In-situ monitoring of the material composition in PBF-LB via optical emission spectroscopy

Powder bed fusion using a laser beam of metals (PBF-LB/M) is a widely used additive manufacturing (AM) technique that enables the material-efficient fabrication of complex geometries in metallic parts. However, achieving high-quality parts with desired properties heavily depends on variances in the manufacturing process and powder composition, making quality control an indispensable aspect of almost all applications. Today, mainly grayscale imaging or pyrometry are employed, whereas in situ recording of chemical (compositional) information has rarely been done during LBF-LB/M. This pilot study explores the feasibility of in-situ optical emission spectroscopy (OES) for elemental analysis of metallic samples during PBF-LB, at the example of Nd-Fe-B. Our findings suggest that the local emissivity of Fe and Nd lines can serve as a reliable indicator to determine the temperature and elemental concentration in the plasma. The results showed that Online-OES during PBF-LB enables tracking of how Nd content in as-build parts critically depends on the laser parameter used while printing the part.