Enhancing microstructure and mechanical properties of Inconel 625 by a low-cost static magnetic field-assisted WAAM process

Abstract

Wire arc additive manufacturing of nickel-based superalloys often suffers from limited deposition stability, microstructural inhomogeneity, and mechanical anisotropy, which restrict its broader industrial application. This study aims to evaluate the feasibility of using a static magnetic field as a low-cost, passive, and energy-free process control strategy for WAAM-fabricated Inconel 625. A GMAW-based WAAM system was employed under different transverse static magnetic field conditions, and the resulting build geometry, microstructural characteristics, and mechanical properties were systematically investigated. The results show that an appropriate magnetic field intensity increased the build height by 15.3% while improving surface morphology and deposition stability. Microstructural observations revealed noticeable changes in solidification morphology and improved microstructural uniformity. Elemental analysis indicated a significant reduction in Nb and Mo segregation, while XRD peak broadening suggested refined microstructural features and partial residual stress release. The average microhardness increased by approximately 6–7% with a more uniform distribution. The ultimate tensile strength increased from 729/660 MPa (horizontal/vertical) to 775/692 MPa, corresponding to improvements of 6.3% and 4.8%, respectively, accompanied by more uniformly distributed ductile fracture features. Overall, the results demonstrate that static magnetic field assistance can effectively enhance molten pool convection, improve microstructural homogeneity, and enhance mechanical performance in WAAM-fabricated Inconel 625, highlighting its potential as a simple and industrially applicable process control approach.