Corrosion behavior of CrN coatings enhanced by niobium ion implantation

Metal plasma ion implantation (MPII) was successfully developed for improving wear, corrosion, and physical properties of engineering materials. In this study, CrN films were deposited by a cathodic arc evaporation (CAE) process, and Nb ions were implanted into the CrN films at 150 keV and (1–2)×1017 ions/cm2 using a metal plasma ion implantation apparatus. The electrochemical behavior of the Nb-implanted CrN films in a 3.5 wt.% NaCl solution was investigated by the potentiodynamic polarization measurement and electrochemical impedance spectroscopy (EIS). The corrosion resistance of Nb-implanted CrN was improved by the formation of amorphous and chemically inert Cr–Nb–N phases in the ion-implanted layer, which leads to the increase of polarization resistances and the decrease of capacitances in the EIS analysis. At the dose of 1×1017 ions/cm2, the Nb-implanted CrN possesses the best corrosion resistance due to the highest polarization resistance (2.53×106 Ω/cm2) and the lowest capacitance (1.4×10−5 F/cm2). Results of this study demonstrate the potential of metal plasma ion implantation in improving the corrosion resistance of the CrN coating without hampering its mechanical properties.