Manipulating intrinsic eutectic for hot cracking suppression and synchronous strengthening via segregation engineering in an additively manufactured superalloy

Hot cracking remains a critical challenge limiting the widespread adoption of superalloys in additive manufacturing. This defect primarily originates from stress-induced rupture of intergranular residual liquid films that persist during final solidification, typically comprising low-melting-point phases formed through solute-segregation. This understanding has guided conventional crack suppression strategies focused on eliminating such residual phases by strict compositional controls. Herein, an innovative approach is demonstrated that strategically engineers residual eutectic fractions (≥2 vol.%) through trace element regulation to achieve an intrinsic capability for crack suppression. Hastelloy X is selected as the model system owing to its marked hot cracking susceptibility. Leveraging the ultra-low partition coefficient ( k = 0.21) of carbon, a subtle increment in its content (<0.1 wt.%) significantly enhances the formation of ternary eutectic carbides through amplified segregation. The resulting adequate eutectic liquids successfully prevent crack initiation through stress-compensating backfilling while preserving structural cohesion via liquid buffering, revealing the context-dependent duality of eutectics—transitioning from crack initiators to healers. These crack-free samples exhibit superior strength–ductility synergy compared to carbon-restricted counterparts, benefiting from combined effects of carbide dispersion strengthening and multiple dynamic hardening mechanisms.