A densification forming method suitable for multi-configuration SiC / SiC composite materials

Abstract

The application belongs to the technical field of ceramic matrix composite structure development, and relates to a densification forming method suitable for SiC / SiC composite materials with multiple configurations. The method solves the problem that the air permeability / liquidity and structural stability of the mold are difficult to balance in the gas-liquid combined process by optimizing the conformal surface design of the mold, reserving the thermal expansion compensation amount, opening the through hole, designing the external fixture and designing the modular structure, and combining specific process steps. The optimized mold can effectively balance the air permeability / liquidity and structural stability of the mold, reduce the deformation risk, thereby improving the component size precision and surface quality, while ensuring uniform penetration of the gas and liquid, shortening the densification cycle and reducing the process cost.

Description

Technical Field

[0001] This invention relates to the field of ceramic matrix composite structural component manufacturing technology, and in particular to a densification molding method applicable to multi-configuration SiC / SiC composite materials. Background Technology

[0002] SiC / SiC composites are considered ideal materials for hot-end components of aero-engines and gas turbines due to their excellent high-temperature performance, oxidation resistance, and corrosion resistance. In their preparation, a combined gas-liquid process, namely chemical vapor deposition (CVI) and precursor impregnation pyrolysis (PIP), demonstrates unique advantages. CVI can construct the initial matrix framework structure by depositing SiC matrix inside a porous preform, exhibiting high strength and minimal damage to fibers. Meanwhile, PIP, leveraging the excellent permeability of the liquid polymer precursor, can effectively fill the closed pores and micropores left after the CVI process. The synergistic use of these two processes enables stepwise filling from the macroscopic to the microscopic scale, significantly improving the material's density and mechanical properties, making it an effective approach for preparing high-performance, complex-structured SiC / SiC components.

[0003] However, in the densification process of SiC / SiC composite components using this combined process, the molding die must simultaneously meet the specific requirements of both processes for permeability and liquid properties. That is, it must have a sufficient number and size of ventilation / impregnation holes, and the die wall thickness should not be too large to ensure smooth penetration of gas precursors and liquid polymers. At the same time, the die must also maintain structural stability in a high-temperature deposition and pyrolysis environment to meet the strict requirements for component molding accuracy.

[0004] In actual processes, it is often difficult to balance the above two requirements. If the mold is excessively thinned or the opening is enlarged to improve air / liquid permeability, the mold will become less rigid at high temperatures and more prone to deformation, which will affect the dimensional accuracy of the components. Conversely, if the mold thickness is increased or the opening is reduced to ensure structural strength, the transmission and permeation of gas and liquid will be significantly hindered, the densification cycle will be prolonged, and the process cost will be increased.

[0005] In summary, the existing SiC / SiC composite material component densification molding technology cannot simultaneously address the issues of mold permeability / liquidity and structural stability, thus failing to balance the dimensional accuracy and process cost of SiC / SiC composite material components. Summary of the Invention

[0006] The purpose of this invention is to provide a densification molding method suitable for multi-configuration SiC / SiC composite materials. By optimizing the conformal surface design of the mold, reserving thermal expansion compensation, opening through holes, designing external fixtures, and designing a modular structure, and combining specific process steps, the problem of balancing gas / liquid permeability and structural stability of the mold in the gas-liquid combination process is solved. Optimizing the mold can effectively balance the gas / liquid permeability and structural stability of the mold, reduce the risk of deformation, thereby improving the dimensional accuracy and surface quality of the component, while ensuring uniform gas and liquid penetration, shortening the densification cycle, and reducing process costs.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a densification molding method suitable for multi-configuration SiC / SiC composite materials, comprising the following steps: Configure a molding die, which includes multiple separable and combinable modules, including an outer mold and / or a core mold. The molding die has a profile that conforms to the surface morphology of the SiC / SiC composite component. The profile is reserved for thermal expansion compensation and through holes are opened on the profile according to preset parameters. The fiber preform is installed and positioned in the cavity of the molding mold, and the molding mold is locked with clamps. After the mold is locked, the fiber preform is shaped and then demolded. After the shaped fiber preform undergoes heat treatment to remove adhesive, a deposition layer is formed on the surface of the fiber preform to create a deposition interface layer. A fiber preform with a deposition interface layer is loaded into a molding mold, placed in a deposition environment, and SiC matrix chemical vapor deposition is performed. Then, at least one precursor impregnation and pyrolysis process is performed to achieve densification of SiC / SiC composite material before demolding to obtain SiC / SiC composite material blank. Machining of SiC / SiC composite blanks to obtain SiC / SiC composite components.

[0008] As one possible implementation, the thickness of the forming mold in the area where the profile is located is greater than or equal to 10 mm and less than or equal to 30 mm.

[0009] As one possible implementation method, the thermal expansion compensation amount is determined in the following way: ΔD=D0×α×ΔT Where ΔD is the thermal expansion compensation amount, D0 is the thickness or diameter of the SiC / SiC composite component at room temperature, α is the thermal expansion coefficient of the molding die material, and ΔT is the difference between the highest temperature during the densification process and room temperature.

[0010] As one possible implementation, the volume of all through holes on the profile is 10% to 20% of the volume of the profile area.

[0011] As one possible implementation, a clamp is used to lock the forming mold, and after the mold is locked, the fiber preform is shaped, including: The wet molding process involves installing and positioning the softened fiber preform into the cavity of the molding mold, applying pressure to make it adhere to the outer mold surface, closing the mold with bolts and / or tenon joints, locking it with clamps, and then placing the whole assembly into an oven for shaping.

[0012] As one possible approach, the shaped fiber preform undergoes heat treatment to remove adhesive. Specifically, the shaped fiber preform is placed in a vacuum environment for heat treatment at a temperature of 500–800°C for 1–3 hours.

[0013] As one possible implementation, the interface layer is a pyrolytic carbon interface layer, a boron nitride interface layer, a silicon carbide interface layer, or a multiphase interface layer.

[0014] As one possible implementation method, the conditions for SiC matrix chemical vapor deposition are as follows: trichloromethylsilane as the precursor, hydrogen as the carrier gas, argon as the dilution gas, deposition temperature of 1000℃~1200℃, deposition pressure of 0.5~2.0kPa, and density of the undensified SiC / SiC composite preform of 1.7~2.1g / cm³. 3 .

[0015] As one possible implementation method, the precursor impregnation pyrolysis process conditions are as follows: the fiber preform after SiC matrix chemical vapor deposition is impregnated in a mixed solution of polycarbosilane and xylene for 8-12 hours, and then dried at 100-140℃; the dried fiber preform is pyrolyzed in nitrogen or argon at 1000-1200℃ for 1-3 hours; wherein the mass fraction of polycarbosilane in the mixed solution of polycarbosilane and xylene is 40%-60%.

[0016] One possible approach is to achieve demolding after densification of the SiC / SiC composite material, i.e., the density of the SiC / SiC composite material reaches 2.35–2.55 g / cm³. 3 Demolding later.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention proposes a densification molding method suitable for multi-configuration SiC / SiC composite materials. By designing the conformal surface of the mold, reserving thermal expansion compensation, opening through holes, designing external fixtures, and designing a modular structure, the technical contradiction of traditional molds being unable to balance structural stability and air / liquid permeability in gas-liquid combination processes is successfully solved.

[0018] 2. The invention proposes a densification molding method suitable for multi-configuration SiC / SiC composite materials. Through the modularization of the molding die and the synergistic effect of the external clamping constraint mechanism, not only is the dimensional accuracy and molding consistency of the component ensured during the high-temperature densification process, but the penetration efficiency of CVI and PIP processes is also significantly improved, and the densification cycle is shortened.

[0019] 3. The invention proposes a densification molding method suitable for multi-configuration SiC / SiC composite materials. The modular design of the molding die enhances the adaptability of the die to different configurations. While achieving high-quality component preparation, it effectively reduces the cost of the die and the complexity of the process, providing a practical solution for the efficient, low-cost, and high-precision manufacturing of multi-configuration SiC / SiC composite component materials.

[0020] 4. This invention proposes a densification molding method suitable for multi-configuration SiC / SiC composite materials. By optimizing the design of the molding die and combining specific process steps, the dimensional accuracy and surface quality of the components are improved, the densification cycle is shortened, and the manufacturing cost is reduced. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart illustrating the densification molding method for multi-configuration SiC / SiC composite materials according to the present invention. Figure 2 A schematic diagram of a mold for a densification molding method of SiC / SiC composite materials with gas-liquid combination process suitable for flat-plate structures is provided for Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of a mold for a densification molding method of SiC / SiC composite material with gas-liquid combination process for small cylindrical structure provided in Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of a mold for a densification molding method of SiC / SiC composite material gas-liquid combination process suitable for large-size cylindrical structure SiC / SiC composite material provided in Embodiment 3 of the present invention; Figure 5 This is a schematic diagram of a mold for a densification molding method for gas-liquid combination process of irregularly shaped SiC / SiC composite materials, as provided in Embodiment 4 of the present invention.

[0022] Figure label: 201-Modular assembly structure, 202-Locking structure, 203-Through hole, 204-External clamp; 301-Core mold, 302-Outer mold, 303-Through hole, 304-External clamp, 305-Locking structure; 401-Core mold, 402-Outer mold, 403-Through hole, 404-External clamp, 405-Positioning pin structure, 406-Locking structure; 501-Female mold, 502-Male mold, 503-Through hole, 504-External clamp, 505-Positioning pin structure, 506-Locking structure. Detailed Implementation

[0023] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0024] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0025] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0026] This invention aims to provide a densification molding method suitable for multi-configuration SiC / SiC composite materials. By optimizing the conformal surface design of the mold, reserving thermal expansion compensation, opening through holes, designing external fixtures, and designing a modular structure, combined with specific process steps, it solves the problem of balancing gas / liquid permeability and structural stability in the gas-liquid combination process. Optimizing the mold can effectively balance the gas / liquid permeability and structural stability of the mold, reduce the risk of deformation, and thus improve the dimensional accuracy and surface quality of the components. At the same time, it ensures uniform gas and liquid penetration, shortens the densification cycle, and reduces process costs.

[0027] This invention provides a densification molding method suitable for multi-configuration SiC / SiC composite materials, comprising the following steps: Configure a molding die, which includes multiple separable and combinable modules, including an outer mold and / or a core mold. The molding die has a profile that conforms to the surface morphology of the SiC / SiC composite component. The profile is reserved for thermal expansion compensation and through holes are opened on the profile according to preset parameters.

[0028] The molding die is a device used to define the shape of SiC / SiC composite material components; as an example, the material of the molding die is selected as high-purity graphite or isostatic graphite.

[0029] For example, the molding die adopts a modular design, which includes multiple modules such as male mold, female mold, core mold, and outer mold. Each module is equipped with a positioning structure, and the modules can be connected by a combination of bolt connection, tenon and mortise fit and pin positioning. The above design ensures assembly accuracy and rigidity while taking into account the convenience of mold assembly and disassembly and the dimensional stability under high temperature environment.

[0030] Among them, the outer mold and / or core mold refer to the external and / or internal structural components that constitute the molding die.

[0031] Here, the profile refers to the surface inside the molding die that corresponds to the surface morphology of the SiC / SiC composite component. As an example, the profile can be directly machined from the three-dimensional model of the component using methods such as milling and grinding; or it can be formed directly into a structure conforming to the shape of the component through casting or additive manufacturing technology.

[0032] Thermal expansion compensation refers to the dimensional allowance reserved to offset the dimensional changes of the molding die material at high temperatures. As an example, thermal expansion compensation can be simulated using finite element analysis software to perform reverse design.

[0033] A through-hole refers to a cavity created on a molded surface for the permeation of gaseous or liquid media. As an example, through-holes can be formed on the molded surface using methods such as drilling or laser drilling; they can also be formed using methods such as etching or waterjet cutting. As an example, the shape of a through-hole can be circular, rectangular, square, polygonal, or slit-shaped.

[0034] Specifically, the molding die is configured, comprising multiple separable and combinable modules, including an outer mold and / or a core mold. The modular design facilitates die assembly and disassembly. High-precision locating pins and grooves are installed on the mating surfaces of each module to ensure accurate alignment of the multiple die modules during assembly, effectively controlling the mold closing gap and preventing matrix material spillage or fiber damage during the process. Based on the three-dimensional digital model of the SiC / SiC composite component, a die surface conforming to its surface morphology is designed to ensure accurate replication of the component's geometry. The die surface is pre-designed for thermal expansion compensation to offset the potential thermal expansion of the molding die material during high-temperature densification. The dimensional changes that can occur are considered to ensure the dimensional accuracy of SiC / SiC composite components during the densification process. The thermal expansion compensation amount is determined according to the calculation formula, and the mold size is reduced in advance when processing the molding mold to offset the deformation caused by the thermal expansion of the graphite mold. This effectively avoids the problem of the component being too large due to the expansion of the mold, thereby ensuring the dimensional accuracy of the component. Through holes are opened on the surface according to preset parameters. Based on the gas transport dynamics of the CVI process and the liquid impregnation flow field characteristics of the PIP process, the number, diameter, distribution position and spatial orientation of the through holes are optimized to ensure that the gas precursor and liquid polymer can be uniformly and efficiently transported and permeated in the preform.

[0035] Compared with existing technologies, existing methods are limited to molding dies for specific configuration components and cannot balance the stability of the mold structure with air / liquid permeability. This solution can effectively improve the air / liquid permeability and stability of the mold, reduce the risk of deformation, and ensure uniform gas and liquid penetration by optimizing the design of the mold conformal surface, reserving thermal expansion compensation, opening through holes, and designing a modular structure.

[0036] Through the above technical solution, this application can meet the molding requirements of SiC / SiC composite material components with different configurations, and ensure the accuracy of the component geometry and dimensions.

[0037] As one possible implementation, the thickness of the forming mold in the area where the profile is located is greater than or equal to 10 mm and less than or equal to 30 mm.

[0038] The thickness of the molding die in the area where the profile is located refers to the local wall thickness of the area in the molding die that is directly conformal to the surface morphology of the SiC / SiC composite component. This thickness is a key parameter affecting the structural stability and gas / liquid permeation efficiency of the mold under high temperature conditions.

[0039] Specifically, the thickness of the molding die in the area containing the molded surface is limited to greater than or equal to 10 mm. This ensures that the molding die has sufficient structural rigidity and strength in the high-temperature environment during the densification process, preventing deformation of the die at high temperatures and thus guaranteeing the molding accuracy of the SiC / SiC composite material components. The thickness of the molding die in the area containing the molded surface is limited to less than or equal to 30 mm to optimize the transmission and penetration efficiency of gas and liquid. If the thickness is too thick, it will hinder the uniform penetration of gas and liquid, thereby reducing the densification efficiency and extending the process cycle to meet the densification requirements.

[0040] Compared to existing technologies, traditional molds cannot balance mold structural stability and gas / liquid permeability. This invention effectively resolves the contradiction between structural stability and gas / liquid transport efficiency during high-temperature densification by limiting the mold thickness in the molding area to a range of 10mm to 30mm.

[0041] Through the above technical solutions, the thickness of the molding die in the area where the surface is located is greater than or equal to 10 mm, which ensures the structural integrity of the die at high temperature and avoids the decrease in the dimensional accuracy of the component due to deformation; the thickness is less than or equal to 30 mm, which ensures uniform and smooth gas / liquid penetration and improves densification efficiency, thereby significantly improving the preparation quality and efficiency of SiC / SiC composite material components.

[0042] As one possible implementation method, the thermal expansion compensation amount is determined in the following way: ΔD = D0 × α × ΔT Where ΔD is the thermal expansion compensation amount, D0 is the thickness or diameter of the SiC / SiC composite component at room temperature, α is the thermal expansion coefficient of the molding die material, and ΔT is the difference between the highest temperature during the densification process and room temperature.

[0043] As one possible implementation, the volume of all through holes on the profile is 10% to 20% of the volume of the profile area.

[0044] The total volume of all through holes on the mold surface refers to the total volume of all holes on the mold surface designed to allow the permeation of gas precursors and liquid polymers. The volume of the profile region refers to the volume occupied by the profile portion in the molding die that conforms to the surface morphology of the SiC / SiC composite component.

[0045] Specifically, the volume ratio of all through-holes on the mold surface to the total volume of the mold surface area is 10%–20%. This ratio ensures that the gaseous precursor and liquid polymer can fully and uniformly penetrate into the fiber preform during SiC matrix chemical vapor deposition (CVI) and precursor impregnation pyrolysis (PIP) processes, thereby promoting an efficient densification process and shortening the densification cycle. Simultaneously, by limiting the total volume ratio of through-holes, a significant decrease in the mechanical strength of the mold under high-temperature deposition and pyrolysis conditions is avoided due to excessive openings, effectively suppressing mold deformation and ensuring the dimensional accuracy of the SiC / SiC composite components.

[0046] Through the above technical solution, the present invention can balance the stability of the mold structure and the efficiency of the densification process by using the design of through holes.

[0047] The fiber preform is installed and positioned in the cavity of the molding mold. The molding mold is locked with clamps. After the mold is locked, the fiber preform is shaped and then demolded.

[0048] The fiber preform is a porous structure made of woven or laid-up SiC fibers, serving as the skeleton of the SiC / SiC composite material. As an example, the fiber preform can employ a 2D, 2.5D, or 3D woven structure.

[0049] As one possible implementation, a clamp is used to lock the forming mold, and after the mold is locked, the fiber preform is shaped, including: The wet molding process involves installing and positioning the softened fiber preform into the cavity of the molding mold, applying pressure to make it adhere to the outer mold surface, closing the mold with bolts and / or tenon joints, locking it with clamps, and then placing the whole assembly into an oven for shaping.

[0050] Wet molding is a process that uses liquid to impregnate a fiber preform, softening and making it malleable so that it can maintain a specific shape after external force is applied. The purpose of wet molding is to reduce the rigidity of the fiber preform, making it easier to conform to the mold surface and allowing it to solidify and solidify after drying.

[0051] The process of impregnating and softening the fiber preform transforms the relatively rigid preform into a flexible and malleable one, enabling it to better adapt to the complex curvature of the mold surface and preventing poor adhesion caused by rigidity. As an example, the impregnation process can involve completely immersing the fiber preform in a solvent containing the binder, or applying an appropriate amount of impregnating agent evenly to the surface of the fiber preform to soften it locally or entirely. As an example, the impregnating agent can be water, alcohol solvents (such as ethanol and isopropanol), ketone solvents (such as acetone), or mixtures thereof.

[0052] Applying pressure to force the preform to adhere tightly to the outer mold surface aims to eliminate gaps between the preform and the mold, ensuring molding accuracy and uniform penetration during subsequent densification, and guaranteeing the dimensional accuracy and surface quality of the final component. As an example, pressure can be achieved through mechanical clamping, such as using pressure plates, airbags, or vacuum bags to compress the preform evenly against the mold surface; or by applying continuous, uniform pressure to the preform after the mold is closed, utilizing the mold's structural design (such as a wedge structure) or the clamping force of external fixtures.

[0053] The clamp, located outside the forming mold, is used to apply mechanical constraints and locking. By adjusting the bolts to apply preload, the clamp actively restrains and strengthens the overall structure of the mold, effectively suppressing expansion, warping, and other deformation caused by thermal stress under high-temperature processing conditions, thus ensuring the stability of the component's forming accuracy. As an example, the clamp can be a C-clamp, a quick-release clamp, or a custom-made ring clamp.

[0054] The mold is closed using bolts and / or mortise and tenon joints, and locked in place by clamps. These clamps apply uniform and controllable mechanical restraint to the outside of the mold to counteract the forces causing deformation due to thermal stress and material phase changes during the CVI high-temperature environment and PIP pyrolysis. This maintains the dimensional stability of the mold cavity throughout the entire process, ensuring the molding accuracy of the component. As an example, high-strength bolts can be used to close the mold through pre-designed bolt holes. The number and distribution of bolts should ensure uniform clamping force. The mortise and tenon joints can be designed with precision techniques, such as dovetail joints, straight tenons, or beveled tenons.

[0055] Specifically, a wet molding process is employed, in which the impregnated and softened fiber preform is installed and positioned in the cavity of the molding mold. Pressure is applied to ensure that the preform fully conforms to the outer mold surface, eliminating gaps between the preform and the mold, thereby ensuring the dimensional accuracy of the initial molded component. At the same time, the mold is closed by bolts and / or tenon joints and further locked by clamps, providing multiple and reliable external constraints for the mold. This effectively suppresses possible deformation of the mold during subsequent oven molding and high-temperature deposition and pyrolysis processes, ensuring the overall rigidity and dimensional stability of the mold.

[0056] Through the above technical solution, the present invention can effectively solve the problem of poor adhesion of fiber preforms in the mold cavity. Through a precise preforming and mold constraint mechanism, it provides a key guarantee for finally obtaining high-precision and high-performance SiC / SiC composite material components.

[0057] After the shaped fiber preform undergoes heat treatment to remove adhesive, a deposition layer is formed on the surface of the fiber preform to create a deposition interface layer.

[0058] The interface layer is a coating deposited on the surface of the fiber preform to improve the bond between the fiber and the matrix and to prevent damage to the fiber during densification. As an example, the interface layer can be formed on the surface of the fiber preform using a chemical vapor deposition (CVD) process.

[0059] As one possible approach, the shaped fiber preform undergoes heat treatment to remove adhesive, specifically: The shaped fiber preform is placed in a vacuum environment for heat treatment at a temperature of 500–800°C for 1–3 hours.

[0060] Among them, heat treatment degumming aims to remove organic binders or other volatile impurities that may be introduced during the preparation of fiber preforms. If these impurities are not removed, they will decompose and volatilize during the subsequent high-temperature densification process, which may form defects and pores during the deposition of the interface layer, or affect the bonding strength between the interface layer and the fiber, thereby reducing the performance of the composite material.

[0061] The process of heat-treating the fiber preform in a vacuum environment aims to utilize high temperatures to decompose and volatilize organic impurities. Simultaneously, the vacuum environment rapidly removes the decomposition products, preventing their redeposition inside or on the surface of the preform, and effectively isolates oxygen to prevent oxidative damage to the fibers at high temperatures. As an example, the preset pressure of the vacuum environment is set to 10... - 2 Below Pa.

[0062] The heat treatment temperature is 500–800°C. This temperature range is designed to ensure that most commonly used organic binders can be fully decomposed and volatilized, while avoiding excessively high temperatures that could cause thermal damage or structural changes to the SiC fibers themselves. As an example, the temperature is set to 800°C.

[0063] The heat treatment time is 1 to 3 hours. Within the set temperature range, sufficient time ensures that organic impurities are completely decomposed and escape from the fiber preform, avoiding residues. As an example, the time is set to 2 hours.

[0064] Specifically, the shaped fiber preform undergoes heat treatment in a vacuum environment to remove adhesive, followed by chemical vapor deposition (CVI) for interface layer deposition. The heat treatment temperature is set to 500–800°C for 1–3 hours, effectively decomposing and removing organic impurities from the interior and surface of the fiber preform. The vacuum environment effectively isolates external oxidation, protecting the fiber material while promoting the rapid escape of decomposition products. Appropriate temperature and time control ensures thorough removal of adhesives without damaging the fibers themselves. By eliminating these potential sources of contamination, the subsequent interface layer is uniformly and densely deposited on the clean fiber surface, significantly improving the bonding strength and integrity between the interface layer and the fiber. This lays a solid foundation for subsequent SiC matrix deposition, ultimately contributing to improved overall performance and densification of the SiC / SiC composite material.

[0065] By introducing a heat treatment degumming step before depositing the interface layer on the surface of the fiber preform, this application effectively solves the problem that residual adhesive or other impurities in the fiber preform may cause uneven interface layer deposition, weakened adhesion, or defects in the subsequent high-temperature deposition environment.

[0066] As one possible implementation, the interface layer is a pyrolytic carbon interface layer, a boron nitride interface layer, a silicon carbide interface layer, or a multiphase interface layer.

[0067] The prefabricated fiber surface deposition interface layer is designed to protect the fibers and promote matrix deposition. Among them, the pyrolytic carbon interface layer refers to the carbon layer formed on the fiber surface through the pyrolytic carbon process; this carbon layer usually has a layered structure, which can provide a weak interface, which is conducive to crack deflection, thereby improving the toughness of the material; as an example, the pyrolytic carbon interface layer is deposited by chemical vapor deposition (CVI) using hydrocarbon gases (such as methane and propane) at high temperature.

[0068] Among them, the boron nitride interface layer refers to the boron nitride (BN) ceramic layer deposited on the fiber surface. Boron nitride has excellent high-temperature stability, chemical inertness and low shear strength, which can effectively protect the fiber from chemical erosion and mechanical damage during the matrix deposition process and provide crack deflection paths. As an example, the boron nitride interface layer can be deposited by chemical vapor deposition using boron-containing and nitrogen-containing gases (such as boron trichloride and ammonia) at high temperature.

[0069] Among them, the silicon carbide interface layer refers to the silicon carbide (SiC) ceramic layer deposited on the fiber surface. Silicon carbide and SiC matrix have good chemical compatibility, which can form a strong bonding interface, promote effective load transfer, and act as a diffusion barrier layer. As an example, the silicon carbide interface layer can be deposited by chemical vapor deposition using silicon-containing and carbon-containing gases (such as methyltrichlorosilane) at high temperature.

[0070] Among them, a multiphase interface layer refers to an interface layer composed of two or more different materials or structures. Such an interface layer aims to combine the advantages of different materials to achieve better overall performance. As an example, a multiphase interface layer can be formed by first depositing a layer of boron nitride and then depositing a layer of silicon carbide to form a multilayer structure.

[0071] Specifically, pyrolytic carbon interfacial layers, with their excellent lubricity and interfacial compatibility, can reduce mechanical damage to fibers during deposition and improve the uniform adhesion of the substrate material. Boron nitride interfacial layers, utilizing their high-temperature stability and low coefficient of friction, maintain the integrity of the interfacial structure in high-temperature deposition environments, effectively preventing defects caused by thermal stress. Silicon carbide interfacial layers, based on their similarity to the SiC substrate, can strengthen the interfacial bonding strength and prevent debonding between the deposited layer and fibers. Multiphase interfacial layers, by integrating the advantages of multiple materials, provide a more adaptable interfacial solution, optimizing performance for different process conditions and comprehensively addressing the deposition inhomogeneity or defect problems that may be caused by a single material.

[0072] Through the above technical solutions, this invention can effectively solve the deposition quality problems and defects that may be caused by improper selection of interface layer materials by selecting pyrolytic carbon interface layer, boron nitride interface layer, silicon carbide interface layer or multiphase interface layer, ensuring effective protection of fibers during SiC matrix chemical vapor deposition, promoting good bonding between matrix and fibers, and thus significantly improving the overall performance and reliability of SiC / SiC composite components.

[0073] A fiber preform with a deposition interface layer is loaded into a molding mold and placed in a deposition environment for SiC matrix chemical vapor deposition. Subsequently, a precursor impregnation pyrolysis process is performed to achieve densification of the SiC / SiC composite material before demolding to obtain a SiC / SiC composite material blank.

[0074] Among them, SiC matrix chemical vapor deposition is a process of forming SiC matrix in the pores of fiber preform through chemical vapor deposition (CVI) process; Among them, the precursor impregnation and pyrolysis process is a process of forming SiC matrix in the pores of fiber preform through liquid polymer impregnation and thermal pyrolysis.

[0075] Specifically, a fiber preform with a deposition interface layer is loaded into a molding die and placed in a chemical vapor deposition furnace to deposit a SiC matrix using a chemical vapor infiltration (CVI) process. After the matrix is ​​deposited, a precursor impregnation pyrolysis (PIP) process is used to densify the composite material matrix. After one impregnation pyrolysis is completed, the operation is repeated until the composite material is densified.

[0076] As one possible implementation, the deposition conditions for the SiC matrix are as follows: trichloromethylsilane as the precursor, hydrogen as the carrier gas, argon as the dilution gas, deposition temperature of 1000–1200℃, deposition pressure of 0.5–2.0 kPa, and the density of the undensified SiC / SiC composite preform of 1.7–2.1 g / cm³. 3 .

[0077] Trichloromethylsilane serves as a precursor, acting as both the silicon and carbon source for SiC. It is deposited on the surface and interior of the fiber preform through a thermal decomposition reaction to form the SiC matrix. As an example, a mixture of silicon tetrachloride and hydrocarbons (such as methane and propane) can be used as the SiC precursor.

[0078] Hydrogen, as the carrier gas, primarily transports the gaseous precursor from the supply source to the deposition reactor and acts as a reducing agent to participate in or promote the deposition reaction. As an example, inert gases such as helium, nitrogen, or argon can be used as carrier gases.

[0079] Argon is used as a diluent gas to regulate the concentration of reactant gases, prevent excessively rapid reaction rates from causing surface blockage or uneven deposition, and contribute to the uniform distribution of gases within complex structures. As an example, nitrogen or helium can be used as diluent gases.

[0080] The deposition temperature is 1000–1200℃, which provides sufficient energy to decompose the precursor molecules and induce a chemical reaction, forming high-quality SiC crystals while balancing the reaction rate with the material's thermal stability. As an example, the deposition temperature can also be adjusted to 900℃ or 1300℃ depending on specific requirements.

[0081] The deposition pressure ranges from 0.5 to 2.0 kPa. This pressure range optimizes the mean free path and diffusion rate of gas molecules, thereby controlling the penetration depth and deposition uniformity of the precursor within the fiber preform and effectively reducing surface clogging. As an example, the deposition pressure can be adjusted according to the reactor design, precursor flow rate, and desired deposition rate, for example, down to 0.1 kPa.

[0082] The density of the undensified SiC / SiC composite preform is 1.7–2.1 g / cm³. 3This density range ensures that a sufficient initial SiC matrix framework is constructed in the fiber preform while maintaining appropriate porosity so that the liquid precursor in the subsequent precursor impregnation and pyrolysis process can effectively penetrate and fill.

[0083] Specifically, using trichloromethylsilane as a precursor ensured the high purity and controllability of SiC matrix formation, avoiding the adverse effects of impurities on subsequent densification. Using hydrogen as a carrier gas promoted the transport and diffusion of the precursor within the through-holes of the molding die, enhancing gas permeability and synergizing with the die's through-hole design. Introducing argon as a dilution gas effectively regulated the concentration of the reaction environment, preventing pore blockage caused by excessively rapid deposition rates, thus ensuring uniform deposition. Controlling the deposition temperature between 1000 and 1200°C balanced the thermal reaction rate with the material's thermal stability, reducing the risk of high-temperature deformation and guaranteeing the quality of the SiC matrix. Setting the deposition pressure between 0.5 and 2.0 kPa optimized gas flow dynamics, ensuring the precursor could uniformly penetrate into the fiber preform, reducing surface blockage and increasing penetration depth. Furthermore, by controlling the density of the undensified SiC / SiC composite preform between 1.7 and 2.1 g / cm³, the deposition process was optimized. 3 This maintained the suitable porous structure of the initial framework, providing sufficient permeation space for the subsequent precursor impregnation and pyrolysis process, ensuring the effective filling of the liquid precursor, and thus achieving good synergy between chemical vapor deposition and precursor impregnation and pyrolysis processes.

[0084] Through the above technical solution, this application effectively solves the problems of low efficiency and uneven matrix quality that may occur during the deposition process by precisely limiting the process parameters of chemical vapor deposition of SiC matrix, ensuring the high efficiency and uniformity of the deposition process, laying an optimized foundation for subsequent process steps, and significantly improving the overall densification efficiency and component quality stability of SiC / SiC composite materials.

[0085] As one possible implementation method, the precursor impregnation pyrolysis process conditions are as follows: the fiber preform after SiC matrix chemical vapor deposition is impregnated in a mixed solution of polycarbosilane and xylene for 8-12 hours, and then dried at 100-140℃; the dried fiber preform is pyrolyzed in nitrogen or argon at 1000-1200℃ for 1-3 hours; wherein the mass fraction of polycarbosilane in the mixed solution of polycarbosilane and xylene is 40%-60%.

[0086] The impregnation process aims to ensure that the liquid polymer precursor fully penetrates into the micropores inside the fiber preform after chemical vapor deposition on the SiC matrix. An impregnation time of 8–12 hours ensures that the precursor solution has sufficient time to penetrate the deep structure of the preform through capillary action and diffusion, thereby achieving effective pore filling. As an example, vacuuming the preform before impregnation removes gas from the pores, facilitating rapid solution filling. As another example, for preforms with low porosity, small pore size, or solutions with high viscosity, the impregnation time can be extended to ensure sufficient penetration.

[0087] The drying process aims to remove xylene, a solvent introduced during impregnation. Maintaining the drying temperature between 100 and 140°C effectively promotes xylene volatilization, preventing solvent residue from affecting subsequent pyrolysis conversion efficiency and product quality. As an example, oven drying, vacuum drying, or reduced-pressure drying can be used to accelerate solvent removal.

[0088] The pyrolysis process aims to convert the dried polycarbosilane precursor into the SiC matrix. Pyrolysis in an inert atmosphere such as nitrogen or argon effectively prevents oxidation of the precursor at high temperatures, ensuring the purity and yield of SiC. A pyrolysis temperature of 1000–1200℃ is suitable for the conversion of polycarbosilane to SiC, while a pyrolysis time of 1–3 hours ensures complete conversion of the precursor. As an example, pyrolysis can be performed in a helium or vacuum environment; as another example, the pyrolysis process can employ single-step or multi-step heating pyrolysis, optimizing the precursor conversion efficiency and the microstructure of the SiC matrix by controlling the heating rate and holding time.

[0089] In this process, the mass fraction of polycarbosilane in the xylene mixed solution is controlled between 40% and 60% to optimize the viscosity and permeability of the precursor solution. As an example, toluene, hexane, or other solvents can be used to dissolve the polycarbosilane.

[0090] Specifically, immersion in a mixed solution of polycarbosilane and xylene for 8–12 hours ensures sufficient time for the precursor to fully penetrate the micropores of the fiber preform, effectively avoiding inadequate pore filling due to insufficient impregnation. Drying at 100–140°C efficiently and gently removes the xylene solvent, preventing solvent residue from affecting subsequent pyrolysis and avoiding premature decomposition or polymerization of the precursor due to excessively high temperatures. Pyrolysis at 1000–1200°C for 1–3 hours in nitrogen or argon provides an inert and suitable conversion environment, ensuring efficient and complete conversion of polycarbosilane into the SiC matrix, avoiding material defects caused by incomplete pyrolysis or oxidation. Furthermore, a mixed solution with a polycarbosilane mass fraction of 40%–60% optimizes the viscosity and flowability of the precursor solution, enabling it to effectively penetrate micropores while ensuring sufficient solids content is introduced with each impregnation, thus balancing penetration efficiency and densification efficiency.

[0091] Through the above technical solution, the present invention enables the precursor impregnation pyrolysis process to achieve efficient and uniform pore filling and matrix transformation by precisely defining the key parameters of the precursor impregnation pyrolysis process. This significantly improves the densification efficiency and final material quality of SiC / SiC composite materials, effectively solves problems such as insufficient penetration, uneven drying and incomplete pyrolysis caused by non-optimized process conditions, thereby shortening the overall process cycle and reducing production costs.

[0092] One possible approach is to achieve demolding after densification of the SiC / SiC composite material, i.e., the density of the SiC / SiC composite material reaches 2.35–2.55 g / cm³. 3 Demolding later.

[0093] The density range of SiC / SiC composite materials is a key indicator for judging the degree of densification. Reaching this density range means that the internal pores of the material have been effectively filled, the matrix has been fully deposited, and the mechanical properties and structural integrity of the material have reached the expected level. As an example, the Archimedes' displacement method can be used to calculate the density by measuring the volume and mass of the blank, and samples can be taken periodically during the densification process until the density reaches the target range. As another example, non-destructive testing techniques such as X-ray computed tomography (CT) or ultrasonic testing can be used to monitor the degree of densification inside the blank in real time or near real time, and determine whether the target density range has been reached based on a preset density-signal correlation model. As yet another example, the current density can be estimated by monitoring the mass gain of the blank during densification, combining its initial density and theoretical density; when the mass gain reaches a preset value, the density is considered to have reached the target range.

[0094] Demolding refers to the process of separating the densified SiC / SiC composite material blank from the molding die. As an example, this can be done after the die has cooled to room temperature. The blank can be removed from the die by disassembling the clamps, separating the die modules, or by using auxiliary methods such as vibration, gentle tapping, or the use of a release agent.

[0095] Specifically, a specific density range of 2.35–2.55 g / cm³ is set. 3 This ensures that when the SiC / SiC composite material is removed from the mold, its internal pores are fully filled, the matrix structure is intact, and the mechanical properties meet expectations. This avoids problems such as insufficient densification and strength defects caused by premature demolding, or prolonged process cycle and increased energy consumption caused by delayed demolding.

[0096] Through the above technical solution, the demolding operation is synchronized with the specific density range of the SiC / SiC composite preform (2.35~2.55g / cm³). 3 With precise correlation, this application effectively solves the problem of inaccurate demolding timing during densification, ensuring the quality stability and reliability of the final SiC / SiC composite component.

[0097] Machining of SiC / SiC composite blanks to obtain SiC / SiC composite components.

[0098] To facilitate understanding of the technical solution of this application, further explanation is provided below with reference to specific embodiments.

[0099] Example 1 A gas-liquid combined process for densification molding of SiC / SiC composite materials with flat panel structures is proposed. The molding die configuration is described in [reference needed]. Figure 2 .

[0100] (1) Molding mold assembly module design: The molding mold adopts a "sandwich" modular assembly structure 201, and each mold can be used to prepare two flat components. Locking structures 202 are set on the joint surfaces of each module to ensure the stability of the fit.

[0101] (2) Molding mold surface design: Based on the three-dimensional digital model of the SiC / SiC composite flat plate component, a mold surface conforming to its surface morphology is designed. High-purity graphite is selected as the mold material, and the thickness of the molding mold in the area of ​​the mold surface is set to 10 mm. The allowable thermal expansion compensation for the mold surface is determined by ΔD = D0 × α × ΔT, where D0 = 10 mm and α = 2.8 × 10 -6 / ℃, ΔT=1180℃, the calculated thermal expansion compensation ΔD is 0.03mm. Given the extremely small thermal expansion, no thermal expansion compensation is reserved on the mold surface in this embodiment. The mold surface is designed with a perpendicular line to the mold surface. A 4 mm through-hole (203) is incorporated to meet the requirements of airflow vertical transmission along the flat plate in the CVI process and the shortest path impregnation of liquid in the PIP process. The volume ratio of the through-hole to the surface area is 20%, balancing penetration efficiency and mold structural strength.

[0102] (3) Molding mold clamping design: The external clamp 204 of the molding mold is designed as a long strip structure with a protrusion in the middle, which matches the groove at the center line of the molding mold.

[0103] (4) Fiber preform assembly and molding: A wet molding process is adopted, in which the fiber preform is impregnated and softened with deionized water. The impregnated and softened fiber preform is installed and positioned in the cavity of the molding mold, and pressure is applied to ensure that it fully fits the mold surface, ensuring that the fiber orientation is correct and undamaged. The mold is closed by bolts and / or tenon joints and locked by clamps. The clamp protrusions apply uniform mechanical constraint force, which effectively suppresses the mold deformation caused by thermal stress and material phase change during the CVI and PIP processes, ensuring the stability of the cavity dimensions and thus ensuring the dimensional accuracy of the component. The assembled graphite mold is placed in an oven for molding treatment, and then demolded after molding.

[0104] (5) Densification molding of flat plate components using gas-liquid combination process: The shaped fiber preform is heat-treated at 800℃ under vacuum for 2 h to remove adhesive; then it is placed in a chemical vapor deposition furnace, and a boron nitride interface layer is deposited using the CVI process. The precursors are boron trichloride and ammonia, the carrier gas is hydrogen, the dilution gas is argon, the carrier gas flow rate is 4 L / min, the dilution gas flow rate is 12 L / h, the deposition temperature is 900℃, the heating rate is 10℃ / min, the deposition pressure is 0.2 kPa, and the deposition time is 30 h; the fiber preform with the deposited boron nitride interface layer is placed in a chemical vapor deposition furnace and SiC matrix is ​​deposited using the CVI process until the density of the SiC / SiC composite material reaches 2.0 g / cm³. 3 The precursor was trichloromethylsilane, the carrier gas was hydrogen, and the dilution gas was argon. The carrier gas flow rate was 15 L / h, the dilution gas flow rate was 16 L / h, the deposition temperature was 1100℃, the heating rate was 10℃ / min, the deposition pressure was 0.2 kPa, and the deposition time was 130 h. A mixed solution of polycarbosilane and xylene (polycarbosilane mass fraction 50%) was used to impregnate the surface-deposited SiC matrix fiber preform under vacuum for 10 h. After impregnation, it was dried at 120℃, and then pyrolyzed at 1200℃ for 2 h under nitrogen protection. This "impregnation-pyrolysis" cycle was repeated 9 times until the density of the SiC / SiC composite material reached 2.55 g / cm³. 3 Demolding yields a SiC / SiC composite material blank.

[0105] Machining of SiC / SiC composite blanks to obtain SiC / SiC composite components.

[0106] Example 2 A gas-liquid combined process for densification molding of SiC / SiC composite materials for small-sized cylindrical structures is described in the attached diagram. Figure 3 .

[0107] (1) Molding mold assembly module design: The molding mold consists of a core mold 301 and an outer mold 302. The core mold is an integral mold, and the outer mold is a segmented mold, which is divided into two segments. The segmented modules are precisely positioned and assembled with each other through mortise and tenon structure.

[0108] (2) Molding mold surface design: Based on the three-dimensional digital model of the small-sized cylindrical component of SiC / SiC composite material, a mold surface conforming to its surface morphology is designed. High-purity graphite is selected as the mold material, and the thickness of the molding mold in the area where the surface is located is set to 10 mm. The allowable thermal expansion compensation for the surface is determined by ΔD=D0×α×ΔT, where D0=60mm and α=2.8×10 -6 At a temperature of 1180℃, ΔT = 1180℃, the calculated thermal expansion compensation ΔD is 0.2mm. Based on this, the diameters of both the core mold and the outer mold are reduced inward by 0.1mm. This design effectively offsets the impact of mold thermal expansion on component dimensions at high temperatures, ensuring the final molding accuracy of the entire ring component. A design perpendicular to the mold surface is incorporated into the profile. A 4 mm through-hole (303) is used to meet the requirements of radial airflow along the component in the CVI process and shortest path liquid impregnation in the PIP process. The volume ratio of the through-hole to the surface area is 15%, balancing penetration efficiency and mold structural strength.

[0109] (3) Molding mold clamping design: The external clamps 304 of the molding mold are designed as a ring structure, arranged in pairs at both ends. The external clamps are locked by the locking structure 305 to ensure the stability of the fit.

[0110] (4) Fiber preform assembly and molding: A wet molding process is adopted, in which the fiber preform is impregnated and softened with deionized water. The impregnated and softened fiber preform is installed and positioned in the cavity of the molding mold. Pressure is applied to ensure that it fully fits the mold surface, ensuring that the fiber orientation is correct and undamaged. The mold is closed by bolts and / or tenon joints and locked by clamps. Specifically, two annular clamps are respectively fitted on the top and bottom of the outside of the mold, and the two are tightened and fixed by applying preload with bolts, thereby forming a uniform circumferential constraint on the overall mold structure. This effectively suppresses the mold deformation caused by thermal stress and material phase change during the CVI and PIP processes, ensuring the stability of the cavity dimensions and thus ensuring the dimensional accuracy of the component. The assembled graphite mold is placed in an oven for molding treatment, and then demolded after molding.

[0111] (5) Densification of small-sized cylindrical components using a gas-liquid combination process: The shaped fiber preform is heat-treated at 800℃ under vacuum for 2 hours to remove adhesive; then it is placed in a chemical vapor deposition furnace, and a boron nitride interface layer is deposited using the CVI process. The precursors are boron trichloride and ammonia, the carrier gas is hydrogen, the dilution gas is argon, the carrier gas flow rate is 4L / min, the dilution gas flow rate is 12L / h, the deposition temperature is 900℃, the heating rate is 10℃ / min, the deposition pressure is 0.2kPa, and the deposition time is 30h; the fiber preform with the deposited boron nitride interface layer is placed in a chemical vapor deposition furnace and SiC matrix is ​​deposited using the CVI process until the density of the SiC / SiC composite material reaches 2.0 g / cm³. 3 The precursor was trichloromethylsilane, the carrier gas was hydrogen, and the dilution gas was argon. The carrier gas flow rate was 15 L / h, the dilution gas flow rate was 16 L / h, the deposition temperature was 1100℃, the heating rate was 10℃ / min, the deposition pressure was 0.2 kPa, and the deposition time was 130 h. A mixed solution of polycarbosilane and xylene (polycarbosilane mass fraction 50%) was used to impregnate the surface-deposited SiC matrix fiber preform under vacuum for 10 h. After impregnation, it was dried at 120℃, and then pyrolyzed at 1200℃ for 2 h under nitrogen protection. This "impregnation-pyrolysis" cycle was repeated 9 times until the density of the SiC / SiC composite material reached 2.50 g / cm³. 3 Demolding yields a SiC / SiC composite material blank.

[0112] Machining of SiC / SiC composite blanks to obtain SiC / SiC composite components.

[0113] Example 3 A gas-liquid combined process for densification molding of SiC / SiC composite materials suitable for large-size cylindrical structures is described in the following section. The molding die configuration is as follows: Figure 4 .

[0114] (1) Molding mold assembly module design: The molding mold consists of a core mold 401 and an outer mold 402. The core mold is an integral mold, and the outer mold is a segmented mold, which is divided into four segments. The segmented modules are precisely positioned and reliably assembled with each other through a positioning pin structure 405 and a locking structure 406.

[0115] (2) Molding mold surface design: Based on the three-dimensional digital model of the large-size cylindrical component of SiC / SiC composite material, a mold surface conforming to its surface morphology is designed. High-purity graphite is selected as the mold material, and the thickness of the molding mold in the area where the surface is located is set to 15 mm. The allowable thermal expansion compensation for the surface is determined by ΔD=D0×α×ΔT, where D0=350mm and α=2.8×10 -6 At a temperature of 1180℃, ΔT = 1180℃, the calculated thermal expansion compensation ΔD is 0.58mm. Based on this, the diameters of both the core mold and the outer mold are reduced inward by 0.29mm. This design effectively offsets the impact of mold thermal expansion on component dimensions at high temperatures, ensuring the final molding accuracy of the entire ring component. A design perpendicular to the mold surface is incorporated into the profile. The 6 mm through-holes (403) meet the requirements of radial airflow along the component in the CVI process and the shortest path impregnation of liquid in the PIP process. The volume ratio of the through-holes to the surface area is 15%, balancing penetration efficiency and mold structural strength.

[0116] (3) Molding mold clamping design: The external clamp 404 of the molding mold is designed as an arc-shaped clamp structure.

[0117] (4) Fiber preform assembly and molding: A wet molding process is adopted, in which the fiber preform is soaked and softened with deionized water. The soaked and softened fiber preform is installed and positioned in the cavity of the molding mold. Pressure is applied to ensure that it fully fits the mold surface, ensuring that the fiber orientation is correct and undamaged. The mold is closed by bolts and / or tenon joints and locked by clamps. Specifically, the bow-shaped clamps are clamped at the corresponding positions of the core mold and the outer mold. Through the mechanical constraint, the mold deformation caused by thermal stress and material phase change during the CVI and PIP processes is effectively suppressed, ensuring the stability of the cavity dimensions and thus ensuring the dimensional accuracy of the component. The assembled graphite mold is placed in an oven for molding treatment, and then demolded after molding.

[0118] (5) Densification of large-size cylindrical components using a gas-liquid combination process: The shaped fiber preform is heat-treated at 800℃ under vacuum for 2 hours to remove adhesive; then it is placed in a chemical vapor deposition furnace, and a boron nitride interface layer is deposited using the CVI process. The precursors are boron trichloride and ammonia, the carrier gas is hydrogen, the dilution gas is argon, the carrier gas flow rate is 4L / min, the dilution gas flow rate is 12L / h, the deposition temperature is 900℃, the heating rate is 10℃ / min, the deposition pressure is 0.2kPa, and the deposition time is 30h; the fiber preform with the deposited boron nitride interface layer is placed in a chemical vapor deposition furnace and SiC matrix is ​​deposited using the CVI process until the density of the SiC / SiC composite material reaches 2.0 g / cm³. 3 The precursor was trichloromethylsilane, the carrier gas was hydrogen, and the dilution gas was argon. The carrier gas flow rate was 15 L / h, the dilution gas flow rate was 16 L / h, the deposition temperature was 1100℃, the heating rate was 10℃ / min, the deposition pressure was 0.2 kPa, and the deposition time was 130 h. A mixed solution of polycarbosilane and xylene (polycarbosilane mass fraction 50%) was used to impregnate the surface-deposited SiC matrix fiber preform under vacuum for 10 h. After impregnation, it was dried at 120℃, and then pyrolyzed at 1200℃ for 2 h under nitrogen protection. This "impregnation-pyrolysis" cycle was repeated 9 times until the density of the SiC / SiC composite material reached 2.52 g / cm³. 3 Demolding yields a SiC / SiC composite material blank.

[0119] Machining of SiC / SiC composite blanks to obtain SiC / SiC composite components.

[0120] Example 4 A gas-liquid combined process for densification molding of irregularly shaped SiC / SiC composite materials is proposed, with the molding die described below. Figure 5 .

[0121] (1) Molding mold assembly module design: The molding mold consists of two modules, male mold 502 and female mold 501. The modules are precisely positioned with each other through the positioning pin structure 505.

[0122] (2) Molding mold surface design: Based on the three-dimensional digital model of the irregular structure of SiC / SiC composite material, a mold surface conforming to its surface morphology is designed. High-purity graphite is selected as the mold material, and the thickness of the molding mold in the area where the surface is located is set to 15 mm. The allowable thermal expansion compensation for the surface is determined by ΔD=D0×α×ΔT, where D0=15mm and α=2.8×10 -6 / ℃, ΔT=1180℃, and the calculated ΔD is 0.05mm. Given the extremely small amount of thermal expansion, no thermal expansion compensation is reserved on the mold surface in this embodiment. The mold surface is designed with a perpendicular line to the mold surface. The 6 mm through-hole 503 is designed to meet the requirements of airflow vertical transmission along the plate in the CVI process and the shortest path impregnation of liquid in the PIP process. The volume ratio of the through-hole to the surface area is 10%, balancing penetration efficiency and mold structural strength.

[0123] (3) Molding mold clamping design: The external clamps 504 of the molding mold are designed as C-shaped structures and are arranged in pairs on both sides of the male mold and the female mold. The external clamps are locked by the locking structure 506 to ensure the stability of the fit.

[0124] (4) Fiber preform assembly and molding: A wet molding process is adopted, in which the fiber preform is soaked and softened with deionized water. The soaked and softened fiber preform is installed and positioned in the cavity of the molding mold. Pressure is applied to ensure that it fully fits the mold surface, ensuring that the fiber orientation is correct and undamaged. The mold is closed by bolts and / or tenon joints and locked by clamps. Specifically, two sets of C-shaped clamps are clamped at corresponding positions on the outside of the male and female molds, and the bolts are used to apply pre-tightening force to achieve fastening. This effectively suppresses the mold deformation caused by thermal stress and material phase change during the CVI and PIP processes, ensuring the stability of the cavity dimensions and thus ensuring the dimensional accuracy of the component. The assembled graphite mold is placed in an oven for molding treatment, and then demolded after molding.

[0125] (5) Densification molding of irregularly shaped components using gas-liquid combination process: The shaped fiber preform is heat-treated at 800℃ under vacuum for 2 hours to remove adhesive; then it is placed in a chemical vapor deposition furnace, and a boron nitride interface layer is deposited using the CVI process. The precursors are boron trichloride and ammonia, the carrier gas is hydrogen, the dilution gas is argon, the carrier gas flow rate is 4L / min, the dilution gas flow rate is 12L / h, the deposition temperature is 900℃, the heating rate is 10℃ / min, the deposition pressure is 0.2kPa, and the deposition time is 30h; the fiber preform with the deposited boron nitride interface layer is placed in a chemical vapor deposition furnace and SiC matrix is ​​deposited using the CVI process until the density of the SiC / SiC composite material reaches 2.0 g / cm³. 3 The precursor was trichloromethylsilane, the carrier gas was hydrogen, and the dilution gas was argon. The carrier gas flow rate was 15 L / h, and the dilution gas flow rate was 16 L / h. The deposition temperature was 1100℃, the heating rate was 10℃ / min, the deposition pressure was 0.2 kPa, and the deposition time was 130 h. A mixed solution of polycarbosilane and xylene (polycarbosilane mass fraction 50%) was used to impregnate the surface-deposited SiC matrix fiber preform under vacuum for 10 h. After impregnation, it was dried at 120℃ and then pyrolyzed at 1200℃ for 2 h under nitrogen protection. This "impregnation-pyrolysis" cycle was repeated 9 times until the density of the SiC / SiC composite material reached 2.53 g / cm³. 3 Demolding yields a SiC / SiC composite material blank.

[0126] Machining of SiC / SiC composite blanks to obtain SiC / SiC composite components.

[0127] This invention, through modular molding die design, combined with thermal expansion compensation and through-hole optimization, and densification under external fixture constraints, effectively resolves the contradiction between mold permeability / liquidity and high-temperature structural stability during the densification process of SiC / SiC composite materials. It enables efficient synergy between CVI and PIP processes. This ensures the molding accuracy of the components while improving densification efficiency and reducing process costs, making it suitable for the fabrication of SiC / SiC composite components with various complex configurations.

[0128] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and other materials. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0129] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A densification molding method suitable for multi-configuration SiC / SiC composite materials, characterized in that, Includes the following steps: Configure a molding die, which includes multiple separable and combinable modules, including an outer mold and / or a core mold. The molding die has a profile that conforms to the surface morphology of the SiC / SiC composite component. The profile is reserved for thermal expansion compensation and through holes are opened on the profile according to preset parameters. The fiber preform is installed and positioned in the cavity of the molding mold, and the molding mold is locked with clamps. After the mold is locked, the fiber preform is shaped and then demolded. After the shaped fiber preform undergoes heat treatment to remove adhesive, a deposition layer is formed on the surface of the fiber preform to create a deposition interface layer. A fiber preform with a deposition interface layer is loaded into a molding mold and placed in a deposition environment for SiC matrix chemical vapor deposition. Then, a precursor impregnation and pyrolysis process is performed to achieve densification of the SiC / SiC composite material before demolding to obtain a SiC / SiC composite material blank. Machining of SiC / SiC composite blanks to obtain SiC / SiC composite components.

2. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The thickness of the forming mold in the area of ​​the profile is greater than or equal to 10mm and less than or equal to 30mm.

3. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The thermal expansion compensation amount is determined as follows: ΔD=D0×α×ΔT Where ΔD is the thermal expansion compensation amount, D0 is the thickness or diameter of the SiC / SiC composite component at room temperature, α is the thermal expansion coefficient of the molding die material, and ΔT is the difference between the highest temperature during the densification process and room temperature.

4. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The volume of all through holes on the surface is 10% to 20% of the volume of the surface area.

5. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The molding die is locked using clamps, and the fiber preform is shaped after the die is installed and locked. This includes: The wet molding process involves installing and positioning the softened fiber preform into the cavity of the molding mold, applying pressure to make it adhere to the outer mold surface, closing the mold with bolts and / or tenon joints, locking it with clamps, and then placing the whole assembly into an oven for shaping.

6. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The shaped fiber preform undergoes heat treatment to remove adhesive, specifically as follows: The shaped fiber preform is placed in a vacuum environment for heat treatment at a temperature of 500–800°C for 1–3 hours.

7. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The interface layer is a pyrolytic carbon interface layer, a boron nitride interface layer, a silicon carbide interface layer, or a multiphase interface layer.

8. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The conditions for chemical vapor deposition (CVD) of the SiC matrix were as follows: trichloromethylsilane as the precursor, hydrogen as the carrier gas, argon as the dilution gas, deposition temperature of 1000–1200℃, deposition pressure of 0.5–2.0 kPa, and density of the undensified SiC / SiC composite preform of 1.7–2.1 g / cm³. 3 .

9. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, The precursor impregnation and pyrolysis process conditions are as follows: the fiber preform after SiC matrix chemical vapor deposition is impregnated in a mixed solution of polycarbosilane and xylene for 8-12 hours, and then dried at 100-140℃; the dried fiber preform is pyrolyzed in nitrogen or argon at 1000-1200℃ for 1-3 hours; wherein the mass fraction of polycarbosilane in the mixed solution of polycarbosilane and xylene is 40%-60%.

10. The densification molding method for multi-configuration SiC / SiC composite materials according to claim 1, characterized in that, Achieving demolding after densification of SiC / SiC composite materials, i.e., achieving a density of 2.35–2.55 g / cm³ for the SiC / SiC composite material. 3 Demolding later.

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