Phase transitions of doped carbon in CrCN coatings with modified mechanical and tribological properties via filtered cathodic vacuum arc deposition

Abstract The CrCN coatings were fabricated onto Si (1 1 1) wafers and SUS304 stainless steel plates using filtered cathodic vacuum arc deposition (FCVAD) technique under different flow ratios of N 2 /C 2 H 2 gas mixture. The morphology, crystalline structure and chemical composition of the coatings were characterized. It was found that the grain size reduce with increasing carbon content, which makes the CrCN coatings refined and smooth. The quasi-one-dimensional carbolite phase was also found in CrN host lattice with C 2 H 2 content ranging from 5% to 20%, and it will be evolved into amorphous carbon and amorphous CN x phases as C 2 H 2 content exceeds 20%. Moreover, we examined the mechanical and tribological properties of the CrCN coatings, and the experimental results confirmed that the friction coefficient of the coatings descend to the lowest value as 0.39 with 30% C 2 H 2 content, due to the graphite (sp 2 C C) phase embed in CrN host lattice; while the chromium carbon (Cr 3 C 2 ) and diamond (sp 3 C C) phases may give rise to the increase of the coating hardness with the highest value at 23.97 GPa under 20% C 2 H 2 content.