Optimizing the Oxidation Properties of FeCrAl Alloys at Low Temperatures
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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.
KeywordsFeCrAl Reactive elements Cr-carbides Alumina
Sandvik Heating Technology AB is greatly acknowledged for providing model alloys and know-how. The authors are particularly thankful for the kind help provided by F. Rave, D. Chandrasekaran, T. Helander, R. Berglund and P. Byhlin. O. Karlsson (SEM and EBSD) and F. Lindberg (FIB-SEM and TEM), both at Swerea KIMAB, are thanked for helping out with microscopy analyzes. The authors are also grateful for the fruitful input and guidance from Prof. J. Wallenius (Div. Reactor Physics, KTH), adj. Prof. R. Pettersson (Jernkontoret and Div. Surface and Corrosion Science, KTH) and adj. Prof. M. Lundberg (Sandvik Materials Technology AB and Div. Surface and Corrosion Science, KTH). The work was funded and supported by Euratom FP7 project MatISSE (Reference No. 604862) and the strategic innovation program “Metalliska Material,” a joint effort by Vinnova, Formas and the Swedish energy agency (Energimyndigheten).
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