SELF-DIFFUSION OF NICKEL ON THE INTERNAL INTERFACES IN A SUPERALLOY BASED ON MULTIALLOYED NI3AL INTERMETALLIDE

In-layers radiometry and high-resolution autoradiography were used to examine the self-diffusion along the internal interfaces in the single crystal ingots of Ni3Al-based superalloy obtained by high-gradient or low-gradient solidification. The permeability. by diffusion. of the i nterfaces was measured in the temperature range 700-900 degrees C and the activation energies were calculated. The structure of the primary precipitations was examined through electron microprobe analysis and t he precipitated cl phases were identified. The effect of the temperatu re gradient of solidification on the diffusion parameters is discussed . Ni3Al-based (alloyed) intermetallide (ordered gamma' phase) is known as the general strengthening phase in the modern nickel-based superal loys. Increasing the phase fraction and making the phase chemistry mor e complex and favorable were the very means that to a large extent con trolled improving of the service characteristics of the superalloys du ring their 50-year history. In these terms. one can realize why so muc h interest was paid during the last Ii years to the development of the ahoy completely or almost completely comprised by this intermetallide .