不同粒度莫来石粉改性硅基陶瓷型芯的制备及性能

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

陶瓷型芯在航空发动机空心涡轮叶片的熔模精密铸造中提供复杂内腔结构。采用不同粒径的电熔莫来石粉作为添加剂,利用热压注法制备氧化硅/莫来石陶瓷型芯,研究莫来石粒径对型芯析晶行为和性能的影响。结果表明:莫来石粉的加入促进方石英的析晶,较细莫来石对不均匀形核的促进更加明显,会产生更多的方石英晶相;粒径过大的莫来石粉会导致型芯烧结程度低,力学性能和抗蠕变能力较差;当莫来石粉的粒径过小时,型芯内含有过多的方石英晶相,冷却中相变产生微裂纹,也会引起室温强度和抗高温变形能力恶化;莫来石粒径为19μm的陶瓷型芯表现出良好的综合性能:线收缩率为0.65%,气孔率为31.8%,室温弯曲强度为17.8 MPa,1540℃的蠕变为0.4 mm,溶蚀率为0.06 g/min。

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 19μm 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.