Influence of Cr on the oxidation of Fe3Al and Ni3Al at 500°C

The influence of chromium on the mechanical properties of the aluminides Fe3Al and Ni3Al has been studied extensively. In order to evaluate the role of Cr during the early stages of oxidation, Fe3Al and Ni3Al containing 2 and 4 at.% Cr were oxidized in dry air at 500degreesC for 6, 50, and 100 hr. The oxide scale on Fe3Al consists of a layer of Fe2O3 mixed with FeAl2O4 on top of a continuous layer of (Al, Cr)(2)O-3. Ni3Al is covered with a mixed layer of (Al, Cr)(2)O-3 and NiO/NiAl2O4 underneath a layer of NiO/NiAl2O4. Moreover, Cr induces the nucleation and growth of Fe2O3 and NiO particles at the oxide surface of Fe3Al and Ni3Al, respectively. This is due to enhanced cationic diffusion through the Cr-modified oxides. As a conclusion, additions of Cr zip to 4 at.% are detrimental to the oxidation behavior of both aluminides at 500degreesC.