Similar to steel, diamond-like carbon (DLC) coatings represent a group of materials exhibiting a broad range of properties. DLC material characteristics range from graphite-like over diamond-like to polymer-like behaviour. Strongly varying physical, mechanical, and tribological properties [4±6] are found, which is not surprising since DLC coatings are prepared by a wide variety of techniques. The use of multilayer structures, different alloying elements such as Si, Ti, Cr, and W, and different adhesion promoting interlayers results in an even wider range of coating properties.
The sensitivity of DLC coating properties to process conditions can be considered as a problem, on the other hand it creates the opportunity to adapt the coating properties to specific applications.
At present, DLC coatings start to find broader application but many industries, often producing low-cost products, still make no use of this promising material because of, amongst others, the lack of a systematic guide describing the different types of DLC coatings and their pros and cons with respect to specific tribological conditions.
The results described in this paper are part of the work performed in the COST 516-Tribology project ªApplication oriented evaluation of wear resistant low friction coatings based on diamond-like carbon and related materialsº. In this project twelve partners co-operated to collect data about the mechanical and tribological properties of a representative series of current state-of-the-art DLC coatings. The coaters, commercial job-coaters as well as research laboratories submitted their coatings for testing. The research partners then carried out the characterisation of these coatings and complementary wear tests.