Microstructure, mechanical, and tribological properties of niobium vanadium carbon nitride films

Abstract

Composite Nb-V-C-N films with different carbon content were synthesized using reactive magnetron sputtering system, and the influence of carbon on the microstructure, mechanical, and tribological properties of niobium vanadium nitride films was investigated. The films with carbon content below 9.1 at. % exhibited a two-phase of solid solution face-centered cubic (fcc) (NbV)(CN) and hexagonal close-packed (hcp) (NbV)2(CN); increasing the carbon content further induced the formation of amorphous carbon and CNx, and the films consist of fcc-(NbV)(CN), hcp-(NbV)2(CN), amorphous carbon, and CNx. Solid solution strengthening and the heterostructure led to an increase in hardness to ∼32 GPa at 9.1 at. % carbon. A further increase in carbon content led to a gradual decrease in hardness due to the formation of soft amorphous phases of carbon and CNx. The tribological properties of the films against alumina counterpart at room temperature were significantly influenced by the carbon content. The incorporation of carbon into the films decreased the average friction coefficient (μ) from ∼0.61 at 0 at. % carbon to ∼0.25 at 21.6 at. % carbon. As the carbon content increased, the wear rate first dropped from ∼2.6 × 10−8 mm3/(N mm) at 0 at. % carbon to ∼1.2 × 10−8 mm3/(N mm) at 9.1 at. % carbon, and then rose gradually to ∼8.7 × 10−7 mm3/(N mm) at 21.6 at. % carbon.