Optimized processing parameters for crack-free fabrication of unweldable Inconel 738LC via directed energy deposition

This study establishes a comprehensive processing window (PW) for the directed energy deposition (DED) of Inconel 738LC (IN738LC), a γ’-precipitation-strengthened superalloy traditionally considered unweldable due to its high crack susceptibility. To address this challenge, we focus on minimizing heat input as the key strategy to suppress cracking and enhance microstructural quality. Through a systematic investigation of thermal conditions and their influence on microstructural evolution, we developed an optimized PW characterized by low heat input, achieved through lower laser power and optimized scanning parameters. This approach effectively minimized elemental segregation, reduced the size of the heat-affected zone, and promoted favorable microstructural features, including equiaxed grain structures. The PW was validated by successfully fabricating crack-free high-density (>99.5%) components, including a prototype turbine blade. These findings confirm that reducing heat input through optimized processing parameters is a highly effective strategy for the crack-free fabrication of γ’-precipitation-strengthened superalloys, enabling novel possibilities in the additive manufacturing of high-performance components.