Interdiffusion coefficients of the refractory elements in Ni-X-Y (X, Y=W, Re, Ru, Al) ternary systems, which were the fundamental systems of Ni-based superalloys, were estimated by a series of experiments using diffusion couples. The modified ternary Boltzmann-Matano method was used to analyze the experimental data. The cross interdiffusion coefficients were smaller than the main interdiffusion coefficients in all systems. Especially, the cross-interdiffusion coefficient DReRuNi was smaller, by an order of magnitude, than the main interdiffusion coefficient DReReNi in Ni-Ru-Re system. This result indicated that the thermodynamic interaction parameter (Wagner's interaction parameter) between Ru and Re was negligible, and implied that Ru did not affect the distribution behavior of Re into γ and γ' phases.

Diffusion of Refractory Elements in Ni-X-Y (X, Y: Re, W, Ru, Al) Ternary Alloys. M.Hattori, N.Goto, Y.Murata, T.Koyama, M.Morinaga: Materials Transactions, 2006, 47[2], 331-4