| Summary: | Temperature and atmosphere have a significant effect on the oxidation of MCrAlY (M = Ni, Co) bond coating. The initial growth behavior of the NiCrAlHf bond coat alloy was investigated at 1100 °C under different atmospheric conditions and using heating methods. A thick Al<sub>2</sub>O<sub>3</sub> oxide layer and large HfO<sub>2</sub> particles were observed, perhaps due to metastable oxide growth at low temperatures when using stepped heating. However, in air and water vapor atmospheres, the oxide scale was thinner and the HfO<sub>2</sub> precipitates were smaller in stepped heating than in constant heating. The size and distribution of the HfO<sub>2</sub> particles might have induced different microstructures, particularly voids within the oxide scale.
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