Interdiffusion in fcc Ni-X (XÂ =Â Rh, Ta, W, Re and Ir) alloys

The interdiffusion coefficients in binary face-centered cubic (fcc) Ni-X (X = Rh, Ta, W, Re and Ir) alloys at 1473, 1523, 1573 and 1623 K were measured by using semi-infinite diffusion couples together with the Sauer-Freise method. A scientific method was employed to evaluate the errors of the determined interdiffusivities by considering the error propagation. The measured interdiffusion coefficients agree in general with the literature data. In order to find out the possible substitutional element for Re in Ni-based superalloys, a comprehensive comparison among the interdiffusion coefficients in fcc Ni-X (X = Nb, Mo, Ru, Rh, Pd, Ta, W, Re, Os, Ir and Pt) alloys with 6 wt% X at 1473-1623 K was conducted. The comparison results indicate that fcc Ni-6 wt% Os alloys exhibit the lowest diffusion coefficient, followed by Ni-6 wt% Re and Ni-6 wt% Ir alloys. The further analysis on the variation of interdiffusion coefficient with its influence factors including alloying concentration, temperature, atomic number, activation energy, atomic radius and compressibility was also performed.