A thermal spraying flame heat recovery and recycling device based on emissivity regulation

Abstract

The application discloses a thermal spraying flame heat recovery and recycling device based on emissivity regulation, and aims at solving the problems of serious flame heat dissipation, low energy utilization rate and insufficient melting of high melting point powder in the existing plasma thermal spraying process. The thermal spraying flame heat recovery and recycling device is provided with a heat recovery cover at the outlet end of a plasma thermal spraying device, the heat recovery cover is a high-temperature-resistant shell, the high-temperature-resistant shell is internally provided with a hollow cavity, the hollow cavity forms a vacuum heat insulation interlayer, the inner surface of the cover of the high-temperature-resistant shell is provided with a high-emissivity coating, the high-emissivity coating is a perovskite coating, a spinel coating or a pyrochlore / defect fluorite coating, the outer surface of the cover of the high-temperature-resistant shell is provided with a low-emissivity coating, and the low-emissivity coating is a metal-doped ZnO coating. The thermal spraying flame heat recovery and recycling device can not only significantly improve the energy utilization rate of the thermal spraying flame, but also improve the coating quality and service protection performance.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of modern surface engineering technology, thermal spraying energy-saving equipment technology, and high-temperature infrared radiation coating control technology. Specifically, it relates to a plasma thermal spraying flame heat recovery and reuse device based on high and low emissivity coating coupling control and vacuum insulation synergy. Background Technology

[0002] Thermal spraying technology is a core modification technology with the greatest engineering value and industrialization prospects in the field of modern surface engineering. It relies on a high-temperature heat source to heat powders such as metals, alloys, ceramics, cermets, and composite materials to a molten or semi-molten state, and then atomizes and deposits them on the substrate surface with a high-speed jet. It can directionally prepare multi-functional integrated coatings with wear resistance and friction reduction, corrosion protection, high-temperature oxidation resistance, thermal barrier insulation, electrical insulation / conductivity, erosion resistance, and dimensional repair. It fundamentally solves the failure problems of high-end equipment components under harsh conditions such as high temperature, high pressure, corrosion, wear, and fatigue, significantly extending service life, reducing maintenance costs, and improving the overall reliability of equipment.

[0003] Currently, thermal spraying has fully covered national strategic pillar industries such as aerospace, energy and power, advanced manufacturing, petrochemicals, shipbuilding, rail transportation, and metallurgical machinery. It is an essential core process for surface strengthening and remanufacturing of key components such as hot-end parts of aero engines, gas turbine blades, blast furnace tuyeres, chemical reactors, mechanical shafts, molds, and valves, providing key technical support for the iterative upgrading of high-end equipment manufacturing towards high performance, long life, and green and low-carbon directions.

[0004] Plasma thermal spraying, with its outstanding advantages such as high flame temperature, high energy density, wide material adaptability, and strong process controllability, has become the preferred process for preparing high-melting-point, high-performance coating materials such as refractory metals, high-temperature alloys, structural ceramics, thermal barrier coatings, and rare-earth functional ceramics, and is a core technological guarantee for the high-end surface protection field. However, in the process of continuous industrial production, plasma thermal spraying has inherent technical bottlenecks that are difficult to avoid, becoming a key obstacle to improving quality and efficiency and promoting green development in the industry: First, the energy utilization rate of the plasma flame is extremely low, resulting in significant energy waste. After exiting the spray gun, the plasma arc rapidly radiates heat to the surrounding environment in a disorderly manner, and a large amount of high-temperature heat energy is dissipated without being effectively used in the powder heating and melting process. The effective energy actually used for powder melting accounts for less than 30% of the total input energy, which not only significantly increases production energy consumption and manufacturing costs, but also exacerbates the accumulation of high-temperature heat in the on-site working environment and accelerates equipment heat loss, which is seriously contrary to the development orientation of green, low-carbon, energy-saving and consumption-reducing manufacturing industry. Second, the high-melting-point powder is not fully melted, making it difficult to meet the overall performance standards of the coating. For refractory alloys such as tungsten, molybdenum, and tantalum, structural / functional ceramics such as zirconium oxide, alumina, spinel, and perovskite, and special thermal barrier coating powders, insufficient effective heat from the flame prevents complete melting during the deposition process. This results in low particle melting degree, poor fluidity and spreadability, ultimately leading to high internal porosity, weak interlayer bonding, and insufficient bonding strength with the substrate. This easily causes problems such as coating cracking, peeling, and protective failure, severely limiting the service stability and lifespan of high-end coatings. Thirdly, traditional improvement solutions have fundamental flaws and cannot solve the problem at its root. The industry commonly uses methods such as simply increasing spraying power, extending the flame distance, and preheating powder raw materials to improve powder melting. These methods can only partially alleviate the problem of insufficient melting and cannot address the core issue of heat dissipation from the flame. Instead, they further increase energy consumption, reduce flame stability, and exacerbate substrate thermal deformation. At the same time, they can easily lead to coarse coating structure, increased residual stress, difficulty in accurately controlling spraying quality, and difficulty in ensuring product consistency.

[0005] High-temperature infrared emissivity coatings are key functional materials for achieving efficient thermal energy regulation. High-emissivity coatings possess excellent infrared radiation and directional thermal reflection characteristics under high-temperature conditions, enabling them to focus and return radiant heat energy lost from the environment to the core heat source area, achieving in-situ energy recovery and efficient utilization. Low-emissivity coatings, with their low infrared emissivity and high thermal reflectivity, can significantly suppress radiative heat dissipation from the component surface to the outside, effectively blocking heat leakage paths. Currently, both types of coatings are mostly used individually in single scenarios such as high-temperature insulation, industrial energy-saving insulation, and infrared stealth. Mature technologies and specialized equipment for functionally coupling high-emissivity heat recovery and low-emissivity heat blocking, and applying them to precise control of plasma thermal spray flame energy, have not yet been developed.

[0006] Therefore, in order to meet the dual core needs of energy saving and consumption reduction and coating quality improvement in plasma thermal spraying, a high emissivity coating, a low emissivity coating, a double-layer vacuum insulation structure and a high-temperature resistant shell are integrated into a single design. A dedicated flame heat recovery and reuse device is developed to achieve efficient control of flame energy throughout the entire process from three dimensions: heat recovery, heat dissipation suppression and multi-level insulation. This has become an inevitable technical path to break through existing technical bottlenecks and promote the upgrading of thermal spraying processes. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of severe heat dissipation of the flame, low energy utilization rate, and insufficient melting of high melting point powder in the existing plasma thermal spraying process, and to provide a thermal spraying flame heat recovery and reuse device based on emissivity regulation.

[0008] The present invention relates to a heat recovery and reuse device for thermal spraying flame based on emissivity regulation. A heat recovery hood is provided at the spray gun outlet of a plasma thermal spraying device. The heat recovery hood is a high-temperature resistant shell with a hollow cavity inside, forming a vacuum insulation interlayer. The inner surface of the high-temperature resistant shell has a high-emissivity coating, which is a perovskite coating, a spinel coating, or a pyrochlore / defective fluorite coating. The outer surface of the high-temperature resistant shell has a low-emissivity coating, which is a metal-doped ZnO coating.

[0009] The process for preparing a metal-doped ZnO coating on a high-temperature resistant shell is as follows:

[0010] Step 1: Mix Zn(NO3)2•6H2O and metal nitrate to prepare a mixed salt solution, then add ammonia water dropwise to adjust the pH of the system to 8~9, carry out a co-precipitation reaction, collect the solid after aging, wash and dry it, calcine it at 700~900℃, and grind it to obtain metal-doped ZnO-based material.

[0011] Step 2: Using metal-doped ZnO-based material as the spraying raw material, a cold spraying process is adopted, with N2 as the working gas, the gas pressure is controlled at 1.8~2.2 MPa, the N2 gas preheating temperature is 280~350 ℃, and the high-temperature shell temperature is 100~130℃. The metal-doped ZnO coating is prepared on the high-temperature shell by layer deposition.

[0012] The metal nitrate mentioned in step one is one or more of aluminum nitrate, iron nitrate, cobalt nitrate, cerium nitrate, and magnesium nitrate, and the molar ratio of the metal element in the metal-doped ZnO-based material is 1% to 5%.

[0013] This invention relates to a thermal spraying flame heat recovery and reuse device based on emissivity coating regulation. By sealing and installing a horn-shaped heat recovery cover that integrates a high emissivity heat-reflective coating and a low emissivity heat-suppressing coating at the outlet of the thermal spraying gun, a multi-level synergistic regulation system is constructed, which integrates internal heat recovery, intermediate heat insulation and blocking, and external heat dissipation suppression. This achieves efficient recovery and reuse of plasma flame heat, promotes full melting of sprayed powder, and achieves the core effects of energy saving, consumption reduction and improved coating quality.

[0014] The heat recovery hood comprises, from the inside out, a high emissivity coating, a high-temperature resistant shell, a vacuum interlayer, and a low emissivity coating. In operation, the inner high emissivity coating directly faces the plasma flame, directionally reflecting the radiant heat lost from the flame back to the core region of the plasma arc, achieving in-situ heat recovery and recycling. The outer low emissivity coating suppresses radiative heat dissipation from the surface of the heat recovery hood towards the environment, minimizing heat loss. The double-layer vacuum interlayer efficiently blocks heat conduction and convection paths, forming a stable high-temperature insulation structure in conjunction with the high-temperature resistant shell. Ultimately, this achieves dual suppression of internal heat reflection and accumulation, and external heat dissipation, simultaneously completing the efficient recovery and reuse of heat from the thermal spraying flame.

[0015] Compared with traditional plasma spraying equipment, the thermal spraying flame heat recovery and reuse device based on emissivity regulation of the present invention has the following technical advantages:

[0016] 1. High energy recovery efficiency and significant energy saving effect: The high emissivity coating directionally transfers and dissipates heat, while the low emissivity coating and the double-layer vacuum interlayer form a double heat dissipation barrier, improving energy utilization by more than 30%. It can meet the melting requirements of high melting point powder without significantly increasing the spraying power, thereby reducing production energy consumption from the source.

[0017] 2. The coating quality is greatly improved and the performance is stable and reliable: The flame has sufficient effective heat, and high-melting-point powders such as refractory alloys and ceramics can be fully melted. The coating porosity is significantly reduced, the bonding strength with the substrate is significantly improved, and the coating density, protective performance and service life are optimized simultaneously.

[0018] 3. Strong high-temperature stability and suitable for long-term working conditions: The high-temperature resistant shell is made of CC composite material or high-temperature alloy, which has excellent temperature resistance and good high-temperature dimensional stability. It can be adapted to long-term high-temperature continuous operation conditions of plasma spraying, and the structure is not easy to deform or fail.

[0019] 4. Excellent adaptability and practicality, with high promotion value: The trumpet-shaped structure design does not interfere with the normal spraying process, is easy to install and modify, can be adapted to mainstream plasma thermal spraying equipment, and is suitable for spraying and processing a variety of high melting point materials, with broad prospects for industrial application. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to the present invention.

[0021] Figure 2 The phase composition test diagram of the low emissivity Al-doped ZnO coating in the example is shown.

[0022] Figure 3 The image shows the morphology of the low emissivity Al-doped ZnO coating in the example.

[0023] Figure 4 This is a phase composition test diagram of the high emissivity Cr-doped yttrium niobate coating in the examples;

[0024] Figure 5 The image shows the morphology of the high-emissivity Cr-doped yttrium niobate coating in the example.

[0025] Figure 6 The image shown is an electron microscope image of the coating morphology after spraying using a thermal spraying flame heat recovery and reuse device based on emissivity regulation, as described in this embodiment. Detailed Implementation

[0026] Specific Implementation Method 1: This implementation method is based on a heat recovery and reuse device for thermal spraying flames with emissivity regulation. A heat recovery hood is installed at the spray gun outlet of the plasma thermal spraying device. The heat recovery hood is a high-temperature resistant shell with a hollow cavity inside, forming a vacuum insulation interlayer. The inner surface of the high-temperature resistant shell has a high-emissivity coating, which is a perovskite coating, spinel coating, or pyrochlore / defective fluorite coating. The outer surface of the high-temperature resistant shell has a low-emissivity coating, which is a metal-doped ZnO coating.

[0027] The process for preparing a metal-doped ZnO coating on a high-temperature resistant shell is as follows:

[0028] Step 1: Mix Zn(NO3)2•6H2O and metal nitrate to prepare a mixed salt solution, then add ammonia water dropwise to adjust the pH of the system to 8~9, carry out a co-precipitation reaction, collect the solid after aging, wash and dry it, calcine it at 700~900℃, and grind it to obtain metal-doped ZnO-based material.

[0029] Step 2: Using metal-doped ZnO-based material as the spraying raw material, a cold spraying process is adopted, with N2 as the working gas, the gas pressure is controlled at 1.8~2.2 MPa, the N2 gas preheating temperature is 280~350 ℃, and the high-temperature shell temperature is 100~130℃. The metal-doped ZnO coating is prepared on the high-temperature shell by layer deposition.

[0030] The metal nitrate mentioned in step one is one or more of aluminum nitrate, iron nitrate, cobalt nitrate, cerium nitrate, and magnesium nitrate, and the molar ratio of the metal element in the metal-doped ZnO-based material is 1% to 5%.

[0031] This implementation focuses on the core directions of energy saving, efficient energy recovery, and improved coating quality in plasma thermal spraying processes. It is particularly suitable for plasma spraying of high-melting-point powders such as refractory metals, high-temperature alloys, structural ceramics, and thermal barrier coating materials. It can widely serve the surface protection coating needs of high-end equipment such as aerospace engine hot-end components, high-temperature energy and power equipment, key wear-resistant and corrosion-resistant components in mechanical manufacturing, and high-temperature pressure-bearing parts in petrochemicals. It also covers sub-technical directions such as energy-saving retrofitting of thermal spraying equipment, in-situ recovery of high-temperature thermal radiation energy, application of CC composite materials in high-temperature structural components, and functional coupling design of high and low emissivity coatings. It is a key equipment technology for improving the quality and efficiency of thermal spraying processes and achieving green energy saving in high-end manufacturing fields.

[0032] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the heat recovery cover is funnel-shaped.

[0033] In this embodiment, the trumpet-shaped heat recovery hood gradually increases in size along the jet direction of the plasma flame.

[0034] Specific Implementation Method 3: The difference between this implementation method and Specific Implementation Method 2 is that the outlet diameter of the heat recovery hood is 1.5 to 3 times the inlet diameter.

[0035] In this embodiment, the inlet diameter is matched with the outer diameter of the spray gun outlet and a sealed assembly is achieved. The outlet diameter is 1.5 to 3 times the inlet diameter. Without interfering with the flame pattern, spray trajectory and deposition process, the flame radiation area is maximized, further improving the heat recovery efficiency.

[0036] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the high-temperature resistant shell is made of CC composite material or high-temperature alloy.

[0037] In this embodiment, the high-temperature resistant shell is made of materials with excellent high-temperature structural stability, such as CC composite material and high-temperature alloy. The inner and outer surfaces of the heat insulation protective layer are roughened by sandblasting to improve the interfacial bonding strength with the high-emissivity coating and the low-emissivity coating, and to prevent the coating from peeling off under high-temperature cycling.

[0038] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that when the high emissivity coating is a perovskite coating, the perovskite coating is LaCr. 1-x Mg x O3 coating, Gd 1-x Ca xCoO3 coating or Cr-doped yttrium niobate coating; when the high-emissivity coating is a spinel coating, the spinel coating is (Cu, Mn)(Co, Fe, Cr)2O4 coating or MgCr. 1.6 Ti 0.4 O 4.2 Coating; when the high emissivity coating is a pyrochlore / defective fluorite coating, the pyrochlore / defective fluorite coating is a Ca / Cr co-doped Y3NbO7 coating or (La 0.25 Sm 0.25 Eu 0.25 Gd 0.25 )2Hf2O7 coating.

[0039] In this embodiment, a high emissivity coating is applied to the inside of the heat recovery hood of the thermal spraying flame. The high emissivity coating has an emissivity of ≥0.85 at room temperature and ≥0.75 at 1200℃. The surface roughness Ra of the coating is ≥3.2~6.3.

[0040] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that, when the high emissivity coating is a Cr-doped yttrium niobate coating, the process for preparing the Cr-doped yttrium niobate coating on the high-temperature resistant shell is as follows:

[0041] I. According to Y (Nb) 0.9 Cr 0.1 The stoichiometric ratio of Y2O3, Nb2O5 and Cr2O3 was mixed and wet ball milled with anhydrous ethanol as the medium. After drying, a mixed precursor was obtained, which was calcined at 1100~1300℃ and ground to obtain Cr-doped YNbO4 powder.

[0042] 2. Using plasma spraying technology, Ar is used as the main gas with a flow rate of 40~45 slpm, H2 is used as the auxiliary gas with a flow rate of 8~10 slpm, and Cr-doped YNbO4 powder is used as the spraying material. The coating is deposited layer by layer to prepare a Cr-doped yttrium niobate coating on a high-temperature resistant shell.

[0043] This embodiment uses a high-temperature solid-state method to prepare 10 at% Cr-doped yttrium niobate (Y(Nb) 0.9 Cr 0.1 O4 powder is then used to prepare a high emissivity coating on a high-temperature resistant shell using a plasma spraying process.

[0044] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the thickness of the Cr-doped yttrium niobate coating is 150~500μm.

[0045] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that, during the preparation of the metal-doped ZnO coating, the spraying distance is controlled to be 15-20 mm, the spray gun scanning speed is 400-500 mm / s, and the powder feeding rate is 10-15 g / min in the cold spraying process.

[0046] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the thickness of the metal-doped ZnO coating is 80~120μm.

[0047] In this embodiment, the low emissivity coating has an emissivity of ≤0.5 at room temperature and ≤0.3 at 600℃, and a surface roughness Ra of ≤0.5μm.

[0048] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the thickness of the vacuum insulation interlayer is 6~10mm.

[0049] Example: This example of a heat recovery and reuse device for emissivity-controlled thermal spraying flame is a heat recovery hood installed at the nozzle outlet of a plasma thermal spraying device. The heat recovery hood is made of CC composite material and is horn-shaped. The high-temperature resistant shell has a hollow cavity inside, forming a vacuum insulation interlayer with a total thickness of 8 mm to reduce heat conduction and convection losses. The inner surface of the high-temperature resistant shell has a Cr-doped YNbO4 high emissivity coating; the outer surface of the high-temperature resistant shell has a low emissivity coating, which is an Al-doped ZnO coating.

[0050] The process for preparing an Al-doped ZnO coating on a high-temperature resistant shell is as follows:

[0051] Step 1: Prepare a 100 mL mixed salt solution by mixing Zn(NO3)2•6H2O and Al(NO3)3•9H2O at a molar ratio of Al / (Zn+Al)=3% (n(Zn²⁺)=0.097 mol, n(Al³⁺)=0.003 mol). Under magnetic stirring, add ammonia water (25% by mass) dropwise to adjust the pH of the system to 8.5, and carry out the Zn(OH)2-Al(OH)3 coprecipitation reaction. After aging at room temperature for 2 h, collect the solid phase, wash, dry at 80℃, calcine at 800℃ for 2 h, and grind after natural cooling to obtain Al-doped ZnO-based material.

[0052] Step 2: Using metal-doped ZnO-based material as the coating material, a cold spraying process is adopted, with N2 as the working gas, the gas pressure controlled at 3.0 MPa, the N2 gas preheating temperature at 350℃, the spraying distance at 20 mm, the spray gun scanning speed at 250 mm / s, the powder feeding rate at 10 g / min, and the high-temperature resistant shell heating temperature at 100℃. Layer-by-layer deposition is carried out to prepare an Al-doped ZnO coating on the high-temperature resistant shell.

[0053] The process for preparing a Cr-doped yttrium niobate coating on a high-temperature resistant shell is as follows:

[0054] I. According to Y (Nb) 0.9 Cr 0.1 The stoichiometric ratio of O4 was determined by mixing Y2O3, Nb2O5 and Cr2O3, wet ball milling for 5 h with anhydrous ethanol as the medium, drying at 80 ℃ to obtain a mixed precursor, pre-calcining the mixed precursor at 700 ℃ for 2 h, grinding it again and calcining it at 1150 ℃ for 3 h, and grinding it to obtain Cr-doped YNbO4 powder.

[0055] II. A plasma spraying process was adopted, with Ar as the main gas at a flow rate of 45 slpm and H2 as the auxiliary gas at a flow rate of 10 slpm. Cr-doped YNbO4 powder was used as the spraying material. The spraying power was 40kW, the spraying distance was 120mm, the powder feeding rate was 30g / min, and the spray gun moving speed was 200mm / s. Cr-doped yttrium niobate coating was prepared on a high-temperature resistant shell by layer-by-layer deposition.

[0056] In this embodiment, the high-temperature resistant shell of the heat recovery hood is made of CC composite material with a thickness of 5mm. The inner and outer surfaces are roughened by sandblasting. The high-emissivity coating on the inner side is a Cr-doped yttrium niobate perovskite coating, prepared by plasma spraying. The coating thickness is 200μm, the emissivity at room temperature is 0.88, the emissivity at 1200℃ is 0.78, and the surface roughness is Ra4.5μm. The low-emissivity coating on the outer side is an Al-doped ZnO coating with an Al doping ratio of 3%, prepared by cold spraying. The coating thickness is 100μm, the emissivity at room temperature is 0.32, the emissivity at 600℃ is 0.26, and the surface roughness is Ra0.3μm. The vacuum jacket is a double-layer structure with a vacuum degree of 5Pa and a total thickness of 8mm. The inlet diameter of the heat recovery hood matches the outlet diameter of the spray gun, and the outlet diameter is twice the inlet diameter. This invention constructs a multi-level heat regulation system of "internal recovery, external barrier, and internal insulation" by sealing and assembling a trumpet-shaped heat recovery cover at the outlet end of a thermal spray gun. The cover integrates a high emissivity heat reflection coating, a high-temperature resistant shell of CC composite material / high-temperature alloy, a double-layer vacuum insulation interlayer, and a low emissivity heat-suppressing coating from the inside out.

[0057] During operation, the high emissivity coating on the inner side directionally reflects the radiative heat lost by the plasma flame back to the core area of ​​the flame, achieving in-situ heat recovery and reuse; the low emissivity coating on the outer side inhibits radiative heat dissipation from the surface of the enclosure to the environment, reducing heat loss; the double-layer vacuum interlayer efficiently blocks the heat conduction and heat convection heat transfer paths, and together with the high-temperature resistant shell, ensures the high-temperature stability of the structure.

[0058] The plasma spraying of zirconia-based ceramic powder using the thermal spraying flame heat recovery and reuse device of this embodiment results in sufficient powder melting, low coating porosity, and a dense coating. The zirconia-based ceramic coating prepared using this thermal spraying flame heat recovery and reuse device exhibits significant advantages: a dense coating structure, uniform and regular surface morphology, no obvious cracks, unmelted particles, or interlayer defects, a tight bond between the coating and the substrate / shell interface without peeling gaps, and excellent microstructural continuity and integrity. Conventional plasma-sprayed zirconia-based ceramic coatings have a porosity of 5.0%~8.0%, and suffer from insufficient powder melting, loose and porous coatings, and low bonding strength. Using the device of this embodiment for plasma spraying of zirconia-based ceramic powder results in sufficient powder melting, a coating porosity ≤2.0%, a dense coating, and significantly improved bonding strength and protective performance.

[0059] When the heat recovery hood is not coated with either a high-emissivity or low-emissivity coating (only the high-temperature resistant shell and vacuum interlayer are retained), the corresponding performance data are: energy efficiency ≈ 35%, zirconia coating porosity ≈ 5.2%, coating-substrate bonding strength ≈ 30 MPa, heat recovery hood outer surface temperature ≈ 320 ℃, and plasma flame core average temperature ≈ 7200 ℃. Key performance test data for the thermal spraying flame heat recovery and reuse device in this embodiment are: energy efficiency ≥ 60%, zirconia coating porosity ≤ 2.0%, coating-substrate bonding strength ≥ 45 MPa, heat recovery hood outer surface temperature ≤ 180 ℃, and plasma flame core average temperature ≥ 8500 ℃.

Claims

1. A device for recovering and reusing heat from thermal spraying flames based on emissivity regulation, characterized in that... The heat recovery and reuse device for thermal spraying flame based on emissivity regulation is a heat recovery hood installed at the spray gun outlet of the plasma thermal spraying device. The heat recovery hood is a high-temperature resistant shell with a hollow cavity inside, forming a vacuum insulation interlayer. The inner surface of the high-temperature resistant shell has a high-emissivity coating, which is a perovskite coating, spinel coating, or pyrochlore / defective fluorite coating. The outer surface of the high-temperature resistant shell has a low-emissivity coating, which is a metal-doped ZnO coating. The process for preparing a metal-doped ZnO coating on a high-temperature resistant shell is as follows: Step 1: Mix Zn(NO3)2•6H2O and metal nitrate to prepare a mixed salt solution, then add ammonia water dropwise to adjust the pH of the system to 8~9, carry out a co-precipitation reaction, collect the solid after aging, wash and dry it, calcine it at 700~900℃, and grind it to obtain metal-doped ZnO-based material. Step 2: Using metal-doped ZnO-based material as the spraying raw material, a cold spraying process is adopted, with N2 as the working gas, the gas pressure is controlled at 1.8~2.2 MPa, the N2 gas preheating temperature is 280~350 ℃, and the high-temperature shell temperature is 100~130℃. The metal-doped ZnO coating is prepared on the high-temperature shell by layer deposition. The metal nitrate mentioned in step one is one or more of aluminum nitrate, iron nitrate, cobalt nitrate, cerium nitrate, and magnesium nitrate, and the molar ratio of the metal element in the metal-doped ZnO-based material is 1% to 5%.

2. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 1, characterized in that... The heat recovery hood is funnel-shaped.

3. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 2, characterized in that... The outlet diameter of the heat recovery hood is 1.5 to 3 times the inlet diameter.

4. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 1, characterized in that... The high-temperature resistant shell is made of CC composite material or high-temperature alloy.

5. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 1, characterized in that... When the high emissivity coating is a perovskite coating, the perovskite coating is LaCr. 1-x Mg x O3 coating, Gd 1-x Ca x CoO3 coating or Cr-doped yttrium niobate coating; when the high-emissivity coating is a spinel coating, the spinel coating is (Cu, Mn)(Co,Fe, Cr)2O4 coating or MgCr 1.6 Ti 0.4 O 4.2 Coating; when the high emissivity coating is a pyrochlore / defective fluorite coating, the pyrochlore / defective fluorite coating is a Ca / Cr co-doped Y3NbO7 coating or (La 0.25 Sm 0.25 Eu 0.25 Gd 0.25 )2Hf2O7 coating.

6. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 5, characterized in that... When the high emissivity coating is a Cr-doped yttrium niobate coating, the process for preparing the Cr-doped yttrium niobate coating on the high-temperature resistant shell is as follows: I. According to Y (Nb) 0.9 Cr 0.1 The stoichiometric ratio of Y2O3, Nb2O5 and Cr2O3 was mixed and wet ball milled with anhydrous ethanol as the medium. After drying, a mixed precursor was obtained, which was calcined at 1100~1300℃ and ground to obtain Cr-doped YNbO4 powder.

2. Using plasma spraying technology, Ar is used as the main gas with a flow rate of 40~45 slpm, H2 is used as the auxiliary gas with a flow rate of 8~10 slpm, and Cr-doped YNbO4 powder is used as the spraying material. The coating is deposited layer by layer to prepare a Cr-doped yttrium niobate coating on a high-temperature resistant shell.

7. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 6, characterized in that... The thickness of the Cr-doped yttrium niobate coating is 150~500μm.

8. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 1, characterized in that... In the process of preparing metal-doped ZnO coatings, the spraying distance is controlled at 15~20 mm, the spray gun scanning speed is 400~500 mm / s, and the powder feeding rate is 10~15 g / min in the cold spraying process.

9. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 1, characterized in that... The thickness of the metal-doped ZnO coating is 80~120μm.

10. The heat recovery and reuse device for thermal spraying flame based on emissivity regulation according to claim 1, characterized in that... The thickness of the vacuum insulation interlayer is 6~10mm.

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