Nitrogen ion implantation for the surface modification of 9Cr18Mo steel

Abstract The effect of nitrogen ion implantation on the electrochemical and fretting behavior of 9Cr18Mo steel has been studied. Anodic polarization measurement in a 0.1N sulphuric acid solution was used to evaluate the corrosion resistance of the steel before and after nitrogen ion implantation. Lower passive current density and higher corrosion potential were obtained on the implanted specimens. The best effect was observed on the fourth polarization scan in multipolarization tests, which correlated well with the nitrogen concentration depth profile determined by AES. The variation of corrosion current density vs corrosion time was also tested. The corrosion current density of the implanted specimen is two orders of magnitude lower than that of the unimplanted specimen, indicating that the corrosion rate of the implanted surfaces is much lower. Fretting tests were also used to evaluate the effect of nitrogen ion implantation. The fretting resistance was clearly improved after implantation.