Effects of Microstructure Anisotropy on Dynamic Fracture Behaviors of a Selective Laser Melting Nickel-Based Superalloy

Abstract

In the study, the microstructure and defect of the Ni-based GH3536 manufactured by SLM were characterized by SEM, TEM, EBSD and μ-CT. The characteristic fracture behaviors corresponding to crack initiation and propagation are quantified by the absorbed impact energy and the dynamic crack resistance curves. It is found that the fabricated alloy exhibited slightly lower strength but much higher dynamic fracture toughness along the building direction, compared to those along transverse directions and the hot-rolled counterpart. Furthermore, the correlation between microstructure anisotropy and dynamic fracture behaviors are explored and discussed through the KAM, fractography and crack trajectories analyses. It is concluded that the anisotropy related to dynamic fracture mechanism of GH3536 alloy manufactured by SLM can be attributed to the ‘weakest link’ interface due to the laser melted pool geometry, the grain boundary or dendrite, which is dependent on the relative orientation difference between the building direction and the crack plane.

Keywords: Selective laser melting, Nickel-based superalloy, Microstructure anisotropy, Dynamic fracture toughness