Diffusion of Co, Ru and Re in Ni-based superalloys: A first-principles study

Self and impurity diffusivities in Ni-based superalloys have been investigated by first-principles calculations within five-frequency model. The vacancy formation energy, migration energy, correlation factor, solute-vacancy binding enthalpies and entropies in vacancy-mediated diffusions have been considered. The positive solute-vacancy binding energies for Co, Ru and Re indicated that the solute-vacancy pair is not a favorable binding. From the electronic point of view, the origination of the repulsive interaction between solute and vacancy has been comprehensibly expatiated on, which possibly accounts for the low diffusivity of Re element. The calculated self and impurity diffusion coefficients show a good consistent with the reported data from experiments and it is found that the trend in diffusivity is DCo > DNi-self > DRu > DRe.