A method for brazing fiber-reinforced composite materials or ceramics with metals using a hollow mesh flexible carbon sponge transition layer

Abstract

The present invention discloses a method for using a hollow mesh flexible carbon sponge transition layer to assist in the brazing of fiber-reinforced composite materials or ceramics with metals. The present invention utilizes vacuum rapid carbonization to treat melamine formaldehyde resin foam to obtain a carbon sponge material with a low thermal expansion coefficient, high mechanical flexibility, and a hollow network structure. During the brazing process using the carbon sponge material as a transition layer, the liquid solder will spontaneously perform capillary infiltration on the carbon sponge and completely fill it, forming an in-situ composite core-sheath structure in which a continuous network of carbon sponge (shell) wraps the solder alloy (core). This structure combines the advantages of the carbon sponge material's low thermal expansion coefficient, high elastic strain energy, and good plasticity of the metal material, giving the transition layer an overall excellent plastic toughness. This method can effectively improve the interface structure, increase the plastic toughness of the brazing seam, and reduce the thermal expansion coefficient of the brazing seam, significantly improving the mechanical properties of the fiber-reinforced composite material or ceramic and metal joints.

Description

Technical Field

[0001] The invention belongs to the technical field of porous material preparation and welding, and relates to a method for brazing a hollow mesh flexible carbon sponge transition layer assisted fiber reinforced composite material or ceramic with metal. Background Art

[0002] Fiber reinforced composite materials or ceramics have the characteristics of high specific strength, ablation resistance and high temperature resistance, and are widely used in the fields of automobile manufacturing, aerospace, electronic packaging, etc. However, the plasticity and machinability of fiber reinforced composite materials or ceramics are poor, which makes it very difficult to prepare fiber reinforced composite materials or ceramic parts with complex structures, limiting their practical application. Connecting them with metal materials with high plasticity and good machinability to form composite components can achieve complementary performance. At present, fiber reinforced composite materials or ceramics and metals are generally connected by brazing, but due to the mismatch in the thermal expansion coefficients of fiber reinforced composite materials or ceramics and metals, there is often a large residual stress in the fiber reinforced composite material or ceramic-metal joint, which seriously weakens the comprehensive mechanical properties of the joint, especially for large-size welding surface structures, the harm of residual stress is particularly significant. It can be seen that alleviating the high residual stress of the brazed joint is extremely important for achieving high-quality connection between fiber reinforced composite materials or ceramics and metals.

[0003] In recent years, the use of porous materials with unique network structures as transition layers to assist in brazing fiber-reinforced composites or ceramics with metals has been shown to address the difficulty of uniformly dispersing high-performance reinforcing phases within the braze joint, effectively improving the overall plasticity of the joint and relieving residual stress in the joint. However, the most widely used porous materials, such as Cu and Ni metals and low-thermal expansion ceramics, suffer from high production costs, poor high-temperature performance, excessively high thermal expansion coefficients, or high brittleness, limiting their effectiveness in strengthening the joint. Therefore, the development of new, low-cost, porous transition layers for brazing that are thermodynamically stable, have low thermal expansion coefficients, and are highly flexible is urgently needed. Summary of the Invention

[0004] The present invention addresses the problem of large residual stress in brazed joints of fiber-reinforced composite materials or ceramics and metals, and proposes a method for assisting the brazing of fiber-reinforced composite materials or ceramics and metals with a hollow mesh flexible carbon sponge transition layer. A vacuum rapid carbonization process is adopted, and melamine formaldehyde resin foam is used as a precursor to quickly prepare a flexible carbon sponge transition layer with a hollow mesh structure. In the process of using this transition layer to assist in the brazing of fiber-reinforced composite materials or ceramics and metals, the liquid active brazing material will spontaneously perform capillary infiltration and completely fill the unique hollow tubes of the carbon sponge, forming an in-situ composite core-sheath structure with a three-dimensional double-continuous network carbon sponge (shell) wrapped in a brazing alloy (core). Compared with a single network carbon material having poor plasticity, the core-sheath structure sponge transition layer formed in situ by this patent utilizes a metal core to significantly enhance the plasticity of the carbon sponge shell, thereby improving the overall strain control capability of the material, better playing the role of load transfer and dispersion during the service of the joint, and reducing the failure sensitivity of the joint. The hollow mesh flexible carbon sponge transition layer used in this patent can effectively improve the interface structure, increase the plastic toughness of the brazing seam and reduce the thermal expansion coefficient of the brazing seam, thereby alleviating the high residual stress of the joint after welding and significantly improving the comprehensive mechanical properties of fiber-reinforced composite materials or ceramic and metal joints.

[0005] The specific steps of the basic technical solution of the present invention are summarized as follows:

[0006] A method for brazing fiber-reinforced composite materials or ceramics with metals using a hollow mesh flexible carbon sponge transition layer as an auxiliary means. First, melamine formaldehyde resin foam is rapidly carbonized in a vacuum to obtain a carbon sponge. The carbon sponge is then used as a transition layer to assist in brazing the fiber-reinforced composite materials or ceramics with the metals.

[0007] The specific steps include:

[0008] (1) According to the shape and size of the surface of the base material to be welded during the brazing assembly process, cutting melamine formaldehyde resin foam of corresponding shape and size as a precursor for preparing carbon sponge;

[0009] (2) First, heat the mixed box / tube furnace to 800-1100°C at a rate of 5-30°C / min and keep the temperature constant;

[0010] Subsequently, the precursor obtained in step (1) was placed in a quartz tube with one side closed and the pressure in the quartz tube was pumped down to 3Pa~3×10 –3 Pa, then insert the quartz tube into a high-temperature mixed box / tube furnace and place the precursor in the center of the furnace, keep it for 5min to 60min and then quickly take it out, wait for the quartz tube to cool to room temperature, and take out the carbon sponge product;

[0011] (3) assembling the carbon sponge product obtained in step (2) with a commercially available active brazing filler metal according to the structure of brazing filler metal / carbon sponge / brazing filler metal, and placing the resultant product between the fiber-reinforced composite material or ceramic and the metal surface to be welded, thereby completing the brazing assembly;

[0012] (4) Place the welded assembly of step (3) into a vacuum brazing furnace and evacuate to a vacuum degree of less than 3×10 –3 Pa, then heat the vacuum brazing furnace hearth to 30-120°C above the melting point of the brazing material at a heating rate of 5-30°C / min, then keep it warm for 5-60 minutes, and finally cool the vacuum brazing furnace hearth to room temperature at a cooling rate of 1-10°C / min to complete the brazing process and obtain a fiber reinforced composite material or ceramic and metal brazing joint.

[0013] In step (2), the solder is in the form of foil or solder paste, which has no effect on the structural assembly method.

[0014] In step (2), the heating rate is 5°C / min, the temperature is raised to 850°C, and the holding time is 50 minutes.

[0015] In step (2), the heating rate is 10°C / min, the temperature is raised to 950°C, and the holding time is 10 minutes.

[0016] In step (3), the active solder foil includes Ag-27.5Cu-4.5Ti (wt.%), Ti-35Zr-15Ni-15Cu (wt.%), Ag-23.4Cu-14.3In-3.5Ti (wt.%), and Ti34Ni66 (wt.%).

[0017] In step (3), the fiber-reinforced composite material includes a carbon fiber reinforced carbon-based (C / C) composite material, a carbon fiber reinforced silicon carbide-based (C / SiC) composite material, a silicon carbide fiber reinforced silicon carbide-based (SiC / SiC) composite material or a silica fiber reinforced silica-based (SiO2 / SiO2) composite material.

[0018] In step (3), the ceramic includes Al2O3 ceramic, SiC ceramic, SiN ceramic, graphite, BN ceramic, AlN ceramic or diamond.

[0019] In step (3), the metal includes metal Nb, GH99 high-temperature alloy, GH3536 high-temperature alloy, TC4 titanium alloy or TiAl alloy.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention uses low-cost melamine formaldehyde resin foam as the raw material for preparing the carbon sponge transition layer. Compared with other common transition layer materials for network structure brazing (including foam metal, porous ceramics, and carbon nanomaterial sponge), the present invention significantly reduces the production cost of the transition layer while ensuring that the transition layer can alleviate the high residual stress of the joint and thus improve the joint connection strength.

[0022] (2) The present invention utilizes a method for rapidly carbonizing a precursor in a hybrid box / tube furnace to obtain a carbon sponge, which can continuously and multiple times sample while maintaining the furnace temperature, thereby realizing the rapid preparation of a large number of carbon sponge materials with arbitrary morphologies and sizes. The method is simple, efficient, and can reduce production energy consumption.

[0023] (3) The hollow network structure of the flexible carbon sponge transition layer of the present invention maintains a complete skeleton structure and does not collapse during the entire brazing process. During the brazing process, the molten brazing material is fully infiltrated into the carbon sponge by the capillary force of the hollow structure, forming a sandwich porous composite material and strengthening the skeleton structure of the carbon sponge.

[0024] (4) During the brazing process, the hollow network structure flexible carbon sponge transition layer of the present invention utilizes the excellent wettability of the carbon sponge transition layer, allowing the liquid active brazing material to spontaneously penetrate into the carbon sponge, forming an in-situ active brazing material transition layer wrapped in a carbon sponge with a core-sheath structure. This in-situ formed core-sheath transition layer not only enhances the strain control capability of the carbon sponge without the introduction of a foam metal substrate, but also plays a role in load transfer and dispersion during the service life of the joint, thereby reducing the joint's sensitivity to failure.

[0025] (5) The carbon sponge transition layer of the present invention easily reacts with active elements such as Ti, Cr, and Fe in various active solders such as Ag-based, Cu-based, Ti-based, and Ni-based solders, that is, it has good wettability matching with many types of commercially available active solders, and has wide applicability and strong practicality.

[0026] (6) The carbon sponge transition layer designed and developed in this patent has an extremely low thermal expansion coefficient, which can effectively reduce the thermal expansion coefficient of the entire brazing joint. In addition, the use of spontaneously infiltrated Ag-Cu-Ti brazing filler metal as the core substrate compensates for the plasticity of the carbon sponge and strengthens the strain adjustment ability of the transition layer, which helps to alleviate the residual stress of the joint and load transfer and dispersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The microstructure of the joint between C / C composite material and Nb metal brazing using carbon sponge as a transition layer and Ag-27.5Cu-4.5Ti (wt.%) active brazing foil;

[0028] Figure 2 This is a comparison chart of joint strength without transition layer and with carbon sponge transition layer;

[0029] Figure 3 This is the SEM image of the carbon sponge after carbonization treatment of melamine formaldehyde resin foam with a porosity of 99.0%. DETAILED DESCRIPTION

[0030] This invention describes a method for brazing fiber-reinforced composite materials or ceramics with metals using a hollow, reticulated, flexible carbon sponge transition layer. This method uses a hybrid box / tube furnace to rapidly vacuum-carbonize a melamine-formaldehyde resin foam precursor to produce a carbon sponge material. This material is then used as a transition layer to assist in brazing fiber-reinforced composite materials or ceramics with metals. By leveraging the inherent properties and network structure of the carbon material, a gradient transition in joint properties is achieved, mitigating high residual stress in large-scale joints and improving joint quality. The technical solutions of this invention are not limited to the specific embodiments listed below but also include any combination of the various specific embodiments.

[0031] Example 1

[0032] A method for brazing fiber-reinforced composite materials or ceramics with metals using a hollow mesh flexible carbon sponge transition layer is mainly divided into the following steps:

[0033] In this embodiment, a method for brazing a fiber-reinforced composite material or ceramic with a metal using a hollow mesh flexible carbon sponge transition layer is implemented by the following steps:

[0034] (1) Melamine formaldehyde resin foam with a porosity of 99% was cut into thin sheets with a side thickness of 2 mm and a length and width of 10 mm, which was used as a precursor for preparing carbon sponge.

[0035] (2) The mixed box / tube furnace was heated to 950°C at a rate of 10°C / min and kept at this temperature. Subsequently, the precursor obtained in step 1 was placed in a quartz tube with one side closed and the pressure in the quartz tube was reduced to 3×10 –3 Pa, then insert the quartz tube into a high-temperature tube furnace and place the precursor in the center of the furnace, keep it for 30 minutes and then quickly take it out. After the quartz tube cools to room temperature, take out the carbon sponge product.

[0036] (3) The carbon sponge product is used as a transition layer and Ag-27.5Cu-4.5Ti (wt.%) active brazing material foil is assembled in the form of foil / carbon sponge / foil, and placed between the C / C composite material and the Nb surface of the metal to be welded to complete the brazing assembly. The welded assembly is placed in a vacuum brazing furnace and evacuated to a vacuum degree of less than 3×10 –3 Pa, then the vacuum brazing furnace hearth was heated to 880℃ at a heating rate of 10℃ / min and kept warm for 10min. Finally, the vacuum brazing furnace hearth was cooled to room temperature at a cooling rate of 5℃ / min to complete the brazing process and obtain the C / C composite material and metal Nb brazing joint.

[0037] Figure 1 This image shows the microstructure of a joint brazed between a C / C composite and Nb metal using carbon sponge as a transition layer and an Ag-27.5Cu-4.5Ti (wt.%) active brazing filler metal foil. The joint interface is structurally intact, free of cracks, pores, and other defects. Furthermore, the in-situ carbon sponge reaction product is observed in the brazed seam, demonstrating its structural integrity and intact structure.

[0038] like Figure 2 As shown in the figure, the introduction of carbon sponge improves the gradient transition of thermal expansion coefficient of the interface structure, effectively relieves the high residual stress of the brazed joint, and the average shear strength of the joint at room temperature reaches 48 MPa, which is more than 2.6 times higher than that of the direct brazing joint without a transition layer.

[0039] Example 2

[0040] This embodiment differs from the first embodiment in that:

[0041] Step (1) Melamine formaldehyde resin foam with a porosity of 99.0% is cut into thin sheets with a side thickness of 1 mm and a length and width of 10 mm;

[0042] Step (2) heating the hybrid box / tube furnace to 900° C. at a rate of 10° C. / min; Step (2) inserting the quartz tube into the high-temperature tube furnace and placing the precursor in the center of the furnace, holding for 20 minutes, and then quickly removing it;

[0043] Step (3) The carbon sponge product is used as a transition layer and assembled with Ti-35Zr-15Ni-15Cu (wt.%) active brazing material foil in the form of foil / carbon sponge / foil, and placed between the C / SiC composite material and the GH3536 high-temperature alloy to be welded to complete the brazing assembly. The welded assembly is placed in a vacuum brazing furnace and evacuated to a vacuum degree of less than 3×10 –3 Pa, then the vacuum brazing furnace was heated to 970°C at a heating rate of 10°C / min and held at that temperature for 15 minutes. Finally, the vacuum brazing furnace was cooled to room temperature at a cooling rate of 5°C / min, completing the brazing process and obtaining a brazed joint between the C / SiC composite material and the GH3536 high-temperature alloy. Other steps and parameters were the same as those in the first embodiment.

[0044] Figure 3 This is an SEM image of a carbon sponge made from 99.0% porosity melamine-formaldehyde resin foam after carbonization. The low-magnification SEM image shows a clear, structurally intact carbon sponge skeleton. The high-magnification SEM image reveals a hollow, tubular structure with nanometer-scale wall thickness, demonstrating a large specific surface area.

[0045] Example 3

[0046] The difference between this embodiment and specific embodiment one or two is that: in step (3), Al2O3 ceramic and TC4 alloy are welded using Ag-23.4Cu-14.3In-3.5Ti (wt.%) foil as solder, with a heating rate of 10°C / min, a brazing temperature of 750°C, a holding time of 20 minutes, and a cooling rate of 5°C / min. The other steps and parameters are the same as those in specific embodiment one or two.

[0047] Example 4

[0048] The difference between this embodiment and specific embodiments one to three is that: in step (1), the melamine formaldehyde resin foam with a porosity of 99.3% is cut into thin slices with a side thickness of 0.8 mm and a length and width of 10 mm. The other steps and parameters are the same as those of specific embodiments one to three.

[0049] Example 5

[0050] The difference between this embodiment and specific embodiments one to four is that in step (1), the melamine formaldehyde resin foam with a porosity of 99.5% is cut into thin slices with a side thickness of 1.0 mm and a length and width of 10 mm. The other steps and parameters are the same as those of specific embodiments one to four.

[0051] Example 6

[0052] The difference between this embodiment and specific embodiments 1 to 5 is that in step (2), the temperature is raised to 800°C and maintained for 30 minutes before being quickly removed and cooled to room temperature. The other steps and parameters are the same as those of specific embodiments 1 to 5.

[0053] Example 7

[0054] The difference between this embodiment and specific embodiments 1 to 6 is that in step (2), the temperature is raised to 900°C and maintained for 10 minutes before being quickly removed and cooled to room temperature. The other steps and parameters are the same as those of specific embodiments 1 to 6.

[0055] Example 8

[0056] The difference between this embodiment and specific embodiments 1 to 7 is that in step (2), the temperature is raised to 1000°C, maintained for 5 minutes, and then quickly removed and cooled to room temperature. The other steps and parameters are the same as those of specific embodiments 1 to 7.

Claims

1. A method for brazing fiber-reinforced composite materials or ceramics with metals using a hollow mesh flexible carbon sponge transition layer, characterized in that: First, melamine formaldehyde resin foam is rapidly carbonized in a vacuum to obtain carbon sponge, and then the carbon sponge is used as a transition layer to assist in brazing fiber-reinforced composite materials or ceramics with metals. The specific steps include: (1) According to the shape and size of the surface of the base material to be welded during the brazing assembly process, cutting melamine formaldehyde resin foam of corresponding shape and size as a precursor for preparing carbon sponge; (2) First, heat the mixed box / tube furnace to 800-1100°C at a rate of 5-30°C / min and keep the temperature constant; Subsequently, the precursor obtained in step (1) was placed in a quartz tube with one side closed and the pressure in the quartz tube was pumped down to 3Pa~3×10 –3 Pa, then insert the quartz tube into a high-temperature mixed box / tube furnace and place the precursor in the center of the furnace, keep it for 5min to 60min and then quickly take it out, wait for the quartz tube to cool to room temperature, and take out the carbon sponge product; (3) assembling the carbon sponge product obtained in step (2) with a commercially available active brazing filler metal according to the structure of brazing filler metal / carbon sponge / brazing filler metal, and placing the resultant product between the fiber-reinforced composite material or ceramic and the metal surface to be welded, thereby completing the brazing assembly; (4) Place the welded assembly of step (3) into a vacuum brazing furnace and evacuate to a vacuum degree of less than 3×10 –3 Pa, then heat the vacuum brazing furnace hearth to 30-120°C above the melting point of the brazing material at a heating rate of 5-30°C / min, then keep it warm for 5-60 minutes, and finally cool the vacuum brazing furnace hearth to room temperature at a cooling rate of 1-10°C / min to complete the brazing process and obtain a fiber reinforced composite material or ceramic and metal brazing joint.

2. The method according to claim 1, wherein In step (2), the solder is in the form of foil or solder paste.

3. The method according to claim 1, wherein In step (2), the heating rate is 5°C / min, the temperature is raised to 850°C, and the holding time is 50 minutes.

4. The method according to claim 1, wherein In step (2), the heating rate is 10°C / min, the temperature is raised to 950°C, and the holding time is 10 minutes.

5. The method according to claim 1, wherein In step (3), the active solder includes Ag-27.5Cu-4.5Ti (wt.%), Ti-35Zr-15Ni-15Cu (wt.%), Ag-23.4Cu-14.3In-3.5Ti (wt.%) or Ti34Ni66 (wt.%).

6. The method according to claim 1, wherein In step (3), the fiber-reinforced composite material includes a carbon fiber-reinforced carbon-based C / C composite material, a carbon fiber-reinforced silicon carbide-based C / SiC composite material, a silicon carbide fiber-reinforced silicon carbide-based SiC / SiC composite material, or a silica fiber-reinforced silica-based SiO2 / SiO2 composite material.

7. The method according to claim 1, wherein In step (3), the ceramic includes Al2O3 ceramic, SiC ceramic, SiN ceramic, graphite, BN ceramic, AlN ceramic or diamond.

8. The method according to claim 1, wherein In step (3), the metal includes metal Nb, GH99 high-temperature alloy, GH3536 high-temperature alloy, TC4 titanium alloy or TiAl alloy.

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