Effect of Ag content on friction and wear properties of TiCN/Ag films in different service environments

Thin-film materials require improved performance to withstand complex and harsh environments as the modern industry evolves. In this study, a series of TiCN/Ag films were fabricated to enhance the frictional properties of the films and extend the lifetime of friction sliding components. The microstructure, mechanical properties, friction, and wear properties of the films were investigated in different service environments. The results showed that the film comprised fcc-TiN, fcc-Ag, amorphous carbon, and amorphous carbon nitride. As the Ag content increased, the hardness of the film first increased, then decreased rapidly, after which the decreasing trend became stable. When the Ag content was 1.8 at%, the optimal hardness and elastic modulus of the films were 29.7 GPa and 228.09 GPa, respectively. Under oil lubrication conditions, Ag atoms can catalyze the formation of a highly graphitized carbon-based friction film on the TiCN/Ag worn surface, thereby enhancing the friction and wear properties of the films. In the air friction, the soft-phase Ag with a low shear modulus acts as a lubricant, and the friction coefficient decreases with an increase in Ag content; however, the consumption of Ag during friction increases the wear rate. In the 3.5 wt% NaCl solution, as the Ag content increased, the surface roughness and corrosion current of the film increased, while the corrosion potential and resistance of the film decreased, resulting in an increase in the friction coefficient and wear rate.