Effect of CaO and SiO2 on the properties of Y2O3-based ceramic core materials

Abstract

Nb-Si alloy is an important candidate material to produce hollow turbine blades in the aero-space industry. However, the ultra-high melting temperature of Nb-Si alloy (≥1750°C) makes the traditional ceramic core made of Al2O3 (poor leachibility) or SiO2 (melting temperature) invalid in the production of Nb-Si hollow turbine blades. In this study, Y2O3 were used as the ceramic core matrix due to its high melting points, high strength, and low interfacial reactivity. CaO and SiO2 were added in Y2O3 matrix to improve the leachability and high temperature flexural strength (1500°C) of ceramic cores. The other properties such as porosity, shrinkage and bulk density were investigated as well. The results showed that the introduction of CaO in Y2O3-based ceramic cores improved the leachability. The addition of SiO2 in the Y2 O3-CaO matrix could greatly improve the high temperature flexural strength, and keep a good leach-ability at the same time. The best comprehensive properties of Y2O3-based ceramic cores were obtained when it contained 12 wt% CaO and 4 wt% SiO2. The new developed Y2O3-based ceramic cores with the addition of CaO and SiO2 has the potential to meet the extreme requirements in the casting of Nb-Si alloy hollow turbine blades.