Thermal oxidation treatments in the development of new coated biomaterials: Application to the MA 956 superalloy

Abstract

Reducing metal ion release and minimizing friction of orthopaedic implant bearing surfaces is of prime concern for long-term performance. Inert ceramic bearing surfaces eliminate these issues, and thus, various surface coating methods are being investigated. In-situ thermal oxidation treatment (1100°C) of MA 956 which produces a fine but tightly adherent α-alumina scale is characterized. This layer enhances the in vitro corrosion resistance up to three orders of magnitude with respect to Ti-Al-V alloys. Additionally, compressive residual stresses are approximately 5000 MPa. The existence of elevated compressive residual stresses in the coating, without compromising the coating-substrate adhesion, guarantees its integrity during tensile deformation and should contribute to better wear and fatigue resistance.