In-situ layerwise monitoring of electron beam powder bed fusion using near-infrared imaging

Abstract A near-infrared camera (NIR) is employed to monitor layer-by-layer in-situ electron beam powder bed fusion (E-PBF). We aim at demonstrating that such a device allows various kinds of flaws to be reliably captured thanks to qualitative thermal information. Defects such as distortions or uneven top surfaces can be detected in the NIR-images. Information about temperature heterogeneities can also be linked with some distortions occurring near overhangs. Some lack-of-fusion pores are revealed in the NIR-images. Unexpected localized defects appearing as isolated pores elongated along the building direction, and referred to as chimney pores, are also detected in the NIR-images. Pore-like defects can be described in 3D based on the NIR-images. Post-processing non-destructive characterization performed using X-ray computed tomography (XCT) is carried out to validate the information provided by the NIR-images. Comparisons between the 3D images obtained from the NIR-images acquired in-situ and processed using image analysis, and the 3D images obtained through XCT demonstrate that the morphology and spatial distribution of the defects can be reliably captured by NIR-imaging.