Experimental and thermodynamic study of the high temperature microstructure of tantalum containing nickel-based alloys

Experiments and thermodynamic calculations were performed on three nickel-based alloys containing chromium, carbon and tantalum. Solidus and liquidus temperatures, and natures and surface fractions of the carbides after exposure for 100 h at 1000, 1100 and 1200 ∘C were determined for each alloy. These results are compared with calculated results, using a thermodynamic database. Good agreement was generally found for the solidus temperatures but less good agreement for the liquidus ones. For alloys containing chromium carbides alone, carbide fractions and matrix compositions correspond to calculation results. But the presence of tantalum carbides in the third alloy was not predicted by calculations.