Study on microstructure and corrosion resistance of Ti-doped nickel-based alloy coatings

The Ti-doped nickel-based alloy coating was prepared by plasma melting, and its microstructure was investigated by optical microscopy (OM) and X-ray diffraction (XRD). The effect of Ti content on the corrosion resistance of nickel-based alloy coating was investigated via electrochemical polarization curves, AC impedance spectra, and Mott-Schottky curves. The results show that Ti changes the selection preference of different crystalline planes and tissue morphology in the matrix phase, and the nickel-based alloy coating with Ti content of 1 wt% had the densest tissue and the most uniform distribution of precipitated phases. The analysis results of polarization curve and AC impedance spectra show that nickel-based alloy coating with Ti content of 1 wt% has the highest pitting potential, the highest charge transfer resistance, and the highest coating resistance, reflecting the best passivity. Meanwhile, an increase in Ti content significantly reduces the donor density of nickel-based alloy coating and weakens the electrical conductivity. This indicates that the passivation film has a low density of point defects and great corrosion resistance.