Effects Of Corundum And Other Additives On The Properties Of Silica Oxide Ceramic Cores

Study on the ceramic core has an important reference value for the production of the hollow blade. The overall performances of the ceramic core include strength, heat deflection, porosity, shrinkage, etc. This paper is committed to improve the high temperature strength of the silicon-based ceramic core, ensuring the large and complex silicon-based ceramic core can be used in the current actual production.This paper summarized the results of previous research and application, through a lot of experiments to determine the basic components of the core; and through measuring bending strength, high temperature deflection, shrinkage, open porosity, etc., and by microstructure observation and phase analysis, research on the effect of the corundum powder, pre-cristobalite and Na OH on the silicon-based ceramic core was conducted, and ultimately a more reasonable ceramic core component and manufacturing process parameters were received.Adding corundum powder made the flexural strength at room temperature of ceramic core increased. For example, the bending strength of the ceramic core in which added 5% 200 mesh corundum powder reached 18.614 MPa,increasing about 7.4MPa; the shrinkage rate was 1.364%;and at 1550℃ about 30 min,the deflection was 1.833 mm. The ratio of the mesh sizes of corundum powder should be considered with the particle size distribution of the overall powder. When the content of the corundum powder is 15%, and the ratio of the corundum powder mesh sizes is 200 mesh: 400 mesh: 600 mesh to 5: 3: 2,the ceramic cores had better overall performances than the original ceramic core. Besides, compared to 1200℃, the final firing temperature 1180℃ mde the ceramic core performances better.Pre-cristobalite have some improvement in the overall performance of the ceramic core. A certain amount of pre-cristobalite help improve ceramic core shrinkage and high temperature performances, but the amount need to reasonably control。The the ceramic core which added 5% cristobalite has a good high temperature performance,and the deflection reduced to 0.816 mm holding temperature 1550℃ about 30 min, the shrinkage rate reduced 0.306%, and bending strength fell to 14.162 MPa.A small amount of Na OH added to the ceramic core changed the performances clearly. Adding 0.5% Na OH into the ceramic core, the shrinkage rate decreaced to 0.45%,with a good dimensional accuracy;the porosity rosed to 0.356%;and the deflection at 1550℃ changed little as 1.25 mm. However, the amount of Na+ should be strictly controled to ensure a good overall performances.