Abstract
A computer calculation was carried out to construct an equilibrium phase diagram of a Ni-Cr-W ternary system between 800 and 1700°C, on the basis of the experimentally determined phase equilibria between 1000 and 1200°C. The method developed by Kaufman and his collaborators was employed in the present calculation. Only sub-regular solution parameters of the three binary systems were used to describe the excess free energy of ternary solution phases such as liquid and three terminal solid solutions: nickel-rich fcc γ, chromium-rich bcc α1 and tungsten-rich bcc α2 phase. No ternary term was added to the excess free energy expression. The sub-regular solution parameters of fcc solid solution in the Cr-W binary system were determined to be gfccCr-W=hfccCr-W=9 000 cal/g-at. A line compound approximation was employed to describe the free energy of intermetallic compounds such as σ phase and β phase (Ni4W). The previously reported line compound parameter of σ phase in the Ni-Cr binary system was revised in addition to the determination of the σ phase parameter in the Ni-W binary system.
