Effect of solidification rate on MC-type carbide morphology in single crystal Ni-base superalloy AM3

Abstract

In order to study the effect of the withdrawing rate on carbide morphology, MC-type carbide in single crystal superalloy AM3 was systematically investigated with sample growth rates from 3.5 μm/s to 500 μm/s. The carbide morphologies were investigated by scanning electron microscopy (SEM), and the electron probe microanalysis (EPMA) was used to characterize the carbide composition. The results indicate that the solidification rate is the important factor governing MC carbide growth morphology, size and distribution, composition and growth mechanism. With the increase of withdrawing rate, nodular, rod-like, Chinese script types of carbide morphology are observed. For the low withdrawing rate, with the increase of withdrawing rate, the carbide size becomes larger. For the case of dendritic interface, the carbide size becomes smaller with refinement of dendrites as withdrawing rate increases. The volume fraction of carbides increases with the withdrawing rate increasing.