TRIBOLOGICAL EFFECTS OF YTTRIUM AND NITROGEN ION-IMPLANTATION ON A PRECIPITATION HARDENING STAINLESS-STEEL

Yttrium, nitrogen and combined yttrium and nitrogen implantations have been carried out on an ASTM A286 precipitation hardening iron base alloy to evaluate the benefits in their tribological behaviour. Microindentation tests have shown a significant 20%-60% increment in hardness on the nitrogen implanted material, with a limited improvement in elastic recovery of the indentation. An abrasive test on the same material has also produced a 50% reduction in scratch depth. Y+ and Y+ + N+ implantations also hardened the material but to a lesser extent. Reciprocating ball on disk friction and wear testing at 400-degrees-C resulted in very severe damage in all cases. X-ray photoelectron spectroscopy analyses combined with Ar sputtering have disclosed that nitrogen is mainly in a nitrided form, yttrium remains oxidized at the surface, below which there is an apparent increase in the metallic bond.