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Synchrotron micro-CT-based characterisation of additively manufactured open porous structures

Additive manufacturing (AM) of open porous metallic structures has great potential in advanced applications such as cooling or catalysis on small length-scales. For such applications, performance is strongly dependent on the 3D morphology, in particular, the surface geometry. X-ray microtomography (µCT) was used to analyse the surface morphology of an additively manufactured nickel-based alloy.

Various studies of functional structures additively manufactured using laser-based powder bed fusion (PBF-LB) have observed spherical particles attached to the surface of the structures. In this study, synchrotron X-ray microtomography (µCT) at beamline ID19 was applied to analyse the surface morphology of six different open porous samples made by PBF-LB of a nickel-based alloy. In contrast to classic functional design for AM, the open porosities considered in this study are the result of the

manufacturing parameters of the process (e.g., laser power and hatch spacing) and not of a detailed CAD-design. The analysis reveals that the laser scan strategy and process parameters of the 3D-printing setup have a major impact on the resulting surface area and the volume of the open porous structures (Figure 137). In particular, the surface area is increased by up to 57% due to the attached particles for the investigated samples, while their impact on the volume is considerably lower.

Understanding such dependencies of the material properties on the manufacturing parameters could be used to tailor the material to a specific application. These findings may then pave the way for adding an additional level of functionality to porous metallic samples produced by AM techniques. Furthermore, this study underlines the potential for obtaining new insights into AM when synchrotron µCT imaging and sophisticated data analysis are brought together. In particular, the high resolution (here 1.5 µm voxel size), in combination with the high synchrotron flux at high X-ray energies, enables detailed high-throughput 3D investigations of dense and complex materials.

Fig. 137: Overview of different features identified in the samples using synchrotron µCT imaging.

PRINCIPAL PUBLICATION AND AUTHORS

Principal publication and authors Synchrotron µ-CT-based morphological characterization of additively manufactured open porous structures, R. Otto (a,b), K. Sørby (b), B. Hesse (c,d), J. Gerber (c), E. Bortel (c), C. Kiener (a), Addit. Manuf. 55, 102874 (2022); https:/doi.org/10.1016/j.addma.2022.102874 (a) Siemens AG Technology (Germany) (b) Norwegian University of Science and Technology (Norway) (c) Xploraytion GmbH (Germany) (d) ESRF