Electromagnetic Field-Assisted Laser Process

Abstract

During the fabrication of ceramic–metal composite coatings via laser melt injection (LMI), an issue with ceramic particle distribution within the metal matrix is often encountered. Traditionally, the successful manufacture of a coating with the desired particle distribution relies on the use of a specially designed lateral nozzle acting as a powder delivery nozzle to avoid the excessive dissolution of the reinforcement particles, thereby optimizing process parameters to achieve the required product specification. However, the practical implementation of this approach has difficulties and is also time-consuming, as the adjustable window for the lateral nozzle powder delivery system is very narrow. A novel approach to control the laser process was proposed recently, which couples an electromagnetic field to the laser system, thus assisting the laser melting process resulting in a controlled particle distribution gradient of the composite coating, as well as in controlled porosity of the coating layer. The impact of applying an electromagnetic compound field to a laser process on the produced coating is studied experimentally and numerically. In the numerical simulation, a 2D multi-physics model is created for the laser melt process coupled with the equations of heat transfer, fluid dynamics, drag force, the Lorentz force and phase transition, which incorporate the effects of the electromagnetic compound field. Experimental and simulation results obtained are in good agreement, both showing that the directional Lorentz force created by the electromagnetic compound field can change the equivalent buoyancy acting on the ceramic particles as a type of volume force, thus controlling their distribution gradient. Furthermore, with an electromagnetic compound field applied, the escape state of pores in the molten pool can be controlled effectively. With the downward Lorentz force acting, dense cladding layers with minimum porosity can be achieved successfully.