THE EFFECT OF SLIDING SPEED ON WEAR OF DIAMOND-LIKE CARBON COATINGS

The effect of sliding speed, wear track diameter and sliding distance on the wear behaviour of a diamond-like carbon (DLC) coating deposited using magnetron sputtering from a carbon target at very high ion curr ent density has been investigated applying experimental design and sta tistical variance analysis. It has been shown that sliding speed has a highly significant effect on wear rate of the DLC coating. Within the sliding speed range studied (0.048 to 0.45 m s(-1)), a U-shaped parab olic curve for the relationship between specific wear rate and sliding speed has been observed with a minimum wear rate at a speed of approx imately 0.25 m s(-1). There is a significant negative effect from the combination of sliding speed and distance on wear rate which indicates the involvement of some time-related processes in wear mechanisms for the DLC coating. A model is presented based on the assumption that th e control step in the generation of wear debris particles is the chemi cally activated debonding at the crack tip due to the presence of some reactive species. A semi-quantitative expression for the relationship between the specific wear rate and sliding speed has been derived. Re asonably good agreement between this expression and experimental resul ts was obtained. (C) 1998 Elsevier Science S.A. All rights reserved.