In-situ composition analysis during laser powder bed fusion of Nd-Fe-based feedstock using machine-integrated optical emission spectroscopy

Abstract

Powder bed fusion of metals using a laser beam (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, photodiodes, or pyrometry are employed, whereas in-situ recording of chemical (compositional) information has rarely been done during PBF-LB/M. This pilot study uses Nd-Fe-B as a compositional sensitive model material to explore the feasibility of in-situ optical emission spectroscopy (OES) for elemental analysis of metallic samples during PBF-LB/M, validated by ex-situ analysis. Our results show that the Boltzmann-corrected local emissivity of the Fe and Nd lines in the plume is a reliable indicator for determining the temperature and elemental material concentration voxel-wise, which could enable a digital 3-D reconstruction of the material composition of a printed part in the future.

Keywords

• In-situ spectroscopy
• In-situ monitoring
• Optical emissivity
• Selective laser melting
• Permanent magnets