Structural design of MoS2-based coatings toward high humidity and wide temperature

The lubrication of pure MoS2 coating for the application in air environment has been commonly limited owing to its loose structure, low hardness, and high humidity sensitivity. To overcome such drawbacks, MoS2/Pb–Ti composite and multilayer coatings were deposited by unbalanced magnetron sputtering system. And subsequently, the oxidation resistance and tribological properties of such MoS2-based coatings were studied after 30 days of exposure under different temperatures (ranging from 20 to 80 °C) with the relative humidity of 80% (RH 80%). We found that pure MoS2 showed poor oxidation resistance after 30 days of exposure and presented high and fluctuating coefficient of friction (COF), leading to the early failure of the coating. In contrast, the oxidation resistance of MoS2 was improved significantly by Pb–Ti co-doping and multilayer design. What is more, the low COF and wear rate were also obtained from the composite and multilayer coatings even after 30 days of exposure at 80 °C, RH 80%, which was related to the compact structure and higher values of hardness to elastic modulus (H/E). More importantly, the high density of interfaces and a relatively strong (002) preferred orientation in the multilayer coating were beneficial to reduce the wear and COF, causing better tribological performance than others.