Effect of nitrogen ion implantation on the corrosion resistance of titanium modified type 316L stainless steel in comparison with argon and oxygen ion implantation

Studies on nitrogen ion implanted (1 x 10(15), 1 x 10(16), 1 x 10(17) and 2.5 x 10(17) ions/cm(2)) titanium modified type 316L stainless steel (SS) showed an increase in the localized corrosion resistance of the material. Gracing Incidence X-ray Diffraction studies showed implanted nitrogen at the interstitial in the specimen implanted at 1 x 10(17) ions/cm(2) which showed the optimum corrosion resistance. Chromium nitride has been found in the dose of 2.5 x 10(17) ions/cm(2), which showed the inferior corrosion resistance. Argon and oxygen ion implantations were carried out to confirm whether the improvement in the localized corrosion resistance after nitrogen ion implantation was due to chemical effect produced by nitrogen or due to microstructural effect produced by ion implantation. The results showed that nitrogen ion implantation improved more than two fold increase in the localized corrosion resistance with low passive current density. XPS studies of the passive film of implanted specimen (optimum dose) showed the presence of oxynitrides along with oxides which could have contributed to the enhanced corrosion resistance. The argon and oxygen ion implantations did not improve localized corrosion resistance and was found detrimental with increase in doses.