATIONS: Information derived from or of value to NASA activities. Publications include conference proceedings, monographs, data compilations, handbooks, sourcebooks, and special bibliographies.

TECHNOLOGY UTILIZATION PUBLICATIONS: Information on technology used by NASA that may be of particular interest in commercial and other non-aerospace applications. Publications include Tech Briefs, Technology Utilization Reports and Notes, and Technology Surveys.

Details on the availability of these publications may be obtained from:

SCIENTIFIC AND TECHNICAL INFORMATION DIVISION

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION' Washington, D.C. 20546

NASA TECHNICAL NOTE · ERRATA NASA Technical Note D-5131 &,#a&? s-& EFFECT OF ULTRASONIC VIBRATION...

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Transcript of NASA TECHNICAL NOTE · ERRATA NASA Technical Note D-5131 &,#a&? s-& EFFECT OF ULTRASONIC VIBRATION...