Thermal-Fluid Behaviors and Morphology Evolution of Molten Pool During Selective Laser Sintering of Inconel 625

Abstract

Abstract A two-dimensional multi-physics finite element model of the Selective laser sintering (SLS) process on Inconel 625 powders is developed. The model is validated through comparison with experimental data previously published in the literature. Thermal/fluid behaviors and morphological evolution of the molten pool are studied, considering phase transition, recoil pressure, surface tension, and the Marangoni force. The simulation outcomes exhibit the time-varying temperature distribution, fluid dynamics, and surface morphology during the SLS process under different conditions, which helps to identify the impacts of process parameters on the SLS process. The results demonstrate that during the SLS process, the morphology and thermal-fluid dynamics of the molten pool are primarily influenced by the Marangoni force and recoil pressure acting on its surface. Specifically, the recoil pressure at the leading edge of the laser spot plays a crucial role in determining the molten pool’s behavior. The recoil pressure increases exponentially as the temperature rises, causing the liquid metal to move downward and form a depression area at the head of the molten pool, and generates particles that are splashed from the rear edge of the molten pool. The backward Marangoni force, which causes high-temperature liquid at the head of the molten pool to flow towards the cooler liquid at the rear, results in the formation of a vortex that moves the molten pool in the rear region. This study analyzes process parameters such as laser intensity, scan speed, and spot size. The results indicate that increasing laser power and decreasing scanning speed and laser beam spot size can lead to an expansion in both the depth and width of the molten pool.