Tribological laboratory evaluation of thin hard coatings

Thin hard coatings are currently being used in a large number of important tribological applications, such as metal cutting tools, forming tools, sliding bearings, seals, engine parts and other machine elements. Therefore the need to understand what decides the tribological response of a coating composite in a given tribological system, and to be able to experimentally rank different composites, is becoming more and more pressing. One of the greatest challenges is to design and/or employ tribological laboratory tests that are suited for this kind of study, that is, tests that are able to correctly simulate different well-defined tribological systems. The present paper deals, experimentally, with the problems of determining tribological coating properties. In particular, the use of several tests, designed and developed at Uppsala University exclusively for the purpose of tribological characterisation of thin hard coatings and coating composites, are presented and discussed. Some examples are given in the form of results from abrasion, solid particle erosion and sliding wear studies of several thin hard coatings, e.g. TiN, CrN, NbN, and some multilayered combinations thereof. (C) 1997 Elsevier Science S.A.