Method for joining an alloy metal to a cf / sic composite

Abstract

The application discloses a kind of alloy metal and Cf / SiC composite material's connecting method, comprising the following steps: S1, respectively to alloy metal workpiece and Cf / SiC composite material workpiece surface is carried out oil removal cleaning;S2, to the welding surface of Cf / SiC composite material workpiece is selectively ablated using laser processing;Then the welding surface of alloy metal workpiece is sandblasting roughening treatment and laser cleaning treatment;S3, using cold spraying process deposition CuTi-W-Ni composite solder layer;S4, using laser beam to the welding surface of alloy metal and the welding surface of Cf / SiC composite material is locally preheating treatment;S5, after preheating treatment, workpiece is vacuum brazing;The alloy metal includes one of nickel-based superalloy or titanium alloy.The application guarantees sufficient connecting strength, significantly reduces joint residual stress, inhibits harmful brittle phase, and has good process stability and engineering applicability.

Description

Technical Field

[0001] This invention relates to the technical field of alloy materials, specifically a method for joining alloy metals with Cf / SiC composite materials. Background Technology

[0002] Carbon fiber reinforced silicon carbide ceramic matrix composites (Cf / SiC) have become ideal materials for aerospace hot-end components due to their low density, high specific strength, and excellent high-temperature performance. To manufacture lightweight composite components, it is often necessary to reliably bond them with metals such as GH3536 nickel-based superalloys and TC4 titanium alloys. However, there are significant differences in their physicochemical properties: Cf / SiC has strong surface chemical inertness and poor wettability, and its coefficient of thermal expansion is severely mismatched with that of the metals, leading to weak interfacial bonding, high residual stress, and easy formation of brittle phases during bonding.

[0003] Existing technologies have made various attempts to improve joint strength, but all have limitations. For example, traditional vacuum brazing directly uses brazing foil for overall heating and connection, which is simple in process but has prominent problems. The brazing filler metal is difficult to wet and spread on the Cf / SiC surface, which easily leads to defects; the overall heating heat input is large, resulting in a sharp increase in thermal stress between dissimilar materials, often exceeding 200 MPa, which can easily cause cracking, and a continuous brittle intermetallic compound layer is easily formed at the interface, which seriously damages the mechanical properties of the joint. Its room temperature and high temperature strength are usually lower than 45 MPa and 30 MPa, respectively, which is difficult to meet the requirements of high-end equipment.

[0004] Patent CN115213583A discloses a brazing method for joining SiCf / SiC composite materials to metal. This method identifies weak areas in the SiCf / SiC composite material through three-dimensional reconstruction using micro-CT and performs customized drilling using a water-guided laser, while simultaneously fabricating corresponding interlocking structures on the metal surface. This method significantly improves joint strength through precise mechanical interlocking. However, this technology relies on complex micro-CT scanning and path planning, resulting in a cumbersome and costly process, and it fails to fundamentally solve the problems of high thermal stress and brittle phase control during brazing.

[0005] In another patent, CN106736030A, a solder and its application method in joining C / SiC composite materials with metal are described. This method addresses wetting and stress issues by altering the surface properties of the materials or employing a high-performance solder system. The C / SiC and metal surfaces are treated with a K2ZrF6 solution to improve wettability. Subsequently, a Cu-Cr-Zr-Ni-Ti mixed powder of a specific composition is used to perform surface metallization infiltration on the C / SiC. Finally, the connection is achieved through vacuum hot pressing. This method can achieve extremely high connection strength. However, its process is complex, involving multiple steps such as embedding, metal infiltration, and secondary processing. It has poor adaptability to component shapes, and the high-temperature hot pressing process also introduces significant heat-affected zones and residual stress risks.

[0006] In summary, current technological approaches present a dilemma where high strength and low damage are difficult to achieve simultaneously. While traditional improved brazing processes strive for simplification, they have significant shortcomings in terms of strength, residual stress control, and high-temperature reliability. Especially in the context of pursuing long-term high-temperature service reliability for aerospace components, how to simultaneously achieve high strength, low residual stress, high interface reliability, and good process adaptability remains a pressing and unresolved technical challenge in this field.

[0007] Therefore, there is an urgent need in the field for a novel joining method that can comprehensively solve the above problems, while ensuring sufficient joining strength, significantly reducing residual stress in the joint, suppressing harmful brittle phases, and possessing good process stability and engineering applicability. Summary of the Invention

[0008] This application provides a method for joining an alloy metal with a Cf / SiC composite material, which significantly reduces residual stress in the joint and suppresses harmful brittle phases while ensuring sufficient joint strength, and has good process stability and engineering applicability.

[0009] This application provides a method for joining an alloy metal and a Cf / SiC composite material, comprising the following steps: S1, degreasing and cleaning the surfaces of the alloy metal workpiece and the Cf / SiC composite material workpiece respectively; S2, selectively ablating the surface to be welded on the Cf / SiC composite material workpiece using a laser to form a protruding microstructure on the surface to be welded; then, sequentially performing sandblasting roughening treatment and laser cleaning treatment on the surface to be welded on the alloy metal workpiece; S3, depositing a CuTi-W-Ni composite brazing filler layer on the treated alloy metal surface to be welded using a cold spraying process; S4, performing local preheating treatment on the alloy metal surface to be welded with the deposited composite brazing filler layer and the Cf / SiC composite material surface to be welded using a laser beam; S5, assembling the preheated workpiece and placing it in a vacuum brazing furnace for vacuum brazing; wherein the alloy metal includes one of a nickel-based high-temperature alloy or a titanium alloy.

[0010] By adopting the above technical solutions, the present application specifically employs steps such as laser microstructure fabrication, cold spraying, laser preheating, and vacuum brazing to achieve the connection between alloy metal and Cf / SiC composite material.

[0011] Laser ablation addresses the surface inertness of Cf / SiC by utilizing the difference in ablation rates between the laser and the SiC matrix to selectively remove part of the matrix, causing the carbon fibers to protrude and providing strong mechanical anchoring force for subsequent bonding.

[0012] Cold spray deposition addresses the conflict between solder layer quality and heat input. CuTi-W-Ni powder is deposited at high speed through impact deposition in a solid state at 400-550℃, forming a high-density, oxidation-free solder pre-layer. The W powder is embedded in solid particles to prepare for subsequent suppression of brittle phases.

[0013] Laser localized preheating addresses thermal stress issues. Precise preheating using oscillating scanning reduces the temperature difference between dissimilar materials during subsequent brazing, thereby significantly reducing residual stress caused by thermal expansion coefficient mismatch.

[0014] Vacuum brazing achieves the final metallurgical bond. In a vacuum environment, the brazing filler metal melts, and the active Ti element diffuses to the Cf / SiC interface and reacts with the C fibers to form a TiC reinforcing phase. Solid W particles inhibit the continuous growth of brittle intermetallic compounds, and Ni element improves wettability.

[0015] Preferably, in step S2, the parameters for the laser selective ablation are: laser power 800-1200W, scanning speed 0.8-1.5m / min, spot diameter 0.5-0.8mm, and overlap rate 40-60%.

[0016] Preferably, in step S2, the height of the protruding microstructure formed after the Cf / SiC composite workpiece is ablated is 20-45 μm, and the surface roughness Ra is 3.2-4.5 μm; after the alloy metal workpiece is sandblasted and laser cleaned, the surface roughness Ra of the alloy metal surface to be welded is 1.2-3.1 μm.

[0017] Preferably, in step S3, the CuTi-W-Ni composite solder layer is formed by cold spraying a mixture of Cu-Ti alloy powder, W powder and Ni powder; the mass ratio of each component is Cu-Ti alloy powder:W powder:Ni powder = 100:5-10:3-8.

[0018] Preferably, the Cu-Ti alloy powder contains 25-35% Ti by mass and has a particle size of 20-50 μm; the W powder has a particle size of 5-20 μm; and the Ni powder has a particle size of 20-40 μm.

[0019] By adopting the above technical solution, Cu-Ti alloy is used as the brazing filler metal matrix. Ti is the active element, used to react with C in Cf / SiC during brazing to form a TiC reinforcing phase, achieving metallurgical bonding. The specific Ti content ensures sufficient activity without excessive formation of brittle phases. W powder is one of the key innovative components, with a particle size of 5-20μm ensuring solid embedding during cold spraying. During brazing, W particles do not melt and are dispersed in the brazing seam, effectively disrupting and inhibiting the continuous network growth of brittle intermetallic compounds. Ni powder plays a role in improving the wettability of the brazing filler metal matrix and adjusting the melting point and mechanical properties of the brazing filler alloy.

[0020] This application ensures the deposition efficiency of the cold spraying process and the uniformity of the solder layer by using a specific particle size range. Powders of different particle sizes have different acceleration and deposition behaviors in the airflow, and the optimized ratio can obtain a dense and uniform preform layer.

[0021] Preferably, in step S3, the parameters of the cold spraying process are as follows: a mixture of He and N2 is used as the carrier gas, the volume ratio of He to N2 is 3:1, the gas pressure is 3.0-4.5MPa, the gas temperature is 400-550℃, and the spraying distance is 80-100mm; the thickness of the deposited composite solder layer is 80-150μm, and the density is ≥99%.

[0022] Preferably, in step S4, the local laser preheating treatment uses a fiber laser; the process parameters for the preheating treatment are: laser power 1500-2000W, scanning speed 0.5-1.0m / min, spot diameter 0.5-1.0mm, oscillation amplitude 0.3-0.6mm, oscillation frequency 40-60Hz; and the preheating temperature is controlled within the range of 400-550℃.

[0023] Preferably, in step S5, the process parameters for vacuum brazing are: vacuum degree ≤ 5 × 10⁻⁶. -4 Pa is heated to 950-1050℃ at a heating rate of 4-6℃ / min and held for 30-60min, then furnace cooled to room temperature at a rate of 3-5℃ / min.

[0024] One or more technical solutions provided in this application have at least the following technical effects or advantages: 1. This invention constructs protruding microstructures on the Cf / SiC surface, forming a dual interfacial bonding mechanism of micron-level mechanical interlocking and metallurgical reaction with the high-density solder layer deposited by cold spraying. During the vacuum brazing stage, the active Ti elements in the solder layer fully diffuse to the Cf / SiC interface, reacting with C fibers to generate a dispersed TiC reinforcing phase in situ; W particles inhibit the continuous growth of brittle intermetallic compounds at the interface through a pinning effect.

[0025] 2. This invention employs cold spraying and low-temperature solid-state deposition to prepare the solder layer, avoiding thermal damage to the substrate caused by high-temperature cladding; local laser preheating precisely heats only the solder layer and interface area; and a slow furnace cooling rate is used after vacuum brazing. These three measures work synergistically to reduce residual stress at the joint, effectively preventing interface cracking caused by mismatch in the thermal expansion coefficients of dissimilar materials.

[0026] 3. This invention employs a cold spraying process to deposit a CuTi-W-Ni composite solder layer. The deposition process involves solid-state plastic deformation, eliminating the risk of oxidation and burn-off. This results in increased solder layer density and precise, controllable thickness. Local laser preheating utilizes oscillating scanning, ensuring high temperature uniformity and preventing localized melting and loss of the solder layer, thus guaranteeing its integrity before vacuum brazing.

[0027] 4. The method described in this invention has no special requirements on the shape of Cf / SiC composite components. Planar, curved, and complex irregular surfaces can all achieve high-quality bonding by adjusting the trajectory of the cold spray gun and the laser scanning path. It is widely applicable to nickel-based superalloys or titanium alloy substrates, and can bond both nickel-based superalloys such as GH3536 and titanium alloys such as TC4. This method has the potential for automated integration and is suitable for the large-scale manufacturing of high-temperature structural components for aerospace applications. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a partial microstructure detail image of the brazed workpiece of TC4 titanium alloy and Cf / SiC composite material in Example 1 of this application, taken under a scanning electron microscope. Detailed Implementation

[0030] This application provides a method for joining an alloy metal with a Cf / SiC composite material, which significantly reduces residual stress in the joint and suppresses harmful brittle phases while ensuring sufficient joint strength, and has good process stability and engineering applicability.

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or modules not explicitly listed or inherent to such processes, methods, products, or devices. Example Example 1

[0033] Embodiment 1 of this application provides a specific joining method for joining an alloy metal and a Cf / SiC composite material. The raw materials for Embodiment 1 include TC4 titanium alloy and Cf / SiC composite material. The specific steps are as follows: S1. Surface pretreatment: Place the TC4 titanium alloy sheet with a specification of 20mm×20mm×3mm and the two-dimensional braided Cf / SiC composite material sheet in an acetone solution and perform ultrasonic cleaning for 15 minutes to remove surface oil and adhering contaminants. After removal, dry with cold air.

[0034] S2. Modification of the surface to be welded: The Cf / SiC composite material was selectively ablated using a fiber laser. The laser power was 800W, the scanning speed was 0.8m / min, the spot diameter was 0.6mm, and the overlap rate was 50%. After treatment, a microstructure composed of protruding carbon fibers was formed on the Cf / SiC surface, with a protrusion height of 20-25μm and a surface roughness Ra of 3.2μm.

[0035] The surfaces of the TC4 titanium alloy to be welded were first roughened by sandblasting using 60-mesh white corundum abrasive at a pressure of 0.5 MPa and a distance of 100 mm for 30 seconds. This was followed by laser cleaning at a laser power of 500 W, a scanning speed of 2 m / s, and a pulse width of 100 ns, repeated twice. After treatment, the surface roughness Ra of the metal was 1.2 μm.

[0036] S3. Cold spraying deposition of composite brazing filler metal layer: Cu-Ti alloy powder with a particle size of 20-50μm (Ti content 30wt%), W powder with a particle size of 5-20μm and Ni powder with a particle size of 20-40μm are mixed in a V-type powder mixer at a mass ratio of 100:5:3 for 2 hours.

[0037] A mixture of He and N2 (volume ratio 3:1) was used as the carrier gas at a pressure of 3.0 MPa and a temperature of 400 °C. The spraying distance was 80 mm, and the spray gun moving speed was 20 mm / s. A CuTi-W-Ni composite solder layer was deposited on the treated TC4 titanium alloy surface to be soldered. The thickness of the solder layer after deposition was 80 μm, and its density was determined to be 99.5% using image analysis.

[0038] S4. Localized Laser Preheating: A fiber laser is used to locally preheat the TC4 and Cf / SiC surfaces to be soldered, which have solder layers deposited on them. The laser beam adopts an ∞-shaped oscillating scanning mode, with a laser power of 1500W, a scanning speed of 0.5m / min, a spot diameter of 0.5mm, an oscillation amplitude of 0.3mm, and an oscillation frequency of 50Hz. The preheating temperature is controlled within the range of 400±10℃ using an infrared thermal imager, and the temperature difference between the surfaces to be soldered is ≤10℃.

[0039] S5. Vacuum Brazing Connection: Assemble the preheated workpieces into an overlapping structure (overlap width 5mm) and fix them with graphite clamps. Place them in a vacuum brazing furnace and evacuate to 3.2×10⁻⁶. -4 Pa. Heat to 950℃ at a rate of 5℃ / min and hold for 30 minutes. After holding, furnace cool to room temperature at a rate of 5℃ / min, with the cooling rate controlled below 3℃ / min in the 800℃ to 300℃ range.

[0040] After cooling, a brazed workpiece of TC4 titanium alloy and Cf / SiC composite material is obtained.

[0041] Figure 1 This is a partial microstructure detail of the brazed TC4 titanium alloy and Cf / SiC composite material workpiece under a scanning electron microscope in Example 1. X-ray diffraction analysis of the joint interface revealed a dispersed TiC phase. Scanning electron microscopy showed that W particles were uniformly distributed in the brazed seam, with no continuous brittle phase layer formed.

[0042] Transmission electron microscopy (TEM) observation of the joint obtained in Example 1 showed that the W particles were spherical or nearly spherical with a size of 5-15 μm and a particle spacing of 15-25 μm. No continuous brittle phase precipitation was observed around the particles. The TiC reinforcing phase was dispersed in nanoscale (20-50 nm) near the Cf / SiC interface.

[0043] The image above shows an irregular, honeycomb-like structure, which is the solidified structure formed after a solid-liquid reaction during the vacuum brazing process of the cold-sprayed CuTi-W-Ni composite solder. At the brazing temperature, the surrounding CuTi solder melts, while the W powder remains solid. These high-melting-point W particles act as heterogeneous nucleation sites during the solidification and shrinkage of the liquid solder. Therefore, the polygonal grains in the image are not the brittle phase itself, but rather α-Cu solid solution grains precipitated around the W particles. The presence of the W particles refines the grain size and prevents the formation of coarse columnar crystals.

[0044] The lower region represents the interior of the brazing seam. This area is flat, dense, and has a uniform gray tone. This indicates that the molten brazing filler metal fully fills the microstructural grooves on the Cf / SiC surface, and that no macroscopic or microscopic pores are generated within the interior due to the support and stirring effect of the W particles. The color changes in the figure represent a natural transition in the solidification structure, rather than an aggregation of brittle phases. This demonstrates that the W powder effectively diluted and dispersed the chemical reactions at the interface, preventing the continuous precipitation of brittle phases.

[0045] The brazed workpieces of TC4 titanium alloy and Cf / SiC composite material obtained in Example 1 of this application were tested and analyzed. The mechanical properties were tested by shear strength, specifically the room temperature shear strength and the 800°C high-temperature shear strength of the joint. A universal testing machine was used for the shear tests. The samples were tested at a constant temperature of 800°C and at room temperature. The shear strength was calculated by dividing the maximum shear load by the overlap area.

[0046] The test results showed that the room temperature shear strength was 81.3 MPa and the high temperature shear strength at 800℃ was 66.8 MPa. Example 2

[0047] The difference between Example 2 and Example 1 lies in the parameters of the connection method. The specific steps are as follows: S1. Surface pretreatment: Place the TC4 titanium alloy sheet with a specification of 20mm×20mm×3mm and the two-dimensional braided Cf / SiC composite material sheet in an acetone solution and perform ultrasonic cleaning for 15 minutes to remove surface oil and adhering contaminants. After removal, dry with cold air.

[0048] S2. Modification of the surface to be welded: The Cf / SiC composite material was selectively ablated using a fiber laser. The laser power was 1000W, the scanning speed was 1.0m / min, the spot diameter was 0.6mm, and the overlap rate was 50%. After treatment, a microstructure composed of protruding carbon fibers was formed on the Cf / SiC surface, with a protrusion height of 40-45μm and a surface roughness Ra of 4.5μm.

[0049] The surfaces of the TC4 titanium alloy to be welded were first roughened by sandblasting using 60-mesh white corundum abrasive at a pressure of 0.6 MPa and a distance of 100 mm for 30 seconds. This was followed by laser cleaning at a laser power of 600 W, a scanning speed of 2 m / s, and a pulse width of 100 ns, repeated twice. After treatment, the surface roughness Ra of the metal was 31 μm.

[0050] S3. Cold spraying deposition of composite brazing filler metal layer: Cu-Ti alloy powder with a particle size of 20-50μm (Ti content 30wt%), W powder with a particle size of 5-20μm and Ni powder with a particle size of 20-40μm are mixed in a V-type powder mixer at a mass ratio of 100:6:5 for 2 hours.

[0051] A mixture of He and N2 (volume ratio 3:1) was used as the carrier gas at a pressure of 4.0 MPa and a temperature of 500 °C. The spraying distance was 90 mm, and the spray gun moving speed was 20 mm / s. A CuTi-W-Ni composite solder layer was deposited on the treated TC4 titanium alloy surface to be soldered. The thickness of the solder layer after deposition was 100 μm, and its density was determined to be 99.8% using image analysis.

[0052] S4. Localized Laser Preheating: A fiber laser is used to locally preheat the TC4 and Cf / SiC surfaces to be soldered, which have solder layers deposited on them. The laser beam adopts an ∞-shaped oscillating scanning mode, with a laser power of 1800W, a scanning speed of 0.8m / min, a spot diameter of 0.8mm, an oscillation amplitude of 0.5mm, and an oscillation frequency of 50Hz. The preheating temperature is controlled within the range of 500±10℃ using an infrared thermal imager, and the temperature difference between the surfaces to be soldered is ≤10℃.

[0053] S5. Vacuum Brazing Connection: Assemble the preheated workpieces into an overlapping structure (overlap width 5mm) and fix them with graphite clamps. Place them in a vacuum brazing furnace and evacuate to a vacuum degree ≤5×10⁻⁶. -4 Pa. Heat to 980℃ at a rate of 4℃ / min and hold for 60 minutes. After holding, furnace cool to room temperature at a rate of 3℃ / min, with the cooling rate controlled below 3℃ / min in the 800℃ to 300℃ range.

[0054] After cooling, a brazed workpiece of TC4 titanium alloy and Cf / SiC composite material was obtained. Testing and analysis showed that the joint obtained in this embodiment had a room temperature shear strength of 82.5 MPa and a high-temperature shear strength of 68.2 MPa at 800℃. Example 3

[0055] The difference between Example 3 and Example 1 is that Example 3 uses a high-temperature nickel-based alloy, specifically GH3536 nickel-based high-temperature alloy sheet. The parameters of the connection method in Example 3 were adaptively adjusted, and the specific steps are as follows: S1. Surface pretreatment: Place the TGH3536 nickel-based high-temperature alloy plate with a specification of 20mm×20mm×3mm and the two-dimensional braided Cf / SiC composite material plate in acetone solution and perform ultrasonic cleaning for 15 minutes to remove surface oil and adhering contaminants. After removal, dry with cold air.

[0056] S2. Modification of the surface to be welded: The Cf / SiC composite material was selectively ablated using a fiber laser. The laser power was 1200W, the scanning speed was 1.5m / min, the spot diameter was 0.6mm, and the overlap rate was 50%. After treatment, a microstructure composed of protruding carbon fibers was formed on the Cf / SiC surface, with a protrusion height of 30-35μm and a surface roughness Ra of 3.8μm.

[0057] The surfaces of the TGH3536 nickel-based superalloy sheet to be welded were first roughened by sandblasting using 60-mesh white corundum abrasive at a pressure of 0.5 MPa and a distance of 100 mm for 30 seconds. This was followed by laser cleaning at a power of 550 W, a scanning speed of 2 m / s, and a pulse width of 100 ns, repeated twice. After treatment, the surface roughness Ra of the metal was 2.8 μm.

[0058] S3. Cold spraying deposition of composite brazing filler metal layer: Cu-Ti alloy powder with a particle size of 20-50μm (Ti content 30wt%), W powder with a particle size of 5-20μm and Ni powder with a particle size of 20-40μm are mixed in a V-type powder mixer at a mass ratio of 100:10:6 for 2 hours.

[0059] A mixture of He and N2 (volume ratio 3:1) was used as the carrier gas at a pressure of 4.5 MPa and a temperature of 550 °C. The spraying distance was 100 mm, and the spray gun moving speed was 20 mm / s. A CuTi-W-Ni composite solder layer was deposited on the treated TC4 titanium alloy surface to be soldered. The thickness of the solder layer after deposition was 120 μm, and its density was determined to be 99.2% using image analysis.

[0060] S4. Localized Laser Preheating: A fiber laser is used to locally preheat the TC4 and Cf / SiC surfaces to be soldered, which have solder layers deposited on them. The laser beam adopts an ∞-shaped oscillating scanning mode, with a laser power of 2000W, a scanning speed of 1.0m / min, a spot diameter of 1.0mm, an oscillation amplitude of 0.6mm, and an oscillation frequency of 50Hz. The preheating temperature is controlled within the range of 450±10℃ using an infrared thermal imager, and the temperature difference between the surfaces to be soldered is ≤10℃.

[0061] S5. Vacuum Brazing Connection: Assemble the preheated workpieces into an overlapping structure (overlap width 5mm) and fix them with graphite clamps. Place them in a vacuum brazing furnace and evacuate to a vacuum degree ≤5×10⁻⁶. -4Pa. Heat to 1020℃ at a rate of 6℃ / min and hold for 50 minutes. After holding, furnace cool to room temperature at a rate of 4℃ / min, with the cooling rate controlled below 3℃ / min in the 800℃ to 300℃ range.

[0062] After cooling, a brazed workpiece of nickel-based superalloy and Cf / SiC composite material was obtained. Tests showed that the joint prepared in Example 3 had a room temperature shear strength of 80.1 MPa and a high-temperature shear strength of 67.5 MPa at 800°C.

[0063] Comparative Example Comparative Example 1 Comparative Example 1 uses a traditional vacuum brazing process, specifically using TC4 titanium alloy and Cf / SiC composite material of the same specifications. The surfaces to be brazed are only cleaned with acetone, without laser microstructure creation, cold spray pre-coating, or laser preheating.

[0064] The specific process involves directly laying AgCuTi foil brazing filler metal (100μm thick), followed by vacuum brazing at 1020℃ for 30 minutes, with the vacuum level controlled to ≤5×10⁻⁶. -4 Pa. After cooling, a brazed workpiece of TC4 titanium alloy and Cf / SiC composite material is obtained.

[0065] Tests showed that the joint's room temperature shear strength was 34.2 MPa and its high-temperature shear strength at 800℃ was 19.6 MPa. Scanning electron microscopy revealed a continuous brittle compound layer at the interface, with a residual stress value of 215 MPa.

[0066] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses a simple cold spraying and vacuum brazing process.

[0067] In step S2, the Cf / SiC composite material was not selectively ablated using a fiber laser on its surface to be welded. Therefore, the Cf / SiC surface did not form a microstructure composed of protruding carbon fibers.

[0068] In step S4, the TC4 soldering surface and the Cf / SiC soldering surface with the solder layer deposited were not preheated locally using a fiber laser.

[0069] Then, in step S5, direct vacuum brazing is performed to obtain a brazed workpiece of TC4 titanium alloy and Cf / SiC composite material.

[0070] Tests showed that the joint's room temperature shear strength was 52.8 MPa, and its high-temperature shear strength at 800℃ was 36.4 MPa. The interface bonding was mainly metallurgical, with weak mechanical meshing.

[0071] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 uses cold spraying, laser microstructure fabrication, and vacuum brazing.

[0072] In step S2, the Cf / SiC composite material undergoes selective ablation of its surface to be welded using a fiber laser. This results in a microstructure composed of protruding carbon fibers forming on the Cf / SiC surface. Simultaneously, the surface of the TC4 titanium alloy to be welded is first roughened by sandblasting.

[0073] However, in step S4, the TC4 and Cf / SiC surfaces to be soldered, which have a solder layer deposited on them, were not locally preheated using a fiber laser. The Cf / SiC composite material was subjected to laser ablation, cold spraying to deposit a solder layer, and direct vacuum brazing to obtain a brazed workpiece of TC4 titanium alloy and Cf / SiC composite material.

[0074] After testing and analysis, the joint's room temperature shear strength was 63.5 MPa; its high-temperature shear strength at 800℃ was 45.7 MPa; scanning electron microscopy showed that the amount of TiC formed at the interface was small and the distribution was uneven.

[0075] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that no W powder is added to the cold spray powder in Comparative Example 4.

[0076] In step S3, a CuTi-Ni composite brazing filler layer is deposited on the TC4 titanium alloy surface to be welded. Specifically, Cu-Ti-Ni ternary powder is used, with a Cu-Ti alloy powder to Ni powder mass ratio of 100:5. The remaining steps are the same as in Example 1. Finally, a brazed workpiece of TC4 titanium alloy and Cf / SiC composite material is obtained. After testing, the joint's room temperature shear strength is 58.6 MPa, and its high-temperature shear strength at 800℃ is 41.2 MPa.

[0077] Scanning electron microscopy revealed that a continuous thick layer of brittle intermetallic compound (approximately 8-12 μm thick) was formed in the brazing seam, exhibiting a continuous layered distribution.

[0078] Based on the analysis of Examples 1-3 of this application, within a reasonable range of process parameters, the joining method of this application can stably obtain high-performance joints with room temperature shear strength exceeding 80 MPa and high temperature strength exceeding 66 MPa. Its microstructure is uniform and dense, without harmful continuous brittle phases.

[0079] Furthermore, in conjunction with the analysis of Comparative Example 1, it was found that Comparative Example 1 used traditional vacuum brazing, and its room temperature shear strength and high temperature shear strength were both lower than those of Examples 1-3, thus demonstrating the limitations of its application.

[0080] Furthermore, in Comparative Example 2, the Cf / SiC composite material in Comparative Example 2, without surface laser ablation and local laser preheating, showed a decrease in joint strength of approximately 35%. This indicates that the mechanical interlocking mechanism makes a significant contribution to improving interfacial bonding strength and effectively solves the problem of weak interfacial bonding.

[0081] Analysis of Comparative Example 3 shows that, without local laser preheating, the joint strength decreased by approximately 22%. This indicates that preheating effectively reduces the interface temperature difference and decreases the thermal stress in subsequent brazing, making it a key step in controlling residual stress.

[0082] In addition, according to the analysis in Comparative Example 4, the absence of W powder in the composite brazing filler metal resulted in a decrease in joint strength and the appearance of a continuous brittle layer at the microscopic level, leading to brittle failure. This demonstrates the core role of W particles in pinning and inhibiting the continuous growth of the brittle phase, thus solving the problem of easy formation of the brittle phase.

[0083] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0084] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0085] This specification and accompanying drawings are merely illustrative examples of this application and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Therefore, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A method for joining an alloy metal with a Cf / SiC composite material, characterized in that, Includes the following steps: S1. Degreasing and cleaning are performed on the surfaces of alloy metal workpieces and Cf / SiC composite material workpieces, respectively. S2. Selective laser ablation is performed on the surface of the Cf / SiC composite workpiece to be welded to form a protruding microstructure; then, the surface of the alloy metal workpiece to be welded is subjected to sandblasting roughening and laser cleaning in sequence. S3. A CuTi-W-Ni composite solder layer is deposited on the treated alloy metal surface to be soldered using a cold spraying process. S4. Use a laser beam to perform local preheating treatment on the alloy metal surface to be soldered with the composite solder layer deposited thereon and the Cf / SiC composite material surface to be soldered. S5. Assemble the preheated workpiece and place it in a vacuum brazing furnace for vacuum brazing. The alloy metal includes either a nickel-based superalloy or a titanium alloy.

2. The method for joining alloy metal and Cf / SiC composite material according to claim 1, characterized in that, In step S2, The parameters for the laser selective ablation are: laser power 800-1200W, scanning speed 0.8-1.5m / min, spot diameter 0.5-0.8mm, and overlap rate 40-60%.

3. The method for joining alloy metal and Cf / SiC composite material according to claim 1, characterized in that, In step S2, The height of the protruding microstructures formed after the ablation of Cf / SiC composite workpieces is 20-45 μm, and the surface roughness Ra is 3.2-4.5 μm. After sandblasting and laser cleaning, the surface roughness Ra of the alloy metal workpiece to be welded is 1.2-3.1μm.

4. The method for joining alloy metal and Cf / SiC composite material according to claim 1, characterized in that, In step S3, The CuTi-W-Ni composite solder layer is formed by cold spraying a mixture of Cu-Ti alloy powder, W powder and Ni powder; the mass ratio of each component is Cu-Ti alloy powder:W powder:Ni powder = 100:5-10:3-8.

5. The method for joining alloy metal and Cf / SiC composite material according to claim 4, characterized in that, The Cu-Ti alloy powder contains 25-35% Ti by mass and has a particle size of 20-50 μm; the W powder has a particle size of 5-20 μm; and the Ni powder has a particle size of 20-40 μm.

6. The method for joining alloy metal and Cf / SiC composite material according to claim 1, characterized in that, In step S3, the parameters of the cold spraying process are: A mixture of He and N2 is used as the carrier gas, with a volume ratio of He to N2 of 3:1, a gas pressure of 3.0-4.5 MPa, a gas temperature of 400-550℃, and a spraying distance of 80-100 mm. The thickness of the composite solder layer formed by deposition is 80-150 μm, and the density is ≥99%.

7. The method for joining alloy metal and Cf / SiC composite material according to claim 1, characterized in that, In step S4, the local laser preheating treatment uses a fiber laser; the process parameters for the preheating treatment are: Laser power 1500-2000W, scanning speed 0.5-1.0m / min, spot diameter 0.5-1.0mm, oscillation amplitude 0.3-0.6mm, oscillation frequency 40-60Hz; preheating temperature controlled within the range of 400-550℃.

8. The method for joining alloy metal and Cf / SiC composite material according to claim 1, characterized in that, In step S5, the process parameters for vacuum brazing are: vacuum degree ≤ 5 × 10⁻⁶. -4 Pa is heated to 950-1050℃ at a heating rate of 4-6℃ / min and held for 30-60min, then furnace cooled to room temperature at a rate of 3-5℃ / min.

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