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

In order to investigate the diffusivity of both W and Re in Ni-based superalloys, interdiffusion coefficients in Ni-Al-X (X = Re, W) tertiary 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 gamma phase of Ni-2.5AI-43Re and of Ni-2.4Al-3.3W (mol%). the major interdiffusion coefficients were estimated to be D-ReRe(Ni) = 2.2 x 10(-15) m(2)/s and D-WW(Ni) = 9.9 x 10(-15) m(2)/s. It is found that D-ReRe(Ni) is much smaller than D-WW(Ni) .Also cross interdiffusion coefficients, vertical bar D-ReAl(Ni)vertical bar < vertical bar D-WAl(Ni)vertical bar and D-ReAl(Ni), D-WAl(Ni) < 0 were obtained in the gamma phase. The interdiffusion coefficients give the Wagner ' s interaction parameter between Re and Al, and between W and At as epsilon(ReAl) < epsilon(WAl) < 0, indicating that the ordering tendency exists between Al and Re, and between Al and W.