Microstructure, mechanical and tribological properties of VCN-Ag composite films by reactive magnetron sputtering

A series of VCN-Ag films with different Ag content were deposited by the magnetron sputtering system. The microstructure, mechanical and tribological properties of VCN-Ag films were characterized by X-ray diffractometer (XRD), Raman spectrometer, transmission electron microscopy (TEM), scanning electron microscopy (SEM), nano-indentation and ball-on disc tribo-meter. The results showed that the deposited VCN-Ag films consisted of face-centered cubic (fcc) Ag, fcc-VCN, tetragonal (t) V5CN and amorphous graphite and CNx phases, and nano-crystalline Ag was dispersed in the films. The addition of Ag below 0.72 at.% into the film increased the hardness, however, the hardness decreased rapidly when the Ag content was increased furtherly. The initial introduction of Ag into the film led to the lowering of the film's room-temperature wear rate, nonetheless, the wear resistance deteriorated when the Ag content was further increased. However, the friction coefficient of the films at room temperature increased monotonically as the content of the Ag increased. As for elevated temperature tribological properties of the film at 3.03 at.% Ag, there was an initial increase in frictional values but, when the temperature was above 300 degrees C the frictional values declined. More so, the wear rate increased monotonically when the temperature increased from 100 degrees C to 500 degrees C.