This work introduces an advanced active thermography method that utilizes the distinctive abilities of Synchronized Path Infrared Thermography (SPIT), to provide a novel process monitoring approach in Laser Powder Bed Fusion of Metals (PBF-LB/M). This technique leverages a dual-scanner system, integrating non-destructive thermal excitation via the processing laser, and enhanced defect detection using a high-speed MWIR thermography system. The SPIT system strategically utilises the manufacturing laser to heat the specimen surfaces, thereby enabling the simultaneous capture of thermal behaviour of the surface through a secondary, infrared-optimised optical path. This setup is adept at identifying subsurface defects, which is crucial for assessing the integrity of components produced via additive manufacturing and that traditional surface inspection methods might miss.

In this technology, the resulting temperature fluctuations caused by locally differing thermal material properties are measured. These differences can be caused by a variety of manufacturing imperfections and result in a decreased heat dissipation, which can be reflected in measurably higher temperatures on the surface of the part.

The presented measurement and evaluation methods demonstrate the efficacy of detecting artificially introduced defects in additively manufactured samples of 1.4540 stainless steel. The examined defects exhibit a diameter range of 0.35 mm to 1 mm, with the capacity to identify them to a depth of 200 µm below the surface of the specimens. The results show the capabilities of the SPIT setup in non-destructive testing and its ability to deliver accurate and reliable detection of defects.