Critical role of a metallic counterpart on the tribochemical wear of ta-C coatings in base oil

Diamond-like carbon coatings (DLC) are promising materials for tribological applications thanks to their ability to reduce friction and wear of mechanical parts. However, their wear mechanism under boundary lubrication and the way they interact with the lubricant and the counterpart are still not fully understood. The first results of this study showed that the high hardness of a DLC coating does not prevent from wear. High hardness tetrahedral amorphous carbon coatings (ta-C) showed a higher wear than softer hydrogenated amorphous carbon coatings (a-C:H) when sliding against M2 or AISI52100 steel in base oil, preheated to 110 °C. Experiments also revealed that the tribochemical wear of ta-C is activated by temperature. To deepen the study, different metal coatings were deposited on the steel counterpart. The analyses of the worn surfaces showed that the counterpart nature plays a significant role on the wear of ta-C and suggested that elements having a carbophilic character could promote the formation of a heterogeneous carbon-containing tribofilm on the steel surface.