Preparation method and platform for carbon composite brazing layer and its application in brazing ceramic-metal dissimilar materials

Abstract

This invention relates to a method for preparing a carbon composite solder layer and a method for brazing ceramic-metal dissimilar materials using the same. The preparation of the carbon composite solder layer includes: constructing a carbon pattern; directly writing carbon of different shapes and forms on a solder sheet to obtain a patterned carbon composite solder preform; heating and drying the carbon composite solder preform; placing carbon composite solder layers of the same size between a ceramic and a metal sheet, then clamping and positioning them, and brazing them together in a vacuum brazing furnace. This invention uses directly written carbon composite solder, which can effectively reduce the residual stress of the ceramic-metal brazed joint and improve the toughness of the joint.

Description

Technical Field

[0001] This invention relates to a method and platform for preparing a carbon composite brazing layer and a method for brazing ceramic-metal dissimilar materials, belonging to the field of dissimilar material brazing technology. Background Technology

[0002] Brazing, a welding process, refers to a method of joining metals by simultaneously heating a filler metal (whose melting point is lower than that of the workpiece) and the workpiece to the filler metal's melting temperature, using the liquid filler metal to fill the gaps in the solid base material. Brazing is one of the most common methods for joining ceramics and metals; however, the significant difference in their coefficients of thermal expansion and modulus of elasticity can lead to thermal mismatch, severely affecting the strength and other properties of the joint.

[0003] Among the methods to improve the mechanical properties of ceramic and metal joints and reduce residual stress in joints, the use of composite brazing filler metal and low-expansion or plastic intermediate layer are commonly used measures.

[0004] Chinese Patent Publication No. CN108672965B discloses a method for alleviating residual stress in ceramic-metal brazed joints. It uses a superplastic titanium alloy sheet with a thermal expansion coefficient between that of the ceramic and metal to be brazed as a transitional intermediate layer to mitigate residual stress. However, titanium is highly reactive, and adding excessive titanium can lead to a large amount of intermetallic compounds in the weld microstructure, deteriorating joint performance. Chinese Patent Publication No. CN112756727B discloses a method for enhancing the reduction resistance of brazed joints using a graphene sponge barrier layer. This method involves cutting graphene sponge into thin sheets, i.e., graphene sheets added externally to the brazing filler metal sheet. In other words, it is not prepared on the brazing filler metal, limiting its application shape. Chinese Patent Publication No. CN103341674B discloses a graphene-assisted brazing method for ceramic matrix composites and metal materials. This method involves growing a graphene layer on the surface of the ceramic matrix using chemical vapor deposition. The chemical vapor deposition process is complex and requires extensive parameter control.

[0005] Considering the diverse shapes and sizes of ceramic samples, simply growing carbon materials on the ceramic surface is insufficient to meet the requirements of flexible, automated, and efficient brazing production methods, and it is difficult to achieve the desired control over graphene thickness, growth area, growth scale, and patterning. Therefore, it is necessary to develop a highly automated carbon composite brazing filler metal capable of producing millimeter, micrometer, and nanometer-sized carbon composites of various shapes and morphologies in a single step on a brazing filler metal sheet, thereby achieving high-strength and high-toughness brazing connections between ceramics and metals. Summary of the Invention

[0006] This invention provides a method for preparing a carbon composite solder layer, a method for brazing ceramic-metal dissimilar materials using the same method, and a platform for preparing a carbon composite solder layer to solve the technical problem.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a method for preparing a carbon composite solder layer, comprising the following steps: constructing carbon patterns; directly writing carbon of different shapes and forms on a solder sheet to obtain patterned carbon composite solder preforms; heating and drying the carbon composite solder preforms to obtain a carbon composite solder layer.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the direct-write material is a carbon-based ink.

[0010] Furthermore, in the step of directly writing carbon of different shapes and forms on the solder sheet, the polymer in the direct-writing carbon-based ink is simultaneously laser-induced to prepare graphene.

[0011] By adjusting the laser parameters and processing parameters during the direct writing process, polymers containing aromatic functional groups in the ink can be laser-induced to prepare three-dimensional graphene structures, achieving control and preparation of carbon morphology and shape. Specific laser parameters include using a semiconductor laser with a wavelength of 504nm-808nm as the direct writing light source and a laser power of 0.7W-1.2W. Specific processing parameters can be selected as follows: laser wavelength 504nm, laser power 0.7W; 808nm, 1.2W; direct writing speed can be selected as 3mm / s-5mm / s, ink flow rate can be 10mm / s-50mm / s, laser defocusing degree 0.0mm±2.5mm, and step size 0.5mm.

[0012] The laser beam is guided through a convex lens and reflected to form a path, which is then focused onto the carbon-based ink using a 10× lens as needed. This ensures that the thickness and width of the graphene required for direct writing and laser-induced formation are met, and that the morphology and shape of the carbon are well controlled.

[0013] Furthermore, the carbon in the carbon-based ink includes one or more of graphene, graphene oxide, and carbon nanotubes.

[0014] Furthermore, the direct writing method for preparing carbon of different shapes and forms on the solder sheet is driven by CAD graphics. Because the direct writing carbon method of this invention is controlled by CAD software, the carbon graphic drawing operation is more flexible. Different patterns and sizes of carbon composite solder layers can be drawn according to specific needs, solving the problem that traditional carbon materials can only be added through coating, printing, and solder mixing.

[0015] The present invention also provides a method for brazing ceramic-metal dissimilar materials, comprising preparing a carbon composite brazing layer by the above-described method for preparing carbon composite brazing material, placing carbon composite brazing layers of the same size between ceramic and metal sheets, then clamping and positioning them, and performing brazing connection in a vacuum brazing furnace.

[0016] Specifically, the metallic materials can be selected from TC4 titanium alloy or GH3536 high-temperature alloy, and the ceramic materials can be selected from carbon fiber reinforced ceramic matrix composites or SiC fiber reinforced SiC matrix composites.

[0017] Before brazing, the surfaces of ceramic and metal materials to be brazed need to be cleaned and treated, welding process parameters need to be set, and the brazing equipment needs to be run. Cleaning and treatment can be done by ultrasonic cleaning in anhydrous ethanol to remove surface impurities. The brazing parameters can be set as follows: heating program of 35-40 minutes to 830℃-880℃, holding program of 830℃-880℃ for 5 minutes, and cooling program of 5-6 hours from 830℃-880℃ to room temperature.

[0018] This invention also provides a platform for preparing carbon composite solder layers, comprising a computer terminal equipped with CAD graphics driving software, a base, a direct-write mounting bracket, a direct-write operation controller, an X-axis moving mechanism, a Y-axis guiding mechanism, a Z-axis guiding mechanism, a solder pad placement platform, and a direct-write assembly. The lower end of the direct-write mounting bracket is fixed to the base; the Y-axis guiding mechanism is mounted on the base; the X-axis moving mechanism is mounted on the upper end of the direct-write mounting bracket, and the Z-axis guiding mechanism is fixed to the moving end of the X-axis guiding mechanism; the direct-write assembly is fixedly or slidably connected to the Z-axis guiding mechanism; the solder pad placement platform is slidably connected to the Y-axis guiding mechanism; the computer terminal is communicatively connected to the direct-write operation controller; and the direct-write operation controller is electrically connected to the X-axis moving mechanism, the Y-axis guiding mechanism, and the Z-axis guiding mechanism.

[0019] Furthermore, the solder sheet placement platform has a suction cup; the direct writing component is an ink injector, and the ink injector can control the ink output amount through the air pressure of the dispensing machine.

[0020] The beneficial effects of this invention are: the use of direct-write carbon composite brazing filler metal can effectively reduce the residual stress in ceramic-metal brazed joints and improve the toughness of the joint. Specifically, it allows for the one-step manufacture of carbon composite brazing filler metals of various shapes and forms through direct-write technology, thereby leveraging the reinforcing and toughening effects of carbon materials in ceramic-metal brazed joints. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the platform structure for preparing the carbon composite solder layer according to the present invention;

[0022] Figure 2 A schematic diagram of patterned carbon composite solder drawn by an ink syringe in the platform for preparing the carbon composite solder layer of this invention;

[0023] Figure 3 This is a schematic diagram of the brazing assembly of the carbon composite brazing layer with ceramic and metal substrates according to the present invention;

[0024] Figure 4 This is a schematic cross-sectional view of the carbon / carbon composite ceramic and titanium alloy joint connected by a carbon composite brazing layer according to the present invention.

[0025] Figure 5 This is a schematic diagram of the process for brazing ceramic-metal dissimilar materials according to the present invention.

[0026] Figure 6 This is a schematic diagram showing the shear strength test results of the joint between the carbon-based composite brazing layer and the titanium alloy using the present invention.

[0027] Figure 7 The carbon composite solder layer prepared by the direct writing method of the present invention.

[0028] The attached diagram lists the components represented by each number as follows:

[0029] 1. Carbon graphics, 2. Computer terminal, 3. Direct write operation controller, 4. X-axis movement mechanism, 5. Y-axis guiding mechanism, 6. Solder sheet, 7. Solder sheet placement platform, 8. Carbon-based ink, 9. Direct write assembly, 10. Direct write mounting bracket, 11. Ceramic base material, 12. Metal base material, 14. Carbon composite solder layer, 15. Graphene, 16. Titanium alloy, 17. Carbon / carbon composite material. Detailed Implementation

[0030] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0031] like Figure 1 As shown, a platform for preparing a carbon composite solder layer according to the present invention includes a computer terminal 2 equipped with CAD graphics driving software, a base, a direct-write mounting bracket 10, a direct-write operation controller 3, an X-axis moving mechanism 4, a Y-axis guiding mechanism 5, a Z-axis guiding mechanism 9, a solder pad placement platform 7, and a direct-write assembly 9. The lower end of the direct-write mounting bracket 10 is fixed to the base; the Y-axis guiding mechanism is mounted on the base; the X-axis moving mechanism is mounted on the upper end of the direct-write mounting bracket 10, and the Z-axis guiding mechanism is fixed to the moving end of the X-axis guiding mechanism; the direct-write assembly is slidably connected to the Z-axis guiding mechanism; the solder pad placement platform is slidably connected to the Y-axis guiding mechanism; the computer terminal is communicatively connected to the direct-write operation controller; and the direct-write operation controller is electrically connected to the X-axis moving mechanism, the Y-axis guiding mechanism, and the Z-axis guiding mechanism.

[0032] The solder pad placement platform 7 may have a suction cup; the direct writing component 9 may be an ink injector.

[0033] like Figure 2As shown, the process of preparing carbon composite solder layer with carbon-based ink involves directly writing carbon patterns 1 of different shapes and forms on solder sheet 6 to obtain carbon composite solder preform. The carbon composite solder preform is then heated and dried to obtain carbon composite solder layer 13.

[0034] like Figure 3 The diagram shows the assembly of a carbon composite brazing filler layer with ceramic and metal substrates. A carbon composite brazing filler layer of the same size is placed between the ceramic and metal sheets, then clamped and positioned, and brazed in a vacuum brazing furnace. Figure 4 The cross-section of the carbon / carbon composite ceramic and titanium alloy joint connected by the carbon composite solder layer in Embodiment 1 of the present invention shows that the graphene foam structure is almost completely present in the weld seam. There are no defects such as collapse, disappearance or unfilling of the graphene foam. This also proves that the graphene foam formed by direct writing on the solder sheet does exist between the weld seams after welding and forms a good filling and metallurgical bond with the solder.

[0035] Example 1

[0036] The metal material chosen is TC4 titanium alloy, with dimensions of 15mm × 15mm × 2mm; the ceramic material is carbon fiber reinforced ceramic matrix composite (referred to as carbon / carbon composite material), with dimensions of 10mm × 10mm × 5mm; the solder sheet is commercial Ag-Cu-Ti solder, cut to 10mm × 10mm × 0.2mm. Commercial carbon-based ink is used for direct writing, employing a carbon composite solder layer preparation platform. The direct writing speed is set to 5mm / s, with the ink flow rate selectable within the range of 10mm / s-50mm / s; in this embodiment, 20mm / s is used.

[0037] The specific implementation steps are as follows:

[0038] Using CAD software, a striped carbon pattern 1 is drawn for carbon pattern preparation, with a stripe spacing of 1 mm and a length of 15 mm. The drawn image file is imported into the direct writing operation controller 3 via computer 2, and the parameters of the X-axis 4 and Y-axis 5 travel trajectory of the worktable are set. The sheet-shaped AgCuTi solder 6 is placed above the suction cup 7 of the solder sheet placement platform 10, and is fixed in the center of the solder sheet placement platform with a vacuum suction cup to ensure that the solder sheet is flat. The syringe 9 containing carbon-based ink 8 is installed on the Z-axis guide mechanism above the solder sheet placement platform and its position is fixed. The syringe is moved in the X-axis 4 and Y-axis 5 directions through the worktable, and the ink ejection outlet is calibrated to the starting point of the area to be directly written.

[0039] After the relative positions of each component of the direct writing three-coordinate moving stage are determined, the direct writing system is started, and the ink is uniformly extruded from the syringe by the air pressure of the dispensing machine. At the same time, the laser is turned on. A semiconductor laser with a wavelength of 504nm is selected as the direct writing light source, and the laser power is selected as 0.7W. The laser is focused onto the direct writing ink through a lens.

[0040] After completing the pattern drawing on the solder sheet, the solder sheet with the drawn pattern is quickly and stably placed in a vacuum oven and dried at 200℃ for 5 minutes. Carbon composite solder prepared using direct writing is shown below. Figure 3 As shown.

[0041] The prepared carbon composite brazing filler metal 15 is prepared according to... Figure 4 The assembly of the sample to be soldered is shown in the schematic diagram. Among them, 11 is carbon fiber reinforced ceramic base material, 12 is titanium alloy base material, 13 is Ag-Cu-Ti solder sheet, 14 is a direct-written carbon pattern, and 15 is carbon composite solder.

[0042] The assembled samples to be welded are fixed and clamped using a high-temperature resistant positioning fixture.

[0043] After opening the brazing furnace door, place the sample to be brazed onto the working platform inside the brazing furnace.

[0044] Control the water pump, air pump, and control cabinet switches:

[0045] Specifically: Open the rotary vane pump and the roughing valve; once the vacuum gauge displays 10 Pa, open the fore-stage valve; open the diffusion pump, close the roughing valve, and then open the main pumping valve; set the brazing operation program: a 40-minute heating program to 900℃, a 5-minute holding program at 900℃, and a 6-hour cooling program from 900℃ to room temperature; the vacuum gauge reading should be 3 × 10⁻⁶ Pa. -3Pa Then, turn on the heating button and run the program; after the brazing is completed, wait for the inside of the furnace to return to room temperature, and then take out the ceramic metal sample welded with carbon composite brazing filler metal.

[0046] Completing the above steps completes the entire process of direct-write preparation of carbon composite solder and its application in brazing dissimilar ceramic and metal materials. The cross-section of the joint between the carbon / carbon composite material and the titanium alloy is shown below. Figure 5 As shown. This process employs a ceramic dissimilar material brazing method based on direct writing preparation of carbon composite solder. The specific process is as follows: Figure 5 As shown.

[0047] Figure 6The shear strength analysis of the brazed joints of TC4 titanium alloy and carbon / carbon composite materials is shown, comparing the joint strength with that using a carbon composite brazing filler layer. As the brazing temperature increased from 880℃ to 920℃, the joint strength changed accordingly, but the joint with carbon composite brazing filler consistently showed a higher shear strength than the joint without a carbon composite brazing filler layer. At a brazing temperature of 900℃, the joint strength reached a maximum of 81 MPa, twice that of the joint without a carbon composite brazing filler layer, and under the same conditions, 1.5 times that of the existing technology using graphene sponge sheets.

[0048] Example 2

[0049] In this embodiment, the metal material selected is GH3536 high-temperature alloy, with dimensions of 15mm × 15mm × 2mm; the ceramic material selected is SiC fiber-reinforced SiC matrix composite material (SiCf / SiC), with dimensions of 10mm × 10mm × 5mm; the solder selected is commercially available Ag-Cu sheet solder, cut to dimensions of 10mm × 10mm × 0.2mm. Commercially available carbon ink is used for direct writing, and a laser direct writing system is employed with a writing speed of 3mm / s, of which the carbon ink flow rate is 10mm / s.

[0050] The specific implementation steps are as follows:

[0051] Various carbon graphics were drawn using CAD software;

[0052] Import the drawn image file into the laser direct writing operation control system and set the parameters for the travel trajectory of the dual-axis traveling table.

[0053] Place the sheet-shaped AgCuTi solder above the laser direct writing three-coordinate moving stage, and fix it in the center of the stage with a vacuum chuck, ensuring the solder sheet is flat. Install the syringe containing carbon ink into the fixture above the work platform and fix its position, calibrating the carbon ink extrusion nozzle to the starting point of the area to be directly written;

[0054] After the relative positions of all components of the laser direct-writing three-coordinate moving stage are determined, the direct-writing system is started. Carbon ink is uniformly and finely extruded from the syringe using the air pressure control of the dispensing machine, achieving uniform direct writing on the solder sheet. Simultaneously, the laser is activated, using an 808nm semiconductor laser as the direct-writing light source, with a laser power of 1.2W. The laser path is formed by reflection adjustment through a convex lens, and then focused onto the carbon-based ink as needed using a 10× lens.

[0055] After laser direct writing is completed, the solder pad is rinsed with deionized water to remove residual and splashed carbon ink. This allows for the preparation of carbon composite solder pads with various laser direct writing patterns, such as... Figure 7 As shown.

[0056] The prepared carbon composite brazing filler metal is prepared according to... Figure 4 Assembly is performed as shown in the diagram, using high-temperature resistant positioning fixtures for secure clamping. After opening the brazing furnace door, the sample to be brazed is placed on the work platform inside the brazing furnace for brazing.

[0057] Brazing parameter settings: heating program is 35 minutes to 830℃, holding program is 830℃ for 5 minutes, cooling program is 5 hours from 830℃ to room temperature.

[0058] Completing the above steps completes the entire process of preparing carbon composite solder by direct writing and applying it to the brazing of ceramics and metals, dissimilar materials. This process employs a ceramic dissimilar material brazing technique based on the preparation of carbon composite solder using laser direct writing technology.

[0059] Shear strength analysis of brazed joints of GH3536 high-temperature alloy SiCf / SiC composite material revealed that when the brazing temperature was 900℃, the joint strength reached a maximum of 87MPa, which is 2.3 times the strength of joints without carbon composite brazing filler metal and 1.7 times that of existing graphene sponge sheet brazed joints.

[0060] The above description is merely a preferred embodiment and preferred implementation of the present invention, and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a carbon composite solder layer, characterized by The method comprises the following steps: constructing a carbon pattern; preparing carbon with different shapes and morphologies on a filler sheet by direct writing to obtain a patterned carbon composite filler preform; heating and drying the carbon composite filler preform to obtain a carbon composite filler layer; wherein in the step of preparing carbon with different shapes and morphologies on a filler sheet by direct writing, a polymer containing an aromatic functional group in the direct writing carbon-based ink is simultaneously prepared into three-dimensional graphene by laser induction; a semiconductor laser with a laser selection wavelength of 504 nm-808 nm is used as a direct writing light source, and a laser power selection is 0.7 W-1.2 W; the laser forms a path via a convex lens and reflection adjustment, and then a 10x lens is used for focusing on the direct writing ink as needed.

2. The method of claim 1, wherein the carbon composite brazing material layer is prepared by the steps of: The carbon in the carbon-based ink comprises one or more of graphite, carbon black, and carbon fiber. ​ 3. The method of claim 1, wherein the carbon composite brazing material layer is prepared by the steps of: The direct writing method for preparing carbon with different shapes and morphologies on a filler sheet is driven by a CAD pattern. ​ 4. A method of brazing a ceramic-metal dissimilar material, characterized by, The carbon composite filler layer prepared by the preparation method of the carbon composite filler in any one of claims 1 to 3 is placed between ceramic and metal sheets of the same size, clamped and positioned, and then subjected to brazing connection in a vacuum brazing furnace.

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