Elucidating sequential laser remelting in tailoring microstructure and mechanical performance of laser-directed energy deposited Hastelloy-X

The current manuscript undertakes a systematic analysis of sequential layer-by-layer laser remelting (SLLR) within the context of laser-directed energy deposition (LDED) of Hastelloy-X (HX) bulk structures. Comparative analysis is conducted between the surface and bulk properties of LDED-built samples and those incorporating SLLR. Integrating SLLR with LDED results in a notable decrease in surface roughness by 71.5% and porosity by eight times. While both lack of fusion and gas porosity are evident in the as-built sample, the combination of SLLR with LDED shows only gas porosity. Moreover, microstructural refinement is observed after SLLR without preferential growth along (100), unlike in samples without SLLR. Analysis reveals segregations of Mo, Si, and C and the presence of Mo-rich carbides in both LDED and SLLR samples. The finer dendritic microstructures observed in SLLR samples contribute to a 12% increase in microhardness and a 7% rise in yield strength along the build direction compared to samples without SLLR. This study lays the path for fabricating dense components with tailored microstructures and mechanical properties during LDED through the utilisation of SLLR.