The effects of deposition temperature and post-annealing on the crystal structure and mechanical property of TiCrAlN films with high Al contents

Ti_xCr_yAl_zN (x+y+z=1) films were synthesized by the arc ion plating method (AIP) under various deposition temperatures between 400 and 650 °C. The films, synthesized from Ti_0.1Cr_0.2Al_0.7 and Ti_0.25 Cr_0.1Al_0.65 targets, were identified as a cubic type structure below 580 and 650 °C, respectively, over which the films were a mixture phase of cubic and hexagonal type. The microhardness of these films decreased from 30 GPa to 24 GPa corresponding with the phase transition from the cubic to the mixture phase. The grains size of c-Ti_0.1Cr_0.2Al_0.7N and c-Ti_0.25Cr_0.1Al_0.65N films were approximately 100 nm and changed to 20-30 nm after the phase transitions. The effect of post-annealing on the phase transition was investigated for the films with the cubic structure. The result showed that the cubic-type films partially transformed to hexagonal structure by annealing over 900 °C, which led to increase in lattice parameter. In this paper, mechanical properties, microstructure and thermal stability of Ti_xCr_yAl_zN films as a function of Cr contents were investigated and discussed on phase transitions.