Preparation method of anti-oxidation coating on surface of boiler tube wall

Abstract

The preparation method of the boiler tube wall surface anti-oxidation coating comprises the steps that a solid phase component and a liquid phase component are weighed and prepared according to the proportion, and coating slurry with different proportions is prepared for standby application after stirring and ball milling; performing surface cleaning and preheating treatment on a to-be-plated workpiece, spraying the coating slurry to the surface of the to-be-plated workpiece, and performing drying and curing treatment; and the to-be-plated workpiece with the cured coating layer is placed in an inert atmosphere to be subjected to heat treatment, the aluminum-silicon anti-oxidation coating is obtained on the surface of the to-be-plated workpiece after cooling, and surface residue treatment is conducted. According to the boiler tube wall surface anti-oxidation coating and the preparation method thereof, a prepared infiltrated layer is uniform in organization structure, moderate in thickness, sufficient in Al atom diffusion, good in metallurgical bonding with a base body, not prone to falling off and suitable for austenitic steel and high-temperature alloy parts used for workpieces with the large length-diameter ratio and various complex shapes such as large boilers and oil and gas field conveying pipelines; and the method has excellent industrial batch production benefits.

Description

Technical Field

[0001] Embodiments of the present disclosure belong to the technical field of material surface alloying and coating preparation, and particularly relate to a method for preparing an antioxidant coating on the surface of a boiler pipe wall. Background Art

[0002] The inner side of the boiler pipe wall is usually in a high-temperature, high-pressure and humid environment, and such conditions are likely to cause corrosion. The corrosion may be caused by oxidation, or may be due to the presence of dissolved oxygen, alkaline substances or other corrosive media in the water. Taking the flue gas side and the water side as examples, the flue gas side corrosion is usually due to the acidic substances contained in the flue gas, while the water side may be corroded by the corrosive substances in the water. In addition, under high-temperature and high-pressure environments, the stress inside the pipeline may cause stress corrosion cracking, which may lead to pipeline leakage and failure. To address these problems, it is necessary to prevent and solve them through reasonable design, material selection, anti-corrosion coatings, regular maintenance, etc. Among them, the preparation of anti-corrosion coatings is cost-effective.

[0003] Research shows that high-temperature coatings have obvious effects in solving component oxidation corrosion, wear, high-temperature ablation, etc. Specific types of high-temperature coatings can provide excellent corrosion resistance, resist corrosive substances in chemical media or flue gas, protect the base material from corrosion, and extend the service life of equipment. However, existing high-temperature coating technologies are mostly used for hot-end components such as aero-engine blades, rotors, and turbine disks with high temperatures, short action times, and small sizes. For the characteristics of the large aspect ratio structure of the flow components of energy equipment, high temperature, long time, and low-stress service environments, existing coating technologies are no longer applicable, and the entire industry is facing the dilemma of lacking anti-corrosion coating technologies for the inner walls of flow components under ultra-supercritical environments and coating preparation processes and supporting devices for the inner walls of components with large aspect ratio size characteristics. Therefore, it is necessary to develop a new type of antioxidant and corrosion-resistant coating preparation technology and process applicable to various complex-shaped workpieces such as large aspect ratios.

[0004] Coatings applied by the slurry method usually have good high-temperature resistance, can protect the base material in a high-temperature environment, and prevent oxidation, hardening, and deformation. Compared with other coating methods, the slurry method technology is relatively simple, the operation is relatively easy, the operability is strong, and it is suitable for large-scale production. If the coating is damaged during use, the slurry method coating is usually relatively easy to repair and remedy. The equipment and material costs required by the slurry method are relatively low, so it is relatively cost-effective. Summary of the Invention

[0005] Embodiments of the present disclosure aim to at least solve one of the technical problems existing in the prior art, and provide a method for preparing an antioxidant coating on the surface of a boiler pipe wall.

[0006] One aspect of an embodiment of the present disclosure provides a method for preparing an antioxidant coating on the surface of a boiler tube wall, including:

[0007] Weigh and prepare the solid-phase components and liquid-phase components in proportion, and after stirring and ball milling, prepare coating slurries with different proportions for standby;

[0008] Perform surface cleaning and preheating treatment on the workpiece to be plated, and spray the coating slurry onto the surface of the workpiece to be plated and perform drying and curing treatment;

[0009] Place the workpiece to be plated with the cured coating layer in an inert atmosphere for heat treatment, and after cooling, obtain an aluminum-silicon antioxidant coating on the surface of the workpiece to be plated, and perform surface residue treatment.

[0010] Optionally, weigh the infiltration source, filler, activator, binder and catalyst in proportion and configure the solid-phase components and liquid-phase components;

[0011] The infiltration source includes Al, Si, BC 4 powder, the filler includes SiC, the activator includes NH 4 Cl, the binder includes water glass, and the catalyst includes CrO 3 ; among them, both the Al and Si powders are sieved through a 1000-mesh sieve.

[0012] Optionally, the preparation method of the solid-phase components of the slurry includes: weighing the solid-phase components by mass percentage, including 40-80% of Al, 10-30% of Si, 5-15% of BC 4 5-15%

[0013] of SiC and 0-5% of NH 4 Cl, the total mass of the solid-phase components is 100%, and after weighing, they are ball milled and mixed by a planetary ball mill, and the ball milling speed is 350-400 rpm and the time is 6-24 h.

[0014] Optionally, the preparation method of the liquid-phase components of the slurry includes: the liquid-phase components include water glass and a 10-30% CrO 3 solution, and after proportionally preparing, they are mixed, stirred, reacted and filtered.

[0015] Optionally, the preparation method of the coating slurry includes: mixing the solid-phase components and the liquid-phase components at a solid-liquid ratio of 10 g: 4-6 ml, stirring for 2-4 h and then placing them in a planetary ball mill for ball milling and mixing, and the ball milling speed is 350-400 rpm and the time is 6-24 h to obtain a uniformly mixed coating slurry.

[0016] Optionally, the preheating treatment includes medium-frequency preheating the workpiece to be plated at 220 °C for 30-60 min.

[0017] Optionally, the slurry spraying pressure is 0.5 - 2 MPa, the thickness of the coating layer is 0.1 - 1 mm, and the coating coverage rate is not less than 98% of the surface of the workpiece to be plated.

[0018] Optionally, the drying of the slurry coating is carried out by natural air drying for 24 - 48 h, and the curing treatment is curing at 300 - 450 °C for 24 - 48 h.

[0019] Optionally, the heat treatment temperature is 980 - 1150 °C, and the inert gas for heat treatment includes Ar or N 2 ; wherein, after the heat treatment, it further includes: performing heat preservation treatment on the workpiece to be plated, and the heat preservation time is 8 - 15 min.

[0020] The beneficial effects of the embodiments of the present disclosure include:

[0021] 1. By introducing Si element to modify the aluminide antioxidant coating, the present invention improves the thermal corrosion resistance of the coating and has excellent economic benefits.

[0022] 2. By adding BC 4 to the coating slurry components, the present invention reduces the viscosity of the oxidation product SiO 2 during the oxidation process, promotes its rapid flow to cover the surface of the workpiece, and further improves its antioxidant ability.

[0023] 3. By performing heat treatment in an inert atmosphere, the present invention effectively avoids phenomena such as oxidation and hydrogen embrittlement that may occur in austenitic steel, protects the workpiece substrate while increasing the infiltration rate.

[0024] 4. By preparing the coating through the slurry coating process, the present invention is applicable to metal workpieces of various complex shapes and has strong universality.

[0025] 5. By preparing the coating through an integrated production line, the present invention has high coating production efficiency, controllable thickness, high process repeatability, and strong practicality.

[0026] Furthermore, the oxidation product B 4 during the oxidation process of BC 2 O 3 can effectively reduce the viscosity of SiO 2 , enhance its fluidity, and promote its rapid coverage of the workpiece surface to hinder the further oxidation of the workpiece.

[0027] Furthermore, the segmented slurry curing process of natural air drying combined with medium - low temperature curing effectively avoids the problems of micro - cracks and tiny holes generated in the slurry layer due to thermal stress during direct drying, and enhances the bonding strength between the slurry layer and the workpiece surface.

[0028] Furthermore, to prevent the rapid evaporation of the slurry components at high temperature, rapid heating and short - time heat preservation are used for heat treatment of the workpiece. Brief Description of the Drawings

[0029] Figure 1 Schematic flow chart of a method for preparing an antioxidant coating on the surface of a boiler tube wall according to an embodiment of the present disclosure;

[0030] Figure 2 Schematic cross-sectional structure diagram of a boiler tube wall surface with an antioxidant coating according to an embodiment of the present disclosure; wherein, the cross-section of the Al infiltration coating with a coating thickness of 24.56 μm is schematically shown in the figure. Detailed Embodiments

[0031] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below in conjunction with the drawings and specific embodiments.

[0032] The embodiments of the present application will be further described in detail below in conjunction with the drawings and embodiments. The detailed description and drawings of the following embodiments are used to exemplarily illustrate the principle of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments. In the description of the present application, it should be noted that unless otherwise specified, the meaning of "a plurality" is two or more; the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate the orientation or positional relationship only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable error range. "Parallel" is not strictly parallel, but within the allowable error range.

[0033] In the description of the present application, it should also be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0034] As Figure 1-2 shown, a method for preparing an antioxidant coating on the surface of a boiler tube wall includes:

[0035] S101. Weigh and prepare the solid-phase component and the liquid-phase component in proportion, and prepare different proportion coating slurries for standby after stirring and ball milling.

[0036] S102. Perform surface cleaning and preheating treatment on the workpiece to be plated, spray the coating slurry onto the surface of the workpiece to be plated, and perform drying and curing treatment. The workpiece to be plated is the boiler tube wall.

[0037] S103. Place the workpiece to be plated with the cured coating layer under an inert atmosphere for heat treatment. After cooling, an aluminum-silicon antioxidant coating is obtained on the surface of the workpiece to be plated, and surface residue treatment is performed. The residue treatment is carried out by flushing with a high-pressure water gun or high-pressure air flow and natural air drying.

[0038] In some embodiments, weigh the carburizing source, filler, activator, binder, and catalyst in proportion and configure the solid-phase component and the liquid-phase component.

[0039] The carburizing source includes Al, Si, BC 4 powder, the filler includes SiC, the activator includes NH 4 Cl, the binder includes water glass, and the catalyst includes CrO 3 , wherein, the Al and Si powders are both sieved through a 1000-mesh sieve.

[0040] In some embodiments, the preparation method of the solid-phase component of the slurry includes: weighing the solid-phase component by mass percentage, including 40-80% of Al, 10-30% of Si, 5-15% of BC 4 , 5-15% of SiC, and 0-5% of NH 4 Cl, the total mass of the solid-phase component is 100%. After weighing, it is ball-milled and mixed by a planetary ball mill, and the ball-milling speed is 350-400 rpm and the time is 6-24 h.

[0041] In some embodiments, the preparation method of the liquid-phase component of the slurry includes: the liquid-phase component includes water glass and a 10-30% CrO 3 solution. After proportionally dispensing, it is mixed, stirred, reacted, and filtered.

[0042] In some embodiments, the preparation method of the coating slurry includes: mixing the solid-phase component and the liquid-phase component at a solid-liquid ratio of 10 g: 4-6 ml, stirring for 2-4 h, and then placing it in a planetary ball mill for ball-milling and mixing. The ball-milling speed is 350-400 rpm and the time is 6-24 h to obtain a uniformly mixed coating slurry.

[0043] In some embodiments, the preheating treatment includes medium-frequency preheating of the workpiece to be plated at 220°C for 30-60 min.

[0044] In some embodiments, the spraying pressure of the slurry is 0.5-2 MPa, the thickness of the coating layer is 0.1-1 mm, and the coating coverage rate is not less than 98% of the surface of the workpiece to be plated.

[0045] In some embodiments, the slurry coating is dried by natural air drying for 24-48 hours, and the curing treatment is cured at 300-450° C. for 24-48 hours.

[0046] In some embodiments, the heat treatment temperature is 980-1150° C., and the inert gas for the heat treatment includes Ar or N 2 , wherein, after the heat treatment, the process also includes: performing heat preservation treatment on the workpiece to be plated, and the heat preservation time is 8-15 minutes.

[0047] An embodiment disclosed in the present invention includes:

[0048] Step 1: Weigh the solid phase components according to the mass ratio, including 40-80% Al (seepage source), 10-30% Si (seepage source), 5-15% BC 4 (source), 5-15% SiC (filler) and 0-5% NH 4 Cl (activator), wherein Al and Si powders are sieved through a 1000 mesh screen, keeping the total percentage of all solid components at 100%, and the weighed solid components are placed in a planetary ball mill at 350-400 rpm for 6-24 hours to obtain a uniformly mixed powder, which is the solid phase infiltration agent. Subsequently, water glass (binder) and 10-30% CrO are mixed according to the proportion. 3 The solution (catalyst) is fully mixed, stirred, reacted and filtered for 4-8 hours to obtain a liquid component. Finally, the solid and liquid components are mixed at a solid-liquid ratio of 10g:4-6ml, and after being fully stirred for 2-4 hours, they are placed in a planetary ball mill at 350-400rpm for 6-24 hours. After completion, a uniformly mixed slurry is obtained, which is the coating slurry.

[0049] Step 2, take out the workpiece to be plated, use a high-pressure water gun to clean the surface for 5-10 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin, and rinse it with alcohol or acetone to provide a clean and metallic surface for the subsequent coating slurry. Then, preheat the workpiece at 220℃ for 30-60 minutes, and apply the slurry to the appropriate thickness at a spray pressure of 0.5-2MPa at one time. Do not apply it in layers multiple times, keep the coating thickness at 0.1-1mm, and the coating coverage rate is not less than 98%. If the slurry layer is too thin, it is not enough to provide sufficient penetration source, and if it is too thick, it is easy to crack and peel off, affecting the uniformity of the penetration layer thickness. After coating, the workpiece is naturally air-dried for 24-48 hours, and then cured at 300-450℃ for 24-48 hours. The segmented slurry curing process of natural air drying combined with medium and low temperature curing effectively avoids the microcracks and tiny holes caused by thermal stress in the slurry layer during direct drying, and enhances the bonding strength between the slurry layer and the workpiece surface.

[0050] Step 3: To prevent the rapid evaporation of the high-temperature feedstock slurry components, the workpiece is heat-treated by rapid heating and short-time heat preservation, and then air-cooled to room temperature. The heat treatment temperature is 980 - 1150 °C, the heat preservation time is 8 - 15 min, and the inert gas is Ar or N 2 , and after the heat treatment, the surface residue of the workpiece is washed with a high-pressure water gun or high-pressure air flow and naturally air-dried.

[0051] Through the above processes and steps, a preparation method of an antioxidant coating on the surface of a boiler pipe wall according to the present invention prepares an aluminum-silicon antioxidant coating with a thickness of 19 - 40 μm and an Al atomic content of 18% - 32% showing good metallurgical bonding under the conditions of adjusting main process parameters such as the composition content of the solid-phase penetrant, the solid-liquid ratio of the slurry, the spraying pressure of the slurry, the thickness of the coating layer, and the heat treatment parameters. The aluminum-silicon coating obtained by the present invention has an antioxidant ability 17 - 61 times higher than that of the base material in a 600 °C pure water vapor environment and 19 - 74 times higher than that of the base material in a 650 °C pure water vapor environment, which shows that the aluminum-silicon antioxidant coating prepared by the method of the present invention effectively improves the antioxidant ability of the alloy base material in a water vapor environment.

[0052] The present disclosure provides the following specific embodiments:

[0053] Example 1

[0054] Step 1: Weigh the solid-phase components by mass ratio, including 50% Al, 20% Si, 10% BC 4 , 15% SiC, and 5% NH 4 Cl, place them in a planetary ball mill and ball-mill at 400 rpm for 24 h to obtain a solid-phase penetrant. Subsequently, mix water glass and a 15% CrO 3 solution in proportion, fully mix, stir, react, and filter for 8 h to obtain a liquid-phase component. Finally, mix the solid-phase and liquid-phase components at a solid-liquid ratio of 10 g:4 ml, fully stir for 4 h, and then place them in a planetary ball mill and ball-mill at 400 rpm for 24 h. After completion, a uniformly mixed slurry, i.e., the coating slurry, is obtained.

[0055] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 min, and rinse it clean with alcohol or acetone. Subsequently, preheat the workpiece at 220 °C by medium frequency for 45 min, and coat the slurry at a spraying pressure of 2 MPa to a thickness of 1 mm at one time, ensuring that the coating coverage rate is not less than 98%. Then, air-dry the workpiece naturally for 48 h and cure it at 450 °C for 48 h.

[0056] Step 3: Place the coated metal pipe under Ar for heat treatment. The heat treatment temperature is 1000 °C and the heat preservation time is 15 min. After completion, wash the surface residue of the workpiece with a high-pressure water gun or high-pressure air flow and naturally air-dry it.

[0057] The procedures of Examples 2 - 11 are the same as that of Example 1. Examples 1 - 11 maintain the same solid-phase component and liquid-phase component ratios. The specific conditions are shown in Table 1. Table 1 shows the specific parameters of Examples 1 - 11 for the preparation method of the antioxidant coating on the boiler tube wall surface. According to the preparation steps in Example 1 above and the specific preparation parameters in the table, aluminum-silicon antioxidant coatings with different thicknesses and Al atomic contents can be obtained.

[0058] Table 1

[0059]

[0060] By analyzing and studying the above examples, measuring the thickness of the infiltration layer is about 19 - 40 μm and the Al atomic content is about 18% - 32%. The specific results are shown in Table 1, and the cross-sectional morphology of the infiltration layer is as shown in the figure. Combining Table 1 and the cross-sectional morphology, it is found that the microstructure of the infiltration layer is uniform, the thickness is appropriate, the Al atoms are diffused sufficiently, the infiltration layer and the substrate show good metallurgical bonding and are not easy to fall off.

[0061] Example 12

[0062] Step 1: Weigh the solid-phase components by mass ratio, including 60% Al, 15% Si, 10% BC 4 , 10% SiC, and 5% NH 4 Cl. Place them in a planetary ball mill and ball mill at 400 rpm for 24 h to obtain the solid-phase infiltrant. Subsequently, prepare water glass and a 15% CrO 3 solution according to the ratio. After 8 h of sufficient mixing, stirring, reaction, and filtration, the liquid-phase component is obtained. Finally, mix the solid-phase and liquid-phase components at a solid-liquid ratio of 10 g:5 ml, stir well for 4 h, and then place them in a planetary ball mill and ball mill at 400 rpm for 24 h. After completion, a uniformly mixed slurry, that is, the coating slurry, is obtained.

[0063] Step 2: Use a high-pressure water gun to clean the surface of the workpiece for 5 min, and rinse it clean with alcohol or acetone. Subsequently, preheat the workpiece at 220 °C by medium frequency for 45 min, and coat the slurry at a spraying pressure of 2 MPa to a thickness of 1 mm at one time, ensuring that the coating coverage rate is not less than 98%. Then, air-dry the workpiece naturally for 48 h and cure it at 450 °C for 48 h.

[0064] Step 3: Place the coated metal pipe under Ar for heat treatment. The heat treatment temperature is 1050 °C and the holding time is 15 min. After completion, rinse the residue on the surface of the workpiece with a high-pressure water gun or high-pressure air flow and air-dry it naturally.

[0065] Example 13

[0066] Step 1: Weigh the solid-phase components by mass ratio, including 70% Al, 10% Si, 5% BC4 and 10% SiC and 5% NH 4 Cl. Place it in a planetary ball mill and ball mill at 400 rpm for 24 h to obtain a solid-phase infiltrant. Subsequently, prepare water glass and a 15% CrO 3 solution according to the proportion. After 8 h of sufficient mixing, stirring, reaction, and filtration, a liquid-phase component is obtained. Finally, mix the solid-phase and liquid-phase components at a solid-liquid ratio of 10 g:5 ml, stir well for 4 h, and then place it in a planetary ball mill and ball mill at 400 rpm for 24 h. After completion, a uniformly mixed slurry, i.e., the coating slurry, is obtained.

[0067] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 min, and rinse it clean with alcohol or acetone. Subsequently, preheat the workpiece at 220 °C by medium-frequency for 45 min, and apply the slurry at one time to a thickness of 1 mm with a spraying pressure of 2 MPa, keeping the coating coverage rate not less than 98%. Subsequently, air-dry the workpiece naturally for 48 h and cure it at 450 °C for 48 h.

[0068] Step 3: Place the coated metal pipe under Ar for heat treatment. The heat treatment temperature is 1050 °C and the holding time is 15 min. After completion, rinse the residue on the surface of the workpiece with a high-pressure water gun or high-pressure air flow and air-dry it naturally.

[0069] Example 14

[0070] Step 1: Weigh the solid-phase components by mass ratio, including 80% Al, 10% Si, 5% BC 4 and 5% SiC. Place it in a planetary ball mill and ball mill at 400 rpm for 24 h to obtain a solid-phase infiltrant. Subsequently, prepare water glass and a 15% CrO 3 solution according to the proportion. After 8 h of sufficient mixing, stirring, reaction, and filtration, a liquid-phase component is obtained. Finally, mix the solid-phase and liquid-phase components at a solid-liquid ratio of 10 g:5 ml, stir well for 4 h, and then place it in a planetary ball mill and ball mill at 400 rpm for 24 h. After completion, a uniformly mixed slurry, i.e., the coating slurry, is obtained.

[0071] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 min, and rinse it clean with alcohol or acetone. Subsequently, preheat the workpiece at 220 °C by medium-frequency for 45 min, and apply the slurry at one time to a thickness of 1 mm with a spraying pressure of 2 MPa, keeping the coating coverage rate not less than 98%. Subsequently, air-dry the workpiece naturally for 48 h and cure it at 450 °C for 48 h.

[0072] Step 3: Place the coated metal pipe under Ar for heat treatment. The heat treatment temperature is 1050 °C and the holding time is 15 min. After completion, rinse the residue on the surface of the workpiece with a high-pressure water gun or high-pressure air flow and air-dry it naturally.

[0073] Embodiment 15

[0074] Step 1: Weigh the solid phase components according to the mass ratio, including 60% Al, 15% Si, and 15% BC 4 , 5% SiC and 5% NH 4 Cl, and then placed it in a planetary ball mill at 400 rpm for 24 h to obtain a solid phase infiltration agent. Subsequently, water glass and 15% CrO 3 The solution was stirred, reacted and filtered for 8 hours to obtain a liquid phase component. Finally, the solid and liquid phase components were mixed at a solid-liquid ratio of 10 g: 5 ml, stirred for 4 hours, and then placed in a planetary ball mill at 400 rpm for 24 hours. After completion, a uniformly mixed slurry was obtained, which was the coating slurry.

[0075] Step 2: Use a high-pressure water gun to clean the surface of the workpiece for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 220°C for 45 minutes, and apply the slurry to a thickness of 1 mm at a time with a spray pressure of 2MPa, keeping the coating coverage rate not less than 98%. Then, air dry the workpiece naturally for 48 hours and cure it at 450°C for 48 hours.

[0076] Step 3: Place the coated metal pipe under Ar for heat treatment at a temperature of 1150°C and a holding time of 10 minutes. After completion, use a high-pressure water gun or high-pressure airflow to flush the residue on the workpiece surface and let it dry naturally.

[0077] Example 16

[0078] Step 1: Weigh the solid components according to the mass ratio, including 60% Al, 15% Si, and 5% BC. 4 , 15% SiC and 5% NH 4 Cl, and then placed it in a planetary ball mill at 400 rpm for 24 h to obtain a solid phase infiltration agent. Subsequently, water glass and 15% CrO 3 The solution was stirred, reacted and filtered for 8 hours to obtain a liquid phase component. Finally, the solid and liquid phase components were mixed at a solid-liquid ratio of 10 g: 5 ml, stirred for 4 hours, and then placed in a planetary ball mill at 400 rpm for 24 hours. After completion, a uniformly mixed slurry was obtained, which was the coating slurry.

[0079] Step 2: Use a high-pressure water gun to clean the surface of the workpiece for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 220°C for 45 minutes, and apply the slurry to a thickness of 1 mm at a time with a spray pressure of 2MPa, keeping the coating coverage rate not less than 98%. Then, air dry the workpiece naturally for 48 hours and cure it at 450°C for 48 hours.

[0080] Step 3: Place the coated metal pipe under Ar for heat treatment at a temperature of 1150 °C and a holding time of 15 min. After completion, rinse the residue on the surface of the workpiece with a high-pressure water gun or high-pressure air stream and air dry it naturally.

[0081] In the present invention, the antioxidant coating on the surface of the boiler tube wall and its preparation method are applicable to austenitic steel and superalloy components used in large boilers, oil and gas field transportation pipelines and other workpieces with large aspect ratios and various complex shapes. It has strong practicability, high diffusion rate, excellent film-substrate bonding force, and excellent industrial mass production benefits.

[0082] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principles of the present disclosure. However, the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also regarded as the protection scope of the present disclosure.

Claims

1. A method for preparing an anti-oxidation coating on the surface of a boiler tube wall, characterized in that: include: Weigh the solid phase components and liquid phase components in proportion, and prepare coating slurries of different proportions after stirring and ball milling for use; The workpiece to be plated is cleaned and preheated, and the coating slurry is sprayed onto the surface of the workpiece to be plated and dried and cured; The workpiece to be plated after the coating layer is solidified is placed in an inert atmosphere for heat treatment, and after cooling, an aluminum-silicon anti-oxidation coating is obtained on the surface of the workpiece to be plated, and surface residue treatment is performed.

2. The method for preparing an anti-oxidation coating on a boiler tube wall surface according to claim 1, characterized in that: Weigh the infiltration source, filler, activator, binder and catalyst in proportion and prepare the solid phase component and the liquid phase component; The infiltration source includes Al, Si, and BC4 powders, the filler includes SiC, the activator includes NH4Cl, the binder includes water glass, and the catalyst includes CrO3; wherein the Al and Si powders are sieved through a 1000-mesh sieve.

3. The method for preparing an anti-oxidation coating on the surface of a boiler tube wall according to claim 2, characterized in that: The preparation method of the slurry solid phase component includes: weighing the solid phase components according to mass percentage, including 40-80% Al, 10-30% Si, 5-15% BC4, 5-15% SiC and 0-5% NH4Cl, the total mass of the solid phase components is 100%, and then mixing them by ball milling in a planetary ball mill, the ball milling speed is 350-400rpm, and the time is 6-24h.

4. The method for preparing an anti-oxidation coating on the surface of a boiler tube wall according to claim 2, characterized in that: The method for preparing the slurry liquid phase component comprises: the liquid phase component comprises water glass and 10-30% CrO3 solution, which are mixed, stirred, reacted and filtered after being mixed according to a certain proportion.

5. The method for preparing an anti-oxidation coating on the surface of a boiler tube wall according to claim 1, characterized in that: The coating slurry preparation method includes: mixing solid phase components and liquid phase components at a solid-liquid ratio of 10g:4-6ml, stirring for 2-4h, and then placing in a planetary ball mill for ball milling, the ball milling speed is 350-400rpm, the time is 6-24h, to obtain a uniformly mixed coating slurry.

6. The method for preparing an anti-oxidation coating on the surface of a boiler tube wall according to claim 1, characterized in that: The preheating treatment includes medium frequency preheating the workpiece to be plated at 220°C for 30-60 minutes.

7. The method for preparing an anti-oxidation coating on the surface of a boiler tube wall according to claim 1, characterized in that: The slurry spraying pressure is 0.5-2MPa, the coating layer thickness is 0.1-1mm, and the coating coverage is not less than 98% of the surface of the workpiece to be plated.

8. The method for preparing an anti-oxidation coating on the surface of a boiler tube wall according to claim 1, characterized in that: The slurry coating is dried by natural air drying for 24-48 hours, and the curing treatment is cured at 300-450°C for 24-48 hours.

9. The method for preparing an anti-oxidation coating on a boiler tube wall surface according to claim 1, characterized in that: The heat treatment temperature is 980-1150°C, and the inert gas for the heat treatment includes Ar or N2; wherein, after the heat treatment, the heat treatment also includes: heat preservation treatment of the workpiece to be plated, and the heat preservation time is 8-15 minutes.

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