Comprehensive modeling of transport phenomena in laser hot-wire deposition process

摘要

Transport phenomena in the molten pool and heat affected zone during the laser hot-wire deposition process are intrinsically complex. These phenomena involve multi-phase flows on the millimeter scale, including surface tension and capillary effects at the gas–liquid interface, solid–liquid phase transition, heat input from the laser beam source, and mass addition from the filler wire. Thus, a comprehensive multi-phase model was proposed in this study, which elucidates the evolution of the gas–liquid–solid interfaces during the laser hot-wire deposition process. A coupled level-set and volume-of-fluid approach was adopted to track the motion of the free surface with high resolution while ensuring that mass conservation was not violated. The mass addition from the preheated filler wire was modeled as the source terms in the continuity and energy equations. The simulation results include the geometries of the molten pool and clad layer, Marangoni outward flow effect and temperature evolution during the deposition. The multi-phase model was validated based on the geometries of the fusion zone and clad layer determined from laser conduction welding and laser hot-wire deposition experiments. The mechanism of cladding formation (specifically the microstructural and microhardness gradients in the deposited FV520B maraging steel) was analyzed based on the temperature profile of various phase transition regions in the heat affected zone.