The microstructure and tribological properties of molybdenum and silicon nitride composite films

Molybdenum nitride (MoxN) film exhibited an excellent self-lubricating performance at room and elevated temperature, while its wear resistance was not very satisfactory. In this paper, silicon was added into the MoxN matrix to enhance the wear resistance and a series of Mo-Si-N films was deposited using magnetron sputtering system. Results showed that the incorporation of silicon into the MoxN matrix in the argon and nitrogen atmosphere led to the formation of another phase of amorphous (a) Si3N4 and the films exhibited a dual-phase of face-centered cubic (fcc) solid solution of (MoSi)(x)N and a-Si3N4. Adding silicon < 3.7 at.% dropped the wear rate (WR) at room temperature with the raising of friction coefficient (Cof.) due to the roughness reduction and hardness enhancement. Higher oxidation resistance temperature of the film at 3.7 at.% silicon resulted in a reduction of the MoO3 tribo-phase and it improved the elevated temperature wear resistance, compared with the MoxN film.