Effect of temperature of annealing below 900 °C on structure, properties and tool life of an AlTiN coating under various cutting conditions

In this study the cemented carbide cutting tools with a nano-crystalline Al0.67Ti0.33N hard PVD coating deposited by cathodic arc evaporation were annealed within a range of temperatures 700–800 °C during 2 h in vacuum. The changes in structure and properties of the coating vs. temperature have been analyzed using TEM as well as high temperature nano-indentation methods. Cutting tools with the annealed AlTiN coating have been run through a number of cutting tests with varying conditions. The conditions were as following: 1) continuous cutting: turning of annealed 1040 steel (HB 220); 2) interrupted cutting: turning of 4340 steel (HRC 40); 3) end milling: ball nose end milling of hardened H13 steel (HRC 50). The cutting tool life has been investigated before and after annealing of the Al0.67Ti0.33N coatings at different temperatures. The relations between high temperature hardness and plasticity of the Al0.67Ti0.33N coating and tool life under varying cutting conditions was outlined.