Study On Preparation And Property Of Silica-Mullite Ceramic Cores Used For Hollow Blades

With the improvement of aero-engine performance, the cooling structure of blades becomes more and more complicated. Ceramic core is the key in casting technology, which become more and more important. Ceramic core has direct effect on the dimensional accuracy and manufacture cost of hollow turbine blades. Silica-based ceramic core has a low thermal expansion coefficient, excellent mechanical properties and good leachability, which is the good choice for the hollow blades.In this study, a series of SiO₂-Mullite ceramic cores were prepared by fused silica powders and mullite. This study investigated the influence of mullite species, particle size, weight percentage, morphology and mullite fibers weight percentage on the microstructure, phase composition and properties of SiO₂-Mullite ceramic cores via the injection molding method. Eventually, a ceramic core prepared by fused silica, fused mullite powders and mullite fibers, can meet the requirement of hollow blades casting.The fused mullite powders can promote the sintering of ceramic cores, and improve the creep deformation resistance of the cores at 1540 ℃ for 1 h. While the sintered mullite powders with high impurity is bad for creep deformation resistance of the cores. The ceramic core prepared by 15 wt% fused mullite powders（D50=18.9 μm） shows good properties after sintered at 1190 ℃ for 6 h. The shrinkage of the core is 1.06 %, the porosity is 28.67 %, the flexural strength is 22.11 MPa, the leaching rate is 0.052 g. min-1 and the creep deformation is 0.15 mm at 1540 ℃ for 1h.The mullite morphology also has influence on the properties of ceramic cores. Compared with the fused mullite powders, mullite fibers have a negative effect on the sintering of ceramic core, the shrinkage is significantly decreased and the porosity is increased leading to a good leachability. While for the shortage of cristobalite after sintered at 1190 ℃ for 6 h, the ceramic core has a high creep deformation, which can not meet the requirement of hollow turbine blades.When 2 wt% mullite fibers were introduced, the silica-mullite ceramic core shows good properties. The shrinkage is 0.65 %, the porosity is 33.96 %, the flexural strength is 23.2 MPa, the leaching rate is 0.13 g.min-1, the creep deformation at 1540 ℃ for 1 h is 0.18 mm, which can meet the requirement of hollow blades.