Effect of lubricant on contact surfaces

In the study and design of machine components it isoften desirable to have detailed knowledge,of the complianceand contact stresses in the mating surfaces. This gives anindication to the designer about the failure and wear of co-ntacting surfaces. To minimize the wear it might use a regi-me of fluid lubrication, such as boundary, hydrodynamic andelatohydrodynamic ones. Some of machine components can notbe lubricated by any of fluid lubricants. Oftenly these ele-ments are subjected to elevated temperature, surrounded bychemical reactive environment, or difficult to be lubricatedby conventional liquids 11,2].The solid lubricants are widely used in the aerospaceindustry, automotive, heavy electrical generators, metal wo-rking ... etc. The solid lubricants are used successfully un-der conditions which are normally either inconvenient or ad-verse to other lubrication forms. The main advantage of thesolid lubricant used is the good stability at extreme tem-perature and chemically reactive environments. In addition,they are of lighter weight, require fewer seals, and do notneed any circulating system. Solids oftenly used to providepermanent lubrication for parts of equipment which are inac-cessible after assembly. Moreover, solid lubricants are qui-te stable in very radioactive environments.The use of solid lubricants reduces time spent in perio-dic maintenance. To investigate how the surface coatings