Changes in tribological properties of an AISI 440C martensitic stainless steel after ion implantation of carbon at very high doses

Ion implantation of N⁺ or C⁺ has been proven to be a suitable technique for improving tribological properties of steels. In the case of C⁺ implantation at very high doses, amorphization and a carbonaceous layer can be formed on the surface, the latter of which reduces adhesion when like-on-like material contact conditions occur, thereby decreasing surface wear and friction. A study to determine the influence of C⁺ ion implantation at very high doses (exceeding 10¹⁸ ions cm^-2) on tribo-mechanical properties of AISI 440C steel is presented in this work. Ball-on-disc wear and friction tests using an AISI 440C steel ball showed a decrease of wear with increasing dose of more than one order of magnitude. A reduction in friction coefficient was also measured, from 1.0 down to 0.4. C 1s spectra from XPS analyses showed the presence of C-C bonds in the ion-implanted samples, suggesting the formation of a graphitic layer on the surface, responsible for the decrease in surface wear and friction after ion implantation.