Porosity Evaluation in Laser Powder Bed Fusion Processed 316L-2.5%Cu: A Comparative Multi-Technique Study

Laser Powder Bed Fusion (L-PBF) has been recognized as a key additive manufacturing (AM) technique for the fabrication of complex metal components. Despite its advantages, the process has been affected by inherent defects such as porosity, which have been shown to influence mechanical properties and part reliability significantly. In this study, 316L stainless steel alloyed with 2.5 wt% copper was fabricated using L-PBF, and its porosity and relative density were analyzed under a wide range of processing parameters. A comprehensive evaluation was carried out using three distinct techniques: optical microscopy (OM), Archimedes density measurements, and X-ray computed tomography (XCT). These methods were employed to analyze pore morphology, including size, shape, and spatial distribution. The primary objective was to perform a comparative analysis of the precision and applicability of each technique for this specific alloy, which had not been extensively studied. In this study, relative density varied from 95.45% at high VED values to 99.04% in optimized conditions, highlighting the strong influence of processing parameters on defect content.The results revealed differences among the methods: XCT provided volumetric insight into internal porosity, OM offered high-resolution 2D surface analysis, and the Archimedes method was found to be sensitive to open pores and surface-connected defects. While XCT detected relative densities up to 99.04% with precise pore morphology classification, the Archimedes method slightly underestimated density in samples with surface-connected defects, and OM showed higher variability due to its 2D limitation. XCT revealed that pores with sphericity ≥0.45 and compactness ≥0.2 dominated in high-density samples, whereas irregular pores were more prevalent under excessive energy input. The study highlighted the importance of choosing suitable evaluation methods for analysing defect content in additively manufactured parts and demonstrated the influence of processing parameters on porosity characteristics.