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

We fabricated WS2/MoS2/C nanometer-scale triple-multilayer films (superlattice structured multilayer films) with dry lubricating characteristics using multitarget RF sputtering. 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. Superlattice structured film is expected to exhibit good mechanical properties, such as high hardness and high stiffness, resulting in low friction and long endurance life in comparison to those of the individual single-layer materials. In the previous study, we concluded that WS2/MoS2 dual-multilayer film showed significantly improved tribological performance in comparison to the single-layer MoS2 or WS2 films. To modify the tribological properties of the nanometer-scale multilayer further, we have prepared the triple-multilayer and sliding friction experiments have been conducted with the films formed on silicon substrates in contact with 440C stainless-steel balls under sliding conditions of ambient air and vacuum at room temperature. The results obtained showed that the triple-multi layer film exhibits superior friction endurance compared with MoS2, WS2 or the dual-multilayer films under atmospheric sliding conditions. in vacuum, wherein almost no effects of humidity or oxygen are observed, both sulfide single-layer films and both multilayer films exhibit lower friction coefficients in comparison to those in ambient air.