Influence of Ni content on the structure and properties of Cr-Ni-N coatings prepared by direct current magnetron sputtering

Cr-Ni-N coatings were deposited on 304 stainless steel substrates using a conventional direct current magnetron reactive sputtering system in nitrogen-argon reactive gas mixtures. The influence of Ni content (0 ≦ x ≦ 20 at.%) on the coating composition, microstructure, and tribological properties was investigated by glow discharge optical spectroscopy, X-ray diffraction and transmission electron microscopy, scanning electron microscopy (SEM), nano-indentation, and pin-on-disk tests. The results showed that microstructure and properties of coatings changed due to the introduction of Ni. The ternary Cr-Ni-N coatings exhibited solid solution structures in spite of the different compositions. The addition of Ni strongly favoured preferred orientation growth of <200>. This preferred orientation resulted from the formed nano-columns being composed of grains with the same crystallographic orientation, as confirmed by SEM cross-sectional observations. The mechanical properties including the nano-hardness and reduced Young's modulus decreased with increasing Ni content. Pin-on-disk tests showed that low Ni content coatings presented higher abrasion resistance than high Ni content coatings.