Fabrication and properties of silica-based ceramic cores modified by mullite powders with different particle sizes

Ceramic cores provide complex internal cavity structures in the investment precision castings of hollow blades for aero-engine. The silica/mullite ceramic cores were fabricated by hot injection molding, adding fused mullite powders with different particle sizes as mineralizers. The particle size of mullite mineralizers on the crystallization and properties of ceramic cores was investigated in the paper. The result shows that the mullite mineralizers promote the crystallization of cristobalite in ceramic cores, and finer mullite powders can further improve the heterogeneous nucleation, and generate larger quantities of cristobalite. Mullite mineralizers with large particle size can lead to low sintering degree, poor mechanical properties and creep resistance of ceramic cores. While the particle size of mullite mineralizers is too small, the core contains too much quartzite crystal phase, and the microcrack occurs during the phase transformation during cooling, which also causes the deterioration of the strength at room temperature and the high temperature deformation resistance ability. The ceramic cores with mullite powders in particle size of 19 μm show excellent comprehensive performance, with linear shrinkage of 0.65%, porosity of 31.8%, room temperature strength of 17.8 MPa, high temperature creep deformation of 0.4 mm, and leaching rate of 0.06 g/min