Solidification characterization of a new rapidly solidified Ni–Cr–Co based superalloy

The solidification characterization of a new rapidly solidified Ni–Cr–Co based superalloy prepared by plasma rotating electrode process was investigated by means of optical microscope, scanning electron microscope, and transmission electron microscope. The results show that the solidification microstructure changes from dendrites to cellular and microcrystal structures with decreasing powder size. The elements of Co, Cr, W and Ni are enriched in the dendrites, while Mo, Nb and Ti are higher in the interdendritic regions. The relationships between powder size with the average solid–liquid interface moving rate, the average interface temperature gradient and the average cooling rate are established. Microsegregation is increased with larger powder size. The geometric integrity of MC′ type carbides in the powders changes from regular to diverse with decreasing powder size. The morphology and quantity of carbides depend on the thermal parameters and non-equilibrium solute partition coefficients during rapid solidification.

► The relations of solidification thermal parameters with powder size are established.
► The relation of non-equilibrium solute partition with powder size is investigated.
► The solidification microstructure is related to thermal parameters.
► The segregation behavior is linked to non-equilibrium partition coefficients.
► The morphology and quantity of carbides depend on the above combined factors.