Improvement of wear and hardness of steel by nitrogen implantation

This paper reports a study of the influence of atomic nitrogen implantation on the improvement of hardness and wear of AISI 8642 steel. The hardness and wear tests were carried out over the dose range 10(17) -7 x 10(17) ions/cm(2) and energy 200 keV. Characterization of the surface and depth profiling of the implanted samples was performed using RBS and XRD techniques. Tribological tests for measuring friction and wear were made on a pin-on-disk stand with different loads for implanted and non-implanted samples. Hardness was measured with a Vickers diamond Square-faced pyramid indenter. Nitrogen implantation of steel increased the hardness by about 150% in comparison to the non-implanted samples. The influence of a 'long-range effect' established beyond the implanted zone during the ion implantation process on the increase of hardness was discussed. No improvement of the friction coefficient was observed in the steel samples due to nitrogen implantation. On the other hand, the wear at a dose 7 x 10(17) ions/cm(2) decreased by a factor of about 20 times compared with the non-implanted steel. (C) 2004 Elsevier Ltd. All rights reserved.