Method for preparing thick-walled ceramic matrix composites by machining-assisted cvi

Abstract

The invention relates to a mechanical processing-assisted CVI method for preparing a ceramic matrix composite material thick-walled part (≥5mm), comprising the following steps: depositing a prefabricated body in a graphite furnace for interfacial layer deposition; and densifying the prefabricated body by chemical vapor infiltration treatment, the relative density of the preform reaches 20% to 65%, and then it is taken out; the preform is processed with micropores by mechanical processing, so as to dredge the transmission channel of the gaseous precursor; and the ceramic matrix composite material is obtained by cyclic deposition. The advantages of this process: (1) It improves the pore structure of the preform itself, reduces the density gradient of the composite material, and effectively solves the problem of uneven density of ceramic matrix composite thick-walled parts (≥5mm); (2) improves (3) Improve the densification speed and shorten the preparation cycle.

Description

technical field [0001] The invention belongs to the field of CVI preparation of ceramic matrix composite materials, and in particular relates to a method for preparing thick-walled ceramic matrix composite materials with mechanical processing assisted CVI. The gaseous precursor diffusion channel inside the preform enables the formation of multi-scale mass transfer channels in the porous body: intra-bundle holes, inter-bundle holes and processing holes, thereby improving the compactness and density of ceramic matrix composite thick-walled parts (≥5mm). Density uniformity to achieve high density and high strength preparation of ceramic matrix composites. Background technique [0002] Ceramic matrix composites can meet the requirements of long life below 1650°C, limited life below 20000°C, and instantaneous life below 2800°C. Thermal systems, cruise missile engines, liquid and solid rocket engines and other weapons and equipment fields have broad prospects for promotion and ap...

AI Technical Summary

Problems solved by technology

In US Patent 4580524, the FCVI method is used to prepare ceramic matrix composites, which can effectively shorten the densification process and improve the density uniformity. However, the heating of each area in the preform mainly depends on heat conduction, resulting in insufficient densification of the cold surface of the preform.

In the German patent DE4142261, the isothermal pressure gradient CVI process is used to prepare porous structure composite materials, which effectively improves the gas transmission capacity, but there is still the problem of uneven densification

Literature "Microwave Heated Chemical Vapor Infiltration: Densification Mechanism of SiC f / SiC Composites.David Jaglin, Jon Binner, and Bala Vaidhyanathan.The American Ceramic Society, 2006,9:2710-2717"proposed the use of microwave pyrolysis to densify SiC f / SiC composite material, this process can make the average density of the composite material reach 50%, and the center density of the composite material reach 73% within 24 hours, speed up the densification rate of the prefabricated body, and improve the density uniformity, but the process is harmful to the equipment The requirements are relatively high, and it is still in the experimental stage

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