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 techniqu e for improving tribological properties of steels. In the case of C+ i mplantation at very high doses, amorphization and a carbonaceous layer can be formed on the surface, the latter of which reduces adhesion wh en like-on-like material contact conditions occur, thereby decreasing surface wear and friction. A study to determine the influence of C+ io n implantation at very high doses (exceeding 10(18) ions cm(-2)) on tr ibe-mechanical properties of AISI 440C steel is presented in this work . Ball-on-disc wear and friction tests using an AISI 440C steel ball s howed a decrease of wear with increasing dose of more than one order o f magnitude. A reduction in friction coefficient was also measured, fr om 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 o f a graphitic layer on the surface, responsible for the decrease in su rface wear and friction after ion implantation.