A comparative study of state-of-the-art diamond-like carbon films

Diamond-like carbon (DLC) coatings represent a group of very similar but st ill very different materials. Their characteristics range from graphite-lik e to diamond-like to polymer-like, depending on the deposition techniques. The sensitivity of DLC coating properties to processing conditions can be c onsidered a problem, but on the other hand it creates opportunities for ada ptation to specific applications. In this study the mechanical and tribolog ical properties of various state-of-the art DLC coatings (from six supplier s) were investigated to generate a basis of data for comparison that should facilitate the selection of DLC coatings for particular applications. Hard ness and modulus of elasticity were measured by depth-sensing indentation. Scratch testing was used to determine the adhesive strength of the coatings . The friction and wear tests were conducted using a ball-on-fat and flat-o n-flat configuration under unidirectional and reciprocating motion, respect ively. The results of this work demonstrate that the mechanical and tribolo gical properties of DLC coatings vary strongly. Each coating type has speci fic advantages and the complete range of properties should be studied caref ully to select the appropriate coating in a particular application. A more general guideline for DLC selection is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.