A thick tungsten coating, its preparation method, and a plasma-facing component

Abstract

This invention belongs to the technical field of thick tungsten coating production and preparation, and discloses a fine-grained reinforced thick tungsten coating, its preparation method, and a plasma-facing component. The thick tungsten coating provided by this invention has a fine columnar crystal microstructure, with an average columnar crystal width ≤50μm. This thick tungsten coating is prepared by introducing activated n-propylamine during chemical deposition and using a special treatment method involving alternating chemical vapor deposition and annealing processes. It exhibits excellent thermal conductivity and mechanical properties, and shows promising application prospects.

Description

Technical Field

[0001] This invention belongs to the technical field of thick tungsten coating production and preparation, and particularly relates to a fine-grained reinforced thick tungsten coating, its preparation method, and a plasma-facing component. Background Technology

[0002] Tungsten, with its high melting point, high thermal conductivity, and low sputtering rate, is one of the most promising candidates for plasma-facing components (PFMs). Future fusion reactors are characterized by long operating times, high heat fluxes, and harsh operating environments. Under the actual conditions of high-temperature plasma, prolonged high-flux heat loads can easily cause recrystallization degradation, plastic deformation, localized melting, and macroscopic cracks on the surface of pure tungsten PFMs, thus adversely affecting plasma impurity control and device safety. Furthermore, plasma-facing components (PFCs) in fusion devices often have complex shapes. Traditional tungsten materials have high room-temperature hardness and high brittleness, presenting challenges in processing, processing costs, and welding.

[0003] Directly preparing thick tungsten coatings on PFC components using methods such as vacuum plasma spraying, physical vapor deposition (PVD), and chemical vapor deposition (CVD) is one of the best solutions to address the difficulty of machining traditional tungsten materials. Among these, vacuum plasma spraying (VPS-W) is low-cost and efficient, but the resulting coating has a porous, layered structure and suffers from poor density, low thermal conductivity, and low purity (high content of impurities such as carbon and oxygen). Physical vapor deposition (PVD-W) produces columnar crystalline coatings with high density, but its low deposition rate makes it difficult to prepare coatings with thicknesses on the order of hundreds of micrometers. Chemical vapor deposition (CVD-W) produces columnar crystalline coatings and combines the advantages of high purity, high density, high thermal conductivity, and ease of preparing thick coatings.

[0004] CN103484830A discloses a method for preparing a thick tungsten coating material. This method employs chemical vapor deposition (CVD) to deposit a thick tungsten coating on a complex-shaped substrate by reducing tungsten hexafluoride with hydrogen. Specific conditions include: tungsten hexafluoride and hydrogen purities greater than 99.9% and 99.99%, respectively; a tungsten hexafluoride to hydrogen flow ratio of 1:2 to 1:5; a deposition temperature range of 500–700℃; and a deposition rate of 0.4–1.0 mm / h. The resulting thick tungsten coating achieves a chemical purity of over 99.99%, a thickness of 1–5 mm, a density of over 99%, and a room temperature thermal conductivity of over 170 W / (m·K), combining the advantages of high purity, high thickness, high density, and high room temperature thermal conductivity. However, the microstructure of this thick tungsten coating consists of coarse columnar crystals, with the average width of the columnar crystals continuously increasing along the coating growth direction. This results in poor mechanical properties of the coating, especially in the direction perpendicular to the coating growth direction. As a result, the coating is prone to cracking or brittle fracture and failure during the manufacturing, processing, transportation, installation, maintenance, repair and service of PFC components, which has significant limitations. Summary of the Invention

[0005] The primary objective of this invention is to address the problem of deteriorated mechanical properties in thick tungsten coatings obtained using conventional chemical vapor deposition, and to provide a thick tungsten coating with superior mechanical properties compared to conventional chemical vapor deposition tungsten materials.

[0006] A second objective of this invention is to provide a method for preparing a thick tungsten coating.

[0007] A third objective of the present invention is to provide a thick tungsten coating prepared by the above method.

[0008] A fourth objective of the present invention is to provide a plasma-facing component comprising the aforementioned thick tungsten coating.

[0009] After in-depth research, the inventors of this invention discovered that the mechanical properties of thick tungsten coatings are closely related to the average width of columnar crystals. During conventional chemical vapor deposition (CVD) tungsten grain growth, when the coating thickness is less than 100 μm, the tungsten grains expand simultaneously in both the transverse and longitudinal directions, without competition or preferential growth among them. Each crystal exhibits a uniformly sized, plate-like shape, exhibiting an equiaxed crystal microstructure. However, when the coating thickness exceeds 100 μm, the tungsten grains develop from a small equiaxed crystal structure along a columnar crystal microstructure with preferred orientation. The grain size shows a significant increasing trend, and this increase in grain size and the appearance of the columnar crystal microstructure adversely affect the material's mechanical properties.

[0010] Based on the problems existing in the prior art, the inventors of this invention, through extensive and in-depth research, creatively discovered that when activated n-propylamine is introduced into the tungsten hexafluoride and hydrogen reaction system as a carbon source gas during the growth process of a thick tungsten coating, it reacts with tungsten atoms in situ to generate tungsten dicarbide during the growth of columnar tungsten crystals. This leads to lattice distortion, disrupts the inheritance of columnar tungsten crystal growth, and interrupts the growth process of columnar tungsten crystals with preferred orientation. This achieves the effect of refining columnar crystals and improving mechanical properties, solving the problems of coarse columnar microstructure, continuously increasing width of columnar crystals along the coating growth direction, and low room temperature tensile strength perpendicular to the coating growth direction in conventional chemical vapor deposition tungsten materials. However, the introduction of activated n-propylamine causes lattice distortion, resulting in coating stress. The thick tungsten coating growth process can crack due to stress accumulation. Introducing annealing treatment in chemical vapor deposition can alleviate the coating stress caused by lattice distortion, ensuring that the thick tungsten coating does not crack due to stress accumulation during growth, thereby endowing the thick tungsten coating with good mechanical properties. Based on this, the present invention was completed.

[0011] Specifically, the tungsten coating provided by the present invention has a thickness of 2 mm or more, the tungsten coating has a fine columnar crystal microstructure, the average width of the columnar crystals in the fine columnar crystal microstructure is less than 50 μm, and the tensile strength of the tungsten coating perpendicular to the columnar crystal growth direction is more than 450 MPa.

[0012] In some specific embodiments, the thick tungsten coating has a density of 98.5% or higher, a room temperature thermal conductivity of 160 W / (m·K) or higher, and a room temperature hardness of 430 HV10 or higher.

[0013] In some specific embodiments, the thickness of the thick tungsten coating is 2 to 8 mm.

[0014] The method for preparing a thick tungsten coating provided by the present invention includes chemical vapor deposition of activated n-propylamine, tungsten hexafluoride and hydrogen on the surface of a substrate. The chemical vapor deposition includes multiple chemical vapor deposition stages performed sequentially, and an annealing stage is set after each chemical vapor deposition stage. The resulting coating is the thick tungsten coating.

[0015] In some specific embodiments, the activated n-propylamine is obtained by activating n-propylamine gas at 450–900°C for 0.2–1.0 h.

[0016] In some specific embodiments, during the chemical vapor deposition process, the flow rate ratio of hydrogen to tungsten hexafluoride is N = (1.5~5):1, and the flow rate ratio of activated n-propylamine to tungsten hexafluoride is M = (0.005~0.10):1.

[0017] In some specific embodiments, during the chemical vapor deposition process, the flow rate ratio of hydrogen to tungsten hexafluoride is N = (2-4):1, and the flow rate ratio of activated n-propylamine to tungsten hexafluoride is M = (0.01-0.08):1.

[0018] In some specific implementations, the conditions for different chemical vapor deposition stages independently include a temperature of 450–650°C, a pressure of 100–150 kPa, and an average deposition rate of 0.3–0.6 mm / h.

[0019] In some specific implementations, the conditions for different annealing stages independently include a temperature of 750–900°C and a time of 0.5–2.0 h.

[0020] In some specific implementations, each chemical vapor deposition stage is designed to achieve a thickness of 0.4–0.6 mm for the newly deposited layer.

[0021] In some specific embodiments, the number of chemical vapor deposition stages and annealing stages is 4 to 20.

[0022] In some specific embodiments, the flow ratio N of hydrogen to tungsten hexafluoride and the flow ratio M of activated n-propylamine to tungsten hexafluoride decrease in the plurality of chemical vapor deposition stages.

[0023] In some specific implementations, the flow rate ratio N of hydrogen to tungsten hexafluoride is [value missing] in the xth and x+1th chemical vapor deposition stages. x and N x+1 Satisfying relation N x -N x+1 =(0.02~0.2):1.

[0024] In some specific embodiments, the flow rate ratio M of activated n-propylamine and tungsten hexafluoride is [value missing] in the xth and x+1th chemical vapor deposition stages. x and M x+1 Satisfying relation M x -M x+1 =(0.0004~0.004):1.

[0025] The present invention also provides a thick tungsten coating prepared by the above method.

[0026] Furthermore, the present invention also provides a plasma-facing component including the aforementioned thick tungsten coating.

[0027] The beneficial effects of this invention are:

[0028] (1) The thick tungsten coating provided by the present invention has a fine columnar crystal microstructure, and the average width of the columnar crystals in the fine columnar crystal microstructure is ≤50μm. The special structure of the thick tungsten coating gives it good mechanical properties and thermal conductivity, especially a tensile strength of more than 450MPa perpendicular to the growth direction of the thick tungsten coating.

[0029] (2) The thick tungsten coating provided by this invention is prepared by introducing activated n-propylamine as a carbon source gas in chemical vapor deposition. The introduced activated n-propylamine can cause lattice distortion during the growth of columnar tungsten crystals, destroying the inheritance of columnar tungsten crystal growth. The growth process of columnar tungsten crystals with preferred orientation is interrupted, solving the problems of conventional chemical vapor deposition tungsten materials having a coarse columnar microstructure, a continuously increasing width of columnar crystals along the coating growth direction, and low room temperature tensile strength perpendicular to the coating growth direction. At the same time, a special processing technology is adopted—chemical vapor deposition is divided into multiple chemical vapor deposition stages, and each chemical vapor deposition stage Each process includes an annealing stage, employing a method of alternating chemical vapor deposition (CVD) and annealing. The annealing between two CVD processes prevents coating cracking caused by the introduction of activated n-propylamine during the thick tungsten coating growth process. Through the synergistic effect of the introduction of activated n-propylamine and the special method of alternating CVD and annealing, the resulting thick tungsten coating exhibits a fine and uniform columnar crystal microstructure, with an average columnar crystal width of no more than 50 μm, and the columnar crystal width remains essentially constant along its growth direction. This endows the thick tungsten coating with excellent thermal conductivity and mechanical properties, demonstrating promising application prospects.

[0030] In a preferred embodiment, when the flow ratio of hydrogen to tungsten hexafluoride and the flow ratio of activated n-propylamine to tungsten hexafluoride are controlled to decrease in multiple chemical vapor deposition stages, the next chemical vapor deposition can be matched with the annealed deposited layer, which is beneficial to improve the bonding force between different deposited layers, thereby more effectively improving the success rate of thick tungsten coating preparation. Attached Figure Description

[0031] Figure 1 This is a metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided in Embodiment 1 of the present invention.

[0032] Figure 2 Metallographic diagram of the longitudinal section of the fine-grained reinforced thick tungsten coating provided in Embodiment 1 of the present invention.

[0033] Figure 3 This is a metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided in Embodiment 2 of the present invention.

[0034] Figure 4 Metallographic diagram of the longitudinal section of the fine-grained reinforced thick tungsten coating provided in Embodiment 2 of the present invention.

[0035] Figure 5 This is a metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided in Embodiment 3 of the present invention.

[0036] Figure 6 Metallographic diagram of the longitudinal section of the fine-grained reinforced thick tungsten coating provided in Embodiment 3 of the present invention.

[0037] Figure 7 This is a metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided in Embodiment 4 of the present invention.

[0038] Figure 8 Metallographic diagram of the longitudinal section of the fine-grained reinforced thick tungsten coating provided in Embodiment 4 of the present invention.

[0039] Figure 9 This is a metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided in Embodiment 5 of the present invention.

[0040] Figure 10 Metallographic diagram of the longitudinal section of the fine-grained reinforced thick tungsten coating provided in Embodiment 5 of the present invention.

[0041] Figure 11 This is a metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided in Embodiment 6 of the present invention.

[0042] Figure 12 Metallographic diagram of the longitudinal section of the fine-grained reinforced thick tungsten coating provided in Embodiment 6 of the present invention.

[0043] Figure 13 This is a metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided in Embodiment 7 of the present invention.

[0044] Figure 14 Metallographic diagram of the longitudinal section of the fine-grained reinforced thick tungsten coating provided in Embodiment 7 of the present invention.

[0045] Figure 15 Metallographic structure of the fine-grained reinforced thick tungsten coating surface provided for Comparative Example 1.

[0046] Figure 16 Metallographic structure of a longitudinal section of a fine-grained reinforced thick tungsten coating provided for Comparative Example 1.

[0047] Figure 17 Metallographic diagram of the surface of the fine-grained reinforced thick tungsten coating provided for Comparative Example 2.

[0048] Figure 18 Metallographic structure of a longitudinal section of a fine-grained reinforced thick tungsten coating provided for Comparative Example 2. Detailed Implementation

[0049] In this invention, the thick tungsten coating has a fine columnar crystal microstructure, wherein the average width of the columnar crystals in the fine columnar crystal microstructure is less than 50 μm (e.g., 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm or any value between them), and the tensile strength of the thick tungsten coating perpendicular to the columnar crystal growth direction is greater than 450 MPa (e.g., 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa or any value between them). The special structure of this thick tungsten coating endows it with excellent mechanical and thermal conductivity properties.

[0050] In some specific embodiments, the density of the thick tungsten coating is 98.5% or higher (e.g., 98.5%, 98.8%, 99.0%, 99.2%, 99.5%, 99.8% or any value between them), the room temperature thermal conductivity is 160 W / (m·K) or higher (e.g., 160, 165, 170, 175, 180, 185, 190, 195, 200 W / (m·K) or any value between them), and the room temperature hardness is 430 HV10 or higher (e.g., 430, 435, 440, 445, 450, 455, 460, 465, 470, 475, 480 HV10 or any value between them).

[0051] In some specific embodiments, the thickness of the thick tungsten coating is 2 mm or more, more preferably 2 to 8 mm, such as 2 mm, 4 mm, 6 mm, 8 mm or any value between them.

[0052] In this invention, the preparation method of the thick tungsten coating includes chemical vapor deposition of activated n-propylamine, tungsten hexafluoride, and hydrogen on the surface of a substrate, and the resulting coating is the thick tungsten coating. Specifically, the tungsten hexafluoride reacts with hydrogen to generate metallic tungsten, which is deposited on the substrate surface. During deposition, some of the metallic tungsten reacts with activated n-propylamine in situ to generate tungsten dicarbide, thus forming a thick tungsten coating with metallic tungsten as the main component (purity above 99.6%) and containing a small amount of tungsten dicarbide (purity below 0.02%).

[0053] In this invention, the activated n-propylamine is preferably obtained by activating n-propylamine gas at 450–900°C for 0.2–1.0 h, which exhibits high reactivity with metallic tungsten. In some specific embodiments, the activation temperature of n-propylamine can be 450°C, 470°C, 500°C, 525°C, 550°C, 600°C, 700°C, 800°C, 900°C, or any value between them, and the activation time can be 0.2 h, 0.4 h, 0.5 h, 0.7 h, 1.0 h, or any value between them.

[0054] In this invention, the purity of the activated n-propylamine is preferably not less than 99.0%, specifically it can be 99.0%, 99.1%, 99.2%, 99.5%, 99.8%, 99.9%, 100.0%, or any value between them. The purity of the tungsten hexafluoride is preferably 99.0% to 99.999%, specifically it can be 99%, 99.5%, 99.9%, 99.99%, 99.999%, or any value between them. The purity of the hydrogen is preferably 99.0% to 99.999%, specifically it can be 99%, 99.5%, 99.9%, 99.99%, 99.999%, or any value between them.

[0055] In this invention, the chemical vapor deposition is a conventional method used in the field of thin film preparation, and it can be, but is not limited to, one or more of low-pressure chemical vapor deposition, atmospheric pressure chemical vapor deposition, and plasma-assisted chemical vapor deposition. In some preferred embodiments, the chemical vapor deposition is selected as atmospheric pressure chemical vapor deposition.

[0056] In this invention, the chemical vapor deposition includes one or more sequential chemical vapor deposition stages. In some specific embodiments, the flow rate ratio N of hydrogen to tungsten hexafluoride in different chemical vapor deposition stages is independently preferably (1.5 to 5):1, at which the tungsten hexafluoride can react sufficiently with the hydrogen. More specifically, the flow rate ratio N of hydrogen to tungsten hexafluoride in a single chemical vapor deposition stage can be, but is not limited to, 1.5:1, 1.7:1, 1.9:1, 2:1, 2.5:1, 3:1, 4:1, 5:1, or any value between them. In some more preferred embodiments, the flow rate ratio N of hydrogen to tungsten hexafluoride is (2 to 4):1. In some specific embodiments, the flow rate ratio M of activated n-propylamine and tungsten hexafluoride in different chemical vapor deposition stages is preferably (0.005–0.1):1. This flow rate ratio allows activated n-propylamine to fully exert its role in disrupting the growth inheritance of columnar tungsten crystals without introducing excessive carbon into the thick tungsten coating, thus affecting its performance. More specifically, the flow rate ratio M of activated n-propylamine and tungsten hexafluoride in a single chemical vapor deposition stage can be 0.005:1, 0.01:1, 0.02:1, 0.05:1, 0.07:1, 0.08:1, 0.1:1, or any value between them. In some more preferred embodiments, the flow rate ratio M of activated n-propylamine and tungsten hexafluoride in different chemical vapor deposition stages is independently (0.01–0.08):1.

[0057] In some specific embodiments, the temperature in each chemical vapor deposition stage is preferably independently between 450 and 650°C, within which a thick tungsten coating with a better fine columnar crystal microstructure can be obtained. More specifically, the temperature in a single chemical vapor deposition stage can be 450°C, 460°C, 480°C, 500°C, 530°C, 550°C, 600°C, 650°C, or any value between them.

[0058] In some specific embodiments, the pressure in different chemical vapor deposition stages is preferably 100–150 kPa, within which a thick tungsten coating with a better fine columnar crystal microstructure can be obtained. More specifically, the pressure in a single chemical vapor deposition stage can be 100 kPa, 101 kPa, 110 kPa, 125.4 kPa, 130 kPa, 140 kPa, 150 kPa, or any value between them.

[0059] In some specific embodiments, the average deposition rate in different chemical vapor deposition stages is preferably 0.3 to 0.6 mm / h independently. More specifically, the average deposition rate in a single chemical vapor deposition stage can be 0.3 mm / h, 0.4 mm / h, 0.5 mm / h, 0.6 mm / h, or any value between them.

[0060] In some specific embodiments, the time in different chemical vapor deposition stages is preferably 0.5 to 2.0 h independently. More specifically, the time in a single chemical vapor deposition stage can be 0.5 h, 0.6 h, 0.8 h, 1.0 h, 1.5 h, 1.8 h, 2.0 h, or any value between them.

[0061] As mentioned above, the introduction of activated n-propylamine can induce lattice distortion during the growth of columnar crystals, disrupting the inheritance of tungsten columnar crystal growth, thereby refining the microstructure of the columnar crystals and endowing the thick tungsten coating with good mechanical properties. However, the introduction of activated n-propylamine can also cause lattice distortion, resulting in coating stress. The thick tungsten coating may crack due to stress accumulation during growth. Introducing annealing into chemical vapor deposition (CVD) can mitigate the coating stress caused by lattice distortion, ensuring that the thick tungsten coating does not crack due to stress accumulation during growth. Based on this, the CVD process is configured to include multiple sequential CVD stages, with an annealing stage following each CVD stage.

[0062] In this invention, the temperature of different annealing stages is preferably 750–900°C, and the time is preferably 0.5–2.0 h. At these temperatures and times, the uniformity of the fine columnar crystal microstructure can be improved without changing the grain size. In some specific embodiments, the temperature of a single annealing stage can be 750°C, 760°C, 800°C, 810°C, 830°C, 860°C, 900°C, or any value between them; the time can be 0.5 h, 0.8 h, 1.0 h, 1.3 h, 1.5 h, 1.8 h, 2.0 h, or any value between them.

[0063] In this invention, each chemical vapor deposition (CVD) stage preferably proceeds to the annealing stage after the thickness of the newly deposited layer reaches 0.4–0.6 mm. At this thickness, a relatively complete fine columnar crystal microstructure is formed, with a small average width of the fine columnar crystals. In some specific embodiments, the thickness of the newly deposited layer in each CVD stage is independently 0.4 mm, 0.5 mm, 0.6 mm, or any value between them. In specific embodiments, with a fixed flow ratio of reactive hydrogen, n-propylamine, and tungsten hexafluoride, the thickness of the newly deposited layer in each CVD stage is controlled by controlling the deposition rate and deposition time of each CVD stage.

[0064] In some specific embodiments, thick tungsten coatings of different thicknesses are prepared by varying the number of chemical vapor deposition (CVD) stages and annealing stages. The number of CVD stages and annealing stages is selected from 4 to 50, specifically 4, 5, 10, 20, 50, or any integer value between them. In some more preferred embodiments, the number of CVD stages and annealing stages is preferably 4 to 20.

[0065] In this invention, the introduction of the annealing stage disrupts the continuity of chemical vapor deposition, resulting in the formation of multiple deposition layers within the thick tungsten coating. This leads to low adhesion between different deposition layers. Based on a deep understanding of multiple processes in the growth of thick tungsten coatings, including grain size growth and deposition formation, the inventors, through comprehensive consideration and extensive experimentation, discovered that by controlling the flow ratio of hydrogen to tungsten hexafluoride and the activated carbon source gas to tungsten hexafluoride to exhibit a decreasing trend, the deposition rate of the coating can be slightly reduced without altering the coating composition and grain size. This, combined with the stress-relieved deposition layers after online annealing, is beneficial for improving the adhesion between different deposition layers, ensuring the successful preparation of a fine-grained reinforced thick tungsten coating. Therefore, the flow ratios N (hydrogen to tungsten hexafluoride) and M (activated n-propylamine to tungsten hexafluoride) in multiple chemical vapor deposition stages are set to exhibit a decreasing trend to improve the adhesion between different deposition layers.

[0066] In some specific embodiments, the decreasing trend of the hydrogen to tungsten hexafluoride flow rate ratio N in the multiple chemical vapor deposition stages is exemplified as follows: in the x-th and x+1-th chemical vapor deposition stages, the hydrogen to tungsten hexafluoride flow rate ratio N... x and N x+1 Satisfying relation N x -N x+1 = (0.02~0.2):1; that is, in two adjacent chemical vapor deposition stages, the flow ratio N of hydrogen and tungsten hexafluoride in the later chemical vapor deposition stage is lower than that in the previous chemical vapor deposition stage by 0.02:1, 0.05:1, 0.08:1, 0.10:1, 0.15:1, 0.20:1 or any value between them.

[0067] In some specific embodiments, the decreasing trend of the flow rate ratio M of activated n-propylamine to tungsten hexafluoride in the multiple chemical vapor deposition stages is exemplified as follows: in the x-th and x+1-th chemical vapor deposition stages, the flow rate ratio M of activated n-propylamine to tungsten hexafluoride is... x and M x+1 Satisfying relation M x -M x+1 = (0.0004~0.004):1; that is, in two adjacent chemical vapor deposition stages, the flow ratio M of activated n-propylamine and tungsten hexafluoride in the later chemical vapor deposition stage is lower than that in the previous chemical vapor deposition stage by 0.0004:1, 0.0008:1, 0.001:1, 0.002:1, 0.003:1, 0.004:1 or any value between them.

[0068] In this invention, the thick tungsten coating prepared by the above method has a fine and uniform columnar crystal microstructure. The average width of the columnar crystals in this microstructure is ≤50μm, and the width of the columnar crystals remains essentially constant along the growth direction of the coating. The thick tungsten coating has a density ≥98.5%, a room temperature thermal conductivity ≥160W / (m·K) along the coating growth direction, a room temperature hardness ≥430HV10, and a room temperature tensile strength ≥450MPa, exhibiting excellent thermal conductivity and mechanical properties.

[0069] In this invention, the above method is applied to the production of plasma-facing components in order to obtain plasma-facing components including the thick tungsten coating described above. These plasma-facing components can be well applied to future fusion reactor devices with characteristics such as long operating time, large heat flux, and harsh service environment, and have good application prospects.

[0070] The embodiments of the present invention are described in detail below. These embodiments are intended to explain the present invention and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0071] Example 1

[0072] This embodiment illustrates the preparation method of the fine-grained reinforced thick tungsten coating provided by the present invention. Tungsten hexafluoride (99.9% purity), hydrogen (99.5% purity), and n-propylamine (99.5% purity) are used as raw materials, and copper is selected as the substrate material. The specific steps include:

[0073] (1) Pre-activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 650°C for 0.5 h to obtain activated n-propylamine gas.

[0074] (2) Formation of a thick tungsten coating: Hydrogen, activated n-propylamine gas, and tungsten hexafluoride gas were mixed and subjected to multiple alternating chemical vapor deposition (CVD) and annealing treatments on the surface of a copper substrate. After each CVD deposition, the substrate was annealed at 800°C for 1 hour in a hydrogen atmosphere. After annealing, the temperature was lowered to 580°C before the next CVD deposition was performed, resulting in a thick tungsten coating. The specific conditions for CVD deposition are shown in Table 1.

[0075] Table 1.

[0076]

[0077] The final tungsten coating thickness obtained in this embodiment is 6.2 mm. The surface metallographic structure and longitudinal section metallographic structure of this tungsten coating are as follows: Figure 1 and Figure 2 As shown, the thick tungsten coating is of good quality, with high density and a microstructure consisting of fine and uniform columnar crystals. The width of the columnar crystals remains basically unchanged along the direction of coating growth.

[0078] Example 2

[0079] This embodiment illustrates the preparation method of the fine-grained reinforced thick tungsten coating provided by the present invention. Tungsten hexafluoride (99.99% purity), hydrogen (99.9% purity), and n-propylamine (99.0% purity) are used as raw materials, and copper is selected as the substrate material. The specific steps include:

[0080] (1) Pre-activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 900°C for 0.2 h to obtain activated n-propylamine gas.

[0081] (2) Formation of a thick tungsten coating: A mixture of hydrogen, activated n-propylamine gas, and tungsten hexafluoride gas was applied to the surface of a copper substrate using alternating chemical vapor deposition (CVD) and annealing processes. After each CVD deposition, the substrate was annealed at 900°C for 0.5 hours in a hydrogen atmosphere. After annealing, the temperature was lowered to 630°C before the next CVD deposition was performed, resulting in a thick tungsten coating. The specific conditions for CVD deposition are shown in Table 2.

[0082] Table 2.

[0083]

[0084] The final thickness of the tungsten coating obtained in this embodiment is 4.2 mm. The surface metallographic structure and longitudinal section metallographic structure of the tungsten coating are as follows: Figure 3 and Figure 4 As shown, the thick tungsten coating is of good quality, with high density and a microstructure consisting of fine and uniform columnar crystals. The width of the columnar crystals remains basically unchanged along the direction of coating growth.

[0085] Example 3

[0086] This embodiment illustrates the preparation method of the fine-grained reinforced thick tungsten coating provided by the present invention. Tungsten hexafluoride (99.5% purity), hydrogen (99.99% purity), and n-propylamine (99.9% purity) are used as raw materials, and copper is selected as the substrate material. The specific steps include:

[0087] (1) Pre-activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 750°C for 0.4 h to obtain activated n-propylamine gas.

[0088] (2) Formation of a thick tungsten coating: Hydrogen, activated n-propylamine gas, and tungsten hexafluoride gas were mixed and subjected to multiple alternating chemical vapor deposition (CVD) and annealing treatments on the surface of a copper substrate. After each CVD deposition, the substrate was annealed at 750°C for 2.0 h in a hydrogen atmosphere. After annealing, the temperature was lowered to 490°C before the next CVD deposition was performed, resulting in a thick tungsten coating. The specific conditions for CVD deposition are shown in Table 3.

[0089] Table 3.

[0090]

[0091] The final tungsten coating thickness obtained in this embodiment is 4.9 mm. The surface metallographic structure and longitudinal section metallographic structure of this tungsten coating are as follows: Figure 5 and Figure 6 As shown, the thick tungsten coating is of good quality and has high density. Its microstructure consists of fine and uniform columnar crystals, and the width of the columnar crystals remains basically unchanged along the growth direction of the coating.

[0092] Example 4

[0093] This embodiment illustrates the preparation method of the fine-grained reinforced thick tungsten coating provided by the present invention. Tungsten hexafluoride (99.9% purity), hydrogen (99.5% purity), and n-propylamine (99.5% purity) are used as raw materials, and copper is selected as the substrate material. The specific steps include:

[0094] (1) Pre-activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 650°C for 0.5 h to obtain activated n-propylamine gas.

[0095] (2) Formation of a thick tungsten coating: A mixture of hydrogen, activated n-propylamine gas, and tungsten hexafluoride gas was applied to the surface of a copper substrate using alternating chemical vapor deposition (CVD) and annealing processes. After each CVD deposition, the substrate was annealed at 800°C for 1 hour in a hydrogen atmosphere. After annealing, the temperature was lowered to 580°C before the next CVD deposition was performed, resulting in a thick tungsten coating. The specific conditions for CVD deposition are shown in Table 4.

[0096] Table 4.

[0097]

[0098] The final tungsten coating thickness obtained in this embodiment is 6.3 mm. The surface metallographic structure and longitudinal section metallographic structure of this tungsten coating are as follows: Figure 7 and Figure 8 As shown, the thick tungsten coating is of good quality, with high density and a microstructure consisting of fine and uniform columnar crystals. The width of the columnar crystals remains basically unchanged along the direction of coating growth.

[0099] Example 5

[0100] This embodiment illustrates the preparation method of the fine-grained reinforced thick tungsten coating provided by the present invention. Tungsten hexafluoride (99.5% purity), hydrogen (99.9% purity), and n-propylamine (99.0% purity) are used as raw materials, and copper is selected as the substrate material. The specific steps include:

[0101] (1) Pre-activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 750°C for 0.4 h to obtain activated n-propylamine gas.

[0102] (2) Formation of a thick tungsten coating: A mixture of hydrogen, activated n-propylamine gas, and tungsten hexafluoride gas was applied to the surface of a copper substrate using alternating chemical vapor deposition (CVD) and annealing processes. After each CVD deposition, the substrate was annealed at 750°C for 1.5 hours in a hydrogen atmosphere. After annealing, the temperature was lowered to 530°C before the next CVD deposition was performed, resulting in a thick tungsten coating. The specific conditions for CVD deposition are shown in Table 5.

[0103] Table 5.

[0104]

[0105] The final tungsten coating thickness obtained in this embodiment is 6.8 mm. The surface metallographic structure and longitudinal section metallographic structure of this tungsten coating are as follows: Figure 9 and Figure 10 As shown, the thick tungsten coating is of good quality and has high density. Its microstructure consists of fine and uniform columnar crystals, and the width of the columnar crystals remains basically unchanged along the growth direction of the coating.

[0106] Example 6

[0107] This embodiment illustrates the preparation method of the fine-grained reinforced thick tungsten coating provided by the present invention. Tungsten hexafluoride (99.9% purity), hydrogen (99.5% purity), and n-propylamine (99.5% purity) are used as raw materials, and copper is selected as the substrate material. The specific steps include:

[0108] (1) Pre-activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 650°C for 0.5 h to obtain activated n-propylamine gas.

[0109] (2) Formation of a thick tungsten coating: A mixture of hydrogen, activated n-propylamine gas, and tungsten hexafluoride gas was applied to the surface of a copper substrate using alternating chemical vapor deposition (CVD) and annealing processes. After each CVD deposition, the substrate was annealed at 800°C for 1 hour in a hydrogen atmosphere. After annealing, the temperature was lowered to 580°C before the next CVD deposition was performed, resulting in a thick tungsten coating. The specific conditions for CVD deposition are shown in Table 6.

[0110] Table 6.

[0111]

[0112] The final tungsten coating thickness obtained in this embodiment is 5.4 mm. The surface metallographic structure and longitudinal section metallographic structure of this tungsten coating are as follows: Figure 11 and Figure 12 As shown, the thick tungsten coating is of good quality, with high density and a microstructure consisting of fine and uniform columnar crystals. The width of the columnar crystals remains basically unchanged along the direction of coating growth.

[0113] Example 7

[0114] This embodiment illustrates the preparation method of the fine-grained reinforced thick tungsten coating provided by the present invention. Tungsten hexafluoride (99.9% purity), hydrogen (99.5% purity), and n-propylamine (99.5% purity) are used as raw materials, and copper is selected as the substrate material. The specific steps include:

[0115] (1) Activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 650°C for 0.5 h to obtain activated n-propylamine gas.

[0116] (2) Formation of a thick tungsten coating: Hydrogen, activated n-propylamine gas, and tungsten hexafluoride gas were mixed and subjected to multiple alternating chemical vapor deposition (CVD) and annealing treatments on the surface of a copper substrate. After each CVD deposition, the substrate was annealed at 800°C for 1 hour in a hydrogen atmosphere. After annealing, the temperature was lowered to 580°C before the next CVD deposition was performed, resulting in a thick tungsten coating. The specific conditions for CVD deposition are shown in Table 7.

[0117] Table 7.

[0118]

[0119] The final tungsten coating thickness obtained in this embodiment is 6.5 mm. The surface metallographic structure and longitudinal section metallographic structure of this tungsten coating are as follows: Figure 13 and Figure 14 As shown, the thick tungsten coating is of good quality, with high density and a microstructure consisting of fine and uniform columnar crystals. The width of the columnar crystals remains basically unchanged along the direction of coating growth.

[0120] Comparative Example 1

[0121] This comparative example provides a method for preparing a reference thick tungsten coating, using tungsten hexafluoride (99.9% purity), hydrogen (99.5% purity), and n-propylamine (99.5% purity) as raw materials, and selecting copper as the substrate material. The method specifically includes the following steps:

[0122] (1) Pre-activation of n-propylamine: n-propylamine was heated and evaporated at 60°C to obtain n-propylamine gas. The n-propylamine gas was then activated in a preheating activation device at 650°C for 0.5 h to obtain activated n-propylamine gas.

[0123] (2) Hydrogen, activated n-propylamine gas and tungsten hexafluoride were mixed according to a flow ratio of 2.8:0.051:1 and chemical vapor deposition was carried out on a copper surface at a surface temperature of 580℃. The deposition pressure was 100kPa, the time was 15h, and the average deposition rate was 0.59mm / h, resulting in a thick tungsten coating.

[0124] The comparative example ultimately obtained a thick tungsten coating with a thickness of 8.9 mm. The surface metallographic structure and longitudinal section metallographic structure of this thick tungsten coating are as follows: Figure 15 and Figure 16 As shown, although the obtained thick tungsten coating has high density and a microstructure of fine columnar crystals, cracks appear on both the surface and longitudinal section of the thick tungsten coating, and the uniformity of the columnar crystal width is poor.

[0125] Comparative Example 2

[0126] This comparative example provides a method for preparing a reference thick tungsten coating, using tungsten hexafluoride (99.9% purity) and hydrogen (99.5% purity) as raw materials, and selecting copper as the substrate material. The method specifically includes the following steps:

[0127] A mixture of hydrogen and tungsten hexafluoride gas was used to perform alternating chemical vapor deposition (CVD) and annealing processes on a copper substrate. After each CVD cycle, the substrate was annealed at 800°C for 1 hour in a hydrogen atmosphere. After annealing, the temperature was lowered to 580°C before the next CVD cycle, resulting in a thick tungsten coating. The specific CVD conditions are shown in Table 8.

[0128] Table 8.

[0129]

[0130]

[0131] The comparative example ultimately obtained a tungsten coating with a thickness of 7.1 mm. The surface metallographic structure and longitudinal section metallographic structure of this tungsten coating are as follows: Figure 17 and Figure 18 As shown, the obtained thick tungsten coating has poor uniformity and its microstructure consists of wide columnar crystals, with the width of the columnar crystals gradually increasing along the direction of coating growth.

[0132] Test case

[0133] This test example illustrates the relevant performance of the thick tungsten coatings in Examples 1-7 and Comparative Examples 1 and 2. The specific test methods are as follows:

[0134] (1) Columnar crystal width: The grain size of the thick tungsten coating growth surface was tested in accordance with the standard "ASTM E112-2013(2021) Standard Test Method for Determination of Average Grain Size".

[0135] (2) Density: The density of the thick tungsten coating was tested using the Archimedes' water displacement method, referring to the standard ASTM B311-2008 "Standard Test Method for Density of Powder Metallurgical Materials with Porosity Less Than 2%" (the theoretical density of pure tungsten was taken as 19.30 g / cm³). 3 count).

[0136] (3) Purity: Referring to the standards GB / T 4324.27-2012 Tungsten Chemical Analysis Methods Part 27: Determination of Carbon Content by High Frequency Combustion Infrared Absorption Method and YS / T901-2013 High Purity Tungsten Chemical Analysis Method: Determination of Trace Impurity Elements by Glow Discharge Mass Spectrometry, the carbon content of the thick tungsten coating was analyzed by a carbon analyzer, and the non-gaseous element impurity content of the thick tungsten coating was analyzed by a glow discharge mass spectrometer (GDMS).

[0137] (4) Room temperature thermal conductivity: The room temperature thermal conductivity of the thick tungsten coating was tested according to the standard GB / T22588-2008 "Measuring Thermal Diffusion Coefficient or Thermal Conductivity by Flash Method". Pure tungsten standard samples were used; the sample surface was polished with sandpaper of 1800 grit or higher; the digital model used Cowan+ pulse correction. The room temperature thermal conductivity test surface was taken from the upper and lower surfaces along the growth direction of the columnar crystals in the thick tungsten coating.

[0138] (5) Room temperature Vickers hardness: The thick tungsten coating was tested using a Vickers hardness tester according to the standard GB / T 4340.1-2009 Metallic Materials Vickers Hardness Test Part 1: Test Method. HV10 was selected, and the test force holding time was 10s. The room temperature Vickers hardness test surface was taken from the surface of the thick tungsten coating.

[0139] (6) Room temperature tensile strength: The room temperature tensile strength of the thick tungsten coating was tested using a universal testing machine in accordance with the standard GB / T 228.1-2010 Metallic Materials Tensile Test Part 1: Room Temperature Test Method. The tensile direction was perpendicular to the growth direction of the columnar crystals.

[0140] The test results are shown in Table 9.

[0141] Table 9.

[0142]

[0143] The test results show that the thick tungsten coating obtained by the method provided in this invention has a fine columnar crystal microstructure, and the width of the columnar crystals remains basically unchanged along the growth direction of the coating. It has excellent thermal conductivity and mechanical properties and has good application prospects.

[0144] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a thick tungsten coating, characterized in that, The method includes performing chemical vapor deposition of activated n-propylamine, tungsten hexafluoride and hydrogen on the surface of a substrate. The chemical vapor deposition includes a plurality of chemical vapor deposition stages carried out in sequence, and an annealing stage is provided after each chemical vapor deposition stage. The obtained coating is the thick tungsten coating; The activated n-propylamine is obtained by activating n-propylamine gas at 450 - 900 °C for 0.2 - 1.0 h; During the chemical vapor deposition process, the flow rate ratio N of hydrogen to tungsten hexafluoride is (2 - 4):1, and the flow rate ratio M of activated n-propylamine to tungsten hexafluoride is (0.01 - 0.08):1; In the x-th and (x + 1)-th chemical vapor deposition stages, the flow rate ratio N of hydrogen to tungsten hexafluoride x and N x+1 satisfies the relation N x - N x+1 = (0.02~0.2):1, and the flow rate ratio M of activated n-propylamine to tungsten hexafluoride x and M x+1 satisfies the relation M x - M x+1 = (0.0004~0.004):1; The conditions of different chemical vapor deposition stages independently include a temperature of 450 - 650 °C, a pressure of 100 - 150 kPa, and an average deposition rate of 0.3 - 0.6 mm / h; The conditions of different annealing stages independently include a temperature of 750 - 900 °C and a time of 0.5 - 2.0 h; Each chemical vapor deposition stage is based on making the thickness of the newly deposited layer reach 0.4 - 0.6 mm.

2. The method for preparing a thick tungsten coating according to claim 1, characterized in that, The number of the chemical vapor deposition stages and the annealing stages is 4 - 20.

3. The thick tungsten coating prepared by the method according to claim 1 or 2, characterized in that The thickness of the thick tungsten coating is 2 mm or more. The thick tungsten coating has a fine columnar crystal microstructure. The average width of the columnar crystals in the fine columnar crystal microstructure is 50 μm or less. The tensile strength of the thick tungsten coating perpendicular to the columnar crystal growth direction is 450 MPa or more.

4. The thick tungsten coating according to claim 3, wherein The density of the thick tungsten coating is 98.5% or more, the room temperature thermal conductivity is 160 W / (m·K) or more, and the room temperature hardness is 430 HV10 or more.

5. The thick tungsten coating according to claim 3, wherein The thickness of the thick tungsten coating is 2 - 8 mm.

6. A plasma-facing component, characterized in that, The plasma-facing component includes the thick tungsten coating according to any one of claims 3 - 5.

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