Microstructure, mechanical and tribological properties of Cr 1− xAl xN films deposited by pulsed-closed field unbalanced magnetron sputtering (P-CFUBMS)

Abstract

Nanocrystallized Cr 1− x Al x N films with various Al contents (0 to 68 at.%) were deposited by pulsed closed field unbalanced magnetron sputtering (P-CFUBMS). The effects of aluminum content on the microstructure, mechanical and tribological properties of the Cr 1− x Al x N films have been investigated. It was found that the hardness and elastic modulus of Cr 1− x Al x N films increased with increasing Al contents in the films and reached the highest value of 36 GPa and 370 GPa, respectively, at an Al content of 58.5 at.%. Addition of Al beyond 64.0 at.% resulted in a change in crystal structure from B1 cubic to B4 hexagonal phase. The wear resistance improved gradually with the increase of Al in the Cr 1− x Al x N films. A combination of the abrasive and adhesive wear mechanism was proposed based on the SEM and EDS analysis of the wear track. The steady state dry coefficient of friction measured against a WC ball for the Cr 1− x Al x N films were in the range of 0.36–0.55, and the wear rate was in the 10 − 6 mm 3 N − 1 m − 1 range.