Molten pool flow behavior and influencing factors in electron beam selective melting of IN738 superalloy

Abstract

Electron beam selective melting (EBSM) has emerged as a promising technology for additive manufacturing (AM) of superalloys. In this study, a comprehensive multi-physics model is developed to analyze the molten pool flow behavior and influencing factors in the EBSM process. The discrete element method (DEM) and volume of fluid (VOF) method are employed to establish the powder bed model and track the solid-liquid free surface, respectively. The results reveal that the molten pool exhibits a conduction mode characterized by a large width-to-depth ratio driven by the Marangoni effect. Internal vortices cause the molten pool to expand even after the scan ends. The ambient pressure, in comparison to the preheat temperature, has a significant impact on vapor recoil and consequently affects the surface quality of the molten pool. Moreover, a large hatch distance results in cracks and porous morphological features on the surface of the samples. These findings demonstrate the effectiveness of numerical simulations in providing detailed insights into the EBSM process of the IN738 superalloy material.