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STRUCTURE AND STRENGTHENiNG OF EVAPORATED CHROMIUM FILMS

by

s. LOGANATHAN

Industrial Tribotogy Machine Dynamics and Maintenance Engineering Centre (ITMMEC)

Submitted

n fulfilment of the iequi"ements of the 曲 g'ee of

DOCTOR OF PHILOSOPHY

to the

INDIAN INSTITUTE OF TECHNOLOGY, DELHI

July, 1993

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Dedicated to My Parents

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CERTIFICATE

This is to certify that the thesis entitled "Structure and Strengthening of Evaporated Chromium FiIms'' being subm汝ed by Mr. S. Logan試han to the indian Institute of Technology, Delhi, for the award of the deg甲e of Doctor of Philosophy, is a record of bon師de research work carried out by him under my guidance and supervision. To my knowledge社has reached the standard of fu用hling requirements of the degree. The matter embodied in this thesis has not been subm批ed, in part or full, to any other Univers町or Inst比ute for the award of any degree or diploma.

(Amitabh Jamn) Associate Professor,

Industrial Tribology Machine Dynamics and Maintenance Engineering Centre.

Indian Institute of Technology.

New Delhi 110016, INDiA

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ACKNOWLEDGEMENTS

I fe& proud in expressing my profound gratitude to Dr. Amitabh Jamn tor his guidance and pos

ve criticism during the pursu

of this research work. I shall always be indebted to him for his constant encouragement and valuable suggestions during the course of this work.

I gratefully acknowl

ge the he'p extended and fachl

les provided by Professor A. Sethuramiah, Head, ITMMEC, Pα

essor A.B. Bhattacha

rya, GARE, and Professor G.K. Mehta, Director, Nuclear Scienoe C

ntre.

I wish to thank D

お.

R.D

.ね町

and Chatar Singh for the help they provided during XRD analyses and SEM/Efl43<

a

ses respectively. I am thankful to Drs. Ami Chand ,G. Bose, B.S. Panwar and Sudhir Chandra, CARE for their support. I wish to thank Dr. D. Kanjilat, Mr. Jaipal and other Pelletron group members ,Nuclear Science Centre for the

lp p

iided in MeV ion irradiation. I wish to acknowledge the help rendered by lJr. Sadhna Sh

応旧

stava during this work. I wish to thank Ms. Sangeeta Srivastav for her help at

面打

cal mom

馴吐

s during this work.

My special thanks to my friends ifi E

.ぬ

nnir Selvam and his mother Ms. Selvi Etamvazhuthi, Mr. K.R. Srinivasan, M

Y. Sripathi and Dr. B.K. Ratnam, and other

iends without whose help this

如永加

uld not have been completed.

would like to express my sincere thanks to the technical staff of ITMMEC.for their help and co-operation

wish to acknowledge the

廿

me

help extended by

‘い

gicsoifi' for their services.

g

(s. LOGANATHAN)

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ABSTRACT

In the present work, chromium, an tmportant metallic tribological coating deposited on 304 stainless steel substrates by electron beam evaporation has been studied. The studies include tribological properties, characterization of chromium coatings deposited at various tempeはures and strengthening by keV and MeV ion irradiations.

The evaporation of Cr thin 石lms was carried out at three d肝ereilt substrate temperatures. Fracture cross se面on of the films show that as the depos面on temperature is increased

(1) a voided structure changes to a full density structure and

(2) the vertical polycrystall比es that make up the film increase in cl治meter and the film appears increasingレcolumnar.

Microhardness measurements were carried out by both Knoop and Vickers indenters under varying load (10 g toふ刃g). The subst胤es coated w忙h Cr showed higher hardness compared to uncoated substrates.

Adhesion of the coatings (of thickness i micron) deposited at i 8O0 C and 3800 C were evaluated by the standa旧 Scばch adhesion tester w比h a diamond stylus.

Chromium coatings were found to exhibit failure in a variety of modes when subjected to scratch tes廿ng under a progressively in叩asing load加mO-lOO N.

The peげormanとe of the co舗ng depos比ed at 380。C was found to be better也an the coating deposited at 180OC. This d施rence is attributed to the lower intrinsic stress level and the coarser columnar structure compared to the coatings deposited at i 80O C.

ln the key energy range, 75肥Vn忙rogen ion implantation induced changes in the tribological properties of 1300入 Cr石lms depos比ed at i加、C on 304 stainless steel substrates were studied. Ion implantation was carried out at a dose of 2x1017 ions/cm2.

Microhardness values were measured at various loads. Friction and wear tests were carried out with a ball-on-disc tribometer with an oscillating steel ball under lubricated conditions. The wear tracks were analyzed under the SEM.

The implanted film showed an increase in hardness when compared to the as-deposited film. The friction trace goes through a peak at a certain stage of the wear

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test. The peak was found to correlate with the failure of the film. Compared to the as-depos仕ed film, the implanted film showed a greatly extended sliding I什e. XRD studies shows that the implanted nitrogen goes into the solid solution of the FCC matrix of the 304 stainless steel substrate.

ln the MeV range, the effect of 75 MeV Ni ion irradiation on the tribological properties of thin chromium石Ims (of thickness i .4い)depos比edw油out any deliberate heating on 304 stainless steel substばes were studied.

Cr films showed a near 100% increase in 細oop hardness at i O g load when they were irradiated w比h 75 MeV Ni ions to a dose of 1x1015 ions/cm、 at a dose臣蚊e of 4.5 nA/mm2.

The studies show that the electronic ene勺y toss, which 1 s dominant at the chosen energy has resulted in some structural modifications in the flim. The same resu比s were obtained when the irradiation was carried out at liquid n仕rogen tempe胤ure.

The i nc旧ase in ha司ness on imョdiation was studied as aんnction of dose and dose rate.

Cr coatings depos比edw比hout heating exhib仕 a higher increase in hardness compared to coatings depos比ed at 1800C and 380OC as a 母su比 of high energy irradiation. This 加nd suggests that the flim structure Which e丸馴ts at I叫substた蚊e tempe胤ure is more conducんefor high energy ion mod市cations.

Sc胤ch adhesion tests of the Cr石lm depos辻edw比ho吐substrate he舗ng show that there is a pronounced increase in the integrity and adhesion of the 石lm 訳em irradiation.

A reduction in thickness of Cr石lms was observed when the同ystep stylus was moved across the boundary of the unirradiated and irradiated regions. The reduction in thickness was observed in both, samples irradiated without forced cooling and samples irradiated at liquid nitrogen temperature. This is for the first time that a dimensional change has been observed in a cystalline metallic material. The uncoated stainless steel substrate did not exhibit a dimensional change after irradiation

The microstructure as revealed by fracture cross-sections is not appreciably changed following irradiation. The XRD studies reveaJ that irradiation causes an anisotropic strain i n the lattice planes of the Cr film. After irradiation all austenite peaks

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of the SUbstrat6 Sh潰 owe Bragg angles which shows that a compressive strain is introduced in the substrate as a result of irradiation.

A hardening effect was observed in the uncoated 304 stainless steel as result of MeV ion irradiation.

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20 20 20

L 3 一り 2 2 2 CONTENTS

CERTIFICATE

ACKNOWLEDGEMENTS ABSTRACT

LIST OF FIGURES LIST OF TABLES CHAPTER i INTRODUCTION

i .1 INTRODUCTION

i _1 .1 Factors governing coating properties 1.1.2 Beam-Solid Interaction

i .2 AIM OF THE PRESENT WORK 1.3 L4 旧UT OF THE CHAPTERS

CHAPTER 2 REVIEW OF UTERA1RE

1 2 2 2

INTRODUCTION

PREVIOUS WORK ON CO打ING STRUCTURE AND PROPERTIES

2.3 PREVIOUS WORK ON SCRATCH ADHESION TESTS 2.4 PREVIOUS WORK USING keV BEAMS

2.5 PREVIOUS WORK USiNG MeV ION BEAMS

CHAPTER 3 EXPERIMENTAL AND ANALYTICAL METHODS

I NTRODUCTION

SUBSTRATE PRE『狐RATION 3.3 SUBSTRATE CLEANING

3.4 CHROMIUM THIN FILM DEPOSITION 3.5 CG8'TING THICKNESS MEASUREMENT

1 2 3 3

13 15 18

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J rJ rC 2 2 2 6 7 8 2 2 2 36 39

0 6 4 4

3.6 TALYSTEP MEASUREMENT 3.7 MICROHARONESS TESTING 3.8 FRICTION AND WEAR TEST 3.9 SCRATCH ADHESION TESTER 3.10 IRRADIATION AT key ENERGIES 3.11 IRRADIATION AT MeV ENERGY

3.12 SG6NNING ELEGTRON MICROSCOPE (SEM) AND ENERGY DISPERSIVE

ANALYSIS 0F X-RAS (ELAX) 313 X-RAY DIFFR飯汀!ON TECHNIQUE

CHAPTER 4 EtECT OF VARYING THE SUBSTRATモTEMPERAi旧RE

41 INTRODUCTION 4.2 RESULTS

4.2.1 Scratch Tests on an Uncoated 304 Stainless Steel Sub帥敵e

4.2.2 Sctch Adhesion Test on Chmium Coatings Depoed on 304 Stainless Steel Subsates

4.2.3 Microhardness Measurements on Uncoated and Coated Specimens

4.3 DISCUSSION 4.4 CONCLUSIONS

CHAPTER 5 IRRADIATION川■而v ENERGIES

5.1 INTRODUCTION 5.2 RESULTS

5.2.1 Ion Implantation

5.2.2 EDAX Spectra of Uncoated and Coated Specimens 5.2.3 Microhaness Measurements on Implanted Specimens

ロ」 nU 2 3

32 32 32 33

8 8 hD 890 4 4 4 4 4 5

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81

92

4 ォ什 1 C9 9

99 ios i 09

5.2.4 5.2.5

Tribological Tests XRD Studies

02 ニ】 G

5.3 DISCUSSION 5.4 CONCLUSIONS

3 2 J D

CHAPTER 6 ION IRRADIATiON AT MeV ENERGIES

6.1 INTRODUCTION 63

6.2 RESULTS 64

6.2.1 Microhardss Studies-Bad Resu 64 6.2.2 w rnpeure Irradions 66

6.2.3 Dosependence 67

6.2.4 Dose Rate Dependence 67

6.2.5 Irradiation Haening ELects in Coatings Deposed at

Vlous Temperatures 68

6.2.6 Unrrnof Beam Current Dens

6.2.7 iickness Cont旧面on 70

6.2.8 Scratch Adhesion Tests 71

6.2.9 Microstructuralalysis by SEM 76 6.2.10 Microstructural Analysis by XRD 77 6.2.11 Irradion of Uncoated Samples 79 6.212 Applicaon of the Haness Model 80 6.3 DISCUSSION

6.4 CONCLUSIONS

CHAPTER 7 CONCLUSIONS AND ScOPE OF FUTURE WORK

7.1 CONCLUSIONS

7.2 SCOPE OF FUTURE WORK

REFERENCES

LIST OF PUBLiCATIONS BIO-DATA

References

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