A high-flux heat exchange tube high-power plasma sprayed porous coating and a preparation method thereof and a high-flux heat exchange tube

Abstract

The application provides a high-flux heat exchange pipe high-power plasma sprayed porous coating and a preparation method thereof and a high-flux heat exchange pipe, and relates to the field of porous coatings. The high-flux heat exchange pipe high-power plasma sprayed porous coating comprises, according to the total mass of 100%, 3-5% of a beta-NiAl phase, 5-7% of a gamma'-Ni3Al phase, 0.5-2% of a hard phase, and the balance of a stainless steel matrix phase. The hard phase comprises CrB, Ni3B and FeSi; and the stainless steel matrix phase comprises gamma-Fe. The beta-NiAl phase or the gamma'-Ni3Al phase provides high-temperature strength and oxidation and corrosion resistance; and the hard phase such as CrB, Ni3B and FeSi is embedded in the metal matrix to provide extremely high wear resistance and corrosion resistance.

Description

Technical Field

[0001] This application relates to the field of porous coatings, and more particularly to a high-power plasma-sprayed porous coating for high-throughput heat exchange tubes, its preparation method, and the high-throughput heat exchange tube itself. Background Technology

[0002] The heat transfer capacity of traditional smooth heat exchanger tubes has become a performance bottleneck. To achieve a significant increase in heat transfer intensity within a confined space, porous coatings need to be prepared on the inner and outer surfaces of the heat exchanger tubes. This greatly enhances boiling phase change heat transfer by significantly increasing the specific surface area and providing stable vaporization nuclei. High-flux heat exchanger tubes utilize a special process to form a porous metal layer on the smooth inner and outer surfaces. This surface provides an extremely large number of micropores, increasing the number of vaporization nuclei. The porous layer itself has a huge specific surface area, expanding the heat transfer area. The capillary force of the porous layer continuously draws liquid to the heating surface, while the generated steam can be smoothly discharged through the interconnected pores, improving liquid supply and steam escape. It is mainly used in evaporators, with base tube materials including copper, carbon steel, and heat-resistant steel, and is suitable for handling media such as alkanes, olefins, and aromatics.

[0003] The limited space constraints of narrow inner diameter and high curvature in high-flux heat exchanger tubes pose significant challenges to coating preparation technology. Coatings must not only possess high porosity, good bonding strength, and structural uniformity, but also achieve efficient and reliable deposition on the inner wall of the tube. The main methods for preparing porous layers in high-flux heat exchanger tubes include coating, sintering, and machining. Coating methods form porous layers through electrochemical corrosion, flame spraying, and plasma spraying; sintering methods sinter metal powder onto the surface of the base tube to form a robust porous layer; and machining methods form microstructures on the tube surface through rolling and cutting. Among these, coating offers the strongest bonding and most stable performance. Currently, the quality control requirements for coated porous layers in high-flux heat exchanger tubes are high, especially in achieving a stable balance of various properties such as operability, porosity, and bonding strength in inner-hole spraying—a common challenge facing the industry. Summary of the Invention

[0004] The purpose of this application is to provide a high-power plasma-sprayed porous coating for high-throughput heat exchange tubes, a method for preparing the same, and a high-throughput heat exchange tube, in order to solve the above-mentioned problems.

[0005] To achieve the above objectives, the first aspect of this application provides a high-throughput heat exchanger tube with a high-power plasma-sprayed porous coating, comprising, by weight (100%): 3-5% β-NiAl phase, 5-7% γ'-Ni3Al phase, 0.5-2% hard phase, balance stainless steel matrix phase; The hard phase includes CrB, Ni3B and FeSi; The stainless steel matrix phase includes γ-Fe.

[0006] Optionally, the thickness of the high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube is 0.1-0.5 mm; And / or, the porosity of the high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube is 20%-70%.

[0007] A second aspect of this application provides a method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube, comprising: The raw materials are mixed and vacuum atomized to obtain alloy powder; The alloy powder and the pore-forming agent are mixed to obtain a mixture; The mixture is applied to the inner wall of a high-throughput heat exchange tube using high-power plasma spraying, and then degreased under a hydrogen atmosphere to obtain a high-power plasma sprayed porous coating inside the high-throughput heat exchange tube. The raw materials include Fe, Cr, Ni, Al, Si, and B.

[0008] Optionally, the raw materials, based on a total mass of 100%, include: 14-18% Cr, 18-20% Ni, 2-4% Al, 1-2% Si, 0.5-1% B, balance Fe.

[0009] Optionally, the vacuum degree of the vacuum atomization is less than 5 × 10⁻⁶. -3 The melting temperature is 1550-1600℃, and the atomization pressure is 2.8-3.0MPa; And / or, the vacuum atomizing nozzle material protects graphite and corundum, and the atomizing medium includes nitrogen.

[0010] Optionally, the particle size of the alloy powder is 25-109 μm.

[0011] Optionally, the pore-forming agent comprises nickel-coated graphite powder; And / or, the particle size of the pore-forming agent is 15-45 μm; And / or, the mass ratio of the alloy powder to the pore-forming agent is 3-9:1.

[0012] Optionally, the high-power plasma spraying has a power of 100-150kW, a powder feeding rate of 50-100g / min, and a spraying distance of 90-120mm; And / or, the degreasing treatment is performed at a temperature of 400-440°C for a time of 30-60 minutes.

[0013] A third aspect of this application provides a high-throughput heat exchange tube, including a high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube.

[0014] Optionally, the diameter of the high-throughput heat exchange tube is ≥10cm.

[0015] Compared with the prior art, the beneficial effects of this application include: The high-throughput heat exchanger tube high-power plasma-sprayed porous coating provided in this application features a β-NiAl phase or γ'-Ni3Al phase that provides high-temperature strength and resistance to oxidation and corrosion. Hard phases such as CrB, Ni3B, and FeSi are embedded in the metal matrix, providing extremely high wear resistance and corrosion resistance. The numerous micropores in the high-power plasma-sprayed porous coating provide readily available "vaporization nuclei," and the interconnected physical structure of the micron-sized pores significantly reduces the boiling point and achieves extremely high heat transfer coefficients at low heat flux densities. The Ni and Al components added to the coating have good thermal conductivity, making it suitable for high heat flux density scenarios.

[0016] The method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube provided in this application utilizes the extremely high plasma jet energy and velocity of high-power plasma spraying to instantly and fully melt alloy powder and spray it at high speed onto the inner wall of the tube, rapidly constructing a functional coating with strong adhesion, controllable thickness, and optimized pore structure. This provides a feasible advanced manufacturing path for breaking through the heat transfer limit of high-throughput heat exchanger tubes.

[0017] The high-throughput heat exchange tube provided in this application has good heat exchange performance. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0019] Figure 1 This is a cross-sectional morphology diagram of a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube provided in Example 1. Detailed Implementation

[0020] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a high-throughput heat exchanger tube with a high-power plasma-sprayed porous coating, comprising, by 100% of total mass: 3-5% β-NiAl phase, 5-7% γ'-Ni3Al phase, 0.5-2% hard phase, balance stainless steel matrix phase; Optionally, a high-power plasma-sprayed porous coating is applied inside the high-throughput heat exchange tube. By weight, the β-NiAl phase can be any value between 3%, 4%, 5%, or 3-5%, the γ'-Ni3Al phase can be any value between 5%, 6%, 7%, or 5-7%, the hard phase can be any value between 0.5%, 1%, 1.5%, 2%, or 0.5-2%, and the balance is a stainless steel matrix phase. The hard phase includes CrB, Ni3B and FeSi; In some embodiments, the mass ratio of CrB, Ni3B and FeSi is 20-50:5-30:30-70; The stainless steel matrix phase includes γ-Fe.

[0021] In some embodiments, the thickness of the high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube is 0.1-0.5 mm; Optionally, the thickness of the high-power plasma-sprayed porous coating inside the high-flux heat exchanger tube can be any value between 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, or 0.1-0.5 mm. And / or, the porosity of the high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube is 20%-70%.

[0022] Optionally, the porosity of the high-power plasma-sprayed porous coating inside the high-flux heat exchanger tube can be any value between 20%, 30%, 40%, 50%, 60%, 70%, or 20-70%.

[0023] A second aspect of this application provides a method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube, comprising: The raw materials are mixed and vacuum atomized to obtain alloy powder; The alloy powder and the pore-forming agent are mixed to obtain a mixture; The mixture is applied to the inner wall of a high-throughput heat exchange tube using high-power plasma spraying, and then degreased under a hydrogen atmosphere to obtain a high-power plasma sprayed porous coating inside the high-throughput heat exchange tube. It should be noted that the preparation of alloy powder by vacuum atomization, based on stainless steel powder composition, is low in cost and has a wide range of applications; high-power plasma spraying has high working efficiency, simple process, strong coating adhesion and controllable thickness, and can be rapidly industrialized; the introduction of nickel-coated graphite powder pore-forming agent can cleverly create vacancies to obtain a large number of interconnected pores, and can be easily removed at low temperature without damaging the porous metal layer material and the corrosion resistance of the base tube. The raw materials include Fe, Cr, Ni, Al, Si, and B.

[0024] It is important to note that by optimizing the ratio of Ni, Al, and Cr, in addition to the γ-Ni-based solid solution, high-strength β-NiAl or γ'-Ni3Al phases precipitate in the interfacial region between these particles. These intermetallic compounds provide high-temperature strength and resistance to oxidation and corrosion. At the same time, the extremely thin Al2O3 or Cr2O3 film formed during the spraying process encapsulates the particles. These oxides are tightly bonded together in the neck region, exhibiting extremely high thermal stability and effectively blocking the diffusion of oxygen and metal ions, greatly enhancing the bonding force and resistance to high-temperature oxidation. During the degreasing process, Al2O3 or Cr2O3 is reduced. Adding appropriate amounts of melting point reducing elements such as Si and B will also form hard phases such as CrB and Ni3B embedded in the metal matrix in the particle neck region, providing extremely high wear resistance and corrosion resistance.

[0025] Furthermore, by using vacuum atomization powder production technology instead of ordinary gas atomization powder production, the sphericity of the powder can be improved, thereby enhancing the powder's flowability and significantly increasing spraying efficiency and uniformity.

[0026] Furthermore, the effective addition of nickel-coated graphite powder as a pore-forming agent during the spraying process enables the coating to form a specific pore structure during subsequent heat treatment, achieving excellent boiling heat transfer performance. By employing high-power plasma spraying technology, the power and stability of the plasma arc are significantly improved, resulting in higher energy input, higher enthalpy, and faster plasma jets. The larger contact area between the fully molten particles and the substrate, along with the localized high temperature and pressure generated by high-speed impacts, facilitates microscopic diffusion and metallurgical bonding, thereby significantly enhancing the bonding strength between the coating and the substrate.

[0027] In some embodiments, the raw materials, based on a total mass of 100%, include: 14-18% Cr, 18-20% Ni, 2-4% Al, 1-2% Si, 0.5-1% B, balance Fe.

[0028] Optionally, the raw materials, based on a total mass of 100%, may contain Cr, any value between 14%, 15%, 16%, 17%, 18%, or 14-18%; Ni, any value between 18%, 19%, 20%, or 18-20%; Al, any value between 2%, 3%, 4%, or 2-4%; Si, any value between 1%, 1.5%, 2%, or 1-2%; B, any value between 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or 0.5-1%; and the balance being Fe.

[0029] It is important to note that the 14-18% Cr content, 18-20% Ni content, and 2-4% Al content are intended to precipitate a high-strength β-NiAl phase or γ'-Ni3Al phase, resulting in excellent high-temperature oxidation resistance. The addition of 1-2% Si and 0.5-1% B is to form a hard phase, achieving good wear and corrosion resistance. Furthermore, the use of high-power spraying technology and the formation of the oxide film during spraying, which exhibits extremely high thermal stability, both contribute to enhanced coating adhesion. The Cr content is 14-18%; too low a content will prevent the formation of a dense and stable passivation layer. The film provides good corrosion resistance, but excessive content will lead to reduced toughness; the Ni content is 18-20%, too low a content cannot strengthen and stabilize austenite, obtain a fully austenitic structure, and thus obtain good toughness and ductility, while too high a content is uneconomical; the Al content is 2-4%, too low a content cannot precipitate a high-strength NiAl phase, while too high a content will cause hot brittleness during spraying and easily lead to cracks; the Si content is 1-2% and the B content is 0.5-1%, too low a content cannot form a hard phase, while too high a content will cause micro-segregation, which can easily lead to local enrichment and the formation of brittle phases.

[0030] In some embodiments, the vacuum degree of the vacuum atomization is less than 5 × 10⁻⁶. -3 The melting temperature is 1550-1600℃, and the atomization pressure is 2.8-3.0MPa; Optionally, the vacuum degree of vacuum atomization can be 1×10⁻⁶. -3 2×10 -3 3×10 -3 4×10 -3 4.9×10 -3 Or less than 5×10 -3 The melting temperature can be any value, such as 1550℃, 1560℃, 1570℃, 1580℃, 1590℃, 1600℃ or any value between 1550℃ and 1600℃; the atomization pressure can be any value between 2.8 MPa, 2.9 MPa, 3 MPa or 2.8-3 MPa. It is important to note that the melting temperature is designed to be 1550-1600℃, which is higher than the melting point of the main component Fe. This helps to reduce the viscosity of the melt, facilitates the spherical shape of the droplets, and reduces irregular particles. The higher the gas pressure and the faster the gas flow, the stronger the shear force and kinetic energy transfer on the molten metal, resulting in more complete droplet breakage and finer powder particle size. The atomization pressure is designed to be 2.8-3.0MPa, which allows the atomized powder particle size distribution to fall to a maximum of 25-109μm. It should also be noted that the properly proportioned raw materials, such as pure iron, chromium blocks, nickel plates, aluminum blocks, ferroborone, and silicon blocks, dissolve in each other under vacuum and high temperature to form a uniform austenitic solid solution. Dissolved gases such as hydrogen and nitrogen escape due to their extremely low partial pressure, achieving degassing, while harmful trace elements such as Pb and Sn are volatilized and removed. Under the impact of high-speed, high-pressure inert gas, the molten metal stream is torn into droplets. Large droplets are further broken into smaller droplets by the airflow during flight; during descent, they rapidly cool and solidify, eventually forming spherical powder. And / or, the vacuum atomizing nozzle material protects graphite and corundum, and the atomizing medium includes nitrogen.

[0031] In some embodiments, the particle size of the alloy powder is 25-109 μm.

[0032] Optionally, the particle size of the alloy powder can be any value between 25μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 109μm or 25-109μm.

[0033] It is important to note that powder particles smaller than 25μm are prone to sticking and clogging the spray gun nozzle during the spraying process; powder particles larger than 109μm result in incomplete powder melting. Setting the powder particle size of the sprayed alloy powder between 25-109μm maximizes the utilization of powder products produced by vacuum atomization, reduces waste powder, and significantly lowers costs.

[0034] In some embodiments, the pore-forming agent comprises nickel-coated graphite powder; And / or, the particle size of the pore-forming agent is 15-45 μm; Optionally, the particle size of the pore-forming agent can be any value between 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 15-45μm; It should be noted that the particle size of the pore-forming agent is set between 15-45μm to facilitate the formation of micropores and to generate irregularly shaped, interconnected channels. This structure is conducive to the formation of through pores, improves the permeability of the porous layer, and ensures heat transfer efficiency. And / or, the mass ratio of the alloy powder to the pore-forming agent is 3-9:1.

[0035] Optionally, the mass ratio of alloy powder to pore-forming agent can be any value between 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 3:9:1.

[0036] It is important to note that, as a pore-forming agent, the ratio of nickel-coated graphite powder to the sprayed powder varies from 9:1 to 3:1, depending on the porosity of the coating. The purpose of nickel-coated graphite powder is to increase its bonding with the substrate. In addition, the nickel contained in the nickel-coated graphite powder can serve as a nickel source for the final high-power plasma-sprayed porous coating inside the high-flux heat exchanger tube.

[0037] In some embodiments, the high-power plasma spraying has a power of 100-150kW, a powder feeding rate of 50-100g / min, and a spraying distance of 90-120mm; Optionally, the power of high-power plasma spraying can be any value between 100 kW, 110 kW, 120 kW, 130 kW, 140 kW, 150 kW or 100-150 kW, the powder feed rate can be any value between 50 g / min, 60 g / min, 70 g / min, 80 g / min, 90 g / min, 100 g / min or 50-100 g / min, and the spraying distance can be any value between 90 mm, 100 mm, 110 mm, 120 mm or 90-120 mm. It is important to note that internal spraying is a challenging operation. Using high-power spraying (100-150kW) can effectively improve coating adhesion and spraying efficiency. The powder feed rate (50-100g / min) must be matched with the heat source power. If the powder feed rate is too high, each particle will not receive enough heat; if it is too low, the particles may overheat. The spraying distance should be 90-120mm. Too short a distance may lead to overheating and oxidation, while too long a distance will weaken the particle speed and temperature due to air resistance and radiation, resulting in poor adhesion. Under high-power spraying processes, in order to prevent the overall temperature of the substrate and coating from becoming too high and causing excessive thermal stress, high-flow-rate cooling gas is required to enhance cooling.

[0038] And / or, the degreasing treatment is performed at a temperature of 400-440°C for a time of 30-60 minutes.

[0039] Optionally, the temperature for degreasing can be any value between 400℃, 410℃, 420℃, 430℃, 440℃ or 400-440℃, and the time can be any value between 30 min, 40 min, 50 min, 60 min or 30-60 min.

[0040] It should be noted that the degreasing process is the process of removing the graphite component from the nickel-coated graphite powder that forms the pores. The graphite removal and pore formation can be achieved under the appropriate temperature and time conditions of the degreasing process.

[0041] A third aspect of this application provides a high-throughput heat exchange tube, including a high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube.

[0042] In some embodiments, the diameter of the high-throughput heat exchange tube is ≥10cm.

[0043] Optionally, the diameter of the high-flux heat exchange tube can be any value of 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, 16 cm, 17 cm, 18 cm, 19 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, 50 cm, 100 cm or ≥10 cm.

[0044] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0045] Example 1 The first aspect of this embodiment provides a high-throughput heat exchanger tube with a high-power plasma-sprayed porous coating, comprising, by weight 100%,: 3.95% β-NiAl phase, 6.11% γ'-Ni3Al phase, 1.89% hard phase, balance stainless steel matrix phase; The hard phase comprises CrB, Ni3B, and FeSi in a mass ratio of 0.44:0.29:1.16; The matrix phase of stainless steel includes γ-Fe.

[0046] The second aspect of this embodiment provides a method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube. The specific preparation steps are as follows: S1: An alloy powder coating material was prepared using a 100kg vacuum atomization powder preparation system. The raw materials (based on 100% total mass, including: 15.63% Cr, 18.12% Ni, 2.75% Al, 1.36% Si, 0.71% B, with the balance being Fe) were mixed. The resulting mixture was then vacuum atomized at a vacuum degree of 4.9 × 10⁻⁶. -3 The melting temperature was 1570℃, the atomization pressure was 2.9MPa, and then alloy powder of suitable particle size was obtained by sieving with 140-mesh and 500-mesh sieves. The particle size of the alloy powder was ≤25μm: 0.1% and ≥109μm: 0.6%. S2: Mix the alloy powder and the pore-forming agent nickel-coated graphite powder with a particle size of 15-45μm, with a mass ratio of alloy powder to pore-forming agent of 9:1, to obtain the mixture; S3: The mixture is applied to the inner wall of the high-throughput heat exchange tube using high-power plasma spraying. The high-power plasma spraying power is 120kW, the powder feeding rate is 80g / min, and the spraying distance is 110mm. Degreasing treatment is carried out in a hydrogen atmosphere at a temperature of 400℃ for 30min to obtain a high-power plasma sprayed porous coating inside the high-throughput heat exchange tube.

[0047] The cross-sectional morphology of the high-power plasma-sprayed porous coating inside the high-throughput heat exchanger tube provided in this embodiment is as follows: Figure 1 As shown.

[0048] The third aspect of this application provides a high-throughput heat exchange tube, which is prepared by the above-described S3 step.

[0049] Example 2 The difference from Example 1 is that the degreasing temperature is 440°C.

[0050] Example 3 The difference from Example 1 is that the degreasing time is 60 minutes.

[0051] Example 4 The difference from Example 1 is that the degreasing temperature is 440°C and the degreasing time is 60 minutes.

[0052] Example 5 The difference from Example 1 is that in step S2, the mass ratio of alloy powder to pore-forming agent is 9:3, the degreasing temperature is 440°C, and the degreasing time is 60 minutes.

[0053] Comparative Example 1 The difference from Example 1 is that the high-throughput heat exchange tube provided in Example 1 is replaced with a commercially available sintered high-throughput heat exchange tube (using a stainless steel-based porous coating), purchased from Cal Gavin's HITRAN® series products.

[0054] Comparative Example 2 The difference from Example 1 is that Cr is not added to the raw materials in step S1, that is, the hard phase of the high-power plasma-sprayed porous coating in the high-throughput heat exchange tube does not contain CrB.

[0055] Comparative Example 3 The difference from Example 1 is that Ni is not added to the raw materials in step S1, that is, the hard phase of the high-power plasma-sprayed porous coating in the high-throughput heat exchange tube does not contain β-NiAl phase, γ'-Ni3Al phase and Ni3B.

[0056] Comparative Example 4 The difference from Example 1 is that Al is not added to the raw materials in step S1, that is, the hard phase of the high-power plasma-sprayed porous coating in the high-throughput heat exchange tube does not contain β-NiAl phase or γ'-Ni3Al phase.

[0057] Comparative Example 5 The difference from Example 1 is that Si is not added to the raw materials in step S1, that is, the hard phase of the high-power plasma-sprayed porous coating in the high-throughput heat exchange tube does not contain the FeSi phase.

[0058] Comparative Example 6 The difference from Example 1 is that vacuum atomization is not performed; instead, the raw materials are directly mixed to obtain alloy powder.

[0059] Comparative Example 7 The difference from Example 1 is that the pore-forming agent nickel-coated graphite powder is replaced with an equal mass of graphite powder.

[0060] Comparative Example 8 The difference from Example 1 is that degreasing is not performed in step S3.

[0061] The above embodiments and comparative examples were subjected to performance tests, and the specific test results are shown in Table 1.

[0062] Table 1 Performance Tests

[0063] analyze: The above tests show that the high-power plasma-sprayed porous coating product for high-throughput heat exchange tubes outperforms the sintered high-throughput heat exchange tube stainless steel-based porous coating products on the market. Without adding Cr and Ni to the raw materials and without vacuum atomization, the coating cannot be successfully sprayed. Without adding Al and Si, the wear resistance and oxidation resistance are greatly affected. Without using nickel-coated graphite as a pore-forming agent, the coating porosity, bonding strength and corrosion resistance will be damaged. Without degreasing treatment, the coating porosity is greatly reduced.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0065] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A high-power plasma-sprayed porous coating for high-throughput heat exchange tubes, characterized in that, Based on a total mass of 100%, including: 3-5% β-NiAl phase, 5-7% γ'-Ni3Al phase, 0.5-2% hard phase, balance stainless steel matrix phase; The hard phase includes CrB, Ni3B and FeSi; The stainless steel matrix phase includes γ-Fe.

2. The high-throughput heat exchanger tube high-power plasma-sprayed porous coating according to claim 1, characterized in that, The thickness of the high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube is 0.1-0.5 mm; And / or, the porosity of the high-power plasma-sprayed porous coating inside the high-throughput heat exchange tube is 20%-70%.

3. A method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube as described in claim 1 or 2, characterized in that, include: The raw materials are mixed and vacuum atomized to obtain alloy powder; The alloy powder and the pore-forming agent are mixed to obtain a mixture; The mixture is applied to the inner wall of a high-throughput heat exchange tube using high-power plasma spraying, and then degreased under a hydrogen atmosphere to obtain a high-power plasma sprayed porous coating inside the high-throughput heat exchange tube. The raw materials include Fe, Cr, Ni, Al, Si, and B.

4. The method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube according to claim 3, characterized in that, The raw materials, based on a total mass of 100%, include: 14-18% Cr, 18-20% Ni, 2-4% Al, 1-2% Si, 0.5-1% B, balance Fe.

5. The method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube according to claim 3, characterized in that, The vacuum degree of the vacuum atomization is less than 5 × 10⁻⁶. -3 The melting temperature is 1550-1600℃, and the atomization pressure is 2.8-3.0MPa; And / or, the vacuum atomizing nozzle material protects graphite and corundum, and the atomizing medium includes nitrogen.

6. The method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube according to claim 3, characterized in that, The particle size of the alloy powder is 25-109μm.

7. The method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube according to claim 3, characterized in that, The pore-forming agent includes nickel-coated graphite powder; And / or, the particle size of the pore-forming agent is 15-45 μm; And / or, the mass ratio of the alloy powder to the pore-forming agent is 3-9:

1.

8. The method for preparing a high-power plasma-sprayed porous coating inside a high-throughput heat exchanger tube according to any one of claims 3-7, characterized in that, The high-power plasma spraying has a power of 100-150kW, a powder feeding rate of 50-100g / min, and a spraying distance of 90-120mm. And / or, the degreasing treatment is performed at a temperature of 400-440°C for a time of 30-60 minutes.

9. A high-flux heat exchange tube, characterized in that, Including the high-power plasma-sprayed porous coating inside the high-throughput heat exchanger tube as described in claim 1 or 2.

10. The high-throughput heat exchange tube according to claim 9, characterized in that, The diameter of the high-throughput heat exchange tube is ≥10cm.

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