Effects of electromagnetic compound field on the macroscopic morphology of laser cladding

Abstract

To enhance the controllability of the molten pool morphology, a directional Lorentz force is produced within the molten pool by synchronously coupling a steady electric field and magnetic field during the laser cladding process. A 2D numerical model of the molten pool considering solid–liquid phase change, heat transfer, fluid flow, deformed geometry and electromagnetic induction is established. The experimental and simulation results demonstrate that the magnetic or electrostatic field has negligible effects on the molten pool shape. The compound electromagnetic field (simply as a compound field) that generates a downward Lorentz force significantly impacts the molten pool height, and wetting angle. As revealed by the observation of the molten pool forming process, it is found that the downward Lorentz force disrupts the force balance of the molten pool, which leads to the outward expansion of the fluid due to an increased pressure difference. As a consequence, the height of the molten pool decreases. Meanwhile, the employment of a magnetic field results in a significant increase in the viscous resistance at the solidification interface. The fluid is accumulated at the bottom of the molten pool, which increases the wetting angle. Additionally, since this approach can produce a steady volume force similar to gravity, it can be used in a weightless environment, such as in a space station, thus significantly improving the process stability.