PIHT heat input regulation for synergistic control of manufacturing quality and mechanical properties in DED-Arc 304 stainless steel

Abstract

Directed Energy Deposition-Arc (DED-Arc) is promising for large-scale metal component manufacturing due to its high efficiency and low cost, but residual stress and deformation from layer-by-layer deposition limit its application. To address the “synergistic control of forming quality and performance,” this study introduces Plasma In-situ Heat Treatment (PIHT) as a synchronous thermal regulation strategy, aiming to explore how PIHT heat input affects the forming quality of DED-Arc-fabricated 304 stainless steel components. A 3D transient thermo-mechanical coupled finite element model (with double ellipsoid plasma heat source) was integrated with experiments (VIC-3D full-field strain measurement and infrared thermal imager) to systematically analyze the effects of PIHT heat input (0.384–0.768 kJ/mm) on temperature field, stress-strain field, mechanical properties, and microstructure. Results show PIHT effectively regulates the welding thermal cycle and improves temperature field uniformity, while excessive heat input causes heat accumulation. The heat input exhibits a non-linear relationship with substrate deformation and residual stress, with an optimal window identified. At 0.672 kJ/mm, longitudinal and transverse equivalent stresses are reduced by  ~57%, residual tensile stresses by ~66% and 52% respectively, and substrate deformation reaches the minimum (1.17 mm). This optimal parameter achieves the best comprehensive mechanical properties (tensile strength = 577/623 MPa, elongation = 16%/17%, microhardness = 225 HV) with uniform distribution. Microstructural analysis indicates PIHT balances grain refinement and second-phase precipitation, avoiding excessive fineness or coarseness defects.