Application of thermodynamic calculations to study high temperature behavior of TaC-strengthened Co-base superalloys

A database for cobalt-base superalloys was built by combing the binary and ternary thermodynamic descriptions available in the SSOL (SGTE) database and from the literature. Using this database, results of thermodynamic calculations for several cobalt-base superalloys were compared to the experimentally observed microstructure of the alloys after homogenization at high temperatures and quenching. Three examples are presented: prediction of phase equilibria versus temperature and composition; selection of highly refractory materials using isothermal sections; and evaluation of local melting temperature in the case of skin formation of Co-base alloy during air oxidation at 1300°C. The agreement between calculated prediction and experimental observation is satisfactory.