Optimizing the Oxidation Properties of FeCrAl Alloys at Low Temperatures

FeCrAl alloys are proposed candidate materials for liquid lead applications. Chromium is needed to assist the formation of a protective alumina layer, albeit has to be limited to avoid α′ precipitation. Reactive elements (RE) improve oxidation properties, but little is known about the RE effects at lower temperatures. An alloy matrix based on Fe–10Cr–4Al (wt%), with varying Zr, Y and Ti contents, was exposed to liquid lead up to 1 year in the temperature interval of 450–550 °C. It was found that the formation of protective alumina was dependent on the RE/carbon ratio. All alloys with ratios lower than unity showed poor oxidation properties due to the formation of Cr-carbides in the metal–oxide interface. A sufficiently high amount of Zr and Ti was shown to significantly improve the oxidation properties at both temperatures. The positive effect is related to the suppression of Cr-carbides by addition of stronger carbide formers.