Long-term oxidation of an as-cast Ni3Al alloy at 900 C and 1100 C

The oxidation behavior of a cast nickel aluminide alloy, IC221M, was examined after long-term aging in air for up to 16,600 hours at 900C and 5000 hours at 1100C. The oxidation products were identified using X-ray diffraction and energy-dispersive X-ray (EDX) spectroscopy with multivariate statistical analysis. At 900C, NiO dominates the oxidation products initially, but at longer times, NiAl 2 O 4 spinel and Al 2 O 3 predominate and remain stable for times up to 16,600 hours. Cross-sectional observation confirmed that a continuous surface oxide that is mostly a mixture of Al 2 O 3 and NiAl 2 O 4 protects the base metal. In its initial stages, the oxidation process at 1100C is qualitatively similar to that at 900C but with faster kinetics. However, as aging proceeds, NiO spalls freely from the surface, and a protective continuous oxide scale does not form. The oxidation mechanism can be qualitatively understood by the selective oxidation mechanism maps developed by Giggins and Pettit.

Long-term oxidation of an as-cast Ni3Al alloy at 900 C and 1100 C Conference Paper