Aero engine turbine blades are commonly produced via investment casting methods and utilise sacrificial ceramic cores to provide internal features such as cooling channels. During the firing process the conversion of the main ingredient (amorphous silica) into β-cristobalite plays a significant role, as it directly affects the dimensional stability, shrinkage and teachability of the core after casting. The formulation used to produce ceramic cores has evolved over the years in an iterative fashion, resulting in a deficit of understanding regarding the role of each component in the now complex formulation. Dilatometry was utilised to evaluate common additives to the amorphous silica system, such as zirconium silicate (zircon), alumina, aluminosilicate and magnesium oxide. Green bodies were prepared via die compaction, then pre-fired to 1200°C combining binder burnout with an initial sintering phase to give the ceramic mechanical strength. Subsequently samples were tested up to temperatures typical for casting (above 1500°C). Comparisons were made of the dimensional properties of the ceramic formulations during the pre-fire and the casting cycle. It was shown that the addition of aluminosilicate and zirconium silicate provides the desired dimensional stability during a simulated casting cycle.
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