Roller burnishing project report

i

SURFACE CHARACTERISTICS OF EN24 BY

ROLLER BURNISHING

A PROJECT REPORT

Submitted by

RAJIV.K 211611114077

SASIRAM KUMAR.S.P 211611114090

in partial fulfilment for the award of the degree

of

BACHELOR OF ENGINEERING

IN

MECHANICAL ENGINEERING

RAJALAKSHMI COLLEGE OF ENGINEERING, THANDALAM

ANNA UNIVERSITY: CHENNAI 600025

APRIL 2015

ii

ANNA UNIVERSITY: CHENNAI 600 025

BONAFIDE CERTIFICATE

Certified that this project report “SURFACE CHARACTERISTICS OF

EN24 BY ROLLER BURNISHING” is the bonafide work of “RAJIV.K

(211611114077) AND SASIRAM KUMAR.S.P (211611114090)”who carried

out the project work under my supervision.

SIGNATURE SIGNATURE

Dr.S.P.SRINIVASAN Mr.E.SHANKAR

HEAD OF THE DEPARTMENT, SUPERVISOR

ASSISTANT PROFESSOR,

Department of Mechanical Engineering, Department of Mechanical Engineering,

Rajalakshmi Engineering College, Rajalakshmi Engineering College,

Thandalam, Chennai-602105 Thandalam, Chennai-602105.

Submitted for the Anna University examination held on…………….

INTERNAL EXAMINER EXTERNAL EXAMINER

iii

ACKNOWLEDGEMENT

We would like to thank our Chairman Mr.S.Meganathan and our

Chairperson Dr. Mrs.Thangam Meganathan for providing us an institution,

which is an exemplary center for learning.

We express our sincere thanks to our Principal Dr.G.Thanigaiarasu and

Dr.S.N.Murugesan (Vice Principal) for providing adequate infrastructure and

congenical environment.

We would like to thank Dr.S.P.Srinivasan, HOD and for his timely

guidance and invaluable support.

We would like to thank our project guide Mr.E.Shankar, Assistant

Professor, Mechanical Department for his continuous support and the knowledge

shared and the practical exposure in completing our project.

We also extend our sincere thanks to all the staff members of mechanical

department who gave us valuable suggestions for doing this project.

Last but not the least, we would like to thank the Almighty for giving us

all the strength and courage in doing this project. We are grateful to our beloved

Parents, without whom we would not have been, as we are today. We also thank

all our friends and well wisher who have always been with us.

iv

TABLE OF CONTENTS

CHAPTER

NO.

TITLE PAGE

NO.

ABSTRACT vi

LIST OF TABLES vii

LIST OF FIGURES viii

1 INTRODUCTION 1

1.1 BURNISHING 1

1.2 BALL BURNISHING 2

1.2.1 In manufacturing 2

1.3 ROLLER BURNISHING 3

1.3.1 Advantages 5

1.3.2 Applications 5

2 LITERATURE SURVEY 7

3 MATERIAL SELECTION 9

3.1 TUNGSTEN CARBIDE 9

3.1.1 Properties of tungsten carbide 9

3.2 WORKPIECE 10

3.2.1 EN 24 10

4 MACHINING 13

4.1 INPUT PARAMETERS 14

4.2 KEROSENE 14

4.3 OUTPUT PARAMETERS 15

4.4 HARDNESS 16

4.4.1 Rockwell hardness 16

4.5 ROUGHNESS 17

v

4.6 TABULATION 19

5 COATING 22

5.1 INTRODUCTION 22

5.2 TITANIUM ALUMINIUM NITRIDE (TiAlN)

COATING

24


5.3 PHYSICAL VAPOUR DEPOSITION(PVD) 25

5.3.1 Process of PVD 26

5.4 CATHODIC ARC DEPOSITION 27

5.4.1 Process 27


5.5 TABULATION 30

6 RESULTS AND DISCUSSIONS 33

7 COST ESTIMATION 38

REFERENCE 39

vi

ABSTRACT

This project describes burnishing process as an alternate finishing process

for EN24 grade steel. Burnishing is a chipless machining process in which a

rotating roller or ball is pressed against metal piece. It is a cold working process

and involves plastic deformation under cold working conditions by pressing hard

against the workpiece. The burnishing process help to improve surface roughness

and hardness. The advantage of the burnishing process is non-chip removal to

attain surface finish. The effect of various input parameters such as spindle speed,

lubricants and number of passes on the output parameters such as surface

roughness and surface hardness is studied. The tool is coated with Titanium

Aluminium Nitride (TiAlN) and the machining is carried out with the coated

roller with the same input parameters. The effect of coating on the output

parameters are then calculated. From the results, it is noted that the coated

burnishing tool results in a better surface finish.

vii

LIST OF TABLES

TABLE NO. TITLE PAGE NO.

3.1

International Steel Specification Comparison

(EN24)

11

3.2 EN24 Steel Mechanical Properties 12

4.1 Hardness and surface roughness of EN24 after

machining without coating the tool

19

5.1 Hardness and surface roughness of EN24 after

machining with TiAlN coated roller

30

7.1 Cost Estimation 38

viii

LIST OF FIGURES

FIG. NO. TITLE PAGE NO.

1.1 Surface profile - Before Burnishing 1

1.2 Surface profile - After Burnishing 1

1.3 Roller Burnishing 4

1.4 Burnishing Tool 5

4.1 Experimental Setup 13

4.2 Rockwell Hardness C Test 17

4.3 Rockwell Hardness Tester 17

4.4 Surface Roughness Tester 18

4.5 Effect of speed on roughness – before coating 20

4.6 Effect of speed on hardness – before coating 21

5.1 Coated Roller 29

5.2 Effect of speed on hardness – after coating 31

5.3 Effect of speed on roughness – after coating 32

6.1 Comparing hardness values before and after

coating the tool – without lubricant

33

6.2 Comparing hardness values before and after

coating the tool – with lubricant

34

6.3 Comparing surface roughness values before and

after coating the tool – without lubricant

35

6.4 Comparing surface roughness values before and

after coating the tool – with lubricant

36

1

CHAPTER 1

INTRODUCTION

1.1 BURNISHING

Burnishing is the plastic deformation of a surface due to sliding contact

with another object. Visually, burnishing smears the texture of a rough surface

and makes it shinier. Burnishing may occur on any sliding surface if the contact

stress locally exceeds the yield strength of the material. As the pressure exceeds

the yield point of the work piece material, the surface is plastically deformed by

cold-flowing of subsurface material. Roller burnishing is a metal displacement

process. Microscopic “peaks” on the machined surface are caused to cold follow

into the “valleys”, creating a plateau- like profile in which sharpness is reduced

or eliminated in the contact plane. The main advantage of burnishing process over

other processes is the chip less removal to attain the required surface finish

thereby saving material and increasing hardness.

FIG 1.1 SURFACE PROFLIE FIG 1.2 SURFACE PROFILE

(BEFORE BURNISHING) (AFTER BURNISHING)

2

The most common forms of burnishing process are:

1. Ball burnishing

2. Roller burnishing

1.2 BALL BURNISHING

It is a metal-displacement process, in which, an oversize ball is pushed

through an undersized hole. The ball expands the hole by displacing an amount

of material equal to the interference fit.

The ball burnishing devices recommended for die and moulds are based on

a hydrostatic spring, whose main advantage is that ball load is constant during the

process and related to the maximum pressure survey by an external pump. This is

a high-pressure pump with low flow, taking coolant up from the machine-tool

reservoir. A movement of the ball head up to 10 mm is possible without changes

in the force value. The key element is a ceramic ball diameter 6 mm; this material

exhibits low adhesion to steels and cast irons, the constitutive materials of moulds

and dies.

Ball burnishing creates a shiny, highly reflective surface. This process is

typically done using steel media or a media with a high bulk density that yields a

cost effective, attractive finish. Ball burnishing finishes are very popular.

Typically they will have a shiny, high lustre appearance. In addition to polishing

the surface of the processed parts ball burnishing also creates a peening effect,

increasing the surface density which can improve the corrosion resistance of the

finished components.

3

1.2.1 BALL BURNISHING IN MANUFACTURING

A burnishing tool rubs against the work piece and plastically deforms its

surface. The work piece may be at ambient temperature, or heated to reduce the

forces and wear on the tool. The tool is usually hardened and coated with special

materials to increase its life.

Ball burnishing, Burnishing Balls, or ballizing, is a replacement for other

bore finishing operations such as grinding, honing, or polishing. A ballizing tool

consists of one or more over-sized balls that are pushed through a hole. The tool

is similar to a broach, but instead of cutting away material, it plows it out of the

way.

Burnishing Balls also occurs to some extent in machining processes. In

turning, burnishing occurs if the cutting tool is not sharp, if a large negative rake

angle is used, if a very small depth of cut is used, or if the work piece material is

gummy. As a cutting tool wears, it becomes blunter and the burnishing effect

becomes more pronounced. In grinding, since the abrasive grains are randomly

oriented and some are not sharp, there is always some amount of burnishing. This

is one reason the grinding is less efficient and generates more heat than turning.

1.3 ROLLER BURNISHING

In roller burnishing process, the tool is in the form of a cylinder which is

moved on the work piece at a constant feed rate. The single roller carbide

burnishing tool is used for burnishing varying outer diameters with a single tool.

With one tool different diameters can be burnished to achieve low surface finish.

Also there is no limitation on the burnishing length for this design tool. Highly

finished superior grade carbide rollers are used with precision assembly

arrangement. This tool is highly suitable in batch production where the diameter

of the job varies from one work order to another work order. Job Order quantity

4

as low as one number can also be processed with this tool so this tool is highly

useful in job shop production.

FIG 1.3 ROLLER BURNSIHING

Roller burnishing does not requires a skilled operators. This process can be

effectively used in many field such as aerospace industries, automobile

manufacturing sector, production of machine tool, hydraulic cylinders, etc.

Even though polishing occurs as a result of burnishing, polishing in itself not

burnishing. The distinction is that polishing will produce a smooth finish, but not

a hard one. Polishing is more about removing material to obtain the desired finish

where as one. Polishing is more about removing material to obtain the desired

finish whereas burnishing will generally result in a deeper polish than is possible

with polishing alone. A hardness or roughness test would be necessary to

distinguish between them.

5

FIG 1.4 BURNISHING TOOL

1.3.1 ADVANTAGES

1. Mirror like surface finish

2. Dimensional Consistency / Repeatability

3. Increase in Surface Hardness

4. Reduces the Reworks and Rejections.

1.3.2 APPLICATIONS

Roller burnishing was first applied in American industry in the 1930s to

improve the fatigue life or railroad car axles and rotating machinery shafts. By

the 1960s, roller burnishing was more widely applied, particularly in

the automotive industry, as other process advantages were recognized. The

primary benefits, related to part quality, are as follows: Accurate size control

(tolerances within 0.0005 inch or better, depending on

material types and other variables). ¸ Surface finished (typically between 1 to 10

micro inches Ra). ¸ Surface hardness (by as much as 5 to 10 % or more). Roller

6

burnishing has long been used on a wide variety of automotive and heavy

equipment components (construction, agricultural, mining and son on), including

piston and connecting rod bores, brake system components, transmission parts

and torque converter bubs. Burnishing tools are also now widely applied in non-

automotive applications for a variety of benefits; to produce better and longer

lasting seal surfaces; to improve wear life; to reduce friction and noise levels in

running parts; and to enhance cosmetic appearance.

Examples include valves, pistons of hydraulic or pneumatic cylinders, lawn

and garden equipment components, shafts for pumps, shafts running in

bushings, bearing bores, and plumbing fixtures.

7

CHAPTER 2

LITERATURE SURVEY

R. L. Murthy et al (1981) discussed the types and working methods of

burnishing process. Burnishing is considered as a cold working process which can

be used to improve surface characteristics. Surface roughness and hardness plays

an important role in many areas and is factor of great importance for the

functioning of machined parts.

Shankar et al (2008) discusses the effect of various input parameters on the

surface roughness and surface hardness of Al-(SiC)p metal matrix composites by

roller burnishing process and found out that when kerosene with graphite power

comparing with other lubricants such as soluble oil, mineral oil and kerosene

yields better results on surface roughness and surface hardness

A.M. Hassan et al (2000) explained the effects of ball and roller burnishing

on the surface roughness and hardness of some non- ferrous metals. It was

suggested by many investigators that an improvement in wear resistance can be

achieved by burnishing process.

U M Shirsat and B B Ahuja (2004) performed burnishing operation on

aluminium and found out that about 60-70% improvement in surface finish is

obtained and at different values of force ,speed and feed ,Kerosene gave best

surface finish.

A.A. Ibrahim et.al.(2009) performed burnishing on mild steel.

Experimental and fuzzy results showed that an increase in burnishing speed up to

1.5 m/s leads to a decrease in the burnished out-of-roundness whereas the increase

in burnishing speed more than 1.5m/sec results in an increase in out-of-roundness

8

L.N. Lo´pez de Lacalle et.al (2005) performed burnishing on heat treated

and tempered steel and found out that maximum pressure of 30 MPa leads to

highest quality improvement for the materials of 35-55 HRC.

Dabeer P.S. and Purohit G.K.(2010) used aluminium workpiece. Optimum

surface finish was obtained at 425rpm speed,7 mm ball diameter,70 N force and

2 tool passes.

S. Thamizhmnaii (2008) et al presented the surface roughness and hardness

investigations on titanium alloy using a roller burnishing tool.

M. H. El- Axir (2008) presented his experimental investigations in to roller

burnishing and the parameters which will affect the surface roughness values on

the specimens.

9

CHAPTER 3

MATERIALS

3.1 TUNGSTEN CARBIDE

The roller used is of tungsten carbide material. Tungsten carbide (WC) is a

chemical compound (specifically, a carbide) containing equal parts

of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine

grey powder, but it can be pressed and formed into shapes for use in industrial

machinery, cutting tools, abrasives, armour-piercing rounds, other tools and

instruments, and jewellery. Tungsten carbide is characterised by its high strength,

toughness and hardness. Its name derives from the Swedish for tung (heavy) and

sten (stone) and it is mainly used in the form of cemented tungsten carbides.

Cemented carbides (also known as hard metals) are made by 'cementing' grains

of tungsten carbide into a binder matrix of cobalt or/and nickel.

Tungsten carbide as a material can vary in carbide grain size (0.2 – 50

microns) and by binder contents (up to 30%), as well as by the addition of other

carbides. By varying the grain size of the tungsten carbide and the binder content

in the matrix, engineers have access to a class of materials whose properties can

be tailored to a variety of engineering applications. This includes high-tech tools,

wear parts and tools for the construction, mining and oil and gas sector.

Tungsten carbide products typically have a high resistance to wear and can

be used at high temperatures, allowing tungsten carbide's combined hardness and

toughness to significantly outperform its steel product equivalents.

3.1.1 PROPERTIES OF TUNGSTEN CARBIDE

1. Strength - Tungsten carbide has very high strength for a material so hard

and rigid. Compressive strength is higher than virtually all melted and cast or

forged metals and alloys.

10

2. Rigidity - Tungsten carbide compositions range from two to three times

as rigid as steel and four to six times as rigid as cast iron and brass. High resistance

to deformation and deflection is very valuable in those many applications where

a combination of minimum deflection and good ultimate strength merits first

consideration. These include spindles for precision grinding and rolls for strip or

sheet metal.

3. Impact Resistant - For such a hard material with very high rigidity, the

impact resistance is high. It is in the range of hardened tool steels of lower

hardness and compressive strength.

4. Heat and oxidation resistance - Tungsten-base carbides perform well up

to about 1000°F in oxidizing atmospheres and to 1500°F in non-oxidizing

atmospheres.

5. Wear-Resistance - Tungsten carbide wears up to 100 times longer than

steel in conditions including abrasion, erosion and galling. Wear resistance of

tungsten carbide is better than that of wear-resistance tool steels.

6. Melting and boiling points - Tungsten carbide has a high melting point

at 2,870 °C (5,200 °F), a boiling point of 6,000 °C (10,830 °F) when under a

pressure equivalent to 1 standard atmosphere (100 kPa).

3.2 WORKPIECE

3.2.1 EN24

EN24 is usually supplied in the T condition with a tensile strength of

850/1000 N/mm2.

EN24 steel is a popular grade of through-hardening alloy steel due to its

excellent machinability in the "T" condition. EN24 is used in components such as

11

gears, shafts, studs and bolts, its hardness is in the range 248/302 HB. EN24 can

be further surface-hardened to create components with enhanced wear resistance

by induction or nitriding processing.

Table 3.1 : International Steel Specification Comparison (EN24)

BS 970:1955 EN24

BS 970:1991 817M40T

German / DIN 34CrNiMo6

French AFNOR 35NCD6

American AISI /

SAE

4340

German

Werkstoff No.

1.6582

European

Standard

EN10277-5

817M40T - EN24T steel is a high tensile alloy steel renowned for its wear

resistance properties and also where high strength properties are required. EN24

is used in components subject to high stress and with a large cross section. This

can include aircraft, automotive and general engineering applications for example

propeller or gear shafts, connecting rods, aircraft landing gear components.

817M40 (EN24) Specification:

Chemical composition of EN24:

Carbon - 0.36-0.44%

Silicon - 0.10-0.35%

Manganese - 0.45-0.70%

12

Sulphur - 0.040 Max

Phosphorus - 0.035 Max

Chromium - 1.00-1.40%

Molybdenum - 0.20-0.35%

Nickel - 1.30-1.70%

Table 3.2 : 817M40T / EN24T Steel Mechanical Properties

Size

mm

Tensile

Strength

N/mm²

Yield

Stress

N/mm²

Elongation Impact

Izod J

Impact

KCV J

Hardness

HRC

63 to 150 850-1000 680 Min 13% 54 50 24-32

150 to 250 850-1000 654 Min 13% 40 35 24-32

Hardening EN24: Heat uniformly to 823/850°C until heated through. Quench in

oil.

Tempering: Heat uniformly and thoroughly at the selected tempering

temperature, up to 660°C and hold at heat for two hours per inch of total thickness.

Stress Relieving: Heat slowly to 650-670°C, soak well. Cool the EN24 tool in a

furnace or in air.

13

CHAPTER 4

MACHINING

The machining process is done on an automatic centre lathe. The input

parameters chosen to be studied are:

1. Speed

2. Number of passes

3. Lubricant

FIG 4.1 EXPERIMENTAL SETUP

14

The work piece is rotated at varying speeds of 200rpm, 300rpm, and 500rpm.

This is because the recommended value of speed is 530rpm. The machining is

done at 1, 2 and 3 number of passes for each speed. In addition, kerosene is used

as a lubricant and the effect of lubricant on the machinihg process is studied.

4.1 INPUT PARAMETERS

SPEED: N1 = 200rpm

N2 = 300rpm

N3 = 500rpm

NO. OF PASSES = 1, 2, 3

LUBRICANT USED: Kerosene

4.2 KEROSENE

Kerosene is a combustible hydrocarbon liquid widely used as a fuel, in

industry, and in households. Its name is derived from Greek keros meaning wax,

and was registered as a trademark by Abraham Gesner in 1854 before evolving

into a genericized trademark. It is sometimes spelled kerosene in scientific and

industrial usage. The term "kerosene" is common in much of India, Canada, the

United States, Australia and New Zealand. Kerosene is usually called paraffin in

the UK, Ireland, Southeast Asia and South Africa. A more viscous paraffin oil is

used as a laxative. A waxy solid extracted from petroleum is called paraffin wax.

15

In industry:

As a petroleum product miscible with many industrial liquids, kerosene can

be used as both a solvent, able to remove other petroleum products, such as chain

grease, and as a lubricant, with less risk of combustion when compared to using

gasoline. It can also be used as a cooling agent in metal production and treatment

(oxygen-free conditions).

In the petroleum industry, kerosene is often used as a synthetic hydrocarbon for

corrosion experiments to simulate crude oil in field conditions.

Kerosene has been found to be an effective pesticide.

4.3 OUTPUT PARAMETERS

The output parameters measured are:

1. Surface hardness – HRC scale

2. Surface roughness – Ra scale

The feed rate and depth of cut were kept constant at 180mm/m and 0.5mm

respectively.

4.4 HARDNESS

Hardness is defined as the ability of a material to resist plastic deformation,

usually by indentation. The term may also refer to resistance to:

1. Scratching

2. Abrasion

3. Cutting

4. Penetration

It is the property of a metal which gives it the ability to resist being

permanently deformed when a load is applied. Therefore, hardness is important

from an engineering standpoint because resistance to wear by either friction or

16

erosion by various elements generally increases with hardness. The greater the

hardness of the metal, the greater resistance it has to deformation.

The common indentation hardness tests are:

1. Rockwell hardness

2. Brinell hardness

3. Vickers hardness

4.4.1 ROCKWELL HARDNESS

The Rockwell scale is a hardness scale based on indentation hardness of a

material. The Rockwell test determines the hardness by measuring the depth of

penetration of an indenter under a large load compared to the penetration made

by a preload. There are different scales, denoted by a single letter, that use

different loads or indenters.

HRC scale is taken. Load - 150 kgf. Indenter - 120° diamond cone

FIG 4.2 ROCKWELL HARDNESS C TEST

17

FIG 4.3 ROCKWELL HARDNESS TESTER

4.5 ROUGHNESS

Surface roughness, often shortened to roughness, is a component of surface

texture. It is quantified by the deviations in the direction of the normal vector of

a real surface from its ideal form. If these deviations are large, the surface is

rough; if they are small, the surface is smooth. Roughness plays an important role

in determining how a real object will interact with its environment. Rough

surfaces usually wear more quickly and have higher friction coefficients than

smooth surfaces. Roughness is often a good predictor of the performance of a

mechanical component, since irregularities in the surface may form nucleation

sites for cracks or corrosion.

The roughness is taken in the Ra scale. Ra is the arithmetic mean of all

values in a particular area.

18

FIG 4.4 SURFACE ROUGHNESS TESTER

A portable surface roughness tester able to operate independently of mains

power and make measurements on almost any part of a workpiece of practically

any size. The 2.4-inch colour graphic back-lit LCD provides excellent readability

and an intuitive display that is easy to use. Operation is by keys on the front of

the unit and under the sliding cover. Up to 10 measurement conditions and one

measured profile can be stored in the internal memory. An optional memory card

can be used as an extended memory to store large quantities of measured surface

profiles and setup conditions. Access to each feature can be protected to prevent

unintended operation. An alarm warns when the stylus should be checked for

wear. Complies with the applicable international standards concerning definition

and calculation of the values of surface roughness parameters. In addition to

calculation results, sectional calculation results and assessed profiles, bearing

curves, and amplitude distribution curves can be displayed.

19

4.6 TABULATION

BEFORE COATING:

Table 4.1: Hardness and surface roughness of EN24 after

machining with uncoated tool

PASS SPEED

(rpm)

WITHOUT LUBRICANT WITH LUBRICANT

HARDNESS

(HRC)

ROUGHNESS

(Ra)

HARDNESS

(HRC)

ROUGHNESS

(Ra)

1

200 33 1.55 32 1.68

300 32 0.73 33 1.38

500 32 0.91 33 1.2

2

200 32 1.54 31 0.85

300 32 0.72 34 1.2

500 33 0.83 32 1

3

200 30 1.51 32 1.1

300 33 0.71 33 0.85

500 31 1.10 32 1.12

The results are drawn as a graph.

20

FIG 4.5 Effect of speed on roughness

LEGEND:

Straight lines – without lubricant

Dotted lines – with lubricant

From the graph, it can be inferred that the surface roughness of the

workpiece decreases as the number of passes and the speed increases. The surface

roughness increases when kerosene is used as lubricant. For the lowest surface

roughness, it is recommended to machine at 300rpm since the lowest roughness

is obtained at this speed – 0.71µm for 3 passes, 0.72 µm for 2 passes and 0.73 µm

for 1 pass.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 100 200 300 400 500 600

No. of pass - 1

No. of pass - 2

No. of pass - 3

No. of pass -1

No. of pass - 2

No. of pass - 3

SPEED(rpm)

RO

UG

HN

ESS(

Ra)

21

FIG 4.6 Effect of speed on hardness

LEGEND:



The hardness increases slightly but the burnishing process has no

significant effect on the hardness of the workpiece. The best hardness is obtained

at 2 number of passes and 300rpm (34 HRC).

29.5

30

30.5

31

31.5

32

32.5

33

33.5

34

34.5

0 100 200 300 400 500 600

No. of pass - 1

No. of pass - 2

No. of pass - 3

No. of pass - 1

No. of pass - 2

No. of pass - 3

SPEED(rpm)

HA

RD

NES

S(H

RC

)

22

CHAPTER 5

COATING

5.1 INTRODUCTION TO COATING

Friction and wear are major factors limiting the performance and service

life of tools and precision components. Coating them is the most effective and

frequently the only possibility of making a decisive difference to their operational

performance.

Tools coated improve the productivity and quality of metalworking and

plastics processing, while coated components in vehicles, machines and

appliances fulfil their functions more reliably and for a longer time.

It was vacuum coating that first made forward-looking developments

possible, for instance with tools for high-speed and dry working or highly loaded

components for the latest diesel injection systems.

Coating offers the following practical advantages:

1. Improved performance with smaller dimensions

2. Increased operational reliability and service life

3. Protection against deficient lubrication / emergency running conditions and

the possibility of running dry

4. Reduction in energy, fuel and lubricant consumption

5. Avoidance of the use of expensive materials

6. Reduction in liability to corrosion

7. Bio-compatibility and approval for food processing applications

23

Coating processes may be classified as follows:

Vapour deposition:

Chemical vapour deposition

1. Metalorganic vapour phase epitaxy

2. Electrostatic spray assisted vapour deposition (ESAVD)

3. Sherardizing

4. Some forms of Epitaxy

5. Molecular beam epitaxy

Physical vapour deposition

1. Cathodic arc deposition

2. Electron beam physical vapour deposition (EBPVD)

3. Ion plating

4. Ion beam assisted deposition (IBAD)

5. Magnetron sputtering

6. Pulsed laser deposition

7. Sputter deposition

8. Vacuum deposition

9. Vacuum evaporation, evaporation (deposition)

Chemical and electrochemical techniques

1. Conversion coating

2. Anodising

3. Chromate conversion coating

4. Plasma electrolytic oxidation

5. Phosphate (coating)

6. Ion beam mixing

7. Pickled and oiled, a type of plate steel coating

8. Plating

9. Electroless plating

10. Electroplating

24

Some of the common materials used for coating tools are:

1. TiN

2. TiCN

3. AlCrN

4. TiAlN

5. TiCrN

The material that has been chosen to coat the burnishing tool is TiAlN because of

its wear resistance properties.

5.2 TITANIUM ALUMINIUM NITRIDE (TiAlN) COATING

One commercial coating type used to improve the wear resistance of

tungsten carbide tools is the TiAlN coating. The coating are sometimes doped

with at least one of the elements like silicon, boron, oxygen in order to improve

selected properties for specific applications These coatings are also used to create

multilayer systems. The coating types mentioned above are applied to protect

tools including special tools for medical applications. They are also used as

decorative finishes. Aluminium Titanium Nitride (TiAlN) is a hard coating that

solves many tribological problems with components that can be coated at

temperatures of 450°C - 475°C. Calico-TiAlN is normally applied to steels,

hardened steels, aluminium and materials where high wear resistance and

lubricity are needed. TiAlN coating provides exceptional oxidation resistance and

extreme hardness. That's why this coating works well in very demanding cutting

tool applications, especially when tools are being pushed to the max.

Titanium aluminium nitride (TiAlN) or aluminium titanium nitride (AlTiN; for

aluminium contents higher 50 at. %) stands for a group of metastable hard

coatings consisting of the metallic elements aluminium and titanium, and

nitrogen. Four important compositions (metal content 100 at. %) are deposited in

industrial scale by physical vapour deposition methods.

25

The coatings are mostly deposited by cathodic arc deposition or magnetron.

Even though most TiAlN and AlTiN coatings are industrially synthesized using

alloy targets with specific percentages of aluminium and titanium it is possible to

produce TiAlN coatings with pure Al and Ti targets using a cathodic arc

deposition technique. TiAlN and AlTiN coatings from pure Al and pure Ti targets

by Cathodic arc deposition have been produced industrially by Nano Shield PVD

Thailand since 1999. By using separate target technology it is possible to offer

more flexibility regarding the structure and composition of the coating.

5.2.1 APPLICATIONS

1. High performance coating in ferrous materials.

2. Excellent high temperature resistance and hardness.

3. Maintains high surface hardness at elevated temperatures improving

tool life and allowing faster feed rates.

4. Produces aluminium oxide layer at high temperature which reduces

thermal conductivity transferring heat into the chip.

5. Excellent in dry machining, machining titanium alloys, stainless

alloys, and cast iron.

5.3 PHYSICAL VAPOUR DEPOSITION

Physical vapour deposition (PVD) describes a variety of vacuum

deposition methods used to deposit thin films by the condensation of a vaporized

form of the desired film material onto various workpiece surfaces (e.g., onto

semiconductor wafers).

The coating method involves purely physical processes such as high-

temperature vacuum evaporation with subsequent condensation, or plasma sputter

bombardment rather than involving a chemical reaction at the surface to be coated

as in chemical vapour deposition.

26

5.3.1 PROCESS OF PHYSICAL VAPOUR DEPOSITION

The high-purity, solid coating material (metals such as titanium, chromium

and aluminium) is either evaporated by heat or by bombardment with ions

(sputtering). At the same time, a reactive gas (e.g. nitrogen or a gas containing

carbon) is introduced; it forms a compound with the metal vapour and is deposited

on the tools or components as a thin, highly adherent coating. In order to obtain a

uniform coating thickness, the parts are rotated at uniform speed about several

axes. The properties of the coating (such as hardness, structure, chemical and

temperature resistance, adhesion) can be accurately controlled.

In the automotive world, it is the newest alternative to the chrome plating that has

been used for trucks and cars for years. This is because it has been proven to

increase durability and weigh less than chrome coating, which is an advantage

because a vehicle's acceleration and fuel efficiency will increase. Physical vapour

deposition coating is gaining in popularity for many reasons, including that it

enhances a product’s durability. In fact, studies have shown that it can enhance

the lifespan of an unprotected product tenfold.

Variants of PVD include, in alphabetical order:

1. Cathodic Arc Deposition: In which a high-power electric arc discharged at

the target (source) material blasts away some into highly ionized vapor to

be deposited onto the work piece.

2. Electron beam physical vapour deposition: In which the material to be

deposited is heated to a high vapour pressure by electron bombardment in

"high" vacuum and is transported by diffusion to be deposited by

condensation on the (cooler) work piece.

3. Evaporative deposition: In which the material to be deposited is heated to

a high vapour pressure by electrically resistive heating in "low" vacuum.

4. Pulsed laser deposition: In which a high-power laser ablates material from

the target into a vapour.

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5. Sputter deposition: In which a glow plasma discharge (usually localized

around the "target" by a magnet) bombards the material sputtering some

away as a vapour for subsequent deposition.

PVD is used in the manufacture of items, including semiconductor devices,

aluminized PET film for balloons and snack bags, and coated cutting tools for

metalworking. Besides PVD tools for fabrication, special smaller tools (mainly

for scientific purposes) have been developed. They mainly serve the purpose of

extreme thin films like atomic layers and are used mostly for small substrates. A

good example are mini e-beam evaporators which can deposit monolayers of

virtually all materials with melting points up to 3500 °C.

Common coatings applied by PVD are Titanium nitride, Zirconium nitride,

Chromium nitride, Titanium aluminium nitride.

The source material is unavoidably also deposited on most other surfaces

interior to the vacuum chamber, including the fixtures to hold the parts.

5.4 CATHODIC ARC DEPOSITION

Cathodic arc deposition or Arc-PVD is a physical vapour deposition

technique in which an electric arc is used to vaporize material from a cathode

target. The vaporized material then condenses on a substrate, forming a thin film.

The technique can be used to deposit metallic, ceramic, and composite films.

5.4.1 PROCESS OF CATHODIC ARC DEPOSITION

The arc evaporation process begins with the striking of a high current, low

voltage arc on the surface of a cathode (known as the target) that gives rise to a

small (usually a few micrometres wide), highly energetic emitting area known as

a cathode spot. The localised temperature at the cathode spot is extremely high

(around 15000 °C), which results in a high velocity(10 km/s) jet of vaporised

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cathode material, leaving a crater behind on the cathode surface. The cathode spot

is only active for a short period of time, then it self-extinguishes and re-ignites in

a new area close to the previous crater. This behaviour causes the apparent motion

of the arc.

As the arc is basically a current carrying conductor it can be influenced by

the application of an electromagnetic field, which in practice is used to rapidly

move the arc over the entire surface of the target, so that the total surface is eroded

over time.

The arc has an extremely high power density resulting in a high level of

ionization (30-100%), multiple charged ions, neutral particles, clusters and

macro-particles (droplets). If a reactive gas is introduced during the evaporation

process, dissociation, ionization and excitation can occur during interaction with

the ion flux and a compound film will be deposited.

One downside of the arc evaporation process is that if the cathode spot stays

at an evaporative point for too long it can eject a large amount of macro-particles

or droplets. These droplets are detrimental to the performance of the coating as

they are poorly adhered and can extend through the coating. Worse still if the

cathode target material has a low melting point such as aluminium the cathode

spot can evaporate through the target resulting in either the target backing plate

material being evaporated or cooling water entering the chamber. Therefore

magnetic fields as mentioned previously are used to control the motion of the arc.

If cylindrical cathodes are used the cathodes can also be rotated during deposition.

By not allowing the cathode spot to remain in one position too long aluminium

targets can be used and the number of droplets is reduced. Some companies also

use filtered arcs that use magnetic fields to separate the droplets from the coating

flux.

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5.4.2 APPLICATION OF CATHODIC ARC DEPOSITION

Cathodic arc deposition is actively used to synthesize extremely hard film

to protect the surface of cutting tools and extend their life significantly. A wide

variety of thin hard-film, Super hard coatings and Nano composite coatings can

be this technology including TiN, TiAlN, CrN, ZrN, AlCrTiN and TiAlSiN.

This is also used quite extensively particularly for carbon ion deposition to create

diamond-like carbon films. Because the ions are blasted from the surface

ballistically, it is common for not only single atoms, but larger clusters of atoms

to be ejected. Thus, this kind of system requires a filter to remove atom clusters

from the beam before deposition. The DLC film from filtered-arc contains

extremely high percentage of sp3 diamond which is known as tetrahedral

amorphous carbon, or ta-C.

The coating was done at Oerlikon Balzers Coating India Ltd. by cathodic

arc deposition method.

Machining was done again after the tool was coated with TiAlN.

The input parameters were kept the same and the output parameters were

measured to know the effect of TiAlN coating on the burnishing tool.

FIG 5.1 COATED ROLLER

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5.5 TABULATION

AFTER COATING:

Table 5.1: Hardness and surface roughness of EN24 after

machining with TiAlN coated roller.

PASS SPEED

(rpm)

WITHOUT LUBRICANT WITH LUBRICANT

HARDNESS

(HRC)

ROUGHNESS

(Ra)

HARDNESS

(HRC)

ROUGHNESS

(Ra)

1

200 32 1.24 32 1.08

300 33 0.88 33 0.86

500 33 0.88 32 1.65

2

200 33 1.18 33 0.60

300 34 0.79 33 0.83

500 34 0.46 34 0.37

3

200 32 1.12 34 0.98

300 33 0.86 34 0.77

500 34 0.72 35 1.12

The results are drawn as a graph.

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LEGEND:



FIG 5.2 Effect of speed on hardness

From the graph it can be inferred that after coating, there is a general

trend of increasing hardness as the number of pass and speed increases. Highest

hardness is obtained at 300rpm and 3 passes when using kerosene as lubricant

(35HRC). Higher hardness are obtained when using lubricant.

31.5

32

32.5

33

33.5

34

34.5

35

35.5

0 100 200 300 400 500 600

No. of pass - 1

No. of pass - 2

No. of pass - 3

No. of pass - 1

No. of pass - 2

No. of pass - 3

SPEED(rpm)

HA

RD

NES

S(H

RC

)

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LEGEND:



FIG 5.3 Effect of speed on roughness

From the graph, it is inferred that there is a general trend of decreasing

roughness with speed. However, the best surface finish is obtained at 300rpm and

2 passes on an average. Lubricant has no effect on the roughness of the workpiece.

Best surface finish is obtained at 200rpm and 2 passes without lubricant.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 100 200 300 400 500 600

No. of pass - 1

No. of pass - 2

No. of pass - 3

No. of pass - 1

No. of pass - 2

No. of pass - 3

SPEED(rpm)

RO

UG

HN

ESS(

Ra)

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CHAPTER 6

RESULTS AND DISCUSSIONS

FIG 6.1 HARDNESS – WITHOUT LUBRICANT

LEGEND:

Straight lines – before coating

Dotted lines – after coating

29.5

30

30.5

31

31.5

32

32.5

33

33.5

34

34.5

1 Pass, 200rpm 1 Pass, 300rpm1 Pass, 500rpm2 Pass, 200rpm 2 Pass, 300rpm2 Pass, 500rpm3 Pass, 200rpm 3 Pass, 300rpm3 Pass, 500rpm

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FIG 6.2 HARDNESS – WITH LUBRICANT

LEGEND:



28

29

30

31

32

33

34

35

1 Pass,200rpm

1 Pass,300rpm

1 Pass,500rpm

2 Pass,200rpm

2 Pass,300rpm

2 Pass,500rpm

3 Pass,200rpm

3 Pass,300rpm

3 Pass,500rpm

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FIG 6.3 SURFACE ROUGHNESS – WITHOUT LUBRICANT

LEGEND:



0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1 Pass,200rpm

1 Pass,300rpm

1 Pass,500rpm

2 Pass,200rpm

2 Pass,300rpm

2 Pass,500rpm

3 Pass,200rpm

3 Pass,300rpm

3 Pass,500rpm

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FIG 6.4 SURFACE ROUGHNESS – WITH LUBRICANT

LEGEND:



0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1 Pass,200rpm

1 Pass,300rpm

1 Pass,500rpm

2 Pass,200rpm

2 Pass,300rpm

2 Pass,500rpm

3 Pass,200rpm

3 Pass,300rpm

3 Pass,500rpm

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1. Effect of speed on hardness and roughness of EN24

There is an increase in hardness as the speed increases and decrease in

roughness as the speed increases and then increases as the speed increases. This

is due to better stabilization of the tool and workpiece at increasing speeds. The

highest values of hardness and the lowest values of surface roughness are obtained

at the speed of 300rpm – 35HRC and 0.71µm on an average. The best surface

finish is at 0.37µm at 500rpm.

2. Effect of number of pass on hardness and roughness of EN24

As the number of passes increases, the roughness goes on decreasing

generally. The best surface finishes are obtained at 2 passes on an average. The

best surface finish is 0.37 µm at 2 passes. This may be because of repeatedly

passing the burnishing tool on the workpiece.

3. Effect of lubricant on hardness and roughness of EN24

The use of kerosene as lubricant has little to no effect on the roughness

of the workpiece. Usage of kerosene increases hardness generally but the increase

in hardness is very little. This may be because the heat generated while burnishing

is not so great so as to warrant the use of lubricant.

4. Effect of coating of roller on hardness and roughness of EN24

From the comparative graphs, it can be inferred that the coating the

tool with TiAlN increase the hardness and decreases the roughness significantly.

This may be due to increase in hardness of the tool after coating the tool. There

is a maximum reduction of 40.48% in surface roughness value after coating the

tool.

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CHAPTER 7

COST ESTIMATION

NO. PROJECT DETAILS COST(Rs.)

1 TOOL 15000

2 WORKPIECE 600

3 MACHINING 1100

4 HARDNESS TEST 1600

5 ROUGHNESS TEST 1600

6 COATING 220

TOTAL 20120

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REFERENCE

1. Malleswara Rao J. N., Chenna Kesava Reddy A. & Rama Rao P. V.,“The

effect of roller burnishing on surface hardness and surface roughness on mild

steel specimens”, International Journal Of Applied Engineering Research,

Dindigul Volume 1, No 4, (2011).

2. Deepak Mahajan, Ravindra Tajane - A Review on Ball Burnishing Process.

International Journal of Scientific and Research Publications, Volume 3, Issue

4, April 2013 ISSN 2250-3153

3. Hudayim Basak and H. Haldun Goktas,”Burnishing process on al-alloy and

optimization of surface roughness and surface hardness by fuzzy logic”,

Materials and Design ,Vol. 30 (2009),pp.1275–1281.

4. C.H. Che-Haron, Tool life and surface integrity in turning titanium alloy,

Journal of Materials Processing Technology 118 (2001) 231-237.

5. A.M. Hassan, The effects of ball and roller burnishing on the surface

roughness and hardness of some non-ferrous metals, Journal of Materials

Processing Technology 72 (1997).

Roller burnishing project report

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