Sliding Friction and Wear Behavior of High Entropy Alloys at Room and Elevated Temperatures

118 Pages·2016·5.65 MB·English

by  Kadhim, Dheyaa

SLIDING FRICTION AND WEAR BEHAVIOR OF HIGH ENTROPY ALLOYS
AT ROOM AND ELEVATED TEMPERATURES
Dheyaa Kadhim, B.S.
Thesis Prepared for the Degree of
MASTER OF SCIENCE
UNIVERSITY OF NORTH TEXAS
December 2016
APPROVED:
Thomas W. Scharf, Major Professor
Rajarshi Banerjee, Committee Member
Sundeep Mukherjee, Committee Member
Andrey Voevodin, Chair of the
Department of Material Science
and Engineering
Costas Tsatsoulis, Dean of College of
Engineering
Victor Prybutok, Vice Provost of Toulouse
Graduate School
Kadhim, Dheyaa. Sliding Friction and Wear Behavior of High Entropy Alloys at
Room and Elevated Temperatures. Master of Science (Material Science and
Engineering), December 2016, 104 pp., 13 tables, 45 figures, chapter references.
Structure-tribological property relations have been studied for five high
entropy alloys (HEAs). Microhardness, room and elevated (100°C and 300°C)
temperature sliding friction coefficients and wear rates were determined for five HEAs:
Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4; Co Cr Fe Ni Al0.25 Ti0.75; Ti V Nb Cr Al;
Al0.3CoCrFeNi; and Al0.3CuCrFeNi2. Wear surfaces were characterized with
scanning electron microscopy and micro-Raman spectroscopy to determine the wear
mechanisms and tribochemical phases, respectively. It was determined that the two
HEAs Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4 and Ti V Nb Cr Al exhibit an excellent
balance of high hardness, low friction coefficients and wear rates compared to
440C stainless steel, a currently used bearing steel. This was attributed to their more
ductile body centered cubic (BCC) solid solution phase along with the formation of
tribochemical Cr oxide and Nb oxide phases, respectively, in the wear surfaces.
This study provides guidelines for fabricating novel, low-friction, and wear-resistant
HEAs for potential use at room and elevated temperatures, which will help
reduce energy and material losses in friction and wear applications.
Copyright 2016
by
Dheyaa Kadhim
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ACKNOWLEDGEMENTS
I would like to acknowledge the contribution and extensive knowledge of Dr.
Thomas Scharf for lending his valuable time to teach and guide me, without whom this
work would not have been possible. I would sincerely thank him for his technical insight
and patience in motivating and nurturing me throughout this work. Next, I am grateful to
my committee members, Dr. Rajarshi Banerjee and Dr. Sundeep Mukherjee who have
been helpful and generous with their time and expertise to evaluate my thesis.
I appreciate PhD student Bharat for being there for me as a friend, helper, and an
encourager. Also, I would like to thank my friend Riyadh for continuous support, and my
lab mate Jonova for helping me in SEM imaging. Also, I would like to thank my friends
and colleagues Jon-Erik, Tinubu, Victor, Vishal, Mantri, Jitendra, Aditya, and Andres. I
also appreciate the help of other colleagues and friends. I would like to express my thanks
for my friends Safaa, Waleed, Alaa, Majeed, Sasan, Amal, Saad, Raed, and Mohammed
Alqaisi.
My acknowledgement is to my parents and family members back in Iraq, who were
always with me with their prayers, love, and blessings, who encouraged me and provided
tremendous support throughout my life. Without their help, I would not be here.
Finally, I would like to acknowledge the Higher Committee for Education
Development (HCED) in Iraq. Thanks for the financial support from the first day I set my
foot into the university. You helped me in so many ways.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS iii
LIST OF TABLES viii
LIST OF FIGURES ix
LIST OF ABBREVIATIONS xiii
CHAPTER 1: INTRODUCTION AND MOTIVATION 1
1.1 Introduction 1
1.2 Motivation 2
1.3 Objectives 2
1.4 Organization of Thesis 3
1.5 References 4
Chapter 2: BACKGROUND AND LITERATURE REVIEW 5
2.1 Description 5
2.2 Meaning and History of Tribology 5
2.3 Cost of Tribology Ignorance 6
2.4 Friction 7
2.4.1 Basic Mechanisms of Sliding Friction 9
2.4.2 Friction Transitions During Sliding 10
2.5 Wear 12
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2.5.1 Types of Wear 12
2.6 Summary 15
2.7 Definition of HEAs 16
2.8 The Concept of High Entropy Alloys 16
2.9 Multi-Principal-Element Effect 18
2.9.1 High Entropy Effect 19
2.9.2 Lattice Distortion Effect 20
2.9.3 Sluggish Diffusion Effect 22
2.9.4 Cocktail Effects 23
2.10 Crystal Structure of Simple Solid Solution Phases 24
2.11 High Entropy Alloys Research and Applications 26
2.12 References 29
CHAPTER 3: EXPERIMENTAL PROCEDURES AND METHODS 34
3.1 Fabrication and Preparation of Specimens 34
3.2 Characterization Techniques 35
3.2.1 X-Ray Diffraction (XRD) 35
3.2.2 Vickers Micro-Hardness Testing 36
3.2.3 Pin on Disk Tribometer 36
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3.2.4 Scanning Electron Microscopy (SEM) 37
3.2.5 Optical Microscopy 37
3.2.6 Raman spectroscopy 38
3.3 References 49
CHAPTER 4: RESULTS AND DISCUSSION 40
4.1 XRD and Microstructure Analyses 40
4.1.1 Alloy 1- Co0.5CrCo0.5FeNi1.5AlTi0.4 40
4.1.2 Alloy 2 -CoCr Fe Ni Al0.25 Ti0.75 43
4.1.3 Alloy 3- Ti Nb Cr Co Al 45
4.1.4 Alloy 4- Ti V Nb Cr Al 48
4.1.5 Alloy 5- Al0.3CoCrFeNi 51
4.1.6 Alloy 6- Al0.3CuCrFeNi2 54
4.2 Microhardness Analysis 57
4.2.1 Alloys 1 57
4.2.2 Alloy 2 57
4.2.3 Alloy 3 59
4.2.4 Alloy 4 60
4.2.5 Alloys 5 and 6 61
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4.3 Tribological Behavior 64
4.3.1 Friction Behavior at room temperature (RT) 65
4.3.2 Friction Behavior at 100°C 70
4.3.3 Friction Behavior at 300°C 75
4.4 Wear Mechanism 80
4.4.1 Analysis of SEM Images of Worn Surfaces with
Corresponding Pin 80
4.4.2 Raman Spectroscopy of Wear Tracks 86
4.4.3 Wear Rates 89
4.4.3.1 Alloys1 and 2 89
4.4.3.2 Alloys 3 and 4 90
4.4.3.3 Alloys 5 and 6 90
4.5 References 92
CHAPTER 5: SUMMARY AND CONCLUSION 99
5.1 Conclusions 99
5.2 Potential Applications of High Entropy Alloys 1 and 4 103
CHAPTER 6: RECOMMENDATIONS FOR FUTURE WORK 104
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LIST OF TABLES
2.1. Physiochemical properties for commonly elements employed in
HEAs systems 25
3.1. Lists the name and compositions notations of specimens. 34
4.1. Chemical composition in at. % of phases present in alloy 1 42
4.2. Presents the chemical compositions in at% of the phases present
in alloy 2. 45
4.3. Presents chemical composition in at% of conventional alloy 3. 46
4.4. Presents chemical composition in at. % of Ti V Nb Cr Al high
entropy alloy 4. 49
4.5 Chemical composition in at. % of as cast Al0.3CoCrFeNi high
entropy alloy 5. 53
4.6. Chemical composition at. % of as cast Al0.3CuCrFeNi2 high
entropy alloy. 55
4.7. Atomic radii of the elements employed in the Alloys1 and 2. 58
4.8. Presents atomic radii of elements used alloy 4. 61
4.9. Atomic radii of the elements employed in the alloys 5 and 6. 63
4.10. Summary of averaged wear track depth, cross-sectional wear
area removed, and wear factor for all high entropy alloys employed
in the present research at room temperature. 91
5.1 summarizes the microstructural phases, hardness, friction and wear
properties of the 6 alloys. 100
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LIST OF FIGURES
Figure 2.1. Illustration of normal force, lateral force, and friction force 8
Figure 2.2. Schematic illustration of different stages of friction 10
Figure 2.3. Schematic illustration of several fashions of friction 11
Figure 3.4. The mixing entropy as a function of the number of elements
for equimolar alloys 17
Figure 2.5. Five-component alloy with equiatomic proportions after
and before mixing 19
Figure 2.6. Schematic illustration of (a) BCC and (b) FCC crystal
structures with five major elements 21
Figure 2.7. Schematic illustration demonstrating severe lattice distortion
in the five-component BCC lattice structure 22
Figure 2.8. Plot showing the effects of Aluminum on the hardness
and crystal structure evolution in Al CoCrFeNi high entropy alloy. 24
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Figure 4.1. XRD pattern of Co0.5CrCo0.5FeNi1.5AlTi0.4 high
entropy alloy 1. 41
Figure 4.2. Representative SEM image of Co0.5CrCu0.5FeNi1.5AlTi0.4
high entropy alloy 42
Figure 4.3. XRD pattern of CoCr Fe Ni Al0.25 Ti0.75 high entropy alloy 2 44
Figure 4.4. SEM images of CoCr Fe Ni Al0.25 Ti0.75 high entropy
alloy showing the different region. 44
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