Study On Fabrication And Properties Of BaZrO₃ Based Ceramic Core Materials For Hollow Blades

In recent years,with the vigorous development of the aviation industry,aero engines have continued to move in the direction of high thrust-to-weight ratio,and turbine inlet gas temperature continuously rising,which has put forward higher property requirements for the hollow blades and ceramic cores of the engine.However,with the appearance of Nb-Si based superalloy hollow blades,the existing ceramic cores’ properties have not met the casting requirements of new kind of blades.This study uses barium zirconate as the matrix material of the ceramic cores,the effect of particle size,sintering parameters（sintering temperature and holding time）and the addition of the second phase（ZrO₂,Y2O3 and Al2O3）on the properties of ceramic cores were studied.Experimental results show:（1）With the decrease of the coarse particles content and the increase of the fine particles content in the matrix material,the sintering shrinkage and bending strength of the core sample gradually increase,the apparent porosity gradually decreases.When the mass ratio of particle size matching is 200 mesh: 325 mesh=1:1,the core sample have better comprehensive properties,the sintering shrinkage is 2.15%,the apparent porosity is 25.9%,the bending strength is 64.62 MPa.（2）With the increase of the sintering temperature and the extension of the holding time,the sintering shrinkage and bending strength of core samples gradually increase,the apparent porosity gradually decreases.By comparing and analyzing the properties of core samples prepared under different sintering parameters,it is confirmed that the sintering temperature is between 1500℃ and 1600℃,and the holding time is 2h.（3）Add ZrO₂ in an appropriate amount to form the mechanical mixture with the matrix material to improve the high-temperature deformation resistance of the core sample,increase the apparent porosity,and reduce the difficulty of core removal.Appropriate addition of Y2O3 will form the solid solution with the matrix material,significantly reduce the sintering shrinkage of the core sample,improve the hightemperature deformation resistance and maintain the high bending strength.The addition of Al2O3 forms the compound with the matrix material,which significantly improves the high-temperature deformation resistance of the core sample,but it will cause a significant increase in sintering shrinkage,a significant reduction in apparent porosity,and more difficult core removal.（4）The core sample is immersed in the dilute nitric acid solution for corrosion.The higher the temperature of the corrosive solution,the faster the corrosion rate.The corrosion process of the core sample in the boiling dilute nitric acid solution is as follows: In the initial stage of the corrosion process,the corrosion rate is relatively slow,after which it shows an increasing trend,and then gradually decreases.By comparing and analyzing the corrosion properties of core samples with different properties characteristics,it is known that the degree of difficulty of corrosion is dominated by its own structure.The denser the structure,the more difficult it is to corrode.If there is no significant difference in the structure,it will be affected by its own material characteristics,and the more likely it is to corrode,the shorter the corrosion time will be.