The interdiffusion of Re, W, Ru and Co in binary and pseudo-binary Ni-based alloys at 1523K, and the γ’-phase coarsening-kinetics of model superalloys at 1324K, was reported. Both Re and W concentration gradients caused up-hill Ru diffusion in the respective pseudo-binary diffusion couple, whereas a Ru concentration gradient promoted up-hill diffusion of W but not of Re. It was interesting that up-hill Re diffusion occurred under the influence of a Co concentration gradient, but the reverse effect was not observed. The cross interdiffusion coefficients, qualitatively determined from the up-hill diffusion profiles, were in reasonable agreement with those reported previously. A comparison of the interdiffusion coefficients in the binary and pseudo-binary diffusion couples showed that Ru and W decreased each other’s diffusivity whereas Co appeared to be more powerful barrier atoms than Ru for decreasing the Re diffusivity. It was evident that the coarsening kinetics of the γ’-phase in both Ru-free and Ru-containing model superalloys were controlled by diffusion, and Ru was found to have no effect upon the rate constant of γ’-phase coarsening.

Diffusion and γ’ Phase Coarsening Kinetics in Ruthenium Containing Nickel Based Alloys. E.Mabruri, S.Sakurai, Y.Murata, T.Koyama, M.Morinaga: Materials Transactions, 2008, 49[4], 792-9