A surface modified ODS superalloy by thermal oxidation for potential implant applications

In the present work attention is paid on the composition, structure and pro tective properties of alumina layer produced by high temperature oxidation on MA 956 superalloy (Fe-20Cr-4.5Al-0.5Ti-0.5Y(2)O(3) (wt %)). The combinat ion of good mechanical properties of this material and the excellent biocom patibility, the good wear and corrosion behavior of an outer alpha -alumina layer, limiting the release of ionic species and wear debris from the bulk material into the body-fluid environment, can make this material a candida te alloy for medical applications. Isothermal oxidation at 1100 degreesC in air of the alloy has led to the formation of a fine-grained, compact and a dherent alpha -alumina scale. Oxide nodules rich in Ti, Y, Cr, and Fe were found on the top of the surface. In vitro electrochemical corrosion experim ents showed good protective properties of the oxide scale. Moreover, no spa llation of the alumina layer was observed. This feature is significant cons idering that the alumina layer has to withstand very high compressive stres ses resulting from both growth and thermal stresses incorporated during coo ling. (C) 2001 Kluwer Academic Publishers.