The Research On Modification Of Alumina Ceramic Cores By Adding Andalusite

Along with the development of the blade cooling technology, the coolingchannels in the blade are becoming more and more complex, and blade cooling effectsare greatly improved. It means, in the production process of blade, ceramic cores formaking hollow blades must bear the even more pressure derived from more complexstructure and more harsh working conditions. Thus the ceramic cores with higherrequest are needed. Due to the high characteristics of alumina including highrefractoriness, high chemical stability and high heat stability, the performance ofalumina-based ceramic cores are guaranteed. However, due to the high chemicalstability of alumina, it is difficult to remove from the samples.In this paper, alumina are choosed as substrate material to prepare a1umna-basedceramic core. While andalusite are added to introduce mullite and quartz glass, whichcan improve the strength, thermal stability and reduce the difficulty of core leach.Consequently, a1umna-based ceramic cores with good comprehensive properties areobtained.The main results are as follows:(1) The proper proportion of alumina powders mixture is before milling: after2hmilling=7:3. In this mixture, coarse grains form skeleton, fine grains fill the poresbetween skeleton, thus, the porosity is reduced. The existence of active fine particlesmake the green body better sintered. The sample shows better performance, that isproper porosity, bibulous rate, volume density, flexural strength and firing shrinkage..(2) Mixture of2.5wt%magnesia and2.5wt%titanium dioxide are choosed as themineralizer. MgO controls the microstructure, TiO2reduces the sintering temperature.Simultaneously working, they make properties of samples better.(3) When amount is about0~30wt%or45~65wt%, the existence of andalusitecan improve bending strength and thermal shock resistance, and decreases linearexpansion coefficient of the alumina ceramic cores, by effectively promoting thesintering and forming mullite networks.(4) Determined by the experiments, we can summerize the optimal formula andtechnology: the sample of alumina ceramic core with best properties are made ofmixed alumina powders (before milling: after2h milling=7:3) added with25wt% andalusite and2.5wt%MgO and2.5wt%TiO2as mineralizers, and are compressionmoulded at30Mpa and sintered at room temperature to1400℃.