Gradient transition controllable preparation method and application of W-Cu functionally graded material

Abstract

The invention discloses a gradient transition controllable preparation method and application of a W-Cu functionally graded material. The invention belongs to the field of W-Cu functionally graded materials and preparation thereof. The invention aims to solve the technical problems of difficulty in gradient transition control, low density and complex process of the existing W-Cu functionally graded material. The method comprises the steps that a Cu solid welding wire and a flux-cored welding wire with W powder inside are made into a stranded welding wire, and the stranded welding wire with the W content changing in a gradient mode is obtained by adjusting the strand number ratio, the diameter ratio and the arrangement mode of the two welding wires; a plurality of stranded welding wires with the W content changing in a gradient mode are sequentially used as filling materials, a coaxial wire feeding arc fuse additive manufacturing method is adopted, the stranded welding wires with different W contents are selected layer by layer according to the W content gradient changing trend to be deposited on the surface of a copper substrate, and the W-Cu functionally graded material is obtained. According to the method, uniform distribution of W powder under different W-Cu components is achieved, and component transition of the W-Cu functionally graded material is achieved.

Description

Technical Field

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

[0002] In a heat-controlled nuclear fusion reactor device, the plasma facing first wall (Plasma facing materials, PSM) is in an extreme service environment because it directly faces the plasma, such as facing extremely high heat loads, plasma scouring 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 prior art 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] The existing processes for preparing W-Cu functional gradient materials are mainly based on melt infiltration and powder metallurgy, but both have shortcomings to a certain extent. For example, in the melt infiltration method, the material composition is difficult to accurately control, the void distribution is uneven, and the sintering temperature is high; in the powder metallurgy method, the production process is complex and requires strict control of the insulation temperature, time and cooling rate. Additive manufacturing, as a highly flexible forming method, has the advantage of not being restricted by traditional processing technology, and provides a new way for the integrated forming of W-Cu functional gradient materials.

[0004] At present, the methods for preparing W-Cu functional gradient materials by additive manufacturing are mainly concentrated in laser powder additive manufacturing (laser powder feeding and laser selective melting). Generally, W powder and Cu powder are mixed by ball milling 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, and 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 by laser additive manufacturing, due to the high reflectivity of Cu laser, problems such as low material density and poor surface roughness are prone to occur during the process of laser additive forming. In addition, the characteristics of the laser heat source determine that this method can only form small-sized parts, with low forming efficiency, and requires multiple powder mixing and powder replacement, and the process is complicated. 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 controllable gradient transition preparation method of W-Cu functional gradient materials and its application.

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

[0007] 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 gradient W content is obtained;

[0008] S2: Using several W-Cu stranded welding wires with W content gradient changes as filling materials in turn, a coaxial wire feeding arc fuse additive manufacturing method is adopted, and W-Cu stranded welding wires with different W contents are selected layer by layer according to the W content gradient change trend to be deposited on the surface of the copper substrate to obtain a W-Cu functional gradient material.

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

[0010] It is further defined 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 welding 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 15-20 L / min.

[0013] It is further defined that 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 functional 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). In addition, from the perspective of fluid mechanics, the convection stirring in the molten pool is related to the flow rate of the liquid. You can refer to the formula of Newton's viscosity law:

[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 of the stranded welding wire on the molten pool is directly related to the shear stress. In order to meet the stirring intensity of the molten pool 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 for 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] The 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 obtained 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] The 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 W powder into flux-cored welding wire, 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 reasonably setting the arc fuse additive manufacturing process parameters, the W powder is evenly distributed under different W-Cu components, and the component transition of the W-Cu functional gradient material is achieved. The specific advantages are as follows:

[0025] (1) Compared with the existing W-Cu functional gradient material preparation method, 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-size 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 common 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 type, which produces a strong stirring effect on the fluid in the molten pool, which is conducive 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 product; 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 to ensure uniform mixing of the components of each layer of powder by ball milling.

[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 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 It is the laser reflectivity of Cu powder under different wavelength lasers in Comparative Example 1. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution 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 used 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 materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

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

[0037] The endpoints and any values ​​of the ranges disclosed in the 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 endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

[0038] Embodiment 1: The controllable preparation method of the gradient transition of the W-Cu functional gradient material of this embodiment is carried out according to 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 welding wires are as follows: Figure 1 As shown, the cored wire has W powder inside and Ni outer skin, the outer skin thickness is 0.05mm, and the W powder filling rate is 80%. The diameter of the solid wire is equal to that of the cored wire, the diameter of each strand is 0.53mm, and the diameter of the overall stranded wire is 1.6mm. The W content (mass percentage) in the 1#, 2#, 3#, and 4# stranded wires is 18%, 34%, 47%, and 57% respectively.

[0040] (2) Computer software is used to perform three-dimensional modeling of the plasma-facing W-Cu functional gradient material, and the established model is sliced. The path planning strategy is selected according to the size characteristics of the part, and the part is imported 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 1# welding wire is used 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 deposition part with a W mass percentage of 18% is obtained;

[0043] When 2# welding wire is used 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 interlayer waiting time 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 3# welding wire is used 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 4# welding wire is used 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 uniform overall distribution. Figure 2 As shown in Table 1, the agglomeration phenomenon is well controlled, the deposition efficiency is high, the W-Cu bonding degree is high, the defects are well controlled, and the porosity is less than 0.00378%, as shown in Table 1. 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 functional gradient material is carried out according to 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 spreading powder, the thickness of each layer of powder is 20 μm, and the W content in each layer is 60%, 65%, 70%, and 75% respectively;

[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 the W-Cu material is completed.

[0053] like Figure 4 As shown, the reflectivity of copper powder under the red laser with a commonly used wavelength of 1064nm 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 above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a W-Cu functional gradient 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 gradient W content is obtained; S2: Using several W-Cu stranded welding wires with W content gradient changes as filling materials in turn, a coaxial wire feeding arc fuse additive manufacturing method is adopted, and W-Cu stranded welding wires with different W contents are selected layer by layer according to the W content gradient change trend to be deposited on the surface of the copper substrate to obtain a W-Cu functional gradient material.

2. The method according to claim 1, characterized in that The outer skin of S1 flux cored wire is Ni, the outer skin thickness is 0.05-0.12mm, and the W powder filling rate is 40-80%.

3. The method according to claim 1, characterized in 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.

4. 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 15-20 L / min.

5. The method according to claim 1, characterized in that The additive manufacturing parameters in S2 are: voltage 10-15V, current 90-140A, wire feeding speed 2.5-6m / min, running speed 0.1-0.5m / min, and inter-layer waiting time 40-100s.

6. The method according to claim 5, characterized in that With the increase of W content in the W-Cu stranded welding wire used in each layer, the additive manufacturing parameters increased layer by layer within the set range.

7. W-Cu functional gradient material obtained by the method according to any one of claims 1 to 6.

8. A plasma first wall, characterized in that: The plasma first wall is made of W—Cu functional gradient material prepared by the method described in any one of claims 1-6.

9. Application of the plasma first wall according to claim 8 in the field of thermonuclear fusion.

10. Use of the method according to any one of claims 1 to 6 in preparing functional gradient materials formed by multiple metals with large sizes and obvious differences in thermal properties.

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