High-temperature alloy diffusion welding method based on element diffusion regulation and control thought

Abstract

The invention relates to the technical field of heat exchanger equipment, in particular to a high-temperature alloy diffusion welding method based on an element diffusion regulation idea, which comprises the following steps: S1, surface pretreatment: mechanically polishing a high-temperature alloy sample, and then chemically cleaning to remove a surface oxide film and impurities; s2, a first middle layer is deposited through magnetron sputtering; s3, a plurality of middle layers are deposited through magnetron sputtering; and S4, the diffusion welding process is conducted, specifically, the assembled high-temperature alloy sample with the surface plated with the multiple middle layers is put into a vacuum furnace to be heated, and the finally-connected high-temperature alloy sample is obtained. According to the high-temperature alloy connection method, the magnetron sputtering technology and the diffusion welding technology are combined, formation of high-temperature alloy carbides is effectively prevented, the adverse effect of the carbides on high-temperature alloy connection is eliminated, and a connection joint good in structure and performance is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchanger equipment, and in particular to a high-temperature alloy diffusion welding method based on the concept of element diffusion control. Background Art

[0002] Diffusion-bonded microchannel heat exchangers (PCHEs) are one of the more commonly used heat exchangers. However, their application in fields such as nuclear power and aerospace, made from high-temperature alloys, still faces bottlenecks. This is manifested in the following: when direct diffusion welding is performed using high-temperature alloys, the joint interface often suffers from poor bonding due to carbide precipitation. The current traditional process, which adds an intermediate layer for welding, has shortcomings such as a narrow process window and weakened joint performance. Even after long welding periods, the uniformity of the elemental composition of the joint structure remains insufficient, the joint strength and toughness are mismatched, and the matrix grains coarsen. These phenomena significantly affect the application of diffusion welding methods in the field of microchannel heat exchangers.

[0003] Publication No. CN109396638B discloses a method for diffusion welding of aluminum alloys, comprising: magnetron sputtering chromium onto the surface of an aluminum alloy base material A to be welded, to obtain an aluminum alloy base material B; magnetron sputtering copper onto the surface of aluminum alloy base material B to be welded, to obtain an aluminum alloy base material C; placing a tin-lead alloy between two pieces of aluminum alloy base materials C to be welded, to obtain a welded assembly; and placing the assembly in a vacuum furnace for diffusion welding to obtain a welded joint. However, aluminum alloys differ significantly from high-temperature alloys, and this method cannot address the problem of poor joints caused by carbide precipitation during diffusion welding of high-temperature alloys, thereby failing to improve weld quality.

[0004] Therefore, a new high-temperature alloy diffusion welding method is urgently needed to solve the problem of poor bonding caused by carbide precipitation in high-temperature alloy diffusion welding. Summary of the Invention

[0005] In view of this, the present invention aims to propose a high-temperature alloy diffusion welding method based on the idea of element diffusion control, which solves the problem of poor joining caused by carbide precipitation in high-temperature alloy diffusion welding.

[0006] Printed Circuit Heat Exchangers (PCHEs) are compact, high-efficiency heat exchangers widely used in the petrochemical, aerospace, nuclear power, and other fields. In specialized service environments, such as high-temperature gas-cooled reactors, the heat exchangers must operate at temperatures up to 900°C, pressures up to 3 MPa, withstand cyclic thermal stresses, and exhibit high heat transfer performance. Furthermore, the heat exchanger must be compact. These requirements limit the use of compact, high-efficiency heat exchangers in such harsh operating conditions.

[0007] Since diffusion-bonded printed circuit board heat exchangers have excellent resistance to high temperatures and high pressures, the use of diffusion welding to manufacture high-temperature and high-pressure resistant printed circuit board heat exchangers can meet the requirements of harsh working conditions for compact and efficient heat exchangers. Solid-state diffusion welding is a welding method that brings the surfaces to be welded into contact with each other under a certain temperature and pressure, expands the physical contact of the surfaces to be welded through microscopic plastic deformation, and then heals the voids between the interfaces through atomic mutual diffusion to achieve bonding. This is mainly achieved by controlling process parameters such as welding temperature, diffusion time, and pressure. However, high-temperature alloys contain a large number of alloying elements, and precipitation phases are easily generated during diffusion welding, hindering interface bonding, resulting in poor welding performance. These are difficult to adjust using welding process parameters alone, and post-weld heat treatment is used to improve joint performance.

[0008] The present invention creatively uses a method based on element regulation to magnetron sputter five layers of intermediate layers on the surface of the component. By pre-treating the surface of the component before welding, the intermediate layer absorbs carbon elements during the welding process, preventing carbides from precipitating at the interface and forming holes, and supplementing strengthening elements and matrix elements, thereby improving joint performance while further promoting structural uniformity and achieving good welding of high-temperature alloys. Specifically, the intermediate layer is added layer by layer to the middle of the heat exchange plate by magnetron sputtering; the heat exchange plate with the added intermediate layer is then assembled in sequence and sent to the diffusion welding equipment; diffusion welding is performed at a certain temperature, pressure, and insulation time. By adding the intermediate layer, good welding of the high-temperature alloy diffusion welded joint is achieved, the welding effect is improved, and the problem of poor joint performance after existing high-temperature alloy diffusion welding is solved.

[0009] The technical solution of the present invention is achieved as follows:

[0010] The present invention discloses a high-temperature alloy diffusion welding method based on the concept of element diffusion control, comprising the following steps:

[0011] S1: Surface pretreatment: Mechanically polish the high-temperature alloy sample and then perform chemical cleaning to remove the surface oxide film and impurities;

[0012] S2: magnetron sputtering deposition of the first intermediate layer;

[0013] S3: magnetron sputtering deposition of multiple intermediate layers;

[0014] S4: Diffusion welding process: The assembled high-temperature alloy sample with multiple intermediate layers plated on the surface is placed in a vacuum furnace for heating to obtain the high-temperature alloy sample after final connection.

[0015] Furthermore, in step S1 , the high-temperature alloy is a Fe—Cr—Ni solid solution strengthened high-temperature alloy.

[0016] Furthermore, in step S1, metallographic sandpapers of different finenesses from 600# to 2000# are used for stepwise polishing, and the mesh size of the metallographic sandpaper is at least two or more of 600#, 800#, 1200#, 1500#, and 2000#.

[0017] Furthermore, in step S2, the vacuum degree of the magnetron sputtering equipment is 1×10 -3 Pa to 1×10 -2 Between Pa.

[0018] Furthermore, in step S2, the intermediate layer is a pure Ni or pure Cr layer.

[0019] Furthermore, in steps S2 and S3 , the thickness of the intermediate layer ranges from 1 μm to 20 μm.

[0020] Furthermore, in step S3, the middle layer is a pure Ni layer, which can undergo a diffusion reaction with the Ni element to form a good joint.

[0021] Furthermore, in step S3, five intermediate layers are provided.

[0022] Further, in step S4, the temperature is increased at a rate of 5°C to 10°C / min to the connection temperature, and kept at this temperature for 60 minutes to 180 minutes. The connection temperature range is 1100°C to 1250°C. Thereafter, the temperature is reduced to 400°C at a rate of 1°C to 5°C / min, and then cooled with the furnace.

[0023] Compared with the prior art, the high-temperature alloy diffusion welding method of the present invention based on the concept of element diffusion control has the following advantages:

[0024] 1. The high-temperature alloy connection method provided by the present invention combines magnetron sputtering technology with diffusion welding technology, effectively preventing the formation of high-temperature alloy carbides, eliminating the adverse effects of carbides on high-temperature alloy connections, and obtaining connection joints with good organization and performance.

[0025] 2. The high-temperature alloy surface activation connection method provided by the present invention uses magnetron sputtering technology to obtain a dense intermediate layer, and the intermediate layer and the high-temperature alloy substrate are tightly bonded without defects, eliminating the adverse effects of defects between the intermediate layer and the substrate on the connection of the high-temperature alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 This is a schematic diagram of a joint according to Example 1 of the present invention;

[0028] Figure 2 This is a schematic diagram of the joint of Example 2 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the technical means, objectives and effects of the present invention easier to understand, embodiments of the present invention are described in detail below with reference to specific figures.

[0030] It should be noted that all terms used in the present invention to indicate direction and position, such as "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "low", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection status between various components in a specific state. They are only for the convenience of describing the present invention, and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0031] In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical connections; direct connections or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0032] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0033] The present invention discloses a high-temperature alloy diffusion welding method based on the concept of element diffusion control, which includes the following specific steps:

[0034] S1: surface pretreatment;

[0035] First, the high-temperature alloy sample is mechanically polished using metallographic sandpaper of different finenesses from 600# to 2000# to remove the surface roughness layer and possible contaminants, providing a smooth and uniform foundation for subsequent magnetron sputtering deposition. Then, chemical cleaning is performed to remove the surface oxide film and impurities, and alcohol solution is used to clean the surface in turn to ensure that the surface is clean and pollution-free. After cleaning, rinse with deionized water, wipe with acetone, and finally blow dry to ensure that there is no residual moisture and organic matter on the surface, which is conducive to improving the adhesion effect of the intermediate layer.

[0036] This step aims to remove the oxide film and impurities on the surface of the high-temperature alloy through mechanical grinding and chemical cleaning, ensuring the cleanliness of the welding surface, helping to enhance the bonding strength between the intermediate layer and the base material, avoiding interface defects caused by surface contaminants, and thus improving the quality of the final weld joint.

[0037] S2: magnetron sputtering deposition of the first intermediate layer;

[0038] The treated high-temperature alloy sample is placed in the magnetron sputtering equipment and vacuumed to ensure the purity of the deposition process and reduce the impact of impurities in the air on the deposited layer. Magnetron sputtering technology is used to deposit a layer on the surface of the high-temperature alloy sample as an intermediate layer to block the migration of carbon elements to the welding interface and prevent the formation of carbides. At the same time, it promotes the diffusion and uniform distribution of elements during the welding process. The thickness can be adjusted according to specific needs to achieve the best welding effect.

[0039] S3: magnetron sputtering deposition of multiple intermediate layers;

[0040] The high-temperature alloy sample after the above treatment continues to be kept in the magnetron sputtering equipment, the target material is replaced, and the magnetron sputtering technology is used again to deposit an additional intermediate layer on the surface of the high-temperature alloy, and finally a high-temperature alloy sample with a multi-layer coating structure is formed.

[0041] Continue to add other types of intermediate layers to form a multi-layer structure. Each layer may have different functions, such as further optimizing element diffusion, increasing the toughness and strength of the weld joint, etc. Different target materials are selected according to needs to form a multi-layer coating structure with specific composition on the surface of the high-temperature alloy. The design of the multi-layer intermediate layer can better adapt to different welding requirements. By adjusting the composition and thickness of each layer, the optimal control of the welding performance can be achieved, and the comprehensive performance of the weld joint can be significantly improved.

[0042] S4: diffusion welding process;

[0043] The assembled high-temperature alloy sample with multiple intermediate layers on the surface is placed in a vacuum furnace and heated under vacuum. It is heated to the connection temperature at a heating rate of 5°C to 10°C / min and kept at this temperature for 60 minutes to 180 minutes to ensure sufficient diffusion. After that, it is cooled to 400°C at a cooling rate of 1°C to 5°C / min and then cooled with the furnace. This can avoid thermal stress damage caused by rapid cooling and obtain the final connected high-temperature alloy sample.

[0044] This setup solves problems associated with traditional processes, such as poor joint performance and a narrow process window. It also improves the mechanical properties and durability of welded joints by optimizing process parameters. Furthermore, the entire process is performed in a strict vacuum environment, minimizing interference from external impurities and ensuring weld quality.

[0045] Specifically, in step S1 , the high-temperature alloy is a Fe—Cr—Ni solid solution strengthened high-temperature alloy.

[0046] Fe-Cr-Ni high-temperature alloys form a solid solution in the iron matrix by adding elements such as Cr and Ni. This solid solution can significantly improve the strength and corrosion resistance of the material. The Cr element enhances the oxidation resistance and corrosion resistance of the alloy, while Ni helps to maintain the structural stability of the alloy at high temperatures. In addition, Fe-Cr-Ni high-temperature alloys have good processing properties, which facilitates pre-treatment steps such as mechanical polishing and chemical cleaning, ensuring a good bonding interface during the subsequent magnetron sputtering deposition of the intermediate layer.

[0047] After surface pretreatment, this setting can be more effectively combined with the intermediate layer material, thereby improving the overall performance of the final weld joint, and can give full play to the excellent physical and chemical properties of the material itself, and further improve the performance of the weld joint through the diffusion welding method provided by the present invention.

[0048] Specifically, in step S1, the mesh size of the metallographic sandpaper may be at least two of 600#, 800#, 1200#, 1500#, and 2000#.

[0049] Gradually grinding from sandpaper with lower mesh count, such as 600#, to higher mesh count, such as 2000#, can effectively remove the oxide layer, impurities and other contaminants on the surface of the high-temperature alloy, and gradually refine the surface roughness, providing a good foundation for subsequent chemical cleaning and magnetron sputtering deposition. By using a variety of sandpapers with different finenesses for grinding, the flatness of the material surface can be significantly improved, ensuring that the intermediate layer can be deposited on the surface as evenly and flat as possible, thereby enhancing the bonding strength between the intermediate layer and the substrate, and helping to eliminate surface defects that may affect welding quality, such as tiny cracks or pits.

[0050] This multi-stage grinding setting can make the surface of the high-temperature alloy smoother and flatter, which is conducive to the close fitting of the subsequent intermediate layer, increases the bonding force between the intermediate layer and the substrate, and thus improves the overall performance of the weld joint, helps to obtain a more uniform and dense intermediate layer coating, and avoids the problem of uneven coating thickness or poor adhesion due to the uneven surface of the substrate.

[0051] Specifically, in step S2, the vacuum degree of the magnetron sputtering equipment is 1×10 -3 Pa to 1×10 -2 Between Pa.

[0052] A high vacuum environment can effectively reduce the chance of oxygen, moisture, and other possible impurity gases in the air reacting with the target or substrate material, ensuring that the deposition process is carried out in a relatively pure environment. Under lower gas pressure, particles in the plasma (such as argon ions) can more efficiently impact the target, causing the atoms / molecules sputtered from the target to have higher energy, thereby helping to form a denser, more uniform, and more strongly adherent thin film layer. Appropriate vacuum levels help maintain a stable plasma state, which is crucial for precisely controlling the thickness and composition of the film layer, ensuring consistent quality of the intermediate layer produced in each batch.

[0053] This setting can significantly improve the key performance indicators of the final product, such as corrosion resistance, mechanical strength and thermal stability, by preparing the intermediate layer under strict vacuum conditions, meeting the stringent requirements of high-end application fields for material performance.

[0054] Specifically, in step S2 , the intermediate layer may be a pure Ni or pure Cr layer.

[0055] High-temperature alloys are prone to poor bonding due to the precipitation of carbides during welding. Using pure Ni or pure Cr as an intermediate layer can absorb carbon during welding, preventing carbides from forming holes at the interface, thereby improving the bonding quality. Ni and Cr are both elements with good diffusivity. They can diffuse with other elements in high-temperature alloys, which helps to improve the uniformity and stability of the weld joint.

[0056] This setting solves the problem of carbide precipitation existing in traditional welding methods, and greatly improves the quality and reliability of high-temperature alloy diffusion welding by optimizing element diffusion and enhancing joint performance.

[0057] Specifically, the thickness of the intermediate layer ranges from 1 μm to 20 μm.

[0058] An appropriate interlayer thickness ensures effective carbon absorption during welding, preventing carbide precipitation and pore formation at the interface. If it's too thin, it may not effectively block carbon diffusion; while too thick may lead to unnecessary material waste and increased costs. This helps ensure effective element diffusion during welding and uniform joint structure. The interlayer acts as a bridge between the base alloy and the weld material, promoting atomic interdiffusion, thereby improving the quality of the weld joint and reducing poor bonding or stress concentration issues caused by inappropriate thickness.

[0059] This setting can significantly improve the mechanical properties and durability of the welded joint, reduce poor joining caused by carbide precipitation or other defects, and thus obtain high-quality welded joints.

[0060] Specifically, in step S3, the intermediate layer may be a pure Ni layer, which can undergo a diffusion reaction with the Ni element to form a good joint.

[0061] Nickel (Ni) is an element with excellent diffusion properties. When pure Ni is used as an intermediate layer, during the welding process, Ni atoms can effectively diffuse with other elements in the high-temperature alloy, thereby promoting atomic-level bonding at the interface, helping to absorb carbon elements that may migrate to the weld interface, and preventing carbides from precipitating at the interface to form holes or defects. This can significantly improve the quality of the weld joint. Through the diffusion of Ni, not only can the overall uniformity of the weld joint be improved, but the mechanical properties of the joint area, including tensile strength and fatigue strength, can also be enhanced, making the weld joint more solid and reliable.

[0062] This setting significantly improves the quality of welded joints, reduces the risk of welding failure due to interface defects, and achieves high-strength and high-stability connections.

[0063] Specifically, in step S3, five intermediate layers are set.

[0064] Compared with a single layer or multiple layers with fewer layers, the five-layer structure can more finely control the microstructure and mechanical properties of the welded joint, significantly improve the overall quality and reliability of the joint, enhance the initial strength and toughness of the welded joint, and improve its stability and durability in long-term use, especially under extreme working conditions (such as high temperature and high pressure).

[0065] Specifically, in step S4, the heating temperature range is 1100°C to 1250°C.

[0066] Within this temperature range, atoms in the superalloy gain sufficient energy to migrate, enabling effective diffusion between the matrix and the interlayer. This diffusion helps eliminate interfacial voids, forming a continuous, uniform interface. This prevents undesirable phase transformations or the formation of brittle phases (such as carbides) during welding, which could weaken the performance of the welded joint. This ensures the material's excellent plastic deformation capacity without excessive grain growth, thereby maintaining the material's microstructural stability and mechanical properties.

[0067] This setting can obtain high-quality weld joints by controlling the heating temperature between 1100℃ and 1250℃, reducing problems such as insufficient diffusion caused by too low temperature or structural degradation caused by too high temperature, making the element distribution in the weld joint area more uniform, which not only enhances the overall strength of the joint, but also improves its toughness and durability.

[0068] Example 1

[0069] 1) First, polish the high-temperature alloy with 600#, 800#, 1200#, 1500#, and 2000# metallographic sandpaper in sequence, use chemical and alcohol solutions for chemical cleaning, then rinse with deionized water, and finally wipe with acetone and blow dry;

[0070] 2) placing the treated high-temperature alloy sample into an electroplating device, and depositing an intermediate layer on the surface of the high-temperature alloy using electroplating technology to obtain a high-temperature alloy sample with a plated surface;

[0071] 3) Place the surface-coated high-temperature alloy sample assembly into a vacuum furnace and place it in a vacuum state (vacuum degree of 5×10 - 3 Pa), heated to the joining temperature at a heating rate of 5°C to 10°C / min and kept at that temperature for 60min to 180min, then cooled to 100°C at a rate of 1°C to 5°C / min and then cooled in the furnace to obtain the joined high-temperature alloy specimens.

[0072] Example 2

[0073] Step 1: First, mechanically polish and chemically clean the high-temperature alloy to remove the surface oxide film and impurities, then rinse with deionized water, and finally wipe with acetone and blow dry;

[0074] Step 2: Place the high-temperature alloy sample processed in step 1 into the magnetron sputtering equipment and evacuate the vacuum to a range of 1×10 -3 Pa~1×10 -2Pa, using magnetron sputtering technology to deposit an intermediate layer on the surface of the high-temperature alloy to obtain a high-temperature alloy sample with a surface coating, wherein the intermediate layer is a pure Ni layer or a pure Cr layer, and the thickness of the intermediate layer is 1 μm to 20 μm;

[0075] Step 3: Place the high-temperature alloy sample processed in step 2 into the magnetron sputtering equipment and evacuate it, replace the target material, and use magnetron sputtering technology to deposit an intermediate layer on the surface of the high-temperature alloy to obtain a high-temperature alloy sample with a multi-layer coating on the surface;

[0076] Step 4: Assemble the surface-plated high-temperature alloy sample, then place it in a vacuum furnace, heat it to the connection temperature at a heating rate of 5°C to 10°C / min under vacuum and keep it warm for 60min to 180min. The connection temperature is 1100°C to 1250°C, then cool it to 400°C at a rate of 1°C to 5°C / min and cool it with the furnace to obtain the connected high-temperature alloy sample.

[0077] The above are only preferred embodiments 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 should be included in the scope of protection of the present invention.

Claims

1. A high-temperature alloy diffusion welding method based on the concept of element diffusion control, characterized in that: The following steps are involved: S1: Surface pretreatment: Mechanically polish the high-temperature alloy sample and then perform chemical cleaning to remove the surface oxide film and impurities; S2: magnetron sputtering deposition of the first intermediate layer; S3: magnetron sputtering deposition of multiple intermediate layers; S4: Diffusion welding process: The assembled high-temperature alloy sample with multiple intermediate layers plated on the surface is placed in a vacuum furnace for heating to obtain the high-temperature alloy sample after final connection.

2. The high-temperature alloy diffusion welding method based on the element diffusion control concept according to claim 1 is characterized in that: In step S1 , the high-temperature alloy is a Fe—Cr—Ni solid solution strengthened high-temperature alloy.

3. The high-temperature alloy diffusion welding method based on the concept of element diffusion control according to claim 1 is characterized in that: In step S1, metallographic sandpapers of different finenesses from 600# to 2000# are used for stepwise polishing, and the mesh size of the metallographic sandpaper is at least two or more of 600#, 800#, 1200#, 1500#, and 2000#.

4. The high-temperature alloy diffusion welding method based on the element diffusion control concept according to claim 1 is characterized in that: In step S2, the vacuum degree of the magnetron sputtering equipment is 1×10 -3 Pa to 1×10 -2 Between Pa.

5. The high-temperature alloy diffusion welding method based on the concept of element diffusion control according to claim 1 is characterized in that: In step S2 , the intermediate layer is a pure Ni or pure Cr layer.

6. The high-temperature alloy diffusion welding method based on the element diffusion control concept according to claim 1 is characterized in that: In steps S2 and S3 , the thickness of the intermediate layer ranges from 1 μm to 20 μm.

7. The high-temperature alloy diffusion welding method based on the element diffusion control concept according to claim 6 is characterized in that: In step S3, the middle layer is a pure Ni layer, which can undergo diffusion reaction with the Ni element to form a good joint.

8. The high-temperature alloy diffusion welding method based on the element diffusion control concept according to claim 7 is characterized in that: In step S3, five intermediate layers are provided.

9. The high-temperature alloy diffusion welding method based on the element diffusion control concept and the preparation method thereof according to claim 1, characterized in that: In step S4, the material is heated to the connection temperature at a heating rate of 5°C to 10°C / min and kept at this temperature for 60 minutes to 180 minutes. The connection temperature range is 1100°C to 1250°C. After that, the material is cooled to 400°C at a cooling rate of 1°C to 5°C / min and then cooled in the furnace.

Images