Oxide scale spallation behaviour of cast chromia-forming TaC-strengthened superalloys
Résumé
Six {Ni,Co}-based alloys containing TaC were subjected to high temperature oxidation in a thermobalance at 1250°C. The mass variations files were exploited to follow the progress of the spallation phenomenon during cooling. Oxides formed on surface were characterized. The oxide spallation started after an average of 300K of cooling, with a tendency of earliness for the nickel-richest alloys. These results are discussed by considering the effect of the base element and the natures and thicknesses of the external oxides. Tantalum threatens the scales adherence. The thicker scales formed on the cobalt-richest alloys resist more against spallation. The CrTaO4 oxide threatens more adherence when it is gathered at the interface.
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