Enhancement of the mechanical and tribological properties of self-lubricant Mo2N–Ag composite film by adding amorphous SiNx

Abstract

In this paper, the Si was introduced into the Mo2N–Ag matrix to synthesize the Mo2N–Ag-SiNx composite films using the magnetron co-puttering technology, designed to provide low-friction and long-term green tribological solutions for the demanding applications used at elevated temperatures. The results showed that the fcc-Mo2N, fcc-Ag, and amorphous SiNx were the main phases in the composite films. Adding Si of above 1.3 at.% could increase the hardness as well as the elastic modulus to ∼21 and ∼245 GPa. The average friction coefficient (COF) at room temperature (RT) exhibited a slight effect from the Si content, and its value was kept at 0.54–0.60, regardless of Si content. However the RT wear rate was significantly enhanced by adding Si of 1.3 at.%, due to the enhancement on the mechanical properties. At 600 °C, the COF decreased from 0.24 at 0 at.% Si to 0.19 at 5.0 at.%, but further increasing the Si content led to an increase in COF. The wear resistance was significantly enhanced by adding Si. It was mainly influenced by the lubricant transfer layers.