Materials Forming, Machining and Tribology

Jitendra Kumar KatiyarP. RamkumarT. V. V. L. N. RaoJ. Paulo Davim   Editors

Tribology in Materials and Applications

Materials Forming, Machining and Tribology

Series Editor

J. Paulo Davim , Department of Mechanical Engineering, University of Aveiro,Aveiro, Portugal

This series fosters information exchange and discussion on all aspects of materialsforming, machining and tribology. This series focuses on materials forming andmachining processes, namely, metal casting, rolling, forging, extrusion, drawing,sheet metal forming, microforming, hydroforming, thermoforming, incrementalforming, joining, powder metallurgy and ceramics processing, shaping processesfor plastics/composites, traditional machining (turning, drilling, miling, broaching,etc.), non-traditional machining (EDM, ECM, USM, LAM, etc.), grinding andothers abrasive processes, hard part machining, high speed machining, highefficiency machining, micro and nanomachining, among others. The formabilityand machinability of all materials will be considered, including metals, polymers,ceramics, composites, biomaterials, nanomaterials, special materials, etc. The seriescovers the full range of tribological aspects such as surface integrity, friction andwear, lubrication and multiscale tribology including biomedical systems andmanufacturing processes. It also covers modelling and optimization techniquesapplied in materials forming, machining and tribology. Contributions to this bookseries are welcome on all subjects of “green” materials forming, machining andtribology. To submit a proposal or request further information, please contactDr. Mayra Castro, Publishing Editor Applied Sciences, via mayra.castro@springer.com or Professor J. Paulo Davim, Book Series Editor, via pdavim@ua.pt.

More information about this series at http://www.springer.com/series/11181

Jitendra Kumar Katiyar • P. Ramkumar •

T. V. V. L. N. Rao • J. Paulo DavimEditors

Tribology in Materialsand Applications

123

EditorsJitendra Kumar KatiyarDepartment of Mechanical EngineeringSRM Institute of Science and TechnologyKattankulathur CampusChennai, Tamil Nadu, India

P. RamkumarIndian Institute of Technology MadrasChennai, Tamil Nadu, India

T. V. V. L. N. RaoSRM Institute of Science and TechnologyChennai, Tamil Nadu, India

J. Paulo DavimDepartment of Mechanical EngineeringUniversity of AveiroAveiro, Portugal

ISSN 2195-0911 ISSN 2195-092X (electronic)Materials Forming, Machining and TribologyISBN 978-3-030-47450-8 ISBN 978-3-030-47451-5 (eBook)https://doi.org/10.1007/978-3-030-47451-5

© Springer Nature Switzerland AG 2020This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or partof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmissionor information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodology now known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in thispublication does not imply, even in the absence of a specific statement, that such names are exempt fromthe relevant protective laws and regulations and therefore free for general use.The publisher, the authors and the editors are safe to assume that the advice and information in thisbook are believed to be true and accurate at the date of publication. Neither the publisher nor theauthors or the editors give a warranty, express or implied, with respect to the material contained herein orfor any errors or omissions that may have been made. The publisher remains neutral with regard tojurisdictional claims in published maps and institutional affiliations.

This Springer imprint is published by the registered company Springer Nature Switzerland AGThe registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

Tribology is the study of science and technology of two surfaces which are inrelative motion. The relative motion causes friction at the interface, and frictioneventually causes wear of one or both the surfaces. Friction and wear between twobodies can be overcome by the application of lubricants. A number of examplesavailable where tribology is very important. Those are different kinds of bearing,gears, engines, orthopaedic joints, and micro-machines.

The primary objective of this book is to broaden the knowledge of tribology.This book is evolved out of current research trends on tribological performance ofsystems related to nano tribology, rheology, engines, polymer brushes, compositematerials, erosive wear and lubrication. The book deals with enhancing the ideas ontribological properties, the different types of wear phenomenon and lubricationenhancement. Further, the tribological performance of systems, whether nano,micro or macro-scale, depends upon a large number of external parameters andimportant among them are temperature, contact pressure and relative speed. Thus,the book focuses on the theoretical aspects to industrial applications of tribology.

Students, academicians, researchers, practising engineers, who are working inthe field of tribology, design, materials and manufacturing will be interested toenrich their ideas about ongoing tribological research themes.

Chennai, India Jitendra Kumar KatiyarChennai, India P. RamkumarChennai, India T. V. V. L. N. RaoAveiro, Portugal J. Paulo Davim

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Contents

1 Introduction and Applications of Tribology . . . . . . . . . . . . . . . . . . 1Anand Singh Rathaur, Jitendra Kumar Katiyar,and Vinay Kumar Patel

2 Polymer Brush Based Tribology . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Manjesh K. Singh

3 Thin Film Lubrication, Lubricants and Additives . . . . . . . . . . . . . . 33Febin Cyriac and Aydar Akchurin

4 Rheological Behaviour of Hybrid Nanofluids: A Review . . . . . . . . . 77Anuj Kumar Sharma, Rabesh Kumar Singh,Arun Kumar Tiwari, Amit Rai Dixit, and Jitendra Kumar Katiyar

5 Energy Efficient Graphene Based Nano-composite Grease . . . . . . . 95Jayant Singh, Deepak Bhardwaj, and Jitendra Kumar Katiyar

6 Synthesis of Magneto Rheological Fluids Using Nickel Particlesand Study on Their Rheological Behaviour . . . . . . . . . . . . . . . . . . . 109Vikram G. Kamble, H. S. Panda, Shreedhar Kolekar,and T. Jagadeesha

7 Tribology of Intelligent Magnetorheological Materials . . . . . . . . . . 123Rakesh Jinaga, Shreedhar Kolekar, and T. Jagadeesha

8 Nanostructured Layered Materials as Novel Lubricant Additivesfor Tribological Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157Sangita Kumari, Ajay Chouhan, and Om P. Khatri

9 Evolution of Surface Topography During Wear Process . . . . . . . . . 179Deepak K. Prajapati and Mayank Tiwari

10 Wear Characteristics of LASER Cladded Surface Coating . . . . . . . 189Manidipto Mukherjee

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11 Analysis of Journal Bearing with Partial Texture LubricatedUsing Micropolar and Power-Law Fluids . . . . . . . . . . . . . . . . . . . . 211T. V. V. L. N. Rao, Ahmad Majdi Abdul Rani,Norani Muti Mohamed, Hamdan Haji Ya, Mokhtar Awang,and Fakhruldin Mohd Hashim

12 Evaluation of the Effect of Friction in Gear Contact Stresses . . . . . 227Santosh S. Patil and Saravanan Karuppanan

13 Tribo-mechanical Aspects in Micro-electro MechanicalSystems (MEMS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243Anand Singh Rathaur, Jitendra Kumar Katiyar,and Vinay Kumar Patel

14 Analysis of Rotor Stability Supported by Surface Porous LayeredJournal Bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261C. Shravankumar, K. Jegadeesan, and T. V. V. L. N. Rao

15 Tribological Effects of Diesel Engine Oil Contamination on Steeland Hybrid Sliding Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279Ramkumar Penchaliah

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

viii Contents

Editors and Contributors

About the Editors

Dr. Jitendra Kumar Katiyar presently working as aresearch assistant professor, in Department ofMechanical Engineering, SRM Institute of Scienceand Technology, Kattankulathur, Chennai, India. Hisresearch interests include tribology of carbon materials,polymer composites, self-lubricating polymers, lubri-cation tribology and coatings for advanced technolo-gies. He obtained his Ph.D., from the Indian Institute ofTechnology Kanpur in 2017 and masters from the sameinstitution in 2010. He obtained his bachelor degreefrom UPTU, Lucknow, with honours in 2007. He haslife professional memberships such as TribologySociety of India, Malaysian Society of Tribology andThe Indian Society for Technical Education (ISTE). Hehas published more than two dozen papers in reputedjournals and international conferences. His two booksare in press, one is Engineering Thermodynamics forUG level in Khanna Publication and another isAutomotive Tribology in Springer. He actively partic-ipated in so many activities related to tribology.

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Dr. P. Ramkumar presently working as an associateprofessor in the Department of MechanicalEngineering, IIT Madras. Prior to coming to IITMadras, he was an associate professor at SSNCollege of Engineering, Chennai. He received hisB.E. in Mechanical Engineering from College ofEngineering, Guindy, Anna University, and hisM.Tech. (Industrial Tribology) from IIT Madras. Later,he pursued Ph.D. from University of Southampton, UK,and did his postdoctoral fellowship in University ofLeicester, UK. His research interests are in the field oftribology, including developing new materials andcoatings for engine tribology, nano-lubrication, gearboxdesign, electrostatic condition monitoring and develop-ing new materials for brake application.

Dr. T. V. V. L. N. Rao is currently a research associateprofessor in School of Mechanical Engineering at SRMInstitute of Science and Technology, since December2017. He received PhD in tribology of fluid filmbearings from the Indian Institute of Technology Delhiin 2000 and M.Tech. in Mechanical ManufacturingTechnology from the National Institute of TechnologyCalicut in 1994. Prior to joining SRM, he served as afaculty member at LNMIIT, Universiti TeknologiPETRONAS, and BITS at Pilani and Dubai campuses.He has authored over 100 publications. He is a memberof Society of Tribologists and Lubrication Engineers,Malaysian Tribology Society and Tribology Society ofIndia. His research interests are in tribology, lubricationand bearings.

Prof. J. Paulo Davim received his Ph.D. degree inMechanical Engineering in 1997, M.Sc. degree inMechanical Engineering (materials and manufacturingprocesses) in 1991, Mechanical Engineering degree(5 years) in 1986, from the University of Porto (FEUP),the Aggregate title (Full Habilitation) from theUniversity of Coimbra in 2005 and the D.Sc. (HigherDoctorate) from London Metropolitan University in2013. He is a senior chartered engineer by thePortuguese Institution of Engineers with an MBA andSpecialist titles in Engineering and IndustrialManagement as well as in Metrology. He is also EurIng by FEANI-Brussels and Fellow (FIET) of

x Editors and Contributors

IET-London. Currently, he is a professor at theDepartment of Mechanical Engineering of theUniversity of Aveiro, Portugal. He is also distinguishedas a honorary professor in several universities/colleges.He has more than 30 years of teaching and researchexperience in Manufacturing, Materials, Mechanicaland Industrial Engineering, with special emphasis onmachining and tribology. He has also interested inmanagement, engineering education and higher educa-tion for sustainability. He has guided large numbers ofpostdoc, Ph.D. and master’s students as well as hascoordinated and participated in several financedresearch projects. He has received several scientificawards and honours. He has worked as an evaluator ofprojects for ERC-European Research Council and otherinternational research agencies as well as examiner ofPh.D. thesis for many universities in different countries.He is the editor in chief of several international journals,guest editor of journals, books editor, book series editorand scientific advisory for many international journalsand conferences. Presently, he is an editorial boardmember of 30 international journals and acts as areviewer for more than 100 prestigious Web of Sciencejournals. In addition, he has also published as editor(and co-editor) more than 125 books and as an author(and co-author) more than ten books, 80 chapters and400 articles in journals and conferences (more than 250articles in journals indexed in Web of Science corecollection/h-index 55+/9500+ citations, SCOPUS/h-index 59+/11500+ citations, Google Scholar/h-index76+/19000+).

Contributors

Aydar Akchurin ASML, Veldhoven, The Netherlands

Mokhtar Awang Department of Mechanical Engineering, Universiti TeknologiPETRONAS, Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia

Deepak Bhardwaj Department of Mechanical and Automation Engineering,Dr. Akhilesh Das Gupta Institute of Technology and Management, New Delhi,India

Ajay Chouhan CSIR-Indian Institute of Petroleum, Dehradun, India

Editors and Contributors xi

Febin Cyriac Institute of Chemical and Engineering Sciences, A*STAR,Singapore, Singapore

Amit Rai Dixit Department of Mechanical Engineering, Indian Institute ofTechnology (ISM), Dhanbad, India

Fakhruldin Mohd Hashim Department of Mechanical Engineering, UniversitiTeknologi PETRONAS, Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia

T. Jagadeesha Department of Mechanical Engineering, National Institute ofTechnology, Calicut, Kerala, India

K. Jegadeesan Department of Mechanical Engineering, SRM Institute of Scienceand Technology, Kattankulathur, India

Rakesh Jinaga Department of Mechanical Engineering, National Institute ofTechnology, NIT Calicut, Calicut, Kerala, India

Vikram G. Kamble Leibniz Institute for Polymer Research, Dresden, Germany

Saravanan Karuppanan Department of Mechanical Engineering, UniversitiTeknologi PETRONAS, Bandar Seri Iskandar, Perak, Malaysia

Jitendra Kumar Katiyar Department of Mechanical Engineering, SRM Instituteof Science and Technology, Kattankulathur Campus, Chennai, Tamil Nadu, India

Om P. Khatri CSIR-Indian Institute of Petroleum, Dehradun, India

Shreedhar Kolekar Department of Mechanical Engineering, SCOEM Satara,Satara, Maharashtra, India;Department of Mechanical Engineering, National Institute of Technology, NITCalicut, Calicut, Kerala, India

Sangita Kumari CSIR-Indian Institute of Petroleum, Dehradun, India

Norani Muti Mohamed Department of Fundamental and Applied Sciences,Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak Darul Ridzuan,Malaysia

Manidipto Mukherjee CAMM, CSIR-Central Mechanical Engineering ResearchInstitute, Durgapur, West Bengal, India

H. S. Panda Ballistic Center, Proof & Experimental Establishment (PXE) DefenceR & D Organization, Balasore, Odisha, India

Vinay Kumar Patel Department of Mechanical Engineering, Govind BallabhPant Institute of Engineering and Technology Ghurdauri, Pauri Garhwal,Uttarakhand, India

xii Editors and Contributors

Santosh S. Patil Department of Mechanical Engineering, Manipal UniversityJaipur, Jaipur, India

Ramkumar Penchaliah Machine Design Section, Department of MechanicalEngineering, Indian Institute of Technology Madras, Chennai, India

Deepak K. Prajapati Department of Mechanical Engineering, Indian Institute ofTechnology, Patna, India

Ahmad Majdi Abdul Rani Department of Mechanical Engineering, UniversitiTeknologi PETRONAS, Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia

T. V. V. L. N. Rao Department of Mechanical Engineering, SRM Institute ofScience and Technology, Kattankulathur, India

Anand Singh Rathaur Department of Mechanical Engineering, Govind BallabhPant Institute of Engineering and Technology Ghurdauri, Pauri Garhwal,Uttarakhand, India

Anuj Kumar Sharma Mechatronics, Centre for Advanced Studies, Dr. APJAbdul Kalam Technical University, Lucknow, India

C. Shravankumar Department of Mechanical Engineering, SRM Institute ofScience and Technology, Kattankulathur, India

Jayant Singh Department of Mechanical and Automation Engineering,Dr. Akhilesh Das Gupta Institute of Technology and Management, New Delhi,India

Manjesh K. Singh Indian Institute of Technology, Kanpur, India

Rabesh Kumar Singh Mechatronics, Centre for Advanced Studies, Dr. APJAbdul Kalam Technical University, Lucknow, India

Arun Kumar Tiwari Department of Mechanical Engineering, Institute ofEngineering and Technology, Dr. APJ Abdul Kalam Technical University,Lucknow, India

Mayank Tiwari Department of Mechanical Engineering, Indian Institute ofTechnology, Patna, India

Hamdan Haji Ya Department of Mechanical Engineering, Universiti TeknologiPETRONAS, Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia

Editors and Contributors xiii

Chapter 1Introduction and Applicationsof Tribology

Anand Singh Rathaur, Jitendra Kumar Katiyar , and Vinay Kumar Patel

Abstract Present chapter describes about the basic terms involve in tribology andtheir application in different fields. When two bodies are in a relative motion, at theinterface rubbing occurred, due to rubbing, friction produced and friction eventuallycauses the wear on one or both the materials. Therefore, the role of lubricant comesinto the picture. Friction and wear between two bodies can be overcome by theapplication of lubricants. In the environment, air and water may act as a lubricantto reduce friction and improve wear resistant property. Furthermore, friction andwear performance of any structure either nano, micro or macro-scale is dependsupon a large member of external parameters and important among them are relativespeed, temperature, and contact pressure. This chapter also describes the importantapplication of tribology in brief.

1.1 Introduction

The word “Tribology” has been derived from the Greek word “Tribos” which means“rubbing” or to rub and suffix “Ology” means “the study of”. Hence, tribology is“the study of rubbing of two materials” [1]. Tribology involves the study and theapplications of the principles of friction, wear, adhesion, lubrication and surfacemodification which is diagrammatically represented in Fig. 1.1.

The relative motion of two bodies cause friction at the interface and this eventu-ally origins wear on either one or both the bodies. Friction and wear between twobodies can be overcome by the application of lubricants. In the environment, air and

A. S. Rathaur · V. K. PatelDepartment of Mechanical Engineering, Govind Ballabh Pant Institute of Engineering andTechnology Ghurdauri, Pauri Garhwal, Uttarakhand 246194, India

J. K. Katiyar (B)Department of Mechanical Engineering, SRM Institute of Science and Technology,Kattankulathur Campus, Chennai, Tamil Nadu 603203, Indiae-mail: jitendrv@srmist.edu.in

© Springer Nature Switzerland AG 2020J. K. Katiyar et al. (eds.), Tribology in Materials and Applications,Materials Forming, Machining and Tribology,https://doi.org/10.1007/978-3-030-47451-5_1

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2 A. S. Rathaur et al.

Tribology

Friction Wear Adhesion Lubrication Surface Modification Erosion

Fig. 1.1 Structure of tribology

water may act as a lubricant to decrease friction and improve wear resistant prop-erty. Comprehensive explanation of friction, wear and lubrication is specified in thefollowing sections.

1.1.1 Friction

The friction is known as a resistance force experienced by the different surfaceslike solid surface, fluid layers etc. in relative motion which is shown in Fig. 1.2.Friction is divided into two categories, dry and fluid film friction. Dry friction isdefined when there are two solid surfaces sliding against each other and energy iscompletely intemperate between the surfaces. Further, it is again subdivided into twoparts; static and kinetic friction.

When the energy dissipation taken place within a thin liquid layer between thetwo surfaces then this type of friction is known as fluid film friction. Essentially,friction is a result of the energy dissipation at the interface which can take placein the form of material deformation, asperity-asperity interactions, fracture, viscousflow of fluid film, interatomic interactions etc.

Fig. 1.2 Schematic offriction

1 Introduction and Applications of Tribology 3

1.1.2 Wear

Because of rubbing action in relative motion of solid bodies, material is continuouslylost at the interface. This phenomenon of loss of material is known as Wear. Oneexample of wear of the surface is shown in Fig. 1.3. Form the schematic; it is clearlyobserved that bottom surface have initially V-notches and top surface rubbing overit, resulting in the abrasion of V-notches. Wear processes are classified into varioustypes such as adhesive wear, abrasive wear, surface fatigue and erosion which arefurther classified into sub groups as shown in Fig. 1.4 [2]. Detailed description ofwear mechanisms are given in the following sections.

Fig. 1.3 Schematic of wear

Fig. 1.4 Classification of wear processes. Reproduced with permission of Ref. [2]

4 A. S. Rathaur et al.

Fig. 1.5 Types of abrasive wear: micro-cutting, fracture, fatigue and grain pull-out.Reproduced with permission of Ref. [3]

1.1.2.1 Abrasive Wear

When two bodies come into a direct contact in which one is soft and another one ishard then abrasive wear occurred. Further, it might also confirm that hard particlesare existing at the interface as a contamination or as “third body”. The third bodydefined as a wear debris or oxidized particles which is trapped at the interface. Afew examples of abrasive wear are shown in Fig. 1.5 which schematically show thegeneration of wear particles by the processes such as micro-cutting, micro-fracture,pull-out of individual grains or accelerated fatigue by repeated deformations. Theactual micrograph of abrasive wear is shown in Fig. 1.6.

1.1.2.2 Adhesive Wear

When large forces applied on interface of two bodies then materials at the interfaceexperience plastic deformation and removal in the form of highly deformed flakes.This type of wear is known as adhesive wear. The high amount of adhesive forcescan also lead to cold welding at confined contact points. The cold-welded part canalso tear-off local material. Adhesive wear can happen in bearing surfaces made ofmetals where lubrication is not present or not effective. The Mechanism of adhesivewear is shown in Fig. 1.7 and the actual micrograph of adhesive wear is shown inFig. 1.8.

1 Introduction and Applications of Tribology 5

Fig. 1.6 SU-8/graphite composite after tribotest at 600 RPM and 2 N applied load

Fig. 1.7 Mechanism of adhesive wear. Reproduced with permission of Ref. [4]

1.1.2.3 Erosive Wear

When the deformation on the solid surface might yield because of the impact of avery small solid or liquid particle and if such impressions are continual over andover again then there will be elimination of local material which is known as erosivewear. It depends upon material of particle (hardness), the impingement angle, theimpact velocity, and the size of particle. The mechanism of erosive wear is illustratedin Fig. 1.9.

1.1.2.4 Fatigue Wear

Fatigue wear occurs primarily in rolling contact and in sliding with lubrication. Itis a result of non-conformal contact where the contact stress is large but the shear

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Fig. 1.8 SU-8/graphene composite after tribotest at 200 RPM and 1.5 N applied load

stress is low. Cracks are nucleated in the subsurface which than grow to the surfacemaking wear particles. The mechanism of fatigue wear is illustrated from Fig. 1.10.

1.1.3 Lubrication

Lubrication is very important agent which reduce the friction and wear between twosurfaces in relative motion. The correct lubrication is chosen by the application andcondition where it is applying. The main functions of lubricants are to control thefriction and wear, interfacial temperature, and corrosion. Also, it can be used forremoving of unwanted particles between interface and form a fluid film to diminishthe friction and wear. There are various parameters which are affected the act oflubricant. These are its physical, chemical, and rheological properties. Apart fromthat, it also depends on the some external parameters levied such as surface temper-ature, pressure between contacts, and relative speed. Because of the development offluid film at the counterface, There are various lubrication regimes are defined whichare

1. Boundary lubrication2. Mixed Lubrication3. Elasto-hydrodynamic lubrication4. Hydrodynamic Lubrication.

1 Introduction and Applications of Tribology 7

Fig. 1.9 Possible mechanisms of erosion; a abrasion at low impact angles, b surface fatigue dur-ing low speed, high impingement angle impact, c brittle fracture or multiple plastic deformationduring medium speed, large impingement angle impact, d surface melting at high impact speeds,e macroscopic erosion with secondary effects. Reproduced with permission of Ref. [3]

Fig. 1.10 Mechanism of fatigue wear. Reproduced with permission of Ref. [4]

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Fig. 1.11 Stribeck curve and mechanism of lubrication. Reproduced with permission of Ref. [6]

The mechanisms of lubrication are illustrated in Fig. 1.11. The lubrication isprovided by either liquid (e.g. natural oil, organic oil and inorganic oil) or solid (e.g.Grease, graphite, graphene etc.).

The liquid lubrication can be studied by a plot known as the “Stribeck curve” or“Stribeck-Hersey curve”. The “Stribeck curve” or “Stribeck–Hersey curve” (namedafter Richard Stribeck and Mayo D. Hersey) (shown in Fig. 1.11) was developed inthe first half of the twentieth century to categorize the friction properties betweentwo liquid lubricated surfaces [5]. The curve is plotted with friction coefficient as afunction of a parameter given by hV /P; where h is the viscosity of the lubricant, V isthe relative velocity and P is the contact pressure. The Stribeck curve contains threemain regimes known as Boundary lubrication, Mixed lubrication and Hydrodynamiclubrication (HL) with Elasto-hydrodynamic lubrication (EHL) regimes in betweenmixed and HL regimes.

The boundary lubrication regime is characterized by solid-solid interactions eventhough there is presence of liquid lubricant. This condition exits when the contactpressure is high and/or the relative speed is low. The hydrodynamic lubricationregime is characterized by whole separation of the two mating surfaces by a thinlayer of lubricant. This thin lubricant film is maintained by the fluid as it entersthe minimum gap between the two mating parts. The smallest film thickness mustbe greater that the surfaces roughness. The mixed lubrication regime is categorisedby partial solid-solid interaction at asperity level with partial fluid film separation.The Elasto-hydrodynamic lubrication (EHL) is a distinct case of HL where there iselastic deformation of one or both solid surfaces in contact and thus facilitating theformation of a fluid film in-between. The coefficient of friction is high when there is

1 Introduction and Applications of Tribology 9

Fig. 1.12 Factors determining the wear and friction behavior. Reproduced with permission of Ref.[7]

solid-solid interaction at asperity level as in the boundary lubrication regime. It canbe extremely low (in the range of 0.001) in the hydrodynamic film regime.

1.1.4 Factors Affecting Tribology Performance

Figure 1.12 illustrates the factors which disturb the performance of any tribologicalsystem.

1.1.5 Tribology in Materials

Materials play a very important parts in technological development of any coun-try. The driving force behind any advancement in any materials are various social,

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Table 1.1 Tribologicalcharacteristic in relation tomaterial types

Mass forces Fpolymer < Fceramics < Fmetal

Hertzian pressure Ppolymer < Pceramics < Pmetal

Friction induced temperatureincreases

Tmetal < Tpolymer < Tceramics

Adhesion energy (surfacetension)

Adceramics < Admetal <Adpolymer

Abrasion Abceramics < Abmetal <Abpolymer

Tribo-chemical reactivity Rpolymer < Rceramics < Rmetal

Reproduced with permission of Ref. [8]

environmental and technological requirementswhich provides reliability of any engi-neering system, durability of any products, higher efficiency, light weight and highstrength structure, higher productivity and miniaturization of components [8]. Fur-thermore, developed new materials are showing very promising use in various appli-cations because friction and wear is directly related to the properties of materialswhich is shown in Table 1.1.

1.1.6 Applications of Tribology

The tribological performance of any system either nano, micro or macro-scale isdepends upon a large member of external parameters such as temperature, contactpressure and relative speed etc. There are various examples, where tribology is veryimperative. These are various kinds of bearings, gears, engines, orthopaedic jointsand micro-machines. The brief description is given in following sections

1.1.6.1 Bio-tribology

Theword bio-tribology, first time introduced byDowson in 1970 [9]. It deals with thetribological aspects related to the biological systems. This is a promptly rising area oftribology and spreads well outside the predictable boundaries. These systems includean extensive range of synthetic materials and natural tissues, including cartilage,blood vessels, heart, tendons, ligaments, and skin. The materials used in biologicalsystems work in a complex cooperative biological environments. The researchersincorporate concepts of friction, wear, and lubrication of these biological surfacesin numerous applications, such as the design of joints and prosthetic devices, thewear of plates and screws in bone fracture repair, wear of denture and restorativematerials, wear of replacement heart valves, and even the tribology of contact lenses.

1 Introduction and Applications of Tribology 11

1.1.6.2 Micro/Nano Tribology

Micro Electro-Mechanical System (MEMS)/Nano Electro-Mechanical System(NEMS) devices continue to find new applications in technology. Some of the suc-cessful MEMS are micro-reservoir, micro-pumps, cantilever, micro-pillars for hold-ing the mirror devices in projectors, rotors, channels, valves, sensors etc. In majorityof the cases, polycrystalline silicon is used as the structural material for MEMSfabrication because of the micro fabrication process knowledge acquired from thesemi-conductor industry. Recently, polymermaterials have also been used forMEMSfabrication. Some of the polymers used as structural material are acrylic (PMMA),PDMSand the epoxy-based SU-8. SU-8 is a negative photoresist which isUVcurableand has excellent mechanical properties over other polymers. However, when com-pared to silicon, SU-8 is mechanically inferior. SU-8 has excellent thermal stability.Despitemany processing advantages, the bulkmechanical and tribological propertiesof SU-8 are the main limitations in making it is a versatile MEMS material.

The development of sophisticated scanning probe technologies and computa-tional methods has given upswing to the field of nanotribology for examinations ofprocesses at the atomic, molecular, and microscopic scale. Nano tribological stud-ies are facilitating to develop important understanding of surface counterfaces inmicro/nanostructures used in a variety of current applications.

Some of these applications comprise chemical and biodetectors, advanced drugdelivery systems, information recording layers, molecular sieves, systems on a chip,nanoparticle reinforced materials, and a new generation of lasers.

1.1.6.3 Wind Turbines

Wind turbines are widely used for power generation using non-renewable energysuch as wind. It is a feasible substitute energy resource. While they have madeexpansions in trustworthiness in the past decade, they are subject to friction andwear problems. Due to these problems, it is difficult and costly to repair. Further,it can drastically reduce their predictable lifecycles. Two key areas of concern arereliability of gearboxes and turbine lubrication. To report these problems, extensivestudies of lubricants have been carried out which are used in wind-turbine gearboxesand hydraulic systems such as the blade pitch control, drive train brake subsystems,and bearings to expand the turbine reliability in thrilling environments. The possiblefailure modes in wind turbines are micro pitting (that is also called frosting) becauseof high tangential stresses, scuffing because of sever plastic deformation, electricdischarge damage because of faulty insulation andmicrostructural alteration (i.e. alsoknown as white etching area cracks) because of the insufficient design considerationof bearing [10].

12 A. S. Rathaur et al.

1.1.6.4 Nano-lubricants

One of the recent areas in the arena of tribology is nano-lubricants, also known asnano fluids. The nano lubricants got its name from its composition i.e. nano particlesdispersed in lubricants. It has been observed that the tribological properties of alubricant enhanced significantly with the addition of nano particles. These nanoparticles added lubricants protects the parent materials from contact with each otherin either of the followingmechanisms: formation of a protective layer over the parentmaterial, filling the crevices, polishing the mating pairs or acting as spacers in theform of rollers between the mating parts.

1.1.6.5 Automotive Tribology

Now a days the automotive technologies are developing very fast. The main concernin these technologies are customer satisfaction and environmental protection. Auto-mobile consists various mechanisms which shake the efficiency of engine mostlysuch as bearing, piston ring, valve train and crank shaft etc. to increase the effi-ciency of automobile, various researchers had tried numerous methods which arevery effective such as surface texturing, surface coating, modification in lubricantetc. for improving the efficiency of engine. Also, they concluded that the efficiencyof any engine is mostly affected by friction.

1.1.6.6 Bearings

In bearing industries, steel is most commonly used material. The industries are fab-ricating various kinds of bearings such as ball bearing, roller bearing and thrustbearing etc. These bearings have been used in diverse applications of automobile;power driven machine etc. [11]. The coefficient of friction in steel on steel interfacehas revealed a very high (~0.7–1.0) [12]. Due to very high friction coefficient, a sub-stantial damage on the surfaces and subsurface of bearing balls occurs. These are inthe form of crack propagation, cavity formation etc. which affects the life of bearingdestructively. Therefore, the reduction in friction coefficient is extremely desirable.To attain low coefficient of friction, the enterprises are exhausting excessive quantityof lubricant which distresses the environment and produces the health risk. Hence,the scientist and researchers have moved their devotion towards some alternate solu-tions which can reduce the consumption of lubricant. Because of that reason, thefew researchers invented a self-lubricating polymer composite coating using solidfriction modifier or additives which obsessed lower coefficient of friction [13, 14].Further, researchers are trying to develop polymer composite bearing balls whichis the one step ahead in reduction of lubrication. These polymer composite bearingballs have shown lower friction coefficient as well as higher wear resistance at lowload [15].

1 Introduction and Applications of Tribology 13

1.1.6.7 Green Tribology

The concept of “green tribology” was also introduced by Jost, who defined it as,“The science and technology of the tribological aspects of ecological balance andof environmental and biological impacts.” There are a numeral of complicationswhich can be addressed using green tribology. The unambiguous field of green orenvironment-friendly tribology highlights the features of mating surfaces in relativemotion. This is having importance for energy or environmental sustainability orwhich have influence upon today’s environment.

In this field, Nosonovsky and Bhushan suggested the 12 principles [16] as theminimization of (1) friction and (2) wear, (3) the reduction or complete eliminationof lubrication, including self-lubrication, (4) natural and (5) biodegradable lubri-cation, (6) using sustainable chemistry and engineering principles, (7) biomimeticapproaches, (8) surface texturing, (9) environmental implications of coatings, (10)real-time monitoring, (11) design for degradation, and (12) sustainable energyapplications.

1.2 Summary

Tribology is the study of science and technology of two rubbing systems. Due torubbing, friction occurs which causes wear at the interface. To reduce these effectfrom interface, a protective layer of lubricant is applied. Therefore, the developmentof materials are very important in any tribological systems because friction andwear is widely affected by the properties of bulk materials. According to the useof materials, there are various applications of tribology. Therefore, tribology is alsoknown as interdisciplinary branch of the science.

References

1. D. Duncan,History of Tribology, 2nd edn. (Professional Engineering Publishing, 1997). ISBN1-86058-070-X

2. J.A. Williams, Wear and wear particles—some fundamentals. Tribol. Int. 38(10), 863–870(2005)

3. G.W. Stachowiak, A.W. Batchelor, Engineering tribology: abrasive, erosive and cavitationwear. Tribol. Ser. 24, 557–612 (1993)

4. A. Abdelbary,Wear of Polymers and Composites: Polymer Tribology (Elsevier, 2013), pp. 1–365. R. Stribeck, Die wesentlichen Eigenschaften der Gleit- und Rollenlager (Characteristics of

plain and roller bearings), Zeit. des VDI 46 (1902)6. L. Burstein, Lubrication and Roughness, Tribology for Engineers, A Practical Guide (Elsevier,

2011)7. T. Lesniewski, S. Krawiec, The effect of ball hardness on four-ball wear test results. Wear

264(7–8), 662–670 (2008)8. H. Czichos, D. Klaffke, E. Santner, M. Woydt, Advances in tribology: the materials point of

view. Wear 190, 155–161 (1995)

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9. D. Dowson, V. Wright, Bio-tribology, in Proceeding of the Conference on the Rheology ofLubrication (The Institute of Petroleum, The Institution of Mechanical Engineers, and theBritish Society of Rheology, London, 1973), pp. 81–88

10. A. Greco, S. Sheng, J. Keller, A. Erdemira, Material wear and fatigue in wind turbine ss. Wear302(1–2), 1583–1591 (2013)

11. H. Bangert, C. Eisenmenger-Sittner, A. Bergauer, Deposition and structural properties of two-component metal coatings for tribological applications. Surf. Coat. Technol. 80(1–2), 162–170(1996)

12. B. Bilyeu, W. Brostow, K.P. Menard, Epoxy thermosets and their applications I: chemicalstructures and applications’. J. Mater. Educ. 21(5–6), 281–286 (1999)

13. A.S. Rathaur, J.K. Katiyar, V.K. Patel, S. Bhaumik, A.K. Sharma, A comparative study oftribological and mechanical properties of composite polymer coatings on bearing steel. Int. J.Surf. Sci. Eng. 12(5/6), 379–401 (2018)

14. J.K. Katiyar, S.K. Sinha, A. Kumar, In situ lubrication of SU-8/Talc composite with base oil(SN150) and perfluoropolyether as fillers. Tribol. Lett. 64(1), 5 (2016)

15. A.S. Rathaur, J.K. Katiyar, V.K. Patel, Tribo-mechanical properties of graphite/talc modifiedpolymer composite bearing balls. Mater. Res. Express 7(1), 15305 (2019)

16. M.Nosonovsky, B.Bhushan,Green tribology: principles, research areas and challenges. Philos.Trans. R. Soc. A 368, 4677–4694 (2010)

Chapter 2Polymer Brush Based Tribology

Manjesh K. Singh

Abstract Polymer chains with one of their ends grafted on a surface, stretch out in agood solvent to take a brush-like formationwhen the grafting density,ρg > 1/

(πR2

g

),

whereRg is the radius of gyration of a chain in a good solvent. The equilibrium heightof such a polymer brush is larger than the unperturbed size (Rg) of the correspondingpolymer chain in a bulk solution. Polymer brushes find applications in the fields oftribology, rheology, biology and colloid-stabilization. Polymer brush based tribologyis a recent attempt to mimic glycoproteins based lubrication found in nature. Highercoefficients of friction are observed due to as perity contact when hard surfacesare brought in contact and sheared against each-other. In contrast, when polymer-brush bearing surfaces are brought in contact with each-other and sheared in thepresence of a good-solvent, much lower coefficients of friction are observed. Due toentropic reasons opposing polymer brushes avoid inter-digitation even under highcompression enabling development of a thin fluid film between the brushes. Such aformation helps polymer brushes to support relatively high applied normal loadwhilethe thin fluid film in-between helps in reducing the friction. Tribological behavior ofpolymer brushes can be tuned by changing the grafting-density (ρg), chain-length(Lc), chain-stiffness (Kb), solvent-quality and cross-linking of chains. Possibility ofdesigning lubricant with specific tribological properties make polymer-brushes aninteresting topic of research. In this chapter wewill go through the effects of differentpolymer-brush architectures on the tribological behavior of polymer brushes.

2.1 Introduction

Nature has a very complex method of lubricating sliding surfaces in an aque-ous medium with the help of bio-polymers such as glycoproteins. In recent timeshumankind has attempted to understand and imitate this using polymer brushes.

M. K. Singh (B)Indian Institute of Technology, Kanpur, Indiae-mail: manjesh@iitk.ac.in

© Springer Nature Switzerland AG 2020J. K. Katiyar et al. (eds.), Tribology in Materials and Applications,Materials Forming, Machining and Tribology,https://doi.org/10.1007/978-3-030-47451-5_2

15

16 M. K. Singh

Fig. 2.1 Schematic of polymer brushes

When polymer chains are grafted to any surface at a sufficiently high grafting den-sity (ρg), in presence of a good solvent, the chains stretch out to form a brush-likestructure known as polymer brush.

The structure of grafted polymer chains depends on the grafting density (ρg) andsolvent-quality. Figure 2.1 shows the different forms grafted chains take at differentgrafting densities (ρ) in presence of good and bad solvents. When the distance (d0)between grafting sites of adjacent polymer chains is greater than radius of gyration(Rg) of the polymer chains in the bulk solution, they takemushroom-like form in goodsolvent and pan-cake like form in bad solvent. When d0 ≈ Rg, polymer chains takesemi-stretched form in a good solvent whereas in a bad solvent, chains form clusters.When d0 < Rg, the grafted polymer chains stretch out to form a polymer brush in agood solvent, whereas the chains form a homogenous layer in a bad solvent. Hencewe see that the critical grafting density (ρ∗

g ) to form a brush in a good solvent is

ρg ∼ d−20 < R−2

g [1–3].

2.1.1 Preparation of Polymer Brushes

Polymer brushes are synthesised using “garfting-from” and “grafting-to” approaches.Both the methods have advantages and limitations (Fig. 2.2).

2 Polymer Brush Based Tribology 17

Fig. 2.2 Method to synthesis polymer brushes: a “grafting-from”, and b “grafting-to”

In “grafting-from” approach, initiators are attached to the grafting surface andpolymer chains are grown out of the initiators to form polymer brushes. In the“grafting-to” approach, solutions containing polymer chains is poured on the graftingsurface and chains get attached by one end to the grafting surface to form polymerbrushes. Higher grafting densities can be achieved using “grafting-from” approachin comparison to the “grafting-to” method. The latter has limitations in achievinghigher grafting density because already adsorbed chains block other chains in thesolution from reaching the grafting surface. The advantage of grafting-to approach isthat chain detached (worn-off) from the grafting surface during sliding are replacedby other chains present in the solution, so this method has a “self-healing” character-istics. In recent times “grafting-from” approach has become more popular because itgives flexibility by modulating the feed monomers to synthesize block co-polymersbased brushes and switching on or off the crosslinking during growth to synthesizelayered structures of polymer brushes and gels (crosslinked polymer brushes).

2.2 Polymer Brush Mediated Lubrication

Tribological behavior of polymer brushes have been studied extensively using exper-iments and simulations to understand the origin of frictional forces at different loadsand shear rates. Boundary and hydrodynamic lubrication have been established andstudied [4]. Figure 2.3a shows the schematic of brush-against-brush and brush-against-wall systems. The density profile of brush-against-brush system (Fig. 2.3b)shows that as the density of polymers deplete moving away from the grafting sur-faces, solvent density goes up and at the point where monomer-density is minimum,solvent density is maximum [5]. Hence, an effective fluid layer is created betweenthe two opposite brushes (or between brush and wall in brush-against-wall system).