Spatiotemporal characterization of evaporated atoms during electron beam melting additive manufacturing by advanced laser diagnostics

Electron powder bed fusion (E-PBF) is an additive manufacturing technology used to produce parts layer-wise for advanced aerospace, biomedical, and other applications. Precise control over the energy transferred to the powder by the electron beam is key to further process improvements. Here, we used tunable diode laser absorption spectroscopy to characterize the evaporated titanium atoms above the molten area of a TA6V powder alloy, and, thus, the effects of the energy transferred to it by the electron beam. This unconventional diagnostic tool achieves analyses at very high temporal (<1 μs) and spatial (<100 μm) resolutions, thus, offering valuable information on the microsecond-scale dynamics of the micro-melting zone and the effectiveness of the electron beam spot at diameters as small as ∼200 μm. Our measurements highlighted sharp fluctuations during the evaporation process that were independent of the power and scan speed of the electron beam; instead, the molten pool surface itself seems to drive these fluctuations. Our analysis also documented the shape and density of the vapor plume, which was oriented perpendicular to the surface under common E-PBF conditions.