Influence of W content on microstructure and surface morphology of hard Ni-W films fabricated by magnetron co-sputtering

Due to their unique mechanical, tribological, thermal, and anticorrosion properties, nickel-tungsten (Ni-W) alloy films have become indispensable for many industrial applications. The present study investigates the impact of W content on the microstructure and mechanical properties of Ni-W thin films. By co-sputtering of Ni and W on silicon wafers coated with a thin buffer layer (∼20 nm) of titanium (Ti), six Ni-W coatings were fabricated, ranging from pure Ni to pure W. The samples were characterized using energy dispersive spectroscopy, x-ray diffraction, scanning electron microscopy, atomic force microscopy, and microindentation. The results show that hardness of the Ni-W films is primarily a function of the W content, which changes the microstructure and surface morphology of the samples. When W concentration is smaller than 40 at. %, the Ni-rich samples have a face-centered cubic structure and the hardness increases with the W content. For the samples having 40