Low-friction behaviour of diamond-like carbon films in a water environment

Abstract Lubrication films of DLC coating were investigated using transmission electron microscope (TEM) analyses. The friction behaviour of DLC and Si-doped DLC films against AISI 440C stainless steel ball was evaluated under water using a ball-on-disk type reciprocating friction tester. The lubrication film at wear scar of mating ball was determined by cross-section TEM and EDS. Thin lubrication films (5–20 nm) on a flat area of wear scars were observed. Furthermore, it was confirmed that the lubrication film for Si-DLC had a double-layer structure and that of DLC had a monolayer structure. The localization of Cr was identified in lubrication films. It is concluded that the structure of the lubrication film played an important role in the low friction behaviour in a water environment.