A method for local current heating diffusion bonding of large-size high-temperature alloys with foil-powder intermediate layers

Abstract

A method for local current heating diffusion connection of large-sized high-temperature alloys with a foil-powder intermediate layer is disclosed, and the method is designed in the technical field of diffusion connection of large-sized high-temperature alloy materials. The purpose of the present invention is to solve the problems of large power loss, low energy utilization rate, and reduction of comprehensive mechanical properties of the original material after a certain period of heating in the existing large-sized high-temperature alloy current heating diffusion connection process. Method: 1. Grinding; 2. Preparing two high-temperature alloy parts to be diffusion-connected coated with nickel powder; 3. Sandwiching nickel foil between the two parts to be diffusion-connected; 4. Sealing and welding the two parts to be diffusion-connected, and evacuating; 5. Assembling and connecting; 6. Applying pressure; 7. Controlling the operation of the circulating water system; 8. Evacuating; 9. Controlling the start of the DC power supply to perform local current heating diffusion connection; 10. Cooling. The present invention avoids the problem of reduced comprehensive mechanical properties of the original material after a certain period of heating.

Description

Technical Field

[0001] The present invention relates to the technical field of diffusion bonding of large-size high-temperature alloy materials. Background Art

[0002] With the continuous development of cutting-edge industries such as aerospace in my country, the demand for high-temperature structural materials is also gradually increasing. According to surveys, the use of high-temperature alloys in aircraft engines and rocket engines exceeds 50%. However, due to the complex alloy system of high-temperature alloys, in addition to the matrix elements Fe, Co, and Ni, they also contain a large number of strengthening elements, which makes joining high-temperature alloys extremely difficult. Problems such as cracking and strength loss are very likely to occur during fusion welding. Even using high-energy density fusion welding methods such as lasers or electron beams, it is difficult to avoid defects such as cracks. Therefore, it is generally believed that non-melting methods are the best way to join high-temperature alloys, which can fundamentally solve the problems caused by fusion welding. Diffusion bonding is a relatively effective and promising process for non-melting joining of high-temperature alloys.

[0003] Traditional diffusion bonding processes require materials to be heated at high temperatures for extended periods, significantly wasting energy and increasing the manufacturing requirements and cost of heating equipment. Furthermore, prolonged heat exposure can lead to significant grain growth and surface oxidation, making diffusion bonding difficult and significantly reducing the overall mechanical properties of the original material.

[0004] In recent years, welding processes using electric current heating have emerged. By leveraging the Joule heating effect of electric current to reach a high temperature in a very short time, they can effectively address the poor welding performance of some difficult-to-weld materials. For example, the invention patent "A Current-Heated Diffusion Bonding Apparatus and Method," published in 2020, utilizes electric current heating to diffusion bond plates. However, high-temperature alloys are difficult to deform, resulting in poor physical contact during diffusion bonding. The pressure required to achieve close contact increases, the time required is long, and the diffusion bonding process requires high temperatures. The addition of an intermediate layer can effectively improve surface contact, reduce pressure during diffusion bonding, and lower the bonding temperature and time. For example, the invention patent "A SPS Diffusion Bonding Method for DD98 Nickel-Based Single Crystal Superalloy," published in 2022, uses a Ni-Cr-WB-Si-Fe powder brazing filler metal as an intermediate layer. Spark plasma sintering technology achieves effective bonding of DD98 nickel-based single crystal superalloys at a relatively low temperature and in a relatively short time. However, this method still involves heating the entire material, which not only takes a long time and has low energy efficiency, but also degrades the overall material performance. Localized current heating can effectively improve this situation. For example, the utility model patent "A Pulse Current Assisted Local High-Temperature Diffusion Bonding Device for Titanium Alloys" published in 2014 uses localized current diffusion bonding to bond titanium alloys.

[0005] However, the current localized current heating diffusion bonding process still applies current directly to the materials to be bonded, gradually transferring the Joule heat generated by the current to the bonding surface. Compared to overall heating, the current loading method remains unchanged. This leads to significant energy loss and low energy efficiency in current heating diffusion bonding of large-scale high-temperature alloys. Furthermore, heat is still transferred from the original material to the bonding surface, and the overall mechanical properties of the material degrade after a certain period of heating. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of large power loss, low energy utilization rate and degradation of the comprehensive mechanical properties of the original material after a certain period of heating in the existing large-scale high-temperature alloy current heating diffusion bonding process, and to provide a method for local current heating diffusion bonding of large-scale high-temperature alloys with a foil-powder intermediate layer.

[0007] A method for locally heating and diffusing a large-scale high-temperature alloy with a foil-powder intermediate layer by local current heating is specifically accomplished by the following steps:

[0008] 1. The surfaces of the high-temperature alloy to be diffusion-bonded are polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy parts to be diffusion-bonded;

[0009] 2. Cutting the nickel foil into a rectangle having the same width as the high-temperature alloy to be diffusion-bonded and a length slightly longer than the high-temperature alloy to be diffusion-bonded to obtain the cut nickel foil; adding nickel powder to ethylene glycol and mixing them evenly to obtain a paste coating; applying the paste coating to the surfaces to be diffusion-bonded of the two high-temperature alloy to be diffusion-bonded, respectively; and then placing the two high-temperature alloy to be diffusion-bonded in a vacuum drying oven until completely dried, to obtain two high-temperature alloy to be diffusion-bonded coated with nickel powder;

[0010] 3. Align the surfaces of two high-temperature alloy pieces coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces, ensuring that the upper and lower surfaces of the nickel foil are flush with the surfaces and that the left and right ends extend the same length beyond the surfaces.

[0011] Fourth, perform edge sealing welding on the two parts to be diffusion connected, and leave an exhaust hole; weld the exhaust pipe to the exhaust hole, and install a vacuum gauge and a valve on the exhaust pipe; perform air tightness test on the parts to be diffusion connected after edge sealing welding, and vacuumize the parts to be diffusion connected with good air tightness, close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the parts to be diffusion connected after vacuuming;

[0012] The position of the exhaust hole described in step 4 is left above or below the diffusion connection surface;

[0013] 5. First, place the pad, the pressure-resistant insulating block, the part to be diffused and connected after vacuuming, the pressure-resistant insulating block, and the pad from bottom to top on the platform inside the hydraulic press. Then, clamp the two copper electrodes on the two electrode clamps respectively. Then, connect the two copper electrodes to the positive and negative poles of the DC power supply respectively. Finally, connect the two electrode clamps to the nickel foil exposed on the left and right sides of the part to be diffused and connected respectively.

[0014] 6. Turn on the hydraulic press and apply pressure to the diffusion connection piece after vacuuming until the pressure reaches the predetermined pressure value and keep the pressure constant;

[0015] 7. Control the operation of the circulating water system to keep the water temperature outside the water-cooling wire at threshold A;

[0016] 8. Connect the exhaust pipe of the diffusion joint to the vacuum pump, open the valve, and continue to vacuum;

[0017] 9. After the vacuum degree reaches a certain value, control the DC power supply to start, so that the temperature of the surface to be diffused and connected rises steadily at a certain rate until the temperature of the surface to be diffused and connected meets the temperature required for diffusion bonding. -2 Perform local current heating diffusion bonding of high temperature alloy parts to be diffusion bonded under Pa;

[0018] 10. After the diffusion bonding is completed, turn off the DC power supply, then raise the hydraulic press to stop maintaining pressure, stop vacuuming after cooling to a certain temperature, close the valve and take out the final high-temperature alloy diffusion bonded parts.

[0019] Principles and advantages of the present invention:

[0020] Based on the existing current-heated diffusion bonding process, the present invention changes the existing current loading method, directly clamping the electrodes in the middle layer (nickel foil). Utilizing the Joule heating effect of current, the resistance of the diffusion bonding surface of the diffusion bonding member is much greater than that of other areas, thereby concentrating most of the heat on the diffusion bonding surface, greatly improving energy utilization while avoiding the problem of reduced comprehensive mechanical properties of the original material after a certain period of heating. In addition, the present invention uses foil-powder as the middle layer. The powder is instantly heated to a high temperature under the action of pulsed current, and plasma is generated. This plasma is rapidly transferred between the powder particles, uniformly heating the entire diffusion bonding surface. Due to the rapid heating of the powder particles and the presence of plasma, the diffusion bonding process of the material can be completed quickly, while reducing the temperature requirement and avoiding excessive grain growth. Moreover, the overall process device is simple, which can achieve process automation and scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is a front view of the apparatus required for a method of localized current heating diffusion bonding of a foil-powder intermediate layer of a high-temperature alloy in Example 1. In the figure, 1 is a hydraulic press, 2 is the part to be diffusion bonded, 3 is an electrode clamp, 4 is a copper electrode, 5 is a DC power supply, 6 is a circulating water system, 7 is a spacer, 8 is nickel foil, and 9 is a pressure-resistant insulating block.

[0022] Figure 2 This is a side view of the apparatus required for a method of localized current heating diffusion bonding of a high-temperature alloy foil-powder intermediate layer in Example 1. In the figure, 10 is a vacuum gauge, 11 is a valve, 12 is an exhaust pipe, and 13 is a vacuum pump.

[0023] Figure 3 This is the interface microstructure of the GH4169 high-temperature alloy in Example 1 after local current heating and diffusion bonding between the nickel powder and nickel foil intermediate layer;

[0024] Figure 4 3. The figures are comparison diagrams before and after shear test of shear specimens obtained after diffusion bonding of GH4169 high-temperature alloy under different conditions. In the figure, (a) is GH4169 high-temperature alloy without an intermediate layer and diffusion-bonded using the existing overall current heating, (b) is GH4169 high-temperature alloy with a nickel foil intermediate layer added and diffusion-bonded using the existing overall current heating, (c) is GH4169 high-temperature alloy in Example 1 with a nickel foil-nickel powder intermediate layer added and diffusion-bonded using local current heating, (d) is GH4169 high-temperature alloy in Control Example 1 with a nickel foil added and diffusion-bonded using local current heating, and (e) is GH4169 high-temperature alloy in Control Example 2 with a nickel powder intermediate layer added and diffusion-bonded using the existing overall current heating. DETAILED DESCRIPTION

[0025] Specific embodiment 1: This embodiment provides a method for locally heating and diffusion-bonding a large-sized high-temperature alloy foil-powder intermediate layer by local current, which is specifically completed in the following steps:

[0026] 1. The surfaces of the high-temperature alloy to be diffusion-bonded are polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy parts to be diffusion-bonded;

[0027] 2. Cutting the nickel foil into a rectangle having the same width as the high-temperature alloy to be diffusion-bonded and a length slightly longer than the high-temperature alloy to be diffusion-bonded to obtain the cut nickel foil; adding nickel powder to ethylene glycol and mixing them evenly to obtain a paste coating; applying the paste coating to the surfaces to be diffusion-bonded of the two high-temperature alloy to be diffusion-bonded, respectively; and then placing the two high-temperature alloy to be diffusion-bonded in a vacuum drying oven until completely dried, to obtain two high-temperature alloy to be diffusion-bonded coated with nickel powder;

[0028] 3. Align the surfaces of two high-temperature alloy pieces coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces, ensuring that the upper and lower surfaces of the nickel foil are flush with the surfaces and that the left and right ends extend the same length beyond the surfaces.

[0029] Fourth, perform edge sealing welding on the two parts to be diffusion connected, and leave an exhaust hole; weld the exhaust pipe to the exhaust hole, and install a vacuum gauge and a valve on the exhaust pipe; perform air tightness test on the parts to be diffusion connected after edge sealing welding, and vacuumize the parts to be diffusion connected with good air tightness, close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the parts to be diffusion connected after vacuuming;

[0030] The position of the exhaust hole described in step 4 is left above or below the diffusion connection surface;

[0031] 5. First, place the pad, the pressure-resistant insulating block, the part to be diffused and connected after vacuuming, the pressure-resistant insulating block, and the pad from bottom to top on the platform inside the hydraulic press. Then, clamp the two copper electrodes on the two electrode clamps respectively. Then, connect the two copper electrodes to the positive and negative poles of the DC power supply respectively. Finally, connect the two electrode clamps to the nickel foil exposed on the left and right sides of the part to be diffused and connected respectively.

[0032] 6. Turn on the hydraulic press and apply pressure to the diffusion connection piece after vacuuming until the pressure reaches the predetermined pressure value and keep the pressure constant;

[0033] 7. Control the operation of the circulating water system to keep the water temperature outside the water-cooling wire at threshold A;

[0034] 8. Connect the exhaust pipe of the diffusion joint to the vacuum pump, open the valve, and continue to vacuum;

[0035] 9. After the vacuum degree reaches a certain value, control the DC power supply to start, so that the temperature of the surface to be diffused and connected rises steadily at a certain rate until the temperature of the surface to be diffused and connected meets the temperature required for diffusion bonding. -2 Perform local current heating diffusion bonding of high temperature alloy parts to be diffusion bonded under Pa;

[0036] 10. After the diffusion bonding is completed, turn off the DC power supply, then raise the hydraulic press to stop maintaining pressure, stop vacuuming after cooling to a certain temperature, close the valve and take out the final high-temperature alloy diffusion bonded parts.

[0037] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the high-temperature alloy described in step 1 is a nickel-based high-temperature alloy or a nickel-aluminum alloy; and the polishing described in step 1 is performed using 180-grit, 400-grit, and 800-grit sandpaper in sequence. The other steps are the same as those in specific embodiment 1.

[0038] Specific embodiment 3: This embodiment differs from specific embodiments 1 or 2 in that the particle size of the nickel powder in step 2 is 5 μm to 15 μm and the thickness of the nickel foil in step 2 is 30 μm to 50 μm. The other steps are the same as those in specific embodiments 1 or 2.

[0039] Specific Embodiment 4: This embodiment differs from Specific Embodiments 1 to 3 in that the length of the cut nickel foil in Step 2 is 5 cm to 8 cm longer than the length of the high-temperature alloy to be diffusion-bonded; and the volume ratio of nickel powder to ethylene glycol in the paste coating in Step 2 is (30 g to 50 g): (20 mL to 25 mL). Other steps are the same as Specific Embodiments 1 to 3.

[0040] Specific embodiment 5: The difference between this embodiment and specific embodiments 1 to 4 is that the mass ratio of the paste coating in step 2 to the surface area of ​​the high-temperature alloy to be diffusely connected is (5g~10g): (10cm 2 ~15cm 2 ); the temperature of the vacuum drying oven in step 2 is 50° C. to 70° C. The other steps are the same as those in specific embodiments 1 to 4.

[0041] Specific embodiment 6: The difference between this embodiment and specific embodiments 1 to 5 is that: in step 4, when the vacuum degree is 1×10 -1 When the pressure reaches 0.0543 MPa, the valve is closed and the vacuum pumping is stopped. The other steps are the same as those in the first to fifth embodiments.

[0042] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the electrode clamp in step 5 is made of copper and the pressure-resistant insulating block in step 5 is made of phenolic resin. The other steps are the same as specific embodiments 1 to 6.

[0043] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the predetermined pressure value in step 6 is 30 MPa to 50 MPa, and the temperature of threshold A in step 7 is 22° C. to 25° C. The other steps are the same as specific embodiments 1 to 7.

[0044] Specific embodiment 9: The difference between this embodiment and specific embodiments 1 to 8 is that in step 9, when the vacuum degree reaches 1×10 -2 Pa, the DC power supply is turned on; the output current of the DC power supply in step 9 is 0 to 10,000 A, the output voltage is 0 to 8 V, and the output frequency is 0 to 40 kHz; the temperature rise rate at the surface to be diffused and bonded in step 9 is 200°C / min to 300°C / min. The other steps are the same as those in specific embodiments 1 to 8.

[0045] Specific Embodiment 10: This embodiment differs from Specific Embodiments 1 to 9 in that the diffusion bonding described in step 9 requires a temperature of 900°C to 1200°C; the local current heating diffusion bonding described in step 9 lasts for 15 to 60 minutes; and vacuuming is stopped after the temperature is lowered to 200°C to 300°C in step 10. The remaining steps are the same as Specific Embodiments 1 to 9.

[0046] The following examples are used to verify the beneficial effects of the present invention:

[0047] Example 1: A method for locally heating and diffusing a large-scale high-temperature alloy to connect a foil-powder intermediate layer by local current is specifically accomplished by the following steps:

[0048] 1. The surfaces of the high-temperature alloy to be diffusion-bonded are polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy parts to be diffusion-bonded;

[0049] The high temperature alloy described in step 1 is GH4169 high temperature alloy;

[0050] The polishing described in step 1 is performed using 180-grit, 400-grit, and 800-grit sandpaper in sequence;

[0051] 2. Cutting the nickel foil into a rectangle having the same width as the high-temperature alloy to be diffusion-bonded and a length slightly longer than the high-temperature alloy to be diffusion-bonded to obtain the cut nickel foil; adding nickel powder to ethylene glycol and mixing them evenly to obtain a paste coating; applying the paste coating to the surfaces to be diffusion-bonded of the two high-temperature alloy to be diffusion-bonded, respectively; and then placing the two high-temperature alloy to be diffusion-bonded in a vacuum drying oven until completely dried, to obtain two high-temperature alloy to be diffusion-bonded coated with nickel powder;

[0052] The particle size of the nickel powder described in step 2 is 5 μm;

[0053] The thickness of the nickel foil described in step 2 is 30 μm;

[0054] The length of the nickel foil cut in step 2 is 6 cm longer than the length of the high-temperature alloy to be diffusion-bonded;

[0055] The volume ratio of nickel powder to ethylene glycol in the paste coating described in step 2 is 40g:25mL;

[0056] The ratio of the mass of the paste coating in step 2 to the surface area of ​​the high-temperature alloy to be diffusion-bonded is 10g:15cm 2 ;

[0057] The temperature of the vacuum drying oven described in step 2 is 70°C;

[0058] 3. Align the surfaces of two high-temperature alloy pieces coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces, ensuring that the upper and lower surfaces of the nickel foil are flush with the surfaces and that the left and right ends extend the same length beyond the surfaces.

[0059] Fourth, perform edge sealing welding on the two parts to be diffusion connected, and leave an exhaust hole; weld the exhaust pipe to the exhaust hole, and install a vacuum gauge and a valve on the exhaust pipe; perform air tightness test on the parts to be diffusion connected after edge sealing welding, and vacuumize the parts to be diffusion connected with good air tightness, close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the parts to be diffusion connected after vacuuming;

[0060] The position of the exhaust hole described in step 4 is left above or below the diffusion connection surface;

[0061] Step 4: When the vacuum degree is 1×10 -1 When Pa, close the valve and stop vacuuming;

[0062] 5. First, place the pad, the pressure-resistant insulating block, the part to be diffused and connected after vacuuming, the pressure-resistant insulating block, and the pad from bottom to top on the platform inside the hydraulic press. Then, clamp the two copper electrodes on the two electrode clamps respectively. Then, connect the two copper electrodes to the positive and negative poles of the DC power supply respectively. Finally, connect the two electrode clamps to the nickel foil exposed on the left and right sides of the part to be diffused and connected respectively.

[0063] The electrode splint described in step 5 is made of copper;

[0064] The material of the voltage-resistant insulating block described in step 5 is phenolic resin;

[0065] 6. Turn on the hydraulic press and apply pressure to the diffusion connection piece after vacuuming until the pressure reaches the predetermined pressure value and keep the pressure constant;

[0066] The predetermined pressure value described in step 6 is 50 MPa;

[0067] 7. Control the operation of the circulating water system to keep the water temperature outside the water-cooling wire at threshold A;

[0068] The temperature of the threshold A described in step 7 is 24°C;

[0069] 8. Connect the exhaust pipe of the diffusion joint to the vacuum pump, open the valve, and continue to vacuum;

[0070] 9. After the vacuum degree reaches a certain value, control the DC power supply to start, so that the temperature of the surface to be diffused and connected rises steadily at a certain rate until the temperature of the surface to be diffused and connected meets the temperature required for diffusion bonding. -2Perform local current heating diffusion bonding of high temperature alloy parts to be diffusion bonded under Pa;

[0071] In step nine, wait until the vacuum degree reaches 1×10 -2 Control the start of DC power supply at Pa;

[0072] The output current of the DC power supply described in step nine is 0 to 10000A, the output voltage is 0 to 8V, and the output frequency is 0 to 40kHz;

[0073] The temperature rise rate at the surface to be diffused and connected in step nine is 200°C / min;

[0074] The diffusion bonding described in step nine requires a temperature of 1000°C;

[0075] The time for the local current heating diffusion connection described in step nine is 20 minutes;

[0076] 10. After the diffusion bonding is completed, turn off the DC power supply, then raise the hydraulic press to stop maintaining pressure, cool down to a certain temperature, stop vacuuming, close the valve and take out the final high-temperature alloy diffusion bonded parts;

[0077] In step 10, the vacuuming is stopped after the temperature drops to 300°C.

[0078] Comparative Example 1: This example differs from Example 1 in that nickel powder is omitted. Specifically, in step 2, the nickel foil is cut into a rectangular shape with a width equal to that of the high-temperature alloy to be diffusion-bonded and a length slightly longer than the high-temperature alloy to be diffusion-bonded, thereby obtaining the trimmed nickel foil. In step 3, the surfaces to be diffusion-bonded of the two high-temperature alloy to be diffusion-bonded are aligned, and the trimmed nickel foil is sandwiched between the two components, ensuring that the upper and lower surfaces of the nickel foil are flush with the surfaces to be diffusion-bonded, and that the left and right ends extend the same length beyond the surfaces to be diffusion-bonded. All other steps and parameters are the same as in Example 1.

[0079] Comparative Example 2: This comparative example adds a nickel powder intermediate layer and adopts the existing overall current heating diffusion connection.

[0080] Figure 3 This is the interface microstructure of the GH4169 high-temperature alloy in Example 1 after local current heating and diffusion bonding between the nickel powder and nickel foil intermediate layer;

[0081] Depend on Figure 3 It can be seen that after adding the intermediate layer, the welding gap disappears and no obvious intermediate layer can be seen, indicating that the addition of the nickel powder-nickel foil intermediate layer effectively improves the GH4169 diffusion bonding interface.

[0082] Figure 43. The figures are comparison diagrams before and after shear test of shear specimens obtained after diffusion bonding of GH4169 high-temperature alloy under different conditions. In the figure, (a) is GH4169 high-temperature alloy without an intermediate layer and diffusion-bonded using the existing overall current heating, (b) is GH4169 high-temperature alloy with a nickel foil intermediate layer added and diffusion-bonded using the existing overall current heating, (c) is GH4169 high-temperature alloy in Example 1 with a nickel foil-nickel powder intermediate layer added and diffusion-bonded using local current heating, (d) is GH4169 high-temperature alloy in Control Example 1 with a nickel foil added and diffusion-bonded using local current heating, and (e) is GH4169 high-temperature alloy in Control Example 2 with a nickel powder intermediate layer added and diffusion-bonded using the existing overall current heating.

[0083] According to the shear test results, the interface shear strength of the GH4169 high-temperature alloy without an intermediate layer using the existing overall current heating diffusion connection is only 80 MPa, and the interface shear strength of the GH4169 high-temperature alloy with nickel foil as the intermediate layer is 298 MPa. The interface shear strength of the GH4169 high-temperature alloy with nickel foil-nickel powder as the intermediate layer using the local current heating diffusion connection described in Example 1 can reach 320 MPa. The interface shear strength of the GH4169 high-temperature alloy using the control example 1 to add nickel foil and use local current heating diffusion connection is 300 MPa, and the interface shear strength of the GH4169 high-temperature alloy using the control example 2 to add a nickel powder intermediate layer and use overall current heating diffusion connection is 287 MPa.

[0084] It can be seen from this that the local current heating diffusion bonding method for high-temperature alloys described in Example 1 effectively concentrates heat in the interface contact area, greatly improving energy utilization. In addition, due to the rapid heating of powder particles and the presence of plasma, the time required for diffusion bonding is also shorter and the work efficiency is higher.

Claims

1. A method for local current heating diffusion bonding of large-sized high-temperature alloys with foil-powder intermediate layers, characterized in that The method is specifically completed according to the following steps:

1. The surfaces of the high-temperature alloy to be diffusion-bonded are polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy parts to be diffusion-bonded; 2. Cutting the nickel foil into a rectangle having the same width as the high-temperature alloy to be diffusion-bonded and a length slightly longer than the high-temperature alloy to be diffusion-bonded to obtain the cut nickel foil; adding nickel powder to ethylene glycol and mixing them evenly to obtain a paste coating; applying the paste coating to the surfaces to be diffusion-bonded of the two high-temperature alloy to be diffusion-bonded, respectively; and then placing the two high-temperature alloy to be diffusion-bonded in a vacuum drying oven until completely dried, to obtain two high-temperature alloy to be diffusion-bonded coated with nickel powder; 3. Align the surfaces of two high-temperature alloy pieces coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces, ensuring that the upper and lower surfaces of the nickel foil are flush with the surfaces and that the left and right ends extend the same length beyond the surfaces. Fourth, perform edge sealing welding on the two parts to be diffusion connected, and leave an exhaust hole; weld the exhaust pipe to the exhaust hole, and install a vacuum gauge and a valve on the exhaust pipe; perform air tightness test on the parts to be diffusion connected after edge sealing welding, and vacuumize the parts to be diffusion connected with good air tightness, close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the parts to be diffusion connected after vacuuming; The position of the exhaust hole described in step 4 is left above or below the diffusion connection surface; 5. First, place the pad, the pressure-resistant insulating block, the part to be diffused and connected after vacuuming, the pressure-resistant insulating block, and the pad from bottom to top on the platform inside the hydraulic press. Then, clamp the two copper electrodes on the two electrode clamps respectively. Then, connect the two copper electrodes to the positive and negative poles of the DC power supply respectively. Finally, connect the two electrode clamps to the nickel foil exposed on the left and right sides of the part to be diffused and connected respectively.

6. Turn on the hydraulic press and apply pressure to the diffusion connection piece after vacuuming until the pressure reaches the predetermined pressure value and keep the pressure constant; 7. Control the operation of the circulating water system to keep the water temperature outside the water-cooling wire at threshold A; 8. Connect the exhaust pipe of the diffusion joint to the vacuum pump, open the valve, and continue to vacuum; 9. After the vacuum reaches a certain value, control the DC power supply to start, so that the temperature of the surface to be diffused and connected rises steadily at a certain rate until the temperature of the surface to be diffused and connected meets the temperature required for diffusion bonding. -2 Perform local current heating diffusion bonding of high temperature alloy parts to be diffusion bonded under Pa; 10. After the diffusion bonding is completed, turn off the DC power supply, then raise the hydraulic press to stop maintaining pressure, stop vacuuming after cooling to a certain temperature, close the valve and take out the final high-temperature alloy diffusion bonded parts.

2. The method of local current heating diffusion bonding of large-sized high-temperature alloys with foil-powder intermediate layers according to claim 1, characterized in that The high-temperature alloy described in step 1 is a nickel-based high-temperature alloy or a nickel-aluminum alloy; the polishing described in step 1 is performed by sequentially using 180-mesh, 400-mesh and 800-mesh sandpaper.

3. The method of local current heating diffusion bonding of large-sized high-temperature alloys with foil-powder intermediate layers according to claim 1, characterized in that The particle size of the nickel powder in step 2 is 5 μm to 15 μm; the thickness of the nickel foil in step 2 is 30 μm to 50 μm.

4. The method of local current heating diffusion bonding of large-sized high-temperature alloys with a foil-powder intermediate layer according to claim 1, characterized in that The length of the cut nickel foil described in step 2 is 5 cm to 8 cm longer than the length of the high-temperature alloy to be diffusion-connected; the volume ratio of the nickel powder mass to ethylene glycol in the paste coating described in step 2 is (30 g to 50 g): (20 mL to 25 mL).

5. The method of local current heating diffusion bonding of large-sized high-temperature alloys with a foil-powder intermediate layer according to claim 1, characterized in that The ratio of the mass of the paste coating in step 2 to the surface area of ​​the high-temperature alloy to be diffusely bonded is (5g to 10g): (10cm 2 ~15cm 2 ); the temperature of the vacuum drying oven in step 2 is 50°C to 70°C.

6. The method of local current heating diffusion bonding of large-sized high-temperature alloys with a foil-powder intermediate layer according to claim 1, characterized in that Step 4: When the vacuum degree is 1×10 -1 When it reaches Pa, close the valve and stop vacuuming.

7. The method of local current heating diffusion bonding of large-sized high-temperature alloys with a foil-powder intermediate layer according to claim 1, characterized in that The material of the electrode clamp described in step five is copper; the material of the pressure-resistant insulating block described in step five is phenolic resin.

8. The method of local current heating diffusion bonding of large-sized high-temperature alloys with a foil-powder intermediate layer according to claim 1, characterized in that The predetermined pressure value in step six is ​​30 MPa to 50 MPa; the temperature of the threshold value A in step seven is 22° C. to 25° C.

9. The method of local current heating diffusion bonding of large-sized high-temperature alloys with a foil-powder intermediate layer according to claim 1, characterized in that In step nine, wait until the vacuum degree reaches 1×10 -2 Pa when controlling the DC power supply to turn on; the output current of the DC power supply described in step nine is 0 ~ 10000A, the output voltage is 0 ~ 8V, and the output frequency is 0 ~ 40kHz; the temperature rise rate at the surface to be diffused and connected described in step nine is 200℃ / min ~ 300℃ / min.

10. The method of local current heating diffusion bonding of large-sized high-temperature alloys with foil-powder intermediate layers according to claim 1, characterized in that The diffusion bonding described in step nine requires a temperature of 900° C. to 1200° C.; the time for the local current heating diffusion bonding described in step nine is 15 min to 60 min; and the vacuuming is stopped after the temperature is lowered to 200° C. to 300° C. in step ten.

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