A method for connecting silicon nitride / nickel-based high-temperature alloy using chemically modified composite brazing filler metal

Abstract

The application relates to a method for connecting silicon nitride / nickel-based high-temperature alloy by using a chemical modified composite filler, and relates to a welding method, in particular to a method for connecting silicon nitride / nickel-based high-temperature alloy by using a chemical modified composite filler.The application aims to solve the technical problem that the adding amount of low-expansion particles is limited due to the reaction between the particles and active element titanium in the current connecting method for connecting silicon nitride ceramic / nickel-based high-temperature alloy.The application delays the reaction with the active element Ti by carrying out copper coating treatment on different carbon sources, realizes the increase of the content of low-expansion particles in the weld, makes the connecting part free of obvious microcracks, further reduces the thermal expansion of the weld, reduces the residual stress of the joint, and improves the connecting strength of the joint.The application has the advantages of simple process, direct brazing of the ceramic and the metal without any modification treatment on the surface of the to-be-welded sample before welding, and effective connection of the ceramic and the metal by adding the intermediate layer.

Description

Technical Field

[0001] The invention relates to a welding method, in particular to a method for connecting silicon nitride / nickel-based high-temperature alloys by using a chemically modified composite brazing filler metal. Background Art

[0002] The large residual stress in the joints of dissimilar materials caused by the mismatch of thermophysical properties between the parent materials is the main problem affecting the connection performance of the joint. Silicon nitride ceramics and nickel-based high-temperature alloys are widely used in the aerospace field as excellent high-temperature materials. By comprehensively utilizing the advantages of silicon nitride and nickel-based high-temperature alloys through connection methods, their application potential can be further explored. In order to alleviate the residual stress of the joint, common methods include adding low-expansion coefficient particles, which can effectively reduce the residual stress of the joint and surface treatment of ceramics. However, the surface treatment of ceramics has the problem of complex and expensive pre-treatment, and the traditional method of adding low-expansion coefficient particles is limited in addition due to the reaction between the particles and active elements, which affects the formation of sufficient interface compounds at the ceramic interface, thereby affecting the joint performance. Summary of the Invention

[0003] The present invention aims to solve the technical problem in the current method for connecting silicon nitride ceramics / nickel-based high-temperature alloys, in which the reaction between the particles and active elements limits the amount of low expansion coefficient particles added, thereby affecting the formation of sufficient interface compounds at the ceramic interface. The present invention provides a method for connecting silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal.

[0004] The method of connecting silicon nitride / nickel-based high-temperature alloy using chemically modified composite brazing filler metal of the present invention is carried out according to the following steps:

[0005] 1. Milling copper-plated carbon powder and copper-plated titanium powder at a low speed in a planetary ball mill to obtain a uniformly mixed composite solder; the volume fraction of the copper-plated carbon powder in the composite solder powder is 5% to 25%;

[0006] 2. Clean the surface of the base material nickel-based alloy, MoCu alloy and base material silicon nitride ceramic;

[0007] 3. Using a tablet press, the composite solder prepared in step 1 and the cleaned MoCu alloy in step 2 are respectively tableted, and then a MoCu alloy sheet is placed between the two composite solder sheets to form a sandwich structure, and a binder is applied between the layers to obtain an intermediate layer solder;

[0008] Fourth, an intermediate layer of brazing filler metal and a cleaned base material of silicon nitride ceramic are sequentially placed on the cleaned base material of nickel-based alloy, and an adhesive is applied between the intermediate layer of brazing filler metal and the two base materials to obtain a workpiece to be welded;

[0009] V. The assembled workpiece to be welded in step IV is placed into a vacuum heating furnace, and heated from room temperature to 300-310 DEG C and kept for 30-35 min to ensure complete volatilization of the adhesive; then heated from 300-310 DEG C to 1000-1060 DEG C and kept for 5-20 min; finally, slowly cooled to 300-310 DEG C, and then cooled to room temperature with the furnace, to complete the brazing of the ceramic and metal; the whole process of step V is carried out under vacuum.

[0010] The present application delays the reaction with the active element Ti by copper coating treatment of different carbon sources (carbon particles, diamond micro powder, carbon fiber and multi-walled carbon nanotube), realizes the increase of the content of low-expansion particles in the weld, makes the connecting piece without obvious micro-cracks, further reduces the thermal expansion of the weld, reduces the residual stress of the joint, and improves the connecting strength of the joint.

[0011] The present application aims to obtain a ceramic-high-temperature alloy joint with good interface, and uses a composite filler to realize partial transient liquid phase connection, to obtain a silicon nitride ceramic / GH4169 alloy high-temperature joint.

[0012] The present application has simple process, and can realize direct brazing of the ceramic and the metal without any modification treatment on the surface of the workpiece to be welded before welding, and can realize effective connection of the ceramic and the metal by adding the intermediate layer. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The assembly drawing of the workpiece to be welded in step IV of test one;

[0014] Figure 2 The SEM image of the copper-plated carbon powder in step I of test two;

[0015] Figure 3 The XRD image of the copper-plated carbon powder in step I of test two;

[0016] Figure 4 The XRD image of the copper-plated carbon powder in step I of test three;

[0017] Figure 5 The SEM image of the microstructure of the silicon nitride ceramic / GH4169 alloy joint obtained in test one;

[0018] Figure 6 The SEM image of the microstructure of the silicon nitride ceramic / GH4169 alloy joint obtained in test two. DETAILED DESCRIPTION

[0019] Embodiment one: the present embodiment is a method for connecting silicon nitride / nickel-based high-temperature alloy by using a chemically modified composite filler, which is specifically carried out according to the following steps:

[0020] One, the plated copper carbon powder and plated copper titanium powder are ball milled by a planetary ball mill to obtain a uniformly mixed composite filler; the volume fraction of the plated copper carbon powder in the composite filler powder is 5% to 25%;

[0021] Two, the base material nickel-based alloy, MoCu alloy and base material silicon nitride ceramic are subjected to surface cleaning treatment;

[0022] Three, the composite filler prepared in step one and the MoCu alloy cleaned in step two are subjected to tabletting treatment by a tabletting machine, then a MoCu alloy tablet is placed between two composite filler tablets to form a sandwich structure, and adhesive is coated between the layers to obtain an intermediate layer filler;

[0023] Four, the intermediate layer filler and the base material silicon nitride ceramic cleaned are sequentially arranged on the base material nickel-based alloy cleaned, and adhesive is coated between the intermediate layer filler and the two base materials to obtain a workpiece to be welded;

[0024] Five, the assembled workpiece to be welded in step four is placed in a vacuum heating furnace, heated from room temperature to 300-310°C and kept for 30-35 min to ensure that the adhesive is completely volatilized; then heated from 300-310°C to 1000-1060°C and kept for 5-20 min; finally, slowly cooled to 300-310°C, and then cooled to room temperature with the furnace, to complete the brazing of the ceramic and the metal; the whole process of step five is carried out in vacuum.

[0025] Specific implementation method two: the difference between this implementation method and specific implementation method one is that the preparation method of the plated copper titanium powder in step one is as follows:

[0026] One, the pure titanium powder is soaked in a mixed solution of acetone and anhydrous ethanol, ultrasonic cleaned for 10-15 min to remove grease on the surface of the powder, and then sequentially filtered and dried, with a drying temperature of 70°C and a drying time of 30 min; the mass fraction of acetone in the mixed solution of acetone and anhydrous ethanol is 50%; the particle size of the pure titanium powder is 2000 mesh;

[0027] Two, SnCl2 is dissolved in deionized water, then NaOH and dilute sulfuric acid solution are sequentially added, then the powder dried in step one is added and ultrasonic oscillated for 1-3 min, and finally sequentially filtered and dried;

[0028] The dilute sulfuric acid solution is 1 mol / L;

[0029] The mass of SnCl2 to the volume of deionized water is (1-5) g:40 mL;

[0030] The mass ratio of SnCl2 to NaOH is 1:(0.4-10);

[0031] The mass ratio of SnCl2 to the volume of the dilute sulfuric acid solution is 1g:(1mL~20mL);

[0032] The mass ratio of the pure titanium powder described in step 1 to the SnCl2 described in step 2 is 1:(0.4-10);

[0033] 3. Mix the silver-based activator with purified water and stir, then add it to the dried product in step 2, mix it with ultrasound for 1 to 5 minutes, then filter and dry it in sequence at a drying temperature of 70°C for 30 minutes;

[0034] The silver-based activator is a silver ammonia solution with a concentration of 10g / L;

[0035] The mass ratio of the silver-based activator to pure water is 1:(1-5);

[0036] The volume ratio of the pure titanium powder described in step 1 to the silver-based activator described in step 3 is 1g:(20mL~25mL);

[0037] 4. Add CuSO4.5H2O, potassium sodium tartrate and EDTA-2Na to pure water and mix and stir, then add NaOH to adjust the solution to a pH of 11.5-12.5, then place in a water bath at 70°C-75°C, add formaldehyde solution dropwise, and then add the dried product in step 3, heat in a water bath at 70°C-75°C for 5-6 minutes, until the solution changes from dark blue to white, and finally filter and dry in sequence to obtain copper-plated titanium powder, the thickness of the copper plating layer being 1 μm-5 μm;

[0038] The mass fraction of the formaldehyde solution is 37%;

[0039] The volume ratio of the formaldehyde solution to pure water is 1:(25-50);

[0040] The mass ratio of potassium sodium tartrate to CuSO4.5H2O is 1:(1.3-1.5);

[0041] The mass ratio of potassium sodium tartrate to EDTA-2Na is 1:(1-1.5);

[0042] The mass ratio of the potassium sodium tartrate to the volume of pure water is 1g:(25mL~30mL);

[0043] The mass ratio of the pure titanium powder in step 1 to the potassium sodium tartrate in step 4 is 1:(6-12). Other steps are the same as those in the first embodiment.

[0044] Specific embodiment 3: This embodiment differs from specific embodiment 1 in that the preparation method of the copper-plated carbon powder described in step 1 is as follows:

[0045] 1. Soak the carbon source in concentrated sulfuric acid, ultrasonically clean it for 10 to 15 minutes, then ultrasonically clean it in deionized water for another 10 to 15 minutes, and then filter and dry it in sequence at a drying temperature of 70°C for 30 minutes; the concentration of the concentrated sulfuric acid is 18.4 mol / L;

[0046] 2. Dissolve SnCl2 in deionized water, then add NaOH and dilute sulfuric acid solution in sequence, then add the dried product in step 1 and ultrasonically vibrate for 1 min to 3 min, and finally filter and dry in sequence;

[0047] The dilute sulfuric acid solution is 1 mol / L;

[0048] The mass ratio of SnCl2 to deionized water is (1g-5g):40mL;

[0049] The mass ratio of SnCl2 to NaOH is 1:(0.4-10);

[0050] The mass ratio of SnCl2 to the volume of the dilute sulfuric acid solution is 1g:(1mL~20mL);

[0051] The mass ratio of the carbon source described in step 1 to the SnCl2 described in step 2 is 1:(0.4-10);

[0052] 3. Mix the silver-based activator with purified water and stir, then add it to the dried product in step 2, mix it with ultrasound for 1 to 5 minutes, then filter and dry it in sequence at a drying temperature of 70°C for 30 minutes;

[0053] The silver-based activator is a silver ammonia solution with a concentration of 10g / L;

[0054] The mass ratio of the silver-based activator to pure water is 1:(1-5);

[0055] The volume ratio of the carbon source described in step 1 to the silver-based activator described in step 3 is 1g:(20mL-25mL);

[0056] 4. Add CuSO4.5H2O, potassium sodium tartrate and EDTA-2Na to pure water and mix and stir, then add NaOH to adjust the solution to a pH of 11.5-12.5, then place in a water bath at 70°C-75°C, add formaldehyde solution dropwise, and then add the dried product in step 3, heat in a water bath at 70°C-75°C for 5-6 minutes, until the solution changes from dark blue to white, and finally filter and dry in sequence to obtain copper-plated carbon powder, the thickness of the copper plating layer is 6μm-9μm;

[0057] The mass fraction of the formaldehyde solution is 37%;

[0058] The volume ratio of the formaldehyde solution to pure water is 1:(25-50);

[0059] The mass ratio of potassium sodium tartrate to CuSO4.5H2O is 1:(1.3-1.5);

[0060] The mass ratio of potassium sodium tartrate to EDTA-2Na is 1:(1-1.5);

[0061] The mass ratio of the potassium sodium tartrate to the volume of pure water is 1g:(25mL~30mL);

[0062] The mass ratio of the carbon source in step 1 to the potassium sodium tartrate in step 4 is 1:(6-12). Other steps are the same as those in the first embodiment.

[0063] Specific embodiment 4: This embodiment differs from specific embodiment 3 in that the carbon source in step 1 is carbon fiber powder and is 1000-mesh short-diameter carbon fiber. Other aspects are the same as specific embodiment 3.

[0064] Specific embodiment 5: This embodiment differs from specific embodiment 3 in that the carbon source in step 1 is 600-mesh diamond powder. Other aspects are the same as specific embodiment 3.

[0065] Specific embodiment 6: The difference between this embodiment and specific embodiment 3 is that the carbon source in step 1 is multi-walled carbon nanotubes with an outer diameter of 8nm to 15nm and a density of 0.08g / cm 3 The rest is the same as the third embodiment.

[0066] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that the carbon source in step 1 is amorphous carbon with a mesh size of 800. Other aspects are the same as specific embodiment 6.

[0067] Specific Embodiment 8: This embodiment differs from Specific Embodiment 1 in that the surface cleaning method for the base material silicon nitride ceramic in step 2 is as follows: the silicon nitride ceramic block is coarsely ground on a 400# diamond grinding wheel until the sample surface is flat. Then, a W3.5 diamond grinding paste is used to grind on a flat glass until there are no obvious wire cut marks on the silicon nitride to be welded. Then, a W1 grinding paste is used to grind until the silicon nitride ceramic surface is bright. Finally, ultrasonic cleaning is performed with anhydrous ethanol for 10 minutes and drying is performed for later use. Other aspects are the same as Specific Embodiment 1.

[0068] Specific embodiment 9: This embodiment differs from specific embodiment 1 in that the surface cleaning method for the base nickel-based alloy and MoCu alloy in step 2 is as follows: the base nickel-based alloy and MoCu alloy are treated with water sandpaper to remove the oxide layer and visible coarse scratches on the surface. The surfaces of the base nickel-based alloy and MoCu alloy are then polished with 600, 800, and 1000 grit metallographic sandpaper in sequence until no obvious scratches are left. Finally, the metal connection surface is polished with 0.5 μm diamond particles to make it bright. Other aspects are the same as specific embodiment 1.

[0069] Specific embodiment 10: This embodiment differs from specific embodiment 1 in that the adhesive in steps 3 and 4 is 502 glue. Other aspects are the same as specific embodiment 1.

[0070] The present invention is verified by the following test:

[0071] Experiment 1: This experiment is a method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal. The specific steps are as follows:

[0072] 1. Milling the copper-plated carbon powder and the copper-plated titanium powder in a planetary ball mill at a low speed of 100 r / min to obtain a uniformly mixed composite solder; the volume fraction of the copper-plated carbon powder in the composite solder powder is 20%;

[0073] The preparation method of the copper-plated titanium powder is as follows:

[0074] 1. Soak pure titanium powder in a mixture of acetone and anhydrous ethanol, ultrasonically clean for 10 minutes to remove grease on the powder surface, and then filter and dry in sequence at 70°C for 30 minutes; the mass proportion of acetone in the mixture of acetone and anhydrous ethanol is 50%; the particle size of the pure titanium powder is 2000 mesh;

[0075] 2. Dissolve SnCl2 in deionized water, then add NaOH and dilute sulfuric acid solution in sequence, then add the powder dried in step 1 and ultrasonically vibrate for 1 min to 3 min, and finally filter and dry in sequence;

[0076] The dilute sulfuric acid solution is 1 mol / L;

[0077] The mass ratio of SnCl2 to deionized water is 3g:40mL;

[0078] The mass ratio of SnCl2 to NaOH is 1:5;

[0079] The mass ratio of SnCl2 to the volume of dilute sulfuric acid solution is 1g:10mL;

[0080] The mass ratio of the pure titanium powder described in step 1 to the SnCl2 described in step 2 is 1:5;

[0081] 3. Mix the silver-based activator with purified water and stir, then add it to the dried product in step 2, mix it with ultrasound for 4 minutes, and then filter and dry it in sequence at a drying temperature of 70°C for 30 minutes;

[0082] The silver-based activator is a silver ammonia solution with a concentration of 10g / L;

[0083] The mass ratio of the silver-based activator to pure water is 1:3;

[0084] The volume ratio of the pure titanium powder described in step 1 to the silver-based activator described in step 3 is 1 g:25 mL;

[0085] 4. Add CuSO4.5H2O, potassium sodium tartrate and EDTA-2Na to pure water and mix and stir. Then add NaOH to adjust the solution to a pH of 12. Then place it in a 75°C water bath, add formaldehyde solution dropwise, and then add the dried product in step 3. Heat in a 75°C water bath for 6 minutes until the solution changes from dark blue to white. Finally, filter and dry in sequence to obtain copper-plated titanium powder. The thickness of the copper plating layer is 5 μm.

[0086] The mass fraction of the formaldehyde solution is 37%;

[0087] The volume ratio of the formaldehyde solution to pure water is 1:50;

[0088] The mass ratio of potassium sodium tartrate to CuSO4.5H2O is 1:1.3;

[0089] The mass ratio of potassium sodium tartrate to EDTA-2Na is 1:1.5;

[0090] The mass ratio of the potassium sodium tartrate to the volume of pure water is 1g:25mL;

[0091] The mass ratio of the pure titanium powder described in step 1 to the potassium sodium tartrate described in step 4 is 1:10.

[0092] The preparation method of the copper-plated carbon powder is as follows:

[0093] ①, soak the carbon source in concentrated sulfuric acid, ultrasonically clean it for 10 minutes, then ultrasonically clean it in deionized water for another 10 minutes, and then filter and dry it in sequence. The drying temperature is 70°C and the time is 30 minutes. The concentration of the concentrated sulfuric acid is 18.4 mol / L. The carbon source is carbon fiber powder and is a short-diameter carbon fiber of 1000 mesh.

[0094] ②, dissolve SnCl2 in deionized water, then add NaOH and dilute sulfuric acid solution in sequence, then add the dried product in step ① and ultrasonically shake for 1min to 3min, finally filter and dry in sequence;

[0095] The dilute sulfuric acid solution is 1 mol / L;

[0096] The mass ratio of SnCl2 to deionized water is 5g:40mL;

[0097] The mass ratio of SnCl2 to NaOH is 1:5;

[0098] The mass ratio of SnCl2 to the volume of dilute sulfuric acid solution is 1g:10mL;

[0099] The mass ratio of the carbon source described in step ① to the SnCl2 described in step ② is 1:5;

[0100] ③. Mix the silver-based activator and purified water, then add it to the dried product in step ②. Ultrasonic mix for 1 to 5 minutes, then filter and dry in sequence at 70°C for 30 minutes.

[0101] The silver-based activator is a silver ammonia solution with a concentration of 10g / L;

[0102] The mass ratio of the silver-based activator to pure water is 1:4;

[0103] The volume ratio of the carbon source described in step ① to the silver-based activator described in step ③ is 1 g:25 mL;

[0104] ④. Add CuSO4.5H2O, potassium sodium tartrate, and EDTA-2Na to pure water and mix and stir. Then, add NaOH to adjust the solution to a pH of 12. Then, place the solution in a 75°C water bath, add formaldehyde solution dropwise, and then add the dried product in step ③. Heat in a 75°C water bath for 6 minutes until the solution changes from dark blue to white. Finally, filter and dry in sequence to obtain copper-plated carbon powder. The thickness of the copper plating layer is 9 μm.

[0105] The mass fraction of the formaldehyde solution is 37%;

[0106] The volume ratio of the formaldehyde solution to pure water is 1:30;

[0107] The mass ratio of potassium sodium tartrate to CuSO4.5H2O is 1:1.5;

[0108] The mass ratio of potassium sodium tartrate to EDTA-2Na is 1:1.5;

[0109] The mass ratio of the potassium sodium tartrate to the volume of pure water is 1g:30mL;

[0110] The mass ratio of the carbon source described in step ① to the potassium sodium tartrate described in step ④ is 1:10;

[0111] 2. Clean the surface of the base material nickel-based alloy GH4169, MoCu30 alloy and base material silicon nitride ceramic;

[0112] The surface cleaning method of the base material silicon nitride ceramic is as follows: the silicon nitride ceramic block is coarsely ground on a 400# diamond grinding wheel until the sample surface is flat, and then it is ground on a flat glass with W3.5 diamond grinding paste until there are no obvious wire cutting marks on the silicon nitride welding surface, and then it is ground with W1 grinding paste until the silicon nitride ceramic surface is bright, and finally it is ultrasonically cleaned with anhydrous ethanol for 10 minutes and dried for use;

[0113] The method for cleaning the surfaces of the base nickel-based alloy and the MoCu30 alloy is as follows: the oxide layer and coarse scratches visible to the naked eye are treated on the surfaces of the base nickel-based alloy and the MoCu30 alloy with water sandpaper, and then the surfaces of the base nickel-based alloy and the MoCu30 alloy are polished with 600, 800, and 1000 grit metallographic sandpaper in sequence until no obvious scratches are left, and finally polished with diamond particles with a particle size of 0.5 μm to make the metal connection surface bright;

[0114] 3. Use a tablet press to press the composite solder prepared in step 1 and the MoCu30 alloy cleaned in step 2 into tablets, then place a MoCu30 alloy sheet between the two composite solder sheets to form a sandwich structure, and apply 502 glue between the layers to obtain the intermediate layer solder;

[0115] Fourth, an intermediate layer of brazing filler metal and a cleaned base material of silicon nitride ceramic are sequentially placed on the cleaned base material of nickel-based alloy, and 502 glue is applied between the intermediate layer of brazing filler metal and the two base materials to obtain a workpiece to be welded;

[0116] 5. Place the workpiece to be welded assembled in step 4 into a vacuum heating furnace. First, heat it from room temperature to 300℃ at a rate of 10℃ / min and keep it warm for 30min to ensure that the 502 glue is completely volatilized. Then, heat it from 300℃ to 1020℃ at a rate of 10℃ / min and keep it warm for 10min. Finally, cool it down to 300℃ at a rate of 5℃ / min and then cool it to room temperature with the furnace to complete the brazing of ceramic and metal. The entire process of step 5 is carried out under vacuum. The vacuum degree in the high temperature zone (above 750℃) should be ensured to be 1×10 -2 After the connection is completed, there is no obvious microcrack in the silicon nitride ceramic / GH4169 alloy joint, the room temperature shear strength of the joint is 117 MPa, and the high temperature shear strength of the joint tested at 800°C is 72 MPa.

[0117] Figure 1 This is the assembly diagram of the workpiece to be welded in step 4 of experiment 1, where 1 is Si3N4 ceramic, 2 is composite brazing filler metal, 3 is MoCu30 alloy, and 4 is nickel-based high-temperature alloy GH4169.

[0118] Experiment 2: This experiment differed from Experiment 1 in that the volume fraction of copper-plated carbon powder in the composite solder powder in Step 1 was 8%, the carbon source was amorphous carbon of 800 mesh, and in Step 5, the temperature was increased from 300°C to 1040°C at a rate of 10°C / min and held for 5 minutes. All other conditions were the same as Experiment 1. After the joint was completed, the silicon nitride ceramic / GH4169 alloy joint showed no visible microcracks. The room temperature shear strength of the joint was 69 MPa, and the high-temperature shear strength tested at 800°C was 34 MPa.

[0119] Experiment 3: This experiment differed from Experiment 1 in that the volume fraction of copper-plated carbon powder in the composite solder powder in Step 1 was 10%, and the carbon source was 600-mesh diamond micropowder. In Step 5, the temperature was increased from 300°C to 1060°C at a rate of 10°C / min and held for 5 minutes. All other conditions were the same as Experiment 1. After the joint was completed, the silicon nitride ceramic / GH4169 alloy joint showed no visible microcracks, and the room-temperature shear strength of the joint was 74 MPa.

[0120] Experiment 4: This experiment differs from Experiment 1 in that the volume fraction of copper-plated carbon powder in the composite solder powder described in Step 1 is 12%, and the carbon source is multi-walled carbon nanotubes with an outer diameter of 8nm to 15nm and a density of 0.08g / cm 3 In step 5, the temperature was raised from 300°C to 1000°C at a rate of 10°C / min and held for 20 minutes. All other conditions were the same as in experiment 1. After the connection was completed, the silicon nitride ceramic / GH4169 alloy joint showed no visible microcracks, and the room temperature shear strength of the joint was 65 MPa.

[0121] Figure 2 This is the SEM image of the copper-plated carbon powder described in step 1 of experiment 2. Figure 3This is the XRD pattern of the copper-plated carbon powder described in step 1 of experiment 2. The XRD results show that no impurities were introduced during the copper plating process on the surface of the amorphous carbon powder. The SEM image shows that the copper plating layer relatively evenly wraps the amorphous carbon powder, and the chemical copper plating effect is good.

[0122] Figure 4 This is the XRD spectrum of the copper-plated carbon powder described in step 1 of experiment 3. The XRD results show that no impurities were introduced during the copper plating process on the surface of the diamond micropowder, and the coating was relatively thick, and the original parent material was not detected.

[0123] Figure 5 Table 1 shows the SEM photos of the silicon nitride ceramic / GH4169 alloy joint structure obtained in Experiment 1. Figure 5 The corresponding EDS results, combined with the SEM images, reveal a well-bonded joint with a thin interfacial reaction layer of approximately 1.6 μm, specifically consisting of a TiN+Ti5Si3 layer. Low-expansion carbon fibers are evenly distributed within the weld, with the TiC bonding the fibers to the weld. The weld also contains a copper-based solid solution and a small amount of dispersed Cu-Ti intermetallic compounds. The network-like distribution of the copper-based solid solution can alleviate residual stresses through plastic deformation.

[0124] Table 1

[0125]

[0126] Figure 6 Table 2 is the SEM photo of the silicon nitride ceramic / GH4169 alloy joint structure obtained in Experiment 2. Figure 6 The corresponding EDS results show that the joint structure is similar to that of the carbon fiber used in Experiment 1. The results show that the joint is well bonded, and the amorphous carbon adsorbs the active element Ti to react and form the TiC phase. However, due to the decrease in volume fraction, the ceramic interface reaction layer thickens, the amorphous carbon content in the weld is low, the weld thermal expansion coefficient is still large, and the connection strength is greatly reduced.

[0127] Table 2

[0128]

Claims

1. A method for connecting silicon nitride / nickel-based high-temperature alloys using chemically modified composite brazing filler metals, characterized in that The method of joining silicon nitride / nickel-based high-temperature alloys using chemically modified composite brazing filler metals is carried out in the following steps:

1. Milling copper-plated carbon powder and copper-plated titanium powder at a low speed in a planetary ball mill to obtain a uniformly mixed composite solder; the volume fraction of the copper-plated carbon powder in the composite solder is 5% to 25%; 2. Clean the surface of the base material nickel-based alloy, MoCu alloy and base material silicon nitride ceramic; 3. Using a tablet press, the composite solder prepared in step 1 and the cleaned MoCu alloy in step 2 are respectively tableted, and then a MoCu alloy sheet is placed between the two composite solder sheets to form a sandwich structure, and a binder is applied between the layers to obtain an intermediate layer solder; Fourth, an intermediate layer of brazing filler metal and a cleaned base material of silicon nitride ceramic are sequentially placed on the cleaned base material of nickel-based alloy, and an adhesive is applied between the intermediate layer of brazing filler metal and the two base materials to obtain a workpiece to be welded; 5. Place the workpiece to be welded assembled in step 4 into a vacuum heating furnace, heat it from room temperature to 300℃~310℃ and keep it warm for 30min~35min to ensure that the adhesive is completely volatilized; then heat it from 300℃~310℃ to 1000℃~1060℃ and keep it warm for 5min~20min; finally, slowly cool it to 300℃~310℃, and then cool it to room temperature with the furnace to complete the brazing of ceramic and metal; the entire process of step 5 is carried out under vacuum.

2. The method for connecting silicon nitride / nickel-based high-temperature alloys using chemically modified composite brazing filler metal according to claim 1, characterized in that The preparation method of the copper-plated titanium powder described in step 1 is as follows:

1. Soak pure titanium powder in a mixture of acetone and anhydrous ethanol, ultrasonically clean for 10 to 15 minutes to remove grease on the powder surface, and then filter and dry the powder in sequence at 70°C for 30 minutes; the weight proportion of acetone in the mixture of acetone and anhydrous ethanol is 50%; the particle size of the pure titanium powder is 2000 mesh; 2. Dissolve SnCl2 in deionized water, then add NaOH and dilute sulfuric acid solution in sequence, then add the powder dried in step 1 and ultrasonically shake for 1 min to 3 min, and finally filter and dry in sequence; The dilute sulfuric acid solution is 1 mol / L; The mass ratio of SnCl2 to deionized water is (1g~5g):40mL; The mass ratio of SnCl2 to NaOH is 1:(0.4~10); The volume ratio of the SnCl2 mass to the dilute sulfuric acid solution is 1g:(1mL~20mL); The mass ratio of the pure titanium powder described in step 1 to the SnCl2 described in step 2 is 1:(0.4~10); 3. Mix the silver-based activator with purified water and stir, then add it to the dried product in step 2, mix it with ultrasound for 1 min to 5 min, then filter and dry it in sequence at a drying temperature of 70°C for 30 min; The silver-based activator is a silver ammonia solution with a concentration of 10g / L; The mass ratio of the silver-based activator to pure water is 1:(1-5); The volume ratio of the pure titanium powder described in step 1 to the silver-based activator described in step 3 is 1g:(20mL~25mL); 4. Add CuSO4.5H2O, potassium sodium tartrate and EDTA-2Na to pure water and mix and stir, then add NaOH to adjust the solution to a pH of 11.5-12.5, then place in a water bath at 70°C-75°C, add formaldehyde solution dropwise, and then add the dried product in step 3, heat in a water bath at 70°C-75°C for 5-6 minutes, until the solution changes from dark blue to white, and finally filter and dry in sequence to obtain copper-plated titanium powder, the thickness of the copper plating layer being 1 μm-5 μm; The mass fraction of the formaldehyde solution is 37%; The volume ratio of the formaldehyde solution to pure water is 1:(25-50); The mass ratio of potassium sodium tartrate to CuSO4.5H2O is 1:(1.3-1.5); The mass ratio of potassium sodium tartrate to EDTA-2Na is 1:(1-1.5); The mass ratio of the potassium sodium tartrate to the volume of pure water is 1g:(25mL~30mL); The mass ratio of the pure titanium powder described in step 1 to the potassium sodium tartrate described in step 4 is 1:(6~12).

3. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 1, wherein The preparation method of the copper-plated carbon powder described in step 1 is as follows:

1. Soak the carbon source in concentrated sulfuric acid, ultrasonically clean it for 10 to 15 minutes, then ultrasonically clean it in deionized water for another 10 to 15 minutes, and then filter and dry it in sequence at a drying temperature of 70°C for 30 minutes; the concentration of the concentrated sulfuric acid is 18.4 mol / L; 2. Dissolve SnCl2 in deionized water, then add NaOH and dilute sulfuric acid solution in sequence, then add the dried product in step 1 and ultrasonically vibrate for 1 min to 3 min, and finally filter and dry in sequence; The dilute sulfuric acid solution is 1 mol / L; The mass ratio of SnCl2 to deionized water is (1g~5g):40mL; The mass ratio of SnCl2 to NaOH is 1:(0.4~10); The volume ratio of the SnCl2 mass to the dilute sulfuric acid solution is 1g:(1mL~20mL); The mass ratio of the carbon source described in step 1 to the SnCl2 described in step 2 is 1:(0.4~10); 3. Mix the silver-based activator with purified water and stir, then add it to the dried product in step 2, mix it with ultrasound for 1 min to 5 min, then filter and dry it in sequence at a drying temperature of 70°C for 30 min; The silver-based activator is a silver ammonia solution with a concentration of 10g / L; The mass ratio of the silver-based activator to pure water is 1:(1-5); The volume ratio of the carbon source described in step 1 to the silver-based activator described in step 3 is 1g:(20mL~25mL); 4. Add CuSO4.5H2O, potassium sodium tartrate and EDTA-2Na to pure water and mix and stir, then add NaOH to adjust the solution to a pH of 11.5-12.5, then place in a water bath at 70°C-75°C, add formaldehyde solution dropwise, and then add the dried product in step 3, heat in a water bath at 70°C-75°C for 5-6 minutes, until the solution changes from dark blue to white, and finally filter and dry in sequence to obtain copper-plated carbon powder, with a copper coating thickness of 6μm-9μm; The mass fraction of the formaldehyde solution is 37%; The volume ratio of the formaldehyde solution to pure water is 1:(25-50); The mass ratio of potassium sodium tartrate to CuSO4.5H2O is 1:(1.3-1.5); The mass ratio of potassium sodium tartrate to EDTA-2Na is 1:(1-1.5); The mass ratio of the potassium sodium tartrate to the volume of pure water is 1g:(25mL~30mL); The mass ratio of the carbon source described in step 1 to the potassium sodium tartrate described in step 4 is 1:(6~12).

4. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 3, wherein The carbon source described in step 1 is carbon fiber powder and is 1000 mesh short diameter carbon fiber.

5. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 3, wherein The carbon source described in step 1 is diamond powder and has a mesh size of 600.

6. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 3, wherein The carbon source described in step 1 is multi-walled carbon nanotubes with an outer diameter of 8nm~15nm and a density of 0.08g / cm 3 .

7. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 3, wherein The carbon source described in step 1 is amorphous carbon and has a mesh size of 800.

8. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 1, wherein The method for surface cleaning of the base material silicon nitride ceramic in step 2 is as follows: coarsely grind the silicon nitride ceramic block on a 400# diamond grinding wheel until the sample surface is flat, then use W3.5 diamond grinding paste to grind on a flat glass until there are no obvious wire cutting marks on the silicon nitride welding surface, then use W1 grinding paste to grind until the surface of the silicon nitride ceramic is bright, and finally use anhydrous ethanol ultrasonic cleaning for 10 minutes and dry for later use.

9. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 1, wherein The method for surface cleaning of the base material nickel-based alloy and MoCu alloy in step 2 is as follows: the base material nickel-based alloy and MoCu alloy are treated with water sandpaper to remove the oxide layer and coarse scratches visible to the naked eye on the surface, and then the surface of the base material nickel-based alloy and MoCu alloy is polished with 600, 800, and 1000 metallographic sandpaper in sequence until there are no obvious scratches, and finally polished with diamond particles with a particle size of 0.5 μm to make the metal connection surface bright.

10. The method for joining silicon nitride / nickel-based high-temperature alloys using a chemically modified composite brazing filler metal according to claim 1, wherein The adhesive described in step 3 and step 4 is 502 glue.

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