Transient oxidation of Al-deposited Fe-Cr-Al alloy foil

摘要

The oxide phases formed on an Al-deposited Fe-Cr-Al alloy foil and an Fe-Cr-Al alloy foil of the same levels of Al and (La+Ce) contents, and their oxidation kinetics have been studied in air at 1173 and 1373 K using TGA, XRD and SEM. Al deposition promotes the growth of metastable aluminas (θ-Al{sub}2O{sub}3, γ-Al{sub}2O{sub}3). Scales consisting of θ-Al{sub}2O{sub}3 and a small amount of α-Al{sub}2O{sub}3 develop on the Al-deposited foil at 1173 K and exhibit the whisker-type morphology. In the early stage of oxidation at 1373K, thick scales consisting of θ-Al{sub}2O{sub}3 and α-A1203 grow rapidly on the Al-deposited foil. The transformation from θ-Al{sub}2O{sub}3 to α-Al{sub}2O{sub}3 is very fast, and the scales result in only α-Al{sub}2O{sub}3. In contrast, α-Al{sub}2O{sub}3 scales containing a minor amount of FeAl{sub}2O{sub}4 develop on the alloy foil. The growth rate of α-Al{sub}2O{sub}3 scales on the Al-deposited foil is smaller than that on the alloy foil and very close to that on NiAl at 1373 K.