Surface characterization and electrochemical studies of biomedical NiTi alloy coated with TiN by PIIID

TiN coatings were deposited on the surface of Ti–50.6 at.% Ni alloy by the advanced plasma immersion ion implantation and deposition (PIIID) technique to improve the wear and corrosion resistances. The surface characteristics and corrosion property of the samples were investigated by atomic-force microscopy (AFM) and electrochemical measurement. The AFM results showed that negative pulse bias voltage and N2/Ar flow rate greatly influence the surface roughness of the TiN films. Combined with the results of Tafel curves, anodic polarization curves and electrochemical impedance spectroscopy, we found that an excellent corrosion resistant TiN coating by PIIID technique could be obtained by varying the process parameters. The sample deposited at −20 kV, with 1:2 nitrogen to argon flow ratio, exhibited excellent anti-corrosion property, which had a more positive value of corrosion potential Ecorr, a higher value of polarization resistance Rp and a low corrosion current density Icorr. An appropriate equivalent circuit model was proposed to describe the corrosion process of the TiN coated samples in the present study.