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

This study explores infrared thermography as a cost-effective alternative to computed tomography for detecting subsurface defects in parts produced by powder bed fusion with an electron beam (PBF-EB). Ti6Al4V specimens were produced with designed defects that mimic subsurface pores or discontinuities whose size and depth are typical of PBF-EB. Computed tomography (CT-scan) was used to collect information on the defect dimensions and coordinates accurately. The same samples were therefore analysed using Joule heating infrared thermography, applying electric current while an infrared camera recorded the temperature development on the surface of the sample. The joint analysis of CT scan and thermography data provided a comprehensive study on the limits of the inspection technologies, PBF-EB process, and measuring system in terms of defect size, depth, and the size-to-depth ratio. The results showed that the surface characteristics of the PBF-EB are critical for thermography.