Effect of Hf and Ta on Ni-based superalloy powders

The effect of Hf and Ta modifying on the microstructure and composition of Ni-based superalloy powders was investigated. The element concentrations on the powder surface and subsurface were quantitatively characterized by the Auger electron spectroscopy, and cross sections of powders were observed by the electron probe microanalysis. The results show that Hf and Ta hardly change the morphology of powders, but significantly change the powder surface and subsurface composition. Hf and Ta enhance the volume fraction of MC carbides in powders, thereby reducing the concentrations of C, Ti, and Nb on the powder surface and subsurface, which effectively inhibits the formation of the prior particle boundary during HIP. It reduces crack sources and thus improves the mechanical properties of the alloy.