Preparation Of Easy-collapsible Alumina Based Ceramic Cores

Alumina based ceramic cores are widely used in the casting of turbine blades, golf ball head, and other demanding precision casting due to its high temperature resistance, good chemical stability, high temperature creep resistance, low cost and can be fabricated to complex structures with high dimensional accuracy. However, Aluminum oxide is hard to react quickly with strong alkali and acid, it can’t be easily removed through dissolving in the alkali or acid solutions. Thus, the leaching out effect of Alumina based ceramic core which main components are Aluminum oxide is not good enough to meet the need of industrial production. Therefore, it is of great significance to study on improving the collapsibility of Alumina based ceramic cores.Firstly, this study is focused on three preparation methods of Alumina based ceramic cores, Then the flexural strength at room temperature, residual strength at high temperature and soluble loss property of the cores prepared by these methods were compared and analyzed. It is found that the collapsibility of the samples made by pressure molding and phenolic resin is the best among them.The orthogonal method was applied to investigate the ingredients, the particle sizes and contents of Si O2 and Al2O3, The influences of these factors on the performance of core samples were discussed. It is found that the particle size of Al2O3 has a great influence on the flexural strength at room temperature, residual strength at high temperature and soluble loss. The further investigate on the relationship between the particle size of Al2O3 and the properties of ceramic cores. The experimental results show that, among the samples with room temperature flexural strength of higher than 8~10MPa, the samples with best collapsibility was prepared by the Al2O3 powder with the fineness 200 mesh, and its residual strength at high temperature is about 3.0MPa, the soluble loss rate reaches about 1.22% min-1.In addition, in this paper, the influences of the stripping methods(alkali boiling in normal pressure and alkali boiling in the reaction kettle with pressure), the stripping mediμm and the alkali boiling time on soluble loss were discussed. XRD(x-ray diffraction), SEM(scanning electron microscope), etc. were used to investigate the microstructure and the change of phase composition of ceramic cores. In terms of the results, the leaching speed tends to increase with the increase of the apparent porosity; the samples can’t be dissolved in boiling water and the leach speed in boiling alkali solution can reach about 3.20% min-1; the alkali boiling time should not be more than 3 hours; and it’s more economical and safer for boiling in alkali solution in normal pressure than in the reaction kettle with pressure.