Synchrotron X-ray tomography for microstructural characterisation of ceramic cores fabricated by injection moulding and additive manufacturing

Ceramic cores for investment casting are sacrificial tools that create complex geometries for internal cooling passages in turbine blades. Increasing engine performance requires intricate geometries that are difficult to achieve using conventional ceramic injection moulding. This difficulty motivates the use of additive manufacturing, as it offers greater design freedom and reduced production times. The behaviour of these ceramics is governed by key microstructural features, including porosity, grain size, and spatial distribution of ceramic additives. In this study, synchrotron X-ray computed tomography (SXCT) is employed to investigate the 3D microstructure of sintered silica-based ceramic cores with micrometre-scale resolution. This approach enables the quantitative visualisation of critical 3D features that are inaccessible to conventional 2D characterisation techniques. Two injection-moulded cores with different compositions are compared with a core produced by additive manufacturing via digital light processing. The SXCT analysis reveals pronounced process-dependent differences in microstructure. Injection-moulded cores exhibit an interconnected pore network with heterogeneous spatial distribution and few closed pores, alongside zircon agglomeration. Grain orientation analysis indicates different grain alignments associated with mould geometry and injection conditions. By contrast, the additively manufactured core presents a lamellar microstructure aligned with the build direction, revealing periodic variations in porosity and grain size distribution associated with the layer-wise printing process. These findings demonstrate how processing routes influence the 3D microstructure of ceramic cores, providing a quantitative basis for linking manufacturing-induced features to macroscopic material properties. Ultimately, this high-resolution microstructural characterisation supports quality assessment and optimisation of ceramic cores for applications in aerospace.