Preparation method of ceramic shell for precision casting of large nickel-based high-temperature alloy casting

Abstract

The invention discloses a preparation method of a ceramic shell for precision casting of a large nickel-based high-temperature alloy casting. The preparation method comprises the following steps of immersing an investment pattern module into an surface layer coating, uniformly smearing the surface layer coating on the surface, and carrying out sand spraying and drying on the investment pattern module, thus completing the preparation of the surface layer; smearing the back layer coasting on the investment pattern module, and carrying out sand spraying and drying on the investment pattern module, and repeating this process several times to reach the required ceramic shell thickness, thus completing the back layer preparation; carrying out slurry sealing on the back layer coating and then carrying out drying, thus completing the preparation of a slurry sealing layer; and finally, carrying out dewaxing and high-temperature roasting treatment on the ceramic shell. According to the preparation method, lignocellulose is used as an additive in the ceramic shell slurry for the first time, so that wet blank bending strength and shell air permeability of the ceramic shell are improved, and meanwhile, the residual strength of the ceramic shell is reduced, and thereby the deformability of the ceramic shell is improved.

Description

technical field [0001] The invention relates to a technique in the field of investment casting, in particular to a method for preparing a ceramic mold shell for precision casting of a nickel-based superalloy large-scale casting. Background technique [0002] With the development of modern aviation and aerospace manufacturing technology, the design of the key hot-end components of the engine is increasingly functionally integrated and structurally integrated, so the size of the components also tends to be larger. In addition to the large size, such castings often have the structural characteristics of complex variable cross-section and large area and thin wall. Taking the high-temperature alloy turbine rear casing of the A380 large passenger aircraft as an example, its outline size is close to 2m, and the thin-walled structure with a wall thickness of 1-2mm accounts for more than 80% of the entire casting area, and there are several hollow support plates, lifting lugs, and bo...

AI Technical Summary

Problems solved by technology

The performance of the ceramic shell is very important for the pouring of large castings. This is because: First, the strength of the ceramic shell is often low because it has not been roasted before dewaxing. Under the condition of high temperature steam dewaxing, it is easy to cause Partial cracks occur in the wax mold due to thermal expansion. When filling the mold with hundreds of kilograms of molten metal, the huge impact force and static pressure will further expand the cracks and cause serious leakage of molten metal. Secondly, in the pouring process of large castings In the process, hundreds to thousands of kilograms of molten metal can be filled within tens of seconds. If the shell cannot quickly discharge the gas, under-casting at the air holes and blind cavities in the casting cannot be avoided; again, during the solidification and cooling process, if If the residual strength of the mold shell is too high and the yield is poor, the resistance of the casting will be greater when it shrinks, which will easily lead to the cracking of the casting

Therefore, how to improve the wet billet strength of large ceramic shells, the air permeability after firing and reduce the residual strength after pouring is the key to realize the complete molding of large castings. Patented technology for the strength, air permeability and yield of the shell

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