Properties of (Ti,Cr,Al)N coatings with high Al content deposited by new plasma enhanced arc-cathode

Abstract

A novel super hard coating system of (Ti x Cr y ,Al z )N ( x: y∼1:2, z=0.63–0.73, x+ y+ z=1) was synthesized by a newly developed plasma enhanced type of arc-cathode. The effect of arc-cathode type, film composition and process parameters on coating's properties was investigated. It was found that in the deposition of the new (Ti,Cr,Al)N coatings, the plasma enhanced cathode has an effect to reduce the number of macro-particles significantly. Depositions of (Ti,Cr,Al)N with approximately z=0.7 under different substrate biases revealed that there was a bias induced phase change from hexagonal (B4) to cubic (B1) structure approximately 50 V of the substrate bias. The hardness of the coating changed drastically as the crystal structure changed from hexagonal to cubic phase, reached more than 35 GPa under proper bias conditions. Depositions from the targets, which contain different Al ratio revealed that cubic phase was maintained up to Al ratio of 0.73. The onset temperature of the oxidation of the (Ti,Cr,Al)N, which was measured by thermo-balance, was approximately 1000 °C, whereas 850 °C was realized in case of the conventional (Ti,Al)N. Also high speed cutting tests against hardened die-steel were conducted in comparison with conventional (Ti,Al)N.