Defect characteristics and analysis of their variability in metal L-PBF additive manufacturing

Additive manufacturing (AM) has provided an opportunity for fabricating complex parts. Fabricating these parts without defects is currently a challenge. Therefore, understanding AM defects is fundamental to the structural integrity of load carrying components, failure analysis, and defect-based modeling of mechanical performance. This work investigates defect content of metal AM specimens and correlations between defect characteristics (size, sphericity/circularity, aspect ratio) using 2D and 3D defect characterization techniques. Distributions of defect characteristics based on location throughout AM specimens were analyzed and the variabilities of defect characteristics within these specimens were studied. Laser-Based Power Bed Fusion (L-PBF) specimens manufactured with different metals, different AM machines and built directions, different surface conditions, and different thicknesses were evaluated. Significant variability in defect characteristics based on location, especially in as-built surface specimens was observed. Well-optimized process parameters and post-processing reduced the overall volume fraction of defects, and the specified variabilities, and resulted in a more random dispersion of defects around the specimens. 2D and 3D defect analysis showed similar trends regarding correlations between defect characteristics and provided complementary information about the actual defect content based on their resolution. Keywords: Additive manufacturing, Defect characterization, Computed tomography, Defect variability, Ti-6Al-4V, 17-4 PH stainless steel