Correlation between arc evaporation of Ti-Al-N coatings and corresponding Ti0.50Al0.50 target types

Ti-Al-N, which has been proven to be an effective protective coating for machining application, is one of the most studied ternary transition metal nitrides systems. Here, the Ti-Al-N coatings were deposited from three different target types (TiAlN_1: powder metallurgical (PM) Ti0.50Al0.50 target produced from powders with grain sizes between 45 and 150 μm, TiAlN_2: PM target produced from powders with grains sized below 45 μm and TiAlN_3 for smelting (SM) target) by cathodic arc evaporation in order to investigate the effect of target types on the structure, mechanical and thermal properties of arc evaporated Ti-Al-N coatings. For Ti-Al-N coatings deposited from PM targets, the TiAlN_2 coating has higher deposition rate, concentration of metallic macro-particles and hardness than TiAlN_1 coating. Additionally, decreasing Ti and Al grain sizes of PM targets has a deteriorative effect on the thermal stability and oxidation resistance of Ti-Al-N coatings, where TiAlN_2 coating exhibits an earlier w-AlN formation by ~ 100 °C during thermal annealing in Ar and thicker oxide scale during exposure to air at 850 °C. The utilization of SM target causes an obvious drop in hardness and oxidation resistance for TiAlN_3 coating, which exhibit similar concentration of metallic macro-particles and thermal decomposition process with TiAlN_1. Therefore, the best cutting performance is obtained by TiAlN_1 coated inserts allowing for the overall mechanical and thermal properties of coating.