The oxidation and erosion of atomic oxygen are considered to be the most dangerous environmental factors for materials exposed to the aerospace environment. In order to investigate the effect of atomic oxygen on the lubricating film and improve the tribological properties, MoS₂–WS₂ composite film was prepared by the sputtering technique. The film structure and mechanical behavior were characterized and their vacuum tribological properties were evaluated by a friction tester. The composite film possessed better atomic oxygen (AO) resistance than pure film because of the dense structure. The tribological performance of composite film was different under the conditions after AO-irradiation and sliding and during AO-irradiation. After AO-irradiation, the tribological properties of composite film were similar to those before AO-irradiation. However, high friction noise, wear rate, and reduced wear duration were observed for the composite film under the AO-irradiation/friction process because of the continuous damage of the lubricating film due to the AO-irradiation. The addition of 16 at.% WS₂ to the MoS₂-based film changed the composite film structure and improved the oxidation resistance of the film, making the composite film exhibit better tribological performance than pure MoS₂.

MoSN/MoS₂ multilayer films were deposited by a sputtering MoS₂ target in alternate Ar and Ar/N₂ mixed atmospheres with different nitrogen flow rates. The influence of nitrogen flow rates on the microstructure, mechanical and tribological properties of the prepared films were investigated. The multilayer film exhibited the preferred orientation of (002) plane for MoS₂ sublayers and amorphous structure for MoSN sublayers. Introducing N₂ into the source gas resulted in a much more compact structure for multilayer films due to the suppression of columnar growth of MoS₂ film. With the increase of the nitrogen flow rate, the hardness of the multilayer film firstly increased from 2.3 to 10.5 GPa as the nitrogen flow rate increased from 4 to 10 sccm and then turned downwards to 6.5 GPa at 20 sccm. MoSN/MoS₂ film deposited with an optimized microstructure exhibited low friction coefficients below 0.03 and a wear life higher than 1.8×10⁵ revolutions in vacuum. Meanwhile, the optimized film showed an ultralow friction coefficient of 0.004~0.01 and wear rate of 4.7 × 10⁻⁷ mm³/N·m in an ultrahigh vacuum. Both the enhanced hardness by N-doping and sustainable formed MoS₂ tribofilm contributed to the improved tribological property of MoSN/MoS₂ multilayer film.

Pure WS₂ films were prepared by the radio frequency sputtering of a WS₂ target with the initial substrate temperature controlled to −40, −25, 0 °C and room temperature by cooling the holder with liquid nitrogen, respectively. The influence of the substrate temperature on the microstructures and the tribological properties of the prepared films have been evaluated and the wear mechanism of the films was explained. It revealed that with decreasing the substrate temperature, the prepared WS₂ film changed from the loose and coarse columnar plate structure for film deposited at room temperature to a much more compact morphology for film deposited at −40 °C. The WS₂ film deposited at low temperature of −40 or −25 °C exhibited a long wear life higher than 5.0 × 10⁵ sliding cycles, while this was about 1.5 × 10⁵ cycles for the WS₂ deposited at room temperature. The improved tribological properties for the low temperature-deposited film were mainly attributed to the much lower wear rate resulted from the compact structure as well as the sustained and steadily formed transform layer on the counterpart ball.