Effect of the magnetic field generated by coil on metal transfer behavior in wire-laser directed energy deposition

Wire-Laser Directed Energy Deposition (W-LDED) offers high deposition rates and efficient material utilization but is limited by unstable metal transfer, spatter formation, and excessive dilution, which reduce process robustness and deposit quality. This work investigates the influence of an electromagnetic field (EMF), generated by a custom-designed coil, on metal transfer dynamics and bead morphology in W-LDED. High-speed imaging at 1000 fps was employed to capture transient droplet melt pool interactions, while cross-sectional macrographs were analyzed to quantify bead geometry and dilution. The application of EMF stabilized the liquid-bridge transfer, reduced rupture frequency and spatter, and improved robustness under wire misalignment by redirecting droplets toward the melt pool. Quantitative analysis showed that EMF increased bead height from 0.81 to 0.97 mm, bead width from 2.50 to 2.60 mm, and cross-sectional area from 1.52 to 1.84 mm ² , while reducing dilution from 41.98% to 26.69%. These effects are attributed to Lorentz forces arising from the interaction between the applied magnetic field and electrically induced currents in the molten metal, which damp Marangoni-driven convection and promote a more uniform thermal distribution. The results demonstrate that electromagnetic assistance is a practical strategy to enhance metal transfer stability, bead quality, and process reliability in W-LDED.