ABSTRACT
Tribology has been de™ned as the science and technology of interacting surfaces in relative motion and related subjects such as friction, wear, and lubrication [1]. Friction is the resistance to relative motion (sliding or rolling) of two surfaces in contact. The coef™cient of friction (µ) is de™ned as the ratio of frictional force (F) to the applied load (W) as shown schematically in Figure 7.1. A practically smooth surface consists of a large number of asperities on the microscopic scale and early researchers believed that the interlocking between the surface irregularities gave rise to friction [2]. According to Amonton’s laws (which were ™rst discovered by Leonardo da Vinci), the friction force is linearly proportional to applied load and also independent of the apparent area of contact [1]. Later, it was proposed by Bowden and Tabor that the friction between metallic surfaces was due to shearing of metallic junctions formed by adhesion or welding at the points of contact and this concept was known as the adhesion theory or welded junction theory of friction [3]. According to the Hertz theory which is based on a nonadhesive single asperity contact, the area of contact is proportional to 2/3 power of load, assuming fully elastic deformation [1,4]. A summary of friction laws can be found in the literature [4,5]. Friction coef™cient is not an intrinsic property of the material; it
7.1 Introduction .......................................................................................................................... 359 7.2 Nanostructured Solid Lubricant Coatings ............................................................................ 365
7.2.1 Nanolayered Multilayer Coatings .............................................................................366 7.2.2 Nanocomposite Coatings .......................................................................................... 367 7.2.3 Adaptive Coatings ..................................................................................................... 372 7.2.4 Fullerene-Like Transition Metal Dichalcogenide Nanoparticle-Based Coatings..... 376 7.2.5 Polymer-Based Nanocomposites .............................................................................. 376
7.3 Growth of Nanostructured Solid Lubricant Coatings .......................................................... 383 7.3.1 Wet Chemical Methods ............................................................................................ 383 7.3.2 Physical And Chemical Vapor Deposition Techniques ............................................384
