Method for local current heating diffusion bonding of large-size high-temperature alloy of foil-powder middle layer

Abstract

The invention discloses a method for local current heating diffusion bonding of large-size high-temperature alloy of a foil-powder middle layer, and relates to the technical field of diffusion bonding of large-size high-temperature alloy materials. The invention aims to solve the problems that the existing large-size high-temperature alloy current heating diffusion bonding process is large in electric energy loss and low in energy utilization rate, and the comprehensive mechanical property of an original material is reduced after heating for a certain time. The method comprises the steps of 1, polishing; 2, preparing two high-temperature alloy to-be-diffused connecting pieces coated with nickel powder; 3, clamping the nickel foil between the two to-be-diffused connecting pieces; 4, carrying out edge sealing welding on the two to-be-diffused connecting pieces, and vacuumizing; 5, assembling and connecting; 6, applying pressure; 7, controlling a circulating water system to work; 8, vacuumizing; 9, controlling the starting of a direct-current power supply, and carrying out local current heating diffusion bonding; and 10, cooling. The problem that the comprehensive mechanical property of an original material is reduced after the original material is heated for a certain time is solved.

Description

Technical Field

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

[0002] With the continuous development of my country's aerospace and other cutting-edge industries, 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 complexity of the alloy system of high-temperature alloys, in addition to the elements Fe, Co, and Ni as the matrix, it also contains a large amount of strengthening elements, which brings great difficulties to the connection of high-temperature alloys. Problems such as cracks and reduced strength are very likely to occur during fusion welding. Even if high-energy density fusion welding methods such as lasers or electron beams are used, it is difficult to avoid defects such as cracks. Therefore, it is generally believed that it is best to use non-melting methods to connect high-temperature alloys, which can fundamentally solve the problems caused by fusion welding. Diffusion bonding is a more effective and promising process method for non-melting connection of high-temperature alloys.

[0003] The traditional diffusion bonding process requires the material to be heated for a long time at high temperature, which not only seriously wastes electrical energy, but also increases the manufacturing requirements and costs of heating equipment. In addition, the material's grain size grows significantly and the surface is severely oxidized under long-term heat exposure conditions, which not only makes it difficult to perform diffusion bonding, but also greatly reduces the comprehensive mechanical properties of the original material.

[0004] In recent years, welding processes using electric current heating have continued to emerge. The advantage of using the Joule heating effect of electric current to make the current-carrying conductor reach a higher temperature in a very short time can effectively solve the problem of poor welding performance of some difficult-to-weld materials. For example, the invention patent "A current-heated diffusion connection device and method" published in 2020 uses current heating to diffuse and connect the plates. However, high-temperature alloys are difficult-to-deform materials, and the physical contact effect during diffusion connection is poor. The pressure required to achieve close contact is increased and the time is long, and the diffusion connection process requires a high temperature. The addition of an intermediate layer can effectively improve surface contact, reduce the pressure during diffusion connection, and at the same time reduce the connection temperature and the diffusion connection time. For example, in the invention patent "A SPS diffusion welding method for DD98-like nickel-based single crystal high-temperature alloy" published in 2022, Ni-Cr-WB-Si-Fe powder brazing material is used as an intermediate transition layer, and the DD98-like nickel-based single crystal high-temperature alloy is effectively connected at a lower temperature and in a shorter time through spark plasma sintering technology. However, the above still heats the material as a whole, which not only takes a long time and has low energy utilization, but also reduces the overall performance of the material. Local current heating can effectively improve the above situation. For example, in the utility model patent "A pulse current assisted local high temperature diffusion connection device of titanium alloy" published in 2014, local current diffusion connection of titanium alloy is adopted.

[0005] However, the current local current heating diffusion bonding process still applies current directly to the material to be diffused and connected, and gradually transfers the Joule heat generated by the current on the material to the surface to be diffused and connected. Compared with overall heating, the current loading method has not changed. This is still a serious problem for large-size high-temperature alloy current heating diffusion bonding, and the problem of high power loss and low energy utilization is still serious. In addition, the heat is still transferred from the original material to the surface to be diffused and connected, and the comprehensive mechanical properties of the material will still decrease 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 reduction of comprehensive mechanical properties of original materials after a certain period of heating in the existing large-size high-temperature alloy current heating diffusion connection process, and to provide a method for local current heating diffusion connection of large-size high-temperature alloy foil-powder intermediate layer.

[0007] A method for locally heating and diffusing a large-size high-temperature alloy to connect a foil-powder intermediate layer is specifically completed in the following steps:

[0008] 1. The surface of the high-temperature alloy to be diffused and connected is polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy part to be diffused and connected;

[0009] 2. Cut the nickel foil into a rectangle with the same width as the high-temperature alloy to be diffused and connected and slightly longer than the high-temperature alloy to be diffused and connected, to obtain the cut nickel foil; add nickel powder to ethylene glycol and mix evenly to obtain a paste coating; apply the paste coating to the surfaces to be diffused and connected of the two high-temperature alloy to be diffused and connected, respectively, and then put the two high-temperature alloy to be diffused and connected into a vacuum drying oven until they are completely dried, to obtain two high-temperature alloy to be diffused and connected coated with nickel powder;

[0010] 3. Align the surfaces of two high-temperature alloy pieces to be diffused and connected coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces to be diffused and connected, so that the upper and lower surfaces of the nickel foil are flush with the surfaces to be diffused and connected, and the lengths of the left and right ends extending from the surfaces to be diffused and connected are the same;

[0011] Fourth, perform edge sealing welding on two pieces to be diffused and 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 pieces to be diffused after edge sealing welding, and perform vacuum treatment on the pieces to be diffused with good air tightness, and close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the pieces to be diffused after vacuuming is completed;

[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 cushion block, the pressure-resistant insulating block, the diffusion connection piece after vacuuming, the pressure-resistant insulating block, and the cushion block from bottom to top on the platform in the hydraulic press, and then clamp the two copper electrodes on the two electrode clamping plates respectively, and then connect the two copper electrodes to the positive and negative electrodes of the DC power supply respectively, and finally connect the two electrode clamping plates to the nickel foil exposed on the left and right sides of the diffusion connection piece respectively;

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

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

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

[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 required temperature for diffusion connection. -2 Local current heating diffusion connection of high temperature alloy parts to be diffusion connected under Pa;

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

[0019] Principles and advantages of the present invention:

[0020] Based on the existing current heating diffusion connection process, the present invention changes the existing current loading mode, directly clamps the electrode in the middle layer (nickel foil), and uses the Joule heating effect principle of the current. The resistance of the diffusion connection surface of the diffusion connection piece is much greater than that of other areas, so that most of the heat is concentrated on the diffusion connection surface, which greatly improves the energy utilization rate and avoids the problem of reduced comprehensive mechanical properties of the original material after a certain period of heating. In addition, the present invention also uses foil-powder as the middle layer. The powder will be instantly heated to a high temperature state under the action of the pulse current, and plasma will be generated at the same time. These plasmas will be quickly transmitted between the powder particles, so that the entire diffusion connection surface is evenly heated. Due to the rapid heating of the powder particles and the presence of plasma, the diffusion connection process of the material can be completed quickly, while reducing the temperature requirements and avoiding excessive growth of grains. Moreover, the overall process device is simple, and the automation and scale of the process can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is a front view of the device required for a method of local current heating diffusion bonding foil-powder intermediate layer high temperature alloy in Example 1, in which 1 is a hydraulic press, 2 is a 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 cushion block, 8 is a nickel foil, and 9 is a pressure-resistant insulating block;

[0022] Figure 2 It is a side view of the device required in a method for local current heating diffusion bonding of a foil-powder intermediate layer of a high-temperature alloy in Example 1, in which 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 morphology of the GH4169 high temperature alloy in Example 1 after local current heating diffusion connection between the nickel powder and nickel foil intermediate layer;

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

[0025] Specific implementation method 1: This implementation method is a method for locally heating and diffusing a large-size high-temperature alloy with a foil-powder intermediate layer, which is specifically completed in the following steps:

[0026] 1. The surface of the high-temperature alloy to be diffused and connected is polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy part to be diffused and connected;

[0027] 2. Cut the nickel foil into a rectangle with the same width as the high-temperature alloy to be diffused and connected and slightly longer than the high-temperature alloy to be diffused and connected, to obtain the cut nickel foil; add nickel powder to ethylene glycol and mix evenly to obtain a paste coating; apply the paste coating to the surfaces to be diffused and connected of the two high-temperature alloy to be diffused and connected, respectively, and then put the two high-temperature alloy to be diffused and connected into a vacuum drying oven until they are completely dried, to obtain two high-temperature alloy to be diffused and connected coated with nickel powder;

[0028] 3. Align the surfaces of two high-temperature alloy pieces to be diffused and connected coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces to be diffused and connected, so that the upper and lower surfaces of the nickel foil are flush with the surfaces to be diffused and connected, and the lengths of the left and right ends extending from the surfaces to be diffused and connected are the same;

[0029] Fourth, perform edge sealing welding on two pieces to be diffused and 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 pieces to be diffused after edge sealing welding, and perform vacuum treatment on the pieces to be diffused with good air tightness, and close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the pieces to be diffused after vacuuming is completed;

[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 cushion block, the pressure-resistant insulating block, the diffusion connection piece after vacuuming, the pressure-resistant insulating block, and the cushion block from bottom to top on the platform in the hydraulic press, and then clamp the two copper electrodes on the two electrode clamping plates respectively, and then connect the two copper electrodes to the positive and negative electrodes of the DC power supply respectively, and finally connect the two electrode clamping plates to the nickel foil exposed on the left and right sides of the diffusion connection piece respectively;

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

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

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

[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 required temperature for diffusion connection. -2 Local current heating diffusion connection of high temperature alloy parts to be diffusion connected under Pa;

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

[0037] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the high temperature alloy described in step 1 is a nickel-based high temperature alloy or a nickel-aluminum alloy; the grinding described in step 1 is grinding with 180 mesh, 400 mesh and 800 mesh sandpaper in sequence. The other steps are the same as those in specific implementation method 1.

[0038] Specific implementation method 3: This implementation method is different from specific implementation method 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 implementation method 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 diffusely connected; the mass 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). The 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 drops to 0.5 Pa, the valve is closed to stop vacuuming. The other steps are the same as those in the first to fifth embodiments.

[0042] Specific implementation method 7: This implementation method is different from specific implementation methods 1 to 6 in that: the material of the electrode clamp described in step 5 is copper; the material of the pressure-resistant insulating block described in step 5 is phenolic resin. The other steps are the same as specific implementation methods 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 the threshold value A in step 7 is 22° C. to 25° C. The other steps are the same as those in specific embodiments 1 to 7.

[0044] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: in step 9, when the vacuum degree reaches 1×10 -2 The DC power supply is controlled to be turned on at Pa; the output current of the DC power supply in step nine is 0 to 10000A, the output voltage is 0 to 8V, and the output frequency is 0 to 40kHz; the temperature rise rate at the surface to be diffused and connected in step nine is 200°C / min to 300°C / min. The other steps are the same as those in specific embodiments one to eight.

[0045] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that: the diffusion connection described in step 9 requires a temperature of 900°C to 1200°C; the time for the local current heating diffusion connection described in step 9 is 15min to 60min; and the vacuuming is stopped after the temperature drops to 200°C to 300°C in step 10. The other steps are the same as those of specific embodiments 1 to 9.

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

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

[0048] 1. The surface of the high-temperature alloy to be diffused and connected is polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy part to be diffused and connected;

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

[0050] The grinding described in step 1 is to use 180 mesh, 400 mesh and 800 mesh sandpaper for grinding in sequence;

[0051] 2. Cut the nickel foil into a rectangle with the same width as the high-temperature alloy to be diffused and connected and slightly longer than the high-temperature alloy to be diffused and connected, to obtain the cut nickel foil; add nickel powder to ethylene glycol and mix evenly to obtain a paste coating; apply the paste coating to the surfaces to be diffused and connected of the two high-temperature alloy to be diffused and connected, respectively, and then put the two high-temperature alloy to be diffused and connected into a vacuum drying oven until they are completely dried, to obtain two high-temperature alloy to be diffused and connected 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 cut nickel foil in step 2 is 6 cm longer than the length of the high-temperature alloy to be diffused and connected;

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

[0056] 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 10 g: 15 cm 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 to be diffused and connected coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces to be diffused and connected, so that the upper and lower surfaces of the nickel foil are flush with the surfaces to be diffused and connected, and the lengths of the left and right ends extending from the surfaces to be diffused and connected are the same;

[0059] Fourth, perform edge sealing welding on two pieces to be diffused and 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 pieces to be diffused after edge sealing welding, and perform vacuum treatment on the pieces to be diffused with good air tightness, and close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the pieces to be diffused after vacuuming is completed;

[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 cushion block, the pressure-resistant insulating block, the diffusion connection piece after vacuuming, the pressure-resistant insulating block, and the cushion block from bottom to top on the platform in the hydraulic press, and then clamp the two copper electrodes on the two electrode clamping plates respectively, and then connect the two copper electrodes to the positive and negative electrodes of the DC power supply respectively, and finally connect the two electrode clamping plates to the nickel foil exposed on the left and right sides of the diffusion connection piece respectively;

[0063] The electrode clamp 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 to apply pressure to the diffused connection piece after vacuuming until the pressure reaches the predetermined pressure value and keep the pressure;

[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 value A;

[0068] The temperature of the threshold value 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 evacuate;

[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 required temperature for diffusion connection. -2Local current heating diffusion connection of high temperature alloy parts to be diffusion connected 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 0-10000A, the output voltage is 0-8V, and the output frequency is 0-40kHz;

[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 connection is completed, turn off the DC power supply, then raise the hydraulic press to stop the pressure maintenance, stop the vacuum after cooling to a certain temperature, close the valve and take out the final high-temperature alloy diffusion connection part;

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

[0078] Comparative Example 1: The difference between this embodiment and Example 1 is that the nickel powder is omitted, that is, in step 2, the nickel foil is cut into a rectangle with the same width as the high-temperature alloy to be diffused and connected, and the length is slightly longer than the high-temperature alloy to be diffused and connected, to obtain the cut nickel foil; in step 3, the surfaces to be diffused and connected of the two high-temperature alloy to be diffused and connected are opposite to each other and the cut nickel foil is sandwiched between the two to be diffused and connected, so that the upper and lower surfaces of the nickel foil are flush with the surfaces to be diffused and connected, and the length of the left and right ends extending from the surfaces to be diffused and connected is the same. Other steps and parameters are the same as those 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 morphology of the GH4169 high temperature alloy in Example 1 after local current heating diffusion connection 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 4The figures are comparison diagrams of shear specimens obtained after diffusion bonding of GH4169 high-temperature alloy under different conditions before and after shear test, in which (a) is GH4169 high-temperature alloy without intermediate layer and diffusion bonded by existing overall current heating, (b) is GH4169 high-temperature alloy with nickel foil intermediate layer added and diffusion bonded by existing overall current heating, (c) is GH4169 high-temperature alloy in Example 1 with nickel foil-nickel powder intermediate layer added and diffusion bonded by local current heating, (d) is GH4169 high-temperature alloy in Control Example 1 with nickel foil added and diffusion bonded by local current heating, and (e) is GH4169 high-temperature alloy in Control Example 2 with nickel powder intermediate layer added and diffusion bonded by existing overall current heating.

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

[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, and 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 locally heating and diffusing a large-size high-temperature alloy with a foil-powder intermediate layer, characterized in that The method is specifically completed according to the following steps:

1. The surface of the high-temperature alloy to be diffused and connected is polished step by step, and then ultrasonically cleaned in anhydrous ethanol to obtain the high-temperature alloy part to be diffused and connected; 2. Cut the nickel foil into a rectangle with the same width as the high-temperature alloy to be diffused and connected and slightly longer than the high-temperature alloy to be diffused and connected, to obtain the cut nickel foil; add nickel powder to ethylene glycol and mix evenly to obtain a paste coating; apply the paste coating to the surfaces to be diffused and connected of the two high-temperature alloy to be diffused and connected, respectively, and then put the two high-temperature alloy to be diffused and connected into a vacuum drying oven until they are completely dried, to obtain two high-temperature alloy to be diffused and connected coated with nickel powder; 3. Align the surfaces of two high-temperature alloy pieces to be diffused and connected coated with nickel powder with each other and sandwich the cut nickel foil between the two pieces to be diffused and connected, so that the upper and lower surfaces of the nickel foil are flush with the surfaces to be diffused and connected, and the lengths of the left and right ends extending from the surfaces to be diffused and connected are the same; Fourth, perform edge sealing welding on two pieces to be diffused and 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 pieces to be diffused after edge sealing welding, and perform vacuum treatment on the pieces to be diffused with good air tightness, and close the valve after the vacuum reaches a certain value, stop vacuuming, and obtain the pieces to be diffused after vacuuming is completed; The position of the exhaust hole described in step 4 is left above or below the diffusion connection surface; 5. First, place the cushion block, the pressure-resistant insulating block, the diffusion connection piece after vacuuming, the pressure-resistant insulating block, and the cushion block from bottom to top on the platform in the hydraulic press, and then clamp the two copper electrodes on the two electrode clamping plates respectively, and then connect the two copper electrodes to the positive and negative electrodes of the DC power supply respectively, and finally connect the two electrode clamping plates to the nickel foil exposed on the left and right sides of the diffusion connection piece respectively; 6. Turn on the hydraulic press to apply pressure to the diffused connection piece after vacuuming until the pressure reaches the predetermined pressure value and keep the pressure; 7. Control the operation of the circulating water system to keep the water temperature outside the water-cooling wire at threshold value A; 8. Connect the exhaust pipe of the diffusion joint to the vacuum pump, open the valve, and continue to evacuate; 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 required temperature for diffusion connection. -2 Local current heating diffusion connection of high temperature alloy parts to be diffusion connected under Pa; 10. After the diffusion connection is completed, turn off the DC power supply, raise the hydraulic press and stop maintaining the pressure. After cooling to a certain temperature, stop vacuuming, close the valve and take out the final high-temperature alloy diffusion connection parts.

2. A method for locally heating and diffusing a large-size high-temperature alloy with a foil-powder intermediate layer 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 using 180 mesh, 400 mesh and 800 mesh sandpaper in sequence.

3. A method for locally heating and diffusion bonding a large-size high-temperature alloy of a foil-powder intermediate layer 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. A method for locally heating and diffusion bonding a large-size high-temperature alloy of 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 mass of nickel powder in the paste coating described in step 2 to ethylene glycol is (30 g to 50 g): (20 mL to 25 mL).

5. A method for locally heating and diffusion bonding a large-size high-temperature alloy of 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 (5 g to 10 g): (10 cm 2 ~15cm 2 ); the temperature of the vacuum drying oven described in step 2 is 50°C to 70°C.

6. A method for locally heating and diffusion bonding a large-size high-temperature alloy of 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. A method for locally heating and diffusion bonding a large-size high-temperature alloy of a foil-powder intermediate layer according to claim 1, characterized in that The electrode clamp described in step 5 is made of red copper; the pressure-resistant insulating block described in step 5 is made of phenolic resin.

8. 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 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. A method for locally heating and diffusion bonding a large-size high-temperature alloy of a foil-powder intermediate layer according to claim 1, characterized in that In step nine, wait until the vacuum degree reaches 1×10 -2 Control the DC power supply to start when Pa; 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. A method for locally heating and diffusion bonding a large-size high-temperature alloy of a foil-powder intermediate layer according to claim 1, characterized in that The diffusion connection described in step nine requires a temperature of 900°C to 1200°C; the time for the local current heating diffusion connection described in step nine is 15min to 60min; and the vacuuming is stopped after the temperature drops to 200°C to 300°C in step ten.

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