Nickel-based superalloy double-radial-plate turbine disc plastic connection method

Abstract

The invention relates to a nickel-based superalloy double-radial-plate turbine disc plastic connection method which comprises the step of machining an annular boss structure and an annular groove structure which are used for being clamped in a matched mode in plastic connection on the disc edges of two blank annular half discs of a double-radial-plate turbine disc and the connecting ring face of a hub. And after the two blank annular half discs subjected to mechanical precision machining are assembled and connected through a boss and groove structure, plastic connection is conducted, so that complete microcosmic metallurgical bonding is achieved within controllable disc edge and hub macroscopic deformation, and the double-radial-plate turbine disc is obtained. And performing recrystallization annealing and stress relief annealing on the double-radial-plate turbine disc in sequence. Compared with a plane connector, the metallurgical bonding area achieved by the boss and groove type connector is remarkably increased, and the plastic connection rate is improved.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing aeroengine turbine disks. Background Art

[0002] The double-web turbine disk is composed of two symmetric half-disk parts connected together, and its overall structure is a hollow double-web structure. Compared with the traditional single-web turbine disk, the double-web turbine disk has a lighter mass and a higher rotational speed. At the same time, cold air can enter its cavity through the hub to cool the inner side of the turbine disk, thereby improving the cooling effect and reducing the cold air consumption.

[0003] Currently, the manufacturing process of the double-web turbine disk mainly includes the following steps: First, two symmetric half-disk structures are machined from forgings, then the two half-disks are connected by friction welding or diffusion welding to form a double-web turbine disk part, and finally machining and shaping are completed. During the friction welding process, due to the significant difference in the linear velocity at different positions along the radial direction of the connection surface, the heating rate at different radii of the disk part is uneven; at the same time, as the temperature rises, the interface friction mode gradually changes from sliding friction to adhesive friction, and the change in the friction mode further affects the heat generation. The resulting non-equilibrium thermal change forms a "plastic ring", which ultimately leads to significant differences in the organizational structure of different regions of the joint, affecting the welding quality and the comprehensive performance of the disk part.

[0004] In contrast, although diffusion welding can ensure uniform joint structure and no obvious deformation, long-time heat preservation not only limits the production efficiency, but also may cause coarsening of grains and precipitate phases, resulting in attenuation of the properties of the parent alloy. In addition, continuous micropore defects may appear at the diffusion connection interface, which are likely to become crack sources, posing a serious threat to the comprehensive performance of the disk part and flight safety.

[0005] In summary, the connection part of the double-web turbine disk is a key part affecting its comprehensive mechanical properties. To ensure sufficient connection strength between the two half-disks, it is urgent to optimize and improve the connection method of the double-web turbine disk. Summary of the Invention

[0006] The purpose of the present invention is to avoid the deficiencies of the prior art and provide a plastic connection method for a nickel-based superalloy double-web turbine disk, which realizes a higher level of equivalent stress concentration in a wider area of the connection surface by optimizing the geometric shape of the boss-groove joint, controlling the metal plastic flow at the joint during the plastic connection process, so as to promote the dynamic recrystallization and grain boundary migration at the interface, thereby realizing the preparation of a high-performance nickel-based superalloy double-web turbine disk.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: A plastic connection method for a nickel-based superalloy double-web turbine disk, comprising the following steps: Step 1: On the connecting ring surfaces at the disc rims and hubs of the two blank annular half-discs of the double web turbine disc, mechanically process the annular bosses and annular grooves for mating and clamping in plastic connection, so that after the boss and groove structures are fitted and connected, the thickness T of the groove is evenly distributed in the annular extension direction of the boss; Step 2: After assembling and connecting the two blank annular half-discs after mechanical precision machining using the boss and groove structures, perform plastic connection to achieve complete microstructural metallurgical bonding within the controllable macroscopic deformation at the disc rim and hub, obtaining a double web turbine disc; Step 3: Perform recrystallization annealing and stress relief annealing on the double web turbine disc in sequence, for the recrystallization of the residual deformed grains after plastic connection and to promote the cross-interface migration of grain boundary elements.

[0008] Furthermore, in the connection section of the boss and groove structures, the height H of the boss is greater than the depth W of the groove, and the size of the boss embedded in the groove is matched with the groove size for interference fit, and the interference fit code is H7 / s6, to prevent the reduction of the connection rate caused by assembly loosening; Meanwhile, the thickness T of the groove is greater than 10 mm, to prevent the problem that it is difficult to effectively provide radial compressive stress in plastic connection due to the greater outward bulging degree of the groove wall than that of the boss.

[0009] Furthermore, the steps for preparing the two blank annular half-discs are as follows: Perform solution treatment and aging treatment on the nickel-based superalloy parts for preparing the double web turbine disc in sequence, to improve the strength and toughness of the plastic connection of the superalloy; Specifically: Solution treatment: Heat-treat the nickel-based superalloy workpiece at a temperature of 1170°C to 1200°C for 2 h to 6 h, and then air-cool; Aging treatment: The nickel-based superalloy workpiece obtained by solution treatment is heat-treated at a temperature of 720°C to 730°C for 4 h to 20 h, and then air-cool; After completion, perform turning and milling composite machining on the obtained nickel-based superalloy parts, and two blank annular half-discs are obtained.

[0010] Furthermore, perform grinding and turning-milling composite precision machining on the two blank annular half-discs, so that the relative connecting ring surfaces of the two blank annular half-discs are machined to a flatness ≤ 0.05 mm and the parallelism between the relative connecting ring surfaces ≤ 0.05 mm.

[0011] Furthermore, before plastic connection, it also includes the treatment of the connecting end surfaces of the boss and groove structures, specifically: First, perform turning and milling operations to ensure that the surface roughness Ra of the effective connection surface when the boss and the groove are matched and connected is ≤ 0.4; Next, polish the effective connection surface. The connection surface in the recess is treated with a handheld grinding machine and a wool grinding head until the surface roughness Ra of the effective connection surface is ≤ 0.05. Then, perform ultrasonic cleaning, drying, and sealing for later use; After the treatment is completed, if the plastic connection cannot be completed within 24 hours, it is necessary to re-treat the effective connection surface and then perform the plastic connection.

[0012] Furthermore, the ultrasonic cleaning is carried out with an ultrasonic frequency of 80 - 120 kHz, a power density of 0.3 - 0.8 W / cm 2 , a time of 5 - 10 min, a cleaning temperature of 50 - 70 °C, and a water-based cleaning agent. Finally, dry it and seal it for storage.

[0013] Furthermore, in step two, before the plastic connection, the assembly of the two blank annular half-discs (1) is specifically to axially butt and combine the boss and groove structures along the blank annular half-discs and use a positioning pin to position them on the mold, so that the clearance between the connection surfaces of the two blank annular half-discs is ≤ 0.02 mm; At the same time, with the mold axis as the reference, the coaxiality between the mold and the two blank annular half-discs is within 0.025 mm; then, apply a relative initial pressure of 50 - 100 MPa to the two assembled blank annular half-discs to make the two blank annular half-discs in close contact.

[0014] Furthermore, the plastic connection of the two assembled blank annular half-discs by assembly connection is specifically as follows: Under the condition of evacuating to a vacuum degree in the furnace above 10 -3 Pa, with a strain rate of 0.01 - 1 s -1 , a heating rate of 1 - 10 °C / s, after the workpiece reaches a temperature of 1100 °C - 1200 °C, hold for 3 - 5 min, and perform plastic connection with a deformation amount of 30% - 50%; The process parameters of the plastic connection are used to ensure the expected connection effect during the plastic connection process. The increase in temperature and the decrease in strain rate during the plastic connection are both beneficial to grain recrystallization at the connection interface, but too high a temperature will cause the strengthening phase to dissolve back, leading to tissue coarsening and damaging the performance of the alloy workpiece; when the strain rate is too low, the newly nucleated grains at the connection interface have sufficient time to significantly coarsen through the grain growth mechanism, resulting in out-of-control grain size and severely reducing the mechanical properties at the joint; The greater the deformation amount, the better the connection effect. Under the same other conditions, the greater the deformation amount, the longer the duration of the plastic connection process, the more sufficient the interfacial atomic diffusion. At the same time, a large deformation amount can provide sufficient distortion energy to ensure multiple rounds of recrystallization of the interfacial grains, which is beneficial to improving the connection effect. However, after the deformation amount exceeds the limited range, the boss and groove structures are significantly upset, and the metal flow situation will become more complex. If the metal flows on both sides of the interface cannot be synchronized, the atomic diffusion and microstructure evolution of the joint cannot cross the interface, which has no effect on plastic connection. After completing the plastic connection, the two blank ring half-discs are taken out and air-cooled to room temperature. This is used to prevent the two blank ring half-discs from deforming and cracking, and during the air-cooling process, a slower cooling rate helps to control the grain growth of the workpiece and better achieve microstructural metallurgical bonding.

[0015] Further, in the plastic connection described above, first, the two blank ring half-discs assembled and connected through the boss and groove structures are put into the furnace and placed at the center of the furnace platform of the plastic connection equipment. Graphite limit blocks are placed on both sides of the two blank ring half-discs, and the height of the graphite limit blocks is 0.15±0.05 mm lower than the height of the two blank ring half-discs assembled and connected.

[0016] Further, the specific content of step three is as follows: The recrystallization annealing is a heat treatment carried out at a temperature of 1050 - 1080 °C for 30 - 60 min and then cooled in the furnace. The stress relief annealing is a heat treatment carried out at a temperature of 600 - 900 °C for 1 - 4 h and then cooled in the furnace.

[0017] The beneficial effects of the present invention are as follows: By optimizing the joint design, the boss part of the web plate contacts the groove wall first, and the constraint effect generated by the groove wall promotes the formation and welding of the interfacial grain boundaries. Under the optimal parameters, the chamfer of the groove wall is the starting connection area of the interfacial grain boundaries. Local plastic deformation is the key factor for the formation of interfacial grain boundaries. Usually, it is difficult to determine the formation area of the interfacial grain boundaries on the connection surface during plastic connection, but the joint with a groove shape produces more obvious local plastic deformation, enabling the interfacial grain boundaries to surely form at the groove chamfer, enhancing the stability of the plastic connection process. On the other hand, the large area of interfacial grain boundaries increases the chance of the grain boundaries of the surface layer grains crossing the interfacial grain boundaries, theoretically increasing the effective connection area.

[0018] 2. Simulate the plastic connection process through finite element software (such as Figure 5 and Figure 6As shown, the results indicate that optimizing the shape of the plastic connection joint can effectively regulate the metal plastic flow in the joint area and achieve a higher level of equivalent stress concentration within a larger range of connection surfaces. Such optimization not only promotes dynamic recrystallization and grain boundary migration but also significantly improves the connection quality of the double-web turbine disk.

[0019] 3. After plastic connection of the optimized joint, an interface grain boundary is formed at the boss chamfer and quickly heals. A large number of fine grains appear at the original weld position, and almost the entire tabletop is completely welded. Compared with the flat joint, the metallurgical bonding area achieved by the boss-groove joint is significantly increased, and the plastic connection rate is improved.

[0020] Based on diffusion connection, the present invention increases the connection pressure in plastic connection, causing slight plastic deformation in the joint, that is, optimizing the shape of the connection joint, significantly reducing the connection time and effectively eliminating defects such as continuous microvoids, thereby fully improving the interface connection strength, achieving high-quality connection of nickel-based superalloy double-web turbine disks. Its process is stable and controllable, with very broad engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the left and right web structures of the present invention; Figure 2 is a schematic diagram of the boss and groove structures of the present invention; Figure 3 is a schematic diagram of plastic connection of the boss and groove structures of the present invention; Among them, (a) plastic connection of the disk edge part; (b) plastic connection of the hub part; Figure 4 is a schematic diagram of the plastic connection effect of the double-web turbine disk of the present invention; Figure 5 is a schematic diagram of the stress distribution of the flat joint in the prior art; Figure 6 is a schematic diagram of the stress distribution of plastic connection of the boss and groove structures of the present invention; Figure 7 is a plastic connection effect diagram of the flat joint in the prior art; Figure 8 is a plastic connection effect diagram of the boss and groove structures of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0023] To achieve the above object, the present invention provides the following specific embodiments: Example 1: As Figure 1 , Figure 2 ,Figure 3 As shown in the figure, a plastic connection method for a nickel-based superalloy double web turbine disk includes the following steps: Step 1: As Figure 1 shown in the figure, prepare two blank annular half-disks 1, and the specific steps are as follows: Perform solution treatment and aging treatment on the nickel-based superalloy parts for preparing the double web turbine disk in sequence to improve the strength and toughness of the plastic connection of the superalloy; Specifically: Solution treatment: Heat-treat the nickel-based superalloy workpiece at a temperature of 1170°C to 1200°C for 2h to 6h, and then air-cool; Aging treatment: The nickel-based superalloy workpiece obtained by solution treatment is heat-treated at a temperature of 720°C to 730°C for 4h to 20h, and then air-cool; After completion, perform turning and milling composite machining on the obtained nickel-based superalloy parts to obtain two blank annular half-disks 1.

[0024] Step 2: Perform precision machining of grinding, turning and milling on the two blank annular half-disks 1 to process the relative connection ring surfaces of the two blank annular half-disks 1 to a flatness ≤ 0.05mm and the parallelism between the relative connection ring surfaces ≤ 0.05mm.

[0025] At the same time, the treatment of the connection end surfaces of the boss and groove structures is specifically as follows: First, use turning and milling machining to make the surface roughness Ra of the effective connection surface when the boss and groove are matched and connected ≤ 0.4; Then, polish the effective connection surface. The connection surface of the concave part is processed with a hand-held grinding machine and a wool grinding head until the surface roughness Ra of the effective connection surface ≤ 0.05. Then, perform ultrasonic cleaning, air-dry, and seal for storage for later use; After the treatment is completed, if the plastic connection cannot be completed within 24 hours, it is necessary to re-treat the effective connection surface and then perform the plastic connection.

[0026] Among them, the ultrasonic cleaning is ultrasonic cleaning with an ultrasonic frequency of 80 - 120kHz, a power density of 0.3 - 0.8W / CM 2 , a time of 5 - 10min, a cleaning temperature of 50 - 70°C, and a water-based cleaning agent as the cleaning agent. Finally, air-dry and seal for storage.

[0027] Step 3: Mechanically process annular bosses and annular groove structures for mating and clamping in plastic connection on the connection ring surfaces 11 at the disk edge and hub of the two blank annular half-disks 1 of the double web turbine disk respectively, so that after the boss and groove structures are fitted and connected, the thickness T of the groove is evenly distributed in the annular extension direction of the boss; AsFigure 2 As shown, in the connection section of the boss and groove structure, the height H of the boss is greater than the depth W of the groove, and the size of the boss embedded in the groove matches the size of the groove. The connection is an interference fit, and the interference fit code is H7 / s6, which is used to prevent loose assembly and reduce the connection rate; At the same time, the thickness T of the groove is greater than 10 mm, which is used to prevent the problem of difficulty in effectively providing radial compressive stress in the plastic connection due to the groove wall bulging outward to a greater extent than the boss bulging in the plastic connection.

[0028] Step 4: Assemble the two blank annular half-discs 1, specifically, align and assemble the boss and groove structures along the axial direction of the blank annular half-disc 1, and use positioning pins to position them on the mold so that the gap between the connecting surfaces of the two blank annular half-discs 1 is ≤0.02mm; At the same time, with the mold axis as the reference, the coaxiality between the mold and the two blank annular half disks 1 is within 0.025 mm; then, a relative initial pressure of 50-100 MPa is applied to the assembled two blank annular half disks 1 to make the two blank annular half disks 1 closely contact each other; Then, the two rough annular half disks 1 which have been precisely machined are assembled and connected using a boss and groove structure.

[0029] Step 5: Plastic connection is performed to achieve complete microscopic metallurgical bonding within the controllable macroscopic deformation of the disc rim and the hub to obtain a double-spoke turbine disc. The obtained structure is as follows: Figure 3 As shown, specifically: Evacuate to the vacuum degree of 10 -3 Under conditions above Pa, at a strain rate of 0.01~1s -1 , heating rate 1~10℃ / s, workpiece reaches 1100℃~1200℃ and keeps warm for 3~5min, plastic connection is performed with deformation of 30%~50%; The process parameters of plastic joining are used to ensure the expected joining effect during the plastic joining process. The increase in temperature and the decrease in strain rate during plastic joining are both conducive to the recrystallization of grains at the joining interface. However, excessively high temperature will cause the strengthening phase to dissolve back, causing microstructure coarsening and damaging the performance of the alloy workpiece. When the strain rate is too low, the new grains that have nucleated at the joining interface have sufficient time to significantly coarsen through the grain growth mechanism, resulting in uncontrolled grain size and a serious reduction in the mechanical properties of the joint. The greater the deformation, the better the connection effect. Under the same other conditions, the greater the deformation, the longer the plastic connection process lasts and the more complete the diffusion of interface atoms. At the same time, the large deformation can provide sufficient distortion energy to ensure that the interface grains undergo multiple rounds of recrystallization, which is beneficial to improving the connection effect. However, after the deformation amount exceeds the limited range, the boss and groove structures are significantly upset, and the metal flow condition will become more complex. If the metal flows on both sides of the interface cannot be synchronized, the atomic diffusion effect and tissue evolution of the joint cannot cross the interface, which will have no effect on plastic connection. After the plastic connection is completed, the two blank annular half-discs 1 are taken out and air-cooled to room temperature; this is used to prevent the two blank annular half-discs 1 from deforming and cracking, and during the air-cooling process, a slower cooling rate helps to control the grain growth of the workpiece and better achieve microstructural metallurgical bonding.

[0030] Step Six: The double-web turbine disk is subjected to recrystallization annealing and stress relief annealing in sequence, which is used for the recrystallization of the deformed grains remaining after plastic connection and promotes the cross-interface migration of grain boundary elements. Specifically: The recrystallization annealing is a heat treatment carried out at a temperature of 1050 - 1080 °C for 30 - 60 minutes, and then cooled in the furnace. The stress relief annealing is a heat treatment carried out at a temperature of 600 - 900 °C for 1 - 4 hours, and then cooled in the furnace.

[0031] Example 2: The same as Example 1, except that in the plastic connection, first, the two blank annular half-discs 1 assembled and connected through the boss and groove structures are put into the furnace and placed at the center of the furnace platform of the plastic connection equipment. Graphite limit blocks are placed on both sides of the two blank annular half-discs 1, and the height of the graphite limit blocks is 0.15 ± 0.05 mm lower than the height of the two blank annular half-discs 1 assembled and connected.

[0032] As Figures 4 - 8 shown, in order to further illustrate the technical solution and technical effect of the present invention, the following specific examples are provided: Specific Example 1: Plastic connection of a nickel-based superalloy double-web turbine disk with a planar joint Step One: Pretreatment of nickel-based superalloy: The pretreatment process of the superalloy workpiece before connection mainly includes solution treatment (1170 °C - 1200 °C / 2 h - 6 h / air cooling) and aging treatment (720 °C - 730 °C / 4 h - 20 h / air cooling).

[0033] Step Two: Machining of the left and right webs of the double-web turbine disk blank: The workpieces to be connected are precisely machined by using grinding and turning-milling compound machining. The workpieces to be connected are two nearly symmetrical blank half-discs, as shown in Figure 1 . The flatness of the two annular planes and the connection surface to be connected is machined to ≤ 0.05 mm, and the parallelism between any annular plane and the connection surface is ≤ 0.05 mm.

[0034] Step Three: Surface treatment of the joint before connection: Polish the mating surface, with the requirement that the surface roughness Ra of the end face ≤ 0.05. Subsequently, perform ultrasonic cleaning, air drying, and seal for storage for later use. If the connection cannot be completed within a short period, it is necessary to reprocess the joint surface to prevent surface oxidation and contamination.

[0035] Step Four: Assembly of the workpieces to be joined: As Figure 4 shown, on the die, axially butt-join the boss end of the workpiece groove, use a positioning pin for positioning, and check that the gap between the two mating surfaces ≤ 0.02 mm. Based on the axis of the die, the coaxiality is required to be within 0.025 mm. Apply an initial pressure to the workpiece to make it in close contact.

[0036] Step Five: Loading the workpiece into the furnace: Place the workpiece to be joined at the center of the furnace platform of the plastic connection equipment, and place graphite limit blocks on both sides. The graphite limit blocks are required to be 0.15 ± 0.05 mm lower than the workpiece to be joined, and then close the furnace door.

[0037] Step Six: Plastic connection of the workpiece: Perform vacuum pumping before plastic connection, and maintain a vacuum degree of 10 -3 Pa or more during the connection process. During the connection process, parameters such as temperature, time, strain rate, and deformation amount have a key impact on the metal flow, microstructure evolution, atomic diffusion, and interface micro-metallurgical bonding at the joint interface, and it is necessary to comprehensively consider and select the optimal parameters.

[0038] Step Seven: Removing the workpiece: After plastic connection, remove the workpiece and air-cool it to room temperature.

[0039] Step Eight: Heat treatment of the joined workpiece: Perform recrystallization annealing and stress relief annealing (1080 °C / 30 min / furnace cooling) on the air-cooled workpiece; Take samples from the plastic connection parts of the double web plate rim and the hub for characterization, as Figure 7 shown. It can be seen that only the central part of the entire mating surface is completely joined, and obvious welds still exist in a large range, indicating that the connection quality is poor at this time.

[0040] Specific Example 2: Plastic connection of a nickel-based superalloy double web plate turbine disk with a boss-groove joint Step One: Pretreatment of nickel-based superalloy: The pretreatment process of the nickel-based superalloy workpiece before connection mainly includes solution treatment (1170 °C - 1200 °C / 2 h - 6 h / air cooling) and aging treatment (720 °C - 730 °C / 4 h - 20 h / air cooling).

[0041] Step Two: Machining of the left and right web plates of the double web plate turbine disk blank Precision machining of the workpieces to be joined is carried out by means of grinding and turning-milling compound machining. The workpieces to be joined are two nearly symmetrical blank half-discs, as shown in Figure 1 . The two annular planes and the connecting surface to be joined are all machined to a flatness of ≤0.05 mm, and the parallelism between any annular plane and the connecting surface is ≤0.05 mm.

[0042] Step 3: Machining of the convex groove on the left and right web plates: Matching shapes are designed at the edges of the left and right web plates and the hub part to control the macroscopic distribution and microscopic distribution during the connection process. The matching shapes of the convex grooves on the workpieces to be joined are as shown in Figure 2 、 Figure 3 . The parameters are as follows: the groove depth is 1.5 mm, the convex height is 2 mm. The end surfaces of the workpieces to be joined are machined by turning and milling, and the surface roughness Ra of the workpieces to be joined is ≤0.4. To ensure the connection effect, an interference fit is required for the convex grooves to prevent assembly loosening and reduce the connection rate.

[0043] Step 4: Surface treatment of the joint before connection: The surface to be joined is polished, and the surface roughness Ra of the end surface is required to be ≤0.05. Subsequently, ultrasonic cleaning, air drying, and sealed storage are carried out for use. If the connection cannot be completed within a short time, the surface treatment of the joint needs to be carried out again to prevent surface oxidation and contamination.

[0044] Step 5: Assembly of the workpieces to be joined: As shown in Figure 4 , on the mold, the groove convex ends of the workpieces are axially butt-jointed and combined, and positioned with a positioning pin. Check that the gap between the two connecting surfaces is ≤0.02 mm. Based on the axis of the mold, the coaxiality is required to be within 0.025 mm. Apply an initial pressure to the workpieces to make them in close contact.

[0045] Step 6: Loading the workpieces into the furnace: Place the workpieces to be joined at the center of the furnace platform of the plastic connection equipment, and place graphite limit blocks on both sides. It is required that the graphite limit blocks are 0.15±0.05 mm lower than the workpieces to be joined, and then close the furnace door.

[0046] Step 7: Plastic connection of the workpieces: Vacuum pumping is carried out before plastic connection, and the vacuum degree is maintained above 10-3 Pa during the connection process. During the connection process, parameters such as temperature, time, strain rate, and deformation amount have a key impact on the metal flow, microstructure evolution, atomic diffusion, and interface micro-metallurgical bonding at the joint interface, and optimal parameters need to be comprehensively considered and selected.

[0047] Step 8: Taking out the workpieces: After plastic connection, take out the workpieces and air-cool them to room temperature.

[0048] Step 9: Heat treatment of the connected workpiece: Perform recrystallization annealing and stress relief annealing (1080 °C / 30 min / furnace cooling) on the workpiece after air cooling.

[0049] Take samples from the plastic connection parts of the double-web disc rim and hub for characterization, as Figure 8 shown. At this time, there is a tendency for the gap at the side wall of the boss to close, indicating that the groove wall effectively provides radial compressive stress to the joint core. An interfacial grain boundary is formed in the area of the boss chamfer, and the interfacial grain boundary quickly closes. A large number of fine grains appear at the original position of the weld, and almost the entire tabletop is completely welded; Obviously, the metallurgical bonding area of the boss-groove type joint is significantly larger than that of the flat joint model, proving that optimizing the joint shape is feasible for increasing the plastic connection rate.

[0050] Simulate the plastic connection process through finite element software (as Figure 5 and Figure 6 shown). The results show that the metal plastic flow of the optimized plastic connection joint is greater, and higher equivalent stress concentration can be achieved within a larger range of connection surfaces. This optimization measure can not only effectively drive the dynamic recrystallization and grain boundary migration processes, but also significantly improve the interfacial connection quality of the double-web turbine disc.

[0051] To more intuitively evaluate the quality of the joint connection effect, it is necessary to statistically compare the connection rates. Use a microhardness tester to mark points at the positions where the non-welded area transforms into the interfacial grain boundary and where the interfacial grain boundary disappears respectively, and then measure the connection lengths with and without the interfacial grain boundary.

[0052] The results show that after the shape of the flat joint is optimized, the plastic connection rate increases from the original 40.6% to 92.9%. It should be noted that the statistical results of this connection rate are affected by the joint profile position. To more intuitively show the influence of the joint shape on plastic connection, tensile tests on different joint shapes are also required.

[0053] The test results show that the maximum tensile load that the flat joint can withstand is 29.4 kN, while the boss-groove type joint can withstand a larger maximum tensile load, reaching 51.5 kN.

[0054] In summary, optimizing the shape of the plastic connection joint can effectively control the metal plastic flow in the joint area and achieve a higher level of equivalent stress concentration within a larger range of connection surfaces. This optimization can not only promote dynamic recrystallization and grain boundary migration, but also significantly improve the connection quality of the double-web turbine disc.

[0055] The above are only the preferred specific examples of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A plastic connection method for a nickel-based superalloy double web turbine disk, characterized in that, It includes the following steps: Step 1: Mechanically process the annular bosses and annular grooves for mating snap connection in plastic connection on the connecting ring surfaces (11) at the disc rims and hubs of the two blank annular half discs (1) of the double web turbine disc, so that after the boss and groove structures are fitted and connected, the thickness T of the groove is evenly distributed in the annular extension direction of the boss; Step 2: After assembling and connecting the two blank annular half discs (1) after precision machining using the boss and groove structures, perform plastic connection to achieve complete microstructural metallurgical bonding within the controllable macroscopic deformation at the disc rim and hub, obtaining the double web turbine disc; Step 3: Perform recrystallization annealing and stress relief annealing on the double web turbine disc in sequence, for the recrystallization of the deformed grains remaining after plastic connection and to promote the cross - interface migration of grain boundary elements.

2. The plastic connection method of the nickel-based superalloy double-web turbine disk according to claim 1, characterized in that In the connection section of the boss and groove structures, the height H of the boss is greater than the depth W of the groove, and the size of the boss embedded in the groove is in interference fit with the groove size, and the interference fit code is H7 / s6, to prevent the reduction of the connection rate caused by assembly loosening; Meanwhile, the thickness T of the groove is greater than 10 mm, to prevent the problem that in plastic connection, it is difficult to effectively provide radial compressive stress because the outward bulging degree of the groove wall is greater than that of the boss.

3. The plastic connection method of the nickel-based superalloy double web turbine disk according to claim 1, characterized in that The steps for preparing the two blank annular half discs (1) are: Perform solution treatment and aging treatment on the nickel - based superalloy parts for preparing the double web turbine disc in sequence, to improve the strength and toughness of the plastic connection of the superalloy; Specifically: Solution treatment: Heat - treat the nickel - based superalloy workpiece at a temperature of 1170 °C - 1200 °C for 2 h - 6 h, and then air - cool; Aging treatment: The nickel - based superalloy workpiece obtained by solution treatment is heat - treated at a temperature of 720 °C - 730 °C for 4 h - 20 h, and then air - cool; After completion, perform turning - milling composite machining on the obtained nickel - based superalloy parts, and two blank annular half discs (1) are obtained.

4. The plastic connection method of the nickel-based superalloy double web turbine disk according to claim 1, characterized in that, Perform precision machining of grinding and turning - milling composite on the two blank annular half discs (1) to machine the relative connecting ring surfaces of the two blank annular half discs (1) to a flatness ≤ 0.05 mm and a parallelism ≤ 0.05 mm between the relative connecting ring surfaces.

5. The plastic connection method of the nickel-based superalloy double web turbine disk according to claim 1, characterized in that, Before plastic connection, it also includes the treatment of the connecting end surfaces of the boss and groove structures. Specifically: First, use turning and milling machining to make the surface roughness Ra of the effective connection surface when the boss and groove are matched and connected ≤ 0.4; Then, polish the effective connection surface. The connecting surface of the concave part is processed with a handheld grinding machine and a wool grinding head until the surface roughness Ra of the effective connection surface ≤ 0.05, and then perform ultrasonic cleaning, air - drying, and seal - preservation for standby; After the treatment is completed, if the plastic connection cannot be completed within 24 hours, it is necessary to re - treat the effective connection surface and then perform plastic connection.

6. The plastic connection method of the nickel-based superalloy double web turbine disk according to claim 5, characterized in that, The ultrasonic cleaning is carried out at an ultrasonic frequency of 80 - 120 kHz, a power density of 0.3 - 0.8 W / cm 2 , for a time of 5 - 10 minutes, at a cleaning temperature of 50 - 70 °C, with a water-based cleaning agent. Finally, it is dried and stored in a sealed manner.

7. The plastic connection method of the nickel-based superalloy double web turbine disk according to claim 1, characterized in that, In Step 2, before plastic connection, the assembly of the two blank annular half-discs (1) is specifically to axially butt-join the boss and groove structures along the blank annular half-disc (1) and use a positioning pin to position them on the die, so that the clearance between the joint surfaces of the two blank annular half-discs (1) is ≤0.02 mm; Meanwhile, with the die axis as the reference, the coaxiality between the die and the two blank annular half-discs (1) is within 0.025 mm; then, a relative initial pressure of 50-100 MPa is applied to the two assembled blank annular half-discs (1) to make the two blank annular half-discs (1) in close contact.

8. The plastic connection method of the nickel-based superalloy double-web turbine disk according to claim 1, characterized in that The plastic connection of the two assembled blank annular half-discs (1) is specifically as follows: Under the condition of evacuating the furnace to a vacuum degree of more than 10 -3 Pa, with a strain rate of 0.01~1 s -1 , a heating rate of 1~10 °C / s, after the workpiece reaches a temperature of 1100 °C~1200 °C, it is heat-insulated for 3~5 min, and plastic connection is carried out with a deformation amount of 30%~50%; The process parameters of plastic connection are used to ensure the expected connection effect during the plastic connection process. The increase in temperature and the decrease in strain rate during plastic connection are both beneficial to grain recrystallization at the connection interface. However, too high a temperature will cause the strengthening phase to dissolve back, leading to tissue coarsening and damaging the performance of the alloy workpiece; when the strain rate is too low, the newly nucleated grains at the connection interface have sufficient time to significantly coarsen through the grain growth mechanism, resulting in out-of-control grain size and severely reducing the mechanical properties at the joint. The greater the deformation amount, the better the connection effect. Under the same other conditions, the greater the deformation amount, the longer the duration of the plastic connection process, the more sufficient the interfacial atomic diffusion, and at the same time, a large deformation amount can provide sufficient distortion energy to ensure multiple rounds of recrystallization of the interfacial grains, which is beneficial to improving the connection effect; However, after the deformation amount exceeds the specified range, the boss and groove structures are significantly upset, and the metal flow situation will become more complex. If the metal flow on both sides of the interface cannot be synchronized, the atomic diffusion effect and tissue evolution at the joint cannot cross the interface, which has no effect on plastic connection; After completing the plastic connection, the two blank annular half-discs (1) are taken out and air-cooled to room temperature; this is used to prevent the two blank annular half-discs (1) from deforming and cracking, and during the air-cooling process, a slower cooling rate helps to control the grain growth of the workpiece and better achieve microstructural metallurgical bonding.

9. The plastic connection method of the nickel-based superalloy double web turbine disk according to claim 8, characterized in that In the described plastic connection, first, the two blank annular half-discs (1) assembled and connected through the boss and groove structures are put into the furnace and placed at the center of the furnace platform of the plastic connection equipment. Graphite limit blocks are placed on both sides of the two blank annular half-discs (1), and the height of the graphite limit blocks is 0.15±0.05 mm lower than the height of the two assembled blank annular half-discs (1).

10. The plastic connection method of the nickel-based superalloy double-web turbine disk according to any one of claims 1-9, characterized in that, The specific content of Step 3 is as follows: Recrystallization annealing is a heat treatment carried out at a temperature of 1050-1080 °C for 30-60 min and cooled in the furnace; Stress relief annealing is a heat treatment carried out at a temperature of 600-900 °C for 1-4 h and cooled in the furnace.

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