Heat input regulation for geometric and property control in directed energy deposition with dense scan path strategy

A fundamental challenge in manufacturing high-performance components using directed energy deposition (DED) is the effective management of heat accumulation when processing complex geometries with a high infill density zigzag scanning strategy. This study reveals an inherent conflict between local and global thermal effects that unresolved by constant power strategies: high power intensifies local melt pool instability at path turning points, whereas low power causes more severe global heat accumulation and sacrifices forming accuracy due to an increased layer count. The study establishes a dual heat-affected zone (HAZ) gradient evolution model at the DED-HIP interface, and reveals the embrittlement risk of the dissolution heat-affected zone (D-HAZ) under high heat input and the softening mechanism of the over-aged HAZ (OA-HAZ). Therefore, this study proposes a power closed-loop control (PCLC) strategy based on real-time melt pool width monitoring to achieve active thermal management. It is revealed that the PCLC technology, by precisely suppressing local overheating in the zigzag scanning path, achieves a synergistic optimization of morphology, accuracy, and microstructure, with significantly enhanced mechanical properties (elongation reached 21.15 %, and tensile strength reached 1189 MPa, achieving 95.8 % that of the substrate). This research provides crucial theoretical guidance and technical support for the additive manufacturing of high-performance components requiring customized microstructures and precise geometric control, such as aero-engine integral blisks.