Liquid-induced healing of cracks in nickel-based superalloy fabricated by laser powder bed fusion

Despite being recognized as a disruptive technology, laser powder bed fusion additive manufacturing has not yet achieved the widespread commercial application envisioned in its early stage. One of the most critical challenges is the cracking issue that limits the printability of most existing engineering alloys. Here we report a liquidinduced healing (LIH) post-process that enables complete healing of those microcracks by inducing the solidliquid phase transition at the cracking regions, resulting in enhanced mechanical properties. Specifically, we adopted In738LC alloy prepared by laser powder bed fusion as the demonstration material to reveal the mechanisms of remelted liquid fraction and isostatic pressure during the crack healing processing. The effects of LIH treatment on mechanical properties and microstructural evolution were also investigated. Compared with the existing solutions for crack elimination (e.g., shortening the solidification range, promoting equiaxed grains, reducing thermal stress, and hot isostatic pressing), our strategy exhibits superiorities in terms of crack healing efficacy, operation complexity, and process cost. LIH shows promise as a routinized and guaranteed process integrated with additive manufacturing, bypassing the technical barriers to completely crack-free printing and thus immediately promoting the industrial application of the alloys hindered by the cracking issue.