Preparation method of high-temperature-resistant anticorrosive aluminum-permeable coating and prepared coating

Abstract

The application discloses a preparation method of a high-temperature-resistant anticorrosive aluminum infiltration coating and the prepared coating and relates to the technical field of coating preparation.The application comprises the following steps: S1, infiltration layer preparation, S2, shielding layer preparation and S3, coating heat treatment in an air atmosphere.The high-temperature-resistant anticorrosive aluminum infiltration coating is prepared in an air atmosphere, has excellent oxidation resistance and corrosion resistance, can resist 1000 DEG C thermal oxidation for 100 hours, can resist neutral salt spray corrosion for 3000 hours, and does not bubble, crack or fall off.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating preparation, and particularly relates to a preparation method of a high-temperature-resistant anti-corrosion aluminum infiltration coating and the prepared coating. BACKGROUND

[0002] Gas turbines and aero-engines are the core power units of ships and aircrafts, and must withstand long-time high-temperature oxidation and complex corrosion environments coupled with salt spray corrosion, molten salt corrosion and gas hot corrosion during service in marine environments. In order to ensure the long-term reliable service of the equipment, high-pressure compressor blades, casings and other adjacent components with a working temperature of 500-1000 DEG C usually adopt aluminum infiltration coatings to achieve high-temperature corrosion resistance. Traditional aluminum infiltration coatings are prepared by powder embedding method, hot-dip aluminum infiltration method, slurry aluminum infiltration method and chemical vapor deposition method. Although the process equipment and process procedures of each method are obviously different, the core aluminum diffusion process needs to be carried out in a vacuum or an inert atmosphere such as high-purity argon, which greatly increases the preparation process cost and difficulty of the aluminum infiltration coating. The reactive aluminum infiltration process in air atmosphere based on the slurry aluminum infiltration process inherits the characteristics of short heat treatment cycle, high utilization rate of aluminum infiltration raw materials and high applicability to complex structures, and attempts to make the process low-cost and convenient, but the thickness of the aluminum oxide layer on the surface of the coating is uncontrollable, the surface roughness affects the aerodynamic performance of the equipment, and there are many cracks in the coating, which greatly reduces the performance of the coating and limits the popularization and application of the process. Therefore, a material and process for blocking oxygen for the aluminum diffusion process in air atmosphere are needed. In view of this, the present application proposes a high-temperature-resistant anti-corrosion aluminum infiltration coating composed of an aluminum infiltration layer and a shielding layer and a preparation method thereof in air atmosphere. SUMMARY

[0003] Based on the above background, the present application aims to provide a high-temperature-resistant anti-corrosion aluminum infiltration coating and a preparation method thereof in air atmosphere for high-pressure compressor blades, casings and other adjacent components with a working temperature of 500-1000 DEG C in gas turbines and aero-engines.

[0004] Therefore, according to an aspect of an embodiment of the present application, a preparation method of a high-temperature-resistant anti-corrosion aluminum infiltration coating is provided, which comprises the following steps:

[0005] Step S1: preparation of a filtration layer: aluminum infiltration slurry is coated on a metal substrate in the form of air spraying, dipping or brushing, and an aluminum infiltration slurry layer is obtained after the coating is dried. The film thickness of the aluminum infiltration slurry layer after drying is controlled to be 30-50 microns. The metal substrate coated with the aluminum infiltration slurry layer is directly placed in 450-500 DEG C for 5-10 min for heat degumming, and then cooled to room temperature in air atmosphere to obtain an aluminum infiltration layer.

[0006] Step S2 shielding layer preparation: shielding coating is applied on the surface of aluminizing layer by air spraying or brushing, and the shielding layer is obtained after the coating is dried. The total film thickness of the shielding layer and the aluminizing layer is controlled to be not more than 80 μm;

[0007] Step S3 coating heat treatment in air atmosphere: the metal substrate coated with the aluminizing layer and the shielding layer is heated to 500 ℃ at a heating rate of 1-2 ℃ / min, and then heated to 700 ℃ at a heating rate of 5-10 ℃ / min after being kept at 500 ℃ for 30-60 min. After being kept at 700 ℃ for 1.5-2 h, the metal substrate is cooled to 150 ℃ at a cooling rate of 10-15 ℃ / min, and then cooled to room temperature in air. The high-temperature corrosion-resistant aluminizing coating prepared on the metal substrate is obtained.

[0008] Optionally, the step S1 further comprises preparation of modified flaky aluminum powder:

[0009] One of toluene, xylene or n-hexane is taken as a solvent to dissolve end-methyl or end-vinyl polysilazane, and the mass ratio of the polysilazane to the solvent is 1:15-25, which is recorded as solution A. The same solvent is taken to dissolve end-hydroxyl polydimethylsiloxane, and the mass ratio of the end-hydroxyl polydimethylsiloxane to the solvent is 1:5-10, which is recorded as solution B. The flaky aluminum powder is dispersed in solution A, and the mass ratio of the two is 1:5-10. After the temperature is stable, solution B is added dropwise in solution A, and the mass ratio of solution A to solution B is 1:0.3-0.5. After the addition is completed, the reaction is carried out under the conditions of nitrogen atmosphere and condensation reflux at 120-150 ℃ oil bath stirring for 2-3 h. The product is filtered and washed with acetone for multiple times, and then dried in vacuum at 50-80 ℃ for 6-8 h to obtain the modified flaky aluminum powder.

[0010] Optionally, the step S1 further comprises preparation of aluminizing slurry: the binder, the associative polyurethane thickener, the spherical aluminum powder, the modified flaky aluminum powder, the metal oxide and the solvent are weighed according to the mass ratio. The binder is dissolved in the solvent, and after the solvent is clarified, the binder solution, the associative polyurethane thickener, the spherical aluminum powder, the modified flaky aluminum powder and the metal oxide are dispersed at a constant temperature of 10-25 ℃ in water to obtain the aluminizing slurry.

[0011] Optionally, the step S2 further comprises preparation of modified corrosion-resistant filler: the hexagonal boron nitride is dispersed in 70%-95% ethanol-water solution, and formic acid or acetic acid is used to adjust the above dispersion to be weakly acidic. One of trimethylmethoxysilane and vinyltriethoxysilane is added in the mixture at a mass ratio of 0.01-0.05:1, and the mixture is stirred at 40-80 ℃ water bath with condensation reflux for 1-3 h. The product is filtered and washed, and then dried at 80-90 ℃ to obtain the modified corrosion-resistant filler.

[0012] Optionally, the preparation of the shielding coating is also included: the modified film-forming resin, the modified anticorrosive filler, various additives and diluents are weighed according to the mass ratio, mixed and ground, the particle size of the mixture is less than 25 μm, and the shielding coating is obtained.

[0013] Optionally, the spherical aluminum powder accounts for 35-50% of the mass of the aluminizing slurry.

[0014] Optionally, the modified flaky aluminum powder accounts for 3-6% of the mass of the aluminizing slurry, and is a flaky aluminum powder coated with a hydroxyl-terminated polydimethylsiloxane and polysilazane copolymer.

[0015] Optionally, the metal oxide accounts for 0.5-1% of the mass of the aluminizing slurry, and is one of cerium oxide and zirconium oxide.

[0016] Optionally, the spherical aluminum powder is composed of spherical aluminum powders with particle size distribution concentrated in 5-10 μm and 25-40 μm, and the mass ratio of the two is 6-8:2-4.

[0017] According to another aspect of the embodiment of the present application, a high-temperature-resistant anticorrosive aluminized coating is also provided, which is prepared by any of the methods, and comprises an aluminized layer and a shielding layer, wherein the aluminized layer is formed by drying and heat removing the aluminizing slurry, and the shielding layer is formed by heat curing the shielding coating, and the aluminum diffusion process is completed by heat treatment to form

[0018] The advantages of the present application include:

[0019] 1. The coating is composed of an aluminized layer and a shielding layer, the cross-linked and cured shielding layer blocks the oxygen in the air for the aluminum diffusion process, so that the process no longer needs to be carried out under the protection of vacuum or inert atmosphere such as high-purity argon, greatly reducing the preparation process cost and process difficulty of the aluminized coating.

[0020] 2. The modified flaky aluminum powder in the aluminized layer provides silicon elements for the aluminum diffusion process and controls the diffusion activity, and adjusts the stress in the coating during the heat treatment process, so that cracks are not easily generated in the aluminized coating.

[0021] 3. Zirconium boride is introduced into the shielding layer, and at high temperature, the zirconium boride is oxidized to form zirconia and boron oxide, the boron oxide is melted, and a molten film layer is formed on the outer surface of the shielding layer by capillary action, further blocking the oxygen.

[0022] The high-temperature-resistant anticorrosive aluminized coating has the following performance advantages:

[0023] Excellent high-temperature corrosion resistance: can provide iron-based and nickel-based high-temperature alloys with a working temperature range of 500-1000℃ with long-term high-temperature corrosion protection close to 1000h; between 500-700℃, the shielding layer can block the corrosion medium and oxygen, and the aluminizing coating is almost not corroded or oxidized, thereby improving the corrosion resistance of the coating;

[0024] Convenient process: short heat treatment cycle, high utilization rate of aluminizing raw materials and high applicability to complex structures. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A flowchart of a preparation method of a high-temperature corrosion-resistant aluminized coating according to the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0027] According to an aspect of an embodiment of the present application, a preparation method of a high-temperature corrosion-resistant aluminized coating is provided, comprising:

[0028] Step S1: Preparation of the aluminizing layer: the aluminizing slurry is coated on the metal substrate by air spraying, dipping or brushing, and the aluminizing slurry layer is obtained after the coating is dried. The film thickness of the aluminizing slurry layer after drying is controlled to be 30-50μm. The metal substrate coated with the aluminizing slurry layer is directly placed in 450-500℃ for 5-10min of heat degumming, and then cooled to room temperature in air atmosphere to obtain the aluminizing layer.

[0029] Step S2: Preparation of the shielding layer: the shielding coating is coated on the surface of the aluminizing layer by air spraying or brushing, and the shielding layer is obtained after the coating is dried. The total film thickness of the shielding layer and the aluminizing layer is controlled to be not more than 80μm.

[0030] Step S3: Heat treatment of the coating in air atmosphere: the metal substrate coated with the aluminizing layer and the shielding layer is heated to 500℃ at a heating rate of 1-2℃ / min, and then heated to 700℃ at a heating rate of 5-10℃ / min after holding for 30-60min. After holding for 1.5-2h, the temperature is decreased to 150℃ at a cooling rate of 10-15℃ / min, and then cooled to room temperature in air. The metal substrate is the prepared high-temperature corrosion-resistant aluminized coating.

[0031] Further, the step S1 further comprises preparation of the modified sheet-like aluminum powder:

[0032] Dissolve end-methyl or end-vinyl polysilazane in one of toluene, xylene or n-hexane, the mass ratio of polysilazane to solvent is 1:15-25, denoted as solution A, dissolve end-hydroxyl polydimethylsiloxane in the same solvent, the mass ratio of end-hydroxyl polydimethylsiloxane to solvent is 1:5-10, denoted as solution B, disperse flaky aluminum powder in solution A, the mass ratio of solution A to flaky aluminum powder is 1:5-10, after the temperature is stable, add solution B drop by drop into solution A, the mass ratio of solution A to solution B is 1:0.3-0.5, after the addition is completed, stir under the condition of nitrogen atmosphere and condensation reflux at 120-150℃ oil bath for 2-3h, filter the product and wash with acetone for several times, dry in vacuum at 50-80℃ for 6-8h, to obtain modified flaky aluminum powder.

[0033] Further, step S1 further comprises preparation of aluminizing slurry: take binder, associative polyurethane thickener, spherical aluminum powder, modified flaky aluminum powder, metal oxide and solvent according to mass ratio, first dissolve the binder in the solvent, after the solvent is clear, disperse the binder solution, associative polyurethane thickener, spherical aluminum powder, modified flaky aluminum powder and metal oxide at 10-25℃ constant temperature water at high speed, finally obtain aluminizing slurry.

[0034] Further, step S2 further comprises preparation of modified anticorrosive filler: disperse hexagonal boron nitride in 70%-95% ethanol-water solution, apply formic acid or acetic acid to adjust the above dispersion to weakly acidic; add one of trimethylmethoxysilane and vinyltriethoxysilane in the mixture, the mass ratio of trimethylmethoxysilane to hexagonal boron nitride is 0.01-0.05:1, stir at 40-80℃ water bath with condensation reflux for 1-3h, filter and wash the product, and dry at 80-90℃, to obtain modified anticorrosive filler.

[0035] Further, it further comprises preparation of shielding coating: mix and grind modified film-forming resin, modified anticorrosive filler, various additives and diluent according to mass ratio, the particle size of the mixture is less than 25μm, to obtain shielding coating.

[0036] Further, the spherical aluminum powder accounts for 35-50% of the mass of the aluminizing slurry.

[0037] Further, the modified flaky aluminum powder accounts for 3-6% of the mass of the aluminizing slurry, which is flaky aluminum powder coated by end-hydroxyl polydimethylsiloxane and polysilazane copolymer.

[0038] Further, the metal oxide accounts for 0.5-1% of the mass of the aluminizing slurry, which is one of cerium oxide and zirconium oxide.

[0039] Further, the spherical aluminum powder is composed of spherical aluminum powder with particle size distribution concentrated in 5-10 μm and 25-40 μm, and the mass ratio of the two is 6-8:2-4.

[0040] Further, the binder accounts for 3-5% of the mass of the aluminizing slurry, and is mainly one of polyethylene glycol and polyvinyl alcohol.

[0041] Further, the associative polyurethane thickening agent accounts for 0.5-2% of the mass of the aluminizing slurry.

[0042] Further, the modified flaky aluminum powder accounts for 3-6% of the mass of the aluminizing slurry. The flaky aluminum powder is mainly coated with a copolymer of hydroxyl-terminated polydimethylsiloxane and polysilazane.

[0043] Further, the metal oxide accounts for 0.5-1% of the mass of the aluminizing slurry, and is mainly one of cerium oxide and zirconium oxide.

[0044] Further, the balance of the mass of the aluminizing slurry is solvent, which is mainly deionized water.

[0045] Further, the number average molecular weight of the polyethylene glycol and polyvinyl alcohol should be controlled to be between 10,000 and 30,000;

[0046] Further, the associative polyurethane thickening agent mainly contains non-ionic polyether polyurethane with a number average molecular weight controlled to be between 3,500 and 6,000;

[0047] Further, the associative polyurethane thickening agent is preferably one of commercially available products BYK RHEOBYK-H7625VF and Viscoplus 3030.

[0048] Further, the flaky aluminum powder has a flaky layer diameter distribution concentrated between 15 and 25 μm.

[0049] Further, the number average molecular weight of the hydroxyl-terminated polydimethylsiloxane used for coating modification of the flaky aluminum powder should be controlled to be between 2,500 and 3,000.

[0050] Further, the number average molecular weight of the polysilazane used for coating modification of the flaky aluminum powder should be controlled to be between 1,000 and 1,500, and the active group is methyl or vinyl.

[0051] Further, the metal oxide has a particle size distribution concentrated between 5 and 10 μm.

[0052] Further, the film-forming resin accounts for 40-50% of the mass of the shielding coating, and is mainly perhydrous polysilazane with a terminal methyl group or a terminal vinyl group.

[0053] ​Further, the modified sheet filler accounts for 10-15% of the mass of the shielding coating, and is mainly hexagonal boron nitride modified by silane.

[0054] Further, the zirconium diboride powder accounts for 5-8% of the mass of the shielding coating.

[0055] Further, the functional auxiliary agent accounts for 1-2% of the mass of the shielding coating, and is mainly composed of dispersing agent and anti-settling auxiliary agent.

[0056] Further, the balance of the mass of the shielding coating is diluent, and the diluent is mainly composed of dimethylbenzene and butyl acetate.

[0057] Further, the number average molecular weight of the perhydridopolysilazane with terminal methyl or terminal vinyl should be controlled to be between 1000 and 1500.

[0058] Further, the hexagonal boron nitride used for modifying the sheet filler has a sheet layer diameter distribution concentrated between 15 and 25 μm.

[0059] Further, the silane used for modifying the hexagonal boron nitride is preferably one of trimethylmethoxysilane and vinyltriethoxysilane.

[0060] Further, the particle size distribution of the zirconium diboride powder is concentrated between 1 and 5 μm.

[0061] Further, the mass ratio of dimethylbenzene to butyl acetate in the diluent is 1-0.5:0.5.

[0062] According to the technical scheme of the present application, the high-temperature-resistant anti-corrosion and anti-permeation aluminum coating is composed of an aluminum-permeation layer and a shielding layer, wherein the aluminum-permeation layer is formed by drying the aluminum-permeation slurry, the shielding layer is formed by curing the shielding coating, and the coating is completed by the aluminum diffusion process after heat treatment. By introducing the associative polyurethane thickening agent into the aluminum-permeation slurry, the stability of the slurry and the thixotropy of the coating process can be ensured while reducing the amount of binder. The sheet aluminum powder coated by the hydroxyl-terminated polydimethylsiloxane and polysilazane copolymer is modified to introduce silicon element into the aluminum-permeation layer, and the reaction activity of the aluminum diffusion process is controlled in cooperation with metal oxides such as cerium oxide and zirconium oxide. The shielding layer uses perhydridopolysilazane as the film-forming resin, which can withstand the process temperature of low-temperature aluminum permeation, and the introduced zirconium boride can be oxidized to form zirconium oxide and boron oxide at this temperature. The molten boron oxide further forms a molten film layer on the outer surface of the shielding layer through capillary action, and cooperates with the sheet filler inside the shielding layer to block oxygen, so that the aluminum diffusion process can be completed in an air atmosphere.

[0063] Example 1

[0064] The application discloses a high-temperature-resistant anti-corrosion aluminum infiltration coating, which is composed of an aluminum infiltration layer and a shielding layer.

[0065] The aluminum infiltration slurry is a single-component coating, which is composed of a binder, an associated polyurethane thickening agent, spherical aluminum powder, modified flaky aluminum powder, metal oxide and solvent.

[0066] Ingredient Specification Mass / g Binder Industrial grade 3 Associative polyurethane thickener Industrial grade 2 Spherical aluminum powder Industrial grade 50 Modified flaky aluminum powder Self-made 3 Metal oxide Analytically pure 0.5 Solvent Self-made 41.5

[0067] The binder is polyvinyl alcohol with a number average molecular weight of 15000.

[0068] The associated polyurethane thickening agent is a commercially available product BYK RHEOBYK-H 7625VF.

[0069] The spherical aluminum powder is composed of spherical aluminum powder with particle size distribution concentrated in 5-10 mu m and 25-40 mu m in a mass ratio of 8:2.

[0070] The modified flaky aluminum powder is a copolymer coated modified flaky aluminum powder of hydroxyl-terminated polydimethylsiloxane and methyl-terminated polysilazane, wherein the number average molecular weight of the hydroxyl-terminated polydimethylsiloxane is 2500, the number average molecular weight of the methyl-terminated polysilazane is 1500, and the flaky aluminum powder has a flaky diameter concentrated in 15-25 mu m.

[0071] The metal oxide is zirconium oxide with particle size distribution concentrated in 5-10 mu m.

[0072] The solvent of the aluminum infiltration slurry is deionized water.

[0073] The shielding coating is a single-component coating, which is composed of a film-forming resin, modified flaky filler, zirconium diboride powder, functional additive and diluent, and is configured in a proportion of 100 g.

[0074] Ingredient Specification Mass / g Film-forming resin Industrial grade 50 Modified flaky filler Self-made 15 Zirconium diboride Industrial grade 8 Functional aid Industrial grade 2 Diluent Industrial grade 30

[0075] The film-forming resin is vinyl-terminated perhydrogenated polysilazane with a number average molecular weight of 1500.

[0076] The modified flaky filler is hexagonal boron nitride modified by trimethylmethoxysilane, and the flaky diameter distribution of the hexagonal boron nitride is concentrated in 15-25 mu m.

[0077] The particle size distribution of the zirconium diboride powder is concentrated in 1-5 mu m.

[0078] The functional additive is composed of 1.5 g of dispersing aid and 0.5 g of anti-settling aid.

[0079] The diluent is prepared by mixing 15 g of xylene with 15 g of butyl acetate.

[0080] A method for preparing a high-temperature-resistant, corrosion-resistant, and aluminum-infiltrated coating in an air atmosphere, the method comprising the following steps:

[0081] (I) Preparation of the aluminum-infiltrated layer

[0082] (1) Preparation of modified flaky aluminum powder: Dissolve the polymethylsilazane in xylene, with a mass ratio of polymethylsilazane to solvent of 1:20, and label the solution as solution A. Dissolve the hydroxyl-terminated polydimethylsiloxane in the same solvent, with a mass ratio of hydroxyl-terminated polydimethylsiloxane to solvent of 1:10, and label the solution as solution B. Disperse the untreated flaky aluminum powder in solution A, with a mass ratio of flaky aluminum powder to solution A of 1:5. After the temperature of the dispersion stabilizes, add solution B dropwise to solution A, with a mass ratio of solution A to solution B of 1:0.5. After the addition is complete, stir the mixture in an oil bath at 150°C under a nitrogen atmosphere with reflux for 2-3 hours. Filter the product and wash it with acetone multiple times. Dry the product in a vacuum oven at 50-80°C for 6-8 hours to obtain the modified flaky aluminum powder.

[0083] (2) Preparation of the aluminum-infiltrated slurry: Weigh the binder, the associative polyurethane thickener, the spherical aluminum powder, the modified flaky aluminum powder, the metal oxide, and the solvent according to the mass ratio. Dissolve the binder in the solvent first. After the solution is clear, place the binder solution, the associative polyurethane thickener, the spherical aluminum powder, the modified flaky aluminum powder, and the metal oxide in a high-speed disperser. Disperse them at a constant temperature of 10-25°C and a speed of 1000 rpm for 4 hours to obtain the aluminum-infiltrated slurry.

[0084] (3) Preparation of the aluminum-infiltrated layer: Apply the aluminum-infiltrated slurry to the metal substrate by air spraying, dipping, or brushing. After the coating dries, an aluminum-infiltrated slurry layer is obtained. Control the film thickness of the aluminum-infiltrated slurry layer after drying to be 35 μm. Place the metal substrate coated with the aluminum-infiltrated slurry layer directly into a muffle furnace at 500°C for 5 minutes to remove the adhesive. Then, cool the metal substrate to room temperature in an air atmosphere to obtain the aluminum-infiltrated layer.

[0085] (II) Preparation of the shielding layer

[0086] (1) Preparation of modified flaky filler: Disperse the untreated hexagonal boron nitride in a 70% ethanol-water solution. Adjust the dispersion to weakly acidic with formic acid or acetic acid. Add trimethylmethoxysilane to the mixture at a mass ratio of 0.05:1. Stir the mixture in a water bath at 80°C with reflux for 3 hours. Filter and wash the product, and dry it in an oven at 90°C to obtain the modified flaky filler.

[0087] (2) Preparation of shielding coating: the modified film-forming resin, modified anticorrosive filler, various additives and diluent are weighed according to the mass ratio, put into a container to obtain a mixture, and put into a sand mill for grinding, the overall particle size of the mixture is controlled to be less than 25 μm, and the shielding coating is obtained.

[0088] (3) Preparation of shielding layer

[0089] The shielding coating is coated on the surface of the aluminizing layer by air spraying or brushing, and the shielding layer is obtained after the coating is dried. The total film thickness of the shielding layer and the aluminizing layer is controlled to be 80 μm.

[0090] (Three) Heat treatment of coating in air atmosphere

[0091] The metal substrate coated with the aluminizing layer and the shielding layer is placed in a muffle furnace, the temperature is raised to 500 ℃ at a rate of 1-2 ℃ / min, and then the temperature is raised to 700 ℃ at a rate of 5-10 ℃ / min after being kept for 60 min, and then the temperature is lowered to 150 ℃ at a rate of 10-15 ℃ / min, and then the metal substrate is taken out from the muffle furnace and cooled to room temperature in air. The high-temperature corrosion-resistant aluminizing coating is prepared on the metal substrate.

[0092] The high-temperature corrosion-resistant aluminizing coating is prepared in air atmosphere, and the coating has excellent oxidation resistance and corrosion resistance, can withstand 1000 ℃ thermal oxidation for 100 h, and can withstand 3000 h of neutral salt spray corrosion. The coating does not blister, crack or fall off.

[0093] Example 2

[0094] A high-temperature corrosion-resistant aluminizing coating, the coating is composed of an aluminizing layer and a shielding layer. The aluminizing layer is formed by drying and heat removing the aluminizing slurry, and the shielding layer is formed by heating and curing the shielding coating. The aluminum diffusion process is completed by heat treatment.

[0095] The aluminizing slurry is a single-component coating, which is composed of a binder, an associated polyurethane thickener, spherical aluminum powder, modified flaky aluminum powder, metal oxide and solvent. The aluminizing slurry is prepared according to the proportion of 100 g.

[0096] Ingredient Specification Mass / g Binder Industrial grade 4 Associative polyurethane thickener Industrial grade 0.5 Spherical aluminum powder Industrial grade 50 Modified flaky aluminum powder Self-made 3 Metal oxide Analytically pure 0.5 Solvent Self-made 42

[0097] The binder is selected from polyethylene glycol with a number average molecular weight of 10000;

[0098] The associated polyurethane thickener is selected from commercially available products Viscoplus 3030;

[0099] The spherical aluminum powder is composed of spherical aluminum powder with particle size distribution concentrated in 5-10 μm and 25-40 μm, and the mass ratio is 7:3.

[0100] The modified flaky aluminum powder is a copolymer coated modified flaky aluminum powder of end-hydroxyl polydimethylsiloxane and end-vinyl polysilazane, wherein the number average molecular weight of the end-hydroxyl polydimethylsiloxane is 2500, the number average molecular weight of the end-vinyl polysilazane is 1500, and the flaky aluminum powder has a flake diameter distribution concentrated between 15-25 μm.

[0101] The metal oxide is selected from zirconium oxide having a particle size distribution concentrated between 5-10 μm

[0102] The solvent of the aluminizing slurry is selected from deionized water.

[0103] The shielding coating is a single-component coating, which is composed of a film-forming resin, a modified flaky filler, zirconium diboride powder, a functional additive, and a diluent. The shielding coating is prepared by mixing the components in a ratio of 100 g.

[0104] Ingredient Specification Mass / g Film-forming resin Industrial grade 45 Modified flaky filler Self-made 15 Zirconium diboride Industrial grade 5 Functional aid Industrial grade 2 Diluent Industrial grade 33

[0105] The film-forming resin is selected from end-methyl polyperhydropolysilazane having a number average molecular weight of 1500.

[0106] The modified flaky filler is hexagonal boron nitride modified by vinyltriethoxysilane, and the hexagonal boron nitride has a flake diameter distribution concentrated between 15-25 μm.

[0107] The zirconium diboride powder has a particle size distribution concentrated between 1-5 μm.

[0108] The functional additive is composed of 1.5 g of a dispersing agent and 0.5 g of an anti-settling agent.

[0109] The diluent is xylene.

[0110] A method for preparing a high-temperature-resistant anticorrosive aluminized coating in an air atmosphere, which comprises the following steps:

[0111] (I) Preparation of the aluminized layer

[0112] (1) Preparation of the modified flaky aluminum powder: end-methyl polysilazane is dissolved in xylene, and the mass ratio of the polysilazane to the solvent is 1:15, which is denoted as solution A. End-hydroxyl polydimethylsiloxane is dissolved in the same solvent, and the mass ratio of the end-hydroxyl polydimethylsiloxane to the solvent is 1:10, which is denoted as solution B. Untreated flaky aluminum powder is dispersed in solution A, and the mass ratio of the two is 1:5. After the temperature of the dispersion is stabilized, solution B is added dropwise to solution A, and the mass ratio of solution A to solution B is 1:0.3. After the dropwise addition is completed, the mixture is stirred at 150°C under a nitrogen atmosphere with reflux condensation for 2-3 h. The product is filtered and washed with acetone for multiple times, and then dried in a vacuum oven at 50-80°C for 6-8 h to obtain the modified flaky aluminum powder.

[0113] (2) Preparation of aluminizing slurry: The binder, the associative polyurethane thickener, the spherical aluminum powder, the modified flaky aluminum powder, the metal oxide and the solvent are weighed according to the mass ratio, the binder is dissolved in the solvent first, and after the solution is clear, the binder solution, the associative polyurethane thickener, the spherical aluminum powder, the modified flaky aluminum powder and the metal oxide are placed in a high-speed disperser and dispersed at a speed of 800 rpm for 6 hours in a constant temperature water bath at 10-25°C, and finally the aluminizing slurry is obtained.

[0114] (3) Preparation of aluminizing layer: The aluminizing slurry is coated on the metal substrate by air spraying, dipping or brushing, and after the coating is dried, the aluminizing slurry layer is obtained, and the film thickness of the aluminizing slurry layer after drying is controlled to be 50 μm. The metal substrate coated with the aluminizing slurry layer is directly placed in a muffle furnace at 500°C for 5 minutes of heat degumming, and then cooled to room temperature in air atmosphere to obtain the aluminizing layer.

[0115] (B) Preparation of shielding layer

[0116] (1) Preparation of modified flaky filler: The untreated hexagonal boron nitride is dispersed in a 95% ethanol-water solution, and formic acid or acetic acid is used to adjust the above dispersion to weakly acidic; vinyltriethoxysilane is added to the mixture at a mass ratio of 0.03:1 with respect to the hexagonal boron nitride, and stirred at 80°C in a water bath with reflux condensation for 3 hours. The product is filtered, washed and dried in an oven at 90°C to obtain the modified flaky filler.

[0117] (2) Preparation of shielding coating: The modified film-forming resin, the modified anticorrosive filler, various additives and the diluent are weighed according to the mass ratio, placed in a container to obtain a mixture and ground in a sand mill, and the overall particle size of the mixture is controlled to be less than 25 μm to obtain the shielding coating.

[0118] (3) Preparation of shielding layer

[0119] The shielding coating is coated on the surface of the aluminizing layer by air spraying or brushing, and after the coating is dried, the shielding layer is obtained, and the total film thickness of the shielding layer and the aluminizing layer is controlled to be 80 μm.

[0120] (C) Heat treatment of coating in air atmosphere

[0121] The metal substrate coated with the aluminizing layer and the shielding layer is placed in a muffle furnace, heated to 500°C at a rate of 1-2°C / min, kept at 500°C for 60 min, then heated to 700°C at a rate of 5-10°C / min, kept at 700°C for 2 h, then cooled to 150°C at a rate of 10-15°C / min, and taken out of the muffle furnace and cooled to room temperature in air, and the high-temperature corrosion-resistant aluminizing coating on the metal substrate is prepared.

[0122] The high-temperature-resistant anticorrosive aluminum infiltration coating is prepared in an air atmosphere, has excellent oxidation resistance and corrosion resistance, can withstand 1000 DEG C thermal oxidation for 100 hours, and can withstand 3000 hours of neutral salt spray corrosion, and the coating does not bubble, crack or fall off.

[0123] The above is only a specific embodiment of the present application, which is described in detail, and the part not described in detail is the conventional technology. However, the protection scope of the present application is not limited to this, any change or replacement that can be easily thought of by those skilled in the art within the technical range disclosed by the present application should be covered within the protection scope of the present application. The protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a high-temperature resistant, corrosion-resistant, aluminized coating, characterized in that, include: Step S1: Preparation of the aluminizing layer: The aluminizing slurry is applied to the metal substrate by air spraying, dip coating or brushing. After the coating is completely dry, the aluminizing slurry layer is obtained. The film thickness of the aluminizing slurry layer after drying is controlled to be 30~50μm. The metal substrate coated with the aluminizing slurry layer is directly placed in 450~500℃ for 5~10min for hot desmearing. Then it is cooled to room temperature in air atmosphere to obtain the aluminizing layer. Step S2: Shielding layer preparation: Apply the shielding coating to the surface of the aluminized layer by air spraying or brushing. After the coating is fully dry, the shielding layer is obtained. Control the total film thickness of the shielding layer and the aluminized layer to not exceed 80 μm. Step S3: Heat treatment of coating in air atmosphere: The metal substrate coated with the aluminized layer and the shielding layer is heated to 500°C at a heating rate of 1~2°C / min and held for 30~60min. Then, it is heated to 700°C at a heating rate of 5~10°C / min and held for 1.5~2h. Finally, it is cooled to 150°C at a cooling rate of 10~15°C / min and cooled to room temperature in air. The high-temperature resistant and corrosion-resistant aluminized coating is then prepared on the metal substrate. Step S1 also includes the preparation of modified flake aluminum powder: Dissolve a polysilazane with methyl or vinyl terminals in a solvent of toluene, xylene, or n-hexane, with a mass ratio of polysilazane to solvent of 1:15-25, denoted as solution A. Dissolve a polydimethylsiloxane with hydroxyl terminals in the same solvent, with a mass ratio of polydimethylsiloxane to solvent of 1:5-10, denoted as solution B. Disperse flake aluminum powder in solution A, with a mass ratio of 1:5-10. After the dispersion temperature stabilizes, weigh solution B and add it dropwise to solution A, with a mass ratio of 1:0.3-0.5 between solution A and solution B. After the addition is complete, stir the reaction in an oil bath at 120-150°C for 2-3 hours under a nitrogen atmosphere with reflux condensation. Filter the product and wash it several times with acetone. Dry it in a vacuum at 50-80°C for 6-8 hours to obtain modified flake aluminum powder. Step S1 further includes the preparation of aluminizing slurry: The binder, associative polyurethane thickener, spherical aluminum powder, modified flake aluminum powder, metal oxide, and solvent are weighed according to the mass ratio. The binder is first dissolved in the solvent. After the solvent is clarified, the binder solution, associative polyurethane thickener, spherical aluminum powder, modified flake aluminum powder, and metal oxide are dispersed at high speed in a constant temperature water bath at 10-25°C to finally obtain the aluminizing slurry. The spherical aluminum powder accounts for 35-50% of the mass of the aluminizing slurry; the modified flake aluminum powder accounts for 3-6% of the mass of the aluminizing slurry and is hydroxyl-terminated polydimethylsiloxane and polysilazane copolymer-coated modified flake aluminum powder; the metal oxide accounts for 0.5-1% of the mass of the aluminizing slurry and is either cerium oxide or zirconium oxide; the spherical aluminum powder is composed of a compound of spherical aluminum powder with particle sizes concentrated at 5-10 μm and 25-40 μm, and the mass ratio of the two is 6-8:2-4. Step S2 also includes the preparation of modified anticorrosive filler: hexagonal boron nitride is dispersed in a 70%~95% ethanol-water solution, and the dispersion is adjusted to a weakly acidic state using formic acid or acetic acid for later use; one of trimethylmethoxysilane and vinyltriethoxysilane in a mass ratio of 0.01~0.05:1 to hexagonal boron nitride is added to the mixture, and the mixture is stirred and reacted in a water bath at 40~80℃ with reflux condensation for 1~3 hours, the product is filtered and washed, and then dried at 80~90℃ to obtain modified anticorrosive filler; The preparation of the shielding coating also includes: weighing and mixing modified film-forming resin, modified anti-corrosion filler, zirconium diboride powder, various additives and diluent, and grinding them together. The particle size of the mixture is less than 25 μm to obtain the shielding coating. The film-forming resin accounts for 40-50% of the mass of the shielding coating, the modified anti-corrosion filler accounts for 10-15% of the mass of the shielding coating, the zirconium diboride powder accounts for 5-8% of the mass of the shielding coating, the various additives account for 1%-2% of the mass of the shielding coating, and the remainder is diluent.

2. A high-temperature resistant, corrosion-resistant, aluminized coating, characterized in that, The coating is prepared by the preparation method described in claim 1. The coating includes an aluminizing layer and a shielding layer. The aluminizing layer is formed by drying and hot degumming of the aluminizing slurry. The shielding layer is formed by heating and curing the shielding coating. The coating is finally formed by completing the aluminum diffusion process through heat treatment.

Images