High-throughput laser powder bed fusion with carbon gradient engineering enables a crack-resistant GH3230 superalloy with superior mechanical properties

Cracking defects are a major obstacle in the laser powder bed fusion (LPBF) of Ni-based superalloys, whereas most current efforts in eliminating cracks also lead to a compromise in mechanical performance. Carbon, a key trace element in superalloys, plays a crucial role in resolving this dilemma, yet its optimal content and associated solidification mechanisms remain unclear. In this study, a carbon-compositionally graded design combined with an LPBF high-throughput screening strategy was employed to systematically and rapidly investigate the effects of carbon content on the crack susceptibility, microstructural evolution, and mechanical properties of GH3230. The results reveal a strong dependence of cracking on the carbon fraction. Crack density firstly increases and then reaches a maximum at ~0.07 wt% C but is completely eliminated when the carbon fraction exceeds 0.25 wt%. Although increasing carbon widens the solidification range, carbon enrichment in the terminal liquid promotes carbide precipitation along grain and cellular boundaries. M₂₃C₆ carbides evolve from discrete particles into continuous or semi-continuous networks, which effectively modify the morphology and continuity of intergranular liquid films and enhance grain boundary cohesion, thereby suppressing crack formation. The optimized composition (0.25 wt% C) achieves a yield strength of ~749 MPa, ultimate tensile strength of ~1 001 MPa, and elongation of ~13% at room temperature while maintaining a yield strength above 200 MPa at 1 000 °C. This study demonstrates that a high-throughput LPBF carbon gradient method can screen a wide crack-free processing window (0.25−0.6 wt% C) and enable crack-resistant Ni-based superalloys with superior performance.