Phase formation in nitrogen ion implanted Ti-Al-Zr alloy and modification of corrosion property

In the present investigation, surface modification of Ti-Al-Zr alloy with nitrogen ions is considered as a method to improve its performance with respect to corrosion. Nitrogen ions were implanted on Ti-Al-Zr alloy at an energy of 65 keV at different doses between 1 x 10¹⁶ and 1 x 10¹⁷ ions/cm². The valence states of nitrogen, titanium and carbon on the sample surfaces were analyzed by X-ray photoemission spectroscopy (XPS). Glancing angle X-ray diffraction (GAXRD) was employed on the as-implanted and annealed specimens to understand phase formation with increasing doses and annealing temperatures. The implanted samples were subjected to electrochemical study in a solution with pH = 10 in order to determine the optimum dose that can give good corrosion resistance in a simulated nuclear reactor condition. The passive current density and area of the repassivation loop were found to decrease as the doses increased. Nitrogen ions implantation enhanced the passivation and reduced the corrosion kinetics of the alloy surface with increasing tendency for repassivation. The corrosion resistance of as-implanted and annealed samples was better than that of as-implanted samples. Nature of the surface and reason for the variation and improvement in corrosion resistance were discussed in detail.