A high-flatness aluminized coating and preparation method thereof

Abstract

The present invention relates to a high-flatness aluminized coating, the raw materials of which include: 10-15wt% inorganic cellulose, 1-3wt% organic linker, 15-25wt% dispersant, 17-25wt% aluminum powder, 0.5-0.8wt% ammonium chloride, 0.2-0.4wt% sodium fluoride, and 25-44wt% aluminum oxide powder. The present invention also relates to a method for preparing the high-flatness aluminized coating. The high-flatness aluminized coating provided by the present invention can solve the problem of existing aluminizing technology that the agglomeration of molten aluminum atoms during the aluminizing process remains 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.

Description

Technical Field

[0001] The present invention relates to the field of aluminized coatings, and in particular to a high-flatness aluminized coating and a preparation method thereof. Background Art

[0002] In order to meet high temperature conditions, traditional steam cracking furnace tubes are often made of high-temperature resistant chromium-nickel alloy steel. However, the nickel and iron elements in the alloy will migrate under high temperature, enrich on the inner surface of the steam cracking furnace tube and serve as catalytic active centers to accelerate the formation of coke, which greatly limits the operating efficiency of the steam cracking furnace. To address this problem, the generally adopted method is based on solid powder embedding co-infiltration technology. By preparing a single or multi-layer coating on the surface of the alloy substrate, these coatings can play a barrier role in shielding the iron and nickel elements in the substrate while improving the oxidation resistance and thermal corrosion resistance of the alloy material, thereby inhibiting the formation of coke during the reaction. At present, the use of solid powder embedding co-infiltration technology to infiltrate aluminum into the alloy substrate to prepare an aluminized layer on the substrate surface is considered to be one of the most effective means to improve the oxidation resistance and mechanical properties of the alloy and inhibit coking. Aluminizing technology has been widely used in the chemical industry.

[0003] CN109055890A discloses a method for thermally preparing a protective composite coating on ultra-high strength steel. The preparation method adopts co-penetration technology. The prepared protective composite coating is a protective coating with a four-layer organizational structure, which includes, from the inside to the outside, an Fe-Zn and Fe-Al intermetallic compound diffusion layer, a Zn-rich layer, an aluminum-silicon alloy layer, and a micro-nano oxide layer. Although the composite coating has high oxidation resistance and notch corrosion resistance, it also has the disadvantages of relatively complex raw material components. During the coating preparation process, the thermal diffusion effects of the raw material components are different, resulting in uncontrollable agglomeration of the raw material components during the co-penetration process. The prepared coating has low flatness, low wear resistance, and a short service life.

[0004] CN105695930A discloses a method for applying an aluminum-silicon coating to the surface of a large aspect ratio boiler tube. This method involves spraying a pre-prepared aluminum-silicon slurry onto a substrate, followed by drying, sintering, and sandblasting to produce the aluminum-silicon coating. This aluminum-silicon coating can be applied to high-temperature hydrocarbon cracking furnace tubes and exhibits high oxidation resistance and excellent coking inhibition. However, during the sintering process, aluminum agglomeration is evident, and the coating requires sandblasting, making the coating preparation process complex. Furthermore, the resulting composite coating has a low flatness.

[0005] 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, polishing the first aluminized layer, and then preparing a second aluminized layer at a lower co-infiltration temperature. The surface roughness of the resulting double-layer 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 cannot be controlled during the co-infiltration process.

[0006] CN104805399A discloses a colored slurry aluminum infiltration process. The raw materials used in the preparation of the slurry include polyvinyl alcohol, sodium hydroxymethyl cellulose, a thickener, an aluminum-supplying agent and water. Among them, polyvinyl alcohol, sodium carboxymethyl cellulose or potassium carboxymethyl cellulose, a thickener and water together constitute a binder. The function of the binder is to adhere the aluminum-supplying agent to the surface of the substrate, thereby making it easier for aluminum atoms to enter the interior of the substrate.

[0007] Based on the solid powder embedding co-infiltration technology, infiltrating aluminum elements into the alloy substrate to prepare an aluminized coating is considered to be one of the most effective means to improve the alloy's antioxidant properties and mechanical properties and inhibit coking. Aluminization technology has been widely used in the chemical industry. However, the existing aluminization technology generally has the problem that the agglomeration between molten aluminum atoms is still uncontrolled during the aluminization process, resulting in the aluminum atoms agglomerating with each other due to high-temperature thermal diffusion during the aluminization process, resulting in the prepared aluminized layer having low flatness. The low-flatness aluminized layer is more likely to adhere to dirt during use, which greatly reduces the properties and gain effect of the aluminized layer. Summary of the Invention

[0008] Based on the above, an object of the present invention is to provide a highly flat aluminized coating that can be used as a protective coating in steam cracking furnace tubes and high-temperature boilers. Another object of the present invention is to provide a method for rapidly preparing a highly flat aluminized coating.

[0009] To this end, the present invention provides a high-flatness aluminized coating, comprising: 10-15wt% of inorganic fiber, 1-3wt% of organic binder, 15-25wt% of dispersant, 17-25wt% of aluminum powder, 0.5-0.8wt% of ammonium chloride, 0.2-0.4wt% of sodium fluoride, and 25-44wt% of aluminum oxide powder.

[0010] In the high-flatness aluminized coating of the present invention, preferably, the inorganic fibers include one or more of aluminum silicate fibers, asbestos fibers, quartz fibers, and mullite fibers, and the length of the inorganic fibers is 10 to 40 μm.

[0011] In the high-flatness aluminized coating of the present invention, it is preferred that the organic linker is organic cellulose, and the organic cellulose includes one or more of carboxymethyl cellulose, ethyl cellulose, and polyvinyl alcohol.

[0012] In the high-flatness aluminized coating of the present invention, preferably, the dispersant is at least one of acetone, ethanol, tetrahydrofuran, and toluene.

[0013] The high-flatness aluminized coating described in the present invention preferably includes: 10-15wt% of inorganic fiber, 1-2.5wt% of organic binder, 20-25wt% of dispersant, 21-25wt% of aluminum powder, 0.5-0.8wt% of ammonium chloride, 0.2-0.4wt% of sodium fluoride, and 35-44wt% of aluminum oxide powder.

[0014] In the high-flatness aluminized coating of the present invention, it is preferred that the aluminum powder is nano-scale, and the particle size D90 of the aluminum powder is 50-100 nm.

[0015] In the high-flatness aluminized coating of the present invention, it is preferred that the alumina powder is micron-sized, and the particle size D90 of the alumina powder is 2 to 10 μm.

[0016] To this end, the present invention also provides a method for preparing a high-flatness aluminized coating, comprising the following steps:

[0017] (1) The surface of the substrate is purified;

[0018] (2) preparing a coating according to the composition ratio of the above-mentioned aluminized coating;

[0019] (3) spraying the coating prepared in step (2) onto the surface of the substrate, and forming a coating on the surface of the substrate after drying; preferably, the spraying is performed by a vapor phase spraying method;

[0020] (4) Placing the coated substrate obtained in step (3) in a permeation box for high-temperature solid-phase aluminizing to obtain a high-flatness aluminized coating.

[0021] In the method for preparing the high-flatness aluminized coating of the present invention, preferably, the thickness of the coating is 10-100 μm, more preferably 30-90 μm.

[0022] The method for preparing a high-flatness aluminized coating of the present invention preferably comprises the following conditions for high-temperature solid-phase aluminizing: temperature 900-1100°C, time 8-12h; further preferably, temperature 1000-1050°C, time 8-10h.

[0023] The beneficial effects of the present invention are as follows:

[0024] The high-flatness aluminized coating provided by the present invention can solve the problem that the existing aluminizing technology generally has that the agglomeration of molten aluminum atoms is still uncontrolled during the aluminizing process, which leads to the agglomeration of aluminum atoms due to high-temperature thermal diffusion during the aluminizing process, resulting in the prepared aluminized layer having low flatness.

[0025] Figures in the specification

[0026] Figure 1 This is the surface morphology of the high-flatness aluminized coating prepared in Example 1 of the present invention;

[0027] Figure 2 This is the cross-sectional morphology of the high-flatness aluminized coating prepared in Example 1 of the present invention;

[0028] Figure 3 This is the surface morphology of the aluminized coating prepared in Comparative Example 1 of the present invention;

[0029] Figure 4 This is the cross-sectional morphology of the aluminized coating prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The following examples of the present invention are described in detail. These examples are based on the technical solutions of the present invention and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following examples. Experimental methods in the following examples where specific conditions are not specified are generally based on conventional conditions. The technical solutions of the present invention are described in detail below through specific examples. % in the following examples and comparative examples is weight %.

[0031] The high-flatness aluminized coating provided by the present invention comprises: 10-15wt% of inorganic fibers, 1-3wt% of an organic linking agent, 15-25wt% of a dispersant, 17-25wt% of aluminum powder, 0.5-0.8wt% of ammonium chloride, 0.2-0.4wt% of sodium fluoride, and 25-44wt% of aluminum oxide powder.

[0032] In some embodiments, preferably, the inorganic fibers include one or more of aluminum silicate fibers, asbestos fibers, quartz fibers, and mullite fibers, and the length of the inorganic fibers is 10 to 40 μm.

[0033] In some embodiments, preferably, the organic linker is organic cellulose, and the organic cellulose includes one or more of carboxymethyl cellulose, ethyl cellulose, and polyvinyl alcohol.

[0034] In some embodiments, preferably, the dispersant is at least one of acetone, ethanol, tetrahydrofuran, and toluene.

[0035] In some embodiments, preferably, the high-flatness aluminized coating includes: 10-15wt% inorganic fiber, 1-2.5wt% organic binder, 20-25wt% dispersant, 21-25wt% aluminum powder, 0.5-0.8wt% ammonium chloride, 0.2-0.4wt% sodium fluoride, and 35-44wt% alumina powder.

[0036] In some embodiments, preferably, the aluminum powder is nano-scale, and the particle size D90 of the aluminum powder is 50-100 nm.

[0037] In some embodiments, preferably, the alumina powder is micron-sized, and the particle size D90 of the alumina powder is 2 to 10 μm.

[0038] The present invention also provides a method for preparing a high-flatness aluminized coating, comprising the following steps:

[0039] (1) The surface of the substrate is purified;

[0040] (2) preparing a coating according to the composition ratio of the above-mentioned aluminized coating;

[0041] (3) spraying the coating prepared in step (2) onto the surface of the substrate, and forming a coating on the surface of the substrate after drying; preferably, the spraying is performed by a vapor phase spraying method;

[0042] (4) Placing the coated substrate obtained in step (3) in a permeation box for high-temperature solid-phase aluminizing to obtain a high-flatness aluminized coating.

[0043] In some embodiments, preferably, the thickness of the coating is 10-100 μm, more preferably 30-90 μm.

[0044] In some embodiments, preferably, the conditions for the high-temperature solid-phase aluminizing are: temperature 900-1100° C., time 8-12 h; more preferably, temperature 1000-1050° C., time 8-10 h.

[0045] Example 1

[0046] The high-flatness aluminized coating provided in this embodiment comprises raw materials including 15% asbestos fiber, 1.5% organic coupling agent ethyl cellulose, 23% acetone, 21% aluminum powder, 0.6% ammonium chloride, 0.4% sodium fluoride, and 42.5% aluminum oxide powder.

[0047] The method for preparing a high-flatness aluminized coating comprises the following steps:

[0048] (1) First, Cr 35 Ni 45 Alloy substrate surface purification treatment to remove oil stains on the substrate surface;

[0049] (2) Prepare the coating according to the composition of the raw materials;

[0050] (3) spraying the prepared coating onto the substrate surface by vapor phase spraying, and the coating thickness after drying is 60 μm;

[0051] (4) The coated substrate is placed in a permeation box and kept at 1040°C for 9 hours for high-temperature solid-phase aluminizing to obtain a high-flatness protective aluminized coating. The surface morphology and cross-sectional morphology of the coating are shown in Figure 1 and Figure 2 shown.

[0052] Example 2

[0053] The high-flatness aluminized coating provided in this embodiment comprises raw materials including 15% aluminum silicate fiber, 2% organic binder carboxymethyl cellulose, 25% acetone, 22% aluminum powder, 0.6% ammonium chloride, 0.4% sodium fluoride, and 35% alumina powder.

[0054] The method for preparing a high-flatness aluminized coating comprises the following steps:

[0055] (1) First, Cr 35 Ni 45 Alloy substrate surface purification treatment to remove oil stains on the substrate surface;

[0056] (2) Prepare the coating according to the composition of the raw materials;

[0057] (3) spraying the prepared coating onto the substrate surface by vapor phase spraying, and the coating thickness after drying is 80 μm;

[0058] (4) The coated substrate is placed in a permeation 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.

[0059] Example 3

[0060] The high-flatness aluminized coating provided in this embodiment comprises raw materials including: 15% mullite fiber, 2.5% organic coupling agent polyvinyl alcohol, 23% acetone, 21% aluminum powder, 0.6% ammonium chloride, 0.4% sodium fluoride, and 37.5% alumina powder.

[0061] The method for preparing a high-flatness aluminized coating comprises the following steps:

[0062] (1) First, Cr 35 Ni 45 Alloy substrate surface purification treatment to remove oil stains on the substrate surface;

[0063] (2) Prepare the coating according to the composition of the raw materials;

[0064] (3) spraying the prepared coating onto the substrate surface by vapor phase spraying, and the coating thickness after drying is 80 μm;

[0065] (4) The coated substrate is placed in a permeation 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.

[0066] Example 4

[0067] The high-flatness aluminized coating provided in this embodiment comprises raw materials including: 15% aluminum silicate fiber, 2% organic binder carboxymethyl cellulose, 25% acetone, 22% aluminum powder, 0.6% ammonium chloride, 0.4% sodium fluoride, and 35% alumina powder.

[0068] The method for preparing a high-flatness aluminized coating comprises the following steps:

[0069] (1) First, Cr 35 Ni 45 Alloy substrate surface purification treatment to remove oil stains on the substrate surface;

[0070] (2) Prepare the coating according to the composition of the raw materials;

[0071] (3) spraying the prepared coating onto the substrate surface by vapor phase spraying, and the coating thickness after drying is 60 μm;

[0072] (4) The coated substrate is placed in a permeation box and kept at 1050°C for 10 hours for high-temperature solid-phase aluminizing, and finally a high-flatness protective aluminized coating is obtained.

[0073] Example 5

[0074] The high-flatness aluminized coating provided in this embodiment comprises raw materials including: 15% aluminum silicate fiber, 2% organic binder carboxymethyl cellulose, 25% acetone, 22% aluminum powder, 0.6% ammonium chloride, 0.4% sodium fluoride, and 35% alumina powder.

[0075] The method for preparing a high-flatness aluminized coating comprises the following steps:

[0076] (1) First, Cr 35 Ni 45 Alloy substrate surface purification treatment to remove oil stains on the substrate surface;

[0077] (2) Prepare the coating according to the composition of the raw materials;

[0078] (3) spraying the prepared coating onto the substrate surface by vapor phase spraying, and the coating thickness after drying is 80 μm;

[0079] (4) The coated substrate is placed in a permeation box and kept at 1000°C for 8 hours for high-temperature solid-phase aluminizing, and finally a high-flatness protective aluminized coating is obtained.

[0080] Comparative Example 1

[0081] The high-flatness aluminized coating provided in this comparative example comprises raw materials including: 25.2% aluminum powder, 0.7% ammonium chloride, 0.5% sodium fluoride, 51% aluminum oxide powder, and 27.6% acetone.

[0082] The method for preparing a high-flatness aluminized coating comprises the following steps:

[0083] (1) First, Cr 35 Ni 45 Alloy substrate surface purification treatment to remove oil stains on the substrate surface;

[0084] (2) Prepare the coating according to the composition of the raw materials;

[0085] (3) spraying the prepared coating onto the substrate surface by vapor phase spraying, and the coating thickness after drying is 80 μm;

[0086] (4) The coated substrate is placed in a permeation 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 surface morphology and cross-sectional morphology of the obtained aluminized coating are shown in Figure 3 and Figure 4 shown.

[0087] The surface roughness data of the high-flatness protective aluminized coating obtained in the above specific examples and the aluminized coating of comparative example 1 can be seen in Table 1.

[0088] Table 1

[0089] Sample name Surface roughness Ra (μm) Comparative Example 1 3.5 Example 1 0.9 Example 2 1.3 Example 3 1.6 Example 4 1.8 Example 5 1.3

[0090] As can be seen from Table 1, the smoothness of the aluminized coating obtained in the embodiment is greatly improved compared with the comparative example. Figure 1 and Figure 2 and Figure 3 and Figure 4 It can be seen from the comparison that the flatness of the aluminized coating obtained in Example 1 of the present invention is significantly higher than that of the aluminized coating obtained in Comparative Example 1.

[0091] In summary, the high-flatness aluminized coating provided by the present invention can solve the problem that the existing aluminizing technology is still uncontrolled during the aluminizing process due to the agglomeration of molten aluminum atoms, which leads to the agglomeration of aluminum atoms due to high-temperature thermal diffusion during the aluminizing process, resulting in the prepared aluminized layer having low flatness.

[0092] 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 present invention.

Claims

1. A high-flatness aluminized coating, characterized in that: The raw materials include: 10-15 wt% of inorganic fiber, 1-3 wt% of organic coupling agent, 15-25 wt% of dispersant, 17-25 wt% of aluminum powder, 0.5-0.8 wt% of ammonium chloride, 0.2-0.4 wt% of sodium fluoride, and 25-44 wt% of aluminum oxide powder; Wherein, the inorganic fiber includes one or more of aluminum silicate fiber, asbestos fiber, quartz fiber, and mullite fiber; The organic linking agent includes one or more of carboxymethyl cellulose, ethyl cellulose, and polyvinyl alcohol; The dispersant is at least one of acetone, ethanol, tetrahydrofuran and toluene.

2. The aluminized coating according to claim 1, characterized in that The length of the inorganic fiber is 10-40 μm.

3. The aluminized coating according to claim 1, characterized in that include: 10~15 wt% inorganic fiber, 1~2.5wt% organic binder, 20~25 wt% dispersant, 21~25 wt% aluminum powder, 0.5~0.8 wt% ammonium chloride, 0.2~0.4 wt% sodium fluoride, 35~44 wt% alumina powder.

4. The aluminized coating according to claim 1, characterized in that The aluminum powder is nano-scale, and the particle size D90 of the aluminum powder is 50-100 nm.

5. The aluminized coating according to claim 1, characterized in that The alumina powder is micron-sized, and the particle size D90 of the alumina powder is 2-10 μm.

6. A method for preparing a high-flatness aluminized coating, characterized in that: The following steps are involved: (1) Purification of the substrate surface; (2) preparing a coating according to the composition ratio of the aluminized coating according to any one of claims 1 to 5; (3) spraying the coating prepared in step (2) onto the surface of the substrate, and forming a coating on the surface of the substrate after drying; (4) The coated substrate obtained in step (3) is placed in a permeation box for high-temperature solid-phase aluminizing to obtain a high-flatness aluminized coating.

7. The method for preparing a high-flatness aluminized coating according to claim 6, characterized in that: The thickness of the coating in step (3) is 10-100 μm.

8. The method for preparing a high-flatness aluminized coating according to claim 6, characterized in that: The thickness of the coating in step (3) is 30-90 μm.

9. The method for preparing a high-flatness aluminized coating according to claim 6, wherein: The conditions of the high-temperature solid-phase aluminizing are: temperature 900-1100° C., time 8-12 hours.

10. The method for preparing a high-flatness aluminized coating according to claim 6, characterized in that: The conditions of the high-temperature solid-phase aluminizing are: temperature 1000-1050° C., time 8-10 hours.

11. The method for preparing a high-flatness aluminized coating according to claim 6, characterized in that: The spraying in step (3) adopts a vapor phase spraying method.

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