Effects of near immersion active cooling on microstructure control in wire arc additive manufacturing of IN718: multiscale modeling and experiments

A multiscale numerical model, integrating the macroscopic finite element model and the microscopic cellular automaton model, is developed to simulate temperature field distribution and solidification microstructure of IN718 nickel-based superalloy during wire arc additive manufacturing (WAAM). Heat accumulation is shown to be intensified by geometric curvature, particularly in corner regions, and increases with layer number. By mapping macroscopic thermal field data into a two-dimensional quantitative cellular automaton model via multidimensional interpolation, the solidification and melting of microstructures are simulated. Simulated results agree well with experiments, confirming that the coarsest dendrites form in middle regions. A near immersion active cooling (NIAC) strategy is developed for the refinement of solidification microstructure. The application of the NIAC technique effectively enhances the heat dissipation and accelerates the cooling rates about 3.5 times, which thus suppresses thermal accumulation. In addition, NIAC significantly refines the primary dendrite arm spacing from 14.3-19.5 μm to 12.5-13.5 μm and reduces the volume fraction of Laves phase from 0.9%-1.7% to 0.6-1.1%. This study provides insights into the thermal–microstructural coupling in WAAM and demonstrates NIAC as an effective approach for microstructure control in WAAM of complex components.