A vacuum brazing process for improving the oxidation resistance of a GH4738 and GH3536 alloy assembly

Abstract

The application provides a vacuum brazing process for improving the oxidation resistance of a GH4738 and GH3536 alloy assembly, and relates to the technical field of improving the oxidation resistance of an assembly of two different component alloys. The method comprises surface treatment of alloy parts to be welded to obtain clean alloy parts; assembling and fixing the two alloys; prepositioning of the filler metal; and finally, vacuum brazing heat treatment of the assembly with the filler metal. The application controls the gap size of the two alloy brazed joints by synergistically controlling the type and amount of filler metal, so that the alloy assembly has unexpected effects in terms of oxidation resistance, and the service life of the assembly in a high-temperature oxidation environment is improved. After the process of the application, the assembly reaches the complete oxidation resistance level under the condition of high-temperature oxidation at 730 DEG C, and the oxidation resistance is at least 1 times higher. The method is stable, easy to implement, low in cost, high in efficiency, and conducive to large-scale industrial production and popularization and application.

Description

Technical Field

[0001] This invention relates to the technical field of improving the oxidation resistance of assemblies made of two different alloys, and in particular to a vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies. Background Technology

[0002] High-temperature alloys, as key basic materials in high-end manufacturing, were initially developed to meet the research and development needs of aero-jet engines. These alloys can withstand the erosion of harsh conditions such as oxidation and gas corrosion in high-temperature environments ranging from 600 to 1200°C, stably withstand various complex alternating stresses, and ensure long-term safe service. They are core materials supporting the high performance and high reliability of high-end equipment. However, with the continuous development of aerospace technology, the service conditions of equipment such as jet engines and gas turbines in extreme environments such as high temperature, thermal shock, and strong airflow are becoming increasingly demanding. A single high-temperature alloy can no longer fully meet the performance requirements of complex structural components, making the need for dissimilar material joining increasingly urgent. For example, ceramic matrix composites (such as SiCf / SiC), with their excellent properties such as high melting point, low coefficient of thermal expansion, and strong oxidation resistance, often need to be joined with high-temperature alloys such as GH3039 and GH3536 to fabricate devices with complex shapes. However, the mismatch in the coefficients of thermal expansion and excessive interfacial reactions pose serious challenges to reliable joining.

[0003] GH3536 alloy is a solid solution strengthened nickel-based superalloy with advantages such as high hot strength and good cold and hot workability. GH3536 honeycomb structures, manufactured using laser spot welding, are widely used in aero-engines. GH4738 is a γ′ phase precipitation strengthened nickel-based superalloy with good workability and stable microstructure, suitable for manufacturing large-size forged ring components such as turbine disks and guide vane inner rings. During the production of a certain type of aero-engine, to improve the sealing effect of the guide vane inner ring, the GH3536 honeycomb structure and GH4738 ring components needed to be connected by vacuum brazing. As a core component of the low-pressure turbine of an aero-engine, the guide vane inner ring needs to withstand temperatures up to 730℃. However, dissimilar brazed joints still face severe oxidation damage during long-term high-temperature service, which not only leads to a decline in the mechanical properties of the joint but may also cause hot cracks and residual stress concentration, ultimately endangering the safety and reliability of the overall structure.

[0004] During high-temperature oxidation service, repeated thermal cycling generates alternating thermal stress inside the joint, which in turn induces the initiation and propagation of microcracks. These cracks not only directly weaken the joint's load-bearing capacity but also provide a rapid pathway for oxygen diffusion inward, allowing the oxidation reaction to continue penetrating along the crack interface, forming a vicious cycle of "oxidation promoting cracking, and cracking accelerating oxidation." Furthermore, the high-temperature oxidation occurring in the guide vane inner ring / weld / honeycomb structure, as heterogeneous structures, differs under high-temperature conditions. In particular, the weld, as a weak area, is more prone to oxidation, ultimately leading to material failure.

[0005] Existing research mainly focuses on the condition of welded joints and the optimization of base alloy properties. However, oxidation under high-temperature environments affects the failure of welded joints. The literature "Bakhtiari H, Farvizi M, Rahimipour MR, et al. Influence of bonding temperature on interfacial microstructure and high-temperature oxidation behavior of transient liquid phase (TLP) bonded Hastelloy X joints[J]. Materials & Design, 2025,258:114740." studied the effect of brazing bonding temperature on the interfacial microstructure and high-temperature oxidation behavior of GH4738 alloy joints. It proposed that a bonding temperature of 1160℃ improves the uniformity of the joint microstructure and provides the best oxidation resistance. However, increasing the temperature is too high for the GH4738 and GH3536 base alloys, leading to a decrease in the performance of the base alloys.

[0006] For example, Chinese patent CN113600950A discloses a multiple brazing and heat treatment process to improve the strength and stability of GH4738 alloy. By setting up multiple high-temperature brazing processes, it solves the problem of insufficient alloy welding performance in actual production. However, it only considers the performance of the welded joint in terms of strength and stability. The defect of this patent is that it only considers the improvement of the strength and stability of the master alloy and does not consider the strength of the welded joint. Moreover, multiple brazings cause the brazing filler metal to melt and solidify repeatedly, resulting in the loss of brazing filler metal.

[0007] Chinese patent CN114571024A discloses a vacuum brazing process to reduce the corrosion of GH3536 honeycomb and GH4738 ring components. By controlling the boron content of the brazing filler metal, the diffusion effect of elements in the brazed joint is weakened, thus protecting the brazed joint from corrosion. However, this process only considers the influence of the brazing filler metal on the brazed joint and does not reflect its performance in a real service environment.

[0008] Chinese patent CN114769772A discloses a vacuum brazing method to improve the strength of GH3536 / GH4738 alloy joints. By controlling the joint gap within the range of 30-50μm, a brazed joint with higher strength is obtained. However, the joint cannot achieve complete isothermal solidification within the range of 40-50μm, resulting in insufficient oxidation resistance. The method shown in this patent cannot fully guarantee both strength and oxidation resistance, affecting service performance in real-world environments.

[0009] In summary, there is currently a lack of technology that can further improve the oxidation resistance of brazed joints without reducing their mechanical properties. Furthermore, the optimized process of this invention has unexpected effects on improving the oxidation resistance of the assembly, achieving at least a 100% improvement compared to existing technologies. Summary of the Invention

[0010] The technical problem to be solved by this invention is that the gap between the brazed joints of GH4738 and GH3536 alloy assemblies in the prior art cannot be strictly controlled, and is on the order of hundreds of micrometers. This results in the weld not being able to form an isothermal solidification structure, weakening the weld strength and reducing the oxidation resistance. In addition, the use of powdered brazing filler metal cannot guarantee the filling effect of the filler metal during short-term brazing, resulting in cracks in the alloy weld and a poor assembly qualification rate. Furthermore, the service life of the assembly is short.

[0011] The existing brazing technology involves: not controlling the joint gap, with an average value of 100μm; after fixing the base alloy, filling with powdered brazing filler metal, compacting, and then undergoing traditional vacuum brazing heat treatment: removing the vacuum level in the furnace to 10... -3 Below Pa, the brazing furnace is heated to 700-900℃ at a rate of 5-15℃ / min and held for 20-30min to preheat the assembly; the brazing furnace is heated to 1030-1040℃ at a rate of 5-10℃ / min and held for 8-10min for brazing; after brazing, the furnace is filled with high-purity argon to accelerate cooling until it drops below 80℃, and the assembly is taken out of the furnace. A high vacuum environment is maintained throughout the process.

[0012] Therefore, a vacuum brazing process to improve the oxidation resistance of GH4738 and GH3536 alloy assemblies was proposed, which can solve the aforementioned problems.

[0013] The technical solution is as follows: A vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies, comprising the following steps: S1. Surface pretreatment of two base materials: First, the two base material alloys GH3536 and GH4738 are processed into the required size by wire cutting. Then, the welding surfaces of the two base material alloys are polished with sandpaper. After that, the surfaces of the two base materials are wiped with acetone to obtain two base material alloys with smooth surfaces and no impurities. S2. Assembly and fixing of the assembly: The two base alloys with smooth and impurity-free surfaces from S1 are overlapped in a staggered manner, with alloy spacers in the middle. Then, the assembly is fixed with a clamp, and finally, the base alloys are further fixed by spot welding to obtain a fixed assembly of the two base alloys. S3, Pre-set brazing filler metal + flow retardant setting: Apply the prepared paste brazing filler metal evenly to the gaps and non-overlapping areas of the fixed assembly of the two base alloys in S2, and apply a flow retardant to the outside of the mating surface of the fixed assembly of the two base alloys to prevent the brazing filler metal from overflowing during the brazing process, and obtain the assembled assembly. S4: Vacuum brazing heat treatment: The assembled components from S3 are placed in a vacuum brazing furnace for vacuum brazing heat treatment, followed by cooling to obtain oxidation-resistant GH4738 and GH3536 alloy assemblies.

[0014] Optionally, the two base alloys in S1 are wire-cut to a size of 100-120mm×11-14mm×5-7mm, of which 100-120mm×11-14mm is the welding surface.

[0015] Optionally, in S1, the alloy surface to be welded should be polished in sequence using 400#, 600#, 1000#, and 1500# sandpaper.

[0016] Optionally, the surface roughness of the two base alloys in S1 after being sanded is 0.05-0.1μm.

[0017] Optionally, the overlap area of ​​the staggered overlap in S2 is 100-120mm×10mm, with a step in the width direction.

[0018] Optionally, the alloy gasket in S2 is a nickel-based alloy with a thickness of 30-40 μm.

[0019] Optionally, the process parameters for spot welding in S2 are: welding current of 4.5-6.0kA, welding time of 0.02-0.5s, electrode pressure of 5-10kN, and electrode end diameter of 5-8mm.

[0020] Optionally, the solder paste in S3 is nickel-based solder BNi-2 with a melting point of 985-995℃. The amount of solder used should be controlled to cover the weld area and the non-overlapping platform area. The flow retardant is mainly composed of traditional metal oxides that form an outer film during the brazing process to prevent solder overflow. The flow retardant is applied precisely and continuously to the boundary of the area to be protected, including the outer side of the mating surface of the fixed assembly. The amount required is to continuously cover the outer side by 0.05-0.1mm.

[0021] Optionally, the vacuum brazing process in S4 is as follows: the assembly is placed at room temperature, and the vacuum level inside the furnace is reduced to 10. -3 Below Pa, the brazing furnace is heated to 700-900℃ at a rate of 5-15℃ / min and held for 20-30min to preheat the assembly; the brazing furnace is heated to 1030-1040℃ at a rate of 5-10℃ / min and held for 8-10min for brazing; after brazing, the furnace is filled with high-purity argon to accelerate cooling until it drops below 80℃, and the assembly is taken out of the furnace. A high vacuum environment is maintained throughout the process.

[0022] Optionally, samples of the oxidation-resistant GH4738 and GH3536 alloy assembly in S4 were taken and subjected to high-temperature oxidation at 730℃ for 100 hours. The oxidation rate was characterized by statistically analyzing the weight gain of the samples during oxidation, and the oxidation rate was 0.0234 ± 0.0005 g / (m³). 2 ·h).

[0023] Optionally, the performance data of the oxidation-resistant GH4738 and GH3536 alloy combination in S4 are as follows: room temperature mechanical properties: room temperature shear strength is 404-429 MPa, and high temperature mechanical properties: high temperature shear strength at 540℃ is 375-397 MPa.

[0024] Technical principle of the invention: The present invention describes polishing two master alloys (GH4738 and GH3536) sequentially with 400#, 600#, 1000# and 1500# sandpaper to control their surface roughness to below 0.1μm, ensuring a smooth surface, improving the fluidity of the brazing filler metal, and ensuring the integrity of the solidification structure of the joint gap.

[0025] The vacuum brazing process described in this invention uses a temperature of 1030-1040℃. According to the high-temperature alloy handbook, this temperature is higher than the solution temperature range of GH4738 and GH3536 alloys. In order to ensure the strength of the master alloy, short-time brazing is adopted, and the holding time is set to 8-10 minutes. This also ensures that the brazing filler metal completely melts and wets the entire weld.

[0026] The key focus of this invention is the control of the gap in brazed joints. Since brazing utilizes capillary action to allow molten filler metal to flow into the joint gap, correctly selecting the gap size is crucial to determining the weld tightness. A gap that is too small will make it difficult for the filler metal to fill, reducing weld tightness and joint strength; a gap that is too large will disrupt the capillary action and hinder the filler metal from filling the joint.

[0027] Furthermore, the solidification of the brazing filler metal during brazing is mainly controlled by the diffusion process dominated by boron. At a fixed brazing temperature and time, when the joint gap is large, the element cannot diffuse completely. After moving a fixed distance, it accumulates in the middle of the weld, easily forming brittle and harmful phases such as borides, reducing the weld's oxidation resistance. This invention precisely controls the joint gap value within the range of 30-40 μm. While ensuring good wetting between the brazing filler metal and the base metal, it also facilitates isothermal solidification within the weld, generating a uniform solid solution structure and significantly improving the joint's oxidation resistance.

[0028] The above technical solution has at least the following advantages compared with the existing technology: The above-mentioned solution proposes a vacuum brazing process to improve the oxidation resistance of GH4738 and GH3536 alloy assemblies, which can solve the technical problems existing in the prior art, such as the difference in oxidation capacity of dissimilar alloy brazing components, weak brazed joints, and short service life.

[0029] This invention uses two pretreatments of the base materials to make the surfaces of the two base alloys smooth, reduce roughness, and improve the fluidity of the brazing filler metal.

[0030] This invention creates steps in the assembly and fixing of components, especially by using an uneven overlapping method, which promotes the conversion of powdered brazing filler metal into paste-like brazing filler metal, improves the fluidity of the brazing filler metal, and makes the weld joint structure more complete. By using metal gaskets of different specifications to block the alloy, the gap of the brazed joint of the alloy assembly is strictly controlled. The process is simple, efficient, and accurate.

[0031] This invention, through the pre-placed brazing filler metal and flow retardant, enables the brazing filler metal to fill the welding gap of the fixed alloy component through capillary action during a short-time vacuum brazing process. Furthermore, the flow retardant ensures that the brazing filler metal does not overflow, reducing material waste and improving the yield.

[0032] This invention, through coordinated control of the type and amount of brazing filler metal, and simultaneous control of the gap size of the brazed joints of the two alloys, enables the alloy assembly to have unexpected effects in terms of oxidation resistance, thereby improving the service life of the assembly in high-temperature oxidizing environments.

[0033] This invention uses a nickel-based brazing filler metal with a melting point of 985-995℃, and selects matching brazing process parameters: brazing temperature of 1030-1040℃ and brazing holding time of 8-10 minutes, which fully comply with existing industrial settings, ensures the fluidity of the brazing filler metal, and improves the strength of the alloy brazed joint.

[0034] This invention uses strip-shaped brazing filler metal as an alloy spacer, which enables precise control of the gap between the brazed joints of the two base material alloys. Moreover, there is no need to remove the alloy spacer after assembly, thus optimizing the process steps and simplifying the operation. Its composition is also consistent with the subsequent paste-like brazing filler metal, ensuring the uniformity of the brazed joint.

[0035] The present invention has a complete process and high operating efficiency. While maintaining the mechanical properties of the alloy assembly joint, isothermal solidification is achieved by precisely controlling the gap of the brazed joint, which has an unexpected effect on improving the oxidation resistance of the assembly, enabling the alloy parts to reach the level of complete oxidation resistance, and improving the oxidation resistance by at least 1 time.

[0036] In summary, compared with traditional alloy component brazing methods, this invention obtains high-oxidation-resistant GH4738 and GH3536 alloy assembly products through two types of base material surface pretreatment, assembly and fixing of the assembly, pre-placed brazing filler metal + flow retardant setting, and vacuum brazing heat treatment. This method is stable, easy to implement, low in cost, and highly efficient, which is conducive to large-scale industrial production and widespread application. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a macroscopic morphology image of the GH4738 and GH3536 alloy assembly of Embodiment 1 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 2 This is a scanning electron microscope image of the surface of the GH4738 and GH3536 alloy assembly of Embodiment 1 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 3 This is a scanning electron microscope image of the cross-section of the GH4738 and GH3536 alloy assembly of Embodiment 1 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 4 This is a macroscopic morphology image of the GH4738 and GH3536 alloy assembly of Comparative Example 1 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 5 This is a scanning electron microscope image of the surface of the GH4738 and GH3536 alloy assembly of Comparative Example 1 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 6 This is a scanning electron microscope image of the cross-section of the GH4738 and GH3536 alloy assembly of Comparative Example 1 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 7 This is a macroscopic morphology image of the GH4738 and GH3536 alloy assembly of Comparative Example 2 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 8 This is a scanning electron microscope image of the surface of the GH4738 and GH3536 alloy assembly of Comparative Example 2 of the present invention after high-temperature oxidation at 730°C for 100 hours. Figure 9 This is a scanning electron microscope image of the cross-section of the GH4738 and GH3536 alloy assembly of Comparative Example 2 of the present invention after high-temperature oxidation at 730°C for 100 hours. Detailed Implementation

[0039] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0040] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0041] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0042] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0043] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0044] A vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies, comprising the following steps: S1. Surface pretreatment of two base materials: First, the two base material alloys GH3536 and GH4738 are processed into the required size by wire cutting. Then, the welding surfaces of the two base material alloys are polished with sandpaper. After that, the surfaces of the two base materials are wiped with acetone to obtain two base material alloys with smooth surfaces and no impurities. S2. Assembly and fixing of the assembly: The two base alloys with smooth and impurity-free surfaces from S1 are overlapped in a staggered manner, with alloy spacers in the middle. Then, the assembly is fixed with a clamp, and finally, the base alloys are further fixed by spot welding to obtain a fixed assembly of the two base alloys. S3, Pre-set brazing filler metal + flow retardant setting: Apply the prepared paste brazing filler metal evenly to the gaps and non-overlapping areas of the fixed assembly of the two base alloys in S2, and apply a flow retardant to the outside of the mating surface of the fixed assembly of the two base alloys to prevent the brazing filler metal from overflowing during the brazing process, and obtain the assembled assembly. S4: Vacuum brazing heat treatment: The assembled components from S3 are placed in a vacuum brazing furnace for vacuum brazing heat treatment, followed by cooling to obtain oxidation-resistant GH4738 and GH3536 alloy assemblies.

[0045] Specifically, the two base alloys in S1 have dimensions of 100-120mm×11-14mm×5-7mm after wire cutting, of which 100-120mm×11-14mm is the welding surface.

[0046] Specifically, in S1, the alloy surfaces to be welded must be polished in sequence using 400#, 600#, 1000#, and 1500# sandpaper.

[0047] Specifically, the surface roughness of the two base alloys in S1 after being sanded is 0.05-0.1μm.

[0048] Specifically, the overlap area of ​​the staggered overlap in S2 is 100-120mm×10mm, with a step in the width direction.

[0049] Specifically, the alloy gasket in S2 is a nickel-based alloy with a thickness of 30-40 μm.

[0050] Specifically, the process parameters for spot welding in S2 are: welding current of 4.5-6.0kA, welding time of 0.02-0.5s, electrode pressure of 5-10kN, and electrode end diameter of 5-8mm.

[0051] Specifically, the solder paste in S3 is a nickel-based solder BNi-2 with a melting point of 985-995℃. The amount of solder used should be controlled to cover the weld seam area and the non-overlapping platform area. The flow retardant is mainly composed of traditional metal oxides that form an outer film during the brazing process to prevent solder overflow. The flow retardant should be applied precisely and continuously to the boundary of the area to be protected, including the outer side of the mating surface of the fixed assembly. The amount required is to continuously cover the outer side by 0.05-0.1mm.

[0052] Specifically, the vacuum brazing process in S4 involves: placing the assembly at room temperature and then evacuating the furnace to a vacuum level of 10. -3 Below Pa, the brazing furnace is heated to 700-900℃ at a rate of 5-15℃ / min and held for 20-30min to preheat the assembly; the brazing furnace is heated to 1030-1040℃ at a rate of 5-10℃ / min and held for 8-10min for brazing; after brazing, the furnace is filled with high-purity argon to accelerate cooling until it drops below 80℃, and the assembly is taken out of the furnace. A high vacuum environment is maintained throughout the process.

[0053] Specifically, samples of the GH4738 and GH3536 alloy assemblies with oxidation resistance in S4 were taken and subjected to high-temperature oxidation at 730℃ for 100 hours. The oxidation rate was characterized by statistically analyzing the weight gain of the samples during oxidation, and the oxidation rate was 0.0234 ± 0.0005 g / (m³). 2 ·h).

[0054] Specifically, the performance data of the oxidation-resistant GH4738 and GH3536 alloy combination in S4 are as follows: room temperature mechanical properties: room temperature shear strength is 404-429 MPa, and high temperature mechanical properties: high temperature shear strength at 540℃ is 375-397 MPa.

[0055] High-temperature antioxidant performance assessment: The high-temperature oxidation resistance assessment was conducted according to the national standard GB / T 38430-2019 "Corrosion of metals and alloys - Isothermal exposure oxidation test method for metallic materials under high-temperature corrosion conditions". The samples in the examples and comparative examples that underwent vacuum brazing heat treatment were subjected to a high-temperature oxidation test at 730℃. The oxidation rate was characterized by the statistical analysis of the sample oxidation weight gain by weighing.

[0056] Example 1

[0057] This embodiment provides a vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies includes the following steps: S1. Surface pretreatment of the two base materials: First, GH3536 and GH4738 base material alloys were processed into strips of 110mm×12mm×5mm using wire cutting. The welding surface was 110mm×12mm. The welding surface of the alloy was polished with 400#, 600#, 1000#, and 1500# sandpaper in sequence to remove the oxide scale on the surface of the base material alloy and obtain a smooth surface. The surface of the base material was wiped with acetone to remove oil and other impurities, resulting in two base material alloys with smooth and impurity-free surfaces. The surface roughness of the welding surface of the two base material alloys after sandpaper polishing was 0.07μm. S2. Assembly and Fixing of the Assembly: The two base alloys with smooth and impurity-free surfaces from S1 are overlapped in a staggered manner with an overlap area of ​​110mm × 10mm. A step is left in the width direction, and a 35μm nickel-based alloy is used as an alloy spacer in the middle. Then, the assembly is fixed with a clamp. Finally, the base alloy is further fixed by spot welding. The process parameters for spot welding are: welding current of 5.0kA, welding time of 0.5s, electrode pressure of 7kN, and electrode end diameter of 8mm, to obtain a fixed assembly of the two base alloys. S3. Pre-applied solder + flow retardant: The prepared paste-like nickel-based solder BNi-2 is evenly applied to the gaps and non-overlapping areas (100mm × 2mm platform) of the fixed assembly of the two base alloys in S2. The chemical composition of the paste-like nickel-based solder BNi-2, by mass percentage, is: Cr 7.2%, B 2.4%, Si 4.6%, Fe 3.3%, with the remainder being Ni and unavoidable impurities. A flow retardant, a traditional oxide, is applied to the outer side of the mating surface of the fixed assembly to prevent solder overflow during brazing. It is precisely and continuously applied to the boundary of the area to be protected, i.e., the outer side of the mating surface of the fixed assembly, with only a thin, continuous layer covering the outer side, approximately 0.1mm thick, resulting in the assembled assembly. S4: Vacuum Brazing Heat Treatment: Place the assembled components from S3 into a vacuum brazing furnace for vacuum brazing heat treatment. The vacuum brazing process is as follows: place the assembly at room temperature, and then evacuate the furnace to a vacuum level of 10. -3 Below Pa, the brazing furnace is heated to 840℃ at a rate of 10℃ / min and held for 30min to preheat the assembly; the brazing furnace is then heated to 1040℃ at a rate of 7℃ / min and held for 10min for brazing; after brazing, the furnace is filled with 0.3MPa high-purity argon gas to accelerate cooling until it drops below 80℃, and the assembly is removed from the furnace while maintaining a high vacuum environment throughout; after cooling, oxidation-resistant GH4738 and GH3536 alloy assemblies are obtained.

[0058] like Figure 1 , Figure 2 and Figure 3As shown, macroscopic photographs and scanning electron microscope images of the alloy assemblies prepared by this process after oxidation at 730℃ for 100 hours show that the degree of alloy oxidation is obvious under medium joint gap conditions.

[0059] In this embodiment, samples were taken from the antioxidant GH4738 and GH3536 alloy assembly. Three parallel samples were prepared and subjected to high-temperature oxidation at 730℃ for 100 hours. The oxidation rate was characterized by the weight gain of the samples during oxidation, and the oxidation rate was 0.0238 g / (m³). 2 ·h), 0.0234g / (m 2 ·h), 0.0229g / (m 2 ·h).

[0060] Performance data of the oxidation-resistant GH4738 and GH3536 alloy composites prepared in this embodiment: Room temperature mechanical properties: room temperature shear strength is 404 MPa, 421 MPa, and 429 MPa; High temperature mechanical properties: high temperature shear strength at 540℃ is 375 MPa, 364 MPa, and 397 MPa.

[0061] Comparative Example 1

[0062] This comparative example describes a vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies includes the following steps: S1. Surface pretreatment of the two base materials: First, GH3536 and GH4738 base material alloys were processed into strips of 110mm×12mm×5mm using wire cutting. The welding surface was 110mm×12mm. The welding surface of the alloy was polished with 400#, 600#, 1000#, and 1500# sandpaper in sequence to remove the oxide scale on the surface of the base material alloy and obtain a smooth surface. The surface of the base material was wiped with acetone to remove oil and other impurities, resulting in two base material alloys with smooth and impurity-free surfaces. The surface roughness of the welding surface of the two base material alloys after sandpaper polishing was 0.07μm. S2. Assembly and fixing of the assembly: The two base alloys with smooth and impurity-free surfaces in S1 are overlapped in a staggered manner with an overlap area of ​​110mm×10mm. A step is left in the width direction. A 55μm nickel-based alloy is used as an alloy spacer in the middle. Then, the assembly is fixed with a clamp to obtain a fixed assembly of the two base alloys. S3. Pre-applied solder + flow retardant: The prepared paste-like nickel-based solder BNi-2 is evenly applied to the gaps and non-overlapping areas (100mm×2mm platform) of the fixed assembly of the two base alloys in S2. The chemical composition of the paste-like nickel-based solder BNi-2, by mass percentage, is: Cr 7.1%, B 2.4%, Si 4.5%, Fe 3.3%, with the remainder being Ni and unavoidable impurities. A flow retardant, a traditional oxide, is applied to the outer side of the mating surface of the fixed assembly to prevent solder overflow during brazing. It is precisely and continuously applied to the boundary of the area to be protected, i.e., the outer side of the mating surface of the fixed assembly, with only a thin, continuous layer covering the outer side, approximately 0.1mm thick, resulting in the assembled assembly. S4: Vacuum Brazing Heat Treatment: Place the assembled components from S3 into a vacuum brazing furnace for vacuum brazing heat treatment. The vacuum brazing process is as follows: place the assembly at room temperature, and then evacuate the furnace to a vacuum level of 10. -3 Below Pa, the brazing furnace is heated to 850℃ at a rate of 12℃ / min and held for 30min to preheat the assembly; the brazing furnace is then heated to 1040℃ at a rate of 6℃ / min and held for 10min for brazing; after brazing, the furnace is filled with 0.3MPa high-purity argon gas to accelerate cooling until it drops below 80℃, and the assembly is removed from the furnace while maintaining a high vacuum environment throughout; after cooling, oxidation-resistant GH4738 and GH3536 alloy assemblies are obtained.

[0063] like Figure 4 , Figure 5 and Figure 6 As shown, macroscopic photographs and scanning electron microscope images of the alloy assemblies prepared by this process after oxidation at 730℃ for 100 hours show that the degree of alloy oxidation is obvious under medium joint gap conditions.

[0064] In this comparative example, samples were taken from the oxidation-resistant GH4738 and GH3536 alloy assemblies prepared in parallel. All samples underwent high-temperature oxidation at 730℃ for 100 hours. The oxidation rate was characterized by the weight gain of the samples during oxidation, and the oxidation rates were 0.0589 g / (m³). 2 ·h), 0.0583g / (m 2 ·h), 0.0584g / (m 2 ·h).

[0065] The room temperature mechanical properties of the oxidation-resistant GH4738 and GH3536 alloy composites prepared in this comparative example are as follows: room temperature shear strength is 334 MPa, 349 MPa, and 363 MPa; high temperature mechanical properties are as follows: high temperature shear strength at 540℃ is 286 MPa, 315 MPa, and 308 MPa.

[0066] Comparative Example 2

[0067] This comparative example describes a vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies includes the following steps: S1. Surface pretreatment of the two base materials: First, GH3536 and GH4738 base material alloys were processed into strips of 110mm×12mm×5mm using wire cutting. The welding surface was 110mm×12mm. The welding surface of the alloy was polished with 400#, 600#, 1000#, and 1500# sandpaper in sequence to remove the oxide scale on the surface of the base material alloy and obtain a smooth surface. The surface of the base material was wiped with acetone to remove oil and other impurities, resulting in two base material alloys with smooth and impurity-free surfaces. The surface roughness of the welding surface of the two base material alloys after sandpaper polishing was 0.07μm. S2. Assembly and Fixing of the Assembly: The two base alloys with smooth and impurity-free surfaces from S1 are overlapped in a staggered manner with an overlap area of ​​110mm × 10mm. A step is left in the width direction, and a 100μm nickel-based alloy is used as an alloy spacer in the middle. Then, the assembly is fixed with a clamp. Finally, the base alloys are further fixed by spot welding. The process parameters for spot welding are: welding current of 5.0kA, welding time of 0.5s, electrode pressure of 7kN, and electrode end diameter of 8mm, to obtain a fixed assembly of the two base alloys. S3. Pre-applied solder + flow retardant: The prepared paste-like nickel-based solder BNi-2 is evenly applied to the gaps and non-overlapping areas (100mm×2mm platform) of the fixed assembly of the two base alloys in S2. The chemical composition of the paste-like nickel-based solder BNi-2, by mass percentage, is: Cr 7.0%, B 2.5%, Si 4.6%, Fe 3.2%, with the remainder being Ni and unavoidable impurities. A flow retardant, a traditional oxide, is applied to the outer side of the mating surfaces of the fixed assembly to prevent solder overflow during brazing. It is precisely and continuously applied to the boundary of the protected area, i.e., the outer side of the mating surfaces of the fixed assembly, with only a thin, continuous layer covering the outer side, approximately 0.1mm thick, resulting in the assembled assembly. S4: Vacuum Brazing Heat Treatment: Place the assembled components from S3 into a vacuum brazing furnace for vacuum brazing heat treatment. The vacuum brazing process is as follows: place the assembly at room temperature, and then evacuate the furnace to a vacuum level of 10. -3Below Pa, the brazing furnace is heated to 830℃ at a rate of 14℃ / min and held for 30min to preheat the assembly; the brazing furnace is then heated to 1040℃ at a rate of 7℃ / min and held for 10min for brazing; after brazing, the furnace is filled with 0.3MPa high-purity argon gas to accelerate cooling until it drops below 80℃, maintaining a high vacuum environment throughout the process; after cooling, oxidation-resistant GH4738 and GH3536 alloy assemblies are obtained.

[0068] like Figure 7 , Figure 8 and Figure 9 As shown, macroscopic photographs and scanning electron microscope images of the alloy assemblies prepared by this process after oxidation at 730℃ for 100 hours show that the alloy oxidation is severe under conditions of large joint gaps.

[0069] Sampling was conducted on the oxidation-resistant GH4738 and GH3536 alloy assemblies prepared in this comparative example. Three parallel samples were collected and subjected to high-temperature oxidation at 730℃ for 100 hours. The oxidation rate was characterized by the weight gain of the samples during oxidation, which was 0.0759 g / (m³). 2 ·h), 0.0756g / (m 2 ·h), 0.0757g / (m 2 ·h).

[0070] The room temperature mechanical properties of the oxidation-resistant GH4738 and GH3536 alloy composites prepared in this comparative example are: room temperature shear strength of 298 MPa, 310 MPa, and 330 MPa; and high temperature mechanical properties: high temperature shear strength at 540℃ is 259 MPa, 278 MPa, and 298 MPa.

[0071] The oxidation rate of the assembly produced by the process described in this invention is only 0.0238 g / (m²). 2 (h) The oxidation rate of the assemblies prepared by the processes described in Comparative Examples 1 and 2 was significantly increased, indicating a substantial reduction in antioxidant capacity. It can be seen that the process described in this invention solves the problem of insufficient antioxidant performance in assemblies prepared by existing methods.

[0072] The above-mentioned solution proposes a vacuum brazing process to improve the oxidation resistance of GH4738 and GH3536 alloy assemblies, which can solve the technical problems existing in the prior art, such as the difference in oxidation capacity of dissimilar alloy brazing components, weak brazed joints, and short service life.

[0073] This invention uses two pretreatments of the base materials to make the surfaces of the two base alloys smooth, reduce roughness, and improve the fluidity of the brazing filler metal.

[0074] This invention creates steps in the assembly and fixing of components, especially by using an uneven overlapping method, which promotes the conversion of powdered brazing filler metal into paste-like brazing filler metal, improves the fluidity of the brazing filler metal, and makes the weld joint structure more complete. By using metal gaskets of different specifications to block the alloy, the gap of the brazed joint of the alloy assembly is strictly controlled. The process is simple, efficient, and accurate.

[0075] This invention, through the pre-placed brazing filler metal and flow retardant, enables the brazing filler metal to fill the welding gap of the fixed alloy component through capillary action during a short-time vacuum brazing process. Furthermore, the flow retardant ensures that the brazing filler metal does not overflow, reducing material waste and improving the yield.

[0076] This invention, through coordinated control of the type and amount of brazing filler metal, and simultaneous control of the gap size of the brazed joints of the two alloys, enables the alloy assembly to have unexpected effects in terms of oxidation resistance, thereby improving the service life of the assembly in high-temperature oxidizing environments.

[0077] This invention uses a nickel-based brazing filler metal with a melting point of 985-995℃, and selects matching brazing process parameters: brazing temperature of 1030-1040℃ and brazing holding time of 8-10 minutes, which fully comply with existing industrial settings, ensures the fluidity of the brazing filler metal, and improves the strength of the alloy brazed joint.

[0078] This invention uses strip-shaped brazing filler metal as an alloy spacer, which enables precise control of the gap between the brazed joints of the two base material alloys. Moreover, there is no need to remove the alloy spacer after assembly, thus optimizing the process steps and simplifying the operation. Its composition is also consistent with the subsequent paste-like brazing filler metal, ensuring the uniformity of the brazed joint.

[0079] The present invention has a complete process and high operating efficiency. While maintaining the mechanical properties of the alloy assembly joint, isothermal solidification is achieved by precisely controlling the gap of the brazed joint, which has an unexpected effect on improving the oxidation resistance of the assembly, enabling the alloy parts to reach the level of complete oxidation resistance, and improving the oxidation resistance by at least 1 time.

[0080] In summary, compared with traditional alloy component brazing methods, this invention obtains high-oxidation-resistant GH4738 and GH3536 alloy assembly products through two types of base material surface pretreatment, assembly and fixing of the assembly, pre-placed brazing filler metal + flow retardant setting, and vacuum brazing heat treatment. This method is stable, easy to implement, low in cost, and highly efficient, which is conducive to large-scale industrial production and widespread application.

[0081] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0082] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0083] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0084] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A vacuum brazing process to improve the oxidation resistance of a GH4738 and GH3536 alloy assembly, characterized in that, The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies includes the following steps: S1. Surface pretreatment of two base materials: First, the two base material alloys GH3536 and GH4738 are processed into the required size by wire cutting. Then, the welding surfaces of the two base material alloys are polished with sandpaper. After that, the surfaces of the two base materials are wiped with acetone to obtain two base material alloys with smooth surfaces and no impurities. S2. Assembly and fixing of the assembly: The two base alloys with smooth and impurity-free surfaces from S1 are overlapped in a staggered manner, with alloy spacers in the middle. Then, the assembly is fixed with a clamp, and finally, the base alloys are further fixed by spot welding to obtain a fixed assembly of the two base alloys. S3, Pre-set brazing filler metal + flow retardant setting: Apply the prepared paste brazing filler metal evenly to the gaps and non-overlapping areas of the fixed assembly of the two base alloys in S2, and apply a flow retardant to the outside of the mating surface of the fixed assembly of the two base alloys to prevent the brazing filler metal from overflowing during the brazing process, and obtain the assembled assembly. S4: Vacuum brazing heat treatment: The assembled components from S3 are placed in a vacuum brazing furnace for vacuum brazing heat treatment, followed by cooling to obtain oxidation-resistant GH4738 and GH3536 alloy assemblies.

2. The vacuum brazing process to improve the oxidation resistance of GH4738 and GH3536 alloy assemblies of claim 1, wherein, The two base alloys in S1 are wire-cut to a size of 100-120mm×11-14mm×5-7mm, of which 100-120mm×11-14mm is the welding surface.

3. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, In S1, the alloy surfaces to be welded need to be polished in sequence using 400#, 600#, 1000#, and 1500# sandpaper.

4. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, The surface roughness of the two base alloys in S1 after sanding is 0.05-0.1μm.

5. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, The overlap area of ​​the staggered overlap in S2 is 100-120mm×10mm, with a step left in the width direction.

6. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, The alloy gasket in S2 is a nickel-based alloy with a thickness of 30-40μm.

7. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, The process parameters for spot welding in S2 are as follows: welding current is 4.5-6.0kA, welding time is 0.02-0.5s, electrode pressure is 5-10kN, and electrode end diameter is 5-8mm.

8. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, The solder paste in S3 is a nickel-based solder BNi-2 with a melting point of 985-995℃. The amount of solder used should be controlled to cover the weld seam area and the non-overlapping platform area. The flow retardant is mainly composed of traditional metal oxides that form an outer film during the brazing process to prevent solder overflow. The flow retardant should be applied precisely and continuously to the boundary of the area to be protected, including the outer side of the mating surface of the fixed assembly. The amount required is to continuously cover the outer side by 0.05-0.1mm.

9. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, The vacuum brazing process in S4 is: placing the assembly at room temperature, drawing the vacuum in the furnace to 10 -3 Below Pa, the brazing furnace is heated to 700-900℃ at a rate of 5-15℃ / min, and the assembly is preheated for 20-30min; the brazing furnace is heated to 1030-1040℃ at a rate of 5-10℃ / min, and brazing is performed for 8-10min; after brazing, the furnace is filled with high-purity argon to accelerate cooling, and the furnace is discharged when it drops below 80℃, and the entire process is kept in a highly vacuum environment.

10. The vacuum brazing process for improving the oxidation resistance of GH4738 and GH3536 alloy assemblies according to claim 1, characterized in that, The sample of the GH4738 alloy assembly with the GH3536 alloy in S4 was subjected to high-temperature oxidation at 730 °C for 100 h. The oxidation rate was characterized by weighing the sample to count the weight gain of the sample. The oxidation rate was 0.0234 ± 0.0005 g / (m 2 ·h). h).

Images