investigation of acoustic emission and

130 Pages·2010·5.41 MB·English

INVESTIGATION OF ACOUSTIC EMISSION AND
SURFACE TREATMENT TO IMPROVE TOOL
MATERIALS AND METAL FORMING PROCESS

Dissertation

Submitted to

The School of Engineering of the

University of Dayton

In Partial Fulfillment of the Requirements for

The Degree

Doctor of Philosophy in Materials Engineering

By

Deming Cao

UNIVERSITY OF DAYTON

Dayton, Ohio

August, 2010
INVESTIGATION OF ACOUSTIC EMISSION AND SURFACE
TREATMENT TO IMPROVE TOOL MATERIALS AND METAL
FORMING PROCESS

APPROVED BY:

____________________________ ____________________________
Norbert Meyendorf, Ph.D. Daniel Eylon, D. Sc.
Advisory Committee Chairman Advisory Committee Member
Professor, Materials Engineering Professor and Director,
Materials Engineering

____________________________ ____________________________
Norman Hecht, Ph.D. Gerald Shaughnessy, M.S.
Advisory Committee Member Advisory Committee Member
Professor Emeritus, Materials Associate Professor, Mathematics
Engineering

____________________________
Paul T. Murray, Ph.D.
Advisory Committee Member
Professor, Materials Engineering

____________________________ ____________________________
Malcolm W. Daniels, Ph.D. Tony E. Saliba, Ph.D.
Associate Dean Dean, School of Engineering
School of Engineering
ii
ABSTRACT

INVESTIGATION OF ACOUSTIC EMISSION AND SURFACE
TREATMENT TO IMPROVE TOOL MATERIALS AND METAL
FORMING PROCESS

Name: Cao, Deming
University of Dayton

Advisor: Dr. Norbert Meyendorf

Silicon nitride and WC-Co cermet tools are used for metal forming
processes including extrusion and drawing. These materials are used to make
tool dies which are exposed to deformation caused by friction and wear.

Surface treatments such as ion implantation, laser blazing and coating have
been found to improve surface properties, to optimize tribological behavior
between the metal and die, as well as to extend service life of the tool dies.
Early detection and continuous monitoring processes by non destructive
testing (NDT) methods are needed in order to ensure the functionality of the
wear process and extend the tool service life. Acoustic emission is one of the
promising NDT methods for this application.

The surface treatment chosen for this investigation was ion implantation.
Three types of wear resistant materials with and without surface treatment
were selected for this project; silicon nitride and two tungsten carbides (6%
Cobalt and 10% Cobalt).

This investigation was conducted using a pin-on-disk device for
wear/friction tests of the selected materials with lubrication and/or without
lubrication against both a stainless steel disk and an aluminum disk. The
acoustic emissions generated during the experiments were recorded and
analyzed.

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The results of this investigation showed that the ion implantation improved
the tribological properties of the materials and reduced acoustic emission
and coefficient of friction. A linear relationship between the average
amplitude of the acoustic emission and the coefficient of friction of the
tested materials was found. The investigation demonstrated that the acoustic
emission method could be used to monitor the wear/friction processes.

iv
ACKNOWLEDGEMENTS

I would like to express my sincere gratitude to Dr. Meyendorf for all his help
during my graduate studies at the University of Dayton. Without his constant
support, this work could not have been accomplished.

I would also like to thank the members of my advisory committee, Dr.
Daniel Eylon, Dr. Murray, Mr. Gerald Shaughnessy for their time and
support and contribution to my academic development as well as for serving
on my research advisory committee. In particular, I would like express my
appreciation to Dr. Norman Hecht for all his assistance and suggestions.

I am grateful to the Dayton Area Graduate Studies Institute (DAGSI) whose
financial and functional support made the pursuit of a Ph.D. possible.

I would like to acknowledge the Fraunhofer Institute of Dresden (IZFP-D)
for their support of the research in funds, samples, instruments and technical
advices.

I am indebted to Dr. Jain and would like to thank him for providing the
experimental apparatus and for all his help. I also want to thank Ms. Cheryl
Seitz for her support.

Finally, a special thank goes to my wife, Ling and my daughter, Faith.

v
PREFACE

Silicon nitride and WC-Co cermet tool dies are commonly used for metal
forming processes including extrusion and drawing. Tool dies are exposed to
deformation caused by friction and wear. Surface treatments have been
found to improve surface properties and to optimize the tribological
behavior between the metal and die. The surface treatment (ion
implantation) tends to extend the service life of the tool dies. In addition it
was thought that the acoustic emission during the wear process could be
used to continuously monitor wear/friction of tool dies. In order to compare
and/or improve the tribological behavior of selected materials and to extend
service life of dies in metal forming processes, a laboratory study of
wear/friction in combination with analysis of acoustic emission was
initiated.

This investigation is focused on the following objectives:

1. Development of tools for deep drawing and cutting by using silicon
nitride and WC-Co with 6% and 10%Co as tool die materials. Study the
wear and friction behavior of these materials against both stainless steel and
aluminum using wear and friction tests.

2. Analysis of the acoustic emission signal and its relationship with wear and
friction processes under selected operating conditions. Development of an
acoustic emission method for detecting and/or monitoring wear and friction
behavior of the selected tool die materials during metal forming processes.

3. Determine the degradation behavior of these test materials during the
wear and friction processes.

4. Determine the effects of ion implantation on wear and friction behavior of
these test materials during the wear and friction processes.

vi
TABLE OF CONTENTS

ABSTRACT...................................................................................................iii

ACKNOWLEDGEMENTS............................................................................v

PREFACE......................................................................................................vi

LIST OF FIGURES……………………………………………………….....x

LIST OF TABLES..……………………………………………………….xiii

CHAPTER 1 INTRODUCTION TO RESEARCH MOTIVATION,
OBJECTIVE AND APPROACH……………………………………………1

CHAPTER 2 BACKGROUND……………………………………………4

2.1 BACKGROUND FOR FRICTION AND WEAR.……………………...4

2.2 BACKGROUND FOR IMPROVEMENT OF WEAR RESISTANCE
BY SURFACE COATING AND MODIFICATION……..…………...13

2.3 BACKGROUND FOR ACOUSTIC EMISSION PROCESS
MONITORING………………………………………………………...19

2.4 BACKGROUND FOR MICROSTRUCTURE AND SURFACE
CHARACTERIZATION………………………………………………27

CHAPTER 3 EXPERIMENTAL PROCEDURES……………………….32

3.1 OVERVIEW............................................................................................32

3.2 EXPERIMENTAL SETUP…………………………………………….32

3.3 ACOUSTIC EMISSION DETECTING SYSTEM.................................35
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3.4 SLIDING WEAR TESTING AND ANALYSIS PLAN……………….41

3.5 MATERIALS AND LUBRICANT EMPLOYED……………………..42

3.6 MEASUREMENT PROTOCOL………………………………………44

3.7 EXPERIMENTAL PROTOCOL………………………………………47

3.8 SAMPLE SURFACE CHARACTERIZATION……………………….49

CHAPTER 4 RESULTS………………………………………………….53

4.1 EFFECT OF MICROSTRUCTURE AND SURFACE TREATMENT.53

4.2 CORRELATION OF ACOUSTIC EMISSION AND COEFFICIENT
OF FRICTION…………………………………………………………58

CHAPTER 5 DISCUSSION AND CONCLUSIONS.…………………...93

5.1 OVERVIEW……………………………………………….…………...93

5.2 DISCUSSION AND CONCLUSIONS RELATED TO ACOUSTIC
EMISSION MONITORING, TOOL MATERIALS AND SURFACE
TREATMENT………………………………………………………….93

5.3 NEW RESULTS FROM THE INVESTIGATION……………………99

5.4 ROLE AND SIGNIFICANCE OF RESULTS FOR IMPROVEMENT
OF METAL FORMING PROCESSES………………………………...99

5.5 FUTURE WORK……………………………………………………..100

viii
APPENDICES…………………………………………………………….101

APPENDIX A EXPERIMENTAL DATA……………...………………..101

APPENDIX B SURFACE ROUGHNESS CHARACTERIZATION
DATA………………….…………………………………105

APPENDIX C SELECTED MATERIALS PROPERTIES……..………..108

REFERENCES……………………………………………………………109

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LIST OF FIGURES

1. Figure 2-1 Schematic of Representation of an AE Burst Signal……...21
2. Figure 2-2 Schematic of Representation of an AE Continuous Signal 22
3. Figure 2-3 The Microstructure of Si N Taken By SEM……………..28
3 4
4. Figure 2-4 The Microstructure of Ion Treated Si N Taken By AFM..29
3 4
5. Figure 2-5 The Microstructure of WC-Co Taken by Author Using
SEM……………………………………………………….31
6. Figure 3-1 Schematic of Pin-On-Disk Tribometer……………………34
7. Figure 3-2 Acoustic Emission Measurement Setup Scheme………….35
8. Figure 3-3 Preamplifier, Main amplifier and AE Transducer………...36
9. Figure 3-4 Strain Gauge Calibration Curve…………………………..44
10. Figure 3-5 Schematic of Strain Indicator 3800……………………….45
11. Figure 3-6 Schematic of White Light Interference Microscopy……...51
12. Figure 3-7 Schematic of SEM/EDS…………………………………..52
13. Figure 4-1 Sample WC-Co (10%) without Surface Treatment……….56
14. Figure 4-2 Sample WC-Co (10%) with Ion Implantation…………….56
15. Figure 4-3 AE RMS Signal Frequency Spectrums for Si N Sample...58
3 4
16. Figure 4-4 AE RMS Signal versus Revolution for Si N Sample…….60
3 4
17. Figure 4-5 Coefficient of Friction versus Revolution for Si N
3 4
Sample…………….………………………………………60
18. Figure 4-6 AE RMS Signal versus Revolution (One Rotation) for Si N
3 4
Sample……………………………………………………..61
19. Figure 4-7 Friction μ versus Revolution (One Rotation) for Si N
3 4
Sample……………………………………………………..61

20. Figure 4-8 AE RMS versus Distance for Ion Treated and Untreated
Si N ………………………………………………………66
3 4
21. Figure 4-9 μ versus Distance for Ion Treated and Untreated Si N …..66
3 4
22. Figure 4-10 AE RMS versus Distance for Ion Treated and Untreated
WC-Co(6%Co)……………………………………………67
23. Figure 4-11 μ versus Distance for Ion Treated and Untreated WC-
Co( 6%Co)………………………………………………...67
x