NiAl Coatings Produced by Magnetron Sputtering from Mosaic Targets

In this study, NiAl-based intermetallic films were obtained by magnetron sputtering of mosaic targets, consisting of nickel and aluminum. Two-segment target consisted of nickel and aluminum semicircular parts; six-segment target was assembled from nickel and aluminum alternating bars. The structure and properties of coatings were evaluated depending on the type of mosaic target, target-to-substrate distance (Ht-s) and substrate material. NiAl grains had predominant (111) or (110) crystallographic orientation parallel to the substrate surface. Sputtering of the six-segment target led to the uniform elemental composition of the coatings. When using the two-segment target, the heterogeneous distribution of Ni and Al in NiAl over the substrate was observed. Ni-rich regions of the coatings had a fine-grained structure, while Al-rich areas predominantly consisted of larger columnar grains. As the Ht-s distance decreased, the morphology of the surface of all films changed from a rough island-type to a smoother one. The correlations between the texture, composition of films, and sputtering conditions are described. The obtained results are analyzed and explained based on fundamental principles of films growth during magnetron sputtering. The nanohardness of the films varied in a range from 6 to 12 GPa, and the coatings possessed high wear resistance.