Effect of C₂H₂/N₂ partial pressure ratio on microstructure and mechanical properties of Ti-Al-Si-C-N coatings

Ti-Al-Si-C-N nanocomposite coatings were deposited on cemented carbide (WC-10 wt%, Co) substrates by reactive magnetron sputtering technique. The effect of C₂H₂/N₂ partial pressure ratio on element concentration, deposition rate, microstructure, cross-sectional morphology, hardness and tribological properties of the coatings were studied. The coatings were found to have a nanocomposite structure consisting of nanocrystallities (Ti,Al)(C,N) and amorphous phase. The coating's columnar crystals structure was restrained with the increase of C₂H₂/N₂ partial pressure ratio. The deposition rates and nanohardness of coatings firstly increased with the increase of C₂H₂/N₂ partial pressure ratio and reached their maximum values of 133 nm/min and 35 Gpa, respectively, at C₂H₂/N₂ partial pressure ratio of 1:2 before decreasing. The friction coefficient and wear rates of Ti-Al-Si-C-N coatings dramatically decreased with the increase of C₂H₂/N₂ partial pressure ratio and reached the lowest value of 0.17 and 1.1 × 10–6 mm³/Nm, respectively, at C₂H₂/N₂ partial pressure ratio of 1:1.