Influence of Ni Deposition and Subsequent N+ Ion Implantation at Different Implantation Energies on Nano-Structure and Corrosion Behavior of 316 Stainless Steels

Nickel films of 300 nm thickness were deposited by electron beam evaporation at room temperature on 316 stainless steels. Corrosion studies of Ni coated 316 SS have been performed after N+ ion implantation at different energies of 20, 40, 60 and 80 keV. The structure and surface morphology of the films were evaluated using X-ray diffraction (XRD), atomic force microscope (AFM) and scanning electron microscope (SEM). X-ray diffraction (XRD) analysis showed formation of nickel nitride phases. The corrosion behavior of the samples was evaluated by potentiodynamic polarization test in 3.5% NaCl solution. The subsequent Tafel analysis revealed nobler open circuit potential and lower corrosion current density values with increase of beam energy. By increasing the implantation energy, diffusion effect enhances, hence, larger grains with smoother surfaces are formed. The smoother surfaces show higher resistance in the corroding medium. Increase in implantation energy was beneficial in improving the corrosion resistance.