Successive ion implantation of high doses of carbon and nitrogen on steels

HSS and stainless steel samples were successively implanted with high doses of carbon and nitrogen. Different sequences of implantation (C+, C++N2+, N2++C+ and N2++C++N2+) were carried out in order to achieve CxNy layers of ultra-high hardness. The bonded states of carbon and nitrogen were studied by XPS spectroscopy. The tribological behaviour was measured by means of ball-on-disc and microhardness tests. The microhardness tests showed that increases in hardness are highly influenced by the implantation order. None of the sequences tested led to a hardness increase higher than that for simple carbon implantation. When nitrogen was implanted into carbon-implanted steel, the result was a huge decrease in surface hardness. Ion implantation of high doses of nitrogen and carbon brought about a decrease in the friction and wear coefficients. The samples for which carbon was implanted in the last step showed the lowest friction and wear coefficients.