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Additive manufacturing techniques are being extended to refractory metals and other metals capable of operating in high-temperature environments. Many of these metals are high-Z and high density necessitating higher x-ray inspection energies. 3D volumetric X-ray computed tomography (X-ray CT) has emerged as a strategic inspection choice for these parts. The internal channels and features of these parts are often complicated and can articulate in spiral configurations for longer chord lengths that are difficult to inspect in a single or ensemble of radiographs. In particular, it is the entire 3D structure of the part that is of interest not just one or two locations in the volume. At the same time, 3D printing is extending the spatial resolution limits for small, manufactured details and defects, which impacts the target resolution. CT inspection requirements for these parts include resolution down to 0.1 mm at MeV energies. In this context, properties of the GLO transparent ceramic scintillator (Gd0.3Lu1.6Eu0.1O3): high-stopping power, high-brightness, high transparency in large area plates combined to produce high intrinsic spatial resolution, could be pivotal for delivering 3D inspections of these parts. Radiabeam LLC has configured an area-detector CT camera-scintillator system employing GLO (other scintillators have been used in this system) in combination with the ARCIS LINAC (adjustable from 2-9 MeV). A variety of AM-fabricated refractory metal components have been scanned at 7.8 MeV, providing robust transmitted signal for high density parts with 2-3” chord lengths, in parts that are up to 6 inches in diameter. Lens-coupled X-ray CT using a transparent scintillator imaged on a sCMOS camera obtains higher spatial resolution than the more commonly employed phosphor-enhanced amorphous silicon (A-Si) panels. The result is higher contrast imaging due to increased stopping power. Interior features of the additively manufactured components have been resolved down to a voxel size of 80 microns. Inspection data from this system with representative AM parts will be reviewed and evaluated.
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