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INFLUENCE of DISSOLVED HYDROGEN on the FATIGUE CRACK GROWTH BEHAVIOUR of AISI 4140 STEEL By

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INFLUENCE of DISSOLVED HYDROGEN on the FATIGUE CRACK GROWTH BEHAVIOUR of AISI 4140 STEEL By Wayne State University Wayne State University Dissertations 1-1-2014 Influence Of Dissolved Hydrogen On The aF tigue Crack Growth Behaviour Of Aisi 4140 Steel Varun Ramasagara Nagarajan Wayne State University, Follow this and additional works at: http://digitalcommons.wayne.edu/oa_dissertations Recommended Citation Ramasagara Nagarajan, Varun, "Influence Of Dissolved Hydrogen On The aF tigue Crack Growth Behaviour Of Aisi 4140 Steel" (2014). Wayne State University Dissertations. Paper 973. This Open Access Dissertation is brought to you for free and open access by DigitalCommons@WayneState. It has been accepted for inclusion in Wayne State University Dissertations by an authorized administrator of DigitalCommons@WayneState. INFLUENCE OF DISSOLVED HYDROGEN ON THE FATIGUE CRACK GROWTH BEHAVIOUR OF AISI 4140 STEEL by VARUN RAMASAGARA NAGARAJAN DISSERTATION Submitted to the Graduate School of Wayne State University, Detroit, Michigan in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY 2014 MAJOR: MATERIALS SCIENCE AND ENGINEERING Approved by: Advisor Date DEDICATION This dissertation work is dedicated to my beloved wife, my lovely mother, my inspiring father, my sweet sister and all my family members and my friends. ii ACKNOWLEDGEMENTS This investigation was carried out under a grant from Office of Naval Research (ONR) - ONR grant No: N 00014-09-1-0535. I would like to express my sincere thanks and gratitude to Dr. Asuri K. Vasudevan, Program Manager at ONR for the financial support of this research. I am deeply indebted to my mentor, teacher and advisor Prof. Susil K. Putatunda for his continuous financial and technical support in bringing this work to its current state. This work would have remained only as a research proposal had it not for his efforts to apply, struggle and secure funding for this research. In addition, after advising my Master’s degree thesis, I would like to thank him again for the having confidence, faith and patience to assign this project to me. I want to thank Mr. Eugene Snowden and Mr. Marvin Santure, the technicians at the engineering workshop for their work in preparing all the test samples. I am very thankful to Dr. James M. Boileau and Mr. John Kelly from Ford Motor Company, Dearborn, MI for all their support to allow me to complete part of my work at Ford Research Labs for sharing of knowledge and also for the machining support to make the test samples. I am immensely thankful to Prof. Eswarahalli Sundararajan Dwarakadasa, retired professor at Indian Institute of Science (IISc), Bangalore, India for his advice on my fatigue experiments. I want to express my appreciation to Dr. Srinivasan Venkatesan who was a part time faculty at Wayne State for his inputs on electrochemical aspects of my studies. I am grateful to my committee members, Prof. Howard W. Matthew, Prof. Golam M. Newaz, Prof. Gavin Lawes and Dr. James M. Boileau for their suggestions, feedback, taking time to review my work and for serving on my graduate defence committee. iii My sincere thanks to my father, G.V. Nagarajan, who initiated and advised me to pursue my Ph.D. degree. This endeavor was possible only due to his belief in my ability and strength. My Ph.D. journey was achievable due to encouragement and emotional support from my mother, R. Vagadevi, whose words helped me a lot during difficult times. I would have given up my degree if not for my mother’s strong words of encouragement. The final dissertation report was largely possible, in this final form, only due pressing support from my dear wife Archana Nagarajan. She was instrumental in supporting me throughout my degree and I appreciate her efforts in bearing down on me to complete this report as quickly as possible. The list is not complete without appreciating my sweet sister, Varsha Ramasagara Nagarajan, for her encouragement and support. I want to say thanks to my mother in law, M.S. Sharadamma, and father in law, Prof. K. Nagarajan, for their prayers and blessings. In addition, I am grateful to my grandparents for being very supportive of my career. This dissertation reached completion only due to the assistance, support and advice from my dear lab mates, Codrick J. Martis and Saranya Panneerselvam. I appreciate their efforts to assist in my experiments, to assist me with my paperwork in my absence and for assistance in organizing the prospectus and final defence meetings. iv FOREWORD A lot of work has been done on understanding the influence of hydrogen on the fatigue behaviour of high and low strength steels. Though many studies tend to develop a theoretical equation based mechanism to explain the experimental observations, these equation tend to give unsatisfactory trends when the process conditions are slightly modified than the initial conditions even after accounting for the expected change due to modification of process conditions. Therefore, it is my sincere effort, through this study, to explain my experimental observations and correlate them to any observable evidence which might throw light on the mechanistic process involved. In addition, an honest attempt has been made to explore austempering as a possible route to obtaining high strength steel and verify its susceptibility to hydrogen in a cyclic loading condition. v TABLE OF CONTENTS Dedication ....................................................................................................................................... ii Acknowledgements ........................................................................................................................ iii Foreword ......................................................................................................................................... v List of Figures ................................................................................................................................ ix List of Tables ............................................................................................................................... xiv CHAPTER 1 - INTRODUCTION .................................................................................................. 1 Fatigue Behaviour and Corrosion Fatigue .................................................................................. 1 Stress Corrosion Cracking .......................................................................................................... 3 CHAPTER 2 - LITERATURE REVIEW ....................................................................................... 6 Fatigue Behaviour of Metallic Materials .................................................................................... 6 Stress Corrosion Cracking .......................................................................................................... 8 Hydrogen Embrittlement .......................................................................................................... 11 AISI 4140 .................................................................................................................................. 16 Austempering Heat Treatment .................................................................................................. 18 CHAPTER 3 - OBJECTIVES ...................................................................................................... 20 CHAPTER 4 - EXPERIMENTAL MATERIALS AND METHODS ......................................... 21 Material ..................................................................................................................................... 21 Heat Treatment.......................................................................................................................... 23 Microstructural Analysis ........................................................................................................... 25 vi X-Ray Diffraction (XRD) Analysis .......................................................................................... 35 TEM Imaging ............................................................................................................................ 37 External Hydrogen Charging .................................................................................................... 46 Hydrogen Concentration Analysis (Vacuum Hot Extraction) .................................................. 47 Fatigue Testing.......................................................................................................................... 48 Stress Corrosion Cracking Testing ........................................................................................... 49 Fractography ............................................................................................................................. 49 CHAPTER 5 - RESULTS ............................................................................................................. 51 Influence of Time on dissolved hydrogen concentration .......................................................... 51 Fatigue crack growth behaviour of the material in Annealed (as-received) condition ............. 54 Fatigue crack growth behaviour of the material in Austempered Batch - 1 (AB1) condition .. 63 Fatigue crack growth behaviour of the material in Austempered Batch 2 (AB2) condition .... 71 Comparison of Fatigue Crack Growth Behaviour among different heat treatment conditions 80 Stress Corrosion Cracking ........................................................................................................ 98 Qualitative mechanism to explain
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