Comparison of post-process X-ray computed tomography and in-process optical measurements for defects evaluation in additively manufactured parts

Despite the capability of fabricating complex and customized components, metal laser powder bed fusion (LPBF) is still affected by manufacturing issues, which can lead to significant geometrical and dimensional errors and internal defects. These aspects can represent a major barrier to a wider industrial application of LPBF, particularly if considering that relevant applications of additive manufacturing are in sectors such as biomedical and aerospace, which have stringent requirements in terms of defects and product quality. The requests for precision improvement are orienting research activities towards the development of in-process monitoring systems able to perform accurate analyses during the fabrication itself, hence providing useful information for improving the quality of produced parts. To this aim, several in-process monitoring methods have been proposed in the literature to identify and correct out-of-control process conditions. In spite of the aforementioned research efforts, work is still needed to reliably correlate in-process measurements to actual defects. The focus of this experimental study is the definition of a robust methodology to compare in-process optical acquisitions to post-process X-ray computed tomography (XCT) measurements of actual defects. XCT unique capabilities are therefore exploited to support and improve the LPBF process through the implementation of an accurate comparison methodology.