Molybdenum coating and preparation method thereof

Abstract

The invention discloses a molybdenum coating and a preparation method thereof.The preparation method comprises the steps that a base body is subjected to surface roughening treatment, the base body subjected to surface roughening treatment is cleaned, and a substrate is obtained; mounting parameters of explosion spraying equipment are obtained, and the substrate is mounted on the explosion spraying equipment according to the mounting parameters; spraying parameters of the explosion spraying equipment are obtained, preset powder is fed into the explosion spraying equipment according to the spraying parameters, equipment parameters of the explosion spraying equipment are regulated and controlled, and the spraying parameters comprise the oxygen-fuel ratio, the cavity filling rate, the nitrogen dilution amount and the powder feeding rate; and the explosion spraying equipment is controlled to ignite, so that the explosion spraying equipment impacts the preset powder on the surface of the base body in a softened state to form the molybdenum coating. According to the method, the impurity content in the coating can be remarkably reduced, the molybdenum coating with high purity, high density and good combination is obtained, the difficulty is low, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the technical field of explosive spraying, specifically relating to a molybdenum coating and its preparation method. Background Technology

[0002] The primary mirror is a crucial optical component within the vacuum chamber of a nuclear fusion device. Directly facing the plasma, it collects and reflects the light signals emitted by the plasma, and its performance directly determines the reliability of the diagnostic system. This component operates in an extremely harsh environment, enduring high surface heat loads, intense particle and neutron radiation, and impurity deposition. The extremely high steady-state and transient heat loads far exceed the material's own heat dissipation limits, necessitating a highly efficient cooling system that rapidly dissipates heat through internal channels to control thermal stress and prevent melting, deformation, or cracking of the mirror surface. Effective operation of the cooling system requires a defect-free and robust connection between the mirror and the heat sink; that is, the primary mirror precursor and the substrate must possess excellent bonding properties.

[0003] Molybdenum and its alloys possess properties such as high melting point, high thermal conductivity, and low sputtering rate, combining durability and economy. They are commonly used materials for laser mirrors and are also suitable for the fabrication of the first mirror in nuclear fusion devices. However, molybdenum is a difficult-to-machine material, making it challenging and costly to bond tightly to a substrate. Therefore, there is an urgent need for a simple and low-cost method to prepare a molybdenum coating that bonds tightly to a substrate. Summary of the Invention

[0004] To achieve a high-strength bond between the first mirror and the substrate, and to address the issues of easy oxidation and high impurity content in the coating during explosive spraying, this invention provides a molybdenum coating for the first mirror precursor of a nuclear fusion device and its preparation method. This method effectively suppresses the formation of oxides and carbides in the coating, significantly reduces impurity content, and improves coating purity. The molybdenum coating prepared by this method has a dense structure, high bonding strength, and good thermal conductivity, offering high cost-effectiveness and suitability for manufacturing the first mirror precursor of future commercial nuclear fusion devices. It should be noted that the scope of protection of this patent is limited to the preparation process of the first mirror precursor and does not include subsequent polishing and mirror-forming steps.

[0005] This invention provides a method for preparing a molybdenum coating, the method comprising: The substrate is roughened on the surface and then cleaned to obtain the base material. Obtain the installation parameters of the explosive spraying equipment, and install the substrate on the explosive spraying equipment according to the installation parameters. The installation parameters include the spraying distance, which is in the range of 30-50mm. The process involves acquiring the spraying parameters of the explosive spraying equipment, feeding a preset powder into the explosive spraying equipment according to the spraying parameters, and adjusting the equipment parameters of the explosive spraying equipment. The spraying parameters include the oxygen-fuel ratio, chamber filling rate, nitrogen dilution rate, and powder feeding rate. The oxygen-fuel ratio ranges from 1.40 to 1.70, the chamber filling rate ranges from 20% to 40%, the nitrogen dilution rate ranges from 6.00% to 10.00%, and the powder feeding rate ranges from 80 to 120 mg / s. The preset powder includes molybdenum powder or molybdenum alloy powder. The explosive spraying equipment is controlled to ignite so that it impacts the preset powder in a softened state onto the substrate surface to form a molybdenum coating.

[0006] In some embodiments, the particle size range of the preset powder is 5-20 μm.

[0007] In some embodiments, the spraying frequency of the explosive spraying equipment is in the range of 7-10 Hz.

[0008] In some embodiments, the spray gun movement speed of the explosive spraying equipment ranges from 8 to 10 mm / s.

[0009] In some embodiments, the explosion temperature generated when the explosive spraying equipment is ignited ranges from 2500°C to 3200°C.

[0010] In some embodiments, the step of mounting the substrate on the explosive spraying equipment according to the mounting parameters, the mounting parameters including the spraying distance, includes: Based on the spraying distance, adjust the distance between the spray gun nozzle of the explosive spraying equipment and the substrate surface to determine the installation position of the substrate; The substrate is mounted on the explosive spraying equipment at the specified mounting location.

[0011] In some embodiments, the spraying equipment includes a gas shut-off valve and a powder feeder. The step of feeding preset powder into the explosive spraying equipment according to the spraying parameters and the equipment parameters of the explosive spraying equipment include: Based on the spraying parameters, determine the powder feeding parameters and operating mode of the spraying equipment; According to the operating mode, the equipment parameters of the gas throttle valves corresponding to each gas are adjusted; The equipment parameters of the powder feeder are adjusted according to the powder feeding parameters.

[0012] In some embodiments, adjusting the equipment parameters of the gas throttle valves corresponding to each gas according to the operating mode includes: According to the operating mode, the orifice diameter and opening duration of the gas throttle valve corresponding to the fuel gas are adjusted. The orifice diameter and opening duration of the gas throttle valve corresponding to oxygen are adjusted; and, The orifice diameter and opening duration of the gas throttle valve corresponding to nitrogen are adjusted.

[0013] In some embodiments, the substrate comprises low-activation steel or copper water-cooled components.

[0014] On the other hand, the present invention also provides a molybdenum coating, which is prepared by using the above-described preparation method.

[0015] The beneficial effects of this invention are: (1) A molybdenum coating suitable for the first mirror precursor of a nuclear fusion device and its preparation method are provided. The method forms the first mirror precursor by explosively spraying a molybdenum coating on a low-activation steel or copper water-cooled component, avoiding the bottleneck that the whole molybdenum material is difficult to directly process into a complex cooling structure, significantly reducing the manufacturing cost, and has high process efficiency and the potential for mass production.

[0016] (2) The selected molybdenum coating has excellent thermophysical properties, with a thermal conductivity of up to 142 W / (m·K). Its thermal expansion properties are well matched with commonly used substrate materials, which can effectively conduct high heat loads and withstand transient thermal shock and neutron irradiation environment, thereby ensuring the stability of the first mirror under extreme working conditions and extending its service life.

[0017] (3) By precisely controlling the process parameters of the explosive spraying, the oxidation and carbonization reactions of molybdenum during the spraying process were effectively suppressed, resulting in a coating with low impurity content and dense structure. The coating exhibits high thermal conductivity and low oxide content, which can meet the stringent requirements of efficient heat dissipation and material purity for the first mirror of nuclear fusion. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic flowchart illustrating a method for preparing a molybdenum coating according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an explosive spraying device provided in an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that, when used in this specification and the claims of the accompanying drawings, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0022] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0023] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0024] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] The first mirror in a nuclear fusion device must operate in extremely harsh environments, including enduring high surface heat loads, intense particle and neutron radiation, and impurity deposition. The extremely high steady-state and transient heat loads far exceed the material's own heat dissipation limits, necessitating a highly efficient cooling system for thermal management to prevent the mirror from melting, deforming, or cracking due to overheating. The effectiveness of the cooling system fundamentally depends on achieving a defect-free and robust connection between the first mirror body and the heat sink, which places extremely high demands on the bonding strength between the first mirror precursor and the substrate.

[0026] Molybdenum and its alloys are ideal materials for preparing the first mirror of nuclear fusion due to their high melting point, high thermal conductivity, low coefficient of thermal expansion, and low sputtering yield. However, molybdenum is difficult to machine, and existing technologies that directly grind it into shape and manufacture the first mirror component with built-in cooling channels suffer from high processing difficulty and manufacturing cost. To overcome this difficulty, this application proposes a technical solution to prepare a molybdenum coating on a pre-formed water-cooling device substrate such as low-activation steel or copper, in order to form a well-bonded first mirror precursor.

[0027] During the preparation of coatings using explosive spraying technology, the high temperature generated by the explosion easily causes molybdenum powder to react with active components such as oxygen and carbon in the environment or in the explosion products, generating impurities such as oxides and carbides. However, there are many parameters that affect the coating quality and performance in explosive spraying technology, and these parameters interact with each other, resulting in a complex mechanism that affects the coating quality and performance. Therefore, coating materials prepared in the existing technology often have the disadvantages of high impurity content and low purity.

[0028] When preparing molybdenum coatings using explosive spraying technology, the high temperatures generated by the deflagration of combustion gases can easily cause molybdenum powder to react with active components such as oxygen and carbon in the surrounding atmosphere or explosion products, generating impurities such as oxides and carbides. Furthermore, this process involves numerous parameters that affect coating performance and are interconnected, resulting in a complex mechanism of action. Consequently, coatings prepared by existing methods generally suffer from high impurity content and insufficient purity.

[0029] Therefore, it is necessary to provide a new preparation method that can effectively suppress the generation of impurities while ensuring a high bonding strength between the molybdenum coating and the substrate, thereby obtaining a coating structure with high purity and high thermal conductivity to meet the stringent application requirements of the first mirror of nuclear fusion.

[0030] Key process parameters for explosive spraying include the oxygen / fuel ratio (OFR), barrel filling ratio (BFR), nitrogen volume in the charge gases (NV), powder feeding rate (PFR), spraying distance (SD), and explosion temperature. This application, by defining suitable ranges for the above six parameters, enables the preparation of high-quality molybdenum coatings through their combined action.

[0031] To resolve the above issues, please refer to [link / reference]. Figure 1 , Figure 1 This invention provides a schematic flowchart of a method for preparing a first mirror precursor for a nuclear fusion device. This method can obtain a high-density and high-bonding-strength molybdenum coating on low-activation steel or copper water-cooled components. By controlling six key parameters affecting coating quality and performance in the explosive spraying technique, it reduces the possibility of powder oxidation and carbonization, thereby significantly reducing the content of impurities such as oxygen and carbon in the coating material. This results in a molybdenum coating with very low impurity content and high purity.

[0032] like Figure 1 As shown, the method for preparing the molybdenum coating includes steps S1 to S4.

[0033] S1. Roughen the surface of the substrate and clean the roughened substrate to obtain the base material.

[0034] Among them, such as Figure 2 As shown, the substrate 10 can be made of materials such as low-activation steel or copper water-cooled components.

[0035] In some embodiments, surface roughening methods include, but are not limited to, sandblasting, thread cutting, knurling, and electro-brushing.

[0036] For example, the surface of the substrate 10 can be sandblasted with 80-250 mesh white corundum abrasive to roughen it, and then ultrasonically cleaned with anhydrous ethanol and ultrapure water for 5-10 minutes. After that, it can be dried with dry compressed air and fixed on the explosion spraying equipment for subsequent spraying.

[0037] S2. Install the substrate on the explosive spraying equipment according to the installation parameters of the explosive spraying equipment.

[0038] Among them, such as Figure 2 As shown, the installation parameters may include the spraying distance, which is the distance between the spray gun nozzle 11 of the explosive spraying equipment and the surface of the substrate 10, and the range of the spraying distance is 30-50mm.

[0039] Specifically, variations in spraying distance within a certain range have little impact on the temperature at which the powder is heated. However, the powder velocity gradually increases with increasing spraying distance, until it approaches a certain upper speed limit. Experiments show that the optimal spraying effect is achieved when the spraying distance is controlled within the range of 30-50 mm. This allows for the formation of a high-density and high-bonding-strength molybdenum coating while maintaining a near-neutral ratio of oxygen and carbon active components in the explosion products. This significantly reduces the likelihood of powder oxidation and carbonization, thereby greatly minimizing the content of oxides and carbides in the molybdenum coating.

[0040] S3. Obtain the spraying parameters of the explosive spraying equipment, and feed the preset powder into the explosive spraying equipment according to the spraying parameters, and adjust the equipment parameters of the explosive spraying equipment. The spraying parameters include oxygen-fuel ratio, chamber filling rate, nitrogen dilution rate, and powder feeding rate. The oxygen-fuel ratio ranges from 1.40 to 1.70, the chamber filling rate ranges from 20% to 40%, the nitrogen dilution rate ranges from 6.00% to 10.00%, and the powder feeding rate ranges from 80 to 120 mg / s. The preset powder includes molybdenum powder or molybdenum alloy powder. The specific equipment parameters of the explosive spraying equipment may include the equipment parameters of the gas throttle valve 14 and the equipment parameters of the powder feeder 12.

[0041] The spraying parameters include the oxygen-fuel ratio, chamber filling rate, nitrogen dilution rate, and powder feeding rate. The oxygen-fuel ratio is the ratio of oxygen to fuel gas. The chamber filling rate is the ratio of the total volume of fuel gas, oxygen, and nitrogen (for dilution) injected into the explosion chamber before detonation to the chamber volume. The nitrogen dilution rate is the proportion of the nitrogen volume injected into the explosion chamber before detonation to the total injected gas volume. Since the explosive spraying is pulsed, the powder feeding rate refers to the amount of powder fed in a single pulse explosive spraying.

[0042] It should be noted that by combining these parameters, the preparation of explosive spray coatings under "low temperature mode" was achieved. That is, the temperature of the explosion products is low (not exceeding the melting point of the powder) while generating a high acceleration effect on the powder. This allows most of the powder to impact the substrate surface at extremely high speed in an unmelted state to form a coating. This can greatly reduce the content of impurities such as oxygen and carbon in the coating material, resulting in a metal coating with very low impurity content and high purity.

[0043] S4. Control the ignition of the explosive spraying equipment so that the explosive spraying equipment impacts the preset powder in a softened state onto the substrate surface to form a molybdenum coating.

[0044] Specifically, the spark plug of the explosive spraying equipment is controlled to ignite, thereby generating an explosion in the combustion chamber of the explosive spraying equipment, so as to impact the preset powder in a softened state onto the substrate surface to form a molybdenum coating.

[0045] To ensure the proper ignition of the gas inside the barrel of the explosive spraying equipment, the oxygen-fuel ratio needs to be within a certain range. Appropriately reducing the oxygen-fuel ratio within this range can reduce the oxygen impurity content in the resulting molybdenum coating to some extent; however, an excessively low oxygen-fuel ratio will lead to an increase in the carbon impurity content within the molybdenum coating. Experiments show that the optimal spraying effect is achieved when the oxygen-fuel ratio is between 1.40 and 1.70, ensuring proper gas ignition while maintaining very low oxygen and carbon content in the molybdenum coating.

[0046] Specifically, within the range of detonable chamber filling ratio, the higher the chamber filling ratio, the higher the energy generated by the explosion, and the higher the temperature and speed at which the powder is heated and accelerated. Experiments show that the optimal spraying effect is achieved when the chamber filling ratio is controlled within the range of 20%-40%.

[0047] Specifically, within the range of ignitable nitrogen dilution, appropriately increasing the nitrogen dilution value can lower the temperature of the explosion products, meaning the maximum temperature the powder can be heated will decrease, but the powder acceleration effect will not be significantly weakened. Experiments show that when the nitrogen dilution value is controlled within the range of 6.00%-10.00%, the NV value can appropriately coordinate with the BFR value to control the operating mode of the explosive spraying equipment, while reducing the impact on powder velocity.

[0048] Specifically, with other parameters fixed, the energy generated by each explosion is constant. Therefore, the powder feed rate must be within a certain range to ensure that the powder is heated and accelerated to the appropriate state, thus depositing a high-quality coating. Experiments show that controlling the powder feed rate within the range of 80-120 mg / s can appropriately reduce the maximum temperature and speed at which the powder is heated and accelerated, while appropriately increasing the thickness of the coating deposited per unit time.

[0049] Specifically, in some embodiments, the explosive spraying equipment includes a gas throttling valve 14 and a powder feeder 12. Based on the spraying parameters, the powder feeding parameters and operating mode of the explosive spraying equipment are determined. Based on the operating mode, the equipment parameters of the gas throttling valve 14 corresponding to each gas are adjusted. Based on the powder feeding parameters, the equipment parameters of the powder feeder 12 are adjusted. This allows for accurate determination of the equipment parameters of the gas throttling valve 14 and the powder feeder 12, thereby controlling each spraying parameter of the explosive spraying equipment within its optimal range. This significantly reduces the content of impurities such as oxygen and carbon in the coating material, resulting in a molybdenum coating with very low impurity content and high purity.

[0050] Each gas has a corresponding gas shut-off valve. For example, the oxygen input channel has a corresponding gas shut-off valve to control the oxygen input, the nitrogen input channel has a corresponding gas shut-off valve to control the nitrogen input, and the fuel gas input channel has a corresponding gas shut-off valve to control the fuel gas input. The powder feeder 12 is used to deliver powder into the explosive spraying equipment. The fuel gas can be acetylene or other gases.

[0051] Specifically, the equipment parameters of the powder feeder 12 can be adjusted by the powder feeding parameters, which may include the groove volume of the slider 13 and the model of the slider 13, etc.; the equipment parameters of the gas throttle valve 14 can be adjusted by the working mode, which may include the orifice diameter of the gas shut-off valve corresponding to each gas and the opening time, etc.

[0052] For example, based on the optimal spraying parameters provided in this application, the powder feeding parameters and working mode of the explosive spraying equipment are determined; based on the low temperature working mode, the equipment parameters of the gas throttle valve 14 corresponding to each gas (oxygen, nitrogen and acetylene) are adjusted; at the same time, the equipment parameters of the powder feeder 12 are also adjusted according to the powder feeding parameters, thereby controlling each spraying parameter of the explosive spraying equipment to be within the optimal range, which can greatly reduce the content of impurities such as oxygen and carbon in the coating material, so that the prepared molybdenum coating has a very low impurity content and high purity.

[0053] In some embodiments, according to the operating mode, the orifice diameter and opening duration of the gas throttle valve 14 corresponding to the fuel gas are adjusted; the orifice diameter and opening duration of the gas throttle valve 14 corresponding to the oxygen gas are adjusted; and the orifice diameter and opening duration of the gas throttle valve 14 corresponding to the nitrogen gas are adjusted. Thus, by controlling the orifice diameter and opening duration of the gas throttle valve 14 corresponding to each gas, the spraying parameters of the explosive spraying equipment can be controlled within the optimal range, thereby greatly reducing the content of impurities such as oxygen and carbon in the coating material, resulting in a molybdenum coating with very low impurity content and high purity.

[0054] Specifically, airflow shut-off valves with different orifice diameters can be used, and the duration of airflow injection can be controlled by controlling the opening duration of the airflow shut-off valve.

[0055] For example, when the orifice diameters of the gas throttle valves 14 for fuel gas and oxygen are the same, the injection time of fuel gas and oxygen can be controlled to achieve a predetermined OFR value; or, by controlling the injection time of fuel gas and oxygen to be the same, and using gas throttle valves 14 with specific orifice diameters for fuel gas and oxygen respectively, a predetermined OFR value can also be achieved.

[0056] For example, the larger the orifice of the gas throttle valve 14 for fuel gas and oxygen and the longer the gas injection time, the larger the BFR value; conversely, the smaller the BFR value.

[0057] For example, gas throttle valves 14 with different orifice sizes for nitrogen are used to control the duration of nitrogen injection. After the fuel gas and oxygen are injected, a small amount of nitrogen is usually injected. By controlling the orifice size of the gas throttle valve 14 corresponding to the nitrogen pipeline and the gas injection time, the predetermined NV value can be achieved.

[0058] In some embodiments, the volume of the groove in the slider 13 corresponding to the powder feeder 12 is adjusted according to the powder feeding parameters. This allows the powder feeding efficiency of the detonation spraying equipment to be controlled within an optimal range by controlling the volume and type of the groove in the slider 13 corresponding to the powder feeder 12. This can appropriately reduce the maximum temperature and speed at which the powder is heated and accelerated, while appropriately increasing the thickness of the coating deposited per unit time.

[0059] Specifically, by using powder feeders 12 and sliders 13 with different groove volumes, the amount of powder injected for each explosion pulse can be controlled.

[0060] For example, the amount of powder injected for each explosion pulse can be controlled by adjusting the groove volume of slider 13 using different models of slider 13. A smaller groove volume results in a lower NV value, and vice versa.

[0061] The preset powder includes molybdenum powder or molybdenum alloy powder, and the molybdenum alloy powder includes TZM alloy powder. The preset powder is sprayed onto the substrate surface to form a corresponding molybdenum or molybdenum alloy coating.

[0062] In some embodiments, the particle size of the preset powder is 5-20 μm, for example, the particle size of the preset powder is 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, so that the preset powder is in a softened state rather than a molten state after being ignited by the explosive spraying equipment.

[0063] Optionally, the particle size of the preset powder added to the explosive spraying equipment can be inconsistent. For example, the particle size distribution parameters of the preset powder are D10: 8±1μm, D50: 12±1μm, and D90: 16±1μm. That is, 10% of the sample particles in the preset powder are smaller than 8±1μm, 50% of the sample particles are smaller than 12±1μm, and 90% of the sample particles are smaller than 16±1μm.

[0064] It should be noted that the corresponding installation and spraying parameters can be determined based on the melting point, density, particle size, and other characteristics of different types of powders.

[0065] For example, if a pure molybdenum coating is prepared using the molybdenum coating and its preparation method provided in this application, the range of the spraying distance can be reduced to 30-40 mm; the range of the oxygen-fuel ratio can be reduced to 1.40-1.60; the range of the chamber filling rate can be reduced to 30%-40%; the range of the nitrogen dilution amount can be reduced to 6.50%-8.50%; and the range of the powder feeding rate can be reduced to 85-115 mg / s.

[0066] Specifically, after adjusting the equipment parameters of the explosive spraying equipment, the preset powder is fed into the adjusted explosive spraying equipment, and the preset powder is sprayed onto the substrate 10 using the explosive spraying equipment to form a molybdenum coating.

[0067] In one embodiment, since the agglomerated mixed powder easily absorbs moisture from the air, before feeding the preset powder into the explosive spraying equipment, the method further includes: placing the preset powder in a baking oven and baking it at a constant temperature of 100°C for 4 hours.

[0068] In some embodiments, the preset powder is fed into the explosive spraying equipment using a preset powder feeding method, wherein the powder feeding method includes in-gun powder feeding or off-axis powder feeding. Considering cost and adaptability, the preset powder feeding method generally adopts in-gun powder feeding.

[0069] In some embodiments, the spraying frequency of the explosive spraying equipment is in the range of 7-10 Hz to control the thickness of the molybdenum coating.

[0070] In some embodiments, the spray gun movement speed of the explosive spraying equipment is in the range of 8-10 mm / s to further control the thickness of the molybdenum coating.

[0071] In some embodiments, the explosion temperature generated when the explosive spraying equipment is ignited ranges from 2500℃ to 3200℃, so that the preset powder remains in a softened state rather than a molten state after ignition. The explosion temperature refers to the highest instantaneous flame temperature generated when the fuel gas and oxygen mix in the combustion chamber of the spray gun and then ignite and explode.

[0072] In some embodiments, the preset powder is sprayed onto the substrate 10 using the explosive spraying equipment to form a molybdenum coating.

[0073] Specifically, oxygen and fuel gas in a preset ratio are delivered from the gas supply port corresponding to the explosive spraying equipment to the combustion chamber of the water-cooled spray gun; the preset powder is fed into the combustion chamber through the powder feeder 12 so that the preset powder floats in the mixture of oxygen and fuel gas, and is ignited by a spark plug and burns and explodes in the mixture to generate heat to reach a melting state, and the preset powder is sprayed at high speed onto the surface of the substrate 10 to form a molybdenum coating by means of the high pressure generated by the explosion shock wave.

[0074] For example, oxygen and acetylene in a preset ratio are delivered from the gas supply port of the explosive spraying device to the combustion chamber of the water-cooled spray gun; preset molybdenum powder or molybdenum alloy powder is fed into the combustion chamber through the powder feeder 12 so that the molybdenum powder and molybdenum alloy powder float in the mixture of oxygen and acetylene, and is ignited by a spark plug and burns and explodes in the mixture to generate heat to reach a softened state, and the softened molybdenum powder or molybdenum alloy powder is sprayed at high speed onto the surface of the substrate 10 to form a molybdenum coating by means of the high pressure generated by the explosion shock wave.

[0075] In one embodiment, such as Figure 2 As shown, based on Figure 2 The explosive spraying equipment provided is used to perform an explosive spraying process cyclically. The explosive spraying process consists of the following four steps: (1) Air intake: Mix explosive gas at the air intake and input the mixture into the spray gun. The explosive gas used is mainly oxygen and acetylene (the ratio needs to be specified).

[0076] (2) Powder feeding: Nitrogen gas is used to feed the preset powder into the spray gun to form a powder mist in a certain area of ​​the spray gun barrel; there are two powder feeding methods: axial powder feeding and radial powder feeding, with axial powder feeding being the main one.

[0077] (3) Ignition: A given frequency ignition signal is emitted into the explosion chamber of the gun barrel. The explosion ignites the combustible gas. The explosion lasts for a few milliseconds and generates a high temperature of about 3200°C and an airflow of about 1500 m / s. The high-temperature and high-speed airflow acts on the preset powder particles. The particles are softened by heating and are shot toward the surface of the substrate 10 at an initial velocity of 600-1000 m / s. When the powder hits the surface of the substrate 10, the kinetic energy is converted into heat energy. The temperature of the powder particles rises during the impact, even reaching their melting point. Therefore, a surface coating with extremely high density and high bonding strength can be formed.

[0078] (4) Remove residual gas and powder: Introduce protective gas into the chamber. The protective gas is nitrogen. Remove the remaining gas and powder in the barrel to prepare for the next cycle. Repeat the above steps in the next cycle.

[0079] It should be noted that the explosive spraying equipment can be adjusted according to the spraying parameters and installation parameters, and the molybdenum coating prepared by the adjusted explosive spraying equipment can achieve better results. Of course, other parameters can also be used in other embodiments.

[0080] The molybdenum coating preparation method provided in this application utilizes a reasonable combination of various spraying parameters in explosive spraying. The heat generated by the combustion explosion softens the molybdenum powder or molybdenum alloy powder, and the high pressure generated by the explosion shock wave impinges the softened powder on the substrate surface at two to three times the speed of sound to form a molybdenum coating. Simultaneously, the proportion of oxygen and carbon active components in the explosion products under these parameters significantly reduces the possibility of powder oxidation and carbonization, thereby greatly reducing the content of oxide and carbide impurities in the coating.

[0081] Compared with related technologies, the beneficial effects of the present invention are: (1) A molybdenum coating suitable for the first mirror precursor of a nuclear fusion device and its preparation method are provided. The method forms the first mirror precursor by explosively spraying a molybdenum coating on a low-activation steel or copper water-cooled component, avoiding the bottleneck that the whole molybdenum material is difficult to directly process into a complex cooling structure, significantly reducing the manufacturing cost, and has high process efficiency and the potential for mass production.

[0082] (2) The selected molybdenum coating has excellent thermophysical properties, with a thermal conductivity of up to 142 W / (m·K). Its thermal expansion properties are well matched with commonly used substrate materials, which can effectively conduct high heat loads and withstand transient thermal shock and neutron irradiation environment, thereby ensuring the stability of the first mirror under extreme working conditions and extending its service life.

[0083] (3) By precisely controlling the process parameters of the explosive spraying, the oxidation and carbonization reactions of molybdenum during the spraying process were effectively suppressed, resulting in a coating with low impurity content and dense structure. The coating exhibits high thermal conductivity and low oxide content, which can meet the stringent requirements of efficient heat dissipation and material purity for the first mirror of nuclear fusion.

[0084] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a molybdenum coating, characterized in that, The preparation method includes: The substrate is roughened on the surface and then cleaned to obtain the base material. Obtain the installation parameters of the explosive spraying equipment, and install the substrate on the explosive spraying equipment according to the installation parameters. The installation parameters include the spraying distance, which is in the range of 30-50mm. The process involves acquiring the spraying parameters of the explosive spraying equipment, feeding a preset powder into the explosive spraying equipment according to the spraying parameters, and adjusting the equipment parameters of the explosive spraying equipment. The spraying parameters include the oxygen-fuel ratio, chamber filling rate, nitrogen dilution rate, and powder feeding rate. The oxygen-fuel ratio ranges from 1.40 to 1.70, the chamber filling rate ranges from 20% to 40%, the nitrogen dilution rate ranges from 6.00% to 10.00%, and the powder feeding rate ranges from 80 to 120 mg / s. The preset powder includes molybdenum powder or molybdenum alloy powder. The explosive spraying equipment is controlled to ignite so that it impacts the preset powder in a softened state onto the substrate surface to form a molybdenum coating.

2. The preparation method according to claim 1, characterized in that, The particle size range of the preset powder is 5-20 μm.

3. The preparation method according to claim 1, characterized in that, The spraying frequency range of the explosive spraying equipment is 7-10Hz.

4. The preparation method according to claim 1, characterized in that, The spray gun moving speed of the explosive spraying equipment is in the range of 8-10 mm / s.

5. The preparation method according to claim 1, characterized in that, The explosion temperature range when the explosive spraying equipment is ignited is 2500℃-3200℃.

6. The preparation method according to claim 1, characterized in that, The substrate is installed on the explosive spraying equipment according to the installation parameters, which include the spraying distance, including: Based on the spraying distance, adjust the distance between the spray gun nozzle of the explosive spraying equipment and the substrate surface to determine the installation position of the substrate; The substrate is mounted on the explosive spraying equipment at the specified mounting location.

7. The preparation method according to claim 1, characterized in that, The spraying equipment includes a gas shut-off valve and a powder feeder. The steps of feeding preset powder into the explosive spraying equipment according to the spraying parameters and the equipment parameters of the explosive spraying equipment include: Based on the spraying parameters, determine the powder feeding parameters and operating mode of the spraying equipment; According to the operating mode, the equipment parameters of the gas throttle valves corresponding to each gas are adjusted; The equipment parameters of the powder feeder are adjusted according to the powder feeding parameters.

8. The preparation method according to claim 7, characterized in that, The step of adjusting the equipment parameters of the gas throttle valves corresponding to each gas according to the operating mode includes: According to the operating mode, the orifice diameter and opening duration of the gas throttle valve corresponding to the fuel gas are adjusted. The orifice diameter and opening duration of the gas throttle valve corresponding to oxygen are adjusted; and, The orifice diameter and opening duration of the gas throttle valve corresponding to nitrogen are adjusted.

9. The preparation method according to claim 1, characterized in that, The substrate includes low-activation steel or copper water-cooled components.

10. A molybdenum coating, characterized in that, The molybdenum coating is prepared by any one of the preparation methods described in claims 1 to 9.

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