The stress and spalling behavior of the oxide scale formed on polycrystalline Ni3Al

The residual stress in the oxide scale formed on polycrystalline Ni3Al in air in the range of 900-1200 degrees C was determined at room temperature using optical fluorescence piezospectroscopy. The stress was found to be almost independent of lime or temperature of oxidation. In contrast, the spalling behavior was strongly dependent on the oxidation temperature, not occurring below 1100 degrees C and profusely at 1200 degrees C. In the intermediate temperature regime (similar to 1100 degrees C), spallation of the oxide scale occurred preferentially in the vicinity of grain boundaries in the Ni3Al. This is attributed to a buckling instability driven by the residual thermal mismatch stress and induced by both void formation and a non-planar interface structure resulting from preferential diffusion along the Ni3Al grain boundaries. Copyright (C) 1996 Acta Metallurgica Inc.