Interface fusion welding method and device

Abstract

The invention discloses an interface fusion welding method and equipment, and belongs to the technical field of diffusion welding. The problem that in the metal diffusion welding process, in order to form tight interface contact, external pressure is excessively relied on, and consequently the deformation amount of base metal is large is solved. And meanwhile, the problem that the temperature of a welding interface is not uniform in traditional welding is solved. The method comprises the following steps: polishing the high-temperature alloy until no obvious scratch exists on the surface, sequentially carrying out ultrasonic cleaning with acetone and absolute ethyl alcohol, and drying; fixing the sample on a sample table of a magnetron sputtering device, vacuumizing, introducing inert gas, carrying out magnetron sputtering on nickel and aluminum at the same time, and then carrying out magnetron sputtering on silver; then, placing in absolute ethyl alcohol for ultrasonic cleaning, placing in a NaOH solution, heating in a water bath for immersion cleaning, and washing with deionized water; then, putting into an HCl solution, carrying out immersion cleaning, washing with deionized water, carrying out ultrasonic cleaning with absolute ethyl alcohol, and drying; and then laminating the plated surface, and performing magnetic field-assisted induction heating diffusion welding. Small-deformation and high-quality diffusion welding of metal at a relatively low temperature is achieved.

Description

Technical Field

[0001] This invention belongs to the field of diffusion welding, specifically, it relates to an interface melting welding method and equipment. Background Technology

[0002] Diffusion welding, a solid-state joining technology, works by applying pressure and holding the workpiece at a temperature below the melting point of the base material for a specified duration. This pressure forces the interfaces to come into close contact through microscopic plastic deformation, atomic diffusion, and creep mechanisms, ultimately eliminating the interface and forming a metallurgically bonded integral joint. The entire process does not require melting the base material; instead, under thermodynamic driving forces, atoms at the interface are activated by prolonged high temperatures, migrating across boundaries to achieve grain growth and cross-boundary bonding. However, traditional diffusion welding processes require temperatures between 0.7 and 0.8 °C to achieve reliable atomic diffusion and interface bonding. m The process is carried out under high temperatures and pressures exceeding 30 MPa. Such process conditions present two fundamental contradictions: first, the high pressure conditions easily lead to plastic deformation of thin-walled components, crushing the internal precision channels; second, the high-temperature environment causes recrystallization and grain coarsening of the base material, impairing the high-temperature mechanical properties of the material.

[0003] SPS diffusion welding is an advanced solid-state bonding method developed from Spark Plasma Sintering (SPS). Its core lies in utilizing a pulsed high current applied to the workpiece and mold to generate two key effects: first, a concentrated Joule heating effect rapidly heats the interface region to the welding temperature; second, the accompanying plasma activation, electroplasticity, and electromigration field effects effectively break down the interface oxide film, significantly enhance atomic diffusion capabilities, and reduce deformation resistance. Compared to conventional diffusion welding, SPS diffusion welding offers advantages such as a faster heating rate and a more concentrated temperature in the welding area.

[0004] Nanocrystalline materials possess extremely high grain boundary density due to their ultra-fine grain size. These grain boundaries act as channels for rapid atomic diffusion, significantly enhancing the material's diffusion coefficient to a level far exceeding that of traditional coarse-grained materials. Simultaneously, the abundant grain boundary structure also implies a high level of excess free energy stored within the system, placing it in a metastable state. These properties give nanocrystalline materials significant advantages in diffusion welding: their exceptionally high diffusion capacity can drastically reduce the required joining temperature or shorten the holding time, thereby suppressing thermal damage caused by diffusion welding; while the higher interfacial energy of nanocrystalline materials acts as an additional driving force, promoting the migration of interfacial atoms and the closure of pores, reducing the demand for welding temperature and pressure, and potentially enabling low-temperature, low-pressure, high-efficiency, and high-quality joining. Summary of the Invention

[0005] Magnetron sputtering is a physical vapor deposition technique that utilizes magnetic field confinement to improve sputtering efficiency. Its principle involves ionizing argon gas using an electric field to generate plasma. Under the confinement of the magnetic field, the electron path is lengthened, significantly increasing gas ionization efficiency. This allows argon ions to bombard the target material more efficiently, sputtering out atoms or molecules that are deposited onto the substrate to form a thin film. The main characteristics of this process are high deposition rate, uniform and dense film, and strong adhesion. Its core advantages lie in its ability to efficiently prepare high-quality thin films, its strong process controllability, and its applicability to various materials such as metals, alloys, semiconductors, and ceramics. Furthermore, magnetron sputtering can also prepare coatings with nanoscale grains.

[0006] Induction heating is a method of heating an electrical conductor (usually a metal) using electromagnetic induction. Eddy currents are generated within the metal, heating it due to its resistance. Heat is generated in two ways. First, the inherent resistance of the material impedes the flow of these eddy currents, resulting in intense localized heating (the Joule effect). Second, if the material is magnetic (such as iron), the rapid reversal of its magnetic domains generates additional frictional heat through hysteresis. When an alternating current flows through the conductor, an induced electromotive force (EMF) is generated within the conductor under the influence of the resulting alternating magnetic field. Since the induced EMF is greater closer to the core, the current in the conductor tends to flow towards the surface, with the current intensity decreasing exponentially from the surface to the core.

[0007] Therefore, this invention utilizes a pulsed current diffusion welding device for welding, while simultaneously employing an induction heating device to increase the temperature of the outer surface of the metal. Prior to welding, a magnetron sputtering device is used to coat the metal surface.

[0008] This invention primarily addresses the problem of excessive reliance on external pressure to form a tight interface during metal diffusion welding, leading to significant deformation of the base material. It also solves the problem of uneven welding interface temperature caused by heat dissipation from the outermost part of the metal connection interface in traditional welding processes, achieving high-quality diffusion welding with minimal deformation at relatively low temperatures.

[0009] To address the aforementioned technical problems, the present invention adopts the following technical solution: This invention provides an interface melting welding method. The core technical route includes four key stages: (1) preparation of nickel-aluminum nanocomposite coating; (2) pulsed current assisted diffusion welding; (3) induction coil assisted heating; and (4) instantaneous liquid phase diffusion welding. To solve the problem of weak atomic diffusion ability on the surface of high-temperature alloys, a coating with nano-sized grains is prepared on the surface of high-temperature alloys by electroplating to improve the near-surface diffusion ability of high-temperature alloys.

[0010] Meanwhile, aluminum grains, as a precipitated phase, play a role in strengthening the coating.

[0011] During the welding process, the nano-silver coating melts, forming diffusion channels for the nickel-aluminum coatings on both sides, thus promoting the diffusion process.

[0012] Pulsed current assisted diffusion welding uses high-frequency pulsed current to rapidly heat up the workpiece to be welded.

[0013] Induction coil auxiliary heating is used to increase the surface temperature of the workpiece being welded, thereby reducing the decrease in surface temperature due to heat loss.

[0014] The purpose of this invention is to provide an interface melting welding method, characterized by comprising the following steps: Step 1: Polish the high-temperature alloy until there are no obvious scratches on the surface, then clean it ultrasonically with acetone and anhydrous ethanol in sequence, and dry it. Step 2: Then fix it onto the sample stage of the magnetron sputtering device, evacuate it and introduce inert gas, while simultaneously magnetron sputtering nickel and aluminum, and then magnetron sputtering silver. Step 3: Then, ultrasonically clean the solution in anhydrous ethanol, immerse it in NaOH solution, heat it in a water bath, and rinse it with deionized water. Step 4: Then place it in HCl solution, soak and wash, rinse with deionized water, ultrasonically clean with anhydrous ethanol, and dry. Step 5: Then, the coated surfaces are bonded together, and magnetic field-assisted induction heating is used for diffusion welding. Further specify the sanding method, using silicon carbide sandpaper of grades 80#, 240#, 800#, 1500#, and 3000# in sequence.

[0015] Further specifying, the inert gas is argon, and the vacuum level is stabilized at 3 Pa to 8 Pa.

[0016] Further, the power of the nickel target is adjusted to 300~400 W, and the power of the aluminum target is adjusted to 150~200 W.

[0017] Further limiting, the power of the silver target is adjusted to 300~400 W.

[0018] Further specified, water bath heating at 50 ℃.

[0019] Furthermore, the mass concentration of the NaOH solution is specified to be 10%~25%.

[0020] Furthermore, the HCl solution has a mass concentration of 5%.

[0021] Further specifying the diffusion welding parameters: vacuum level at 5×10 -4Below Pa, the heating temperature is set to 700 ℃, the heating rate is 100 ℃ / min, the holding time is 30 min, the welding pressure is 20 MPa, the DC pulse current duty cycle is set to 1:1, the induction heating frequency is set to 10 kHz, and the power is set to 20 kW.

[0022] The present invention also provides an interface melting welding device, which includes a quartz tube, two electrodes, two graphite pressure heads, an induction coil and an induction heating system. The induction coil is surrounded by the quartz tube and connected to the induction heating system. The graphite pressure head is disposed inside the quartz tube. The workpiece to be welded is placed between the two graphite pressure heads, and an electrode is disposed at the end of each of the two graphite pressure heads.

[0023] Another object of the present invention is to provide a method for welding high-temperature alloys using any of the above methods, wherein the high-temperature alloy is high-temperature alloy GH536.

[0024] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves high-quality bonding at low temperature and low pressure: by magnetron sputtering a nano-nickel-aluminum composite coating and a silver interlayer onto the surface of a high-temperature alloy, the diffusion ability and reactivity of interfacial atoms are significantly improved. Combined with the synergistic effect of pulsed current Joule heating and induction heating, a dense metallurgical bond can be achieved at relatively low temperature and pressure, effectively avoiding the base material deformation, grain coarsening, and internal structural damage caused by high temperature and high pressure in traditional diffusion welding.

[0025] This invention provides a technique for homogenizing welding: using an induction coil to assist in heating the outer edge of the workpiece, compensating for the interface temperature gradient caused by heat dissipation, making the temperature distribution in the entire welding area more uniform, thereby improving the homogeneity of the joint structure and reducing welding defects.

[0026] The method of this invention shortens the process cycle and improves efficiency: the combination of pulsed current rapid heating and the high diffusion coefficient of the nano-coating significantly shortens the heat preservation time required for diffusion welding, improves production efficiency, and reduces energy consumption.

[0027] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the coating. Figure 2 This is a schematic diagram of an SPS diffusion welding apparatus; Figure 3 It is the shear stress-strain curve of the welded sample; Figure 4 This is a SEM image of the welded sample joint; Figure 5 This is an image of the grain size of the weld joint. Detailed Implementation

[0029] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0030] Example 1: The interface fusion welding method in this embodiment is implemented through the following steps: (1) Use silicon carbide sandpaper of 80#, 240#, 800#, 1500# and 3000# in sequence to polish the high temperature alloy GH536 sample until there are no obvious scratches on the sample surface.

[0031] (2) Use acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes each to remove residual oil and other organic pollutants from the surface of nickel-based high-temperature alloy GH536.

[0032] (3) Place the sample in an oven to dry for 1 minute to ensure that the sample surface is clean and free of moisture.

[0033] (4) Fix the dried sample onto the sample stage of the magnetron sputtering device. Install a 99.99% nickel target on the strong magnetic target holder, a 99.99% aluminum target on the AC target holder, and a 99.99% silver target on the DC target holder. Start the magnetron sputtering device.

[0034] (5) Start the mechanical pump and molecular pump in sequence to evacuate the vacuum and reduce the vacuum level inside the magnetron sputtering device to 5×10⁻⁶. -4 Below Pa.

[0035] (6) Introduce argon gas as the sputtering gas, start the flow meter, and adjust the internal vacuum of the magnetron sputtering to stabilize at 3~8 Pa.

[0036] (7) Simultaneously start magnetron sputtering of the nickel and aluminum targets. Adjust the nickel target power to 300~400 W and the aluminum target power to 150~200 W. Sputtering time is 4 h. After sputtering is completed, turn off the nickel and aluminum targets.

[0037] (8) Start the magnetron sputtering of the silver target. Adjust the silver target power to 300~400 W and the sputtering time to 1 h. Turn off the silver target after sputtering is completed.

[0038] (9) After the magnetron sputtering coating is completed, the sample is taken out and ultrasonically cleaned in anhydrous ethanol for 15 min.

[0039] (10) Place the sputtered sample in a NaOH solution with a concentration of 10~25%, heat it in a water bath to 50 °C, immerse it for about 15 min, and then rinse the sample surface with deionized water.

[0040] (11) Place the sample treated with alkali in a 5% HCl solution and immerse it for 2 min. After that, rinse the sample surface with deionized water and ultrasonically clean it with anhydrous ethanol for 15 min. After drying, store it in alcohol.

[0041] (12) Dry the alcohol on the sample surface, attach the coating layer, and fix it in the SPS diffusion soldering equipment. Control the vacuum degree of the SPS diffusion soldering equipment at 5×10⁻⁶. -4 Below Pa, the heating temperature was set to 700 ℃, the heating rate to 100 ℃ / min, the holding time to 30 min, and the welding pressure to 20 MPa. The DC pulse current duty cycle was set to 1:1. Simultaneously, the induction heating frequency was set to 10 kHz and the power to 20 kW. During the welding process, a type K thermocouple was used to monitor the temperature at the weld joint of the sample.

[0042] (13) After welding, the welded sample is cooled with the furnace and then removed.

[0043] System composition description: Pulse power supply: Provides high-frequency pulse current to generate Joule heating effect.

[0044] Vacuum system: Maintains a high vacuum environment to prevent oxidation.

[0045] Pressure system: Provides precise axial pressure control.

[0046] Temperature measurement system: Infrared thermometer (≥800 ℃) + K-type thermocouple (<800 ℃).

[0047] Cooling system: Controllable rate cooling device.

[0048] Induction heating system: Heats the sample by generating eddy currents inside the welded sample using a high-frequency changing magnetic field.

[0049] This implementation uses welding equipment (see...) Figure 2 It includes a quartz tube, two electrodes, two graphite pressure heads, an induction coil, and an induction heating system. The induction coil is surrounded by the quartz tube and connected to the induction heating system. The graphite pressure head is set inside the quartz tube. The workpiece to be welded is placed between the two graphite pressure heads, and an electrode is set at the end of each graphite pressure head.

[0050] The shear stress-strain curve of the welded sample is as follows Figure 3As shown in the figure, the welded joint exhibits high strength and good plastic deformation capacity in the shear strength test. The shear strength of the joint can reach 446 MPa, which is much higher than that of conventional low-temperature diffusion welded joints. This indicates that the synergistic design of nickel-aluminum nano-coating reinforcement and silver interlayer diffusion promotion effectively improves the interfacial bonding strength and toughness.

[0051] SEM images of welded sample joints, such as Figure 4 As shown in the figure, there are no obvious defects such as pores or cracks at the weld interface. A dense and continuous metallurgical bond is formed between the coating and the base material, creating an interdiffusion zone with a width of approximately 1 μm. The microstructure near the interface is uniform, with no obvious oxide inclusions, indicating that the coating treatment and welding process effectively promoted the interdiffusion and bonding of interfacial atoms.

[0052] Grain size images of welded joints as shown Figure 5 As shown in the figure, the welded joint area after welding has uniform and fine grain size, belonging to submicron grains. The introduction of the nano-coating inhibits the migration and coarsening of grain boundaries during the welding process, which is beneficial to maintaining the high-temperature mechanical properties and creep resistance of the joint.

[0053] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A method for interfacial melting welding, characterized in that, Includes the following steps: Step 1: Polish the high-temperature alloy until there are no obvious scratches on the surface, then clean it ultrasonically with acetone and anhydrous ethanol in sequence, and dry it. Step 2: Then fix it onto the sample stage of the magnetron sputtering device, evacuate the vacuum and introduce inert gas, and simultaneously turn on the nickel target and aluminum target for magnetron sputtering, and then turn on the silver target for magnetron sputtering. Step 3: Then, ultrasonically clean the solution in anhydrous ethanol, immerse it in NaOH solution, heat it in a water bath, and rinse it with deionized water. Step 4: Then place it in HCl solution, soak and wash, rinse with deionized water, ultrasonically clean with anhydrous ethanol, and dry. Step 5: Then, the coated surfaces are bonded together, and magnetic field-assisted induction heating is used for diffusion welding.

2. The method according to claim 1, characterized in that, Use silicon carbide sandpaper of grades 80#, 240#, 800#, 1500#, and 3000# in sequence to polish.

3. The method according to claim 1, characterized in that, Argon is used as the inert gas to stabilize the vacuum level at 3 Pa to 8 Pa.

4. The method according to claim 1, characterized in that, The power of the nickel target is adjusted to 300~400 W, the power of the aluminum target is adjusted to 150~200 W, and the power of the silver target is adjusted to 300~400 W.

5. The method according to claim 1, characterized in that, Heated in a water bath at 50℃.

6. The method according to claim 1, characterized in that, The NaOH solution has a mass concentration of 10% to 25%.

7. The method according to claim 1, characterized in that, The HCl solution has a mass concentration of 5%.

8. The method according to claim 1, characterized in that, Diffusion welding parameters: vacuum degree at 5×10 -4 Below Pa, the heating temperature is set to 700 ℃, the heating rate is 100 ℃ / min, the holding time is 30 min, the welding pressure is 20 MPa, the DC pulse current duty cycle is set to 1:1, the induction heating frequency is set to 10 kHz, and the power is set to 20 kW.

9. The method according to claim 1, characterized in that, The high-temperature alloy is GH536.

10. An apparatus for the method according to any one of claims 1-9, characterized in that, It includes a quartz tube, two electrodes, two graphite pressure heads, an induction coil, and an induction heating system. The induction coil is surrounded by the quartz tube and connected to the induction heating system. The graphite pressure head is set inside the quartz tube. The workpiece to be welded is placed between the two graphite pressure heads, and an electrode is set at the end of each graphite pressure head.

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