The influence of graphite on the physical, thermal, and mechanical properties of silica‐based ceramic cores

Abstract Due to their excellent thermal stability and chemical resistivity against molten metals, silica‐based ceramic cores have been prepared for use in nickel‐based superalloy investment casting via injection molding under 12 kPa pressure and 115°C temperature. This paper evaluated the effect of graphite as an additive on the thermal and mechanical properties of silica‐based ceramic cores. The results show that adding graphite increases the core's modulus of rupture (MOR) and hot MOR (at 1200°C) by 6% and 35% to 10.65 and 18 MPa, respectively. According to phase analysis by X‐ray diffraction, the presence of graphite reduced the crystallization behavior of fused silica and increased the open and closed porosity amounts by 2.5%–33.6%. Additionally, the formation of the in situ SiC phase due to reduction reactions decreases the shrinkage and enhances the strength of graphite‐containing bodies. No difference in the thermal expansion coefficient of samples in the presence of graphite has been detected.