Published online by Cambridge University Press: 03 March 2011
The pseudo NiAl binary phase was formed in a nickel-based superalloy by pack cementation. Scanning electron microscopy, transmission electron microscopy, x-ray diffraction, electron probe microanalysis, and positron annihilation technique were used to characterize the pseudo NiAl binary phase. Based on reasonable assumptions, the chemical interdiffusivities of the pseudo NiAl binary phase were then assessed by means of the modified Wagner’s method. The results showed that the chemical interdiffusivities of the pseudo NiAl binary phase were about two orders of magnitude lower than those reported by others. The analysis indicated that the change in thermodynamic properties due to the additions of the microalloying atoms originally present in a superalloy could be responsible mainly for a decrease in chemical interdiffusivities.