ENVIRONMENT-FRIENDLY POLYMERIC BOUNDARY LUBRICANTS FOR MECHANICAL BEARING SYSTEMS MOHAMMED ABDUL SAMAD NATIONAL UNIVERSITY OF SINGAPORE 2010 ENVIRONMENT-FRIENDLY POLYMERIC BOUNDARY LUBRICANTS FOR MECHANICAL BEARING SYSTEMS MOHAMMED ABDUL SAMAD (B. E, Osmania University, Hyderabad, India M.S., King Fahd University of Petroleum & Minerals, Dhahran, KSA) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF MECHANICAL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2010 Preamble Preamble This thesis is submitted for the degree of Doctor of Philosophy in the Department of Mechanical Engineering, National University of Singapore under the supervision of Dr. Sujeet Kumar Sinha. No part of this thesis has been submitted for any degree or diploma at any other Universities or Institution. As far as the author is aware, all work in this thesis is original unless reference is made to other work. Part of this thesis has been published/accepted and under review for publication as listed below: List of Publications 1. M. Abdul Samad, Satyanarayana Nalam and S. K. Sinha, Tribology of UHMWPE film on air-plasma treated tool steel and the effect of PFPE overcoat, Surface & Coatings Technology, 204 (2010) 1330-1338. (Chapter & part of chapter 6) 2. M. Abdul Samad and S. K. Sinha, Nanocomposite UHMWPE-CNT polymer coatings for boundary lubrication on aluminium substrates, Tribology Letters, Vol. 38 (2010) 301-311. (part of chapter 8) 3. M. Abdul Samad and S. K. Sinha, Mechanical, thermal and tribological characterization of a UHMWPE film reinforced with carbon nanotubes coated on steel, (under review). (Chapter 5) 4. M. Abdul Samad and Sujeet K. Sinha, “Dry sliding and boundary lubrication performance of a UHMWPE/CNTs nanocomposite coating on steel substrates at elevated temperatures” Wear, 270(2011), p. 395 - 402. (Chapter & part of chapter 8) i Preamble 5. M. Abdul Samad and S. K. Sinha, Effect of counterface and UV radiation on the tribological performance of the UHMWPE/CNTs nanocomposite coating on steel substrates, (under review). (Chapter 7) 6. M. Abdul Samad, N. Satyanarayana and S. K. Sinha, “Effect of Air-Plasma pretreatment of Si substrate on adhesion strength and tribological properties of a UHMWPE film”, Journal of Adhesion Science and Technology, 24(2010), p.2557 – 2570. Conference Oral Presentations 1. M. Abdul Samad, Nalam Satyanarayana and Sujeet K. Sinha, “Effect of the airplasma pre-treatment of the substrate on the tribological properties of UHMWPE thin films coated onto Si”, WTC2009-90213, World Tribology Conference IV, Kyoto, Japan, 6th – 11th September, 2009. 2. M. Abdul Samad, Nalam Satyanarayana and Sujeet K. Sinha, “A Comparative study of two surface modification processes for better adhesion and tribological properties of UHMWPE film deposited on a Si substrate”, Proceedings of the International Conference on Materials for Advanced Technologies 2009 (ICMAT 2009), 2nd July 2009, Singapore. 3. M. Abdul Samad, Nalam Satyanarayana and Sujeet K. Sinha, “Effect of air-plasma pre-treatment of the substrate and the thickness of the film on the tribological performance of UHMWPE\PFPE films steel substrates”, Proceedings of the 2nd International Conference in Advanced Tribology (iCAT), Singapore, 4th Dec, 2008. ii Preamble Conference Poster Presentations 1. M. Abdul Samad and S. K. Sinha, Nanocomposite UHMWPE/CNT polymer coatings for boundary lubrication in sliding components, 4th MRS-S Conference on Advanced Materials, Institute of Materials Research and Engineering (IMRE) during 17th - 19th March 2010. Book Chapters 1. Nalam Satyanarayana, Myo Minn, Mohammed Abdul Samad and Sujeet. K. Sinha, “Tribology of Polymer Coatings / Thin Films”. iii Acknowledgements Acknowledgements I would like to express my sincere thanks and gratitude to many people who directly or indirectly helped me in fulfilling my dream of completing my PhD. First and foremost, I would like to thank my graduate advisor and mentor, Dr. Sujeet Kumar Sinha for his guidance, encouragement and support throughout the period of my PhD. Secondly, my sincere thanks to Dr. Nalam Satyanarayana for his unstinting help and continuous support. I am grateful to the Material Science Lab staff, Mr. Thomas Tan Bah Chee, Mr. Abdul Khalim Bin Abdul, Mr. Ng Hong Wei, Mrs. Zhong Xiang Li, Mr. Maung Aye Thein and Mr. Juraimi Bin Madon for their support and assistance for many experiments. I would also like express my gratitude to the ME dept office staff, Ms. Teo Lay Tin, Sharen and Ms. Thong Siew Fah for their support. I would like to thank all my colleagues in the lab, Minn, Amit, Chandra, Sashi, Srinath and Jahangeer, for their support and friendship. Finally, I would like to thank my family for their support and encouragement, and most of all, my wife, Rana, for having the courage, patience and stamina for supporting me through out my PhD candidature. No words are sufficient to express my gratitude and thanks for her support and understanding. Thanks to my two lovely children, Jawad and Nida for their love, without which the journey of my PhD would have been mundane. Last but not the least I would like to thank GOD and my parents for all their blessings and support. iv Table of Contents Table of Contents Page Number Preamble i Acknowledgements iv Table of Contents v Summary xiv List of Tables xvii List of Figures xviii List of Notations xxvi Chapter Introduction 1.1 Background 1.1.1 Principle of working of a journal bearing 1.1.2 Stribeck curve 1.1.3 Base oils and its categories 1.1.4 Additives 1.2 Present state of lubrication in mechanical components 1.3 Research Objectives 11 1.4 Research methodology in the present work 12 1.5 Significance of the present work 14 Chapter Literature Review 18 2.1 History of Tribology and its significance to Industry 18 2.2 Tribology and Surface Engineering 19 2.3 Low friction coatings for machine elements 20 v Table of Contents 2.4 Polymer Coatings 23 2.5 UHMWPE as a polymer coating 26 2.5.1 Structure and properties of UHMWPE 29 APPROACH 2.6 Surface pre-treatment of the metallic substrates – First approach 32 2.6.1 Air-plasma pre-treatment 33 2.6.2 What is Air-plasma? 34 2.6.3 Advantages of air-plasma treatment 35 2.7 Carbon nanotubes as filler materials – Second approach 35 2.7.1 What are carbon nanotubes? 35 2.7.2 Types of carbon nanotubes and related structures 37 2.7.3 Properties of carbon nanotubes 38 2.7.4 Carbon nanotubes as nanofillers 38 2.8 Providing an overcoat of PFPE – Third approach 43 2.9 Research objectives 44 Chapter Experimental Procedures 46 3.1 Surface Pre-treatment 46 3.1.1 Air-plasma pre-treatment 46 3.1.2 Working principle of air-plasma 46 3.1.3 Air-plasma used in the present research 47 3.2 Surface Characterization and analysis 47 3.2.1 Contact angle measurement 47 3.2.2 Topography measurements with atomic force microscopy vi Table of Contents (AFM) 48 3.2.3 Fourier Transform-Infrared Spectroscopy (FTIR) 49 3.2.4 X-ray Photoelectron Spectroscopy (XPS) 50 3.2.5 X-ray diffraction technique (XRD) 51 3.2.6 FESEM observation of polymer films 51 3.2.7 Surface roughness measurements 52 3.3 Measurement of thickness of the polymer films using field emission Ion beam (FIB) technique 52 3.4 Scratch tests 53 3.5 Thermal characterization of the polymer films 54 3.5.1 Thermogravimetric analysis (TGA) 54 3.5.2 Thermal conductivity measurements 55 3.6 Tribological characterization of the polymer films 3.6.1 Wear and friction tests on flat samples (point contact) 55 55 3.6.2 Wear and Friction tests on Cylindrical samples (Dry and OilLubricated conditions at room temperature) [Line contact] 56 3.6.3 Wear and Friction tests on Cylindrical samples (Dry and Oil-Lubricated conditions at elevated temperatures) [Line contact] 58 3.6.4.1Opertional procedure 59 3.6.4.2 Calibration of the setup 61 3.7 Nano-mechanical property characterization of polymer films using Nanoindentation 63 vii Table of Contents 3.8 Materials and chemical used in the experiments 64 3.8.1 UHMWPE polymer 64 3.8.2 PFPE – perfluoropolyether 64 3.8.3 SWCNTs – Single walled carbon nanotubes 65 Chapter Deposition and Tribology of UHMWPE coating on air-plasma treated tool steel – First Approach 4.1 Background 4.1.1 Main Objective 66 66 67 4.2 Materials 68 4.3 Sample Preparation 68 4.3.1 Pre-treatment procedure for the steel surface 68 4.3.2 Dip-coating of the polymer films on the steel substrate 68 4.4 Experimental procedures 69 4.5 Results 70 4.5.1 Physical and chemical analysis of the UHMWPE film 70 4.5.2 Effect of the air-plasma treatment on adhesion and tribological properties of the UHMWPE film 73 (a) Improvement of surface energy of the steel substrate 73 (b) Surface characterization using XPS 74 (c) Adhesion between the steel substrate and the UHMWPE film 77 (d) Effects of the air-plasma treatment on the tribological properties of the UHMWPE film 80 viii References Bao, Y., Zhang, T and Gawne, D. 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Specialization: Nano-Tribology of polymer films (GPA: 4.33\5) Master of Science in Mechanical Engineering (1994-1997), King Fahd University of Petroleum & Minerals, Dhahran – 31261, KSA. Specialization: Materials and Manufacturing (GPA: 3.75\4) Bachelor of Engineering in Mechanical Engineering (1989-1993), College of Engineering, Osmania University, Hyderabad, India. (Marks: 80%) Certifications Project Management Professional (PMP), 2005 Tutoring Online: Principles & Practices, University of ILLINOIS, USA. 212 Curriculum Vitae Academic/Teaching Experience Research Scholar (2007 - present), Mechanical Engineering Department, National University of Singapore, Singapore Lecturer (1997 – 2007), Mechanical Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran – 31261, KSA. Research Assistant (1994 - 1997), Mechanical Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran – 31261, KSA. Courses Taught Manufacturing Processes – I Manufacturing Processes – II Machine Design – II Materials Science Engineering Drawing and Graphics Teaching Evaluations Quantitative scores always more than on a scale of 10 213 [...]... consumption of lubricants and contribute to lubricants with low additive contents or biodegradable fluids leading to an environmental friendly lubricant technology 1 Chapter 1: Introduction The main focus of the present study is to evaluate the feasibility of using these polymer coatings on metallic substrates, which would be helpful in developing energy efficient and environmental friendly mechanical. .. oil film by forcing the lubricant into the mating surfaces of the shaft and the bearing The oil film provides the journal bearing with its excellent load carrying capacity at higher rotational speeds The pressures encountered in the contact area of journal bearings are significantly less than those generated in rolling bearings This is because of the larger contact area created by the conforming surfaces... the mechanical components such as gears and bearings Therefore, the present study is focused on the main objective of exploring the feasibility of using polymer films as boundary lubricant layers onto metallic substrates modified with appropriate surface pre-treatments, which are expected to enhance the lubrication characteristics and reduce the consumption of harmful additives and the amount of lubricants. .. Summary Single walled carbon nanotubes (SWCNTs) are used as nano filler reinforcements in this study for developing the nanocomposite film Mechanical, thermal and tribological characterizations of the developed nanocomposite coatings are performed Effects of temperature, counterface material and the UV radiations on the tribological performance of the nanocomposite film is also evaluated It is observed that... the improvements in their mechanical and thermal properties xvi List of Tables List of Tables Page Number Table 2.1 Mechanical Properties of UHMWPE in the bulk form [Callister 2003] 30 Table 2.2 Comparison of the mechanical properties of CNTs with other materials [O’ Connell 2006] 38 Table 3.1 Properties of UHMWPE (GUR X 143) polymer 64 Table 4.1 Water contact angle values for the steel surfaces with\without... cycles for a typical run for the bare and UHMWPE film coated steel, with/without air-plasma treatment before the coating of UHMWPE film 3 wt% of UHMWPE was used to obtain the film 81 xix List of Figures Figure 4.6 FIB-Qunta3D image for 5 wt% UHMWPE film on the steel substrate The film thickness value = (Reading) X sin52O 82 Figure 4.7 (a) Coefficient of friction as a function of sliding cycles for different... friction values for each case for a normal load of 60 N and a linear speed of 0.11 ms-1 under dry conditions Figure 9.3 (a) SEM micrograph after the test for the nanocomposite coating 176 without the PFPE overcoat at 80 OC (b) SEM micrograph after the test for the nanocomposite coating without the PFPE overcoat at 120 O C (c) 2-D profile of the worn and the non-worn regions across the interface for the nanocomposite... against the DLC coating for 100 hrs under base oil lubricated conditions (c) Photograph of the counterface flat plate after sliding against the nanocomposite coating for 100 hrs under base oil lubricated conditions xxv List of Notations List of Notations AFM: Atomic force microscopy CNT: Carbon nano tube CSM: Continuous Stiffness Measurement DMEMS: Dynamic microelectromechanical systems FE-SEM: Field... technologists to look for various ways and means to conserve energy on one hand and to invent products which are environmental friendly to reduce pollution and tackle the issue of global warming on the other Every mechanical system has sliding components which experience friction and if proper lubrication is not provided, the component will wear and this will eventually lead to failure For example, in automotive\aerospace... lubrication for many contacting surfaces in mechanical systems are the use of protective coatings on surfaces and the use of lubricants added with appropriate additives Various protective coatings that are in practice are Diamond-like carbon (DLC), several PVD (physical vapor deposition) coatings such as TiAlN, CrAlN, ZrN, ZrC, WC/C, WC: H and TiO2, Al2O3 etc Commonly used additives in the lubricants . ENVIRONMENT-FRIENDLY POLYMERIC BOUNDARY LUBRICANTS FOR MECHANICAL BEARING SYSTEMS MOHAMMED ABDUL SAMAD . NATIONAL UNIVERSITY OF SINGAPORE 2010 ENVIRONMENT-FRIENDLY POLYMERIC BOUNDARY LUBRICANTS FOR MECHANICAL BEARING SYSTEMS MOHAMMED ABDUL SAMAD (B used in the mechanical components such as gears and bearings. Therefore, the present study is focused on the main objective of exploring the feasibility of using polymer films as boundary lubricant