Development of new testing method by centrifugal erosion tester at elevated temperature

Wear 258 (2005) 443–457

Development of new testing method by centrifugal erosion testerat elevated temperature

Noriyuki Hayashia,∗, Yoshimi Kagimotoa, Akira Notomia, Yasuyuki Takedaa, Koji Katob

a Nagasaki R&D Center, Mitsubishi Heavy Industries, 5-717-1 Fukahori-machi, Nagasaki 851-0392, Japanb Tohoku University, 01 Aramaki, Aoba-ku, Sendai 980-8579, Japan

Received 22 December 2003

Abstract

A new experimental apparatus which can evaluate particle erosion at high temperature is proposed. This apparatus has the followingcharacteristics:

• g speed of

• nder various

• equired for

preliminarye rosion ratesa amount of Cro .-F. Man,E©

K

1

ioputo

h

armave

es bymadeom-this

icles,aturerela-

ol-

0d

Particles are accelerated by centrifugal force of a rotating nozzle. So, particle impingement velocity is easily adjusted by rotatinthe nozzle.Nine test pieces can be supplied for one test, and temperature of the test pieces is controlled independently. So, erosion data utemperature conditions can be obtained in only one test.A test piece is heated by a cartridge heater directly. So temperature of test pieces rise in short duration, and electric power rerosion tests is lower than blast type high temperature erosion apparatuses.

To confirm that the new apparatus can obtain similar erosion data to the data obtained by conventional apparatuses, somexperiments have been performed. As a result, it was confirmed that the new centrifugal erosion apparatus can obtain similar end velocity exponents to the data obtained by conventional erosion apparatuses. The erosion rates of steels containing variousbtained by the new centrifugal erosion apparatus showed similar tendency to the data obtained by Levy and Man [A.V. Levy, Yrosion–corrosion mechanisms and rates in Fe–Cr steels, Wear 131 (1989) 51] using a blast type erosion apparatus.2004 Published by Elsevier B.V.

eywords:Particle erosion; High temperature; Centrifugal apparatus; New testing method

. Introduction

Particle erosion by ash or sand has often been experiencedn the coal fired power plants. In order to achieve the long lifef the power plants, it is very important to know the rate ofarticle erosion. The parts of power plants are often erodednder elevated temperature condition. So, in order to predict

he erosion rate of plants, it is necessary to develop the methodf particle erosion testing under high temperature conditions.

Table 1shows apparatuses for a particle erosion test atigh temperature used by research institutes around the world

∗ Corresponding author. Tel.: +81 95 834 2800; fax: +81 95 834 2385.E-mail address:noriyuki1 [email protected] (N. Hayashi).

[1–21]. There are three types of apparatuses, rotatingtype, blast type and wind tunnel type. Most institutes hused blast type apparatuses, especially blowing particla gas jet. Though the gas jet type apparatus is easilyby a combination of tubes, a particle feeder and a cpressor or a combustor, there are some problems inapparatus.

• As a test piece is heated by hot gas containing partone erosion test is carried out under only one tempercondition. So many tests are required to obtain thetionship between temperature and erosion.

• Adjustment of particle velocity is difficult because the vume of gas is changed by temperature.

043-1648/$ – see front matter © 2004 Published by Elsevier B.V.oi:10.1016/j.wear.2004.09.022

444 N. Hayashi et al. / Wear 258 (2005) 443–457

Table 1High temperature erosion apparatuses used by research institutes in the world

Institute Rotating arm type Blast type Wind tunnel type

Fluidized Not fluidized Gas jet Drop tube Centrifugal

University of California, Berkeley (USA)[1,2] © ©University of Cincinnati (USA)[3] ©University of Pittsburgh (USA)[4] ©Iowa State University (USA)[5] ©Kentucky Center for Energy Research Lab (USA)[6] ©Battelle (USA)[7] ©Metalspray International (USA)[8] ©University of Cambridge (UK)[9] ©Cranfield University (UK)[10] © © © ©University of Manchester Institute of Science and

Technology (UK)[11]©

University of Nottingham (UK)[12] © ©University of Surrey (UK)[13] ©University of Cape Town (South Africa)[14] ©Hiroshima University (Japan)[15] ©Kanazawa Institute of Technology (Japan)[16] ©Sumitomo Metal Industries (Japan)[17] ©Kawasaki Heavy Industries (Japan)[18,19] © © ©Ishikawajima-Harima Heavy Industries (Japan)[20] © ©Mitsubishi Heavy Industries (Japan)[21] ©© denotes the apparatus used in the institute shown in the left column.

• Large amounts of electric power or fuel are required tomake high temperature gas for erosion tests.

To perform efficient erosion tests at high temperatures, a newtest apparatus based on a centrifugal erosion tester proposedby Soderberg et al.[22] has been designed. The new appa-ratus can obtain the erosion data under different temperatureconditions in one test and thus decrease power consumptionfor erosion tests. In this paper the structure of the new testapparatus and procedure of high temperature erosion tests aredescribed. And some data obtained by the new erosion testapparatus are introduced in order to show validity of the newtesting method.

2. Structure of the new high temperature erosionapparatus

Pictures of the new high temperature erosion apparatusare shown inFig. 1, and the structure of the new apparatusare shown inFigs. 2 and 3. A rotating nozzle with holes isrotated by a motor in high speed. Particles are supplied in thecenter of the rotating nozzle and fly out from the holes bycentrifugal force. The particles erode the test pieces standingaround the nozzle. The apparatus produced in this study hast

• Sincepen-ndi-

• tureby a

Fig. 1. Pictures of the centrifugal high temperature erosion apparatus: (a)appearance of whole apparatus and (b) appearance of rotating nozzle andtest pieces.

he following characteristics.

Cartridge heaters are inserted into each test piece.temperature of the cartridge heaters is controlled indedently, data of erosion under different temperature cotions can be obtained in only one test.By use of small cartridge heaters, the high temperaerosion tests require smaller electric power than tests

N. Hayashi et al. / Wear 258 (2005) 443–457 445

Fig. 2. Main structure of the centrifugal high temperature erosion apparatus:(a) principal of centrifugal erosion apparatus and (b) structure of the mainpart of apparatus.

conventional apparatus. As one heater heats only one testpiece, the temperature of the test piece rises quickly.

• By use of cylindrical test pieces, it is possible to eval-uate the erosion rate at different particle impingement

Table 2Specifications of the centrifugal high temperature erosion apparatus

Type Blast, centrifugal type

Heating apparatus Cartridge heater (temperature ofeach test piece is controlledindependently)

Reachable temperature 800◦C (surface of the test piece)Number of test piece Nine test pieces per one testMaximum rotating velocity of

nozzle (maximum velocity ofnozzle edge)

10000 rpm (100 m/s)

Atmosphere ExchangeableMaximum particle supplying rate About 30 g/min

angles by measurement of the shape of only one testpiece.

• The main part of apparatus is installed in a tightly-closedchamber and the pressure in the chamber is controlled bya vacuum pump. And erosion tests in corrosive gas or inertgas can be carried out.

Specifications of the centrifugal high temperature erosion ap-paratus are shown inTable 2. The nozzle can be rotated until10,000 rpm (velocity at circumference of the nozzle is up to100 m/s) and test pieces can be heated up to 800◦C. The testconditions of this apparatus cover the eroding conditions inboilers of coal fired power plants.

3. Procedure to set up erosion test conditions

In this section the measurement of particle velocity, par-ticle impingement angle, weight of particles impinging on atest piece and temperature of a test piece in the new centrifu-gal erosion apparatus are shown.

ntrifuga
Fig. 3. Whole structure of the ce l high temperature erosion apparatus.


Fig. 4. Velocity components of the particle flying out from the rotating nozzle.

3.1. Particle impingement velocity

As shown inFig. 4, particles flying out from the rotatingnozzle have various components of velocity. In order to ob-tain the particle velocity flying out from the nozzle,V0, it isrequired to know the leaping angleκ. In the apparatus pro-duced in this study, the holes in the rotating nozzle declineas shown inFig. 4. The angle of declivity of the hole is 30◦.So particles fly in a slight downward angle. The downwardangle of the flying particle� is determined by the ratio ofthe particle velocity in a rotating directionVr to the particlevelocity in a radius direction of the nozzleVd. So if we canobtain the relationship between the distance from the centerof rotating nozzle and the height of flying particles, it is pos-sible to obtain the leaping angleκ and the downward angleγ geometrically. Procedure to obtainκ andγ are detailed inAppendix A.

In order to obtain the relationship between the distancefrom the center of rotating nozzle and the height of flyingparticles, particle catchers shown inFig. 5 were prepared.The particle catcher consisted of 12 pipes piled up vertically.

Three particle catchers were mounted around the rotatingnozzle at the different distance from the rotating nozzle asshown inFig. 6, and weight of particles caught by each pipewas measured. The distribution of the weight of particleswas evaluated, and the height where the most particles werecaught was obtained in each particle catcher. If particles flyin the downward angle, the height where the largest amountsof particles are caught becomes lower as the distance fromthe rotating nozzle increases. So, the relationship between thedistance from the rotating nozzle to the particle catcher andthe height where the largest amounts of particles are caughtis obtained, and the leaping angleκ and the downward angleγ are calculated.

Fig. 7 shows the relationship between the height of thepipe and the weight of particles caught by each pipe of theparticle catchers. As the distribution of the weight of parti-cles was similar to a Gaussian distribution, the height wherethe largest amounts of particles were caught was obtained by

Fig. 5. Schematic of the particle catcher.
Fig. 6. Position of the particle catchers.


Fig. 7. Relationship between the height of the pipe and the amount of theparticle caught by the particle catcher. (particle: SiO2 (average diameter:23�m), rotating velocity of the nozzle: 9600 rpm): (a) distance betweenparticle catcher and the center of nozzle = 110 mm, (b) distance betweenparticle catcher and the center of nozzle = 120 mm and (c) distance betweenparticle catcher and the center of nozzle = 135 mm.

approximation of the distribution of the particles’ weight to aGaussian distribution.Fig. 8shows the relationship betweenthe distance from the center of the rotating nozzle to the par-ticle catchers and the height where the largest amounts of

Fig. 8. Relationship between the distance from the center of the nozzle tothe particle catcher and the height where the largest amount of the particleswere caught.

Fig. 9. Schematic of the ideal and a real trace of particles and a position ofthe hole throwing particles in a horizontal plane.

particles were caught. As mentioned above, the height wherethe largest amounts of particles were caught became lower byincreasing the distance between the rotating nozzle and theparticle catcher. FromFig. 8, it was obtained that the down-ward angleγ was 6◦ by the geometrical examination shownin Appendix A.

The leaping angleκ and the downward angleγ changewhen material, shape or size of particles change. So if par-ticles prepared for an erosion test change, the leaping angleκ and the downward angleγ should be measured before anerosion test.

If the leaping angleκ and the downward angleγ are mea-sured, we can obtain the particle velocity flying out from therotating nozzleV0 by the following equation:

V0 = 2πrω

60 cosκ cosγ(1)

wherer is the radius of the rotating nozzle,ω the rotatingvelocity of the nozzle (rpm).

Though it is possible to obtain the initial velocity of parti-cles flying out from the nozzle, velocity of particles decreasesby resistance of gas when particles impinge on test pieces. Inorder to evaluate the speed reduction of particles, we visual-ized a trajectory of particles and compared it with the idealtrajectory of particles when resistance of gas is not consid-e

ingt isp stantvi

L

V nea nd,t g

red.Fig. 9shows positions of particles and the hole throw

he particles beforet seconds in a horizontal plane. If itossible to ignore resistance of gas, particles fly at conelocity. So, the flight distance of the particleL with no gass obtained by the following equation:

= Vht = V0t cosγ (2)

h is the initial velocity of the particle in a horizontal plandt is the flight duration from the nozzle. On the other ha

he rotating angleθ duringt seconds is shown in the followin


Fig. 10. Schematic of a photographing system for the trace of particles.

equation:

θ = 2πωt

60(3)

From Eqs.(2) and (3)we can obtain the relationship betweenthe rotating angle of the nozzleθ and the flight distance ofthe particleL

L = 60V0 cosγθ

2πω(4)

From Eqs.(1) and (4), it is possible to express the relationshipbetweenL andθ by the simple equation

L = rθ

cosκ(5)

From Eq.(5), the trajectory of flying particles can be obtained.If the particles are subjected to gas resistance, the trajec-

tory of flying particles will differ from the trajectory withno gas resistance as shown inFig. 9. In order to obtain realtrajectories, the particles are photographed.Fig. 10shows aschematic of the photographing system used. Since the parti-cle velocity was very high, pictures of particles were taken byuse of a high-speed electric flash (flash duration is 1/10,000 s).And by synchronizing the flash with rotation of the nozzle, wecould take pictures of the rotating nozzle throwing particles.

Fig. 11shows a photograph of the particle trajectory. Ther edbs dif-f o gasr o in-c

wase

Fig. 11. Photograph of the real trace of the flying particles.

Fig. 12. Relationship between flight duration and difference from the idealtrace to the real trace of particles.

Fig. 12, the coefficientA in Eq. (B.4) was obtained.Fig. 13shows the relationship between the distance from the centerof the rotating nozzle and the particle velocity obtained byEq. (B.9). FromFig. 13the particle velocity decreases withthe distance from the nozzle. The hatching area inFig. 13shows the region where wear depths of test pieces are mea-

Fig. 13. Relationship between the distance from the center of rotating nozzleand the flying velocity of the particles.

eal trajectory is a little different from the trajectory obtainy Eq. (5) due to the influence of gas resistance.Fig. 12hows the relationship between the flight duration anderence between trajectories with gas resistance and nesistance, which indicates that the difference tends trease with flight duration.

The speed reduction of particles by gas resistancevaluated by the procedure shown inAppendix B. From


Fig. 14. Schematic of horizontal layout of a test piece and the rotating nozzle.

sured, and it was found that change of the particle velocityis low. So, the average velocity in the region is used as theparticle impingement velocity. (It is supposed that the changeof the erosion rate by the change of particle velocity in theregion where wear depth is measured is about 10% or less,so this effect was ignored in this study.)

The calibration tests shown in this section were carried outat room temperature and atmospheric pressure because mosterosion tests are carried out under atmospheric pressure andlow gas temperature condition (<100◦C). However, densityof the gas influences gas resistance to the particles and theparticle velocity. So, when the erosion tests are carried outin very high or low gas pressure or under very high gas tem-perature condition, the calibration tests should be carried outunder the erosion test conditions.

3.2. Particle impingement angle

If the leaping angleκ and the downward angleγ are ob-tained, it is possible to obtain a particle impingement angleon test pieces geometrically. The horizontal layout of a testpiece and a rotating nozzle is schematically shown inFig. 14.The particle impingement angle in a horizontal plane,α′, isexpressed in the following equations (seeAppendix C):

α3π

(r′2 + r 2 − r 2

)

α

w stp andt

Fig. 15. Relationship between the particle impingement angleα andα′.

Because particles fly in a slight downward angle, the par-ticle impingement angleα is slight smaller thanα′. Fig. 15shows the relationship betweenα andα′. FromFig. 15 theparticle impingement angleα is given in the following equa-tion:

α = cos−1

( √1/tan2α′ + tan2γ√

1/tan2α′ + tan2γ + 1

)(7)

By using cylindrical test pieces we can obtain the relationshipbetween the particle impingement angle and the erosion rateby measurement of the shape of one test piece.

3.3. Weight of impinging particles on a test piece

Amount of the particles impinging on the test piece in-fluences the eroded volume. In this section the procedure toobtain the weight of the impinging particles par unit area onthe surface of the test piece by using the data of the particlecatching test shown in Section3.1 is described.

Fig. 16shows a model used for calculation of the amountof impinging particles on a test piece. Particles supplied tothe center of the rotating nozzle are assumed to be uniformlydispersed around the rotating nozzle. As shown inFig. 16,the amount of particles passing the area with unit width in a

F thet

′ =2

− cos−1 t c

2r′rt

−sin−1{ r

r′ sin(κ + π

2

)}whenδ > 0 (6.1)

′ = π

2− sin−1

{ r

r′ sin(κ + π

2

)}−sin−1

(− rc

r′ sinδ)

whenδ < 0 (6.2)

herer′ =√

rt2 + rc

2 − 2rtrc cosδ, rt the radius of the teiece,rc the distance between the center of the nozzle

he center of the test piece.
ig. 16. Calculating model on the amount of the impinging particle on
est piece.


horizontal direction,w′, is expressed by the following equa-tion:

w′ = sT

2πrd sinκ(8)

wheresis the particle supplying rate,T the duration of particlesupply,rd the distance from the center of the rotating nozzle.

On the other hand, as mentioned in Section3.1, the ver-tical distribution of flying particle is similar to a Gaussiandistribution. It is possible to obtain the peak value of theamount of particles from the result of particle catching tests.The peak amount of particles passing unit area,w, is shownby using the peak amount of particles obtained from the dataof particle catching tests,c, in the following equation:

w = csT

2πrd sinκ(9)

From Eq.(9), the amount of impinging particles on a test pieceis the function of the leaping angle,κ, distance between thecenter of the rotating nozzle and a test piece,rd, supplyingrate of particles,s, and test duration,T. It is possible to controlthe supplying rate of particles from 0 to 30 g/min by changingrotating speed of a screw feeder which supplies particles tothe center of the rotating nozzle.

3

r areh ticle ist

ridgeh r, andt feed-b

dom-i ateri f then d the

Fig. 18. Measuring procedure of wear depth by a roundness measuring ap-paratus.

test piece, thermal conductivity of the test piece and so on.And because a thermocouple in each cartridge heater is in adifferent position, the surface temperature of each test pieceis slightly different even if temperature measured by a ther-mocouple in each cartridge heater is equal. So we directlymeasured the surface temperature of the test piece by fixinga thermo couple by a thin stainless steel plate on the surfaceof the test piece as shown inFig. 17. And the relationship be-tween the temperature of the cartridge heater and the surfacetemperature of the test piece is obtained on each test piecebefore erosion tests.

4. Measurement of erosion rates of test pieces

In order to obtain the relationship between wear depth andparticle impingement angle, three-dimensional distributionof wear depth on a test piece is required because particles flyin a slight downward angle. Three-dimensional profile of thetest piece was measured by a roundness measuring apparatusshown inFig. 18 [23].

of the

.4. Temperature of a test piece

Though the gas and particles supplied to the chambeeated by a heater, the temperature of the gas and par

oo low to raise the temperature of test pieces.The temperature of a test piece is controlled by a cart

eater. There is a thermocouple in each cartridge heatehe temperature of each cartridge heater is adjusted byack controller independently.

On the other hand, the temperature of a test piece isnated by not only the temperature of the cartridge henserted into the test piece but also the rotating speed oozzle, the clearance between the cartridge heater an

Fig. 17. Measuring instrument
surface temperature of a test piece.


Fig. 19. Example of three-dimensional profile of a test piece measured by aroundness measuring apparatus.

Fig. 19 shows the example of three-dimensional profileof an eroded test piece measured by the roundness measur-ing apparatus. All profile data measured by the roundnessmeasuring apparatus are saved in a personal computer, anda program to calculate the three-dimensional distribution ofwear depth from the profiling data of a test piece was devel-oped.Fig. 20shows the principle using to obtain wear depthfrom the profile of a test piece. Profiles are measured beforeand after erosion testing. And the relationship between a po-sition and wear depth is obtained by comparison between theunworn profile and the worn profile. Particle impingement an-gles at each position are calculated by the procedure shownin Section3.2, and the relationship between a position andwear depth is converted to the relationship between particleimpingement angle and wear depth.

On the other hand, the vertical position where wear depthbecome maximum corresponds to the height where the mostparticles impinge. So the wear depth,d, is converted into theerosion rate,E, which is eroded volume per unit weight ofparticles by the following equation:

E = d

w sinα(10)

α is obtained by Eq.(7), andw is obtained by Eq.(9).

In general, the erosion rate is defined as the weight or vol-ume loss of material per unit weight of impinging particles.However, it is not suitable to use weight loss for evaluationof the erosion under high temperature condition. This is be-cause oxidation of the uneroded part of the test sample canlead to gain in weight if the oxide in coherent on the metalsurface. So, in this study the eroded volume per unit weightof impinging particles is used as the erosion rate.

5. Test results of preliminary tests by the centrifugalhigh temperature erosion apparatus

5.1. Quantitative comparison between data obtained bythe new apparatus and a conventional apparatus

To confirm that the new apparatus can obtain quantita-tively equivalent data to conventional apparatuses, erosiontests by different apparatuses have been carried out undersame test conditions.

Two apparatuses, one is the new centrifugal erosion appa-ratus and another is a blast type erosion apparatus, shown inFig. 21 [24], were used with the conditions shown inTable 3.Because the blast type erosion apparatus cannot perform testsunder high temperature conditions, erosion data were ob-t so o, thee usw ratus.

ses,s fugala ainedbs h ap-p ilar, soi eacha

con-fi moste tusesb

TE erenta

P

P

P

PMT

Fig. 20. Model to obtain wear depth of a test piece.

ained at room. As mentioned in Section5.3, the erosion ratef stainless steel hardly depend on the temperature. Srosion rate obtained at 150◦C in the centrifugal apparatas compared with that obtained by the blast type appaFig. 22shows erosion rates obtained by two apparatu

howing that the erosion rate obtained by the new centripparatus is almost equivalent to the erosion rate obty the conventional blast type erosion apparatus.Fig. 23hows eroded surfaces of test pieces supplied to eacaratus. The appearance of each eroded surface is sim

t is expected that the mode of erosion is the same inpparatus.

As a result of erosion tests using two apparatuses, it isrmed that the new centrifugal apparatus can obtain alquivalent data to conventional blast type erosion apparay adopting the calibrations shown in Sections3 and 4.

able 3rosion test conditions for quantitative comparison between diffpparatuses

Centrifugalapparatus

Blast apparatus

article SiO2 (average diameter: 23�m,angular shape)

article impingementvelocity

80 m/s

article impingementangle

– 30◦

article supplying rate 30 g/min 16 g/minaterial of test piece 304SS

emperature of testpiece

200◦C RT


Fig. 21. Blast type erosion apparatus used to compare erosion data with that obtained by the new centrifugal apparatus[24].

Fig. 22. Comparison of erosion rates obtained by two different apparatuses(particle: SiO2 (average diameter: 23�m), material of test piece: 304SS,particle impingement velocity: 80m/s, particle impingement angle: 30◦).

5.2. Influence of the particle impingement velocity andthe particle flux rate on the erosion rate

It has been reported that the erosion rate is proportionalto the second or third power of impingement velocity[25]and independent of the flux rate of impinging particleswhen the influence of oxidation or corrosion is not severe[26]. So the influence of the particle impingement veloc-ity and the flux rate of impinging particles on the erosionrate was examined by the new centrifugal apparatus, usedwith the conditions shown inTable 4. The influence of thevelocity and the flux rate has been examined under vari-ous temperature conditions. Stainless steel, which is often

Table 4Test conditions to examine the influence of particle impingement velocityand particle flux rate on erosion rate

Particle SiO2 (average diameter: 75�m,angular shape)

Particle impingement velocity 20, 33 m/sParticle supplying rate 4, 33 g/minMaterial of test piece 304SSTemperature of test piece 400, 500, 600, 700◦C

Fig. 23. Eroded surface of test pieces from: (a) the centrifugal apparatus and(b) the blast type apparatus observed by SEM (particle: SiO2 (average diam-eter: 23�m), material of test piece: 304SS, particle impingement velocity:80 m/s, particle impingement angle: 30◦).


Fig. 24. Relationship between temperature of the test piece and erosion rate(particle: SiO2 (average diameter: 75�m), material of test piece: 304SS,particle impingement angle: 30◦).

used as corrosion-resistant material, has been chosen as testmaterial.

Fig. 24shows the relationship between temperature of thetest piece and erosion rate. FromFig. 24it was found that theerosion rate slightly increased with increases in temperatureof the test piece. The erosion rate increases by increasingthe particle impingement velocity, and the erosion rate underthe low flux rate condition is slightly larger than that underhigh flux rate condition. It is supposed that the influence ofoxidation more strongly appeared under the low flux ratecondition, so the erosion rate was more strongly influencedby temperature.

Fig. 25 shows the relationship between the particle im-pingement velocity and the erosion rate. InFig. 25the dottedline whose slope is 2.5 is shown. FromFig. 25the velocityexponent of erosion rates is about 2.5. It is concluded that thedata obtained by the new centrifugal erosion apparatus showssimilar tendency of the data reported by other researchers onthe influence of particle impingement velocity and flux rateof particles.

5.3. Influence of the temperature of test pieces on theerosion rate

In order to examine the influence of temperature of testpieces on the erosion rate, erosion tests using five kinds of

F osionr S,p

Table 5Test conditions to examine the influence of temperature and content of Crin test piece on erosion rate of steels

(a) Test conditionsParticle SiO2 (average diameter: 23�m,

angular shape)Particle impingement velocity 80 m/sParticle supplying rate 30 g/minMaterial of test piece 1.25Cr steel, 2.25Cr steel,

9Cr–1Mo steel, 304SS, 310SSTemperature of test piece 400, 500, 600, 700◦C

Material of test piece Content (%)

C Si Mn Fe Cr Ni Mo V

(b) Material of test piece1.25Cr steel 0.2 0.2 0.5 97.4 1.0 0.1 0.5 –2.25Cr steel 0.1 0.4 0.5 95.8 2.3 – 0.9 –9Cr–1Mo steel 0.1 0.4 0.4 89.3 8.5 0.1 0.9 0.2304SS 0.1 0.3 1.1 72.3 18.1 8.1 – –310SS 0.1 1.0 1.5 53.2 24.2 20.1 – –

steels containing various amount of Cr were carried out andthe results of the tests were compared with the data obtainedby other researcher using a conventional blast type erosionapparatus.

Sundararajan and Roy using a blast type erosion apparatus,have reported that acceleration of the erosion rate of steelsby rise of temperature appears notably when content of Cr insteels is less than 10%[27]. Table 5shows the test conditionsand chemical composition of steels tested.

F ariousa -m -a(d) temperature of the test piece: 700◦C.

ig. 25. Relationship between particle impingement velocity and erate (particle: SiO2 (average diameter: 75�m), material of test piece: 304Sarticle impingement angle: 30◦).

ig. 26. Influence of temperature on erosion rate of steels containing vmount of Cr (particle: SiO2 (average diameter: 23�m), particle impingeent velocity: 80 m/s): (a) temperature of the test piece: 400◦C, (b) temperture of the test piece: 500◦C, (c) temperature of the test piece: 600◦C and


Fig. 27. Relationship between content of Cr in steels and erosion rate: (a)data obtained by the new centrifugal apparatus (particle: SiO2 (average diam-eter: 23�m), particle impingement velocity: 80 m/s, particle impingementangle: 30◦, temperature of test piece: 700◦C) and (b) data obtained by blasttype apparatus reported by Levy and Man[28].

Fig. 26shows the influence of the temperature on the ero-sion rate of test pieces. Though the erosion rates of eachsteel are almost equal under 500◦C, erosion rate of low al-loy steels increases drastically when the temperature of testpieces reaches 700◦C. Fig. 27(a) shows the relationship be-tween Cr content and the erosion rate at 700◦C obtained bythe new centrifugal apparatus. It is clear that content of Cr inthe steels influences the erosion rates of the test pieces. Thesdata are similar to the data reported by Levy and Man shownin Fig. 27(b) [28].

This confirms that the centrifugal high temperature ero-sion apparatus can obtain the results similar to those obtainedby a blast type high temperature erosion apparatus.

6. Conclusions

In order to evaluate erosion rates of various materials underhigh temperature condition, the new testing method using acentrifugal high temperature erosion apparatus has been pro-posed. In this paper procedure to measure particle impinge-ment velocity, particle impingement angle, temperature oftest pieces and erosion rates are described in detail.

From results of erosion tests by the new testing methodthe following conclusions have been obtained.

• The erosion rate obtained by the centrifugal erosion appa-ratus is almost equivalent to the erosion rate obtained by aconventional blast type erosion apparatus.

• The dependence of erosion rates on the particle impinge-ment velocity and the flux rate of particles obtained by thecentrifugal erosion apparatus shows similar tendency todata obtained by other apparatus.

• Data from the centrifugal erosion apparatus show that theerosion rate of steels containing more than 10 wt.% Cris almost independent of temperature up to 700◦C. Thisresult agrees with the data obtained by Levy et al. using ablast type erosion apparatus.

One of the characteristics of the new centrifugal erosionapparatus is that more data can be obtained in shorter durationand smaller energy consumption than a conventional hightemperature erosion apparatus. This characteristic helps theevaluation of high temperature erosion in small laboratories.

Acknowledgement

Authors wish to thank Mr. Yasuo Kawamoto of RyokenT

Ap

G

t

e

ech Co. for his support in the experiments.

ppendix A. Procedure to obtain the leaping angle ofarticle κ and the downward angle of particleγ

Fig. A1shows the definition of the lengtha, b, c, r andrp.eometrically we can obtain the following equations:

anκ = a

b(A.1)

Fig. A1. Definition of lengtha, b, c, r andrp.


rp =√

(r + a)2 + b2 (A.2)

On the other hand, as the angle of declivity of the hole is 30◦,the following equation is obtained:

a = c

tan 30◦=

√3c (A.3)

By putting Eqs.(A.1) and (A.3)into Eq.(A.2), the followingequation is obtained:

rp =

√√√√(r +√

3c)2 +

(√3c

tanκ

)2

(A.4)

If the relationship between distance from the center of thenozzlerp and heightc is obtained by experiments using par-ticle catchers, tanκ will be obtained from Eq.(A.4).

The downward angleγ is expressed by use of the lengthshown inFig. A1 in the following equation:

γ = tan−1(

c√a2 + b2

)(A.5)

By putting Eqs.(A.1) and (A.3)into Eq. (A.5), the fol-lowing equation is obtained:

γ = tan−1

(a√

3√)

Sa

Ap

esis-t

F

w t,V

fl beo

m

B

x

w er

thep ces

Fig. B1. Relationship betweenx, r andrp.

of particles with gas resistance and no gas resistance,�x, isshown by the following equation:

�x = V0t − AV0(1 − e−t/A) (B.4)

From the relationship betweent and�x shown inFig. 12,coefficientA is obtained. By puttingA into Eq. (B.3), theflight distance of particles is obtained as a function of theflight duration. On the other hand, the particle velocityVp isshown in the following equation:

Vp = V0 e−t/A (B.5)

From Eqs.(B.3) and (B.5), the following equation is obtained:

Vp = V0

(1 − x

AV0

)(B.6)

From the relationship between the flight distancex and thedistance from the center of nozzle to the particlerp (seeFig. B1), the following equation is obtained:

r2p = x2 + r2 − 2xr cos

(κ + π

2

)(B.7)

From Eq.(B.7), x is expressed by the following equation:

x =√

r2 sin2κ + r2p − r2 − r sinκ (B.8)

Putting Eq.(B.8) into Eq.(B.6), Vp is expressed in the fol-l

V

S nt rticlev ncef

Ai

ngleo

a2 + α2/tan2κ

= tan−1

(1√

3(1+ 1/tan2κ)

)(A.6)

o we can obtain the downward angleγ from the leapingngleκ.

ppendix B. Evaluation of speed reduction of aarticle by resistance of gas

It is assumed that a particle moving in a gas suffers rance which is proportional to the velocity of the particle

= −CVp (B.1)

hereF is the resistance by the gas,C the resistant coefficienp the velocity of the particle.

If we definem as the mass of the particle andx as theight distance of the particle, the following equation canbtained:

x = −Cx (B.2)

y solving Eq.(B.2) the following solution is obtained:

= AV0(1 − e−t/A) (B.3)

hereA=m/C,V0 the particle velocity at flying out from thotating nozzle (Eq.(1)), t the flight duration.

If the resistance by gas is negligible, the velocity ofarticle is constant (V0). So the difference between the tra

owing equation:

p = V0

1 −

√r2 sin2κ + r2

p − r2 − r sinκ

AV0

(B.9)

o if we can obtain the coefficientA by comparison betweehe ideal trace and the real trace of particles, the paelocity Vp can be obtained as the function of the distarom the center of the nozzle to the particlerp.

ppendix C. Procedure to obtain a particlempingement angle in a horizontal plane

We consider two conditions, one is that the center af test pieceδ (seeFig. 14) is positive and another is thatδ is


Fig. C1. Definition ofr’ , α1 andα2 (δ > 0).

negative.

(1) δ > 0

At first we define the lengthr′ and the anglesα1 andα2 asshown inFig. C1. By use ofα1 and�2, a particle impinge-ment angle in a horizontal planeα′ is given in the followingequation:

α′ = 32π − (α1 + α2) (C.1)

The relationship betweenr′, rc and rt is expressed in thefollowing equation:

r2c = r′2 + r2

t − 2r′rt cosα1 (C.2)

On the other hand, the relationship betweenr′ and r is ex-pressed in the following equation:

r′

sin(κ + π/2)= r

sinα2(C.3)

From Eqs.(C.2) and (C.3), α1 andα2 are obtained:

α1 = cos−1

(r′2 + rt

2 − rc2

2r′rt

)(C.4)

α2 = sin−1{ r

r′ sin(κ + π

2

)}(C.5)

P .

(

W fα ane

α′ is given in the following equation:

α′ = π

2− (α3 + α4) (C.6)

The relationship betweenr andr′ is expressed in the followingequation:

r

sinα3= r′

sin(κ + /π/2)(C.7)

On the other hand,rc andr′ have the following relationship:

r′ sinα4 = −rc sinδ (C.8)

From Eqs.(C.7) and (C.8), α3 andα4 are obtained

α3 = sin−1{ r

r′ sin(κ + π

2

)}(C.9)

α4 = sin−1(− rc

r′ sinδ)

(C.10)

Putting Eqs.(C.9) and (C.10)into(C.6), Eq.(6.2)is obtained.By the way,r′ is expressed by the angleδ in the following

equation:

r′2 = r2t + r2

c − 2rtrc cosδ (C.11)

From Eq.(C.11), r′ is shown by the following equation:

r

R

n of

rialf the, pp.

n of

andation

ior ofn and

lowaper

ffect-dingsietyuis

ncybed

velrna-

, pp.

utting Eqs.(C.4) and (C.5)into (C.1), Eq.(6.1)is obtained

2) δ > 0

e define the anglesα3 andα4 as shown inFig. C2. By use o3 andα4 a particle impingement angle in a horizontal pl

Fig. C2. Definition ofα3 andα4 (δ < 0).

′ =√

r2t + r2

c − 2rtrc cosδ (C.12)

eferences

[1] A.V. Levy, J. Yan, J. Patterson, Elevated temperature erosiosteels, Wear 108 (1986) 43–60.

[2] Y. Liu, A.V. Levy, The influence of test parameters on matewastage in a fluidized bed wear test rig, in: Proceedings oInternational Conference on Wear Materials, vol. 1991, 199119–26.

[3] N. Gat, W. Tabakoff, Some effects of temperature on the erosiometals, Wear 50 (1978) 85–94.

[4] S.L. Chang, F.S. Pettit, N. Birks, Interaction between erosionhigh-temperature corrosion of metals: the erosion-affected oxidregime, Oxidat. Met. 34 (1990) 23–45.

[5] J. Zhou, S. Bahadur, High-temperature erosion-corrosion behavstainless steels, in: Proceedings of the Conference on CorrosioParticle Erosion at High Temperature, 1989, pp. 315–333.

[6] R.G. Corey, V.K. Sethi, Erosion–corrosion synergistics in theerosion regime, in: Proceedings of the NACE—Corrosion’86, PNo. 114, NACE, 1986, pp. 1–11.

[7] I.G. Wright, V. Nagarajan, R.B. Herchenroeder, Some factors aing solid particle erosion/corrosion, in: K. Natesan (Ed.), Proceeof the Symposium at the Fall Meeting of the Metallurgical Socof AIME on Corrosion–Erosion Behavior of Materials, St. LoMissouri, October 17–18, 1978, 1980, pp. 268–312.

[8] S.W. Lee, B.Q. Wang, Effect of particle-tube collision frequeon material wastage on in-bed tubes in the bubbling fluidizedcombustor, Wear 184 (1995) 223–229.

[9] M.J. Entwisle, I.M. Hutchings, J.A. Little, Evaluation of a nofluidized bed erosion rig, in: Proceedings of the Seventh Intetional Conference on Erosion by Liquid and Solid Impact, 198771.1–71.10.


[10] J.R. Nicholls, Laboratory studies of erosion-corrosion processes un-der oxidizing and oxidizing/sulphidising conditions, Mater. HighTemp. 14 (1997) 289–306.

[11] F.H. Stott, M.P. Jordan, S. Lekatos, M.M. Stack, G.C. Wood,The erosion–corrosion of alloys under oxidizing–sulphidizingconditions at high temperature, Wear 186/187 (1995) 291–298.

[12] P.J. Shayler, K.H. Yee, Erosion of AISI 303 steel by fine (about5�m and about 50�m) ash particle, Wear 98 (1984) 127–140.

[13] A.L. Ham, J.A. Yeomans, J.F. Watts, Elevated temperature solidparticle erosion of silicon carbide continuous fiber reinforced cal-cium aluminosilicate glass–ceramic matrix composite, Wear 203–204(1997) 387–392.

[14] M. Suckling, C. Allen, The design of an apparatus to test wear ofboiler tube, Wear 186/187 (1995) 266–272.

[15] M. Matsumura, Y. Oka, K. Baba, Development of sand erosion testerunder high temperature and corrosive condition, in: Proceedings ofthe Fushoku-Boshoku’88, 1988, pp. 198–201 (in Japanese).

[16] T. Nakagawa, M. Tennichi, Relation between erosion and mate-rial characteristics, in: Proceedings of the 30th Meeting of JSMEHokuriku-Shinetsu Branch, vol. 937, No. 1, 1993, pp. 85–88 (inJapanese).

[17] Y. Shida, H. Fujikawa, Particle erosion behaviour of boilertube materials at elevated temperature, Wear 103 (1985) 281–296.

[18] K. Hasegawa, S. Okazaki, H. Murase, S. Matsuda, T. Someya, K.Kikusawa, S. Ito, T. Takada, Experimental study on erosion-wearcharacteristics of in-bed tubes in fluidized bed boiler, Kawasaki JukoGiho 88 (1985) 1–9 (in Japanese).

[19] M. Takamori, K. Hasegawa, S. Okazaki, M. Kiyoshige, T. Mori,Wear of alloy steels by impact of powder at high temperature, Trans.JSME (A) 60 (1994) 1898–1901 (in Japanese).

[20] F. Umemura, S. Matsukura, T. Kawamoto, Influence of particle andtemperature on erosion of metallic materials, Ishikawajima-HarimaJuko Giho 25 (1985) 286–290 (in Japanese).

[21] N. Hayashi, Y. Kagimoto, H. Akiyama, et al., Adhered film formationon steel surface by impingement of hard particles, in: D. Dowson(Ed.), The Third Body Concept, Elsevier, 1996, pp. 605–613.

[22] S. Soderberg, S. Hogmark, U. Engman, H. Swahn, Erosion classifi-cation of materials using a centrifugal erosion tester, Tribol. Int. 14(1981) 333–343.

[23] N. Hayashi, K. Hasezaki, S. Takaki, High-temperature erosion ratesof Fe–Cr–C alloys produced by mechanical alloying and sinteringprocess, Wear 242 (2000) 54–59.

[24] Y. Kagimoto, S. Matsumoto, T. Noda, M. Noda, M. Etsu, N. Shida,Experimental study on the relationship between erosion wear rateand particle impact velocity measured by LDV, in: Proceedings ofthe Seventh International Conference on Erosion by Liquid and SolidImpact, 1987, pp. 69.1–69.8.

[25] A.V. Levy, The platelet mechanism of erosion of ductile metals,Wear 108 (1986) 1–21.

[26] P.M. Rogers, T.E. Howes, I.M. Hutchings, J.A. Little, Wastage oflow alloy steels in a fluidized bed environment, Wear 186/187 (1995)306–315.

[27] G. Sundararajan, M. Roy, Solid particle erosion behavior of metallicmaterials at room temperature and elevated temperature, Tribol. Int.30 (1997) 339–359.

[28] A.V. Levy, Y.-F. Man, Erosion–corrosion mechanisms and rates inFe–Cr steels, Wear 131 (1989) 39–51.

Development of new testing method by centrifugal erosion tester at elevated temperature

Documents

Transcript of Development of new testing method by centrifugal erosion tester at elevated temperature