Tribological Performance of Advanced Polymeric Coatings
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TRIBOLOGICAL PERFORMANCE OF ADVANCED POLYMERIC COATINGS UNDER EXTREME OPERATING CONDITIONS A Dissertation by PIXIANG LAN Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Andreas A. Polycarpou Committee Members, Luis San Andrés Hong Liang Jonathan Felts Mohammad Naraghi Head of Department, Andreas A. Polycarpou December 2017 Major Subject: Mechanical Engineering Copyright 2017 Pixiang Lan ABSTRACT Polymers and their composites have favorable tribological performance such as low coefficient of friction (COF) and good corrosion resistance, when working as bearing materials. The present work is studying the tribological performance of thin (~ 10s of microns) high-bearing polymeric coatings under extreme working conditions, including high temperature, cryogenic temperature, high contact pressure, high chamber pressure, starved lubrication, and abrasive wear. This work is an important contribution in proving the concept of application of thin polymeric coatings in environments such as dry sliding bearing, valve sealing surfaces, hydrodynamic bearings and drilling application under different extreme working conditions. Three groups of polymers, namely Polytetrafluoroethylene(PTFE)-based, Polyether ether ketone (PEEK)-based, and Aromatic Thermosetting coPolyesters(ATSP)-based coatings were extensively studied. Out of the three groups of polymers, ATSP-based coating showed the most desirable tribological performance: ‗zero wear‘ at different temperature from -160°C to 260°C with dry sliding, extremely low wear coefficient (4.15×10-8 mm3/Nm) under starved lubrication condition, stable coefficient of friction (COF) and low wear rate under sand abrasive condition, and extreme low COF for oil and gas drilling application. Traditionally, the friction force between two solids is attributed to adhesion and deformation effects; where the adhesion force involves the shearing between the real ii contact surfaces and deformation is due to the hard material‘s asperities plowing on the softer material. This work proposes a phenomenological model of friction for viscoelastic materials by using the viscosity and elasticity parameters acquired by nano- indentation measurements at elevated temperatures. Substituting the viscosity and elastic modulus terms, the model showed reasonable COF for the coatings up to temperatures that were lower than the glass transition temperature. iii ACKNOWLEDGEMENTS I would like to thank my committee chair, Dr. Andreas A. Polycarpou, for his patient and professional guidance. And I also would like to thank my committee members, Dr. Luis San Andrés, Dr. Hong Liang, Dr. Jonathan Felts and Dr. Mohammad Naraghi, for their help and support throughout this research. Thanks also go to my friends and colleagues and the department faculty and staff for making my time at Texas A&M University a great experience. Finally, thanks to my father and my wife for their encouragement; and thanks to my lovely daughter for her company. iv CONTRIBUTORS AND FUNDING SOURCES Contributors Part 1, faculty committee recognition This work was supervised by a dissertation committee consisting of Professor Andreas Polycarpou, Luis San Andrés, Hong Liang and Jonathan Felts of the Department of Mechanical Engineering and Professor Mohammad Naraghi of the Department of Aerospace Engineering. Part 2, student/collaborator contributions The EDS analysis depicted in Chapter 5 was conducted by Dr. Kyriaki Polychronopoulou, a visiting professor of the Department of Mechanical Engineering. All other work conducted for the dissertation was completed by the student. Funding Sources This work was made possible in part by the Turbomachinery Research Consortium at Texas A&M University under Grant Number 1519x6; and by ExxonMobil Chemical Company, Global R&D, Baytown, Texas, USA, under Grant Number 28-406950-00001. v TABLE OF CONTENTS Page ABSTRACT ....................................................................................................................... ⅱ ACKNOWLEDGEMENTS .............................................................................................. ⅳ CONTRIBUTORS AND FUNDING SOURCES .............................................................. ⅴ TABLE OF CONTENTS .................................................................................................. ⅴⅰ LIST OF FIGURES ........................................................................................................... ⅰⅹ LIST OF TABLES .......................................................................................................... ⅹⅴⅰ 1. INTRODUCTION .......................................................................................................... 1 1.1 Tribology of polymers .............................................................................................. 1 1.2 Bulk polymers and their composites ........................................................................ 3 1.3 Coatings of polymers and their composites ............................................................. 5 1.4 Objective and research outline ................................................................................. 7 2. TRIBOLOGICAL PERFORMANCE OF ATSP-BASED AND PEEK-BASED COATINGS AT ELEVATED TEMPERATURE IN DRY CONDITION ..................... 11 2.1 Introduction ............................................................................................................ 12 2.2 Experimental .......................................................................................................... 14 2.2.1 High Temperature Tribometer (HTT) ....................................................... 14 2.2.2 Samples ..................................................................................................... 15 2.2.3 Experimental design .................................................................................. 18 2.2.4 Scanning Electron Microscopy (SEM) and wear analysis ........................ 19 2.3 Results and Discussion ........................................................................................... 20 2.3.1 Roughness and coating thickness .............................................................. 20 2.3.2 Tribological experiments ........................................................................... 22 2.3.3 SEM analysis ............................................................................................. 30 2.4 Conclusion .............................................................................................................. 38 3. TRIBOLOGICAL PERFORMANCE OF ATSP BASED COATINGS UNDER CRYOGENIC CONDITIONS ......................................................................................... 40 vi 3.1 Introduction ............................................................................................................ 41 3.2 Experimental .......................................................................................................... 44 3.2.1 Specialized cryogenic tribometer .............................................................. 44 3.2.2 Samples ..................................................................................................... 45 3.2.3 Experimental methodology ....................................................................... 47 3.3 Tribological experimental results ........................................................................... 48 3.4 SEM analysis .......................................................................................................... 52 3.5 Conclusion .............................................................................................................. 58 4. ADVANCED POLYMERIC COATINGS FOR TILTING PAD BEARINGS WITH APPLICATION IN THE OIL AND GAS INDUSTRY ....................................... 59 4.1 Introduction ............................................................................................................ 60 4.2 Experimental .......................................................................................................... 63 4.2.1 High pressure tribometer (HPT) and experiment configuration ............... 63 4.2.2 Samples ..................................................................................................... 64 4.2.3 Experimental design .................................................................................. 67 4.3 Tribological results and discussion ........................................................................ 69 4.3.1 Scuffing experiments ................................................................................. 69 4.3.2 Wear experiments: 4.3 Km sliding distance (30 min) ............................... 72 4.3.3 Durability experiments .............................................................................. 77 4.3.4 SEM analysis ............................................................................................. 82 4.4 Conclusion .............................................................................................................. 85 5. SAND ABRASIVE WEAR OF ADVANCED POLYMERIC COATINGS .............. 87 5.1 Introduction ............................................................................................................ 88 5.2 Experimental .......................................................................................................... 90 5.2.1 Ultra-High Pressure Tribometer (UHPT) and