High-fidelity optical monitoring of laser powder bed fusion via aperture division multiplexing

Abstract

Qualification of high-performance metal components produced by laser powder bed fusion (LPBF) must identify porous defects that nucleate fatigue cracking. Detecting such defects via optical monitoring of LPBF can enable in-process quality control without downstream testing. However, integration of in-process sensing with LPBF is hampered by optical complications, and therefore, it has yet to be proven that the finest pores that limit component fatigue life can be resolved. We present aperture division multiplexing (ADM) as a method for simultaneously focusing the process laser and providing unobstructed optical access for high-fidelity process monitoring using a common optic. Construction of an ADM optic with 50 μm spatial resolution in the mid-wave infrared is described, and it is demonstrated on a production-representative LPBF testbed. High-speed video data are correlated to micro-CT measurement of pores as fine as 4.3 μm, establishing the promise of ADM for the qualification of LPBF component fatigue performance.