Deposition and tribological properties of WS2/MoS2/C solid lubricating multilayer films

We used multitarget RF sputtering to fabricate WS 2 /MoS 2 /C nanometer-scale triple-multilayer films (superlattice-structured multilayer films) with dry lubricating characteristics. Superlattice structures are obtained by layering two or more materials in a regular periodic structure at a thickness of several atoms or several tens of atoms. Film with a superlattice structure is expected to exhibit good mechanical properties, such as high hardness and stiffness, that result in lower friction and longer endurance life than individual single-layer materials. In our previous study, we concluded that WS 2 /Mos 2 dual-multilayer film showed significantly better tribological performance than single-layer MOS 2 or WS 2 films. We prepared the triple-multilayer film to further improve the tribological properties of the nanometer-scale multilayer. We conducted sliding friction experiments with films formed on silicon substrates in contact with 440C stainless-steel balls under sliding conditions of ambient air and vacuum at room temperature. The triple-multilayer film exhibited better friction endurance than the MOS 2 , WS 2 , and dual-multilayer films under atmospheric sliding conditions. The sulfide single-layer films and multilayer films exhibited lower friction coefficients in a vacuum, where humidity and oxygen had almost no effect, than in ambient air.