DD10 single-crystal high-temperature alloy connection method based on middle layer and magnetic field assistance

Abstract

The invention discloses a DD10 single-crystal high-temperature alloy connecting method based on an intermediate layer and magnetic field assistance, and belongs to the technical field of metal welding. According to the method, a NiCo22Cr20W10Mo7Ta5Ge5Re2Hf0. 8La0. 2 middle layer is adopted, the middle layer is arranged between an upper layer of DD10 single crystal high-temperature alloy and a lower layer of DD10 single crystal high-temperature alloy, diffusion bonding is conducted in a vacuum diffusion welding furnace embedded into a magnetic field generator, and a welding piece of the DD10 single crystal high-temperature alloy is obtained; under the synergistic effect of the two components, the microstructure and the physical and chemical process of the material are regulated and controlled, atomic diffusion is promoted, the microstructure is optimized, the effects of refining grains, controlling liquid level deformation and removing inclusions are achieved, the mechanical property of a joint is improved, the welding quality and efficiency are remarkably improved, and a low-temperature welding workpiece has the excellent performance of high-temperature service; and a high-reliability solution is provided for efficient welding manufacturing of the DD10 single-crystal high-temperature alloy of the aero-engine blade.

Description

Technical Field

[0001] The present invention relates to the technical field of metal welding, and particularly to a joining method for DD10 single-crystal superalloy based on an interlayer and magnetic field assistance. Background Art

[0002] With the increase in the thrust-to-weight ratio of aero-engines, the working conditions of high-pressure turbine blades become increasingly harsh. Complex aerodynamic, thermal stress, and mechanical loads, etc., can all cause blade failure. Therefore, it is crucial to select a material with good comprehensive performance. Nickel-based single-crystal superalloy DD10 has become the optimal choice for this component due to its excellent creep performance, stress rupture performance, and casting performance. Also, due to the special structure of the blade, how to effectively join DD10 single-crystal superalloy has become an urgent problem to be solved.

[0003] Regarding the joining technology of superalloys, traditional fusion welding methods often cause a tendency of hot cracks due to the high heat input, resulting in a significant decline in the mechanical properties of the joint; while the direct diffusion welding technology avoids the heat input problem of fusion welding, but in practical applications, it is prone to such interface bonding defects as lack of fusion and large-area pores. When using a conventional commercially available interlayer for transient liquid-phase diffusion welding, although low-temperature joining can be achieved by introducing melting-point-depressing elements B and Si, the resulting brittle compound phases will significantly weaken the joint strength. More prominently, in order to ensure sufficient diffusion of elements, the traditional transient liquid-phase diffusion welding process usually requires a holding time of more than several hours. Such inefficient process parameters not only increase the production cost but also seriously restrict the feasibility of industrial mass production.

[0004] Therefore, in response to the above challenges, the present invention completes the transient liquid-phase diffusion welding of nickel-based single-crystal superalloy DD10 by introducing a new type of interlayer and combining magnetic field-assisted welding, improving the welding efficiency while ensuring the mechanical properties of the joint. Summary of the Invention

[0005] Aiming at the deficiencies in the background art, the main purpose of the present invention is to improve the mechanical properties of the joint and increase the welding efficiency by introducing a newly designed interlayer and combining electromagnetic-assisted welding.

[0006] To achieve the above object, the present invention provides a joining method for DD10 single-crystal superalloy based on an interlayer and magnetic field assistance, including the following steps: Step 1: Prepare the interlayer; the atomic ratio of the elements in the interlayer is NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 ; Step 2: Embedding a magnetic field generator into the inner wall of the vacuum diffusion welding furnace; Step 3: Transient liquid phase diffusion welding; placing the intermediate layer obtained in Step 1 between the upper and lower DD10 single crystal superalloy base materials, and performing transient liquid phase diffusion welding in the vacuum diffusion welding furnace of Step 2. During the welding process, an alternating magnetic field is applied along the direction perpendicular to the welding surface to be welded, and heating is synchronized with the application of the magnetic field, and finally a welded part of DD10 single crystal superalloy is obtained.

[0007] Preferably, the process of preparing the intermediate layer in Step 1 is to weigh metal element particles Ni, Co, Cr, W, Mo, Ta, Ge, Re, Hf, La with a purity greater than 99.99 wt% according to the atomic ratio of the elements, clean them and put them into a melting furnace, melt them to obtain alloy bars, and then use the alloy melt spinning technology in a single-roll spinning machine to prepare an amorphous foil intermediate layer.

[0008] Preferably, the thickness of the amorphous foil intermediate layer is 50 μm - 80 μm.

[0009] Preferably, the temperature of the melting is 1300 °C.

[0010] Preferably, the process of preparing the amorphous foil intermediate layer by using the alloy melt spinning technology is as follows: encapsulating the alloy bars in a quartz tube, vertically fixing them at the center of the induction coil of the single-roll spinning machine, heating them to 150 °C above the liquidus of the alloy bars under the protection of a vacuum and argon atmosphere, and pressurizing and spraying the melt onto the surface of the copper roll to solidify and form an amorphous foil intermediate layer.

[0011] Preferably, the intensity of the magnetic field applied in Step 3 is 0.1 T - 0.5 T, and the magnetic field intensity gradient increases, and the alternating frequency is 30 HZ.

[0012] Preferably, the heating process in Step 3 adopts a segmented heating method. In the first stage, the vacuum diffusion welding furnace is heated from room temperature to 500 °C at a rate of 10 °C / min, and is held at 500 °C for 10 min, and the magnetic field is applied while the temperature rises to 300 °C. In the second stage, it is heated to 900 °C at a rate of 10 °C / min and held at 900 °C for 10 min. In the third stage, it is heated to the welding temperature of 1175 °C at a rate of 10 °C / min. In the fourth stage, it is held at the welding temperature of 1175 °C for 1 h, and a pressure of 5 MPa is applied for heat preservation and pressure holding.

[0013] Preferably, during the transient liquid phase diffusion welding process, when the heat preservation and pressure holding are completed, the pressure is unloaded first, and the welded part is cooled with the furnace. When the temperature of the vacuum diffusion welding furnace drops to 300 °C, the magnetic field generator is turned off, and when the temperature of the vacuum diffusion welding furnace drops to room temperature, the welding is completed.

[0014] Preferably, before the transient liquid phase diffusion welding in step three, the DD10 single crystal superalloy is polished successively with 400#-2000# sandpaper. After polishing, it is mechanically polished with a polishing solution and ultrasonically cleaned in absolute ethanol.

[0015] Preferably, the vacuum degree of the vacuum diffusion welding furnace in step three .

[0016] Compared with the prior art, the present invention has the following beneficial effects: Through the NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 interlayer and the magnetic field-assisted transient liquid phase diffusion welding of DD10 single crystal superalloy, the synergistic effect of the interlayer and the electromagnetic field regulates the material microstructure and physical and chemical processes, promotes atomic diffusion, optimizes the microstructure, plays a role in refining grains, controlling the liquid surface deformation and removing inclusions, improves the mechanical properties of the joint, significantly improves the welding quality and efficiency, enables the low-temperature welded workpiece to have excellent properties for high-temperature service. Through the combined action of the new interlayer and the magnetic field, the welding temperature can be appropriately reduced to achieve the effect of high-temperature welding, effectively improving the welding efficiency. Moreover, the non-contact nature of the electromagnetic assistance and the workpiece greatly broadens the application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the sample clamping before the transient liquid phase diffusion welding in Embodiment 1 of the present invention and the direction of the magnetic field applied during the welding process.

[0018] Figure 2 SEM micrograph of the joint microstructure after the transient liquid phase diffusion welding in Embodiment 1 of the present invention.

[0019] Figure 3 SEM micrograph of the joint microstructure in Comparative Example 1 of the present invention.

[0020] Figure 4 SEM micrograph of the joint microstructure in Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0022] The present invention provides a method for joining DD10 single-crystal superalloy based on an intermediate layer and magnetic field assistance, which specifically includes the following steps: Step 1: Polish the surface of the DD10 single-crystal superalloy to be welded successively with 400#, 600#, 1000#, 1500#, and 2000# sandpapers, polish it with 0.15 μm silica polishing solution until there are no obvious scratches on the surface, ultrasonically clean the polished alloy with anhydrous ethanol at a frequency of 20 kHz for 15 min, and dry it with a nitrogen gun to obtain the treated DD10 single-crystal superalloy base material; Step 2: Prepare an intermediate layer, and clamp the intermediate layer and the DD10 single-crystal superalloy base material according to the "base material - intermediate layer - base material" sandwich structure; The process of preparing the intermediate layer includes the following steps: Step 1: Weigh metal element particles Ni, Co, Cr, W, Mo, Ta, Ge, Re, Hf, and La with a purity greater than 99.99 wt%, clean the surface with dilute sulfuric acid solution, and place them in an alcohol solution for ultrasonic cleaning; 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 Step 2: Melting: Load the cleaned proportioned raw materials into an intermediate frequency induction melting furnace, start the mechanical pump and Roots pump in sequence to create a vacuum environment, then fill high-purity argon as a protective atmosphere in sequence, maintain dynamic air pressure balance, activate the intermediate frequency power supply for gradient heating, and implement slag removal and refining treatment by combining electromagnetic stirring and flux covering technology during the heating process to eliminate non-metallic inclusions and complete the alloying melting process; The above process is repeated three times, poured into a mold, and cooled to obtain alloy bars with consistent specifications; The melting temperature is 1300 °C; Step 3: Spinning: Enclose the alloy bar in a high-purity quartz tube, vertically fix it at the center of the induction coil of a single-roll spinning machine, interlock and start the vacuum system and then fill high-purity argon for protection, heat it by intermediate frequency induction to 150 °C above the liquidus of the alloy, pressurize and spray the melt onto the surface of a rapidly rotating copper roll, and rapidly solidify to form an amorphous foil intermediate layer with a thickness of 50 μm - 80 μm. The required process parameters are: the diameter of the beryllium copper is 400 mm, the rotation speed of the copper roll is 1800 rpm, the cooling rate is greater than 106 °C / sec; the width of the nozzle is 12 mm, the aperture is 1.5 mm; the distance between the nozzle and the surface of the copper roll is 0.5 mm; the argon injection pressure is 45 KPa; Step 3: Modification of the vacuum diffusion welding furnace cavity: As Step 3: Modification of the vacuum diffusion welding furnace cavity: As Figure 1As shown in the figure, a magnetic field generator is embedded in the inner wall of the vacuum diffusion welding furnace to facilitate the application of the magnetic field. An alternating magnetic field is selected as the type of applied magnetic field, and the direction of the magnetic field is perpendicular to the surface to be welded. The magnetic field intensity is adjusted. For the magnetic field-assisted transient liquid phase diffusion welding test, the magnetic field intensity needs to be strictly controlled. The magnetic field intensity is 0.1 - 0.5 T. For example, it can be 0.1 T, 0.2 T, 0.3 T, 0.4 T, 0.5 T, and the alternating frequency is 30 HZ to avoid the deterioration of the joint performance caused by the imbalance of the magnetic field intensity.

[0023] Step 4: Place the "base material - interlayer - base material" structure in Step 2 into the reformed vacuum diffusion welding furnace in Step 3 for transient liquid phase diffusion welding; During the welding process, the application of the magnetic field needs to be synchronized with the heating, and at the same time, the magnetic field intensity gradient is applied. During the heating process, in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 500 °C at a rate of 10 °C / min and kept at 500 °C for 10 min. It should be noted that the magnetic field is applied while the temperature rises to 300 °C. In the second stage, it is heated to 900 °C at a rate of 10 °C / min and kept at 900 °C for 10 min. In the third stage, it is heated to the welding temperature of 1175 °C at a rate of 10 °C / min. In the fourth stage, it is kept at the welding temperature of 1175 °C for 1 h, and a pressure of 5 MPa is applied for heat preservation and pressure holding. When the heat preservation and pressure holding are completed, the pressure is unloaded first, and the welded part is cooled with the furnace. When the temperature of the vacuum diffusion welding furnace drops to 300 °C, the magnetic field generator is turned off. When the temperature of the vacuum diffusion welding furnace drops to room temperature, the welding is completed. The vacuum degree during the whole welding process is always not higher than .

[0024] In some embodiments of the present invention, during the transient liquid phase diffusion welding process, NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2The functions of the elements in the intermediate layer during the welding process and their synergistic effects with the magnetic field are as follows: During the welding process, Ni-Co-Cr forms the main framework, forming a continuous compositional transition with the DD10 base material. The Ni / Co matrix forms a continuous solid solution during welding, significantly reducing the interfacial lattice mismatch degree, and at the same time promoting the mutual diffusion of elements between the base material and the intermediate layer, effectively alleviating the interfacial residual stress; W and Mo, as the main solid solution strengthening elements, form stable solid solutions in the γ-phase matrix, strengthening through lattice distortion caused by atomic size differences; The Re element, relying on its unique grain boundary segregation characteristics, forms dislocation obstacles in the interface region, synergistically improving the high-temperature creep resistance of the joint; The introduction of Ge element reduces the liquidus temperature of the alloy, forming a controllable transient liquid phase layer at the initial stage of welding; Combined with the magnetic field-assisted process, this liquid phase layer can optimize the solute distribution during isothermal solidification, inhibit the formation of brittle intermetallic compounds, and promote dense metallurgical bonding; The Ta-Hf-La multi-element system will form an oxide layer during high-temperature oxidation, and the oxide constitutes a dense barrier layer, significantly improving the antioxidant stability of the joint in a high-temperature environment; At the same time, during the welding process, by applying an electromagnetic field, the spreading and gap filling behaviors of the liquid intermediate layer can be promoted, improving the wettability; The flow velocity of the liquid intermediate layer is proportional to the peak current and the static magnetic field strength; Applying an electromagnetic field can regulate the material microstructure and physical and chemical processes, promote atomic diffusion, optimize the microstructure, play a role in refining grains, controlling the liquid surface deformation and removing inclusions, realizing the improvement of the mechanical properties of the joint, and ensuring the welding quality and efficiency.

[0025] The following further illustrates the present invention in conjunction with embodiments.

[0026] Example 1 This example uses NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 as the intermediate layer, and at the same time apply a magnetic field to assist in the transient liquid phase diffusion welding of the nickel-based single crystal superalloy DD10. The specific steps are as follows: Step 1: The surface of the DD10 single crystal superalloy to be welded is polished successively with 400#, 600#, 1000#, 1500#, and 2000# sandpapers, polished with 0.15 μm silica polishing liquid until there are no obvious scratches on the surface, ultrasonically cleaned with absolute ethanol for 15 min at a frequency of 20 kHz, and dried with a nitrogen gun to obtain the treated DD10 single crystal superalloy base material; Step 2: Prepare the intermediate layer and clamp the intermediate layer and the DD10 single crystal superalloy base material according to the "base material - intermediate layer - base material" sandwich structure; The process of preparing the intermediate layer includes the following steps: Step 1: According to the atomic ratio of elements NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 Weigh metal element particles Ni, Co, Cr, W, Mo, Ta, Ge, Re, Hf, La with a purity greater than 99.99 wt%, clean the surface with dilute sulfuric acid solution, and place them in an alcohol solution for ultrasonic cleaning; Step 2: Melting: Load the cleaned proportioned raw materials into an intermediate frequency induction melting furnace. Start the mechanical pump and roots pump in sequence to create a vacuum environment, and then fill high-purity argon as a protective atmosphere in sequence to maintain dynamic pressure balance. Activate the intermediate frequency power supply for gradient heating. During the heating process, use electromagnetic stirring combined with flux covering technology to carry out slag removal and refining treatment to eliminate non-metallic inclusions and complete the alloying melting process; The above process is repeated three times, poured into a mold, and cooled to obtain alloy bars with consistent specifications; The melting temperature is 1300 °C; Step 3: Spinning: Seal the alloy bar in a high-purity quartz tube, vertically fix it at the center of the induction coil of a single-roll spinning machine. After interlocking and starting the vacuum system, fill high-purity argon for protection. Induction heating with intermediate frequency to 150 °C above the liquidus of the alloy, and pressurize and spray the melt onto the surface of a rapidly rotating copper roll to form a 65-μm-thick amorphous foil belt intermediate layer by rapid solidification. The required process parameters are: the diameter of the beryllium copper is 400 mm, the rotational speed of the copper roll is 1800 rpm, and the cooling rate is greater than 106 °C / sec; the width of the nozzle is 12 mm, and the orifice diameter is 1.5 mm; the distance between the nozzle and the surface of the copper roll is 0.5 mm; the argon injection pressure is 45 KPa.

[0027] Step Three: Transformation of the vacuum diffusion welding furnace cavity: As Figure 1 shown, embed a magnetic field generator on the inner wall of the vacuum diffusion welding furnace to facilitate the application of the magnetic field. Select an alternating magnetic field as the type of applied magnetic field, with the direction of the magnetic field perpendicular to the welding surface, and adjust the magnetic field intensity. For the magnetic-assisted transient liquid phase diffusion welding test, the magnetic field intensity needs to be strictly controlled to ensure that the magnetic field intensity remains between 0.1 - 0.5 T, and the alternating frequency is 30 HZ, to avoid the deterioration of joint performance caused by magnetic field intensity imbalance.

[0028] Step Four: Place the "base material - intermediate layer - base material" structure in Step Two into the transformed vacuum diffusion welding furnace in Step Three for transient liquid phase diffusion welding; During the welding process, the magnetic field application process needs to be carried out simultaneously with the heating, and the magnetic field intensity gradient is applied at the same time; during the heating process, in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 500℃ at a rate of 10℃ / min, and kept at 500℃ for 10min. It is worth noting that the magnetic field is applied while the temperature rises to 300℃. In the second stage, the temperature is increased to 900℃ at a rate of 10℃ / min, and kept at 900℃ for 10min. In the third stage, the temperature is increased to the welding temperature of 1175℃ at a rate of 10℃ / min. In the fourth stage, the welding temperature is kept at 1175℃ for 1h, and a pressure of 5MPa is applied for insulation and pressure maintenance; at the end of insulation and pressure maintenance, the pressure is unloaded first, and the welded parts are cooled with the furnace. When the temperature of the vacuum diffusion welding furnace drops to 300℃, the magnetic field generator is turned off. When the temperature of the vacuum diffusion welding furnace drops to room temperature, the welding is completed. The vacuum degree during the entire welding process is always no higher than , the welded parts of DD10 single crystal high temperature alloy are obtained, and the microstructure of the joint is as follows Figure 2 As shown; the mechanical properties of the welded joint of this embodiment are tested using an INSTRON3382 electronic universal material testing machine, and the shear strength of the joint can reach 857MPa.

[0029] Example 2 This embodiment uses NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 As an intermediate layer, a magnetic field is applied to assist in transient liquid phase diffusion welding of nickel-based single crystal high-temperature alloy DD10, wherein the process of preparing the intermediate layer includes the following steps: Step 1: According to the atomic ratio of the elements, NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 Weigh metal element particles Ni, Co, Cr, W, Mo, Ta, Ge, Re, Hf, and La with a purity greater than 99.99 wt%, clean the surface with a dilute sulfuric acid solution, and place in an alcohol solution for ultrasonic cleaning; Step 2, smelting: the cleaned proportioned raw materials are loaded into the medium frequency induction melting furnace, the mechanical pump and the Roots pump are started in turn to create a vacuum environment, and then high-purity argon gas is filled in turn as a protective atmosphere to maintain dynamic air pressure balance, and the medium frequency power supply is activated for gradient heating. During the heating process, electromagnetic stirring combined with flux covering technology is used to implement slag removal and refining treatment to eliminate non-metallic inclusions and complete the alloying smelting process; the above process is repeated three times, poured into a mold, and cooled to obtain alloy bars with consistent specifications; the smelting temperature is 1300°C; Step 3, strip casting: Enclose the alloy bar in a high-purity quartz tube, vertically fix it at the center of the induction coil of a single-roll strip casting machine, interlock and start the vacuum system, then fill it with high-purity argon for protection. Inductively heat it with medium frequency to 150 °C above the liquidus of the alloy, and spray the melt onto the surface of a rapidly rotating copper roll under pressure. Rapid solidification forms an amorphous foil intermediate layer with a thickness of 50 μm. The remaining steps are the same as those in Example 1.

[0030] Use an INSTRON 3382 electronic universal material testing machine to detect the mechanical properties of the welded joints in this example. The shear strength of the joints can reach 845 MPa.

[0031] Example 3 This example uses NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 as the intermediate layer, and at the same time apply a magnetic field to assist in the transient liquid-phase diffusion welding of nickel-based single-crystal superalloy DD10. During the process of preparing the intermediate layer, the following steps are included: Step 1: Weigh metal element particles Ni, Co, Cr, W, Mo, Ta, Ge, Re, Hf, La with a purity greater than 99.99 wt%, clean the surface with dilute sulfuric acid solution, and place them in an alcohol solution for ultrasonic cleaning. 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 Step 2: Melting: Load the cleaned proportioned raw materials into an intermediate frequency induction melting furnace, start the mechanical pump and roots pump in sequence to create a vacuum environment, then fill it with high-purity argon as the protective atmosphere in sequence to maintain dynamic pressure balance, activate the intermediate frequency power supply for gradient heating, and use electromagnetic stirring combined with flux covering technology to implement slag removal and refining during the heating process to eliminate non-metallic inclusions and complete the alloying melting process. The above process is repeated three times, poured into a mold, and cooled to obtain alloy bars with consistent specifications. The melting temperature is 1300 °C. Step 3: Strip casting: Enclose the alloy bar in a high-purity quartz tube, vertically fix it at the center of the induction coil of a single-roll strip casting machine, interlock and start the vacuum system, then fill it with high-purity argon for protection. Inductively heat it with medium frequency to 150 °C above the liquidus of the alloy, and spray the melt onto the surface of a rapidly rotating copper roll under pressure. Rapid solidification forms an amorphous foil intermediate layer with a thickness of 80 μm. The remaining steps are the same as those in Example 1.

[0032] ​The mechanical properties of the welded joints in this embodiment were tested using an INSTRON 3382 electronic universal material testing machine, and the shear strength of the joints could reach 847 MPa.

[0033] Comparative Example 1 In this comparative example, NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 was used as the interlayer to achieve transient liquid-phase diffusion bonding of nickel-based single-crystal superalloy DD10. The specific steps are as follows: Steps 1 and 2 are the same as those in Example 1; Step 3: Place the "base material-interlayer-base material" structure in Step 2 into a vacuum diffusion welding furnace without a magnetic field generator for transient liquid-phase diffusion welding; during the heating process, in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 500 °C at a rate of 10 °C / min, and held at 500 °C for 10 min. It should be noted that a magnetic field is applied while the temperature rises to 300 °C. In the second stage, it is heated to 900 °C at a rate of 10 °C / min and held at 900 °C for 10 min. In the third stage, it is heated to the welding temperature of 1300 °C at a rate of 10 °C / min. In the fourth stage, it is held at the welding temperature of 1300 °C for 4 h, and a pressure of 5 MPa is applied for heat preservation and pressure holding; when the heat preservation and pressure holding are completed, the pressure is unloaded, and the welded part is cooled to room temperature with the furnace, and the welding is completed. The vacuum degree during the whole welding process is always not higher than , and a welded part of DD10 single-crystal superalloy is obtained, and its joint microstructure is as Figure 3 shown.

[0034] The mechanical properties of the welded joints in this comparative example were tested using an INSTRON 3382 electronic universal material testing machine, and the shear strength of the joints could reach 798 MPa.

[0035] Comparative Example 2 In this comparative example, BNi-2 foil tape was used as the interlayer to achieve transient liquid-phase diffusion bonding of nickel-based single-crystal superalloy DD10. The specific steps are as follows: Step 1 is the same as that in Example 1; Step 2: Clamp the BNi-2 foil tape interlayer and the DD10 single-crystal superalloy base material in a "base material-interlayer-base material" sandwich structure; Step 3: Place the "base material - interlayer - base material" structure in Step 2 into a vacuum diffusion welding furnace without a magnetic field generator for transient liquid-phase diffusion welding; during the heating process, in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 500 °C at a rate of 10 °C / min, and held at 500 °C for 10 min. In the second stage, it is heated to 900 °C at a rate of 10 °C / min and held at 900 °C for 10 min. In the third stage, it is heated to the welding temperature of 1200 °C at a rate of 10 °C / min. In the fourth stage, it is held at the welding temperature of 1200 °C for 4 h, a pressure of 5 MPa is applied, and heat and pressure are maintained. When the heat and pressure maintenance ends, the pressure is unloaded, and the welded part is cooled to room temperature with the furnace, and the welding is completed. The vacuum degree during the entire welding process is always not higher than , obtaining a welded part of DD10 single-crystal superalloy, and the microstructure of its joint is as Figure 4 shown.

[0036] The mechanical properties of the welded joint of this comparative example were detected using an INSTRON3382 type electronic universal material testing machine, and the shear strength of the joint can reach 694 MPa.

[0037] Combined with Figure 2 , Figure 3 , Figure 4 it can be obtained that the microstructure of the joint of the transient liquid-phase diffusion welding of nickel-based single-crystal superalloy DD10 based on electromagnetic field assistance and interlayer design in Example 1 is as Figure 2 shown, indicating that even at a lower temperature, there is no white hard and brittle phase in the welded joint, that is, the joint is all isothermal solidification, and at the same time, the welding time required is reduced and the efficiency is improved. The mechanical properties of the welded joint of Example 1 were detected using an INSTRON3382 type electronic universal material testing machine, and the shear strength of the joint of Example 1 can reach 857 MPa; Comparative Example 1 is the transient liquid-phase diffusion connection of nickel-based single-crystal superalloy DD10 based on interlayer design. Even by increasing the corresponding welding temperature and holding time, it can only reproduce the synergistic effect of electromagnetic field assistance and interlayer design to a certain extent. The microstructure of the obtained joint is as Figure 3 shown. It can be seen that without magnetic field assistance, by increasing the welding temperature and holding time, a small amount of white hard and brittle phase appears in the joint, that is, a non-isothermal solidification region appears, and at this time, the mechanical properties of the joint are reduced to 798 MPa; in Comparative Example 2, commercially available BNi-2 was used to perform transient liquid-phase diffusion connection on nickel-based single-crystal superalloy DD10 at 1200 °C, and the microstructure of its joint is as Figure 4 shown. It can be clearly seen from Figure 4 that when using a traditional interlayer for transient liquid-phase diffusion welding, even if the temperature is appropriately increased, the brittle phase in the joint cannot be completely eliminated, that is, there is always a non-isothermal solidification region, which is prone to induce the initiation of cracks, and at this time, the joint performance is low, only 694 MPa.

[0038] The above content is only an example and illustration of the structure of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar ways to replace them. As long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they shall fall within the protection scope of the present invention.

[0039] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0040] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to only the specific implementation manners. Obviously, according to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art of this technology can understand and utilize the present invention well. The present invention is only limited by the claim book and its full scope and equivalents.

Claims

1. A connection method for DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance, characterized in that, It includes the following steps: Step 1: Prepare the intermediate layer; the atomic ratio of elements in the intermediate layer is NiCo 22 Cr 20 W 10 Mo7Ta5Ge5Re2Hf 0.8 La 0.2 ; Step 2: Embedding a magnetic field generator into the inner wall of the vacuum diffusion welding furnace; Step 3: Transient liquid phase diffusion welding: Place the intermediate layer obtained in Step 1 between the upper and lower DD10 single crystal superalloy base materials, and conduct transient liquid phase diffusion welding in the vacuum diffusion welding furnace of Step 2. During the welding process, apply an alternating magnetic field along the direction perpendicular to the welding surface, and heat and apply the magnetic field synchronously. Finally, a welded part of DD10 single crystal superalloy is obtained.

2. The method for connecting DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 1, characterized in that, The process of preparing the intermediate layer in Step 1 is as follows: Weigh metal element particles Ni, Co, Cr, W, Mo, Ta, Ge, Re, Hf, and La with a purity greater than 99.99 wt% according to the atomic ratio of the elements. After cleaning, put them into a melting furnace and melt to obtain an alloy bar. Then, use the alloy melt spinning technology in a single-roll spinning machine to prepare an amorphous foil intermediate layer.

3. A method for connecting DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 2, wherein, The thickness of the amorphous foil intermediate layer is 50μm - 80μm.

4. A method for joining DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 2, wherein The temperature of the melting is 1300°C.

5. A method for connecting DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 2, characterized in that, The process of preparing the amorphous foil intermediate layer by using the alloy melt spinning technology is as follows: Enclose the alloy bar in a quartz tube, vertically fix it at the center of the induction coil of the single-roll spinning machine, and under the protection of a vacuum and argon atmosphere, heat it to 150°C above the liquidus of the alloy bar, and spray the melt onto the surface of the copper roll under pressure to solidify and form an amorphous foil intermediate layer.

6. A method for joining DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 1, characterized in that, The intensity of the magnetic field applied in Step 3 is 0.1T - 0.5T, and the magnetic field intensity gradient increases, with an alternating frequency of 30HZ.

7. A method for connecting DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 1, characterized in that, The heating process in Step 3 adopts a segmented heating method. In the first stage, the vacuum diffusion welding furnace is heated from room temperature to 500°C at a rate of 10°C / min, and held at 500°C for 10 minutes. The magnetic field is applied while the temperature rises to 300°C. In the second stage, it is heated to 900°C at a rate of 10°C / min and held at 900°C for 10 minutes. In the third stage, it is heated to the welding temperature of 1175°C at a rate of 10°C / min. In the fourth stage, it is held at the welding temperature of 1175°C for 1 hour, and a pressure of 5MPa is applied for heat preservation and pressure holding.

8. A method for connecting DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 7, characterized in that, During the transient liquid phase diffusion welding process, when the heat preservation and pressure holding end, first unload the pressure, and the welded part cools with the furnace. When the temperature of the vacuum diffusion welding furnace drops to 300°C, turn off the magnetic field generator. When the temperature of the vacuum diffusion welding furnace drops to room temperature, the welding is completed.

9. A method for connecting DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 1, characterized in that, Before the transient liquid phase diffusion welding in Step 3, the DD10 single crystal superalloy is polished successively with 400#, 600#, 1000#, 1500#, and 2000# sandpapers. After polishing, it is mechanically polished with a polishing solution and ultrasonically cleaned in anhydrous ethanol.

10. A method for connecting DD10 single crystal superalloy based on an intermediate layer and magnetic field assistance according to claim 1, characterized in that, The vacuum degree of the vacuum diffusion welding furnace described in Step 3 .

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