Multi-component (Al,Cr,Nb,Y,Zr)N thin films by reactive magnetron sputter deposition for increased hardness and corrosion resistance

Abstract

Multi-component nitride thin films in the Al–Cr–Nb–Y–Zr system with non-equimolar composition have been deposited by reactive dc magnetron sputtering. The substrate temperature and substrate bias have been varied, from room temperature to 700 °C and from 0 to −200 V respectively. The relationship between these varied growth conditions on the structure, morphology, mechanical and corrosion properties of the films have been probed.All films consisted of a single solid solution with a NaCl-type structure, as shown by X-ray diffraction. However, elemental energy dispersive spectroscopy maps, obtained in the scanning transmission electron microscope, indicated that there could be partial segregation of Al, Cr and Y atoms within the grains. The microstructure of the films became denser, more fine-grained and smoother as the bias and temperature were increased. Nanoindentation showed that the hardness of the films increased with both bias and temperature, reaching a maximum of 27 ± 2 GPa. The corrosion resistance of the films, studied by performing potentiodynamic polarisation curves in 1 M HCl, was also found to be improved when compared to a commercially available hyper-duplex stainless steel and a ternary reference (Nb,Zr)N thin film as well.