Self-adaptive MoS2-Pb-Ti film for vacuum and humid air

Space equipment is stored in terrestrial environments before launch, where the water vapor is detrimental to the tribological performance of molybdenum disulfide (MoS2). To meet the requirement of the storage on the earth and the use in space, a new kind of MoS2-Pb-Ti film was designed. Both vacuum and air tests demonstrated that its tribological performance was much better than that of MoS2 film. To explore the origin of the excellent tribological performance, MoS2, MoS2-Ti and MoS2-Pb films were also studied as references. The composition, mechanical properties, surface morphologies and microstructures of as-deposited films were investigated with energy dispersive spectrometer (EDS), nanoindenter, scanning electron microscopy (SEM), atomic force microscopy (AFM), glancing angle X-ray diffraction (GIXRD) and Raman spectrometer. The tribological tests were performed in vacuum and air under different relative humidity. The superior tribological properties of MoS2-Pb-Ti film in vacuum were mainly attributed to MoS2 dominated contact interfaces, the increased elastic modulus and an improved transfer layer. Moreover, the significantly improved tribological performance in humid air was mainly due to the sacrificial effect of doped metals, which protected the MoS2 from the attack of H2O and O2. Furthermore, the potential application of MoS2-Pb-Ti film for alternative humid air and vacuum was explored.