Surface modification of a FeCrAlY-alloy by ion implantation and oxidation for potential implant applications

摘要

Oxide Dispersion Strengthened (ODS) high temperature alloys are excellent materials for high temperature applications due to their good mechanical and corrosive behavior in aggressive environments. The latter is due to the ability to form a dense, adherent and protective alumina layer. It is also known that alumina is a material with superior biocompatibility, besides the high hardness. This combination makes this type of ODS alloy, in combination with pre-oxidation at high temperatures, a potential candidate for articulating (load bearing) implants, such as hip and knee prostheses. In this study the ODS alloy PM 2000 (Fe-Cr-Al-Y{sub}2O{sub}3) was subjected to different high temperature oxidation treatments with the aim to form a dense and adherent alumina layer. Attention was paid to the as-received material and to material implanted with aluminum or niobium. Ion implantation was used to attempt to achieve a pure alumina scale without the presence of small amounts of other oxide compounds. Results show that after isothermal oxidation the non-implanted material forms a dense and adherent α-alumina with nodules on the surface, which are rich in iron and chromium or titanium and yttrium. Due to the presence of these nodules the surface roughness increased to values higher than recommended for load bearing surfaces such as hip and knee replacements. It was found that increasing the aluminum concentration in the subsurface layer by ion implantation did not lead to the formation of a nodule-free surface morphology. Implantation of niobium successfully suppressed the nodule formation during isothermal oxidation only at 900°C. At higher temperatures no differences could be observed between the oxide scale formed on non-implanted and niobium-implanted material.