Mechanical and corrosion-resistant properties of Ti–Nb–Si–N nanocomposite films prepared by a double glow discharge plasma technique

Two quaternary Ti–Nb–Si–N nanocomposite films, with differing Nb contents, were deposited onto Ti–6Al–4V substrates using a double glow discharge plasma technique. The chemical composition and microstructure of the films were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The Ti–Nb–Si–N films exhibit a typical nanocomposite structure, in which nanocrystalline (Ti,Nb)N grains, ~8 nm in diameter, were embedded in an amorphous SiNx matrix. The hardness and elastic modulus of the Ti–Nb–Si–N nanocomposite films were measured by nanoindentation. The electrochemical behavior of the Ti–Nb–Si–N nanocomposite films was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5 wt% NaCl solution. For comparative purposes, these measurements were also performed on TiN and Ti–Si–N films. The results show that the Ti–Nb–Si–N nanocomposite films exhibit both higher hardness and corrosion resistance than the TiN and TiSiN films, which could be attributed to their nanocomposite structure together with the incorporation of both Nb and Si into the TiN films.