Process–Structure–Property Mapping of Inconel 625 Processed by Laser Beam Directed Energy Deposition (DED-LB)

Laser beam directed energy deposition (DED-LB) of Inconel 625 (IN625) is an attractive route for near net shape manufacturing and repair of high-value components. However, robust processing windows linking process parameters, defect formation, and mechanical response remain insufficiently established. In this work, a comprehensive process–structure–property map for powder-fed DED-LB IN625 is developed through an experimental program that includes single-bead geometric parameterization and direct multi-layer upscaling to bulk blocks. Laser power, scan speed, powder feed rate, hatch overlap, and layer height were systematically varied, and bead geometry, dilution, deposition efficiency, and energy density were used to identify suitable conditions for bulk fabrication. Under the optimal parameters, the material exhibited nearly full density with minimal defects and a refined dendritic microstructure characterized by Nb/Mo microsegregation and the formation of Laves and carbide phases. These microstructural features, combined with the reduction of lack-of-fusion defects, resulted in tensile strengths exceeding those of wrought IN625, while maintaining elongation values appropriate for structural applications, though lower than the wrought counterpart. Analysis of the parameter space demonstrates that volumetric energy density alone is insufficient to control porosity; instead, coordinated adjustment of hatch spacing and layer height with laser power and scan speed is required to suppress both lack-of-fusion and keyhole-related defects. The proposed map provides quantitative guidance for selecting robust DED-LB processing windows for the fabrication and repair of IN625 components with tailored microstructure and mechanical performance.