Basic Research On The Preparation Process Of 3D Printed Silica Based Ceramic Cores

Aero-engine is the core component that provides the power source of aircraft.Turbine blade is one of the important factors affecting the performance of the engine.The ceramic core is the key to forming the cooling structure of the inner cavity of the blade,which greatly affects the qualification rate and cost of casting production.Silica based ceramic cores have the characteristics of small thermal expansion coefficient,easy to be dissolved by alkali,can be sintered in a lower temperature range and have good sintering performance.At present,they are mainly used in the manufacture of directional solidification hollow turbine blades.3D printing technology has the advantages of high model freedom,less material waste,high dimensional accuracy of finished products,and no need to manufacture molds in advance,and models can be modified arbitrarily.However,the use of 3D printing technology to prepare ceramic cores is still in the exploratory stage and has not been applied on a large scale,and the prepared silica based ceramic cores have large firing shrinkage and poor high temperature performance.In this paper,the effects of printing parameters,sintering parameters and high temperature strengthening on the performance of 3D printed silica based ceramic cores were studied,and a certain amount of zirconium silicate was added as an additive to improve the high temperature performance of the core.The obtained results are as follows:Printing parameters have an impact on the dimensional accuracy of 3D printed ceramic core samples.There are two options for the molding parameters of the printing equipment used in this experiment,namely support and part.According to the experimental test,when part is selected as the molding parameter and Z-axis compensation is not added,the dimensional deviation in each direction of X/Y/Z is less than±0.1mm,which meets the accuracy requirements,and the orientation of the model has no effect on the printing accuracy.The sintering parameters have a significant effect on the comprehensive properties of the core.With the increase of sintering temperature,the firing shrinkage of the core increases,the apparent porosity decreases,the bulk density rises,the room temperature strength improves,and the high temperature creep resistance enhances.Increasing the sintering temperature and prolonging the holding time will promote the sintering of the core and the crystallization of the quartz glass.The optimum sintering parameters for pure silica based ceramic cores are 1210℃for 480min.The strengthening treatment has a great influence on the room temperature strength and high temperature creep resistance of the core.Using ethyl silicate hydrolyzate as strengthening agent,with the increase of strengthening time and strengthening times,the room temperature strength of the core gradually improves,the porosity decreases,and the high temperature deflection reduces.The pure silica based ceramic core with the sintering parameter of 1210℃for 480min,after three high temperature strengthening,the room temperature strength is as high as 45.3MPa,and the high temperature deflection is 6.40mm.Additives affect the phase composition and comprehensive properties of ceramic cores.The high temperature performance of the ceramic core added with zirconium silicate is significantly improved.When the addition amount of zirconium silicate is15wt%,the high temperature strength of the core after sintering at 1180℃for 480min is37.13MPa,and the deflection of the core is greatly reduced to 1.78mm,the firing shrinkage rate is 1.95～4.31%,the apparent porosity is 30.23%,the bulk density is1.74g/cm~3,and the room temperature strength is 8.93MPa.