Influence of pulsed substrate bias on the structure and properties of Ti–Al–N films deposited by cathodic vacuum arc

Abstract

Ti–Al–N films were deposited by cathodic vacuum arc (CVA) technique in N2 atmosphere with different pulsed substrate bias. The influence of pulsed substrate bias (0 to −800V) on the deposition rate, surface morphology, crystal structure, and mechanical properties of the Ti–Al–N films were systematically investigated. Increasing pulsed bias voltage resulted in the decrease of deposition rate but the increase of surface roughness. It was found that there was a strong correlation between the pulsed bias and film structure. All the films studied in this paper were composed of TiN, AlN, and Ti–Al–N ternary phases. The grains changed from equiaxial to columnar and exhibited preferred orientation when the pulsed bias increased. With the increase of pulsed bias voltage, the atomic ratio of Ti to Al element increased gradually, while the N to (Ti+Al) ratio decreased. The composite films present an enhanced nanohardness compared with binary TiN and ZrN films. The film deposited with pulsed bias of −200V possessed the maximum scratch critical load and nanohardness. The minimum friction coefficient with pulsed bias of −300V was obtained.