Aluminized protective coating and its preparation method and application

Abstract

The present invention discloses an aluminized protective coating, its preparation method, and application. The preparation method comprises the following steps: Step 1, spraying an inorganic fiber coating on the surface of a substrate and drying it to form an inorganic fiber layer on the substrate surface; the inorganic fiber coating comprises inorganic fibers, an organic binder, and a dispersant; Step 2, aluminizing the substrate treated in Step 1 with the aluminizing agent to form an aluminized protective coating on the inorganic fiber layer. The present invention uses an organic binder to interconnect the inorganic fiber filaments. After drying, an inorganic fiber layer with a specific pore size is prepared on the substrate surface. This inorganic fiber layer can effectively inhibit the agglomeration of molten aluminum atoms during the subsequent aluminizing process, thereby ensuring that the resulting aluminized coating has high flatness.

Description

Technical Field

[0001] The invention relates to a preparation method of an aluminized protective coating, the aluminized protective coating obtained by the preparation method, and application of the aluminized protective coating in a steam cracking furnace tube. Background Art

[0002] Steam cracking furnace tubes, a core unit in the ethylene production process, determine the operating efficiency and energy consumption of the steam cracking furnace. Generally, steam cracking furnace tubes are made of high-temperature resistant chromium-nickel alloy steel. However, the nickel in this alloy migrates during use, accumulating on the surface of the steam cracking furnace tubes and acting as catalytic active centers, accelerating coke formation. To address this issue, a common approach is to utilize solid powder embedding co-infiltration technology, which infiltrates aluminum into the alloy substrate to improve the alloy's oxidation resistance and thermal corrosion resistance. Solid powder embedding co-infiltration technology is a chemical heat treatment process that involves placing the substrate in an infiltrant. The infiltrant is then heated to thermally decompose and produce active atoms. These active atoms adsorb on the substrate surface and diffuse into the interior of the substrate, forming a more stable new alloy phase with the Cr and Ni elements in the alloy material, thereby improving the overall mechanical properties of the alloy substrate. Furthermore, the resulting alloy phase can inhibit the migration of Ni atoms in the alloy substrate. At present, infiltrating aluminum into the alloy substrate through solid powder embedding co-infiltration technology is considered to be one of the most effective means to improve the oxidation resistance and mechanical properties of the alloy. Aluminum infiltration technology has been widely used in the chemical industry.

[0003] After the workpiece in CN201010277865.4 is treated with aluminizing, a metal-rich layer or compound layer is formed on the surface of the material, which changes the surface properties of the workpiece and significantly improves its resistance to high-temperature oxidation and carburization. Since a stable inert aluminum oxide layer is generated on the surface of the workpiece after aluminizing, CN106637071A discloses a method for preparing a composite coating by combining multi-stage embedded aluminizing with micro-arc oxidation. This method first uses a multi-stage embedded aluminizing technology to obtain a continuous and smooth NbAl3 aluminizing layer on the substrate. Then, the micro-arc oxidation electrolyte is adjusted by adding a film-forming agent sodium fluoride, a modifier sodium tungstate, a stabilizer disodium ethylenediaminetetraacetic acid, and a rare earth salt yttrium nitrate to prepare a uniform and regular porous Al2O3 ceramic film on the NbAl3 aluminizing layer, thereby obtaining an Al2O3 / NbAl3 composite coating. Although this composite coating has the characteristics of good bonding, uniform coating, and excellent resistance to high-temperature thermal corrosion, the coating preparation requires many control conditions, including embedded aluminizing time, temperature, micro-arc oxidation electrolyte, electrical parameters, etc., and the prepared composite coating has low flatness.

[0004] CN109868447A discloses a method for reducing the surface roughness of an aluminized layer. This method involves pre-preparing a first aluminized layer on the surface of a substrate at a high co-infiltration temperature. After polishing the first aluminized layer, a second aluminized layer is prepared at a lower co-infiltration temperature. The surface roughness of the resulting double aluminized layer is less than that of the aluminized layer prepared using existing aluminizing technology. Although this method can effectively reduce the surface roughness of the aluminized coating, the process is relatively complex and the agglomeration of aluminum atoms during the aluminizing process cannot be controlled.

[0005] CN103589992A discloses a method for preparing an aluminum-silicon infiltrated layer on the surface of a turbine blade by using chemical vapor deposition technology. The aluminum-silicon infiltrated coating used in this method is composed of an infiltrant and a binder. The infiltrant is pure aluminum powder and metallic silicon powder, and the binder is acetone, acetylacetone and nitrocellulose. The aluminum-silicon infiltrated coating prepared by this method can meet the needs of aircraft engine development. The overall mechanical properties of the coating are excellent and the bonding with the substrate is relatively strong. The main function of the nitrocellulose organic binder used in this technology is to play a cross-linking function, so that the prepared coating has a denser structural property, and it cannot inhibit the agglomeration of aluminum atoms during the aluminum infiltration process.

[0006] Therefore, this field still needs to further study how to suppress the agglomeration of aluminum atoms in solid powder embedding co-infiltration technology. Summary of the Invention

[0007] The main purpose of the present invention is to provide an aluminized protective coating and its preparation method and application, so as to overcome the defects of the existing aluminizing process, in which the agglomeration between molten aluminum atoms is uncontrolled, resulting in the aluminum atoms agglomerating with each other due to high-temperature thermal diffusion during the aluminizing process, resulting in the prepared aluminized layer having low flatness, which in turn makes the aluminized layer more susceptible to dirt adhesion, greatly reducing the properties and gain effect of the aluminized layer.

[0008] In order to achieve the above object, the present invention provides a method for preparing an aluminized protective coating, comprising the following steps:

[0009] Step 1: spraying an inorganic fiber coating on the surface of a substrate and drying the coating to form an inorganic fiber layer on the surface of the substrate; the inorganic fiber coating comprises inorganic fibers, an organic binder, and a dispersant;

[0010] Step 2: aluminizing the substrate treated in step 1 with an aluminizing agent to form an aluminized protective coating on the inorganic fiber layer.

[0011] In the method for preparing the aluminized protective coating of the present invention, the surface of the substrate is purified before the inorganic fiber coating is sprayed on the substrate.

[0012] In the method for preparing the aluminized protective coating of the present invention, the inorganic fiber layer has a thickness of 10-100 μm and a pore size of 0.04-0.1 μm.

[0013] The preparation method of the aluminized protective coating described in the present invention, wherein the inorganic fiber includes at least one of aluminum silicate fiber, asbestos fiber, quartz fiber, and mullite fiber; the organic binder is organic cellulose, and the dispersant is an organic solvent.

[0014] The preparation method of the aluminized protective coating described in the present invention, wherein the inorganic fiber is composed of inorganic fiber filaments, and the length of the inorganic fiber filaments is 10 to 40 μm; the organic cellulose includes at least one of carboxymethyl cellulose, ethyl cellulose and polyvinyl alcohol cellulose; and the dispersant is at least one of acetone, ethanol, tetrahydrofuran and toluene.

[0015] The preparation method of the aluminized protective coating described in the present invention, wherein, based on the total mass of the inorganic fiber coating, the content of the inorganic fiber is 70-80%, the content of the organic linking agent is 2-5%, and the content of the dispersant is 15-28%.

[0016] The preparation method of the aluminized protective coating described in the present invention, wherein, based on the total mass of the aluminizing agent, the aluminizing agent includes 15-30% aluminum powder, 1-1.5% ammonium chloride, 0.3-1% sodium fluoride, and 67.5-83.7% alumina powder.

[0017] The method for preparing the aluminized protective coating of the present invention comprises the following steps: placing the substrate treated in step 1 and the aluminizing agent into an aluminizing furnace for aluminizing treatment; the aluminizing treatment temperature is 900-1100° C.; and the aluminizing treatment time is 8-12 hours.

[0018] In the method for preparing the aluminized protective coating of the present invention, the particle size D90 of the aluminum powder is 50 to 100 nm, and the particle size D90 of the aluminum oxide powder is 2 to 10 μm.

[0019] In order to achieve the above object, the present invention also provides an aluminized protective coating obtained by the above preparation method.

[0020] In order to achieve the above-mentioned object, the present invention further provides a steam cracking furnace, wherein the furnace tubes of the steam cracking furnace are coated with the above-mentioned aluminized protective coating.

[0021] In order to achieve the above object, the present invention provides a boiler coated with the above-mentioned aluminized protective coating.

[0022] Beneficial effects of the present invention:

[0023] The present invention uses an organic binder to connect the inorganic fiber filaments to each other. After drying, an inorganic fiber layer with a specific pore size is prepared on the surface of the substrate. The inorganic fiber layer can effectively inhibit the agglomeration of molten aluminum atoms in the subsequent aluminizing process, thereby making the obtained aluminized coating have high flatness.

[0024] The high-flatness aluminized coating of the present invention can be applied to steam cracking furnace tubes. The high flatness of the coating can effectively prevent the adhesion of carbon deposit precursors, significantly improve the operating cycle of the steam cracking furnace, and extend the service life of the furnace tubes. The surface roughness of the high-flatness aluminized protective coating prepared by the method of the present invention can reach a minimum of 0.8 μm, which is much smaller than the aluminized coating obtained by the prior art (surface roughness Ra = 3 μm). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of the high-flatness aluminized coating of Example 1 of the present invention.

[0026] Figure 2 This is a scanning electron microscope image of the aluminized coating of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The following is a detailed description of the embodiments of the present invention. These embodiments are implemented based on the technical solutions of the present invention, and detailed implementation methods and processes are given. However, the scope of protection of the present invention is not limited to the following embodiments. The experimental methods for which specific conditions are not specified in the following embodiments are generally based on conventional conditions.

[0028] The present invention provides a method for preparing an aluminized protective coating, comprising the following steps:

[0029] Step 1: spraying an inorganic fiber coating on the surface of a substrate and drying the coating to form an inorganic fiber layer on the surface of the substrate; the inorganic fiber coating comprises inorganic fibers, an organic binder, and a dispersant;

[0030] Step 2: aluminizing the substrate treated in step 1 with an aluminizing agent to form an aluminized protective coating on the inorganic fiber layer.

[0031] The present invention uses an organic binder to connect the inorganic fiber filaments to each other. After drying, an inorganic fiber layer with a specific pore size is prepared on the surface of the substrate. The inorganic fiber layer can effectively inhibit the agglomeration of molten aluminum atoms in the subsequent aluminizing process, thereby making the obtained aluminized coating have high flatness.

[0032] The present invention does not impose any particular limitation on the material of the substrate. For example, the tube of a steam cracking furnace tube may be CrNi alloy, more specifically CrNi alloy. 35 Ni 45In one embodiment, the surface of the alloy substrate is cleaned before the inorganic fiber coating is sprayed to remove oil, impurities, etc. on the substrate surface. The present invention does not particularly limit the cleaning method; conventional cleaning methods in the art can be used.

[0033] In one embodiment, the inorganic fiber of the present invention includes at least one of aluminum silicate fiber, asbestos fiber, quartz fiber, and mullite fiber, and the length of the inorganic fiber filament is 10 to 40 μm; the organic binder is organic cellulose, polyvinyl alcohol, etc., and the organic cellulose includes, for example, at least one of carboxymethyl cellulose, ethyl cellulose, and polyvinyl alcohol cellulose; the dispersant is an organic solvent, for example, at least one of acetone, ethanol, tetrahydrofuran, and toluene.

[0034] In another embodiment, the present invention takes the total mass of the inorganic fiber coating as a benchmark, and in the inorganic fiber coating, the content of the inorganic fiber is 70-80%, the content of the organic linking agent is 2-5%, and the content of the dispersant is 15-28%.

[0035] The present invention does not particularly limit the method of spraying the inorganic fiber coating onto the substrate, and conventional spraying methods in the art may be used.

[0036] In the present invention, after the inorganic fiber coating is sprayed on the surface of the substrate, it is dried at a temperature of 60-90° C., preferably 60-80° C. After drying, an inorganic fiber layer is formed on the surface of the substrate. In one embodiment, the inorganic fiber layer has a thickness of 10-100 μm, preferably 20-80 μm, and a pore size of 0.04-0.1 μm.

[0037] Step 2 is to subject the substrate treated in step 1 to aluminizing treatment with an aluminizing agent to form an aluminized protective coating on the inorganic fiber layer. The thickness of the aluminized protective coating is 10-110 μm, preferably 50-110 μm.

[0038] In one embodiment, the present invention comprises, based on the total mass of the aluminizing agent, 15-30% aluminum powder, 1-1.5% ammonium chloride, 0.3-1% sodium fluoride, and 67.5-83.7% alumina powder. In another embodiment, the aluminizing agent comprises 15-25% aluminum powder, 1-1.5% ammonium chloride, 0.4-0.8% sodium fluoride, and 67.5-83.7% alumina powder. Ammonium chloride serves as an aluminizing activator, and sodium fluoride serves as an aluminizing stabilizer.

[0039] The raw materials are mixed in proportion and ground thoroughly to obtain the aluminizing agent. The substrate treated in step 1 and the aluminizing agent are placed in a high-temperature solid-phase aluminizing furnace and kept at 900-1100°C for 8-12 hours for high-temperature solid-phase aluminizing. In one embodiment, the solid-phase aluminizing temperature is 1000-1050°C for 8-10 hours.

[0040] In one embodiment, the aluminum powder of the aluminizing agent is nanometer-sized, with a particle size D90 of 50 to 100 nm, and the aluminum oxide powder is micrometer-sized, with a particle size D90 of 2 to 10 μm.

[0041] Therefore, the aluminized protective coating obtained by the method of the present invention has good flatness, and the surface roughness of the aluminized protective coating can reach a minimum of 0.8 μm, which is much smaller than the aluminized coating obtained by the prior art (surface roughness Ra=3 μm).

[0042] The preparation method of the aluminized protective coating of the present invention and the obtained aluminized protective coating can be used as a protective coating in the fields of steam cracking furnace tubes and high-temperature boilers.

[0043] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0044] Example 1

[0045] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. firstly 35 Ni 45 1. The surface of the alloy substrate is purified to remove oil stains on the surface of the substrate; 2. The inorganic fiber layer is sprayed on the surface of the substrate. The selected spraying method is the vapor phase spraying method. The raw materials in the inorganic fiber coating are divided into 73% asbestos fiber, 4% organic coupling agent ethyl cellulose, and 23% acetone by weight percentage. After spraying, it is dried at a drying temperature of 60°C. The thickness of the fiber layer obtained by drying is 60μm, and the pore size of the inorganic fiber layer is 0.08μm; 3. The aluminizing agent is prepared according to the weight percentage of the raw materials. The weight of each raw material is 100μm. The percentages are: aluminum powder 20%, ammonium chloride 1.5%, sodium fluoride 0.8%, and alumina powder 77.7%, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. The raw materials are fully ground and mixed to obtain an aluminizing agent; 4. The substrate coated with the inorganic fiber layer and the prepared aluminizing agent are placed in an aluminizing box and kept at 1040°C for 9 hours for high-temperature solid-phase aluminizing, and finally a high-flatness protective aluminized coating is obtained. The aluminized coating has a thickness of 63μm. The surface morphology of the coating is shown in the attached figure. Figure 1 shown.

[0046] Example 2

[0047] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. firstly 35 Ni 451. The surface of the alloy substrate is purified to remove oil stains on the substrate surface; 2. The surface of the substrate is sprayed with inorganic fibers using a vapor phase spraying method. The raw materials in the inorganic fiber coating are composed of 70% aluminum silicate fiber, 3.5% organic binder carboxymethyl cellulose, and 26.5% acetone by weight. After spraying, the coating is dried at 60°C. The resulting fiber layer has a thickness of 60 μm and a pore size of 0.07 μm. 3. Aluminized aluminum is prepared according to the weight percentage of the raw materials. The weight percentages of the raw materials are as follows: 20% aluminum powder, 1.5% ammonium chloride, 0.7% sodium fluoride, and 77.8% alumina powder, wherein the particle size D90 of the aluminum powder is 70 nm, and the particle size D90 of the alumina powder is 2 μm. The raw materials are fully ground and mixed uniformly to obtain the aluminizing agent; 4. The substrate coated with the inorganic fiber layer and the prepared aluminizing agent are placed in a aluminizing box, and the aluminizing is carried out at 1040°C for 9 hours for high-temperature solid-phase aluminizing, and finally a high-flatness protective aluminized coating is obtained, and the thickness of the aluminized coating is 62 μm.

[0048] Example 3

[0049] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. firstly 35 Ni 45 1. The surface of the alloy substrate is purified to remove oil stains on the substrate surface; 2. The surface of the substrate is sprayed with inorganic fibers. The selected spraying method is vapor phase spraying. The raw materials in the inorganic fiber coating are divided into 78% mullite fiber, 2% organic linker polyvinyl alcohol, and 20% acetone by weight percentage. After spraying, it is dried at a drying temperature of 60°C. The fiber layer obtained by drying has a thickness of 60μm and a pore size of 0.08μm. 3. Aluminizing agent is prepared according to the weight percentage of the raw materials. The weight percentages of the raw materials are: 20% aluminum powder, 1.5% ammonium chloride, 0.8% sodium fluoride, and 77.7% alumina powder, wherein the aluminum powder particle size D90 is 70nm, and the alumina powder particle size D90 is 5μm. The raw materials are fully ground and mixed evenly to obtain an aluminizing agent; 4. The substrate coated with the inorganic fiber layer and the prepared aluminizing agent are placed in an aluminizing box, and kept warm at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally a high-flatness protective aluminizing coating is obtained, and the thickness of the aluminizing coating is 65μm.

[0050] Example 4

[0051] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. firstly 35 Ni 451. The alloy substrate surface is cleaned to remove oil stains from the substrate surface; 2. The substrate surface is sprayed with inorganic fibers using a vapor phase spraying method. The inorganic fiber coating comprises 70% aluminum silicate fiber, 3.5% carboxymethyl cellulose as an organic binder, and 26.5% acetone by weight. After spraying, the coating is dried at 60°C. The resulting fiber layer has a thickness of 80 μm and a pore size of 0.1 μm. 3. An aluminizing agent is prepared according to the weight percentage of the raw materials. The weight percentages of the raw materials are: 15% aluminum powder, 1% ammonium chloride, 0.4% sodium fluoride, and 83.6% alumina powder, wherein the aluminum powder particle size D90 is 100nm, and the alumina powder particle size D90 is 10μm. The raw materials are fully ground and mixed evenly to obtain an aluminizing agent; 4. The substrate coated with the inorganic fiber layer and the prepared aluminizing agent are placed in an aluminizing box, and kept warm at 1050°C for 10 hours for high-temperature solid-phase aluminizing, and finally a high-flatness protective aluminized coating is obtained, and the thickness of the aluminized coating is 87μm.

[0052] Example 5

[0053] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. firstly 35 Ni 45 1. The surface of the alloy substrate is purified to remove oil stains on the substrate surface; 2. The surface of the substrate is sprayed with inorganic fibers using a vapor phase spraying method. The raw materials in the inorganic fiber coating are composed of 70% aluminum silicate fiber, 3.5% organic binder carboxymethyl cellulose, and 26.5% acetone by weight. After spraying, the coating is dried at 80°C. The resulting fiber layer has a thickness of 80 μm and a pore size of 0.1 μm. 3. Aluminized coating is prepared according to the weight percentage of the raw materials. agent, the weight percentage of each raw material is: aluminum powder 25%, ammonium chloride 1.5%, sodium fluoride 0.8%, aluminum oxide 72.7%, wherein the aluminum powder particle size D90 is 60nm, and the aluminum oxide powder particle size D90 is 5μm. The raw materials are fully ground and mixed uniformly to obtain the aluminizing agent; 4. The substrate coated with the inorganic fiber layer and the prepared aluminizing agent are placed in a aluminizing box, and kept warm at 1000℃ for 8h for high-temperature solid-phase aluminizing, and finally a high-flatness protective aluminized coating is obtained, and the thickness of the aluminized coating is 84μm.

[0054] Example 6

[0055] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of a Cr35Ni45 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, wherein the selected spraying method is a vapor phase spraying method, and the raw materials in the inorganic fiber coating are composed of 73% asbestos fiber, 4% organic coupling agent ethyl cellulose, and 23% acetone in weight percentage. After spraying, the coating is dried at a drying temperature of 60°C. The fiber layer obtained after drying has a thickness of 60 μm and a pore size of 0.08 μm. m; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, wherein the weight percentages of the raw materials are: 30% aluminum powder, 1.5% ammonium chloride, 1.0% sodium fluoride, and 67.5% alumina powder, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind the raw materials thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, and keep it at 1040°C for 9 hours for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 68μm.

[0056] Example 7

[0057] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of a Cr35Ni45 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, wherein the selected spraying method is a vapor phase spraying method, and the raw materials in the inorganic fiber coating are composed of 73% asbestos fiber, 4% organic coupling agent ethyl cellulose, and 23% acetone in weight percentage. After spraying, the coating is dried at a drying temperature of 60°C. The fiber layer obtained after drying has a thickness of 60 μm and a pore size of 0.08 μm. m; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, wherein the weight percentages of the raw materials are: 15% aluminum powder, 1.0% ammonium chloride, 1.0% sodium fluoride, and 83.0% alumina powder, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind the raw materials thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, and keep it at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 61μm.

[0058] Example 8

[0059] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of a Cr20Ni35 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, wherein the selected spraying method is a vapor phase spraying method, and the raw materials in the inorganic fiber coating are composed of 73% asbestos fiber, 4% organic coupling agent ethyl cellulose, and 23% acetone in weight percentage. After spraying, the coating is dried at a drying temperature of 60°C. The fiber layer obtained after drying has a thickness of 60 μm and a pore size of 0.08 μm. m; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, wherein the weight percentages of the raw materials are: 20% aluminum powder, 1.5% ammonium chloride, 0.8% sodium fluoride, and 77.7% alumina powder, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind the raw materials thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, and keep it at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 63μm.

[0060] Example 9

[0061] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of an Incoloy 800 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, using a vapor phase spraying method; the inorganic fiber coating comprises, by weight, 73% asbestos fiber, 4% ethyl cellulose as an organic coupling agent, and 23% acetone; drying the coating at 60°C; and drying the resulting fiber layer to a thickness of 60 μm and a pore size of 0.08 μm. μm; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, the weight percentage of each raw material is: 20% aluminum powder, 1.5% ammonium chloride, 0.8% sodium fluoride, 77.7% alumina powder, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind each raw material thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, keep it warm at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 63μm.

[0062] Example 10

[0063] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of a Cr20Ni35 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, wherein the selected spraying method is a vapor phase spraying method, and the raw materials in the inorganic fiber coating are composed of 73% asbestos fiber, 4% organic coupling agent ethyl cellulose, and 23% acetone in weight percentage. After spraying, the coating is dried at a drying temperature of 60°C. The fiber layer obtained after drying has a thickness of 60 μm and a pore size of 0.08 μm. m; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, wherein the weight percentage of each raw material is: 30% aluminum powder, 1.5% ammonium chloride, 1.0% sodium fluoride, and 67.5% alumina powder, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind each raw material thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, and keep it at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 66μm.

[0064] Example 11

[0065] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of a Cr20Ni35 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, wherein the selected spraying method is a vapor phase spraying method, and the raw materials in the inorganic fiber coating are composed of 73% asbestos fiber, 4% organic coupling agent ethyl cellulose, and 23% acetone in weight percentage. After spraying, the coating is dried at a drying temperature of 60°C. The fiber layer obtained after drying has a thickness of 60 μm and a pore size of 0.08 μm. m; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, wherein the weight percentage of each raw material is: 15% aluminum powder, 1.0% ammonium chloride, 1.0% sodium fluoride, and 83.0% alumina powder, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind each raw material thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, and keep it at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 62μm.

[0066] Example 12

[0067] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of an Incoloy 800 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, using a vapor phase spraying method; the inorganic fiber coating comprises, by weight, 73% asbestos fiber, 4% ethyl cellulose as an organic coupling agent, and 23% acetone; drying the coating at 60°C; and drying the resulting fiber layer to a thickness of 60 μm and a pore size of 0.08 μm. μm; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, the weight percentage of each raw material is: 30% aluminum powder, 1.5% ammonium chloride, 1.0% sodium fluoride, 67.5% alumina powder, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind each raw material thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, keep it warm at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 67μm.

[0068] Example 13

[0069] A method for preparing a high-flatness protective aluminized coating comprises the following steps: 1. first, purifying the surface of an Incoloy 800 alloy substrate to remove oil stains from the substrate surface; 2. spraying the substrate surface with inorganic fibers, using a vapor phase spraying method; the inorganic fiber coating comprises, by weight, 73% asbestos fiber, 4% ethyl cellulose as an organic coupling agent, and 23% acetone; drying the coating at 60°C; and drying the resulting fiber layer to a thickness of 60 μm and a pore size of 0.08 μm. μm; 3. Prepare an aluminizing agent according to the weight percentage of the raw materials, the weight percentage of each raw material is: aluminum powder 15%, ammonium chloride 1.0%, sodium fluoride 1.0%, alumina powder 83.0%, wherein the aluminum powder particle size D90 is 50nm, and the alumina powder particle size D90 is 2μm. Grind each raw material thoroughly and mix them evenly to obtain the aluminizing agent; 4. Place the substrate coated with the inorganic fiber layer and the prepared aluminizing agent in an aluminizing box, keep it warm at 1040°C for 9h for high-temperature solid-phase aluminizing, and finally obtain a high-flatness protective aluminized coating with a thickness of 62μm.

[0070] Comparative Example 1

[0071] According to step 1 of Example 1, Cr 35 Ni 45 The surface of the alloy substrate is cleaned and the aluminizing agent is prepared according to the weight percentage of the aluminizing agent raw materials in step 3 of Example 1; 4. The Cr 35 Ni 45The alloy substrate and the prepared aluminizing agent were placed in a permeation box and kept at 1040℃ for 9 hours for high temperature solid phase aluminizing. The surface morphology of the aluminized coating was shown in the attached figure. Figure 2 shown.

[0072] Comparative Example 2

[0073] According to step 1 of Example 1, Cr 20 Ni 35 The surface of the alloy substrate is purified, and an aluminizing agent is prepared according to the weight percentage of the aluminizing agent raw materials in step 3 of Example 1; the Cr35Ni45 alloy substrate after only the surface purification treatment and the prepared aluminizing agent are placed in a permeation box, and kept at 1040°C for 9 hours for high-temperature solid-phase aluminizing to obtain an aluminized coating.

[0074] Comparative Example 3

[0075] The surface of an Incoloy 800 alloy substrate was cleaned according to step 1 of Example 1. An aluminizing agent was prepared according to the weight percentages of the aluminizing agent raw materials in step 3 of Example 1. The Cr35Ni45 alloy substrate, which had only undergone surface cleaning, and the prepared aluminizing agent were placed in an aluminizing chamber and subjected to high-temperature solid-phase aluminizing at 1040°C for 9 hours to produce an aluminized coating. The surface roughness of the high-flatness protective aluminized coating obtained in the above specific example and the aluminized coating of the comparative example were analyzed using a surface roughness tester AR-132A, which complies with national standards GB / T 6062 as well as ISO, DIN, ANSI, and JIS. The data obtained are shown in Table 1.

[0076] Table 1

[0077]

[0078]

[0079] From Table 1, Figure 1 and 2 As shown, the aluminized coating obtained by the method of the present invention has low surface roughness and high coating flatness.

[0080] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an aluminized protective coating, characterized in that: The steps include: Step 1: spraying an inorganic fiber coating on the surface of a substrate and drying the coating to form an inorganic fiber layer on the surface of the substrate; the inorganic fiber coating comprises inorganic fibers, an organic binder, and a dispersant; Step 2, aluminizing the substrate treated in step 1 with an aluminizing agent to form an aluminized protective coating on the inorganic fiber layer; Wherein, the organic linker is organic cellulose or polyvinyl alcohol; the organic cellulose includes at least one of carboxymethyl cellulose, ethyl cellulose and polyvinyl alcohol cellulose; The inorganic fiber includes at least one of aluminum silicate fiber, asbestos fiber, quartz fiber, and mullite fiber.

2. The method for preparing an aluminized protective coating according to claim 1, wherein: Before the inorganic fiber coating is sprayed on the substrate, the surface of the substrate is purified.

3. The method for preparing an aluminized protective coating according to claim 1, wherein: The inorganic fiber layer has a thickness of 10-100 μm and a pore size of 0.04-0.1 μm.

4. The method for preparing an aluminized protective coating according to claim 1, wherein: The dispersant is an organic solvent.

5. The method for preparing an aluminized protective coating according to claim 4, characterized in that: The inorganic fibers are composed of inorganic fiber filaments, and the length of the inorganic fiber filaments is 10-40 μm; the dispersant is at least one of acetone, ethanol, tetrahydrofuran, and toluene.

6. The method for preparing an aluminized protective coating according to claim 4, wherein: Based on the total mass of the inorganic fiber coating, the content of the inorganic fiber is 70-80%, the content of the organic linking agent is 2-5%, and the content of the dispersant is 15-28%.

7. The method for preparing an aluminized protective coating according to claim 1, wherein: Based on the total mass of the aluminizing agent, the aluminizing agent includes 15-30% aluminum powder, 1-1.5% ammonium chloride, 0.3-1% sodium fluoride, and 67.5-83.7% aluminum oxide powder.

8. The method for preparing an aluminized protective coating according to claim 1, wherein: The substrate treated in step 1 and the aluminizing agent are placed in an aluminizing furnace for aluminizing treatment. The aluminizing treatment temperature is 900-1100° C. and the aluminizing treatment time is 8-12 hours.

9. The method for preparing an aluminized protective coating according to claim 7, wherein: The particle size D90 of the aluminum powder is 50-100 nm, and the particle size D90 of the aluminum oxide powder is 2-10 μm.

10. An aluminized protective coating obtained by the preparation method according to any one of claims 1 to 9.

11. A steam cracking furnace, characterized in that: The furnace tubes of the steam cracking furnace are coated with the aluminized protective coating according to claim 10.

12. A boiler, characterized in that: The boiler is coated with the aluminized protective coating according to claim 10.

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