THIN TRIBOLOGICAL COATINGS - MAGIC OR DESIGN

Surface engineering using applied coatings has become a well-establish ed technology and is an extremely versatile means of improving compone nt performance. Tribological coatings add physical properties, such as lubricity, hardness, or corrosion resistance, to lower-valued substra tes that improve the overall quality of the component. In addition, th e substrate can be designed for strength and toughness to avoid catast rophic failure of the component. This message is often misinterpreted by end-users of coated components, however, in the sense that it is be lieved that a thin surface coating can provide superior performance to a component made out of a cheap low quality bulk material. In additio n, suppliers of tribological coatings often offer coatings on a trial and error basis without a systematic approach, resulting in few succes ses with many disappointments. In this paper some typical aspects of t ribological coatings will be highlighted. emphasising that a coated co mponent must be regarded as a composite structure. Both the coating an d the substrate should be optimised taking into account mechanical, st ructural, chemical, electrical, thermal, and dimensional properties. T echniques are presented for the reliable testing of thin surface coati ngs, and a generic methodology is suggested using surface coating tech nology for systematic problem solving of friction and wear cases. Fina lly, an example of the potential of thin surface films for tribologica l applications is given. (C) 1997 Elsevier Science S.A.