The effect of an aluminizing treatment on the oxidation behavior of carbon-nitrogen free Fe-12Ni-9Co-10W alloy has been investigated in steam at 973 K for 28 Ms. An FeAl layer with a thickness of 70 μm was observed to form on the alloy surface during aluminizing treatment, which consisted of hot pressing of pure Al foil of 50 μm thickness on to the sheet specimens at 523 K, and subsequent diffusion annealing at 1373 K for 3.6 ks in vacuum of 10-4 Pa. The sheet specimens subjected to the aluminizing treatment exhibit excellent oxidation resistance in steam at 973 K, resulting from the formation of very thin Al2O3 scale. Oxidation tests were carried out using specimens with a thin layer of FeAl, and specimens with no FeAl layer but different Al concentrations at the alloy surface. Excellent oxidation resistance was observed due to Al2O3 scale formation when the FeAl layer was present or the Al concentration at the alloy surface with no FeAl layer was higher than 11%. When the Al concentration at the alloy surface with no FeAl layer decreased below 11%, thick scale of Fe3O4 and Fe2O3 formed during oxidation.
