Synergistic Effects of Carbon/Nitrogen Content and Laser Powder Bed Fusion Parameters on the Hot Cracking Behavior and Microstructural Evolution of a Ni–Co‐Based Superalloy

The broad industrial adoption of additively manufactured superalloys is severely hindered by hot cracking. This research utilizes laser powder bed fusion (LPBF) to provide a systematic elucidation of how carbon and nitrogen concentrations interact with processing conditions to govern the microstructural development and crack initiation mechanisms within a Ni–Co‐based superalloy. With increasing carbon and nitrogen content, the areal fraction of intergranular carbides increases markedly. Meanwhile, the carbides decorating grain boundaries transition from discrete particles to quasi‐continuous and ultimately continuous networks, accompanied by enhanced nitride precipitation. These hard and brittle phases refine the cellular solidification structure but substantially increase the proportion of high‐angle grain boundaries (HAGBs). Their pronounced pinning effect hinders liquid feeding during the terminal stage of solidification, thereby creating preferential crack‐initiation sites and accelerating intergranular crack propagation. Furthermore, increasing the energy density and laser power significantly heightens crack susceptibility by modifying molten‐pool thermodynamics and intensifying thermal stress gradients, whereas an appropriately optimized processing window effectively suppresses crack formation. Overall, this study establishes mechanistic and quantitative linkages among alloy chemistry, LPBF‐induced microstructural features, and hot‐cracking behavior, thereby providing a rigorous scientific foundation for the composition design and process optimization of LPBF‐fabricated superalloys.