Beneficial effects of rhenium additions on the cyclic-oxidation resistance of {beta}-NiAl + {alpha}-Cr alloys
- Univ. of New South Wales, Sydney, New South Wales (Australia). School of Materials Science and Engineering
This study reports the effects of up to 4 at.% rhenium addition on the cyclic-oxidation behavior of {beta}-NiAl+{alpha}-Cr alloys having a base composition (in at.%) Ni-40Al-17Cr. Tests were conducted in still air at 1100 C for up to 250 1-hr cycles. The ternary alloy (without rhenium addition) exhibited poor cyclic-oxidation resistance, undergoing extensive scale spallation and internal oxidation. Additions of rhenium considerably improved the oxidation behavior, reducing the extent of both scale spallation and internal oxidation. These beneficial effects increased with increasing rhenium content. Rhenium additions improved cyclic-oxidation resistance by both decreasing the solubility of chromium in the {beta} phase and causing the interdendritic {alpha}-Cr precipitates in the alloy microstructure to become more spheroidized and disconnected. These effects aided in preventing both interdendritic attack and the dissolution of the {alpha}-Cr precipitates from the subsurface region of the alloy. The maintenance of {alpha}-Cr precipitates at the alloy-scale interface decreased the extent of scale spallation by providing a lower coefficient of thermal-expansion (CTE) mismatch between the alloy and the Al{sub 2}O{sub 3}-rich scale.
- OSTI ID:
- 665162
- Journal Information:
- Oxidation of Metals, Vol. 50, Issue 5-6; Other Information: PBD: Dec 1998
- Country of Publication:
- United States
- Language:
- English
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