Manufacture, microstructure and mechanical properties of Mo–W–N nanostructured hard films

Mo1−xWxNy (x = 0–0.67) hard films were fabricated on wafers of silicon and high speed steel by dc magnetron sputtering technique. The effect of tungsten concentration on the phase composition, microstructure, surface morphology, hardness, adhesion, and corrosion resistance of the films was studied by X-ray diffraction, scanning electron microscopy, nano-indentation, and scratch test. It was found that if the W concentration (x) in the film is in the range of 0–0.52, the films exhibit fcc (Mo,W)Ny single phase where larger W atoms substituted Mo atoms in fcc MoNy. At higher x values (x > 0.52) the films exhibit a two-phase structure consisting of fcc (Mo,W)Ny and pure bcc tungsten phase. The hardness of the Mo1−xWxNy films increases at first with increasing x, and then decreases after passing a maximum. The maximum hardness of 47 GPa is obtained at x = 0.37 corresponding to an adhesion strength of 60 N. The Mo–W–N coated high speed steel has a lower corrosion current density and higher corrosion potential than the bare high speed steel substrates.