Study On Filling Performance Of Alumina Based Ceramic Cores For Investment Casting Super Alloy Blades

Alumina based ceramic cores, used for producing blades of super alloy, are of good chemical stability and creep resistance. They can guarantee the dimensional precision and qualified rate of directional solidification hollow blades and single crystal hollow blades, which have complex bore structures, and decrease the manufacturing cost. But in actual production there are many problems in the die filling process, which restrict the application of alumina based ceramic cores.In this paper, the rheological property of alumina based ceramic cores slurry has been systematically investigated. It is found that the slurry has a settlement process and thixotropic property. The viscosity of slurry is changed with temperature, and these changes are related with the liquidity of paraffin wax. In the higher temperature, the changes of the viscosity are not obvious; in the lower temperature, the viscosity increases sharply. In the low rate of shear, along with the increase of rate, the viscosity of slurry reduces; in the high rate, the result is contrary.In order to research the different factors affecting the performance of die filling of the fusible pattern, the mold for evaluating the slurry of alumina based ceramic cores is well designed. After selecting the suitable slurry temperature, mold temperature and die filling pressure, the orthogonal experiments have been carried on. The results show that the pressure is the biggest influencing factor in the filling of slurry and the mold temperature is the least.The analysis of ceramic cores grains indicates that the granules are composed of different size particles. The bigger particles form high temperature framework after sintering, and fine particles fill the interspaces between the coarse granules to reinforce the framework, which make the ceramic core have a good sintering strength. It has a higher rate of porosity, which is good for leaching. In the high temperature the thermal expansion and thermal expansivity of ceramic cores are small, and the size stability is extremely good. The changes of alumina and silica phase are very little.