Tribological behavior of MoS2/a-C:Si composite films in high-temperature air and vacuum environments

Abstract

MoS2/a-C:Si composite films doped with different contents of carbon (C) and silicon (Si) were deposited using a hybrid deposition system consisting of a superimposed high-power impulse magnetron sputtering (HiPIMS)-direct current magnetron sputtering (DCMS) and a mid-frequency magnetron sputtering (MFMS). The content of C and Si elements in the films was controlled by changing the direct current (DC) of the graphite-silicon (C-Si) mosaic target. The effects of C and Si doping on the microstructure and mechanical properties of the films were investigated. In addition, the tribological behavior of the films in high-temperature air (up to 350 °C) and vacuum environments was evaluated in detail. The results suggested that MoS2/a-C:Si composite films exhibited excellent tribological properties in both high-temperature air and vacuum environments. MoS2/a-C:Si composite films doped with C and Si elements exhibited low coefficient of friction (COF) and wear rate (WR) at elevated temperatures due to the improved thermal stability. In particular, MoS2/a-C:Si composite film with 40.37 at% C displayed a low COF of 0.051 and a low WR of 1.47 × 10 −6 mm3/(N·m) at 350 °C in air. Moreover, MoS2/a-C:Si composite film also exhibited excellent tribological properties under vacuum conditions due to the precipitation of C on the wear track surface. The COF of MoS2/a-C:Si composite film with 40.37 at% C under vacuum conditions was as low as 0.018, and the WR of the film was as low as 1.99 × 10 −7 mm3/(N·m).