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Molybdenum Disulphide Lubrication
148
Book reviews / Tribology International 33 (2000) 143–149
Instruments) is lacking only in the absence of any References list. The Chemically Deposited Coatings section is dedicated to two papers on galvannealing processes for steel sheet. In the Chemical Vapour Deposition section, three of the four papers deal with a combustion-based process whose primary purpose is to provide corrosion protection for a variety of metals. Given that there is a section headed Corrosion Resistant Coatings, it is clear that corrosion is an important theme within the book. Having said that, one of the papers in the latter section seems misplaced as it is actually concerned with applications of plasma source ion implantation for metal forming tools within General Motors. The modelling section, likewise, is diverse in content. One paper deals with finite element modelling of contact stresses on coated and uncoated aluminium substrates, whilst the other deals with simulation of growth kinetics in gas nitriding. This latter paper, from authors in Canada and Poland, won the Best Paper Award at the Conference. The sections which will probably be of greatest interest to readers of Tribology International are those dealing with Wear Resistant Coatings and Ultra Hard Coatings. Again, the topics covered in these sections are very wide-ranging. In the former section, papers include subjects such as the improved rolling contact fatigue behaviour of a carburised stainless steel material, the use of ion plated silver and gold to enhance the tribological performance of Si3N4 and SiC materials, the tribological behaviour of silicon-doped diamond-like-carbon (DLC) coatings and the synthesis and properties of crystalline carbon nitride thin films deposited using a ZrN multilayering approach. There is also an interesting paper on self-replenishing solid lubricant films on boron carbide (B4C) from the Argonne National Laboratory in the USA. A couple of papers in this section deal specifically with wear mechanisms. One, from the CNRS laboratory in Mulhouse, France, deals with the kinetics of third body formation (including transfer film build-up). The second, from researchers in Papua New Guinea and Texas A&M University, USA, deals with an investigation of mechanisms in compound wear (i.e. where sliding and impact motions occur simultaneously). Examples of topics in the section on Ultra Hard Coatings include carbon nitride films produced by CO2 laser pyrolysis, sputtered amorphous carbon films, DLC nanocomposite barrier films and metal-doped DLC coatings. A paper from North Carolina State University details the properties of several hard biocompatible coatings and discusses their advantages and limitations (especially with regard to adhesion on prosthetic devices). The laser processing section reflects the variety of uses to which lasers are now put. For example, there is a paper on laser gas alloying of Ti-6Al-4V to form a TiN coating, and another on the control of the surface
structure of graphite fibres for improved composite interfacial properties. These papers tend to emphasise the processes, rather than the tribological properties of the surfaces produced. Similarly many of the papers in the Thermal Barrier Coatings section are concerned with the relationship between process parameters and coating microstructure. The final section, entitled Applications of Coatings, is not the only place in the book where applications-related papers are to be found. It does though contain several papers which will be of particular interest to tribologists. For example, a paper from researchers at the National Science Foundation and Cummins Engine Corporation in the USA discusses the transfer of several novel surface engineering techniques from the laboratory into industrial practice. Another paper, from Thermal Spray Technologies Inc, discusses several interesting case studies of thermal sprayed coating for wear parts such as lawnmower break clutches, sail winches and even bicycle rims. Another paper, from General Motors, discusses the use of thermal spraying for molten metal handling tools and moulds. Overall the book provides valuable material for those involved in developing coatings and those seeking to apply them more effectively. Tribologists will find much of interest within its covers. Professor Allan Matthews The Research Centre in Surface Engineering, The University of Hull, Hull HU6 7RX, UK PII: S 0 3 0 1 - 6 7 9 X ( 0 0 ) 0 0 0 1 9 - 0
Molybdenum Disulphide Lubrication A.R. Lansdown, Tribology series, 35, D. Dowson (Ed.) 1999, pp. 380 This book analyses the various aspects of molybdenum disulphide lubrication in general. It is both a practical guide and a superb reference for all aspects of MoS2 lubrication. (The text is organized in sixteen chapters and contains 561 references). Authoritative volumes such as this one are becoming even more important and useful, and this book is equally valuable to novice and veteran tribologists. The history of MoS2 lubrication is described in chapter 1. Interestingly, it indicates that the material might have been used in a wide range of situations by the Greeks and Romans, but also on the legs of the Appolo Lunar Module as well. Overall, several thousands papers
Book reviews / Tribology International 33 (2000) 143–149
and reports have been published and this may be an indication of the importance of the subject. The next three chapters deal with the extraction of molybdenum disulphide, its physical and chemical properties. Oxidation and the effect of moisture on MoS2 are particularly highlighted: molybdenum oxides are more or less abrasive materials and oxidation takes place preferentially at the crystallite edges whereas non-polar molecules such as hydrocarbons are adsorbed on the lamellar faces. Chapter five is devoted to the mechanism of lubrication related to the special case of MoS2. Deformation friction is usually small in comparison to adhesive friction. Moreover where a thin film is deposited, the shear stress is determined by the surface film. Concerning the origin of low friction by lamellar MoS2, the discussion is well detailed by analysing different parameters such as the effects of contact load, vapours and contaminants. The non-specialist will find a good explanation to distinguish the different behaviours of layer-lattice materials such as mica, graphite and MoS2. The generally accepted view is that low friction of molybdenum disulphide is due to easy shear between lamellae and that the effect of contaminants is to alter the bond energies between the lamellae. Perhaps the lability of sulphur atoms may play a role in a more crystallographic (or atomistic) approach. This aspect is not developed in the text but can be found elsewhere. The next chapter is a more technological approach of formation of MoS2 thin films, burnished film from powder film formation by transfer. The structure of burnished films consists of an assembly of (001) basal planes. This section is very well documented for anyone working in the technological aspect of elaborating efficient films in different conditions, including the effect of the nature of the substrate. Chapter seven focuses on friction properties of MoS2, the effects of moisture and other vapours, the effect of temperature, radiation and vacuum. The effect of particle shape and size, film thickness, sliding speed are also described. This part represents invaluable resources especially for those starting out in these areas. Usefully, the author gives good images of the processes by saying for example that the basal plane surface provides low friction whereas the edges cause abrasion, or that large particles would experience higher rotational couples than small ones etc ... The effect of additives in the film composition, and particularly antimony trioxide is explained by arguing that the oxide acts as a sacrificial anti-oxidant
149
preventing MoS2 from oxideative degradation. Actually this “oxide interaction concept” which is put forward by the author was recently used to explain the antiwear mechanisms of additives such as zinc dithiophosphate for example. Transfer phenomena are universal in dry contact and they indeed play an important role in MoS2 lubrication. It is well known that the lowest friction values of MoS2 are only obtained when the oriented film is present on both surfaces. Before moving to applications of transfer process to the lubrication of mechanical parts, different modes of transfer are discussed in the section, from the re-attachment of loose particles to direct transfer from a surface to the antagonist. In situ MoS2 films from molybdenum organic compounds (or oil-soluble compounds) is reviewed in the light of recently published papers). Unfortunately, molecular rearrangements of Mo and S in the form of MoS2 single sheets have been published too recently to be referenced in the book. The next part is devoted to sputtered films and other physical deposition processes. The effects of sputtering variables on film structure shows that films of high purity are needed. The incorporation of oxygen in the lattice is a significant form of alteration which may increase the reactivity of basal planes. The reference to recent works on the superlubricity of pure MoS2 or adaptive lubricant coatings containing MoS2 and lead oxide indicates that the author always tries to relate past and present data. The last chapters of the book deal with bonded films, composites, metallic composites, ceramic and inorganic composites, greases, pastes and dispersions in oils. There is a considerable amount of data, resources and references in these sections. In the final chapter, the author summarises the practical aspects and gives some selection rules for the choise of MoS2 lubrication modes. To sum up, the book is excellent, maintaining high standards in tribology and making a very significant contribution to the available literature on MoS2 lubrication. Professor Jean Michel Martin Chairman, Department of Materials and Surface Science, Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, BP 163, 69131 Ecully Cedex, France 8 February 2000 PII: S 0 3 0 1 - 6 7 9 X ( 0 0 ) 0 0 0 2 0 - 7
Book reviews / Tribology International 33 (2000) 143–149
Instruments) is lacking only in the absence of any References list. The Chemically Deposited Coatings section is dedicated to two papers on galvannealing processes for steel sheet. In the Chemical Vapour Deposition section, three of the four papers deal with a combustion-based process whose primary purpose is to provide corrosion protection for a variety of metals. Given that there is a section headed Corrosion Resistant Coatings, it is clear that corrosion is an important theme within the book. Having said that, one of the papers in the latter section seems misplaced as it is actually concerned with applications of plasma source ion implantation for metal forming tools within General Motors. The modelling section, likewise, is diverse in content. One paper deals with finite element modelling of contact stresses on coated and uncoated aluminium substrates, whilst the other deals with simulation of growth kinetics in gas nitriding. This latter paper, from authors in Canada and Poland, won the Best Paper Award at the Conference. The sections which will probably be of greatest interest to readers of Tribology International are those dealing with Wear Resistant Coatings and Ultra Hard Coatings. Again, the topics covered in these sections are very wide-ranging. In the former section, papers include subjects such as the improved rolling contact fatigue behaviour of a carburised stainless steel material, the use of ion plated silver and gold to enhance the tribological performance of Si3N4 and SiC materials, the tribological behaviour of silicon-doped diamond-like-carbon (DLC) coatings and the synthesis and properties of crystalline carbon nitride thin films deposited using a ZrN multilayering approach. There is also an interesting paper on self-replenishing solid lubricant films on boron carbide (B4C) from the Argonne National Laboratory in the USA. A couple of papers in this section deal specifically with wear mechanisms. One, from the CNRS laboratory in Mulhouse, France, deals with the kinetics of third body formation (including transfer film build-up). The second, from researchers in Papua New Guinea and Texas A&M University, USA, deals with an investigation of mechanisms in compound wear (i.e. where sliding and impact motions occur simultaneously). Examples of topics in the section on Ultra Hard Coatings include carbon nitride films produced by CO2 laser pyrolysis, sputtered amorphous carbon films, DLC nanocomposite barrier films and metal-doped DLC coatings. A paper from North Carolina State University details the properties of several hard biocompatible coatings and discusses their advantages and limitations (especially with regard to adhesion on prosthetic devices). The laser processing section reflects the variety of uses to which lasers are now put. For example, there is a paper on laser gas alloying of Ti-6Al-4V to form a TiN coating, and another on the control of the surface
structure of graphite fibres for improved composite interfacial properties. These papers tend to emphasise the processes, rather than the tribological properties of the surfaces produced. Similarly many of the papers in the Thermal Barrier Coatings section are concerned with the relationship between process parameters and coating microstructure. The final section, entitled Applications of Coatings, is not the only place in the book where applications-related papers are to be found. It does though contain several papers which will be of particular interest to tribologists. For example, a paper from researchers at the National Science Foundation and Cummins Engine Corporation in the USA discusses the transfer of several novel surface engineering techniques from the laboratory into industrial practice. Another paper, from Thermal Spray Technologies Inc, discusses several interesting case studies of thermal sprayed coating for wear parts such as lawnmower break clutches, sail winches and even bicycle rims. Another paper, from General Motors, discusses the use of thermal spraying for molten metal handling tools and moulds. Overall the book provides valuable material for those involved in developing coatings and those seeking to apply them more effectively. Tribologists will find much of interest within its covers. Professor Allan Matthews The Research Centre in Surface Engineering, The University of Hull, Hull HU6 7RX, UK PII: S 0 3 0 1 - 6 7 9 X ( 0 0 ) 0 0 0 1 9 - 0
Molybdenum Disulphide Lubrication A.R. Lansdown, Tribology series, 35, D. Dowson (Ed.) 1999, pp. 380 This book analyses the various aspects of molybdenum disulphide lubrication in general. It is both a practical guide and a superb reference for all aspects of MoS2 lubrication. (The text is organized in sixteen chapters and contains 561 references). Authoritative volumes such as this one are becoming even more important and useful, and this book is equally valuable to novice and veteran tribologists. The history of MoS2 lubrication is described in chapter 1. Interestingly, it indicates that the material might have been used in a wide range of situations by the Greeks and Romans, but also on the legs of the Appolo Lunar Module as well. Overall, several thousands papers
Book reviews / Tribology International 33 (2000) 143–149
and reports have been published and this may be an indication of the importance of the subject. The next three chapters deal with the extraction of molybdenum disulphide, its physical and chemical properties. Oxidation and the effect of moisture on MoS2 are particularly highlighted: molybdenum oxides are more or less abrasive materials and oxidation takes place preferentially at the crystallite edges whereas non-polar molecules such as hydrocarbons are adsorbed on the lamellar faces. Chapter five is devoted to the mechanism of lubrication related to the special case of MoS2. Deformation friction is usually small in comparison to adhesive friction. Moreover where a thin film is deposited, the shear stress is determined by the surface film. Concerning the origin of low friction by lamellar MoS2, the discussion is well detailed by analysing different parameters such as the effects of contact load, vapours and contaminants. The non-specialist will find a good explanation to distinguish the different behaviours of layer-lattice materials such as mica, graphite and MoS2. The generally accepted view is that low friction of molybdenum disulphide is due to easy shear between lamellae and that the effect of contaminants is to alter the bond energies between the lamellae. Perhaps the lability of sulphur atoms may play a role in a more crystallographic (or atomistic) approach. This aspect is not developed in the text but can be found elsewhere. The next chapter is a more technological approach of formation of MoS2 thin films, burnished film from powder film formation by transfer. The structure of burnished films consists of an assembly of (001) basal planes. This section is very well documented for anyone working in the technological aspect of elaborating efficient films in different conditions, including the effect of the nature of the substrate. Chapter seven focuses on friction properties of MoS2, the effects of moisture and other vapours, the effect of temperature, radiation and vacuum. The effect of particle shape and size, film thickness, sliding speed are also described. This part represents invaluable resources especially for those starting out in these areas. Usefully, the author gives good images of the processes by saying for example that the basal plane surface provides low friction whereas the edges cause abrasion, or that large particles would experience higher rotational couples than small ones etc ... The effect of additives in the film composition, and particularly antimony trioxide is explained by arguing that the oxide acts as a sacrificial anti-oxidant
149
preventing MoS2 from oxideative degradation. Actually this “oxide interaction concept” which is put forward by the author was recently used to explain the antiwear mechanisms of additives such as zinc dithiophosphate for example. Transfer phenomena are universal in dry contact and they indeed play an important role in MoS2 lubrication. It is well known that the lowest friction values of MoS2 are only obtained when the oriented film is present on both surfaces. Before moving to applications of transfer process to the lubrication of mechanical parts, different modes of transfer are discussed in the section, from the re-attachment of loose particles to direct transfer from a surface to the antagonist. In situ MoS2 films from molybdenum organic compounds (or oil-soluble compounds) is reviewed in the light of recently published papers). Unfortunately, molecular rearrangements of Mo and S in the form of MoS2 single sheets have been published too recently to be referenced in the book. The next part is devoted to sputtered films and other physical deposition processes. The effects of sputtering variables on film structure shows that films of high purity are needed. The incorporation of oxygen in the lattice is a significant form of alteration which may increase the reactivity of basal planes. The reference to recent works on the superlubricity of pure MoS2 or adaptive lubricant coatings containing MoS2 and lead oxide indicates that the author always tries to relate past and present data. The last chapters of the book deal with bonded films, composites, metallic composites, ceramic and inorganic composites, greases, pastes and dispersions in oils. There is a considerable amount of data, resources and references in these sections. In the final chapter, the author summarises the practical aspects and gives some selection rules for the choise of MoS2 lubrication modes. To sum up, the book is excellent, maintaining high standards in tribology and making a very significant contribution to the available literature on MoS2 lubrication. Professor Jean Michel Martin Chairman, Department of Materials and Surface Science, Laboratory of Tribology and System Dynamics, Ecole Centrale de Lyon, BP 163, 69131 Ecully Cedex, France 8 February 2000 PII: S 0 3 0 1 - 6 7 9 X ( 0 0 ) 0 0 0 2 0 - 7