Modeling electrostatic field development in electron beam powder bed fusion

Powder bed fusion with electron beam (PBF-EB) emerges as a promising metal additive manufacturing (AM) technology for industrial applications. This technique employs a layer-by-layer fabrication approach, enabling the creation of intricate geometries directly from metal powder beds. Traditionally, a process efficiency of 90% has been assumed. However, recent discoveries highlight that the efficiency in PBF-EB is significantly influenced by various process characteristics. A key characteristic is the development of the electrostatic field within the process, which is created by the charging of the powder substrate by electrons. This leads to a critical transient phenomenon known as the ‘smoking effect’. The impact of this effect has not yet been thoroughly investigated in prior studies. This research focuses on the influence of powder charging and the resulting electrostatic field as a major contributing factor to EBM process efficiency. COMSOL Multiphysics simulations were utilized to approximate the developing electrostatic field within the PBF-EB process. Additionally, Monte Carlo-EGS5 simulations were employed to gain a comprehensive understanding of how this field impacts the process dynamics. The simulations revealed two key findings: The electrostatic field within the PBF-EB process is significantly larger than previously reported values, and the field exhibits variations based on various factors. Furthermore, the research demonstrates that the electrostatic force dominates the forces acting on individual powder grains, ultimately influencing the observed “smoking effect.” This work underscores the critical role of the electrostatic field in PBF-EB. For clarification, throughout this paper, the term “grain” refers to powder grains (particles), while the term “particle” refers to nuclear particles such as electrons.