A W-Cu functionally graded material with controlled gradient transition and its application

Abstract

A method for preparing a W‑Cu functional gradient material with controllable gradient transition and its application. The present invention belongs to the field of W‑Cu functional gradient materials and their preparation. The purpose of the present invention is to solve the technical problems of difficult gradient transition control, low density and complex process of existing W‑Cu functional gradient materials. The method of the present invention: a stranded welding wire is made of a Cu solid welding wire and a flux-cored welding wire with W powder inside, and a stranded welding wire with a gradient change in W content is obtained by adjusting the strand ratio, diameter ratio and arrangement of the two welding wires; a plurality of stranded welding wires with a gradient change in W content are sequentially used as filling materials, and a coaxial wire feeding arc fuse additive manufacturing method is adopted, and stranded welding wires with different W contents are selected layer by layer according to the gradient change trend of the W content to be deposited on the surface of a copper substrate to obtain a W‑Cu functional gradient material. The method of the present invention realizes uniform distribution of W powder under different W‑Cu components, thereby achieving component transition of the W‑Cu functional gradient material.

Description

Technical Field

[0001] The present invention belongs to the field of W-Cu functional gradient materials and preparation thereof, and particularly relates to a controllable gradient transition preparation method of W-Cu functional gradient materials and application thereof. Background Art

[0002] In a heat-controlled nuclear fusion reactor device, the plasma-facing first wall (Plasma facing materials, PSM) is directly facing the plasma and is in an extreme service environment, such as facing extremely high heat loads, plasma scour and neutron irradiation. Therefore, the first wall material is required to be able to maintain mechanical integrity and dimensional stability in harsh environments, that is, the first wall material must have a high melting point, high thermal shock resistance, high thermal conductivity, low vapor pressure and good radiation resistance. W-Cu material is considered to be the best option as the first wall material. However, due to the large difference in the physical properties of W and Cu, when the tungsten surface is subjected to a large thermal load, a large thermal stress is generated at the junction of the two and cracks are generated, resulting in material failure. Therefore, the existing technology is to effectively reduce the stress concentration at the interface of dissimilar materials by continuously changing the composition and structure of the W-Cu material to form a functional gradient material.

[0003] Existing processes for preparing W-Cu functionally gradient materials primarily rely on melt infiltration and powder metallurgy, but both methods have limitations. For example, melt infiltration suffers from difficulties in precisely controlling material composition, uneven void distribution, and high sintering temperatures; while powder metallurgy presents a complex manufacturing process requiring strict control of holding temperature, time, and cooling rate. Additive manufacturing, as a highly flexible forming method, offers the advantage of being unrestricted by traditional machining processes and offers a new approach for the integrated forming of W-Cu functionally gradient materials.

[0004] At present, the methods for preparing W-Cu functional gradient materials using additive manufacturing are mainly concentrated in laser powder additive manufacturing (laser powder feeding and laser selective melting). Generally, W powder and Cu powder are ball-milled and mixed according to different composition ratios, and then the Cu powder is melted by laser. W powder is distributed in the Cu matrix as solid particles. The transition of W-Cu functional gradient materials is achieved by changing the ratio of W-Cu components. However, when forming W-Cu functional gradient materials using laser additive manufacturing, due to the high reflectivity of Cu laser, problems such as low material density and poor surface roughness are easily encountered during the laser additive forming process. In addition, the characteristics of the laser heat source determine that this method can only form smaller parts, with low forming efficiency, and requires multiple powder mixing and powder replacement, which is a complex process. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problems of difficult gradient transition control, low density and complex process of existing W-Cu functional gradient materials. The present invention provides a method for preparing W-Cu functional gradient materials with controllable gradient transition and its application.

[0006] One of the purposes of the present invention is to provide a method for preparing a W-Cu functionally gradient material with controlled gradient transition, the method being carried out in the following steps:

[0007] S1: W-Cu stranded welding wire is made of Cu solid welding wire and flux-cored welding wire with W powder inside. By adjusting the strand ratio, diameter ratio and arrangement of the two welding wires, W-Cu stranded welding wire with a gradient of W content is obtained;

[0008] S2: Using several W-Cu stranded welding wires with varying W content gradients as filling materials, a coaxial wire-feeding arc-fused wire additive manufacturing method is used. W-Cu stranded welding wires with varying W content are selected layer by layer according to the W content gradient trend and deposited on the surface of the copper substrate to obtain a W-Cu functionally gradient material.

[0009] It is further defined that the outer sheath of the flux-cored wire in S1 is Ni.

[0010] It is further specified that the outer skin thickness of the flux-cored welding wire is 0.05-0.12 mm and the W powder filling rate is 40-80%.

[0011] It is further defined that the strand ratio, diameter ratio and arrangement of the two welding wires in S1 are determined according to the W content gradient setting form in the target component. To ensure uniform W distribution in each layer of the target component, the two welding wires are symmetrically arranged.

[0012] It is further defined that the vertical distance between the gun tip and the substrate in S2 is 12-16 mm, the angle between the gun tip and the normal of the substrate is 5-20°, and the shielding gas is argon at a flow rate of 15-20 L / min.

[0013] Further definition, the additive manufacturing parameters in S2 are: voltage is 10-15V, current is 90-140A, wire feeding speed is 2.5-6m / min, running speed is 0.1-0.5m / min, and inter-layer waiting time is 40-100s.

[0014] The present invention fully considers the influence of the stirring effect of the stranded welding wire on the molten pool, the heat input and the flow characteristics during the deposition process. As the W powder content in the functionally gradient material changes, different heat inputs are matched according to the deposition requirements of the workpiece to meet the molten pool stirring intensity under different W-Cu ratios, so as to achieve uniform distribution of the W powder and reduce the agglomeration effect.

[0015]

[0016] Where Q is the heat input, η is the thermal efficiency, U is the arc voltage (V), I is the welding current (A), and v is the welding speed (mm / s). Furthermore, from a fluid mechanics perspective, convection stirring in the molten pool is related to the flow rate of the liquid. You can refer to the formula for Newton's law of viscosity:

[0017]

[0018] Where τ is the shear stress, μ is the dynamic viscosity, and du / dy is the velocity gradient. In the molten pool, the stirring effect brought by the stranded welding wire to the molten pool is directly related to the shear stress. In order to meet the molten pool stirring intensity under different W-Cu ratios, so as to achieve the purpose of uniform distribution of W powder and reduce the agglomeration effect, the present invention increases the wire feeding speed as the W content increases during the parameter setting process, ensuring that a larger velocity gradient can be provided to the molten pool during the deposition process, thereby increasing the molten pool stirring shear stress brought by the stranded welding wire. Therefore, the present invention further defines the additive manufacturing parameters in S2: as the W content in the W-Cu stranded welding wire used in each layer increases, the additive manufacturing parameters increase layer by layer within the set range.

[0019] A second object of the present invention is to provide a W-Cu functional gradient material prepared according to the above method.

[0020] A third object of the present invention is to provide a plasma first wall, wherein the plasma first wall is made of the W-Cu functional gradient material prepared by the above method.

[0021] A fourth object of the present invention is to provide an application of the above-mentioned plasma first wall in the field of thermonuclear fusion.

[0022] A fifth object of the present invention is to provide an application of the above method in the preparation of functional gradient materials formed by multiple metals with large sizes and obvious differences in thermal properties.

[0023] The advantages of the present invention compared to the prior art are:

[0024] The present invention prepares flux-cored wire from W powder, coats it with Ni, and twists it with Cu wire in different proportions to obtain a special welding wire for additive manufacturing of W-Cu functional gradient materials. By rationally setting the arc-fuse additive manufacturing process parameters, W powder is evenly distributed under different W-Cu compositions, achieving the composition transition of the W-Cu functional gradient material. The specific advantages are as follows:

[0025] (1) Compared with the existing preparation method of W-Cu functional gradient materials, the method of the present invention greatly improves the deposition efficiency, simplifies the process flow, reduces the manufacturing cost, shortens the production cycle, and can realize the preparation of large-scale W-Cu functional gradient materials;

[0026] (2) The method of the present invention significantly improves the problems of energy loss and poor forming quality caused by the high laser reflectivity of Cu in the laser additive manufacturing process, such as Figure 4 As shown, the reflectivity of copper powder under the red laser with a commonly used wavelength of 1064nm is between 60.6% and 79.2%;

[0027] (3) The present invention uses the unique rotating arc shape of the stranded welding wire to make the liquid metal in the molten pool flow in a vortex-like manner, which produces a strong stirring effect on the fluid in the molten pool, contributes to the uniform distribution of multiple elements and the overflow of gas in the molten pool, thereby improving the uniformity and density of the W-Cu functional gradient material;

[0028] (4) The arrangement of the solid welding wire and the flux-cored welding wire of the present invention helps to more evenly distribute the W powder in the molten pool under different component gradient transition conditions, reduce the degree of W powder agglomeration, and improve the isotropic properties of the workpiece; at the same time, it avoids the problem of frequent powder spreading and powder replacement during the deposition of each layer in the laser powder additive manufacturing process, and the need for ball milling of each layer of powder to ensure uniform mixing of the components.

[0029] (5) The present invention uses Ni as the coating material of W powder, which improves the problem of poor wettability between W and Cu to a certain extent, thereby achieving the purpose of improving the W-Cu bonding ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the characteristics and structure of the W-Cu stranded welding wire in Example 1;

[0031] Figure 2 This is the W-Cu functional gradient material structure obtained in Example 1;

[0032] Figure 3 The porosity of the W-Cu functional gradient material obtained in Example 1;

[0033] Figure 4 is the laser reflectivity of Cu powder under different wavelengths of laser in Comparative Example 1. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0036] As used in the following examples, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0037] The endpoints of the ranges and any values disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0038] Example 1: The controllable gradient transition preparation method of the W-Cu functionally gradient material of this embodiment is carried out by the following steps:

[0039] (1) In this embodiment, the ratio of the number of strands, the ratio of the diameters and the arrangement of the W-Cu stranded wires are as follows: Figure 1 As shown, the flux-cored wire contains W powder inside and a Ni sheath with a thickness of 0.05mm. The W powder filling ratio is 80%. The diameters of the solid and flux-cored wires are the same, with a single strand diameter of 0.53mm and a strand diameter of 1.6mm. The W content (by mass) in stranded wires #1, #2, #3, and #4 is 18%, 34%, 47%, and 57%, respectively.

[0040] (2) Use computer software to perform three-dimensional modeling of the plasma-facing W-Cu functional gradient material, slice the established model, select the path planning strategy according to the dimensional characteristics of the part, and import it into the additive manufacturing equipment.

[0041] (3) The vertical distance between the welding gun tip and the substrate is 13 mm, the angle between the gun tip and the substrate normal is 8°, and the shielding gas is argon at 15 L / min;

[0042] When using No. 1 welding wire for deposition, the welding voltage is 10V, the current is 92A, the wire feeding speed is 2.5m / min, the running speed is 0.1m / min, and the interlayer waiting time is 40s. After the deposition is completed on the copper substrate, a deposited portion with a W mass percentage of 18% is obtained;

[0043] When using 2# welding wire for deposition, the welding voltage is 11V, the current is 98A, the wire feeding speed is 3.0m / min, the running speed is 0.2m / min, and the waiting time between layers is 50s. After the deposition is completed on the basis of the previous part, a deposition part with a W mass percentage of 34% is obtained;

[0044] When using 3# welding wire for deposition, the welding voltage is 12V, the current is 106A, the wire feeding speed is 4.0m / min, the running speed is 0.25m / min, and the interlayer waiting time is 60s. After the deposition is completed on the basis of the previous part, a deposition part with a W mass percentage of 47% is obtained;

[0045] When using 4# welding wire for deposition, the welding voltage is 14V, the current is 127A, the wire feeding speed is 5.0m / min, the running speed is 0.35m / min, the interlayer waiting time is 70s, and after the deposition is completed on the basis of the previous part, a deposition part with a W mass percentage of 57% is obtained.

[0046] After the above steps are completed, the preparation of the plasma-facing W-Cu functional gradient material for the nuclear fusion tokamak device is realized. The W-Cu functional gradient material prepared by the present invention has a large W content gradient transition range and a uniform overall distribution. Figure 2 As shown in Table 1, the agglomeration phenomenon is well controlled and the deposition efficiency is high. The W-Cu bonding degree is high and the defects are well controlled. The porosity is less than 0.00378%. Figure 3 As shown, it can be seen that the present invention has obvious advantages over the prior art in preparing W-Cu functional gradient materials.

[0047] Comparative Example 1: Laser Selective Melting Additive Manufacturing of W-Cu Functionally Gradient Materials was carried out in the following steps:

[0048] (1) Select a laser with a wavelength of 1060-1100 nm;

[0049] (2) A laser beam with a spot diameter of 0.1 mm is used as the heat source, the protective gas is Ar, and the oxygen volume fraction in the forming chamber is less than 0.1%;

[0050] (3) The powder is fed in by a spreading method, with each layer of powder being 20 μm thick, and the W content in each layer being 60%, 65%, 70%, and 75% in sequence;

[0051] (4) Laser power 200 W, scanning speed 400 mm / s, overlap rate 10%;

[0052] (5) As the deposited layers gradually accumulate to form a multilayer component, the additive manufacturing of W-Cu materials is completed.

[0053] like Figure 4 As shown, the reflectivity of copper powder under a red laser with a commonly used wavelength of 1064 nm is 60.6-79.2%.

[0054] Table 1

[0055] W content variation span (%) <![CDATA[Deposition efficiency (mm 3 / h)]]> Example 1 39 90490 Comparative Example 1 15 2880

[0056] The foregoing are merely preferred embodiments of the present invention. These embodiments are all different implementations based on the overall concept of the present invention. The scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person 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 based on the scope of protection of the claims.

Claims

1. A method for preparing a W-Cu functionally graded material with controlled gradient transition, characterized in that: The method: S1: A W-Cu stranded welding wire is made of a Cu solid welding wire and a flux-cored welding wire with W powder inside. By adjusting the strand ratio, diameter ratio, and arrangement of the two welding wires, a W-Cu stranded welding wire with a W content gradient is obtained. The outer sheath of the flux-cored welding wire is Ni, with a thickness of 0.05-0.12mm, and a W powder filling rate of 40-80%. The strand ratio, diameter ratio, and arrangement of the two welding wires are determined according to the W content gradient setting in the target component. To ensure uniform W distribution in each layer of the target component, the two welding wires are arranged symmetrically. S2: Several W-Cu stranded welding wires with gradient W content were used as filling materials in sequence. The coaxial wire feeding arc fusion additive manufacturing method was adopted. W-Cu stranded welding wires with different W contents were selected layer by layer according to the W content gradient trend and deposited on the surface of the copper substrate to obtain W-Cu functional gradient material. The additive manufacturing parameters were as follows: voltage of 10-15V, current of 90-140A, wire feeding speed of 2.5-6m / min, running speed of 0.1-0.5m / min, and interlayer waiting time of 40-100s. As the W content in the W-Cu stranded welding wire used in each layer increased, the additive manufacturing parameters increased layer by layer within the set range.

2. The method according to claim 1, characterized in that In S2, the vertical distance between the welding gun tip and the substrate is 12-16 mm, the angle between the gun tip and the substrate normal is 5-20°, and the shielding gas is argon at a flow rate of 15-20 L / min.

3. A W-Cu functionally gradient material prepared by the method according to any one of claims 1 to 2.

4. A plasma first wall, characterized in that The plasma first wall is made of a W-Cu functional gradient material prepared by the method according to any one of claims 1 to 2.

5. Application of the plasma first wall according to claim 4 in the field of thermonuclear fusion.

6. Use of the method according to any one of claims 1 to 2 in the preparation of functionally gradient materials composed of multiple metals with large sizes and obvious differences in thermal properties.

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