Interdiffusivities and atomic mobilities in FCC Co-Mo-W alloys

By employing six groups of bulk diffusion couples together with electron probe microanalysis technique, the composition dependence of ternary interdiffusion coefficients in Co-rich fcc Co-Mo-W alloys at 1373 K was determined via the Whittle and Green method. The experimental interdiffusion coefficients were critically assessed to obtain the atomic mobilities of Co, Mo and W in fcc Co-Mo-W alloys by using the DICTRA (Diffusion-Controlled TRAnsformations) software package. Comprehensive comparisons between the calculated and experimental data show that a good agreement is obtained for diffusivities in binary Co-Mo and ternary Co-Mo-W systems. In addition, a further verification of the obtained atomic mobilities was carried out through comparing the model-predicted concentration profiles/diffusion paths of several diffusion couples with the corresponding experimental data. The results indicate that the atomic mobilities can reproduce the experiment data reasonably well. This work contributes to the establishment of a Co-based kinetic database for computational design of superalloys.