Ti2AlNb / GH536 dissimilar material interface fusion welding method

Abstract

The application discloses a Ti2AlNb / GH536 dissimilar material interface melting welding method and belongs to the dissimilar alloy welding field. The application aims at solving the problems of the brittle phase and the stress concentration caused by the too large difference of the thermal expansion coefficients of the dissimilar metals during the welding process. The application adopts the gradient nanocrystalline intermediate layer Ni / Nb and the Ag and SPS technology to perform diffusion welding on the GH536 alloy and the Ti2AlNb alloy, utilizes the gradient intermediate layer to relieve the difference of the thermal expansion coefficients of the two base materials and reduces the generation of the brittle phase during the welding process. Since the joint stress is relieved, the mechanical properties of the joint are ensured to be close to the base material. In addition, the nanocrystalline can promote the element diffusion by increasing the grain boundary quantity, reduces the welding temperature, and thus realizes the reliable welding of the joint with low temperature, small deformation and high strength.

Description

Technical Field

[0001] This invention belongs to the field of dissimilar alloy welding, specifically, it relates to a method for interfacial melting welding of Ti2AlNb / GH536 dissimilar materials. Background Technology

[0002] GH536 is a Ni-Cr-Fe based solid solution strengthened superalloy, with Mo, W, and Co as the main solid solution strengthening elements. It exhibits good corrosion resistance, oxidation resistance, strength, cold and hot working properties, and weldability at high temperatures. Compared to Ti-Al based lightweight intermetallic compounds, Ti2AlNb alloys, based on ordered orthorhombic phase (O), simultaneously possess better room temperature ductility, fracture toughness, and crack propagation resistance. Therefore, using Ti2AlNb alloys to replace some nickel-based superalloys in the manufacture of hot-end components for aero-engines can significantly improve the component's temperature resistance, effectively reduce component weight, and improve thrust-to-weight ratio, which is crucial for improving aero-engine performance. However, research on the joining of GH536 and Ti2AlNb is limited, and problems such as high joining temperatures, uncontrollable interfacial brittle compounds, and poor joint performance are commonly encountered.

[0003] SPS (Spark Plasma Sintering) diffusion welding is a highly efficient welding method that rapidly heats the interfaces to be joined and achieves interfacial metallurgical bonding under certain pressure and time. It offers advantages such as fast heating rate, low joining temperature, short joining time, and low energy consumption. Furthermore, the electromigration effect during SPS diffusion welding accelerates atomic diffusion efficiency, further improving joint performance. Traditional diffusion welding has a slow heating rate and requires prolonged holding at high temperature and pressure to ensure sufficient element diffusion, leading to grain growth and the formation of brittle intermetallic compounds in the base material, thus reducing its properties. Summary of the Invention

[0004] The purpose of this invention is to provide a method for interfacial melting welding of dissimilar materials Ti2AlNb / GH536. This method can achieve high-quality joining of dissimilar high-temperature alloys under low temperature and small deformation conditions, effectively avoiding the problems of brittle phase formation and stress concentration caused by excessive differences in the thermal expansion coefficients of dissimilar metals during welding.

[0005] This invention primarily addresses the problem of low joint strength in diffusion bonding of dissimilar alloys (such as GH536 alloy and Ti2AlNb alloy) due to the aggregation of brittle phases caused by the mutual diffusion of elements like Ti and Ni in the diffusion region. Simultaneously, it solves the problems of deformation and grain growth that easily occur in traditional hot-press diffusion welding processes due to excessively high welding temperatures and prolonged holding times, achieving low-temperature, low-deformation, rapid, and high-quality bonding of dissimilar materials.

[0006] This invention uses Ni and Nb as intermediate layer elements for auxiliary bonding, which can suppress the diffusion of harmful elements (Ti, Ni, Cr, etc.). Ni and Nb are both high melting point metals with small differences in their crystal structures, which can better match the two parent materials.

[0007] This invention employs a gradient nanocrystalline Ni / Nb interlayer and SPS technology for diffusion welding of GH536 alloy and Ti2AlNb alloy. During the welding process, the gradient interlayer mitigates the difference in thermal expansion coefficients between the two base materials and reduces the formation of brittle phases. Because the joint stress is relieved, the mechanical properties of the joint are ensured to converge with those of the base materials. Furthermore, the nanocrystals, by increasing the number of grain boundaries, promote element diffusion and lower the welding temperature, thereby achieving a reliable weld with low temperature, small deformation, and high strength.

[0008] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0009] The purpose of this invention is to provide a method for interfacial melting and welding of dissimilar materials Ti2AlNb / GH536, comprising the following steps:

[0010] Step 1: Grind the GH536 alloy and Ti2AlNb alloy parts to be welded separately until the surface is bright and free of scratches, and then clean or wipe with organic solvent.

[0011] Step 2: Using a magnetron sputtering device, nanoscale Ni is deposited on the surface of GH536 alloy and nanoscale Nb is deposited on the surface of Ti2AlNb alloy. During the deposition process, when the grain size grows to close to 20nm, the process is switched to 180W to bombard the surface.

[0012] Step 3: Introduce nanoscale Ag between Ni and Nb nanocrystalline layers respectively to obtain intermediate layers on GH536 alloy and Ti2AlNb alloy;

[0013] Step 4: Butt-weld GH536 alloy and Ti2AlNb alloy with the intermediate layer located between the two parts to be welded, and perform multi-stage composite pulse process welding.

[0014] To further specify, in step 1, sandpaper of grits 80, 240, 400, 1000, 2000, and 3000 is used in sequence for polishing.

[0015] Further specifying, in step 1, cleaning or wiping is performed using the organic solvent acetone or anhydrous ethanol.

[0016] Further specifying step 2, the process involves introducing nanoscale Ni and Nb using magnetron sputtering, depositing Ni on the GH536 alloy, and depositing Nb on the Ti2AlNb alloy surface, as follows:

[0017] Step 1: Turn on the main power supply of the equipment and turn on the water cooling equipment;

[0018] Step 2: Turn on the control cabinet switch and start the control panel;

[0019] Step 3: Open the vent valve, attach the treated sample to the sample stage with high-temperature adhesive, and close the vacuum chamber;

[0020] Step 4: Turn on the mechanical pump, open the bypass valve to its maximum value, turn on the vacuum gauge, and when the vacuum gauge reaches 30, close the bypass valve.

[0021] Step 5: Open the molecular pump pre-vacuum valve and turn on the molecular pump. After the frequency reaches 820Hz, open the electric gate valve to evacuate to a high vacuum.

[0022] Step 6: Wait for the vacuum level in the vacuum chamber to reach 5×10⁻⁶. -4 When Pa, open the gas cylinder valve, set the flow meter reading, start the flow meter, open the Ar gas shut-off valve and the vacuum chamber inlet valve, open the diaphragm meter in sequence, switch to automatic mode, and set the vacuum level.

[0023] Step 7: Press the pressure control button. After the pressure stabilizes, select the appropriate sample stage speed (20rpm-30rpm), open the baffle of the corresponding target position, turn on the RF sputtering power switch, set the sputtering power to 120W, and deposit for 2 hours. Once the surface has a dense and smooth columnar crystal structure and the grain size reaches about 20nm, switch the sputtering power to 180W and deposit for another hour.

[0024] To further define the method for introducing nano-Ag, the following steps are taken: After coating the GH536 and Ti2AlNb surfaces, switch to a direct-frequency sputtering power supply, turn on the switch, set the sputtering power to 120W, and deposit for 20 minutes to prepare a nano-Ag film.

[0025] Based on the original method, multilayer nanocomposite interlayers can also be prepared. By introducing nanoscale Ag into the existing nanocomposite Ni / Nb interlayer, its high diffusion coefficient and low melting point (below 600℃) enable diffusion to be activated at lower temperatures, promoting rapid fusion of interface atoms.

[0026] Further defining the process, the multi-stage composite pulse process consists of a preheating and activation stage, a connection stage, and a thermal field-assisted stabilization stage; the specific steps are as follows:

[0027] Step 1, Preheating stage: The temperature is increased from room temperature to 600°C at a rate of 160°C / min to 200°C / min. A medium-low intensity pulsed current (1 kHz and 50% duty cycle) and a low axial pressure (15 MPa) are used to achieve close physical contact between the surfaces to be joined. The Joule heating effect of the pulsed current is used to clean the interface and enhance atomic activity, preparing for the subsequent diffusion reaction.

[0028] Step 2: During the first 10 minutes of the heat preservation process, apply a high energy density (1.1 kW / cm²) solution. 2 A high duty cycle pulsed current (500 Hz and 70% duty cycle) and an external pressure of 20 MPa are applied to suppress the thermal effect of nanocrystals while providing sufficient energy for the interdiffusion of interfacial reactions, so as to achieve a strong, diffusion-dominant metallurgical bond.

[0029] Step 3: 20 minutes after the start of heat preservation, during the second half of the heat preservation process, the pulse current mode is adjusted to a medium-low intensity alternating pulse current (2kHz and 30% duty cycle) diffusion connection, supplemented by precise temperature field control and continuous pressure (20MPa) to optimize the interface structure and ensure the uniformity of temperature and structure.

[0030] To further specify, direct current is used to replace pulse current.

[0031] The synergistic effect of pulsed electric field and nano-sized interlayer. In the SPS process, pulsed current not only provides rapid and uniform heating but also induces electromigration, i.e., the directional migration of metal ions along grain boundaries or bulk diffusion paths under the influence of the electric field, significantly increasing the atomic diffusion rate. Furthermore, the nano-sized Ni / Nb interlayer, due to its extremely small grain size and high volume fraction of grain boundaries, acts as a rapid channel for atomic diffusion, further accelerating the interdiffusion of elements such as Ni, Nb, and Ti, shortening the residence time of elements in the interface region, and reducing the formation of brittle intermetallic compounds.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) It has better technical effects compared with existing fusion welding or brazing techniques, such as more complete hole closure and better relief of residual stress;

[0034] (2) The surface nano-sizing method using magnetron sputtering has the following advantages: controllable and stable composition, uniform thickness; high deposition rate and low temperature rise; high film density and strong adhesion.

[0035] (3) The invention adopts nano-assisted pulse current technology to reduce welding temperature and improve the problems of metallurgical incompatibility and large difference in thermal expansion coefficient of dissimilar materials. It conforms to the current technological development trend.

[0036] 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

[0037] Figure 1 This is a schematic diagram of the joint structure obtained at 600℃ / 20MPa / 30min. Detailed Implementation

[0038] 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.

[0039] Example 1: The method for achieving high-quality dissimilar Ti2AlNb alloy and GH536 alloy joints at a lower temperature in this example is achieved through the following steps:

[0040] Step 1: Grind the surfaces of the Ti2AlNb alloy and GH536 alloy to be welded respectively: Grind the surfaces to be welded in sequence with 80 grit, 240 grit, 400 grit, 1000 grit, 2000 grit and 3000 grit sandpaper, and then place them in acetone for ultrasonic cleaning for 5 minutes.

[0041] Step 2: Coat the Ti2AlNb alloy and GH536 alloy to be soldered with Nb and Ni nanocrystals respectively. Use a magnetron sputtering device to first evacuate to a vacuum of 5×10⁻⁶. -4 Pa, and then under Ar gas protection, Nb and Ni were deposited on Ti2AlNb alloy and GH536 alloy for 3 hours respectively using DC sputtering target and RF sputtering target. After the deposition, the samples were taken out and immediately placed in the graphite mold in the order of GH536 on top and Ti2AlNb on the bottom.

[0042] The specific steps are as follows:

[0043] Step 1) Turn on the main power supply to the equipment and turn on the water cooling system;

[0044] Step 2) Turn on the control cabinet switch and start the control panel;

[0045] Step 3) Open the vent valve, attach the treated sample to the sample stage with high-temperature adhesive, and close the vacuum chamber;

[0046] Step 4) Turn on the mechanical pump, open the bypass valve to its maximum value, turn on the vacuum gauge, and when the vacuum gauge reaches 30, close the bypass valve;

[0047] Step 5) Open the molecular pump pre-vacuum valve and turn on the molecular pump. After the frequency reaches 820Hz, open the electric gate valve to evacuate to a high vacuum.

[0048] Step 6) Wait for the vacuum level in the vacuum chamber to reach 5×10 -4 When Pa, open the gas cylinder valve, set the flow meter reading, start the flow meter, open the Ar gas shut-off valve and the vacuum chamber inlet valve, open the diaphragm meter in sequence, switch to automatic mode, and set the vacuum level.

[0049] Step 7) Press the pressure control button, and after the pressure stabilizes, select the appropriate rotation speed (20-30 rpm), open the baffle of the corresponding target position, turn on the RF sputtering power switch, set the sputtering power to 120W, and deposit for 2 hours. Then switch the sputtering power to 180W and deposit for another 1 hour.

[0050] Step 8) Introduce nanoscale Ag into the Ni and Nb nanocrystalline layers respectively, i.e., obtain intermediate layers on the surfaces of GH536 alloy and Ti2AlNb alloy. The specific magnetron sputtering steps are as follows: At a vacuum level of 5 × 10⁻⁶... -4 Radio frequency sputtering under Pa and Ar gas protection, sputtering power of 120W, deposition time of 20 minutes.

[0051] Step 3: Place the graphite mold containing the sample into the vacuum diffusion welding furnace. The pressure system inside the furnace applies vertical pressure to the assembly, causing the surfaces to be welded to adhere.

[0052] Step 4: Then, evacuate to a high vacuum of 2E-2Pa and run the diffusion bonding process. The specific process is as follows:

[0053] The pulsed current in-situ heating system was first operated, with the sample temperature rising at a rate of 100℃ / min, until it reached 600℃. The pulsed current in-situ heating system maintained the sample temperature for 30 minutes, during which the pressure was 20MPa. The pulsed current frequency was 20kHz, and the pulsed current and radiant heating power were controlled by a multi-heat source temperature control system to ensure that the sample temperature conformed to the process curve.

[0054] Step 5: After the heat preservation is completed, the pressure system stops running, and the pulse current in-situ heating system stops running.

[0055] Compared to traditional hot-press diffusion welding methods, the above method can prepare materials such as... under parameters of 600℃-20MPa-30min. Figure 1 The tissue exhibits excellent performance with very few joints in the brittle phase distribution.

[0056] 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 of dissimilar materials Ti2AlNb / GH536, characterized in that, Includes the following steps: Step 1: Grind the GH536 alloy and Ti2AlNb alloy parts to be welded separately until the surface is bright and free of scratches, and then clean or wipe with organic solvent. Step 2: Using a magnetron sputtering device, nanoscale Ni is deposited on the surface of GH536 alloy and nanoscale Nb is deposited on the surface of Ti2AlNb alloy using physical vapor deposition technology. During the deposition process, when the grain size grows to 20nm, the sputtering power is switched to 180W to bombard the surface. Step 3: Introduce nanoscale Ag between Ni and Nb nanocrystalline layers respectively to obtain gradient intermediate layers in GH536 alloy and Ti2AlNb alloy. Step 4: Butt-weld GH536 alloy and Ti2AlNb alloy with the intermediate layer located between the two parts to be welded, and perform multi-stage composite pulse welding process; The multi-stage composite pulse process consists of a preheating and activation stage, a connection stage, and a thermal field-assisted stabilization stage. During the preheating and activation stage, diffusion connection is performed using a pulsed current with a frequency of 1kHz and a duty cycle of 30%-50%, with an axial pressure of 15MPa and a temperature range from room temperature to 600℃. The connection stage involves applying a high energy density of 1.1 kW / cm³ during the first 10 minutes of holding at 600°C. 2 An external pressure of 20MPa is applied, and a pulse current with a frequency of 500Hz and a duty cycle of 70% is used for diffusion connection; The thermal field-assisted stabilization phase is achieved during the last 20 minutes of heat preservation, by applying 0.2 kW / cm² heat. 2 、 2kHz pulsed current with 30% duty cycle, diffusion connection at 20MPa pressure.

2. The method according to claim 1, characterized in that, Use sandpaper of grits 80, 240, 400, 1000, 2000 and 3000 in sequence to polish.

3. The method according to claim 1, characterized in that, The organic solvent is acetone or anhydrous ethanol.

4. The method according to claim 1, characterized in that, In step 2, the magnetron sputtering process is as follows: When the vacuum level reaches 5 × 10⁻⁶... -4 Radio frequency sputtering under Pa and Ar gas protection, sputtering power of 120W, plating for 2 hours, then switching sputtering power to 180W, and plating for another 1 hour.

5. The method according to claim 1, characterized in that, The steps for introducing nanoscale Ag are as follows: At a vacuum level of 5 × 10⁻⁶ -4 Radio frequency sputtering under Pa and Ar gas protection, sputtering power of 120W, deposition time of 20 minutes.

6. The method according to claim 1, characterized in that, The pulse current is replaced with direct current.

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