Multiphysics modeling of melt pool dynamics and powder bed stability in LPBF of inconel 718 for a circular cavity

Abstract Laser powder bed fusion (LPBF) is a metal additive manufacturing process in which a concentrated laser beam selectively melts successive powder layers to fabricate components. Final part quality is highly sensitive to process parameters such as hatch spacing, powder bed density, laser power, and scanning speed. In this study, a computational fluid dynamics model employing discrete element method has been developed in FLOW-3D to simulate LPBF of Inconel 718. The modeled powder bed incorporates particle size distribution data obtained from scanning electron microscopy and is evaluated for single-layer, single-track deposition over a circular cavity. The model captured melt pool dynamics in terms of width and depth, spattering, and Marangoni convection. Results showed that spattering was limited and melt pool behavior was predominated by the coupled effects of recoil pressure and Marangoni convection. Recoil pressure is identified as a contributing factor to melt pool instabilities associated with spattering behavior, while Marangoni convection influenced melt pool shape and stability. The effect of airflow at various velocities (8–48 cm/s) and exposure times on powder bed stability were also analyzed, revealing that airflow significantly disturbed finer particles at moderate to high velocities. Similarly, low chamber pressures (0.99–0.97 atm) were found to enhance gas velocities and powder displacement over the powder bed.