Nanostructured CrAlN films prepared at different pulse widths by pulsed DC reactive sputtering in facing target type system

Abstract

CrAIN films have been prepared using a pulsed DC reactive sputtering in FTS system with Cr/Al alloy (= 50/50 at%) targets in a mixed atmosphere of Ar and N2. The effects of pulse width on the film structure and properties have been investigated. XRD analyses were carried out to determine the phases and texture of the films. Transmission electron microscopy studies were carried out for selected films. In order to investigate the relationship between the mechanical properties and microstructure of the films, the hardness was measured by a nanoindentation system. Films prepared at lower pulse widths, exhibited fcc-CrN structure. In contrast, films that were prepared at higher pulse widths showed a mixed structure of hcp-AIN, hcp-Cr2N and a small amount of fcc-CrN phases. Plastic hardness, Hpl, of the films ranged between 32 to 41 GPa while the Young's modulus, EIT of the films ranged from 320 to 340 GPa. Increasing the pulse width also resulted in an increase in the film's internal stress. In addition, the grain size of the samples decreased with increasing pulse width. Consequently, the film deposited at higher pulse width exhibited high hardness of 41 GPa, H3/E2 ratio of ∼0.6 and relatively lower internal stress of -3.5 Gpa. These results indicated that changing the pulse width can strongly affect structure and properties of CrAIN films, resulting in a good combination of mechanical and tribological properties, under proper conditions in a pulsed DC Balanced Magnetron Sputtering system. © 2008 The Japan Institute of Metals.