In-depth analysis of CT resolution impact on porosity evaluation in laser powder bed fusion additive manufacturing

Accurate porosity determination of Additive Manufacturing (AM) parts remains a key challenge. This study provides an in-depth analysis of how computed tomography (CT) resolution affects porosity detection in Laser Powder Bed Fusion (LPBF) manufactured parts by comparing X-ray based measurements from laboratory and synchrotron sources. To represent a range of porosity levels, three samples were selected from an extensive set of LPBF experiments, of respectively low, medium, and high porosities. A laboratory source based computed tomography system was used for the acquisition at the best resolution considering the size limitation due to the sample geometry. In order to achieve higher resolution, a synchrotron source was additionally utilized. The comparative analysis revealed that the porosity measurements from both the laboratory and synchrotron sources were in good agreement for samples with low and high porosity levels. This indicates that for extreme ends of the studied porosity spectrum, laboratory CT systems can provide reliable measurements. However, for the sample with medium porosity, the limited resolution of the laboratory CT leads to an overestimation compared to the synchrotron CT results. This discrepancy is found to be due to inaccuracies in detecting and clustering neighboring pores, leading to an overestimation of porosity. A comparison of the obtained results with the porosity determinations by the widely used Archimedes method is proposed to show the potential and the limitations of each technique for the assessment of additively manufactured parts.