Gradient composite material for controlled nuclear fusion reactor, preparation process thereof and method for connecting with first wall of blanket

Abstract

This invention discloses a gradient composite material for controlled nuclear fusion reactors, its preparation process, and its connection method with the first wall of the blanket, relating to the field of manufacturing technology for plasma-oriented components and the first wall of the blanket in nuclear fusion reactors. A gradient composite material for controlled nuclear fusion reactors comprises, from top to bottom, an upper metal layer, a first gradient layer, an intermediate transition layer, a second gradient layer, and a bottom metal layer; the upper metal layer is tungsten or a tungsten alloy, the intermediate transition layer metal is vanadium or a vanadium alloy, and the bottom metal is low-activation ferritic / martensitic steel. Compared to traditional tungsten / steel gradient layers, this invention reduces the formation of brittle phases between tungsten and steel through the design of the intermediate gradient layer and the connection of homogeneous materials. Simultaneously, the vanadium or vanadium alloy material used is a low-activation and low-hydrogen-embrittlement-sensitive material, effectively alleviating the welding and thermal stress mismatch problems between dissimilar metals, and improving the service reliability and lifespan of the blanket components in the harsh environment of nuclear fusion devices.

Description

Technical Field

[0001] This invention relates to the field of manufacturing technology of plasma-oriented materials / components and the first wall of the blanket in nuclear fusion reactors, and particularly to a gradient composite material for controlled nuclear fusion reactors, its preparation process, and its connection method with the first wall of the blanket. Background Technology

[0002] Energy security and other issues are becoming increasingly serious, posing one of the most severe challenges facing human society in the 21st century. Fusion energy, with its abundant, inexpensive, environmentally friendly, and safe fuels, is considered a "clean, safe, and sustainable" energy source. In magnetic confinement fusion devices, the first wall and blanket structural materials face harsh operating environments, including high heat loads and high-flux neutron irradiation. Tungsten (or tungsten alloys) is the plasma-oriented material (PFM) for the China Fusion Engineering Experimental Reactor (CFETR) and the Fusion Demonstration Reactor (DEMO), with low-activation ferrite / martensitic (RAFM) steel considered the preferred structural material for fusion reactors. The connection between the PFM and structural materials in the plasma-oriented components (PFC) is crucial and has become one of the bottleneck issues in the development of fusion energy.

[0003] While methods such as direct bonding of tungsten with low-activation ferrite / martensitic steel and traditional high-temperature diffusion bonding have achieved the connection between PFC and the first wall component of the cladding, the difference in thermal expansion coefficients between the cladding material (low-activation ferrite / martensitic steel) and the plasma-facing material (tungsten) under high thermal loads can cause significant thermal stress at the interface during service, leading to interface deformation, mismatch, or even separation. This seriously threatens the integrity and service life of the structure. In the integrated manufacturing of large-scale, complex structures for plasma-facing components and structural materials, avoiding interface failure at the direct bonding interface of dissimilar metals and achieving efficient and reliable bonding is a pressing technical problem that needs to be solved.

[0004] To address the aforementioned issues, existing technologies typically introduce an intermediate metal layer and a composition gradient layer as transition layers, and then use hot isostatic pressing (HIP) diffusion bonding to diffuse-weld the gradient plate, plasma-facing material, and cladding structure material. However, the aforementioned conventional processes have the following technical drawbacks:

[0005] (1) Complex interface properties: There is a dissimilar material interface between the gradient plate and the low-activation ferrite / martensitic steel matrix (the gradient plate usually contains a high content of tungsten or tungsten alloy or other alloying elements, which is very different from the composition of the matrix). The atomic diffusion rates of the dissimilar material interface are very different, and brittle intermetallic compounds or Kirkendal pores are easily formed during thermal cycling, resulting in low interfacial bonding strength. Intermediate layers such as Ti, Cu, Nb, and Ni can achieve effective connection between tungsten and low-activation ferrite / martensitic steel. However, Cu, Nb, and Ni are non-low-activation elements and are not suitable for fusion reactor materials; while Ti intermediate layers will form brittle phases and have high hydrogen embrittlement sensitivity.

[0006] (2) Poor interface healing ability: During the cooling and subsequent heat treatment process after HIP, the interface of dissimilar materials is difficult to achieve "self-healing" through recrystallization or grain boundary migration to eliminate micro-defects, making the interface a weak link in the entire component.

[0007] Therefore, there is an urgent need to develop a fabrication process that can effectively alleviate interfacial stress, avoid the formation of brittle phases, and enable reliable integrated manufacturing of large-size complex structures. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a gradient composite material for controlled nuclear fusion reactors and its preparation process. This gradient composite material can significantly improve interfacial bonding strength, eliminate interfacial defects by utilizing the self-healing properties of homogeneous materials, and simultaneously optimize matrix properties.

[0009] The present invention also provides a method for connecting a gradient composite material for a controlled nuclear fusion reactor to the first wall of the cladding.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A gradient composite material for a controlled nuclear fusion reactor comprises, from top to bottom, an upper metal layer, a first gradient layer, an intermediate transition layer, a second gradient layer, and a bottom metal layer; the upper metal layer is tungsten or a tungsten alloy, the intermediate transition layer is vanadium or a vanadium alloy, and the bottom metal layer is low-activation ferrite / martensitic steel.

[0012] The composition of the first gradient layer transitions continuously from 100% upper metal to 100% intermediate transition layer metal; the composition of the second gradient layer transitions continuously from 100% intermediate transition layer metal to 100% bottom metal.

[0013] The thickness of the upper metal layer is 0.2~3mm, the thickness of the first gradient layer is 0.1~1mm, the thickness of the intermediate transition layer is 0.1~1mm, the thickness of the second gradient layer is 0.1~1mm, and the thickness of the bottom metal layer is 0.5~5mm.

[0014] The preparation process of the gradient composite material for controlled nuclear fusion reactors described above includes the following steps:

[0015] Step S1: Fix the substrate in the build chamber of the selective laser melting device;

[0016] Step S2: The substrate is preheated and then a selective laser melting process is used to sequentially form an upper metal layer, a first gradient layer, an intermediate transition layer, a second gradient layer, and a bottom metal layer on the substrate to obtain a gradient composite material for controlled nuclear fusion reactors. The upper metal layer is tungsten or a tungsten alloy, which is suitable for the first wall material facing plasma. The intermediate transition layer metal is vanadium or a vanadium alloy. The bottom metal layer is a low-activation ferrite / martensitic steel, which is a candidate structural material for cladding the first wall.

[0017] In the process of forming the first gradient layer, the powder feeding ratio is adjusted according to the designed mass percentage of each layer, and the continuous gradient transition of the composition is achieved by mixing and conveying the upper metal powder and the intermediate transition layer metal powder in proportion.

[0018] When forming the second gradient layer, the powder feeding ratio is adjusted according to the designed mass percentage of each layer, and the intermediate transition layer metal powder and the bottom layer metal powder are mixed and transported in proportion to achieve a continuous gradient transition of components.

[0019] The temperature of the preheating treatment in step S2 is 300~1200℃.

[0020] In step S2, the laser power of the selective laser process is 150~400W.

[0021] In step S2, the height of the powder layer is 20~30μm.

[0022] The laser energy density used in forming the upper metal layer is greater than 250 J / mm². 3 The laser energy density used in forming the intermediate transition layer metal is 70~120 J / mm². 3 The laser energy density used in forming the underlying metal is greater than 190 J / mm². 3 .

[0023] A method for connecting a gradient composite material for a controlled nuclear fusion reactor to the first wall of the blanket, wherein the bottom metal of the gradient composite material for the controlled nuclear fusion reactor is connected to the first wall of the blanket.

[0024] The above-mentioned method for connecting the gradient composite material to the first wall of the blanket in a controlled nuclear fusion reactor includes the following steps:

[0025] S3: The gradient composite material for controlled nuclear fusion reactors is connected to the first wall of the blanket through a hot isostatic pressing process; the parameters of the hot isostatic pressing are: temperature of 1050~1150℃, pressure of 100~200MPa, and heat and pressure holding time of 2~8h.

[0026] Before the hot isostatic pressing process, the surfaces of the gradient composite material and the first wall of the blanket for the controlled nuclear fusion reactor must be cleaned and fixed by spot welding.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) The gradient composite material for controlled nuclear fusion reactors proposed in this invention mainly includes plasma-oriented materials, transition region materials, and structural materials. The plasma-oriented component material adopts a gradient material design. Vanadium or vanadium alloys have low activation and can be infinitely dissolved with tungsten or tungsten alloys, effectively avoiding the formation of brittle intermetallic compounds formed by direct bonding between tungsten or tungsten alloys and low-activation ferrite / martensitic steel. In addition, the physical properties of vanadium or vanadium alloys are between those of tungsten or tungsten alloys and low-activation ferrite / martensitic steel, which can effectively alleviate thermal stress concentration and enhance structural stability and reliable connection.

[0029] (2) The gradient composite material for controllable nuclear fusion reactor proposed in this invention is designed with the thickness of each layer material as the design goal of minimizing thermal stress. The layers are uniformly transitioned, which effectively relieves thermal stress, makes the temperature distribution more balanced, improves the stability of the cladding module, and extends the service life of the cladding module.

[0030] (3) The present invention uses selective laser melting to prepare gradient composite materials on existing tungsten plates. Compared with the preparation of tungsten-vanadium or vanadium alloy-low-activation ferrite / martensitic steel gradient materials by direct selective laser melting, it effectively avoids the problems of cracking that exist in additive manufacturing of tungsten alloys, and greatly improves the reliability and stability of the structure.

[0031] (4) This invention connects the gradient composite material to the first cladding wall via HIP. Compared with the method of directly welding tungsten or tungsten alloy to the first cladding wall, this invention can effectively reduce interfacial stress, form a continuous metallurgical bond, and avoid the problem of interfacial failure caused by the presence of dissimilar material interfaces. Selective laser melting precisely controls the gradient composition distribution, providing an ideal "preform" for subsequent HIP; while HIP not only achieves the connection, but also eliminates the residual porosity that may exist in the selective laser melting formed parts, and optimizes the microstructure of the low-activation ferrite / martensitic steel matrix, greatly improving product quality and long-term stable and safe operation. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the gradient composite material for the controlled nuclear fusion reactor of the present invention.

[0033] Figure 2 This is a schematic diagram of the structure of the gradient composite material for the controlled nuclear fusion reactor of the present invention after being connected to the first wall of the cladding.

[0034] Figure 3 This is a schematic diagram of the structure after the composite components of Comparative Example 2 are connected.

[0035] The reference numerals in the attached figures are as follows: 1-substrate; 2-upper metal layer; 3-first gradient layer; 4-intermediate transition layer metal; 5-second gradient layer; 6-bottom metal layer; 7-cladding first wall; 100-tungsten plate; 200-tungsten-titanium interface; 300-titanium metal intermediate layer; 400-titanium-low-activation ferrite / martensitic steel interface; 500-low-activation ferrite / martensitic steel. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0037] See Figure 1 This invention proposes a gradient composite material for controlled nuclear fusion reactors, which comprises, from top to bottom, an upper metal layer 2, a first gradient layer 3, an intermediate transition layer metal 4, a second gradient layer 5, and a bottom metal 6; wherein the composition of the first gradient layer 3 continuously gradients from 100% upper metal layer 2 to 100% intermediate transition layer metal 4; and the composition of the second gradient layer 5 continuously gradients from 100% intermediate transition layer metal 4 to 100% bottom metal 6.

[0038] In this embodiment, the upper metal 2 is tungsten or a tungsten alloy, which is adapted to the first wall material facing plasma; the middle transition layer metal 4 is vanadium or a vanadium alloy with low activation; and the bottom metal 6 is ferrite / martensitic steel, which is a candidate structural material for the cladding first wall 7.

[0039] Preferably, the thickness of the upper metal layer 2 is 0.2-3 mm, the thickness of the first gradient layer 3 is 0.1-1 mm, the thickness of the intermediate transition layer metal 4 is 0.1-1 mm, the thickness of the second gradient layer 5 is 0.1-1 mm, and the thickness of the bottom metal layer 6 is 0.5-5 mm.

[0040] Example 1:

[0041] The gradient composite material for the controlled nuclear fusion reactor in this embodiment comprises, from top to bottom, a tungsten layer, a tungsten-vanadium gradient layer, a vanadium layer, a vanadium-low-activation ferrite / martensitic steel gradient layer, and a low-activation ferrite / martensitic steel layer. The composition of the tungsten-vanadium gradient layer transitions continuously from 100% tungsten material to 100% vanadium metal; the composition of the vanadium-low-activation ferrite / martensitic steel gradient layer transitions continuously from 100% vanadium metal to 100% low-activation ferrite / martensitic steel. The thickness of the tungsten layer is 2 mm, the tungsten-vanadium gradient layer is 1 mm, the vanadium layer is 1 mm, the vanadium-low-activation ferrite / martensitic steel gradient layer is 1 mm, and the low-activation ferrite / martensitic steel layer is 5 mm.

[0042] The preparation process of the aforementioned gradient composite material for controlled nuclear fusion reactors includes the following steps:

[0043] S1: Select a 2mm thick tungsten plate as substrate 1, preheat substrate 1 to 700℃, and fix it in the construction chamber of the selective laser melting equipment. Use a scraper to evenly spread a layer of tungsten powder on substrate 1.

[0044] S2: Forming Tungsten Layer: Selective laser melting equipment using fiber laser with a maximum power of 400W and a spot diameter of 70μm is used. Under Ar protective gas, the laser power is 400W, the scanning rate is 600 mm / s, the powder layer thickness is 30μm, and the hatch distance is 85μm. The laser forms tungsten powder selectively according to the contour information of each slice. After one layer is melted, the platform descends 30μm, and the powder spreading and laser melting steps are repeated until a tungsten layer thickness of 1mm is achieved.

[0045] S3: Forming a tungsten-vanadium gradient layer: Tungsten powder or vanadium or vanadium alloy powder is mixed and fed into a powder mixer according to the designed mass percentage of each layer. Under Ar gas protection, the forming parameters are kept consistent with those of the tungsten layer. A laser is used to selectively melt the powder according to the contour information of each slice. After one layer is melted, the platform drops by 30 μm. The powder spreading and laser melting steps are repeated until a tungsten-vanadium gradient layer with a continuous gradient transition of composition of 1 mm is achieved.

[0046] S4: Forming the intermediate vanadium layer: A layer of vanadium powder is evenly spread on substrate 1 using a scraper. Under Ar protective gas, the vanadium powder is formed by laser with a laser power of 180W, a scanning rate of 600mm / s, a powder layer thickness of 30μm, and a hatch distance of 85μm. The laser selectively melts the powder according to the contour information of each slice. After one layer is melted, the platform drops by 30μm. The powder spreading and laser melting steps are repeated until a vanadium layer thickness of 1 mm is achieved.

[0047] S5: Forming Vanadium-Low-Activation Ferrite / Martensitic Steel Gradient Layer: By mixing vanadium powder with low-activation ferrite / martensitic steel powder, the powder feeding ratio is adjusted according to the designed mass percentage of each layer and fed into the powder mixer for uniform mixing. Under Ar gas protection, the forming parameters are consistent with the vanadium layer. A laser is used to selectively melt the powder according to the contour information of each layer slice. After one layer is melted, the platform drops by 30μm. The powder spreading and laser melting steps are repeated until a vanadium-low-activation ferrite / martensitic steel gradient layer with a continuous gradient transition of composition of 1mm is achieved.

[0048] S6: Forming a low-activation ferrite / martensitic steel layer: The powder feeding system for placing vanadium powder is turned off, and only the low-activation ferrite / martensitic steel powder is fed. A layer of low-activation ferrite / martensitic steel powder is evenly spread on substrate 1 using a scraper. Under Ar protective gas, the low-activation ferrite / martensitic steel layer is formed by laser with a laser power of 320W, a scanning rate of 600mm / s, a powder layer thickness of 30μm, and a hatch distance of 85μm. The laser selectively melts the powder according to the contour information of each slice. After one layer is melted, the platform is lowered by 30μm. The powder spreading and laser melting steps are repeated until a low-activation ferrite / martensitic steel layer thickness of 5mm is achieved.

[0049] Example 2:

[0050] See Figure 2 This embodiment provides a blanket structure for a controlled nuclear fusion reactor, which, from top to bottom, includes an upper metal layer 2, a first gradient layer 3, an intermediate transition metal layer 4, a second gradient layer 5, a bottom metal layer 6, and a first blanket wall 7. The bottom metal layer 6 is connected to the first blanket wall 7.

[0051] The above-mentioned method for connecting the gradient composite material for controlled nuclear fusion reactors to the first wall of the blanket specifically involves connecting the gradient composite material for controlled nuclear fusion reactors to the first wall 7 of the blanket through a hot isostatic pressing process; the hot isostatic pressing temperature is 1100℃, the pressure is 150MPa, and the heat and pressure holding time is 8 hours.

[0052] Preferably, the gradient composite material for controlled nuclear fusion reactors is first fixed to the first wall of the blanket 7 by spot welding, and then the connection between the gradient composite material for controlled nuclear fusion reactors and the first wall of the blanket 7 is achieved by hot isostatic pressing.

[0053] Furthermore, the surfaces of the gradient material and cladding material must be clean and maintain a certain roughness before hot isostatic pressing.

[0054] Ultrasonic testing showed that the interlayer bonding and final HIP (High-Intensity Interconnect) interface of the blanket material for the controlled nuclear fusion reactor obtained in Example 2 were good, with no obvious defects. Simulation calculations showed that this gradient design reduced the maximum thermal stress by approximately 40% compared to the direct-connection structure.

[0055] Comparative Example 1:

[0056] A component was constructed by directly joining a tungsten plate to a low-activation ferritic / martensitic steel using the same HIP process. After thermal cycling testing, obvious cracks appeared at the interface, while the component of this invention maintained an intact interface, demonstrating the effectiveness of the invention.

[0057] Comparative Example 2:

[0058] Pure Ti metal is used as the intermediate bonding layer, and the tungsten plate is connected to the low-activation ferritic / martensitic steel component using the HIP process. For example... Figure 3 As shown, the components in Comparative Example 2 sequentially include a tungsten plate 100, a titanium metal interlayer 300, and a low-activation ferrite / martensitic steel 500, wherein a tungsten-titanium interface 200 exists between the tungsten plate 100 and the titanium metal interlayer 300, and a titanium-low-activation ferrite / martensitic steel interface 400 exists between the titanium metal interlayer 300 and the low-activation ferrite / martensitic steel 500. Figure 3 It can be seen that the bonding between the tungsten-titanium interface 200 and the titanium-low-activation ferrite / martensitic steel interface 400 is relatively good, but a brittle phase exists on the Ti-RAFM steel side. Furthermore, studies show that Ti has a high sensitivity to hydrogen embrittlement, and these issues limit the use of Ti metal as an intermediate bonding layer in fusion environments.

[0059] In summary, this invention proposes a gradient composite material for controlled nuclear fusion reactors and its preparation process. This gradient composite material comprises an upper metal layer 2, an intermediate transition metal layer 4, and a bottom metal layer 6, with a first gradient layer 3 and a second gradient layer 5 providing a continuous gradient transition in composition between the layers. The upper metal layer 2 is tungsten or a tungsten alloy, suitable for the first wall material facing plasma; the intermediate transition metal layer 4 is vanadium or a vanadium alloy with low activation; and the bottom metal layer 6 is a candidate structural material for the cladding first wall 7, namely, low-activation ferrite / martensitic steel 500. The preparation process includes: using selective laser melting, and by dynamically adjusting the powder feeding ratio, sequentially forming each layer of material on a substrate 1 to obtain the gradient composite material. This invention achieves minimum interfacial stress through gradient material design and preparation, while selective laser melting technology precisely controls the gradient composition distribution, providing an ideal "preform" for subsequent HIP. HIP not only achieves connection but also eliminates residual porosity that may exist in the selective laser melting formed parts and optimizes the microstructure of the low-activation ferrite / martensitic steel matrix, realizing efficient and reliable integrated manufacturing of large-size, complex structures for plasma components and structural materials.

[0060] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A gradient composite material for controlled nuclear fusion reactors, characterized in that, The gradient composite material for the controlled nuclear fusion reactor comprises, from top to bottom, an upper metal layer, a first gradient layer, an intermediate transition layer, a second gradient layer, and a bottom metal layer; the upper metal layer is tungsten or a tungsten alloy, the intermediate transition layer is vanadium or a vanadium alloy, and the bottom metal layer is low-activation ferrite / martensitic steel. The composition of the first gradient layer transitions continuously from 100% upper metal to 100% intermediate transition layer metal; the composition of the second gradient layer transitions continuously from 100% intermediate transition layer metal to 100% bottom metal.

2. The gradient composite material for controlled nuclear fusion reactors according to claim 1, characterized in that, The thickness of the upper metal layer is 1-3 mm, the thickness of the first gradient layer is 0.5-5 mm, the thickness of the intermediate transition layer is 0.5-5 mm, the thickness of the second gradient layer is 0.5-5 mm, and the thickness of the bottom metal layer is 0.5-10 mm.

3. The preparation process of the gradient composite material for controlled nuclear fusion reactors according to claim 1 or 2, characterized in that, Includes the following steps: Step S1: Fix the substrate in the build chamber of the selective laser melting device; Step S2: The substrate is preheated and then a selective laser melting process is used to sequentially form an upper metal layer, a first gradient layer, an intermediate transition layer, a second gradient layer, and a bottom metal layer on the substrate to obtain a gradient composite material for a controlled nuclear fusion reactor. The upper metal layer is tungsten or a tungsten alloy, the intermediate transition layer is vanadium or a vanadium alloy, and the bottom metal layer is low-activation ferrite / martensitic steel. In the process of forming the first gradient layer, the powder feeding ratio is adjusted according to the designed mass percentage of each layer, and the continuous gradient transition of the composition is achieved by mixing the upper metal powder and the intermediate transition layer metal powder. When forming the second gradient layer, the powder feeding ratio is adjusted according to the designed mass percentage of each layer, and the continuous gradient transition of components is achieved by mixing the intermediate transition layer metal powder with the bottom layer metal powder.

4. The preparation process of the gradient composite material for controlled nuclear fusion reactors according to claim 3, characterized in that, The temperature of the preheating treatment in step S2 is 300~1200℃.

5. The preparation process of the gradient composite material for controlled nuclear fusion reactor according to claim 3, characterized in that, The laser power of the selective laser process in step S2 is 150-400W.

6. The preparation process of the gradient composite material for controlled nuclear fusion reactor according to claim 3, characterized in that, In step S2, the height of the powder layer is 20-30 μm.

7. The preparation process of the gradient composite material for controlled nuclear fusion reactors according to claim 3, characterized in that, The laser energy density used in forming the upper layer metal is not less than 250 J / mm 3 ; the laser energy density used in forming the intermediate transition layer metal is 70 to 120 J / mm 3 ; and the laser energy density used in forming the bottom layer metal is more than 190 J / mm 3 .

8. A method for connecting a gradient composite material to the first wall of the blanket in a controlled nuclear fusion reactor, characterized in that, It includes the gradient composite material for controlled nuclear fusion reactors as described in claim 1 or 2, wherein the bottom metal of the gradient composite material for controlled nuclear fusion reactors is connected to the first wall of the cladding.

9. The method for connecting the gradient composite material for a controlled nuclear fusion reactor to the first wall of the blanket as described in claim 8, characterized in that, Includes the following steps: S3: The gradient composite material for controlled nuclear fusion reactors is connected to the first wall of the blanket through a hot isostatic pressing process; the parameters of the hot isostatic pressing are: temperature 1050-1150℃, pressure 100-200MPa, and heat and pressure holding time 2-8h.

10. The method for connecting the gradient composite material to the first wall of the blanket in a controlled nuclear fusion reactor according to claim 9, characterized in that, Before performing the hot isostatic pressing process, the surfaces of the gradient composite material for the controlled nuclear fusion reactor and the first wall of the blanket must be cleaned and fixed by spot welding.

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