Diffusion of Refractory Elements in Ni--X--Y (X, Y: Re, W, Ru, Al) Ternary Alloys

Interdiffusion coefficients of the refractory elements in Ni-X-Y (X, Y=W, Re, Ru, Al) ternary systems, which are the fundamental systems of Ni-based superalloys, were estimated by a series of experiments using diffusion couples. The modified ternary Boltzmann--Matano method was employed for analyzing the experimental data. The cross interdiffusion coefficients were smaller than the main interdiffusion coefficients in all systems. Especially, the cross interdiffusion coefficient ?DReRuNi is much smaller by an order of magnitude than the main interdiffusion coefficient ?DReReNi in Ni--Ru--Re system. This result indicates that the thermodynamical interaction parameter (Wagnerʹs interaction parameter) between Ru and Re is negligible, and implies that Ru does not affect the distribution behaviour of Re into (gamma) and (gamma)ʹ phases.