Welding method for metal part to be welded and large-size tungsten / copper component

Abstract

The invention discloses a metal to-be-welded part which comprises a first metal matrix, a permeation layer and a middle layer, and nano-porous structures are distributed on the surface of the first metal matrix; the second metal is infiltrated and distributed on the surface layer of the first metal matrix, and the nano-porous structure is filled with the second metal to form an infiltrated layer; second metal is deposited on the surface of the infiltrated layer to form an intermediate layer; wherein the first metal is an indissolvable metal, and the first metal and the second metal are not subjected to solid solution. The invention further discloses a preparation method and application of the metal part to be welded. The invention further discloses a welding method of the large-size tungsten / copper component, which comprises the following steps that the tungsten to-be-welded piece and the copper are subjected to diffusion welding to obtain the large-size tungsten / copper welding component, the tungsten to-be-welded piece is the metal to-be-welded piece, the first metal is tungsten, and the second metal is copper. By means of the specific structure of the to-be-welded part, welding of insoluble metal and non-solid-soluble metal of a large-size or complex-shape component can be achieved, and the method is environmentally friendly, safe, easy to operate and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of refractory metal welding, and in particular to a metal welded part, a large-size tungsten / copper component welding method. Background Art

[0002] Fusion energy has become an ideal energy source for human society in the future due to its abundant resources and near-zero pollution. It is one of the most promising fundamental solutions to completely solve the energy problem and has important strategic significance for the sustainable development of my country's economy and society. Plasma components are key components in magnetic confinement fusion devices.

[0003] Tungsten (W) is a rare high-melting-point metal (3683K) with relatively stable chemical properties, high thermal conductivity, high sputtering threshold and low tritium retention. Therefore, it is identified as one of the preferred materials for plasma-facing materials (PFMs). However, due to the poor thermal conductivity of W, W needs to be connected to a cooling system consisting of a heat sink material to quickly transfer a large amount of heat on its surface during service to maintain its service life. Copper-based alloys (such as CuCrZr) have become the first choice for heat sink materials in plasma-facing components due to their excellent thermal conductivity and high-temperature strength. However, W and Cu do not dissolve in each other and are difficult to alloy directly, and they have different melting points and thermal expansion coefficients (α Cu ≈4α W ) and Young's modulus (E Cu ≈0.2E W ) and other physical properties. Therefore, the connection problem of W / Cu, which are immiscible materials, has always been a technical bottleneck. The shear strength of W / Cu components welded by existing processes is about 150MPa, and the connection of large-size W / Cu is even more challenging, with lower shear strength.

[0004] Explosive welding, hot isostatic pressing and vacuum diffusion welding are all suitable for connecting large-sized materials. However, since W is a typical brittle metal, explosive welding may cause W to break, and there are usually restrictions on the thickness of W. In addition, explosive welding will also produce considerable residual stress in the parent material, resulting in a decrease in the high temperature or fatigue strength of the W / Cu layered composite material or connector. In comparison, hot isostatic pressing and vacuum diffusion welding are more suitable methods, and both have been applied in engineering. These two methods usually use an intermediate layer to achieve W / Cu alloy connection (such as Ni, Ti, Cu, W-Fe, etc.), but the intermediate layer composed of non-Cu elements will destroy the consistency of the overall connector composition and reduce its thermal conductivity.

[0005] Direct diffusion bonding of W / Cu components must first solve the problem of interface metallurgical bonding. Currently, there are mainly the following technical approaches: (1) Using the high-temperature structure of low-melting-point Cu in the W / Cu system to induce mutually immiscible metal alloying to form a metallurgical bonding interface; (2) Using the radiation damage structure produced by ion implantation to provide a channel for atomic mutual diffusion, and using the high-energy atoms around the defects to provide a thermodynamic driving force for diffusion; (3) Through physical vapor deposition of W / Cu multilayer films, W and Cu are chemically mixed to achieve a diffusion effect and realize metallurgical bonding; (4) Using the effect of mechanical energy to cause diffusion and solid-state reaction between W / Cu powders to achieve metallurgical bonding at room temperature; (5) Mixing alloying of mutually immiscible metal ions and solid-state reaction amorphization, etc.

[0006] In general, the above methods can overcome the mutual imsolubility between W and Cu, realize the mutual diffusion between the two atoms, establish a metallurgical bonding interface, and realize alloying. However, the above methods have their own applicability. Among them, high temperature structure induces alloying, and the process window is small (0.90-0.97T m , T m is the melting point of Cu); irradiation damage alloying, the modified layer of traditional ion implantation technology is relatively thin (the layer thickness is only nanometer scale), so the diffusion layer thickness is also small, and this technology is not suitable for the preparation of large-sized or bulk material alloys; mechanical alloying, serious material deformation, affecting the manufacturing accuracy of components; physical vapor deposition and ion beam mixing are not suitable for the preparation of large-sized or bulk material alloys. Summary of the invention

[0007] Based on the technical problems existing in the background technology, the present invention proposes a metal part to be welded, a large-size tungsten / copper component welding method. The surface of the refractory metal matrix of the present invention is distributed with a nanoporous structure, a diffusion layer and an intermediate layer to form the part to be welded. Its specific structure can realize the welding of refractory metals of large-size components or components with complex shapes and their mutually immiscible metals, thereby improving the bonding strength. The shear strength of the W / Cu welded parts reaches 236MPa. The preparation process does not involve the use of corrosive / hazardous chemicals, is environmentally friendly and safe, and is simple to operate and low in cost.

[0008] The present invention proposes a metal welded part, comprising: a first metal substrate, a diffusion layer and an intermediate layer, wherein a nanoporous structure is distributed on the surface of the first metal substrate; a second metal is infiltrated and distributed on the surface of the first metal substrate, and the nanoporous structure is filled with the second metal to form a diffusion layer; the second metal is deposited on the surface of the diffusion layer to form an intermediate layer; wherein the first metal is a sparingly soluble metal, and the first metal and the second metal are not mutually soluble.

[0009] Preferably, the volume of the metal to be welded is ≥1m 3 .

[0010] The shape of the metal workpiece to be welded is not limited, and may be block-shaped, circular, irregular, etc.

[0011] Preferably, the nanopore size of the nanoporous structure is 10-200 nm, more preferably 50-150 nm.

[0012] Preferably, the penetration depth of the diffusion layer is 0.1-10 μm.

[0013] Preferably, the thickness of the intermediate layer is 0.1-10 μm.

[0014] Preferably, the first metal is tungsten or a tungsten alloy.

[0015] When the first metal is tungsten, its purity is greater than 99.9wt%; when the first metal is a tungsten alloy, the tungsten content is ≥85wt%, more preferably ≥95wt%.

[0016] Preferably, the second metal is one of copper and copper alloy; when the second metal is copper alloy, the copper content is ≥97wt%.

[0017] Preferably, a hollow cathode is used for plasma beam irradiation to form the nanoporous structure, the diffusion layer and the intermediate layer.

[0018] Preferably, the cathode material in the hollow cathode is a second metal.

[0019] Preferably, the cathode in the hollow cathode is a mesh cathode.

[0020] Preferably, the mesh size of the mesh cathode is 0.1-1 cm.

[0021] The shape of the mesh cathode is not limited. It can be a hollow cathode with a mesh outer wall, such as a hollow cylinder, a hollow square column, a hollow sphere, a hollow ellipsoid, a hollow irregular shape, etc.; it can also be a mesh plate, etc. The shape of the mesh cathode can be designed according to the structure of the workpiece to be processed.

[0022] Preferably, a nanoporous structure is formed on the surface of the first metal substrate by He plasma beam irradiation.

[0023] Preferably, the diffusion layer and the intermediate layer are formed by plasma beam irradiation of the second metal.

[0024] The present invention forms nanometer-scale bubbles on the surface of the first metal substrate by irradiating the He plasma beam, and then the bubbles burst to form a nanoporous structure with regular morphology and adjustable pore size. A large amount of energy is stored in the nanoporous structure, and a large number of non-equilibrium structures such as grain boundaries, dislocations, subgrain boundaries, and vacancies exist. When the second metal plasma beam is irradiated to form a permeation layer, more driving force and channels can be provided for the diffusion of the second metal atoms, the surface energy of the first metal substrate is increased, the second metal atoms are promoted to diffuse and penetrate in the first metal substrate to form a permeation layer, and a mechanical locking effect is generated on the permeation layer, and then an intermediate layer is formed to obtain the welded part.

[0025] The welded parts with this structure can be used for welding between a first metal that is difficult to dissolve and a second metal that is immiscible with each other, thereby achieving tight welding of the first metal and the second metal and improving the bonding strength of the two after welding.

[0026] When treating metal by conventional hollow cathode discharge irradiation, the metal needs to be placed in the cathode of the hollow cathode. Since the cathode discharge space of the conventional hollow cathode is limited (taking round block-shaped metal parts as an example, the conventional hollow cathode can generally only treat metal parts with a diameter of ≤100 mm), and when the cathode size of the conventional hollow cathode is too large, plasma can only be generated at the edge of the cathode, making it difficult to treat workpieces of large size or complex structure; and the working gas pressure of the conventional hollow cathode is relatively high (50-200 Pa), resulting in a very short particle free path and uneven plasma distribution, resulting in uneven metal surface treatment, and the inability to achieve welding of refractory metals and mutually immiscible metals. The cathode in the hollow cathode of the present invention is designed to be mesh-shaped. Under relatively low pressure conditions, the He plasma beam can form a nanoporous structure on the surface of the first metal (i.e., the insoluble metal), thereby reducing energy consumption. When the mesh cathode is large in size, its mesh structure can generate uniform plasma inside the cathode, which is suitable for workpieces of large size or complex structure. The cathode material in the hollow cathode is selected as the second metal. By adjusting the parameters and using the same hollow cathode, the nanoporous structure, the diffusion layer and the intermediate layer can be continuously formed, thereby greatly reducing the difficulty of production and simplifying the operation. The use of the hollow cathode of the present invention can increase the thickness of the diffusion layer and improve the bonding strength between the first metal and the second metal.

[0027] The present invention also proposes a method for preparing the above-mentioned metal welded part, comprising the following steps:

[0028] S1. In an argon and helium atmosphere, a plasma beam of Ar and He is formed by a hollow cathode to bombard the surface of the first metal substrate, thereby forming a nanoporous structure on the surface of the first metal substrate;

[0029] S2, in an argon atmosphere, using a hollow cathode to form a plasma beam of a second metal to bombard the surface of the first metal substrate to form a diffusion layer;

[0030] S3, in an argon atmosphere, using a hollow cathode to form a plasma beam of the second metal to bombard the infiltrated layer to form an intermediate layer, thereby obtaining a metal to be welded;

[0031] The cathode material in the hollow cathode is a second metal, and the cathode in the hollow cathode is a mesh cathode.

[0032] After the first metal substrate is cleaned, the treatment in step S1 is performed; the first metal substrate can be made by powder metallurgy.

[0033] Preferably, in S1, in the plasma beam, the density of the plasma is 10 19 -10 26 ion / (m 2 ·s).

[0034] Preferably, in S1, the volume ratio of argon to helium is 1-5:1; more preferably 3:1.

[0035] Preferably, in S1, the pulse width of the hollow cathode is 5-30 μs, more preferably 15 μs.

[0036] Preferably, in S1, the voltage of the hollow cathode is -600 to -2000V; more preferably, -800 to -1200V.

[0037] Preferably, in S1, the first metal substrate serves as the second cathode, and its bias voltage is -50 to -600V.

[0038] Preferably, in S1, the pressure of the argon and helium atmospheres is 1-10 Pa; more preferably, 5 Pa.

[0039] In the above S1, the He ion energy is regulated by adjusting the bias voltage of the second cathode, and the beam current of the plasma beam is regulated by the plasma density.

[0040] Preferably, in S1, the surface of the first metal substrate is first cleaned by forming an Ar plasma beam with a hollow cathode in an argon atmosphere, and then the surface of the first metal substrate is irradiated and bombarded by forming an Ar and He plasma beam with a hollow cathode in an argon and helium atmosphere.

[0041] Taking the first metal substrate as tungsten substrate and the second metal as copper as an example, the cathode in the hollow cathode of the present invention is designed as a copper mesh hollow cathode, and by adjusting the experimental steps and parameters for many times, it is unexpectedly found that in argon and helium atmospheres, the copper mesh hollow cathode can realize the decoupling regulation of gas and Cu plasma, and only Ar and He plasma beams are formed under suitable conditions, but no Cu plasma is formed, thereby realizing that only the copper mesh hollow cathode can continuously form a nanoporous structure, a copper infiltration layer and a copper intermediate layer on the surface of the tungsten substrate, greatly reducing the difficulty of preparation, completing the preparation of the welded parts at one time, with simple operation, low energy consumption and no pollution; and the nanoporous structure can be evenly distributed, the thickness of the infiltration layer is as high as micron level, and the intermediate layer is uniform and flat, which can greatly improve the bonding strength during tungsten-copper welding, especially for large-sized or complex-structured components, and has a good welding effect; the shear strength of large-sized tungsten / copper welded components reaches 236MPa.

[0042] Preferably, in S2, the voltage of the hollow cathode is -500 to -1200 V, and the pulse width of the hollow cathode is 50-90 μs.

[0043] Preferably, in S2, the first metal substrate serves as the second cathode, and its bias voltage is 0 to -1000V.

[0044] Preferably, in S3, the voltage of the hollow cathode is -500 to -1200 V, and the pulse width of the hollow cathode is 100-210 μs.

[0045] Preferably, in S3, the first metal substrate serves as the second cathode, and its bias voltage is 0 to -600V.

[0046] Preferably, in S2, the temperature of the first metal substrate is 800-1200°C.

[0047] Preferably, in S2, in an argon atmosphere, a hollow cathode is used to form an Ar plasma beam to irradiate and bombard the surface of the first metal substrate, so that the first metal substrate is heated to 800-1200°C, and then a second metal plasma beam is formed to irradiate and bombard the surface of the first metal substrate to form a diffusion layer.

[0048] The present invention also proposes the use of the above-mentioned metal weldment in welding a first metal and a second metal, wherein the first metal is a refractory metal, and the first metal and the second metal are not soluble in each other.

[0049] Preferably, it is used in welding the first metal and the second metal of large-sized components or components with complex shapes.

[0050] The present invention also proposes a large-size tungsten / copper component welding method, comprising the following steps: taking a tungsten workpiece to be welded and copper for diffusion welding to obtain a large-size tungsten / copper welding component, wherein the tungsten workpiece to be welded is such as the above-mentioned metal workpiece to be welded, the first metal is one of tungsten and a tungsten alloy, and the second metal is one of copper and a copper alloy.

[0051] Preferably, the diffusion welding is vacuum diffusion welding.

[0052] Preferably, the diffusion welding procedure is: heating to 450-550°C, adjusting the pressure to 40-60MPa, and keeping warm for 0.5-1h; then heating to 600-750°C, adjusting the pressure to 20-40MPa, and keeping warm for 0.5-1.5h.

[0053] The above diffusion welding is performed in a diffusion welding device.

[0054] In the above diffusion welding procedure, the temperature is raised to 450-550°C at a rate of 8-12°C / min.

[0055] After the above diffusion welding is completed, the temperature is lowered to 100-200°C at a rate of 8-12°C / min, and then cooled along with the equipment.

[0056] The shape of the tungsten welded parts is not limited, and can be block, round, irregular, etc.; the tungsten welded parts are large-sized welded parts, and their volume can be ≥1m 3 .

[0057] Taking a round block as an example, its diameter can be ≥1m; taking a square block as an example, its side length can be ≥1m; taking an irregular shape as an example, its volume can be ≥1m 3 .

[0058] In traditional methods, femtosecond laser etching and anodization can be used to prepare nanostructures on the W surface. However, the femtosecond laser method is not suitable for large-sized materials, and the technology is limited by the shape of the sample. For example, it is impossible to prepare nanostructures on the inner surface and curved surface; reduction and deoxidation treatment is required after anodization, otherwise the oxide layer will easily make the metal microstructure loose or even cause metal embrittlement and failure, and anodization generally uses corrosive chemicals, which has an impact on the environment. The working gas pressure of the existing hollow cathode discharge irradiation method is relatively high, resulting in a very short particle free path, uneven plasma distribution, and limited discharge space, making it difficult to process large-sized or complex-structured workpieces.

[0059] In view of the above problems, the present invention uses a copper mesh hollow cathode, the size of the copper mesh can be adjusted according to the size of the component, and the gas and metal plasma can be decoupled and regulated, so that not only can a uniform nanopore structure be prepared on the tungsten surface by He plasma, the surface energy of the tungsten block is improved, and the copper infiltration layer is promoted and mechanically locked, but also a copper infiltration layer and a copper intermediate layer can be prepared on the tungsten surface by Cu plasma. The copper mesh hollow cathode has stable discharge, is non-toxic and pollution-free, the obtained copper infiltration layer reaches the micron level, and the copper intermediate layer is uniform and flat, which is suitable for tungsten / copper welding of large-sized components or components with complex structures.

[0060] Compared with traditional methods, the present invention is suitable for surface treatment of large-sized or complex-shaped metal components and welding of the inner surface of workpieces based on copper mesh hollow cathode plasma treatment. It is easy to operate, has good repeatability, low production cost, and wide applicability. It breaks through the limitations of traditional methods of welding tungsten / copper and is conducive to the industrial application of tungsten / copper components. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 The cross-sectional morphology and cross-sectional EDS line scan results of a large-sized tungsten / copper welded component, where a is the cross-sectional morphology and b is the cross-sectional EDS line scan result. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is described in detail below through specific embodiments.

[0063] Example 1

[0064] A method for preparing a large-size tungsten welded part comprises the following steps:

[0065] S1, after powder metallurgy, a round tungsten block with a purity of 99.96wt% (with a size of ), vacuum annealed at 1000℃ for 2h to eliminate residual stress and surface defects after processing; then polished with 400#, 800#, 1000# and 1200# metallographic sandpaper in turn, and then polished with 0.3μm diamond polishing agent, and then ultrasonically cleaned in acetone, isopropanol and methanol to remove oil, and then ultrasonically cleaned in anhydrous ethanol and ultrapure water, and then placed in a vacuum chamber with a vacuum degree of 10 -2 Pa, dried in a vacuum drying oven at 30°C;

[0066] Take a hollow cathode device (the cathode in the hollow cathode is a copper mesh hollow cylinder, the diameter of the cylinder bottom is 1100 mm, the height is 10 mm, the mesh aperture is 0.2 cm, and the cathode in the hollow cathode is in a vacuum environment), then put a tungsten block into the copper mesh hollow cylindrical cathode, and use the tungsten block as the second cathode, pass argon gas, adjust the first cathode pulse voltage to -1000 V, the pulse width to 15 μs, the frequency to 600 Hz, and the second cathode bias to -500 V, generate an Ar plasma beam to perform Ar plasma cleaning on the copper mesh and tungsten block surfaces for 2 hours;

[0067] Then helium was gradually introduced into the vacuum chamber to make the volume ratio of argon and helium 3:1, the pressure of argon and helium atmosphere was adjusted to 5 Pa, the pulse width of the hollow cathode was 15 μs, the frequency was 600 Hz, the voltage of the hollow cathode was -1000 V, and the bias voltage of the second cathode tungsten block was -500 V, forming a plasma beam of Ar and He (the density of the plasma was 10 19 -10 26 ion / (m 2 ·s)) bombards the surface of the tungsten block for 0.5h, so that He migrates in the tungsten block to form helium bubbles, and finally forms a nanoporous structure on the surface of the tungsten block. The nanoporous structure is evenly distributed on the surface of the tungsten block, and the nanopore size of the nanoporous structure is 30-100nm;

[0068] S2, replace the argon and helium atmospheres in S1 with argon atmosphere, adjust the argon pressure to 5Pa, the pulse width of the hollow cathode to 15μs, the frequency to 800Hz, the voltage of the hollow cathode to -1000V, the bias voltage of the second cathode tungsten block to -800V, generate an Ar plasma beam to bombard the surface of the tungsten block treated by S1 with Ar plasma, so that the surface temperature of the tungsten block rises to 1000°C; then adjust the voltage of the hollow cathode to -800V, the pulse width of the hollow cathode to 50μs, the frequency to 800Hz, the bias voltage of the second cathode tungsten block to -600V, and the argon pressure to 5Pa, form a copper plasma beam to irradiate and bombard the surface of the tungsten block for 1h to form a copper infiltration layer with a thickness of 2.2μm;

[0069] S3. Adjust the voltage of the hollow cathode to -1000V, the pulse width of the hollow cathode to 100μs, the frequency to 800Hz, the bias voltage of the second cathode tungsten block to -200V, and the argon gas pressure to 3Pa, so as to form a copper plasma beam to irradiate and bombard the diffusion layer on the surface of the tungsten block for 0.5h to form a copper intermediate layer with a thickness of 1μm, and obtain a large-sized tungsten weldment.

[0070] Comparative Example 1

[0071] The cathode in the hollow cathode is in the shape of a copper tube, and the size of the copper tube is the same as that of the copper mesh hollow cylinder in Example 1. Other aspects are the same as in Example 1.

[0072] It was found that the copper tube could not generate hollow cathode plasma discharge and could not form nanoporous structure, diffusion layer and intermediate layer on the surface of tungsten block.

[0073] Comparative Example 2

[0074] The cathode in the hollow cathode is a copper tube, and the size of the copper tube is the same as the size of the copper mesh hollow cylinder in Example 1. The gas pressure of the argon and helium atmospheres in S1 is 50Pa, the argon pressure in S2 is 50Pa, and the argon pressure in S3 is 50Pa. The rest is the same as Example 1.

[0075] It was found that the copper tube could not generate hollow cathode plasma discharge and could not form nanoporous structure, diffusion layer and intermediate layer on the surface of tungsten block.

[0076] The large-sized tungsten parts to be welded prepared in Example 1 and Comparative Examples 1-2 were used to prepare large-sized tungsten / copper welding components respectively according to the same method.

[0077] The welding method includes the following steps: taking a large-sized tungsten workpiece to be welded and a round copper block (whose size is ) is placed in a vacuum diffusion welding device, the temperature is increased to 500°C at a rate of 10°C / min, the pressure is adjusted to 50MPa, and the temperature is kept for 0.5h; then the temperature is increased to 700°C, the pressure is adjusted to 30MPa, and the temperature is kept for 1h; then the temperature is decreased to 150°C at a rate of 10°C / min, and then cooled with the equipment to obtain a large-sized tungsten / copper welded component.

[0078] The average shear strength of large-size tungsten / copper welded components was tested, and the results are shown in Table 1 and Figure 1 shown.

[0079] The large-sized tungsten / copper welded component of Example 1 was tested and the results were as follows: Figure 1 As shown, Figure 1 The cross-sectional morphology and cross-sectional EDS line scan results of a large-sized tungsten / copper welded component, where a is the cross-sectional morphology and b is the cross-sectional EDS line scan result.

[0080] Depend on Figure 1 It can be seen from a that the weld in this area is well formed and has no obvious defects; Figure 1 b It can be seen that W and Cu form a cross-gradient distribution W / Cu interface, and the thickness of the interdiffusion layer reaches 2.20 μm.

[0081] Figure 1 The mounting resin is used to fix the sample during microscopic characterization.

[0082] Table 1 Average shear strength of large-size tungsten / copper welded components (three parallel samples)

[0083]

[0084]

[0085] As can be seen from Table 1: the cathode in the hollow cathode of the present invention is designed to be mesh-shaped, which can realize the decoupling control of gas and Cu plasma. Under low pressure conditions, by selecting appropriate parameters, only Ar and He plasma beams can be formed without forming Cu plasma, thereby realizing that only a copper mesh hollow cathode can continuously form a nanoporous structure, a copper infiltration layer and a copper intermediate layer on the surface of a large-sized tungsten substrate; and the nanoporous structure can be evenly distributed, the thickness of the infiltration layer is as high as micron level, and the intermediate layer is uniform and flat, which can greatly improve the bonding strength of tungsten and copper during welding. However, the existing hollow cathode cannot realize the welding of large-sized tungsten and copper, and the existing hollow cathode cannot realize the process of continuously forming a nanoporous structure, a copper infiltration layer and a copper intermediate layer using only one hollow cathode.

[0086] The parameters in S1-S3 were adjusted to prepare large-sized tungsten welded parts, and large-sized tungsten / copper welded components were prepared according to the above method, and their average shear strength was tested. The parameter selection and test results are shown in Table 2.

[0087] Table 2 Parameter selection of Examples 2-9 and Comparative Examples 3-9, average shear strength test results of large-size tungsten / copper welded components (three parallel samples)

[0088]

[0089]

[0090] It can be seen from Table 2 that by selecting appropriate parameters, the copper mesh hollow cathode can continuously form a nanoporous structure, a copper infiltration layer and a copper intermediate layer on the surface of a large-sized tungsten substrate, and keep the nanoporous structure evenly distributed, the infiltration layer thickness up to micron level, and the intermediate layer uniform and flat, thereby improving the bonding strength of large-sized tungsten / copper welded components.

[0091] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A metal part to be welded, characterized in that: include: A first metal matrix, a diffusion layer and an intermediate layer, wherein a nanoporous structure is distributed on the surface of the first metal matrix; a second metal is infiltrated and distributed on the surface layer of the first metal matrix, and the nanoporous structure is filled with the second metal to form a diffusion layer; the second metal is deposited on the surface of the diffusion layer to form an intermediate layer; wherein the first metal is a sparingly soluble metal, and the first metal and the second metal are not soluble in each other.

2. The metal workpiece to be welded according to claim 1, characterized in that: The volume of the metal to be welded is ≥1m 3 ; Preferably, the nanopore size of the nanoporous structure is 10-200nm; Preferably, the penetration depth of the diffusion layer is 0.1-10μm; Preferably, the thickness of the intermediate layer is 0.1-10μm; Preferably, the first metal is tungsten or one of tungsten alloys; Preferably, the second metal is copper or one of copper alloys.

3. The metal workpiece to be welded according to claim 1 or 2, characterized in that: A hollow cathode is used for plasma beam irradiation to form a nanoporous structure, a permeation layer and an intermediate layer; preferably, the cathode material in the hollow cathode is a second metal; preferably, the cathode in the hollow cathode is a mesh cathode; preferably, the mesh aperture of the mesh cathode is 0.1-1 cm.

4. The metal workpiece to be welded according to any one of claims 1 to 3, characterized in that: A nanoporous structure is formed on the surface of the first metal substrate by He plasma beam irradiation; preferably, a diffusion layer and an intermediate layer are formed by second metal plasma beam irradiation.

5. A method for preparing a metal workpiece to be welded as claimed in any one of claims 1 to 4, characterized in that: The steps include: S1. In an argon and helium atmosphere, a plasma beam of Ar and He is formed by a hollow cathode to bombard the surface of the first metal substrate, thereby forming a nanoporous structure on the surface of the first metal substrate; S2, in an argon atmosphere, using a hollow cathode to form a plasma beam of a second metal to bombard the surface of the first metal substrate to form a diffusion layer; S3, in an argon atmosphere, using a hollow cathode to form a plasma beam of the second metal to bombard the infiltrated layer to form an intermediate layer, thereby obtaining a metal to be welded; The cathode material in the hollow cathode is a second metal, and the cathode in the hollow cathode is a mesh cathode.

6. The method for preparing a metal workpiece to be welded according to claim 5, characterized in that: In S1, the density of plasma in the plasma beam is 10 19 -10 26 ion / (m 2 ·s); preferably, in S1, the volume ratio of argon and helium is 1-5:1; preferably, in S1, the pulse width of the hollow cathode is 5-30μs; preferably, in S1, the voltage of the hollow cathode is -600 to -2000V; preferably, in S1, the first metal substrate serves as the second cathode, and its bias voltage is -50 to -600V; preferably, in S1, the gas pressure of the argon and helium atmospheres is 1-10Pa; preferably, in S1, first in an argon atmosphere, a hollow cathode is used to form an Ar plasma beam to clean the surface of the first metal substrate, and then in an argon and helium atmosphere, a hollow cathode is used to form an Ar and He plasma beam to irradiate and bombard the surface of the first metal substrate.

7. The method for preparing a metal workpiece to be welded according to claim 5 or 6, characterized in that: In S2, the voltage of the hollow cathode is -500 to -1200V, and the pulse width of the hollow cathode is 50-90μs; preferably, in S2, the first metal substrate serves as the second cathode, and its bias voltage is 0 to -1000V; preferably, in S3, the voltage of the hollow cathode is -500 to -1200V, and the pulse width of the hollow cathode is 100-210μs; preferably, in S3, the first metal substrate serves as the second cathode, and its bias voltage is 0 to -600V; preferably, in S2, the temperature of the first metal substrate is 800-1200℃; preferably, in S2, in an argon atmosphere, a hollow cathode is used to form an Ar plasma beam to irradiate and bombard the surface of the first metal substrate, so that the first metal substrate is heated to 800-1200℃, and then a plasma beam of the second metal is formed to irradiate and bombard the surface of the first metal substrate to form a diffusion layer.

8. Use of the metal weldment as claimed in any one of claims 1 to 4 in welding a first metal and a second metal, wherein: The first metal is a refractory metal, and the first metal and the second metal are not mutually soluble; preferably, the first metal and the second metal are used in welding large-sized components or components with complex shapes.

9. A method for welding large-size tungsten / copper components, characterized in that: The method comprises the following steps: diffusion welding a tungsten workpiece to be welded with copper to obtain a large-sized tungsten / copper welded component, wherein the tungsten workpiece to be welded is a metal workpiece to be welded as claimed in any one of claims 1 to 4, the first metal is one of tungsten and a tungsten alloy, and the second metal is one of copper and a copper alloy.

10. The large-size tungsten / copper component welding method according to claim 9, characterized in that: Diffusion welding is vacuum diffusion welding; preferably, the diffusion welding procedure is: heating to 450-550° C., adjusting the pressure to 40-60 MPa, and keeping warm for 0.5-1 h; Then raise the temperature to 600-750℃, adjust the pressure to 20-40MPa, and keep warm for 0.5-1.5h.

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