Improvement on the oxidation resistance and tribological properties of molybdenum disulfide film by doping nitrogen

Abstract

Transition metal dichalcogenides such as molybdenum disulfide (MoS2) were classified as excellent solid self-lubricant materials in vacuum or dry conditions. However, their poor mechanical and oxidation resistance properties limited their applications when used in humid air or at elevated temperature. In this paper, nitrogen was incorporated into the molybdenum disulfide matrix to synthesize the Mo–S–N films using RF magnetron sputtering system to improve above mentioned properties. The results showed the deposited nitrogen-free film was MoSx (x < 2), and due to its substoichiometry with respect to sulfur, both amorphous and crystalline state co-existed in MoSx film. Incorporation nitrogen into MoSx matrix induced the poor crystallinity and the formation of Mo–N, S–N and N–N bonds. All Mo–S–N films exhibit higher hardness and oxidation resistance temperature than that of MoSx mainly due to the Mo–N bonds. By comparison with MoSx film, all Mo–S–N films also had excellent tribological properties in the air at room temperature, 200 and 400 °C.