Brazing connection method for SiCf / SiC composite material and metal

Abstract

The invention relates to the technical field of connection of ceramic matrix composites and metals, in particular to a brazing connection method of a SiCf / SiC composite and a metal. According to the method, the to-be-brazed face of the SiCf / SiC composite material is optimized through water-guided laser machining, punching machining is conducted on a low-toughness continuous SiC matrix, a defect area of the composite material and a SiCf area parallel to the to-be-brazed face, and the wettability of the to-be-brazed side of the composite material is improved; meanwhile, an interlocking structure corresponding to the metal material is machined on the surface of the metal material through laser etching, and through the interlocking effect of the metal and the SiCf / SiC composite material, the fracture toughness of the joint is further improved, and the shear strength of the joint is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic matrix composite materials and metal connection, and more specifically, to a SiC f Brazing connection method of / SiC composite material and metal. Background Art

[0002] Carbon fiber reinforced silicon carbide ceramic matrix composites (SiC f / SiC composite materials) have significant properties such as low density, low thermal expansion coefficient, high specific stiffness, excellent fracture toughness, oxidation resistance, friction resistance, thermal conductivity and thermal shock resistance, and are ideal structural materials for high temperature applications. In spacecraft, SiC f SiC composite materials can be used in combination with metal materials to make up for the shortcomings of high density and low temperature resistance of metal materials. They have broad application prospects in hot end components that need to withstand extremely high temperatures, such as thermal protection systems, rocket engine nozzles, turbine blades, and aircraft brake components. f / SiC composite materials and metal connection joints have high requirements on strength, reliability and heat resistance.

[0003] Currently, SiC f The connection technologies of SiC composite materials mainly include adhesive connection, mechanical connection, diffusion bonding and brazing. Adhesive connection and mechanical connection are difficult to meet the requirements of heat resistance and reliability. Although diffusion bonding can achieve reliable connection, its process is complicated and costly, which has certain limitations in practical application. In comparison, brazing technology is superior in that it has simple process and good structural adaptability, and is a good choice for SiC composite materials. f / SiC composite materials are the main method of joining. However, due to the f / SiC composite materials have low thermal expansion coefficient and poor brazing wettability. The joints obtained by brazing have connection thermal stress and low interface bonding strength, which leads to the SiC f The connection strength between / SiC composite materials and metals is low and the reliability is poor.

[0004] Active brazing and the introduction of intermediate layers are currently the main methods to improve SiC f / SiC composite materials and metal joint strength is an effective way. For example, Chinese invention patent CN115213583A discloses a method for SiC f Brazing connection method for connecting SiC composite materials using nickel-chromium alloy powder modified by adding silicon powder f / SiC composite material, the resulting joint shear strength is 35.21Mpa, but the joint strength improvement of this method is limited and the high-temperature mechanical properties of the resulting joint are poor. fA method for improving the toughness of heterogeneous brazing joints of / SiC composite materials is proposed. By introducing a buffer metal foam and a special high-entropy brazing filler metal for synergistic effect, a brazing joint with low residual stress and high strength is obtained. However, this method has problems such as difficulty in controlling the interface reaction and uneven joint performance, and the prepared joint has poor stability.

[0005] In addition, SiC f / SiC composite-metal structural parts suffer from brittle fracture failure, and the fracture path is mainly concentrated in SiC f The reaction layer on one side of the SiC / SiC composite material f / SiC composite material, and the fracture surface shows SiC f Interface fracture between SiC composite material and reaction layer, SiC matrix fracture, SiC f Fracture, SiC f Typical characteristics of peeling from the composite surface. f The brittleness and structural defects (pores, cracks, etc.) of SiC / SiC composite materials are also important factors affecting the joint strength. In fact, SiC prepared by current mainstream methods such as chemical vapor infiltration, polymer impregnation cracking, reactive infiltration and composite processes f / SiC composite materials inevitably have defects such as pores and microcracks. In addition, the toughness of the SiC matrix of the composite material is poor, and the SiC f The low interfacial bonding strength with the SiC matrix also significantly restricts the improvement of joint strength. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a SiC f / SiC composite material and metal brazing connection method. The present invention uses water-guided laser processing to optimize SiC f / SiC composite material to be brazed surface, in the low toughness continuous SiC matrix, composite material defect area and SiC parallel to the surface to be brazed f The area is punched to improve the wettability of the side of the composite material to be brazed; at the same time, the corresponding interlocking structure is laser-etched on the surface of the metal material, and the metal and SiC f The interlocking effect of the SiC / SiC composite material further improves the fracture toughness of the joint and enhances the shear strength of the joint.

[0007] The object of the present invention is to provide a SiC f / SiC composite material and metal brazing connection method. To achieve the above purpose, the present invention provides the following technical solutions: A SiC f A brazing connection method of a SiC composite material and a metal comprises the following steps: Step 1: Use micro-CT to examine SiC f / SiC composite materials were three-dimensionally reconstructed to clarify SiC f Size and SiC f (SiC fiber) and SiC matrix distribution; Step 2: Polishing SiC f The surface of the brazing surface of the / SiC composite material was then observed under an optical microscope to mark the continuous SiC matrix and SiC f / SiC composite material defect area and SiC parallel to the surface to be brazed f The area serves as a processing area; Step 3: Using a water-guided laser processing method, a continuous tapered hole array is processed in the processing area marked in step 2 to optimize the structure of the surface to be brazed of the composite material; Step 4: Using a laser etching method, a conical interlocking structure corresponding to the conical hole array in step 3 is processed on the metal surface to be brazed; Step 5: Process the SiC f / Pre-weld treatment of SiC composite materials and metals; Step 6: Apply solder paste evenly to SiC f The conical hole area of ​​the surface to be brazed of the SiC / SiC composite material is assembled with the surface to be brazed of the metal and the surface to be brazed of the composite material, and then vacuum brazing is performed.

[0008] Furthermore, in step 2, use 240#~800# silicon carbide sandpaper to polish the SiC f / SiC composite material surface roughness Ra≤0.8μm.

[0009] Furthermore, in step 3, the processing depth of each processing area is ≤1 mm, and the processing inner wall roughness Ra is ≤1.6 μm.

[0010] Furthermore, in step 3, the bottom diameter of the conical holes is 0.1 mm to 0.3 mm, and they are arranged in a square array with a density of 10 to 20 conical holes per square centimeter.

[0011] Furthermore, in step 4, SiC f The conical interlocking structure gap between the / SiC composite material and the metal is 0.1mm~0.2mm, and the milling surface roughness Ra≤0.8μm.

[0012] Furthermore, the specific method of pre-welding treatment in step 5 is to process the processed SiC f The SiC / SiC composite material and metal were immersed in acetone respectively, ultrasonically cleaned for 10 min to 15 min, and then blown dry for use.

[0013] Preferably, the ultrasonic cleaning parameters in step 5 are: ultrasonic frequency: 40kHz~100kHz, cleaning temperature: 30℃~50℃.

[0014] Furthermore, after the metal and composite surfaces to be brazed are assembled in step 6, the assembly is placed in an Al2O3 ceramic fixture. A uniform pressure of 5 kPa to 10 kPa is then applied to the assembly using a ceramic block. The pressure applied by the ceramic block promotes wetting and capillary action of the solder paste.

[0015] Furthermore, the preparation method of the solder paste in step 6 is to mix the solder alloy powder and the additive and stir them evenly; the solder alloy powder is selected according to the metal type, including but not limited to Ni-Cr-Si-B-Ti, Pd-Cu-Ti, Au-Ni-Ti, Cu-Ni-Ti, Ti-Zr-Cu-Ni, and Ti-V-Cr.

[0016] Furthermore, the specific method of vacuum brazing in step 6 is: placing the assembly in a vacuum brazing furnace, and evacuating the furnace to a vacuum degree of ≤5×10 -5 Start heating after Pa, increase the temperature to 200℃~300℃ at a heating rate of 5℃ / min~10℃ / min, and keep it warm for 10min~20min, then increase the temperature to 100℃~150℃ at a heating rate of 10℃ / min~20℃ / min, and keep it warm for 20min~30min, then increase the temperature to brazing temperature at a heating rate of 3℃ / min~5℃ / min, and keep it warm for 10min~40min; cool down to below 400℃ at a cooling rate of 5℃ / min~10℃ / min, and then cool with the furnace.

[0017] Preferably, the brazing temperature is 10°C to 50°C higher than the liquidus of the brazing alloy.

[0018] The technical solution provided by the present invention has at least the following beneficial effects compared to the prior art: The present invention uses water-guided laser processing to optimize SiC f / SiC composite material to be brazed, in the low-toughness continuous SiC matrix, composite material defect area and SiC parallel to the joint surface f Punching is performed in the area to improve the wettability of the side of the composite material to be brazed, which can effectively solve the problem of SiC matrix fracture and SiC f The problem of peeling affecting the joint strength; at the same time, the corresponding interlocking structure is processed by laser etching on the surface of the metal material, and the metal and SiC f The interlocking effect of the SiC / SiC composite material further improves the fracture toughness of the joint and increases the shear strength of the joint. In addition, the contact area between the composite material and the metal is increased in the present invention, further enhancing the interface bonding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 For example 1, the silicon carbide sandpaper is used to polish SiC f / SiC composite material to be brazed surface structure diagram; Figure 2 The SiC is optimized by water-guided laser in Example 1. f / Structure diagram of the surface to be brazed of SiC composite material; Figure 3 This is a structural diagram of the surface to be brazed of the GH4169 alloy after laser etching in Example 1; Among them, 1-continuous SiC matrix, 2-composite material defect area, 3-SiC perpendicular to the surface to be brazed f Region 4 - SiC parallel to the surface to be brazed f Area, 5-SiC f / SiC composite material surface to be brazed. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to more clearly understand the present application, the present invention is further described in detail below with reference to the examples and drawings. However, it should be understood that the following examples are only preferred embodiments of the present invention, and the scope of protection claimed in the present invention shall be subject to the scope defined in the claims. Unless otherwise expressly indicated, throughout the specification and claims, the term "comprise" or its variations such as "comprises" or "comprising" shall be understood to include the stated elements or components without excluding other elements or other components.

[0021] In the description of the present invention, it should be noted that if specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0022] In addition, in order to better illustrate the present invention, numerous specific details are provided in the specific embodiments below. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In some embodiments, raw materials, methods, means, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present invention.

[0023] Example 1

[0024] This embodiment provides a SiC f Brazing connection method of SiC composite material and GH4169 alloy, the SiC used fThe / SiC composite material is a three-dimensional structure, which is cut into 5mm×5mm×5mm square samples using chemical vapor infiltration, and the GH4169 alloy is cut into 10mm×10mm×5mm samples. The solder used in this example is Pd 65 -Cu 25 -Ti 10 The solder has a solidus temperature of 850°C and a liquidus temperature of 1050°C. The specific technical solution is as follows: A SiC f The brazing connection method of the SiC composite material and the GH4169 alloy comprises the following steps: Step 1: Use micro-CT to examine SiC f / SiC composite materials were three-dimensionally reconstructed to clarify SiC f Size and SiC f and SiC matrix distribution; Step 2: Use 240#, 400#, and 800# silicon carbide sandpaper to polish SiC f The surface of the / SiC composite material to be brazed is then observed under an optical microscope to mark the continuous SiC matrix of the surface to be brazed, the defective area of ​​the composite material, and the SiC parallel to the surface to be brazed. f The area is used as the processing area, and the processing path file is configured. The structure of the surface to be brazed is as follows Figure 1 As shown; Step 3: Place the composite material on the water-guided laser processing platform, import the processing path file, and use the water-guided laser processing method to process a continuous conical hole array in the processing area marked in step 2 to optimize the structure of the composite material surface to be brazed; the density of the conical holes in the array is 12 per square centimeter, the hole depth is 0.5mm, and the roughness Ra is ≤1.6μm; the optimized structure of the composite material surface to be brazed is as follows Figure 2 As shown; Step 4: Laser etching is used to process the conical interlocking structure corresponding to the conical hole array in step 3 on the surface of GH4169 alloy to be brazed; GH4169 alloy and SiC f The gap of the conical interlocking structure of the / SiC composite material is 0.1mm, and the roughness Ra is ≤ 0.8μm. The structure of the GH4169 alloy to be brazed after laser etching is as follows Figure 3 As shown; Step 5: Process the SiC f / SiC composite materials and GH4169 alloy are pre-treated before welding; the specific method of pre-treatment is to process the SiC fThe SiC / SiC composite material and GH4169 alloy were immersed in acetone and ultrasonically cleaned for 15 min three times using an ultrasonic cleaner. After ultrasonic cleaning, they were rinsed with anhydrous ethanol and dried for later use. The ultrasonic frequency was 40 kHz and the cleaning temperature was 35°C. Step 6: Weigh Pd 65 -Cu 25 -Ti 10 Alloy powder, after adding binder and stirring evenly, obtain Pd 65 -Cu 25 -Ti 10 Solder paste; apply solder paste evenly to SiC f The conical hole area of ​​the surface to be brazed of the GH4169 alloy and the surface to be brazed of the composite material were assembled, and the assembled parts were placed in an Al2O3 ceramic fixture. A 12.5g ceramic block was then used to apply a uniform pressure of 5kPa to the assembled parts. The entire fixture was then placed in a vacuum brazing furnace and evacuated to a vacuum degree of ≤5×10 -5 After Pa, heating was started, and the temperature was increased to 300℃ at a heating rate of 5℃ / min and kept at this temperature for 10min, then the temperature was increased to 800℃ at a heating rate of 15℃ / min and kept at this temperature for 30min, and then the temperature was increased to 1080℃ at a heating rate of 5℃ / min and kept at this temperature for 10min; finally, the temperature was decreased to below 400℃ at a cooling rate of 5℃ / min, and then cooled with the furnace. f / SiC composite material-GH4169 alloy brazed joint.

[0025] The SiC obtained in Example 1 was tested using an electronic universal testing machine. f The room temperature shear strength test of the brazed joint of / SiC composite material and GH4169 alloy was carried out. The shear strength of the joint was calculated according to the maximum load. The average value of five samples was taken after continuous testing. The average room temperature shear strength of the brazed joint was 126MPa.

[0026] The SiC obtained in Example 1 was tested using a high temperature shear tester. f The shear strength of the brazed joint of SiC composite material and GH4169 alloy at 800℃ was 83 MPa after continuous testing of five samples and the average value was taken.

[0027] Example 2

[0028] This embodiment provides a SiC f Brazing connection method of SiC composite material and GH4169 alloy, the SiC used fThe / SiC composite material is a two-dimensional structure, which was cut into 5mm×5mm×5mm square specimens by chemical vapor infiltration, and the GH4169 alloy was cut into 10mm×10mm×5mm specimens. The brazing material used in this example is Pd 65 -Cu 25 -Ti 10 The solder has a solidus temperature of 850°C and a liquidus temperature of 1050°C. The specific technical solution is as follows: A SiC f The brazing connection method of the SiC composite material and the GH4169 alloy comprises the following steps: Step 1: Use micro-CT to examine SiC f / SiC composite materials were three-dimensionally reconstructed to clarify SiC f Size and SiC f and SiC matrix distribution; Step 2: Use 240#, 400#, and 800# silicon carbide sandpaper to polish SiC f The surface of the / SiC composite material to be brazed is then observed under an optical microscope to mark the continuous SiC matrix of the surface to be brazed, the defective area of ​​the composite material, and the SiC parallel to the surface to be brazed. f The area is used as the processing area and the processing path file is configured; Step 3: Place the composite material onto a water-guided laser processing platform, import the processing path file, and use water-guided laser processing to machine a continuous tapered hole array within the processing area marked in Step 2 to optimize the structure of the composite material surface to be brazed. The tapered holes in the array have a density of 12 per square centimeter, a hole depth of 0.5 mm, and a roughness Ra of ≤ 1.6 μm. Step 4: Laser etching is used to process the conical interlocking structure corresponding to the conical hole array in step 3 on the surface of GH4169 alloy to be brazed; GH4169 alloy and SiC f The gap of the conical interlocking structure of the / SiC composite material is 0.1mm, and the roughness Ra ≤ 0.8μm; Step 5: Process the SiC f / SiC composite materials and GH4169 alloy are pre-treated before welding; the specific method of pre-treatment is to process the SiC f The SiC / SiC composite and GH4169 alloy were immersed in acetone and ultrasonically cleaned for 15 min three times using an ultrasonic cleaner. After ultrasonic cleaning, they were rinsed with anhydrous ethanol and dried for later use. The ultrasonic frequency was 40 kHz and the cleaning temperature was 35°C. Step 6: Weigh Pd 65 -Cu 25 -Ti 10Alloy powder, after adding binder and stirring evenly, obtain Pd 65 -Cu 25 -Ti 10 Solder paste; apply solder paste evenly to SiC f The conical hole area of ​​the surface to be brazed of the GH4169 alloy and the surface to be brazed of the composite material were assembled, and the assembled parts were placed in an Al2O3 ceramic fixture. A 12.5g ceramic block was then used to apply a uniform pressure of 5kPa to the assembled parts. The entire fixture was then placed in a vacuum brazing furnace and evacuated to a vacuum degree of ≤5×10 -5 After Pa, heating was started, and the temperature was increased to 300℃ at a heating rate of 5℃ / min and kept at this temperature for 10min, then the temperature was increased to 800℃ at a heating rate of 15℃ / min and kept at this temperature for 30min, and then the temperature was increased to 1080℃ at a heating rate of 5℃ / min and kept at this temperature for 10min; finally, the temperature was decreased to below 400℃ at a cooling rate of 5℃ / min, and then cooled with the furnace. f / SiC composite material-GH4169 alloy brazed joint.

[0029] The SiC obtained in Example 2 was tested using an electronic universal testing machine. f The room temperature shear strength test of the brazed joint of / SiC composite material and GH4169 alloy was carried out. The shear strength of the joint was calculated according to the maximum load. The average value of five samples was taken after continuous testing. The average room temperature shear strength of the brazed joint was 136MPa.

[0030] The SiC obtained in Example 2 was tested using a high temperature shear tester. f The shear strength of the brazed joint of SiC composite material and GH4169 alloy at 800℃ was 72MPa after continuous testing of five samples and the average value was taken.

[0031] Example 3

[0032] This embodiment provides a SiC f Brazing connection method of SiC composite material and GH536 alloy, the SiC used f The / SiC composite material is a three-dimensional structure, which is cut into 5mm×5mm×5mm square specimens by chemical vapor infiltration, and the GH536 alloy is cut into 10mm×10mm×5mm specimens. The solder used in this example is Pd 65 -Cu 25 -Ti 10 The solder has a solidus temperature of 850°C and a liquidus temperature of 1050°C. The specific technical solution is as follows: A SiC fThe brazing connection method of the SiC composite material and the GH4169 alloy comprises the following steps: Step 1: Use micro-CT to examine SiC f / SiC composite materials were three-dimensionally reconstructed to clarify SiC f Size and SiC f and SiC matrix distribution; Step 2: Use 240#, 400#, and 800# silicon carbide sandpaper to polish SiC f The surface of the / SiC composite material to be brazed is then observed under an optical microscope to mark the continuous SiC matrix of the surface to be brazed, the defective area of ​​the composite material, and the SiC parallel to the surface to be brazed. f The area is used as the processing area and the processing path file is configured; Step 3: Place the composite material onto a water-guided laser processing platform, import the processing path file, and use water-guided laser processing to machine a continuous tapered hole array within the processing area marked in Step 2 to optimize the structure of the composite material surface to be brazed. The tapered holes in the array have a density of 16 per square centimeter, a hole depth of 0.5 mm, and a roughness Ra of ≤ 1.6 μm. Step 4: Laser etching is used to process the conical interlocking structure corresponding to the conical hole array in step 3 on the surface of the GH536 alloy to be brazed; GH536 alloy and SiC f The gap of the conical interlocking structure of the / SiC composite material is 0.1mm, and the roughness Ra ≤ 0.8μm; Step 5: Process the SiC f / SiC composite materials and GH536 alloy are pre-treated before welding; the specific method of pre-treatment is to process the SiC f The SiC / SiC composite material and GH536 alloy were immersed in acetone and ultrasonically cleaned for 15 min three times using an ultrasonic cleaner. After ultrasonic cleaning, they were rinsed with anhydrous ethanol and dried for later use. The ultrasonic frequency was 40 kHz and the cleaning temperature was 35°C. Step 6: Weigh Pd 65 -Cu 25 -Ti 10 Alloy powder, after adding binder and stirring evenly, obtain Pd 65 -Cu 25 -Ti 10 Solder paste; apply solder paste evenly to SiC f The conical hole area of ​​the surface to be brazed of the GH536 alloy and the surface to be brazed of the composite material were assembled, and the assembled parts were placed in an Al2O3 ceramic fixture. A 12.5g ceramic block was then used to apply a uniform pressure of 5kPa to the assembled parts. The entire fixture was then placed in a vacuum brazing furnace and evacuated to a vacuum degree of ≤5×10-5 After Pa, heating was started, and the temperature was increased to 300℃ at a heating rate of 5℃ / min and kept at this temperature for 10min, then the temperature was increased to 800℃ at a heating rate of 15℃ / min and kept at this temperature for 30min, and then the temperature was increased to 1080℃ at a heating rate of 5℃ / min and kept at this temperature for 10min; finally, the temperature was decreased to below 400℃ at a cooling rate of 5℃ / min, and then cooled with the furnace. f / SiC composite material-GH536 alloy brazed joint.

[0033] The SiC obtained in Example 3 was tested using an electronic universal testing machine. f The room temperature shear strength test of the brazed joint of / SiC composite material and GH536 alloy was carried out. The shear strength of the joint was calculated according to the maximum load. The average value of five samples was taken after continuous testing. The average room temperature shear strength of the brazed joint was 132MPa.

[0034] The SiC obtained in Example 3 was tested using a high temperature shear tester. f The shear strength of the brazed joint of / SiC composite material-GH536 alloy at 800℃ was 76MPa after continuous testing of five samples and the average value was taken.

[0035] Finally, it should be noted that the above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several modifications and equivalent substitutions can be made without departing from the principles of the present invention. These modifications and equivalent substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A SiC f A brazing connection method for SiC composite materials and metals, characterized in that: The following steps are involved: Step 1: Use micro-CT to examine SiC f / SiC composite materials were three-dimensionally reconstructed to clarify SiC f Size and SiC f and SiC matrix distribution; Step 2: Polishing SiC f The surface of the brazing surface of the / SiC composite material was then observed under an optical microscope to mark the continuous SiC matrix and SiC f / SiC composite material defect area and SiC parallel to the surface to be brazed f The area serves as a processing area; Step 3: Use water-guided laser processing to process a conical hole array in the processing area marked in step 2 to optimize the SiC f / SiC composite material surface structure to be brazed; Step 4: Using a laser etching method, a conical interlocking structure corresponding to the conical hole array in step 3 is processed on the metal surface to be brazed; Step 5: Process the SiC f / Pre-weld treatment of SiC composite materials and metals; Step 6: Apply solder paste evenly to SiC f The conical hole area of ​​the surface to be brazed of the SiC / SiC composite material is assembled with the surface to be brazed of the metal and the surface to be brazed of the composite material, and then vacuum brazing is performed.

2. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: Step 2 Use 240#~800# silicon carbide sandpaper to polish. f / SiC composite material surface roughness Ra≤0.8μm.

3. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: In step 3, the processing depth of the processing area is ≤1mm, and the processing inner wall roughness Ra is ≤1.6μm.

4. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: In step 3, the bottom diameter of the conical holes is 0.1 mm to 0.3 mm, and they are arranged in a square array with a density of 10 to 20 conical holes per square centimeter.

5. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: Step 4 SiC f The conical interlocking structure gap between the / SiC composite material and the metal is 0.1mm~0.2mm, and the milling surface roughness Ra≤0.8μm.

6. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: The specific method of pre-welding treatment in step 5 is to process the SiC f The SiC / SiC composite material and metal were immersed in acetone respectively, ultrasonically cleaned for 10 min to 15 min, and then blown dry for use.

7. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: After the metal surface to be brazed and the composite surface to be brazed are assembled in step 6, the assembly is placed in an Al2O3 ceramic tooling, and then a uniform pressure of 5KPa to 10KPa is applied to the assembly using a ceramic block.

8. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: The preparation method of the solder paste in step 6 is to mix the solder alloy powder and the auxiliary agent and stir them evenly; the solder alloy powder is selected according to the metal type, including Ni-Cr-Si-B-Ti, Pd-Cu-Ti, Au-Ni-Ti, Cu-Ni-Ti, Ti-Zr-Cu-Ni and Ti-V-Cr.

9. The SiC according to claim 1 f A brazing connection method for SiC composite materials and metals, characterized in that: The specific method of vacuum brazing in step 6 is: place the assembly in a vacuum brazing furnace and evacuate the furnace until the vacuum degree is ≤5×10 -5 Start heating after Pa, increase the temperature to 200℃~300℃ at a heating rate of 5℃ / min~10℃ / min, and keep it warm for 10min~20min, then increase the temperature to 100℃~150℃ at a heating rate of 10℃ / min~20℃ / min, and keep it warm for 20min~30min, then increase the temperature to brazing temperature at a heating rate of 3℃ / min~5℃ / min, and keep it warm for 10min~40min; then cool it to below 400℃ at a cooling rate of 5℃ / min~10℃ / min, and then cool it with the furnace.

10. The SiC according to claim 9 f A brazing connection method for SiC composite materials and metals, characterized in that: The brazing temperature is 10°C to 50°C higher than the liquidus of the brazing alloy.

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