NUMERICAL STUDIES OF EXTREME HIGH-SPEED LASER MATERIAL DEPOSITION PROCESSES AT POWDER-SCALE

We present a meshfree Direct Numerical Simulation (DNS) for a Laser Material Deposition technology referred to as Extreme High-speed Laser Material Deposition (EHLA) process at the powder scale based on the novel Hot Optimal Transportation Meshfree (HOTM) method. The HOTM method is a High Performance Computing-based incremental Lagrangian meshfree solver for strongly coupled Thermal Fluid-Structure Interaction problems, possibly involving extremely large deformations, dynamic phase transition and multiphase mixing. It combines the Optimal Transportation Meshfree (OTM) method and the variational thermomechanical constitutive update. In the HOTM simulations, the powder particles are modeled explicitly using the size distribution measured in experiments and discretized by nodes and material points. The governing equations, including the linear momentum and energy conservation equations, are solved simultaneously in the meshfree framework to predict the deformation, temperature and local state of the powder particles. A full-field constitutive model is developed to model the multiphase flow with melting and solidification. The Lagrangian nature of the HOTM method overcomes various challenges in the DNS of the melt pool thermodynamics during EHLA processes. The proposed approach is employed to quantify the influence of the main processing parameters, such as laser power, laser radius, deposition speed, powder mass flow and axial feed, on the layer thickness, surface roughness and porosity of the bonding zone. It further enables an in-depth understanding of the quality control in the EHLA coating technique.