The roles of passive layers in regulating the electrochemical behavior of Ti5Si3-based nanocomposite films

Abstract

A novel TiC–Ti₅Si₃ nanocomposite film was successfully engineered onto a Ti–6Al–4V substrate using a double glow discharge plasma technique. This type of film exhibits a self-toughened, hierarchical structure, consisting of cauliflower-like Ti₅Si₃ grains together with TiC nanoparticles distributed at the boundaries. The electrochemical behavior and electronic properties of the passive layers formed on the TiC–Ti₅Si₃ nanocomposite film were compared to a monolithic Ti₅Si₃ film and uncoated Ti–6Al–4V in a 3.5 wt% NaCl solution by various electrochemical analytical techniques, including low frequency impedance, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and Mott–Schottky analysis. The results showed that the corrosion resistance of the TiC–Ti₅Si₃ nanocomposite film was comparable to that of the monolithic Ti₅Si₃ film, but was significantly higher than that of uncoated Ti–6Al–4V. The TiC–Ti₅Si₃ nanocomposite film is thus an attractive candidate for surface protection of components against mechanical and chemical attacks.