Thermodynamic Equilibrium Calculation Method for Prediction of Sigma Phase in Commercial Ni-Co-Cr Base Superalloys

This paper try to predict the formation of σ phase on the basis of thermodynamic equilibrium calculation. A power series model was chosed to express the excess free energy of multi-component non-ideal phase. All data including the interaction coefficient in binary and ternary alloy system were obtained by phase diagram fitting method. New method has the ability to predict phase formation correctly and enough precisely for all Ni-Co-Cr base sup-eralloys.