Abstract
The cyclic oxidation resistance of normal-grained cast Co-30Cr-5Al alloy and its microcrystallized film was investigated at 1000 °C in air. The results indicated that normal-grained CoCrAl alloy exhibited very poor resistance against cyclic oxidation. After only 2 cycles, the initially formed Al 2 O 3 scale severely spalled off, and then Cr 2 O 3 and CoCr 2 O 4 spinel were formed as a surface layer, while Al 2 O 3 only existed in the form of internal oxides. Acoustic emission measurements showed that the Al 2 O 3 scale formed on the normal-grained Co-30Cr-5Al alloy would crack and spall off only during cooling, and cracking and spalling at about 400°C. On the contrary, the microcrystallized film showed very excellent cyclic oxidation resistance. No AE single was detected during cooling from 1000°C even down to room temperature, which was consistent with the surface morphologies observed by SEM. This denoted that the microcrystallization can significantly improve cyclic oxidation resistance of Co-30Cr-5Al alloy.
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