<b>Flat-top laser powder bed fusion of non-weldable Ni-based superalloy: crack mitigation through microstructural engineering for enhanced mechanical properties</b>

Here, a flat top (FT) laser beam was used to fabricate Inconel 939, and its cracking behavior, microstructure, and tensile properties were compared with those produced by a Gaussian beam. At 850 W and 350 mm/s, FT-LPBF produced specimens with 99.95% relative density and no cracks detected in the examined sections.

Compared with the Gaussian conditions, FT processing generated flatter melt pools, continuous columnar grains, and a lower fraction of high-angle grain boundaries. The as-built FT specimen achieved an ultimate tensile strength (UTS) of 1211 MPa and elongation of 18.8% at room temperature. From 800 to 1000℃, Its UTS decreased from 983 to 284 MPa, while elongation increased from 18.4% to 29.4%.