Diffusion of refractory elements in Ni-Al-X (X:Re,W) ternary alloys

Abstract

In order to investigate the diffusivity of both W and Re in Ni-based superalloys, interdiffusion coefficients in Ni-Al-X (X = Re, W) ternary system, which is the fundamental system of Ni-based superalloys, were measured by an experiment using diffusion couples. A modified ternary Boltzmann-Matano method was employed for the evaluation of the interdiffusion coefficients. In the y phase of Ni-2.5Al-4.3Re and of N1-2.4Al-3.3W (mol%), the major interdiffusion coefficients were estimated to be D̃ReReNi = 2.2 × 10-15 m2/s and D̃WWNi = 9.9 × 10-15 m2/s. It is found that D̃ReReNi is much smaller than D̃ WWNi. Also cross interdiffusion coefficients, |D̃ReAlNi| < |D̃ReAlNi| and D̃ReAlNi, D̃ReAlNi < 0 were obtained in the γ phase. The interdiffusion coefficients give the Wagner's interaction parameter between Re and Al, and between W and Al as |ReAl < |WAI < 0, indicating that the ordering tendency exists between Al and Re, and between Al and W. © 2005 The Japan Institute of Metals.