Structure and composition effects on pitting corrosion resistance of austenitic stainless steel after molybdenum ion implantation

316LVM, cold worked austenitic stainless steel, was implanted at 49 keV with molybdenum ions. Implantation doses varied between 1×1015 and 3.5×1016 ions cm−2. The structure of the implanted layer was examined by grazing incidence X-ray diffraction and the chemical composition was characterized by X-ray photoelectron spectroscopy combined with argon sputtering. Pitting corrosion studies were carried out on both unimplanted and implanted stainless steels in neutral chloride medium. The relationship between the pitting corrosion resistance, the structural and chemical modifications induced by Mo implantation was discussed. As a function of molybdenum ion dose, an expansion of fcc austenite was first observed, then above 8×1015 ions cm−2 a new bcc structure appeared and finally the implanted layer was partially amorphized. Electrochemical studies revealed that ion implantation enhances the pitting corrosion resistance. Increase in molybdenum implantation dose was beneficial up to 8×1015 ions cm−2 in improving the pitting corrosion resistance, beyond which it had a detrimental effect.