Friction reduction mechanisms in boundary lubricated W-doped DLC coatings

The applications of commercially available Diamond Like Carbon (DLC) coatings have seen a rapid increase whilst a lot of tribochemistry problems are not fully understood. This study looks into a tungsten doped hydrogenated DLC coating reciprocating against cast iron in model oils. Friction and wear of such system are then compared with steel. Raman spectroscopy is used extensively to understand the coating interactions with the lubricant/additives. Our results have demonstrated the way to characterize carbon coating structure in lubrication. It clarified that the chemical decomposition of MoDTC to MoS2 is the dominant process rather than the possible formation of WS2 in such system. It also enables application of in situ tribochemical aspects using Raman spectroscopy in ambient conditions.