The mechanical and thermal behaviors of porous silica-based ceramic cores for preformation of internal cooling passages in gas turbine blades were studied. The silica-based ceramic cores are composed of fused silica and zircon powders, and silicon carbide powder (SiC) was added to improve the mechanical and thermal properties of the silica-based ceramic cores. Cristobalite, which was formed by crystallization of amorphous silica on SiC surface, improved the flexural strength, bulk density and thermal conductivity of silica-based ceramic cores up to an addition of 10 wt% SiC. The SiC on the silica-based ceramic cores enhanced the thermal conductivity, because SiC has higher thermal conductivity compared with matrix materials of ceramic cores (fused silica and zircon). However, in case of 20 wt% SiC on ceramic core, the crystallization of fused silica was accelerated due to SiC addition which acts as a seed of crystallization, therefore, many microcracks were generated by phase transformation (β→α) of cristobalite. As a result, the flexural strength, relative density and thermal conductivity of the ceramic core with 20 wt% SiC were reduced.

Keywords: Ceramic core, Fused silica, Porous ceramics, Silicon carbide, Thermal conductivity.