Low friction mechanism of chlorine-doped amorphous carbon films sliding against an aluminium alloy

The effect of chlorine-doping on the tribological properties of amorphous carbon films was investigated. Chlorine-doped amorphous carbon films were deposited using a plasma-based ion implantation and deposition (PBII&D) method with vaporized tetrachloroethylene as a precursor. During sliding tests with aluminium alloy counter parts, chlorine-doped amorphous carbon films showed lower friction coefficients compared to hydrogenated amorphous carbon films. Both aluminium and a chlorine-based hydrate were observed on the wear track of the carbon films. This hydrate was a tribofilm formed via a tribochemical reaction during sliding between the chlorine-doped amorphous carbon films and aluminium alloy. The viscosity of this tribofilm was similar to polyalpha olefin and we propose that it acted as a lubricant and lowered the friction coefficient.