Cumulative effects of powder beds and melted areas on pore defects in electron beam powder bed fusion of tungsten

Abstract

In this article, meso-scale simulations and modeling on the multi-layer spreading and melting of tungsten through electron beam powder bed fusion (EB-PBF) were conducted by a three-dimensional discrete element method coupled computational fluid dynamics approach. The recurring pore defects at the edge were explored, and the cooperative effects of spreading/melting parameters on the edge pores were analyzed. On this basis, the mechanism of edge pore formation was revealed, and the occurrence frequency and edge pore size were quantified. Results show that in the multi-layer printing process, the presence of concavities will cause periodic edge pores at the end of the melted area. Increasing melting power and decreasing melting velocity will reduce the occurrence frequency and increase the average size of edge pores, while high spreading velocity and reverse direction can enlarge the total area and average size of the edge pores. The obtained highlighted results are not only of theoretical significance, but also of practical value for parametric setting and optimization in the actual EB-PBF of tungsten.