Translated Abstract
Turbine blades are core hot end components in aero engines and gas turbines. The preparation method of silicon carbide ceramic materials based on stereolithography(SL) and gel casting provides a new way to fabricate the turbine blades. However, in this method, the drying and curing shrinkage have negative influence on the dimensional accuracy of ceramic green body. Hence, it is significant to reduce the drying and curing shrinkage of ceramic blade＇s green body.
The drying shrinkage of ceramic green body was reduced effectively through solid drying process. CaO powder was selected as the solid desiccant,and the influence of CaO particle size, crosslinking environment of monomer and relative humidity(RH) on drying shrinkage of green body was investigated.It was demonstrated that the drying shrinkage of green body was reduced to 0.12% in solid drying process at 40℃ and 40RH% when selecting CaO powder with a diameter of 2 μm as the desiccant after the ceramic body was set naturally. Also, investigation showed that solid drying process could reduce dehydration rate in the early stage of drying period, prolong the time of constant drying period as well as improve the uniformity of gel structure under the same conditions of temperature and humidity compared to heat drying process, so that the drying shrinkage of ceramic green body was reduced.
The curing shrinkage of the ceramic green body was reduced effectively by optimizing the preparation of slurry and adding carbon fiber. The relationship between particle interaction potential energy and particle spacing was analyzed, and based on which, the optimum solid content of ceramic slurry was determined. The particle model of the closest packing based on Dinger-Funk equation was applied to obtain the optimal volume fraction ratio of the cubic gradation. The adding of short carbon fibers was optimized, and the results illustrated that the addition of short carbon fibers can reduce the curing shrinkage and shrinkage anisotropy effectively. Moreover, the continuous carbon fiber preform reduced the curing shrinkage of ceramic green body significantly and the curing shrinkage of the preform was reduced to 0.015% by adding short carbon fibers, reducing 86.73% when compared with the results without short carbon fiber.
The curing deformation of the blade＇s green body was reduced effectively by optimizing the placing angle of the blade and adopting surface compensation technique. The influence of the placing angle on the curing distortion of the blade green body was analyzed, it was revealed that the curing distortion of trailing edge of the blade green body was reduced to 0.129° when the placing angle is 315°, which is 84.86% lower than before. The surface compensation model based on nodal deformation was established,and iterative analysis on the surface compensation process was carried out by using finite element software and reverse precision software. It was experimentally proved that the negative mean deviation of the blade was reduced to 0.177 mm with a decrease of 42.16%. Also, the section of z=85 was translated 0.116 mm and 0.069 mm in the X and Y directions respectively with a twist angle of 0.04° .
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