There are many techniques available for the surface modification of the substrate. One of the important ion implantation techniques is plasma source ion implantation (PSII). Ion implantation is a vacuum process in which a beam of ions is directed to the surface and introduced into it. This technique produces minimum invasion of the bulk properties of the substrate. Nitrogen plasma ion implantation treatments were done on the substrate, Cu-strengthened HSLA – 80 steel in various N-H mixtures at 100oC for 3 h. The ion implantation brought the mechanical, physical and chemical change in the substrate. This investigation showed that improvements in hydrogen embrittlement resistance could be obtained through plasma ion implantation. Plasma implantation caused incremental increase in the hardness, indicating nitrogen introduction in the substrate surface and subsurface. X-ray diffraction spectra of the treated samples revealed a shift in the primary peak indicating that the nitrogen was most probably resident as solute. The presence of nitrogen as well as surface defects produced by implantation caused a non-monotonic change in the hydrogen diffusivity. The presence of a high surface hardness possibly delayed crack initiation under hydrogen charging conditions. Keywords: Plasma ion implantation, hardness, hydrogen diffusivity, hydrogen embrittlement, HSLA Steel
