Abstract
The kinetics and products of oxidation of alloys in the Co-Cr-Al system have been studied and four mechanisms of oxidation identified. For the first mechanism, the rate-controlling process is cation diffusion of cobalt cations through CoO, and the main oxidation product is CoO. In the second mechanism, cation diffusion through CoO is still rate controlling, but the oxidation is strongly inhibited by an inner discontinuous spinel layer. The major oxidation products are CoO and CoCr2O4. The third mechanism of oxidation consists of preferential oxidation of chromium coupled with internal oxidation of aluminum while the fourth mechanism is the preferential oxidation of aluminum with the subsequent formation of Al2O3 scales, providing the best oxidation resistance. From the oxidation data obtained, an “oxide map” from which the oxidation behavior of various alloys may be deduced is drawn for the Co-Cr-Al system at 1100°C.
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Wallwork, G.R., Hed, A.Z. Mapping of the oxidation products in the ternary Co-Cr-Al system. Oxid Met 3, 213–227 (1971). https://doi.org/10.1007/BF00603522
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DOI: https://doi.org/10.1007/BF00603522