Nano-multilayered ZrN-Ag/Mo-S-N film design for stable anti-frictional performance at a wide range of temperatures

Abstract

A multilayer film, composed by ZrN-Ag (20 nm) and Mo-S-N (10 nm) layers, combining the intrinsic lubricant characteristics of each layer was deposited using DC magnetron sputtering system, to promote lubrication in a wide-range of temperatures. The results showed that the ZrN-Ag/Mo-S-N multilayer film exhibited a sharp interface between the different layers. A face-centered cubic (fcc) dual-phases of ZrN and Ag co-existed in the ZrN-Ag layers, whilst the Mo-S-N layers displayed a mixture of hexagonal close-packed MoS₂ (hcp-MoS₂) nano-particles and an amorphous phase. The multilayer film exhibited excellent room temperature (RT) triblogical behavior, as compared to the individual monolayer film, due to the combination of a relative high hardness with the low friction properties of both layers. The reorientation of MoS₂ parallel to the sliding direction also contributed to the enhanced anti-frictional performance at RT. At 400 °C, the reorientation of MoS₂ as well as the formation of MoO₃ phase were responsible for the lubrication, whilst the hard t-ZrO₂ phase promoted abrasion and, consequently, led to increasing wear rate. At 600 °C, the Ag₂MoO₄ double-metal oxide was the responsible for the low friction and wear-resistance; furthermore, the observed transformation from t-ZrO₂ to m-ZrO₂, could also have contributed to the better tribological performance.