Speaker
Description
Laser-based additive manufacturing processes such as Laser Powder Bed Fusion (L-PBF) and Directed Energy Deposition (DED) are intrinsically governed by highly dynamic thermal conditions. Local heat accumulation, cooling rates and spatial temperature distributions directly influence defect formation, such as keyhole porosity and lack of fusion, as well as the resulting microstructure and mechanical performance. Thermal methods provide a complete and scalable approach to investigate these phenomena across di erent high di usive and fast materials, across aluminum alloys (AlSi10Mg), nickel-based superalloys (Inconel 718), super-duplex (F55) and more conventional steels (AISI 316L). During fabrication, in-situ infrared monitoring is based not on absolute temperature measurement, which is strongly a ected by emissivity uncertainties and melt pool evaluation, but on the extraction of robust thermal features. Parameters such as maximum apparent temperature, cooling slope, and statistical thermal features of reconstructed thermal fields are correlated with process parameters such as laser power, scanning speed, energy density and build position. This feature-based approach allows the identification of stable operating ranges of process parameters and the detection of conditions leading to defect formation, such as keyhole porosity or lack of fusion, without requiring complex emissivity calibration. The methodology has been demonstrated to be implementable with both cooled infrared cameras and microbolometric sensors, enabling robust and scalable industrial deployment. Offline, active thermographic testing adopts a similar feature-extraction strategy to detect and localize sub superficial real defects, typical of additive manufacturing processes. Laser thermography has been applied as active thermographic technique to inspect specimens with process-induced and artificial defects of real and complex geometry, validated by micro-computed tomography. Detection capability is analysed as a function of defect type, depth, morphology and material thermal di usivity. Particular attention is devoted to the quantitative characterization of clusters of keyhole porosity and lack-of-fusion regions, which produce distinct thermal signatures. Across on-line monitoring and o -line non-destructive evaluation, thermal feature extraction provides a versatile methodology applicable to di erent additive manufacturing processes, materials, defect types, and inspection conditions. The consistent use of measurable thermal descriptors enables a quantitative characterization of process parameter ranges, defect formation mechanisms, and their influence on resulting material microstructure and final mechanical performance. Thermal analysis thus becomes a practical tool for evaluating both process stability and material integrity in metal additive manufacturing.
