NUMERICAL INVESTIGATION OF CMT-WAAM: EFFECTS OF SUBSTRATE PREHEATING ON MOLTEN POOL DYNAMICS AND THERMAL HISTORY

As a Directed Energy Deposition (DED) process, Wire Arc Additive Manufacturing (WAAM) offers high deposition rates and low costs, making it ideal for medium to large metal components. Cold Metal Transfer (CMT) further improves precision by minimizing heat input. However, complex molten pool dynamics in CMT-WAAM can result in irregular bead morphology and discontinuities. This study presents a 3D multiphysics Computational Fluid Dynamics (CFD) model to investigate thermal history, molten pool behavior, and droplet dynamics in the deposition of 17-4 PH stainless steel. The model incorporates the effects of substrate preheating and contact angle variation. The Volume of Fluid (VOF) method was used to track molten pool evolution. Simulation results, validated by experiments, showed that preheating improves pool homogeneity and reduces cooling rates, thereby enhancing deposition stability. Additionally, larger contact angles were found to impair droplet spreading, leading to intermittent bead formation. This work clarifies the interplay between thermal conditions and wetting behavior, offering guidance for optimizing process parameters in WAAM.