Oxidation resistance of CrAIN films with different microstructures prepared by pulsed DC balanced magnetron sputtering system

CrAIN films were prepared using a pulsed DC balanced reactive sputtering system under different N₂/Ar ratios and pulse widths. We investigated the oxidation resistance of two CrAIN films with different microstructures; i) with a fcc-CrN structure, lower internal stress and moderate hardness, and ii) with a mixed structure of hep-AIN and hcp-Cr₂N phases, higher internal stress and super high hardness of 41 GPa. The CrAIN film (i) having the single fcc-CrN structure showed good oxidation resistance up to 900°C. The plastic hardness of this film increased to a maximum of 38.5 GPa at 900°C. In contrast, the CrAIN film (ii) with the mixed structure of hcp-AIN and hcp-Cr2N phases was stable up to 800°C. The plastic hardness of this film decreased gradually with annealing.