Eutectic Formation During Solidification of Ni-Based Single-Crystal Superalloys with Additional Carbon

gamma/gamma' eutectics' nucleation behavior during the solidification of a single-crystal superalloy with additional carbon was investigated by using directional solidification quenching method. The results show that the nucleation of the gamma/gamma' eutectics can directly occur on the existing gamma dendrites, directly in the remaining liquid, or on the primary MC-type carbides. The gamma/gamma' eutectics formed through the latter two mechanisms have different crystal orientations than that of the gamma matrix. This suggests that the conventional Ni-based single-crystal superalloy castings with additional carbon only guarantee the monocrystallinity of the gamma matrix and some gamma/gamma' eutectics and, in addition to the carbides, there are other misoriented polycrystalline microstructures existing in macroscopically considered single-crystal superalloy castings. (C) The Minerals, Metals & Materials Society and ASM International 2017.