Coating for a corrosion-resistant thermocouple for waste power generation and its preparation method

Abstract

The present invention provides a coating for a corrosion-resistant thermocouple used in waste power generation and a preparation method thereof, belonging to the field of coatings. The coating includes: a transition layer, which is attached to the surface of the metal protective sleeve of the thermocouple. In terms of parts by weight, the coating of the transition layer is composed of the following chemical components: 40-60 parts of Al-Ni intermetallic compound, 20-40 parts of metal-ceramic composite material, and 10-20 parts of high-expansion alloy; and a functional layer, which is attached to the surface of the transition layer. In terms of parts by weight, the coating of the functional layer is composed of the following chemical components: 20-50 parts of nickel-based self-fluxing alloy, 5-10 parts of ZrO2, 2-7 parts of ZrC, 5-10 parts of SiO2, 2-8 parts of Al2O3, 5-10 parts of Y2O3-coated WO3 composite material, 5-10 parts of inorganic nano-composite binder, 1-3 parts of dispersant, and 20-50 parts of solvent. Thereby, the high-temperature resistance, corrosion resistance, and wear resistance of the metal protective sleeve of the thermocouple used in waste power generation are improved simultaneously.

Description

Technical Field

[0001] The present application relates to the technical field of coatings, and particularly to a coating for a corrosion-resistant thermocouple used in waste power generation and a preparation method thereof. Background Art

[0002] A thermocouple mainly consists of parts such as a thermal electrode, an insulating tube, a metal protective casing, and a junction box. Among them, the thermal electrode and the insulating tube are placed in the metal protective casing to achieve the protection and support of the thermocouple. The thermocouple can directly measure the temperature and convert the temperature signal into a thermal electromotive force signal, which is further converted into the temperature of the measured medium through an electrical instrument. In waste incineration power plants, thermocouples are widely used for temperature measurement at key positions such as the furnace chamber and flue gas duct. Since the flue gas generated during waste incineration has a high temperature, strong corrosiveness, and contains a large amount of slag, ash, and dust, the thermocouple needs to have excellent high-temperature resistance, corrosion resistance, and wear resistance.

[0003] By electroplating or spraying ceramic coatings on the surface of the metal protective casing of the thermocouple, the corrosion resistance of the thermocouple can be improved to a certain extent. However, problems such as poor adhesion of the existing coatings, insufficient corrosion resistance of the coatings, and low hardness of the coatings seriously restrict the further development of the coatings.

[0004] Chinese Patent CN114645269B discloses a high-temperature resistant ceramic coating for a thermocouple used in a waste incinerator and a preparation method thereof. By adding components such as ceramic aggregates, titanium particles wrapped with boron nitride, and flaky aluminum powder, and making full use of the physical and chemical effects between the components, a dense high-temperature resistant coating is formed. However, the thermal expansion coefficients of the high-temperature resistant coating and the metal protective casing of the thermocouple are quite different, resulting in the coating being prone to expansion and cracking, reducing the service life of the thermocouple; Chinese Patent CN115572934A discloses an anti-corrosion and wear-resistant composite coating applied to the heating surface of a waste incineration power generation boiler. By forming a mechanical pinning effect, the bonding strength between the transition layer and the ceramic surface layer is enhanced, thus ensuring the coating quality. The ceramic coating as the surface layer not only increases the erosion resistance of the coating, improves the service life of the boiler pipeline, but also has an electrochemical protection and physical shielding effect. However, the ceramic surface layer selects conventional erosion-resistant materials with relatively low hardness and cannot withstand the erosion of high temperature and corrosive substances, resulting in the coating being prone to wear and damage.

[0005] Therefore, how to simultaneously improve the high-temperature resistance, corrosion resistance, and wear resistance of the metal protective casing of the thermocouple used in waste power generation, so as to improve the service life of the thermocouple at high temperatures, is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0006] The present application provides a coating for a corrosion-resistant thermocouple used in waste power generation and a preparation method thereof to solve the following technical problems: how to simultaneously improve the high-temperature resistance, corrosion resistance, and wear resistance of the metal protection sleeve of the thermocouple used in waste power generation.

[0007] In a first aspect, the present application provides a coating for a corrosion-resistant thermocouple used in waste power generation, and the coating includes:

[0008] A transition layer, the transition layer is attached to the surface of the metal protection sleeve of the thermocouple. By weight, the coating of the transition layer is composed of the following chemical components: 40-60 parts of Al-Ni intermetallic compound, 20-40 parts of metal ceramic composite, and 10-20 parts of high-expansion alloy; and

[0009] A functional layer, the functional layer is attached to the surface of the transition layer. By weight, the coating of the functional layer is composed of the following chemical components: 20-50 parts of nickel-based self-fluxing alloy, 5-10 parts of ZrO 2 is 5-10 parts, ZrC is 2-7 parts, SiO 2 is 5-10 parts, Al 2 O 3 is 2-8 parts, Y 2 O 3 coated WO 3 composite material is 5-10 parts, inorganic nano-composite binder is 5-10 parts, dispersant is 1-3 parts, and solvent is 20-50 parts;

[0010] Among them, the metal ceramic composite is composed of alumina-based metal ceramic and silicon nitride-based metal ceramic, and the mass ratio of the alumina-based metal ceramic to the silicon nitride-based metal ceramic is 1:(1-3).

[0011] Optionally, the nickel-based self-fluxing alloy includes: one or more of NiCo23Cr17Al12Y0.5, NiCo23Cr20Al8.5Ta4Y0.1, and CoNi32Cr21Al8Y0.5; and / or,

[0012] The high-expansion alloy includes: one or more of Cu60Zn40, FeNi22Cr3, FeNi20Mn6, FeNi13Mn7, and Mn72Cr18Ni10.

[0013] Optionally, the inorganic nano-composite binder includes: one or more of aluminum dihydrogen phosphate, silica sol, and aluminum sol.

[0014] Optionally, the Y 2 O 3 coated WO 3 composite material is a core-shell structure, wherein Y 2 O3 The mass of which is the Y 2 O 3 Coated WO 3 1 to 10% of the total mass of the composite material.

[0015] Optionally, the thickness of the transition layer is 40 to 80 μm, and the thickness of the functional layer is 50 to 200 μm.

[0016] Optionally, the coating satisfies the following properties: microhardness HV≥600, porosity <0.5%, and the service life of the thermocouple at 1300 °C > 180 d.

[0017] In a second aspect, the present application provides a method for preparing a coating according to any one of the embodiments in the first aspect, and the preparation method includes:

[0018] Shot peening the thermocouple metal protection sleeve;

[0019] Spraying the coating of the transition layer onto the surface of the thermocouple metal protection sleeve to form a transition layer on the surface of the thermocouple metal protection sleeve;

[0020] Coating the coating of the functional layer on the surface of the transition layer, and then performing a curing treatment to form a functional layer on the surface of the transition layer.

[0021] Optionally, the preparation method of the coating of the functional layer includes:

[0022] Performing ball milling on SiO 2 and Al 2 O 3 , then adding an inorganic nano-composite binder, and continuing the ball milling treatment to obtain a first mixture;

[0023] Performing ball milling on nickel-based self-fluxing alloy, ZrO 2 , ZrC, a dispersant and a solvent to obtain a second mixture;

[0024] Mixing the first mixture, the second mixture and Y 2 O 3 Coated WO 3 The composite material to obtain the coating of the functional layer.

[0025] Optionally, the preparation method of the Y 2 O 3 Coated WO 3 Composite material includes:

[0026] Dissolving Y 2 O 3 in dilute nitric acid to obtain a mixed solution;

[0027] Immerse WO 3 in the above-mentioned mixed solution, and then perform solid-liquid separation to obtain a precursor;

[0028] Subject the precursor to high-temperature calcination to obtain Y 2 O 3 coated WO 3 composite material; the temperature of the high-temperature calcination is 900-1000 °C, and the time of the high-temperature calcination is 60-180 min.

[0029] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0030] The present application provides a coating for a corrosion-resistant thermocouple used in waste power generation. First, a composite coating structure of a transition layer and a functional layer is adopted. The transition layer mainly plays a role in enhancing the bonding force between the functional coating and the metal protection sleeve. The multiple components of the functional layer can form a multi-level protection, effectively isolating the contact between the corrosive medium and the metal protection sleeve of the thermocouple; second, the composition of the coating of the transition layer is reasonably designed. The Al-Ni intermetallic compound and the metal-ceramic composite material in the transition layer significantly enhance the bonding force between the coating and the metal protection sleeve through the synergistic effect at the molecular level, and effectively alleviate the problem of coating peeling caused by the difference in thermal expansion coefficient; third, the chemical composition of the coating of the functional layer is reasonably designed. Components such as nickel-based self-fluxing alloy, ZrO 2 , ZrC, etc. form a stable metal-ceramic composite structure, improving the hardness and wear resistance of the coating. At the same time, SiO 2 , Al 2 O 3 and Y 2 O 3 coated WO 3 composite materials and other components form a dense oxide network structure, enhancing the corrosion resistance and high-temperature resistance of the coating. In addition, the inorganic nano-composite binder tightly binds each component together through a tight bonding effect, improving the overall strength and toughness of the coating. The dispersant ensures the uniform dispersion of each component in the coating, avoiding the occurrence of agglomeration and precipitation phenomena, thereby improving the uniformity and stability of the coating; finally, through the combined action of the composite coating structure of the transition layer and the functional layer, the reasonable design of the composition of the coating of the transition layer, and the reasonable design of the chemical composition of the coating of the functional layer, the high-temperature resistance, corrosion resistance and wear resistance of the metal protection sleeve of the thermocouple used in waste power generation are improved simultaneously. Description of the Drawings

[0031] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments in line with the present application, and are used together with the specification to explain the principles of the present application.

[0032] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 Schematic diagram of a coating for a corrosion-resistant thermocouple used in waste power generation provided by an embodiment of the present application;

[0034] Figure 2 Flow chart of a preparation method for a coating of a corrosion-resistant thermocouple used in waste power generation provided by an embodiment of the present application;

[0035] Reference numerals:

[0036] 1 - Thermocouple metal protection sleeve matrix, 2 - Transition layer, 3 - Functional layer. Detailed implementation manners

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0038] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchases or can be prepared by existing methods.

[0039] Figure 1 Schematic diagram of a coating for a corrosion-resistant thermocouple used in waste power generation provided by an embodiment of the present application.

[0040] The present application provides a coating for a corrosion-resistant thermocouple used in waste power generation, as Figure 1 shown, the coating includes:

[0041] A transition layer, the transition layer adheres to the surface of the thermocouple metal protection sleeve. By weight, the coating of the transition layer consists of the following chemical components: 40 - 60 parts of Al-Ni intermetallic compound, 20 - 40 parts of metal ceramic composite material, and 10 - 20 parts of high-expansion alloy; and

[0042] A functional layer, the functional layer adheres to the surface of the transition layer. By weight, the coating of the functional layer consists of the following chemical components: 20 - 50 parts of nickel-based self-fluxing alloy, ZrO 2is 5 to 10 parts, ZrC is 2 to 7 parts, SiO 2 is 5 to 10 parts, Al 2 O 3 is 2 to 8 parts, Y 2 O 3 coated WO 3 The composite material is 5 to 10 parts, the inorganic nano-composite binder is 5 to 10 parts, the dispersant is 1 to 3 parts, and the solvent is 20 to 50 parts;

[0043] Among them, the cermet composite material is composed of alumina-based cermet and silicon nitride-based cermet, and the mass ratio of the alumina-based cermet to the silicon nitride-based cermet is 1:(1 - 3).

[0044] Through the combined action of the composite coating structure of the transition layer and the functional layer, the reasonable design of the composition of the coating of the transition layer, and the reasonable design of the chemical composition of the coating of the functional layer, the present application simultaneously improves the high-temperature resistance, corrosion resistance, and wear resistance of the thermocouple metal protection sleeve for waste power generation. Specifically as follows:

[0045] First, the present application adopts the composite coating structure of the transition layer and the functional layer. The transition layer adheres to the surface of the thermocouple metal protection sleeve, mainly playing the role of enhancing the bonding force between the functional coating and the metal protection sleeve, and at the same time alleviating the problem of coating peeling caused by the difference in thermal expansion coefficient. The functional layer adheres to the surface of the transition layer and is the main functional part of the coating, responsible for withstanding various harsh conditions in the waste power generation environment. Multiple components in the functional layer can form a multi-level protection, effectively isolating the contact between the corrosive medium and the thermocouple metal protection sleeve, thereby improving the corrosion resistance of the coating.

[0046] Second, the present application reasonably designs the composition of the coating of the transition layer. The functions of the chemical components of the coating of the transition layer are as follows:

[0047] Al-Ni intermetallic compound: (1) The Al-Ni intermetallic compound is a compound formed by two metal elements, aluminum (Al) and nickel (Ni), through a specific atomic ratio and arrangement. The atoms in these compounds are connected to each other through metallic bonds, forming a stable crystal structure. When the Al-Ni intermetallic compound is part of the transition layer coating, its metallic bond can form a chemical bond with the metal atoms on the surface of the metal protection sleeve, thereby enhancing the bonding force between the coating and the metal protection sleeve. (2) The Al-Ni intermetallic compound usually has good wettability and spreading property, which means that it can uniformly cover the surface of the metal protection sleeve to form a continuous coating. Good wettability and spreading property help to increase the contact area between the coating and the metal protection sleeve, thereby further improving the bonding force.

[0048] Cermet composite materials: (1) Cermet composite materials are composite materials composed of a metal phase and a ceramic phase. In the transition layer, the metal phase serves as the matrix, while the ceramic phase (such as oxides, carbides, etc.) serves as the reinforcing phase. The ceramic phase has excellent properties such as high hardness, high wear resistance, and high corrosion resistance. When they are dispersed in the metal matrix in the form of fine particles, they can be tightly combined with the metal matrix through physical and chemical actions, forming a strong interfacial bond. (2) There are usually differences in the thermal expansion coefficients of metals and ceramics. In the transition layer, by reasonably adjusting the proportion and distribution of the metal phase and the ceramic phase, the overall thermal expansion coefficient of the transition layer can be adjusted to a certain extent. When the thermal expansion coefficient of the transition layer is close to that of the metal protective casing, the problem of coating peeling caused by thermal expansion differences can be significantly reduced.

[0049] High-expansion alloy: The addition of high-expansion alloy is mainly to adjust the thermal expansion coefficient of the coating to make it more compatible with the substrate material, thereby reducing the stress and peeling phenomenon caused by thermal expansion mismatch.

[0050] The chemical components of the coating in the transition layer have significant synergistic effects, as follows:

[0051] (1) Enhancing the bonding force: The chemical bonding and wetting and spreading properties of the Al-Ni intermetallic compound, as well as the strong bonding between the reinforcing phase and the matrix in the cermet composite material, jointly enhance the bonding force between the coating and the metal protective casing. This enhanced bonding force makes the coating not easy to peel off in a harsh working environment, thereby improving the stability and service life of the thermocouple. (2) Alleviating thermal expansion differences: By adjusting the thermal expansion coefficient of the transition layer, it can be made to match the thermal expansion coefficient of the metal protective casing, thereby effectively alleviating the problem of coating peeling caused by thermal expansion differences. This alleviating effect further improves the stability and reliability of the coating, ensuring the normal operation of the thermocouple at high temperatures and in harsh environments.

[0052] Therefore, the Al-Ni intermetallic compound and the cermet composite material in the transition layer significantly enhance the bonding force between the coating and the metal protective casing through their synergistic effects at the molecular level, and effectively alleviate the problem of coating peeling caused by thermal expansion coefficient differences. This synergistic effect provides a strong guarantee for the stable operation of the thermocouple in harsh environments such as waste power generation.

[0053] Thirdly, reasonably design the chemical composition of the coating for the functional layer. The functions of the chemical components of the coating for the functional layer are as follows:

[0054] Nickel-based self-fluxing alloy: Nickel-based self-fluxing alloy is mainly composed of nickel (Ni) and other alloying elements (such as chromium, silicon, boron, etc.). During the coating curing process, these elements are interconnected through metallic bonds to form a stable alloy structure. Nickel has good ductility and corrosion resistance, enabling the coating to maintain stability and integrity in harsh environments. Other elements in the alloy, such as chromium, can enhance the high-temperature resistance of the coating, while elements like silicon and boron help improve the hardness and wear resistance of the coating.

[0055] ZrO 2 and ZrC: ZrO 2 (zirconia) and ZrC (zirconium carbide) are both high-hardness ceramic materials with excellent wear resistance and high-temperature resistance. In the coating, the molecules of ZrO2 and ZrC are interconnected through ionic bonds or covalent bonds to form a dense ceramic network structure. This structure can effectively resist wear and scratches while maintaining the stability of the coating at high temperatures.

[0056] SiO 2 and Al 2 O 3 : SiO 2 (silicon dioxide) and Al 2 O 3 (aluminum oxide) are both common inorganic oxides with good corrosion resistance and high-temperature resistance. In the coating, the molecules of SiO 2 and Al 2 O 3 bind with surrounding metal or ceramic molecules through ionic bonds or covalent bonds to form a stable compound structure. These compound structures can resist the erosion of various corrosive media while maintaining the stability of the coating at high temperatures. At the same time, under high-temperature conditions, the molecules of SiO 2 and Al 2 O 3 are interconnected through ionic bonds or covalent bonds to form a stable mullite structure. The mullite structure is dense and has a low porosity, which can effectively resist the erosion of various corrosive media.

[0057] Y 2 O 3 coated WO 3 composite material: Y 2 O 3 (yttrium oxide) as a coating material can significantly improve the high-temperature resistance and stability of WO 3 (tungsten trioxide). In the coating, the molecules of Y 2 O 3 bind with the molecules of WO 3 through ionic bonds or covalent bonds to form a stable composite material structure. This structure can further enhance the high-temperature resistance of the coating and improve its antioxidant ability.

[0058] Inorganic nano - composite binder: The inorganic nano - composite binder consists of nano - scale inorganic particles and a binder, and has excellent bonding properties and toughness. In the coating, the inorganic nano - particles combine with surrounding metal, ceramic or oxide molecules through physical and chemical actions to form a tight bonding structure. This structure can significantly improve the overall strength and toughness of the coating, while enhancing the synergistic effect between components.

[0059] Dispersant: A dispersant is a surfactant that can reduce the surface tension between components in the paint, enabling them to be evenly dispersed in the solvent. During the coating preparation process, the dispersant molecules form a protective film by adsorbing on the surface of paint particles, preventing particle agglomeration and precipitation. This effect ensures the formation of a uniform coating structure during the curing process, thereby improving the overall performance of the coating.

[0060] The various chemical components of the paint in the functional layer jointly enhance the high - temperature resistance, corrosion resistance and wear resistance of the coating through complex interactions and synergistic mechanisms. The following is a detailed explanation of this synergistic effect:

[0061] Enhancement of high - temperature resistance. (1) Composite structure of metal and ceramic: Metal components such as nickel - based self - fluxing alloys provide good ductility and toughness, enabling the coating to maintain its integrity at high temperatures. Ceramic components such as ZrO 2 , ZrC, etc. have high melting points and can remain stable at extremely high temperatures, forming a heat - resistant framework. (2) Stabilizing effect of the oxide network: Oxide components such as SiO 2 and Al 2 O 3 can form a stable oxide network structure at high temperatures, effectively blocking the transfer of heat and improving the heat - insulation performance of the coating. The formation of mullite (formed by the reaction of SiO 2 and Al 2 O 3 ) further enhances the high - temperature resistance of the coating. (3) Strengthening effect of the inorganic nano - composite binder: The inorganic nano - composite binder tightly binds the metal and ceramic components together through a tight bonding effect, forming a stable composite structure and improving the overall high - temperature resistance of the coating.

[0062] Enhancement of corrosion resistance. (1) Protective effect of the dense structure: The components in the paint form a dense coating structure through chemical reactions and physical bonding, effectively blocking the erosion of corrosive media on the substrate. Ceramic components such as ZrO 2 , ZrC, etc. have excellent chemical stability and can resist the erosion of various corrosive media. (2) Barrier effect of the oxide layer: SiO 2 and Al 2 O 3Oxide components such as can form a dense oxide layer at high temperatures, acting as a barrier to prevent the penetration of corrosive media. The formation of mullite further enhances this barrier effect and improves the corrosion resistance of the coating. (3) Y 2 O 3 Coating WO 3 Reinforcement of the composite material: Y 2 O 3 Coating WO 3 The composite material can significantly improve the high-temperature oxidation resistance and corrosion resistance of the coating, protecting the coating from corrosion by forming a stable oxide layer.

[0063] Improvement of wear resistance. (1) Formation of hard phases: ZrO 2 , ZrC and other ceramic components have high hardness and can form hard phases in the coating to improve the wear resistance of the coating. Hard carbides, borides, etc. in the nickel-based self-fluxing alloy also enhance the wear resistance of the coating. (2) Synergistic effect between metal and ceramic: Metal components provide good toughness and ductility, which can absorb and disperse the impact force during the wear process. Ceramic components provide high hardness and wear resistance, which can resist friction and scratches during the wear process. (3) Bonding effect of inorganic nano-composite binder: The inorganic nano-composite binder firmly binds each component together through a tight bonding effect, forming a coating structure with excellent overall performance and improving the wear resistance of the coating.

[0064] Therefore, components such as nickel-based self-fluxing alloy, ZrO 2 , ZrC, etc. form a stable metal-ceramic composite structure, improving the hardness and wear resistance of the coating. At the same time, SiO 2 , Al 2 O 3 and Y 2 O 3 Coating WO 3 Composite materials and other components form a dense oxide network structure, enhancing the corrosion resistance and high-temperature resistance of the coating. In addition, the inorganic nano-composite binder tightly binds each component together through a tight bonding effect, improving the overall strength and toughness of the coating. The dispersant ensures the uniform dispersion of each component in the coating, avoiding agglomeration and precipitation phenomena, and thus improving the uniformity and stability of the coating. The components in the functional layer coating synergistically improve the high-temperature resistance, corrosion resistance and wear resistance of the coating at the molecular chemistry level, providing a strong guarantee for the stable operation of the thermocouple in harsh environments.

[0065] IV. Surface coating of the thermocouple metal protection sleeve In a high-temperature environment, the components in the coating will undergo a series of complex interactions and reactions, thereby generating coating substances with high temperature resistance and corrosion resistance. The following is a detailed description of these interactions and reactions:

[0066] Nickel-based self-fluxing alloy: (1) The nickel-based self-fluxing alloy will melt at high temperatures and undergo chemical reactions with other components. As one of the main components of the coating, it can form a stable chemical structure with other oxides and composite materials. (2) The Ni element in the nickel-based self-fluxing alloy will react with oxides (such as ZrO 2 , SiO 2 , Al 2 O 3 ) to form oxides or composite oxides of Ni, and these compounds have high stability and corrosion resistance at high temperatures.

[0067] Oxides (ZrO 2 , ZrC, SiO 2 , Al 2 O 3 ): (1) At high temperatures, these oxides will undergo a certain degree of sintering and densification to form a more stable oxide layer. These oxide layers can effectively block the erosion of corrosive media and improve the corrosion resistance of the coating. (2) ZrO 2 and ZrC have high hardness and wear resistance at high temperatures, which can further enhance the anti-wear performance of the coating. At the same time, they may also undergo chemical reactions with other components (such as nickel-based self-fluxing alloy) to form new compounds or solid solutions. SiO 2 and Al 2 O 3 can enhance the chemical stability of the coating and prevent the coating from undergoing chemical changes at high temperatures. They will also interact with other components to form a more complex chemical structure.

[0068] Y 2 O 3 coated WO 3 composite material: (1) At high temperatures, Y 2 O 3 in the Y 3 coated WO 2 O 3 composite material can act as a stabilizer to prevent WO 3 from decomposing or undergoing phase changes at high temperatures. At the same time, WO 3 has a certain catalytic effect and can promote the formation of a dense oxide protective film on the coating surface. (2) Y 2 O 3 and WO 3 may undergo chemical reactions to form new compounds or solid solutions. These compounds or solid solutions have high stability and corrosion resistance at high temperatures and can further enhance the performance of the coating.

[0069] Inorganic nano - composite binder: The inorganic nano - composite binder will melt at high temperatures and penetrate into the tiny gaps between the components, forming strong chemical bonds. This binder can ensure that the components are tightly bonded together at high temperatures, forming a complete coating structure. At the same time, the nano - scale particle size enables the binder to more effectively fill and seal the tiny defects in the coating, improving the density and corrosion resistance of the coating.

[0070] Therefore, at a high temperature of 1200 °C, complex interactions and reactions occur between the components in the transition layer and the functional layer. These reactions include processes such as interdiffusion, chemical reactions, sintering, and densification. Through these processes, stronger chemical bonds and more stable chemical structures are formed between the components. These structures endow the coating with excellent high - temperature resistance, corrosion resistance, and anti - wear properties at high temperatures.

[0071] In some alternative embodiments, the nickel - based self - fluxing alloy includes one or more of NiCo23Cr17Al12Y0.5, NiCo23Cr20Al8.5Ta4Y0.1, and CoNi32Cr21Al8Y0.5; and / or,

[0072] The high - expansion alloy includes one or more of Cu60Zn40, FeNi22Cr3, FeNi20Mn6, FeNi13Mn7, and Mn72Cr18Ni10.

[0073] The coating of the nickel - based super - high - temperature alloy is dense, has a high bonding strength, is corrosion - resistant and cavitation - resistant, can withstand a high temperature of 982 °C, and has excellent oxidation resistance. It is used as a high - temperature heat - resistant coating and as a bonding transition layer for thermal barrier coatings. It is used for heat - resistant coatings on the surfaces of thermal equipment such as metallurgical rolls, hot - dip immersion rolls, and heat treatment furnace rolls; heat - resistant coatings for aero - engine blades and gas - turbine blades, as well as bonding transition layers for thermal barrier coatings on the surfaces of high - temperature furnace tuyeres and heat shields.

[0074] In some alternative embodiments, the particle size of the nickel - based self - fluxing alloy is - 140M + 325M; - 325M.

[0075] In some alternative embodiments, the inorganic nano - composite binder includes one or more of aluminum dihydrogen phosphate, silica sol, and aluminum sol.

[0076] It should be noted that aluminum dihydrogen phosphate is an inorganic adhesive with excellent fire - resistance, flame - retardancy, and high - temperature bonding properties. It can maintain a stable bonding strength in a high - temperature environment and is not easily oxidized or decomposed.

[0077] Silica sol is a dispersion of nanoscale silica particles in water or a solvent. It has good dispersibility, permeability, and adhesiveness. The silica particles in the silica sol contain a large amount of water and hydroxyl groups, which enable it to form strong silicon-oxygen bonds when losing water and become an excellent adhesive.

[0078] Nanometer aluminum sol is a colloidal solution in which positively charged feather-shaped alumina colloidal particles are dispersed in water. It has adhesiveness, film-forming property, and heat resistance, and the solid component is almost entirely composed of alumina, so it has extremely high heat resistance.

[0079] In some alternative embodiments, the Y 2 O 3 coated WO 3 composite material has a core-shell structure, wherein, Y 2 O 3 has a mass of 1-10% of the total mass of the Y 2 O 3 coated WO 3 composite material.

[0080] Y 2 O 3 coated WO 3 composite material is a material with a special core-shell structure, wherein Y2O3 is used as the shell material and WO3 is used as the core material. This structure can improve its high-temperature oxidation resistance, corrosion resistance, and mechanical strength, etc.

[0081] In some alternative embodiments, the cermet composite material is composed of alumina-based cermet and silicon nitride-based cermet, and the mass ratio of the alumina-based cermet to the silicon nitride-based cermet is 1:(1-3).

[0082] The mass ratio of the alumina-based cermet to the silicon nitride-based cermet being 1:(1-3) can significantly enhance the bonding force between the coating and the metal protection sleeve and effectively alleviate the problem of coating peeling caused by the difference in thermal expansion coefficients. In addition, in a high-temperature environment, due to the inevitable difference in thermal expansion coefficients, thermal stress may be generated between the coating and the metal protection sleeve. The composite structure of the alumina-based cermet and the silicon nitride-based cermet can effectively disperse and alleviate these thermal stresses, thereby reducing the risk of coating peeling.

[0083] In some alternative embodiments, the thickness of the transition layer is 40-80 μm, and the thickness of the functional layer is 50-200 μm.

[0084] In some alternative embodiments, the coating satisfies the following properties: microhardness HV≥600, porosity <0.5%, and the service life of the thermocouple at 1300°C >180 d.

[0085] Figure 2 This is a flowchart of a method for preparing a coating of a corrosion-resistant thermocouple for waste power generation provided by an embodiment of the present application.

[0086] Based on a general inventive concept, the present application provides a method for preparing a coating as described in any one of the above embodiments, as Figure 2 shown, the preparation method includes:

[0087] S1. Shot peening treatment is performed on the thermocouple metal protection sleeve;

[0088] The main purpose of shot peening treatment is to pre-treat the surface of the thermocouple metal protection sleeve to enhance its surface roughness and adhesion. By shot peening, tiny uneven structures can be formed on the sleeve surface, and these structures help the subsequent coating materials to better adhere to the sleeve.

[0089] S2. The coating of the transition layer is sprayed onto the surface of the thermocouple metal protection sleeve to form a transition layer on the surface of the thermocouple metal protection sleeve;

[0090] The main function of the transition layer is to provide an intermediate layer between the thermocouple metal protection sleeve and the functional layer to alleviate problems such as differences in thermal expansion coefficients and chemical incompatibility between the two. The transition layer can also enhance the overall strength and durability of the coating system.

[0091] S3. The coating of the functional layer is coated on the surface of the transition layer, and then curing treatment is performed to form a functional layer on the surface of the transition layer.

[0092] The functional layer is the outermost layer of the coating system. It directly faces the working environment and undertakes the main protection and functional roles. The functional layer can have various properties, such as high temperature resistance, corrosion resistance, wear resistance, etc.

[0093] In some alternative embodiments, the method for preparing the coating of the functional layer includes:

[0094] S101. SiO 2 and Al 2 O 3 are subjected to ball milling treatment, and then an inorganic nano composite binder is added, and the ball milling treatment is continued to obtain a first mixture;

[0095] S102. Nickel-based self-fluxing alloy, ZrO 2 , ZrC, a dispersant and a solvent are subjected to ball milling treatment to obtain a second mixture;

[0096] S103. The first mixture, the second mixture and Y 2 O 3Coated WO 3 The composite materials are mixed to obtain the coating for the functional layer.

[0097] In the first mixture and the second mixture, a ceramic matrix composed of SiO 2 , Al 2 O 3 and an inorganic nano-composite binder, and a metal-ceramic composite system composed of a nickel-based self-fluxing alloy, ZrO 2 , ZrC, a dispersant and a solvent are respectively formed. When the first mixture, the second mixture and the Y 2 O 3 coated WO 3 composite materials are mixed, Y 2 O 3 in the molecule and WO 3 can undergo chemical bonding or physical adsorption with the molecules in the ceramic matrix and the metal-ceramic composite system, forming a tighter bond. This bond not only improves the overall strength of the coating but also endows the coating with special high-temperature resistance and corrosion resistance. Therefore, the preparation process of mixing in three steps ensures the uniform dispersion, tight combination and improvement of special properties of the raw materials at the molecular level, thus preparing a functional layer coating with excellent properties.

[0098] In some alternative embodiments, the preparation method of the Y 2 O 3 coated WO 3 composite materials includes:

[0099] S201. Dissolve Y 2 O 3 in dilute nitric acid to obtain a mixed solution;

[0100] S202. Immerse WO 3 in the mixed solution, and then perform solid-liquid separation to obtain a precursor;

[0101] S203. Calcinate the precursor at a high temperature to obtain the Y 2 O 3 coated WO 3 composite materials; the temperature of the high-temperature calcination is 900 - 1000 °C, and the time of the high-temperature calcination is 60 - 180 min.

[0102] Y 2 O 3 coated WO 3 The preparation method of the composite materials realizes the uniform coating of Y 2 O 3 on the surface of WO 3 through three steps of dissolution, immersion and high-temperature calcination. This composite material combines Y2 O 3 and WO 3 With excellent properties such as high heat resistance, corrosion resistance and good mechanical properties, it has broad application prospects.

[0103] The following will further elaborate on this application in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. The experimental methods without specific conditions noted in the following embodiments are usually determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions or the conditions recommended by the manufacturer.

[0104] Example 1

[0105] This example provides a coating for a corrosion-resistant thermocouple used in waste power generation. The coating includes:

[0106] Transition layer, which adheres to the surface of the stainless steel protection sleeve of the thermocouple. Calculated by weight, the coating material of the transition layer consists of the following chemical components: 50 parts of Al-Ni intermetallic compound, 30 parts of metal ceramic composite material, and 20 parts of high-expansion alloy;

[0107] Among them, the Al-Ni intermetallic compound is Ni 3 Al. The metal ceramic composite material is composed of alumina-based metal ceramic and silicon nitride-based metal ceramic with a mass ratio of 1:1. The model of the alumina-based metal ceramic is 96 porcelain (ceramic material with an alumina content of about 96%), the model of the silicon nitride-based metal ceramic is YB-1, and the high-expansion alloy is Cu60Zn40;

[0108] Functional layer, which adheres to the surface of the transition layer. Calculated by weight, the coating material of the functional layer consists of the following chemical components: 34 parts of nickel-based self-fluxing alloy, 5 parts of ZrO 2 5 parts of ZrC, 10 parts of SiO 2 10 parts of Al 2 O 3 4 parts of Y 2 O 3 WO-coated 3 Composite material is 6 parts, inorganic nano-composite binder is 10 parts, dispersant is 1 part and solvent is 25 parts.

[0109] Among them, the nickel-based self-fluxing alloy is NiCo23Cr17Al12Y0.5, the inorganic nano-composite binder is silica sol (Shandong Baite New Materials, model S3010, content 30%, sodium-type silica sol with a particle size of 10 - 15nm), Y 2 O 3 WO-coated 3In the composite material, the mass ratio of Y 2 O 3 is 5%, the mass ratio of WO 3 is 95%, the dispersant is sodium dodecyl sulfate, and the solvent is deionized water.

[0110] Based on the above coating, this embodiment also provides a method for preparing the coating, which specifically includes the following steps:

[0111] Step 1: Dissolve Y 2 O 3 in dilute nitric acid to obtain a mixed solution; immerse WO 3 in the mixed solution, then perform solid-liquid separation to obtain a precursor; calcine the precursor at high temperature to obtain Y 2 O 3 coated WO 3 composite material; the temperature of the high-temperature calcination is 900 °C, and the time of the high-temperature calcination is 180 min.

[0112] Step 2: Mix the Al-Ni intermetallic compound powder, the cermet composite powder, and the high-expansion alloy powder to obtain the coating for the transition layer.

[0113] Step 3: Perform ball milling on SiO 2 and Al 2 O 3 , then add an inorganic nano-composite binder and continue the ball milling to obtain a first mixture; perform ball milling on the nickel-based self-fluxing alloy, ZrO 2 , ZrC, the dispersant, and the solvent to obtain a second mixture; mix the first mixture, the second mixture, and the Y 2 O 3 coated WO 3 composite material to obtain the coating for the functional layer. The time of the ball milling is 80 min.

[0114] Step 4: Use a sandblaster to spray steel balls of a certain size and speed onto the surface of the thermocouple metal protection sleeve; use a spray gun to evenly spray the coating for the transition layer onto the surface of the thermocouple metal protection sleeve to form a transition layer on the surface of the thermocouple metal protection sleeve; apply the coating for the functional layer onto the surface of the transition layer, and then perform drying and curing to form a functional layer on the surface of the transition layer. The spraying temperature is 920 °C, the thickness of the transition layer is 40 μm, and the thickness of the functional layer is 200 μm.

[0115] Example 2

[0116] Based on the content disclosed in Example 1, this embodiment is further modified as follows:

[0117] The coating of the transition layer is composed of the following chemical components: 60 parts of Al-Ni intermetallic compound, 20 parts of metal-ceramic composite material, and 20 parts of high-expansion alloy.

[0118] Example 3

[0119] Based on the content disclosed in Example 1, the following further modifications are made in this example:

[0120] The coating of the transition layer is composed of the following chemical components: 40 parts of Al-Ni intermetallic compound, 40 parts of metal-ceramic composite material, and 20 parts of high-expansion alloy.

[0121] Example 4

[0122] Based on the content disclosed in Example 1, the following further modifications are made in this example:

[0123] The coating of the functional layer is composed of the following chemical components: 50 parts of nickel-based self-fluxing alloy, 5 parts of ZrO 2 5 parts of ZrC, 5 parts of SiO 2 5 parts of Al 2 O 3 2 parts of Y 2 O 3 WO-coated 3 5 parts of composite material, 5 parts of inorganic nano-composite binder, 1 part of dispersant, and 25 parts of solvent.

[0124] Example 5

[0125] Based on the content disclosed in Example 1, the following further modifications are made in this example:

[0126] The coating of the functional layer is composed of the following chemical components: 20 parts of nickel-based self-fluxing alloy, 9 parts of ZrO 2 6 parts of ZrC, 9 parts of SiO 2 9 parts of Al 2 O 3 8 parts of Y 2 O 3 WO-coated 3 10 parts of composite material, 10 parts of inorganic nano-composite binder, 3 parts of dispersant, and 25 parts of solvent.

[0127] Example 6

[0128] Based on the content disclosed in Example 1, the following further modifications are made in this example:

[0129] The metal-ceramic composite material is alumina-based metal-ceramic.

[0130] Example 7

[0131] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0132] The cermet composite material is a silicon nitride-based cermet.

[0133] Embodiment 8

[0134] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0135] Y 2 O 3 Coated WO 3 In the composite material, the mass ratio of Y 2 O 3 is 10%, and the mass ratio of WO 3 is 90%.

[0136] Comparative Example 1

[0137] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0138] The coating of the transition layer does not add Al-Ni intermetallic compound.

[0139] Comparative Example 2

[0140] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0141] The coating of the transition layer does not add cermet composite material.

[0142] Comparative Example 3

[0143] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0144] The coating of the transition layer does not add high-expansion alloy.

[0145] Comparative Example 4

[0146] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0147] The coating of the functional layer does not add ZrO 2 .

[0148] Comparative Example 5

[0149] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0150] The coating of the functional layer does not add ZrC.

[0151] Comparative Example 6

[0152] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0153] SiO is not added to the coating of the functional layer 2 and Al 2 O 3 .

[0154] Comparative Example 7

[0155] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0156] SiO is not added to the coating of the functional layer 2 .

[0157] Comparative Example 8

[0158] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0159] Y is not added to the coating of the functional layer 2 O 3 coated WO 3 composite material.

[0160] Comparative Example 9

[0161] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0162] The inorganic nano-composite binder is not added to the coating of the functional layer.

[0163] Comparative Example 10

[0164] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0165] 6 parts of Y 2 O 3 coated WO 3 composite material is replaced with 0.3 parts of Y alone 2 O 3 and 5.7 parts of WO 3 .

[0166] Comparative Example 11

[0167] On the basis of the content disclosed in Example 1, the following further modifications are made:

[0168] Only the functional layer is provided on the surface of the thermocouple metal protection sleeve, and the transition layer is not provided.

[0169] Comparative Example 12

[0170] On the basis of the content disclosed in Embodiment 1, the following further modifications are made:

[0171] No coating is provided on the surface of the thermocouple metal protection sleeve.

[0172] Perform performance tests on the surface coatings of the thermocouple metal protection sleeves of Embodiments 1-8 and Comparative Examples 1-12. The results are shown in Tables 1 and 2. High-temperature resistance test method: Place the thermocouple metal protection sleeve in a high-temperature furnace, heat up to 1300 °C, hold for 1 h, and cool with the furnace. Observe whether there are cracks or melting phenomena on the coating surface. The adhesion is determined according to GB / T9286-1998. Record the time when the surface coating of the thermocouple metal protection sleeve is corroded to the substrate of the protection sleeve in 5% sulfuric acid and 5% sodium hydroxide solutions respectively.

[0173] Table 1 Performance of the surface coatings of the thermocouple metal protection sleeves of Embodiments 1-8

[0174]

[0175] As can be seen from Table 1, for the surface coatings of the thermocouple metal protection sleeves of Embodiments 1-8, the microhardness HV≥600, the porosity <0.5%, the service life of the thermocouple at 1300 °C >180 d, the time for corrosion to the substrate of the protection sleeve in 5% sulfuric acid solution >3000 h, and the time for corrosion to the substrate of the protection sleeve in 5% sodium hydroxide solution >3100 h. In Embodiments 6 and 7, the metal-ceramic composite material is a single metal-ceramic material, and the service life is slightly reduced.

[0176] Table 2 Performance of the coatings on the surface of the thermocouple metal protection sleeves of Comparative Examples 1-12

[0177]

[0178] As can be seen from Table 2, in Comparative Examples 1-3, the coating of the transition layer lacks important components, resulting in a decrease in the bonding strength between the functional coating and the thermocouple metal protection sleeve and a decrease in the corrosion resistance of the coating. Among them, Comparative Example 3 shows the largest decrease, which is due to the lack of high-expansion alloy, resulting in a much lower thermal expansion coefficient of the transition layer than that of the thermocouple metal protection sleeve and poor bonding strength. In Comparative Examples 4-10, the coating of the functional layer lacks important components, resulting in a decrease in the generation amount of the coating material with high temperature resistance and corrosion resistance and a decrease in corrosion resistance. Comparative Example 11 lacks a transition layer, resulting in poor bonding strength between the functional coating and the thermocouple metal protection sleeve, easy shedding of the coating, and a decrease in corrosion resistance.

[0179] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the description of the said range has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0180] In the description of the specification of the present application, terms such as "including" and "comprising" mean "including but not limited to". In this text, "and / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may indicate: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B may be singular or plural. In this text, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one of the following (items)" or similar expressions refer to any combination of these items, including any combination of single item (s) or plural items (s). For example, "at least one of (item) a, b, or c", or, "at least one of (item) a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0181] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A corrosion-resistant thermocouple coating for waste-to-energy, characterized in that: The coating comprises: A transition layer, the transition layer is attached to the surface of the thermocouple metal protection sleeve, and the coating of the transition layer is composed of the following chemical components by weight: 40 to 60 parts of Al-Ni intermetallic compound, 20 to 40 parts of metal ceramic composite material, and 10 to 20 parts of high expansion alloy; and A functional layer, the functional layer is attached to the surface of the transition layer, and the coating of the functional layer is composed of the following chemical components by weight: 20 to 50 parts of nickel-based self-fluxing alloy, 5 to 10 parts of ZrO2, 2 to 7 parts of ZrC, 5 to 10 parts of SiO2, 2 to 8 parts of Al2O3, 5 to 10 parts of Y2O3-coated WO3 composite material, 5 to 10 parts of inorganic nanocomposite binder, 1 to 3 parts of dispersant and 20 to 50 parts of solvent; The metal-ceramic composite material is composed of alumina-based metal-ceramic and silicon nitride-based metal-ceramic, and the mass ratio of the alumina-based metal-ceramic to the silicon nitride-based metal-ceramic is 1:(1-3).

2. The coating according to claim 1, characterized in that The nickel-based self-fluxing alloy includes one or more of NiCo23Cr17Al12Y0.5, NiCo23Cr20Al8.5Ta4Y0.1 and CoNi32Cr21Al8Y0.5; and / or, The high expansion alloy includes one or more of Cu60Zn40, FeNi22Cr3, FeNi20Mn6, FeNi13Mn7 and Mn72Cr18Ni10.

3. The coating according to claim 1, characterized in that The inorganic nanocomposite binder includes one or more of aluminum dihydrogen phosphate, silica sol and aluminum sol.

4. The coating according to claim 1, characterized in that The Y2O3-coated WO3 composite material is a core-shell structure, wherein the mass of Y2O3 is 1-10% of the total mass of the Y2O3-coated WO3 composite material.

5. The coating according to claim 1, characterized in that The thickness of the transition layer is 40-80 μm, and the thickness of the functional layer is 50-200 μm.

6. The coating according to claim 1, characterized in that The coating meets the following properties: microhardness HV≥600, porosity<0.5%, and service life of the thermocouple at 1300°C>180d.

7. A method for preparing a coating according to any one of claims 1 to 6, characterized in that: The preparation method comprises: Shot peening of the thermocouple metal protection sleeve; Spraying a transition layer coating onto the surface of the thermocouple metal protection sleeve to form a transition layer on the surface of the thermocouple metal protection sleeve; The coating of the functional layer is applied to the surface of the transition layer, and then a curing treatment is performed to form the functional layer on the surface of the transition layer.

8. The method according to claim 7, characterized in that The preparation method of the coating of the functional layer comprises: Ball milling SiO2 and Al2O3, adding an inorganic nanocomposite binder, and continuing the ball milling to obtain a first mixture; Ball milling the nickel-based self-fluxing alloy, ZrO2, ZrC, a dispersant and a solvent to obtain a second mixture; The first mixture, the second mixture and the Y2O3-coated WO3 composite material are mixed to obtain the coating of the functional layer.

9. The method according to claim 8, characterized in that The preparation method of the Y2O3-coated WO3 composite material comprises: Dissolve Y2O3 in dilute nitric acid to obtain a mixed solution; Impregnating WO3 in the mixed solution, and then performing solid-liquid separation to obtain a precursor; The precursor is subjected to high temperature calcination to obtain a Y2O3-coated WO3 composite material; the temperature of the high temperature calcination is 900-1000°C, and the time of the high temperature calcination is 60-180 minutes.

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