Effect of alloying element (Si,Y) on properties of AIP deposited (Ti,Cr,Al)N coating

Experiment on systematic alloying of Si and Y to (Ti,Cr,Al)N coating was conducted with a fixed Si + Y ratio (0.05) and effect of Si + Y addition to the structural and mechanical characteristics of (Ti,Cr,Al)N coating was investigated. (Ti0.2Cr0.2Al0.55Si0.03Y0.02)N and (Ti0.15Cr0.2Al0.6Si0.03Y0.02)N coatings were deposited by cathodic arc ion plating (AIP) under different substrate bias voltages. Crystal structure was a mixture of cubic (rock-salt) and hexagonal, (wurzite) when the substrate bias is lower than 50 V, transforming into a cubic single phase was observed when bias is increased. Maximum hardness of 33 GPa is obtained under the same conditions which the cubic single phase is obtained. Oxidation resistance was primarily evaluated by measuring oxidation weight gain curves in dry air. For (Ti,Al,Cr,Si)N, sudden weight decrease due to decomposition of CrN to Cr2N was observed, whereas up to 1200 °C, no major weight change was observed in case of Si + Y added (Ti,Cr,Al)N. Composition of the oxide layer was analyzed using AES depth analysis after annealing in air at 1000 °C. The oxide layer thickness was approximately reduced to half compared to (Ti,Al,Cr,Si)N, showing the superior oxidation resistance of this coating system. Cutting tests were conducted against hardened high speed steel (HRC 65) and clearly showed reduced wear of cutting edge compared to (Ti,Cr,Al,Si)N.