| The ability to improve the heat dissipation of turbine blades through complex air-cooled internal cavity structure has become the key to advanced engine manufacturing.The ceramic core is the core component for casting blades with complex air-cooled internal cavity structure.Therefore,it has vital research significance and practical value.At present,the ceramic cores used in the manufacture of high efficiency gas-cooled turbine blade are mainly divided into silicon oxide based ceramic core and alumina ceramic core according to the matrix material at home and abroad.The porosity of ceramic core has a great influence on its removal efficiency,the higher porosity,the easier to remove it.Thus,it is one of the main methods to develop high performance ceramic core to ensure the strength and improve the porosity at the same time.In the research,aluminum oxide based ceramic core material was prepared by gel injection molding using molten corundum as matrix material and alumina fiber cotton as adding phase and the related properties were characterized.In this paper,the effects of pH,dispersant,milling time,fiber and solid phase on the viscosity of the slurry were investigated.The viscosity of the prepared slurry is the lowest about174mPa·s at solid phase content of 45 wt.%,pH value is 9,ball milling is 24 h,dispersant is0.7wt.%,and the amount of fiber addition is 4wt.%.The effects of heating drying and vacuum freeze drying on the blank were investigated.The specimens are obviously warped and deformed after heat drying,and the deformation is small after vacuum freeze drying.The splines are completely dried and not deformed under the experimental conditions of pre-freezing for 5h and vacuum freezer for 24 h.The peeling phenomenon of the body after drying was also studied,and the result show that the peeling of the body is inhibited completely with 1wt.% of polyacrylamide.The properties of ceramics prepared by gel molding were studied.The strength of ceramic sample increases first and then decreases with the increase of the solid content were found.Bending strength of the ceramic sample reached 58.23 Mpa,which the solid content is 55 wt.%,volume density of the ceramic sample decreases and the porosity increases with fiber content increases.The volume density of ceramic samples increases and the porosity decreases with the increase of sintering temperature and holding time.The bending strength of the ceramic sample reached the maximum value of 80.25 MPa and the porosity is51.26% when the solid content is 55 wt.%,the fiber additive amount is 4wt.%,the sintering temperature is 1600°C,and the holding time is 8h.The bending strength and porosity is increased 37.82% and 17.43% respectively compared with ceramic samples without fiber addition. |
