In order to design for the Ruthenium (Ru)-bearing nickel-base superalloys, a series of phase estimation equations for γ and γ′ phases in Ru-bearing nickel-base superalloys were established by regression analysis of data obtained by the electron-probe X-ray micro-analysis (EPMA). The partitioning ratios of alloying elements in Ru-bearing superalloys, and their temperature dependencies were experimentally obtained. The prediction equations for the partitioning ratios of alloying elements, and for the aluminum content in γ′ phase at arbitrary temperatures were developed. By using these equations and the lever rule of chemical compositions for the γ and γ′ phases, the compositions and volume fractions of γ and γ′ phases in equilibrium for Ru-bearing Ni-base superalloys were successfully estimated for various alloy compositions and temperatures. The estimated compositions and volume fractions of γ and γ′ phases showed a good agreement with the values obtained from EPMA and X-ray analysis.
