Research on the coupled characteristics of multi-physics fields in direct energy deposition melt pool considering powder effect

Direct Energy Deposition (DED) is an additive manufacturing process that entails complex energy and material transformations. The rapid transport of heat and material within the melt pool plays a critical role in shaping the solidification morphology of the deposited layer. This paper develops a multi-physics numerical model for DED process, which integrates the Smoothed Particle Hydrodynamics (SPH) with the Discrete Element Method (DEM) and incorporates a powder-laser attenuation model. In the experiment, the residence time of the powder on the surface of the molten pool is influenced by temperature and the location of its entry, resulting in behaviors such as integration, floating, or adhesion. Moreover, the residence time increases with the distance from the laser zone. When powders in different states (single molten, agglomerated molten and unmolten) fall into the molten pool, the randomly added kinetic energy and heat disturb the existing Marangoni flow, triggering oscillations of varying intensities within the molten pool. Among these, fully molten powder exerts the least influence on the pool. Increasing the laser power or decreasing the powder velocity leads to higher powder deposition temperatures. The path of the powder from the laser center to the edge is particularly sensitive to variations in the parameters. This study provides a more comprehensive analysis of the interactions between the powder and the molten pool, thereby enhancing the accuracy of molten pool flow modeling.