Friction and wear performance of diamond-like carbon films grown in various source gas plasmas

In this study, we investigated the effects of various source gases (methane , ethane, ethylene, and acetylene) on the friction and wear performance of diamond-like carbon (DLC) films prepared in a plasma-enhanced chemical vapo r deposition (PECVD) system. Films were deposited on AISI H13 steel substra tes and tested in a pin-on-disk machine against DLC-coated M50 balls in dry nitrogen. We found a close correlation between friction coefficient and so urce gas composition. Specifically, films grown in source gases with higher hydrogen-to-carbon ratios exhibited lower friction coefficients and a high er wear resistance than films grown in source gases with lower hydrogen-to- carbon (H/C) ratios. The lowest friction coefficient (0.014) was achieved w ith a film derived from methane with an H/C ratio of 4, whereas the coeffic ient of films derived from acetylene (HC = 1) was 0.15. Similar correlation s were observed for wear rates. Specifically, films derived from gases with lower H/C values were worn out, and the substrate material was exposed, wh ereas films from methane and ethane remained intact and wore at rates that were almost two orders of magnitude lower than films obtained from acetylen e. (C) 1999 Published by Elsevier Science S.A. All rights reserved.