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PM 2000 is a Ni-free oxide dispersion strengthened Fe-20Cr-5Al alloy able to develop a fine, dense and tightly adherent α-alumina scale during high-temperature oxidation. Despite the high temperature involved during thermal oxidation (1100°C), microstructural changes in the candidate material, a hot rolled product, hardly occurs. Consequently, the good mechanical properties of the as-received material are not significantly affected. Moreover, due to the high compressive residual stresses at the alumina scale, an increase in the fatigue limit from 500 to 530 MPa is observed. Such stresses also account for the high capability of the coating/metal system to withstand more than 1% tensile deformation without cracking. The biocompatibility of the alloy was assessed in comparison to commercial alumina. Saos-2 osteoblast-like cells were either challenged with PM 2000 particles, or seeded onto PM 2000 (with and without scale) solid samples. Viability, growth, and ALP release from cells were assessed after 3 or 7 days, while mineralization was checked at 18 days. This study has demonstrated that PM 2000 with and without scale are capable of supporting in vitro growth and function of osteoblast-like cells over a period of 18 days. Results from this study suggest that the resulting alumina/alloy system combines the good mechanical properties of the alloy with the superior biocompatibility of the α-alumina, for which there is very good clinical experience. © 2004 Elsevier Ltd. All rights reserved.

This paper presents the influence of substrate roughness on the corrosion behaviour of the Al2O3/MA 956 system. An alumina layer of thickness 1-5μm was generated of the MA956 alloy by thermal oxidation at 1100°C using different exposure times. This Al2O3/MA 956 system with a polished substrate has shown excellent corrosion behaviour in a physiological fluid, due to the fact that the α-Al2O3 layer formed is dense, continuous and firmly adhered to the substrate, irrespective of the scale thickness. This good adherence allows it to withstand potentials above 1.7 V. Specimens with rough finish substrate and treatment times above 10 h present spallation of the alumina layer at the crests of the roughness profile. In this case a mixed corrosion behaviour between an alumina coated material and one with a passive layer is observed. In both types of specimens, rough and smooth, once the passivation layer is broken the repassivation capacity of the substrate is ensured due to the high chromium content of the alloy, under oxygenation conditions.