Detection of sub-superficial defects by infrared thermography in parts made by powder bed fusion with electron beam

The study explores Joule heating infrared thermography as a cost-effective alternative to computed tomography (CT) for detecting subsurface defects in parts produced by powder bed fusion with electron beam (PBF-EB). The primary objective was to quantify how surface roughness typical of different build orientations in PBF-EB affects thermographic data reliability. Simplified intentional defects of various sizes and depths were created in Ti6Al4V custom-samples under various target surfaces, whose morphology was characterized by confocal microscopy. CT scans provided accurate defect dimensions and revealed that sintered powder within defects does not significantly affect thermographic detection and can be treated as voids, paving the way to the application of the method to closed defects. The research led to the development and calibration of a reliable automated thermographic inspection protocol, the definition of best practices and key performance indicators for detectability, and the initiation of defect detectability maps tailored to the distinctive anisotropic features of additively manufactured parts.