A kind of preparation method of special-shaped section chopped carbon fiber modified ceramic mold shell

Abstract

The invention relates to the field of precision casting of high-temperature alloy vacuum furnaces, in particular to a method for preparing a modified ceramic mold shell through special-shaped cross section short carbon fibers. The mold shell is a compound shell and comprises a surface layer and a back layer modified by adding the special-shaped cross section short carbon fibers. The method comprises the preparation steps that surface layer slurry and back layer slurry are prepared correspondingly; the short carbon fibers which are evenly scattered in advance are added into the back layer slurry; the surface layer is coated with the surface layer slurry, the back layer is coated with the back layer slurry, and sand is sprayed to the surface layer and the back layer; the slurry coating and sand spraying operations are conducted repeatedly till a preset number of layers is met; the surface layer slurry is used for slurry sealing, and the mold shell is dewaxed; and the mold shell is cooled in a furnace after being roasted. According to the mold shell prepared through the method, the fibers are scattered evenly and are not likely to be pulled out and lose efficacy, the strength of the mold shell is improved, the thickness of the mold shell is reduced, the heat dissipation performance of the mold shell is enhanced, the performance requirements for thin walls and high strength are met, and the yield of single-crystal blades is increased.

Description

technical field [0001] The invention relates to the field of high-temperature alloy vacuum furnace precision casting, in particular to a method for preparing a modified ceramic mold shell with special-shaped cross-section chopped carbon fiber. Background technique [0002] The preparation of superalloy columnar crystal / single crystal structure by directional solidification technology is a key technology in the manufacture of aeroengine turbine blades and gas turbine blades; in order to obtain high-quality superalloy blades, ceramic shells are required to have sufficient strength and excellent heat dissipation performance. The commonly used formwork strengthening method in production is to increase the number of formwork layers, but this method is obviously contrary to the technical requirements of increasing the temperature gradient by reducing the formwork thickness in the directional solidification process. [0003] The axial strength and modulus of carbon fiber are high, ...

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Problems solved by technology

[0003] The axial strength and modulus of carbon fiber are high, the specific heat is between non-metal and metal, and the performance is stable. It is suitable for applying it to the preparation of formwork to improve the strength and heat dissipation performance; Chinese Patent Document No. CN103252448A records "a kind of "Preparation method of thin-walled high-strength formwork for single crystal blades", this method is to use continuous carbon fiber cloth to cover the baked formwork to increase the strength. Although this method has a certain strengthening effect, it can only strengthen the surface of the formwork. The heat dissipation ability cannot solve the huge thermal resistance problem of the thick mold shell itself. In addition, this method has the disadvantages of complicated process and high cost of carbon fiber cloth.

[0004] Chinese patent document number CN103192062A records "a formwork for the manufacture of superalloy single crystal blades". The back layer of the formwork is directly made of a good thermal conductor material such as silicon carbide or graphite powder as the back sand. The thermal conductivity of the mold shell is greatly improved, but the strength of the back layer is significantly reduced. In addition, because graphite is easy to oxidize, the firing process is complicated.

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