Oxide scale spallation behaviour of cast chromia-forming TaC-strengthened superalloys

Six {Ni,Co}-based alloys containing TaC were oxidised at 1250°C. The mass variations files were exploited to follow the progress of the spallation of the oxide scales during cooling. The oxides formed on surface were characterised. On average, spallation started after a 300 K cooling, at higher temperature for the nickel-richest alloys than for the others. These results are discussed by considering the effect of the base element and the natures and thicknesses of the external oxides. Tantalum has a negative influence on the scales adherence. The thicker scales formed on the cobalt-richest alloys are less affected by spallation. The CrTaO 4 oxide is more deleterious for the adherence of the external oxide scale when it is gathered at the interface.