THE MECHANICS OF THE TRIBOLOGY OF THIN-FILM SYSTEMS

This paper aims to explain both the advantages and the current limitations of thin film systems in tribological situations. It begins with short reviews of the relevant basic concepts of friction and wear, of those elements of contact mechanics which are a necessary introduction to an understanding of tribological behaviour, and of the stresses occurring at uncoated surfaces, initially under normal load only and then under combined normal and tangential loads. It then describes the mechanics underlying the two technologically important systems of hard surfaces covered by soft coatings and relatively soft surfaces covered by hard coatings. The mechanics of the scratch test are then discussed and explanations are offered for the various failure modes observed during such a test. Finally, outlines are given of current and future programmes of work designed to elucidate the factors limiting coating performance.