Effect of Environment Humidity on Friction Behavior of MoS₂-Au/SiCH Composite Lubricating System

The friction behavior of MoS₂-Au film /SiCH (silahydrocarbon) oil composite system was investigated in various humidities using a ball-on-disk tribometer. Compared with the single MoS₂-Au solid film or SiCH oil lubrication condition, a synergy lubrication effect was displayed when they were combined to a composite system. The steady-state friction coefficient reduced largely as the environment was changed from low to high humidity, while wear rate varied in a inverse trend. The results of Raman and FTIR revealed that no tribo-chemical reactions occurred for SiCH oils during the friction. A structure model of dual liquid lubrication, combining SiCH with the adsorbed water on the base plane of MoS₂, was proposed to explicate the friction behavior in high humidity, where the declined friction coefficient was attributed to the low shear strength at the interface of water and SiCH layers.