Electron beam powder bed fusion process monitoring by in-melt electron analysis

Effective process monitoring is crucial for ensuring high print quality in electron beam powder bed fusion (PBF-EB), an advanced additive manufacturing technique. The interaction of electrons and matter provides a wealth of in-melt information during repeated local melting. To utilize the emitted electron signal efficiently, this study develops an in-melt electron analysis (IMEA) approach by analyzing and interpreting emissions, primarily composed of backscattered, secondary, and thermionic electrons. Owing to the high correlation of thermionic electrons to the temperature and area of the hottest spot, the melt pool characteristics can be monitored from the signal of emitted electrons. Two types of melting were conducted: (1) single tracks on a bare plate without powder and (2) printing on a powder bed. We demonstrate that the intensity of measured in-melt electrons correlated with the melt pool width on bare plate of 316 L stainless steel. In addition, we also demonstrate the applications of IMEA approach to detect the melt pool dynamics such as melt pool surface depression during a real print of 80 layers on 316 L stainless steel powder bed. This approach provides reliable monitoring of melt pool characteristics and surface depression, offering a promising tool for process control in PBF-EB.