A method for improving the corrosion resistance of aluminide cladding coatings

Abstract

This disclosure proposes a method for improving the corrosion resistance of aluminum compound cladding coatings, belonging to the field of material surface alloying and coating preparation technology. The method includes: mixing solid-phase cladding powder and liquid-phase binder, followed by stirring and ball milling to obtain a cladding slurry; cleaning and preheating the surface of the workpiece to be plated; spraying the cladding slurry onto the surface of the workpiece, followed by drying and curing to form a pre-coated layer on the workpiece surface; and placing the workpiece with the pre-coated layer under an inert atmosphere for laser cladding treatment, followed by cooling to obtain the aluminum compound cladding coating. This disclosure achieves a thicker coating by first mixing solid-phase cladding powder and liquid-phase binder, spraying it onto the workpiece surface, and then using a laser cladding process, effectively increasing the corrosion resistance of the coating. This process has high repeatability and strong practicality and universality.

Description

Technical Field

[0001] This disclosure belongs to the field of material surface alloying and coating preparation technology, specifically relating to a method for improving the corrosion resistance of aluminide cladding coatings. Background Technology

[0002] Laser cladding technology, a novel surface modification technology that emerged in the 1970s with the development of high-power lasers, refers to a surface strengthening method in which alloy powder or ceramic powder is rapidly heated and melted with the substrate surface under the action of a laser beam. After cooling, a metallurgically bonded surface coating is formed on the substrate surface, thereby significantly improving the wear resistance, corrosion resistance, oxidation resistance and other properties of the substrate surface.

[0003] Laser cladding technology is widely used in the preparation of coating materials due to its advantages such as rapid cooling, low coating dilution rate, and minimal part distortion. The coatings produced by laser cladding exhibit uniform and dense structure and strong adhesion to the substrate. In particular, laser cladding technology has virtually no restrictions on powder selection, allowing the use of various metal powders to meet specific application requirements.

[0004] Al powder, as a coating material, possesses high corrosion resistance, making aluminum profile powder coatings superior to traditional coatings in terms of corrosion resistance. This effectively protects the aluminum profile surface from various corrosive substances such as acids, alkalis, salts, and oils. Secondly, aluminum profile powder coatings have higher hardness than traditional coatings, effectively improving the surface strength and wear resistance of aluminum profiles. Furthermore, aluminum profile powder coatings do not contain organic solvents and do not produce volatile organic compounds, meeting environmental protection requirements.

[0005] In current laser cladding processes, various metal powders are simultaneously clad onto the workpiece surface. The resulting Al coating is relatively thin, only a few micrometers or tens of micrometers thick, and the adhesion between the coating and the substrate is weak. While this may appropriately extend the service life of the pipe in the early stages of use, the coating still peels off due to continuous corrosion from soot and water vapor, resulting in poor coating quality. Therefore, to improve the corrosion resistance of the coating, further improvements are urgently needed to meet the requirements of long-term pipeline use and reduced thermal power costs. Summary of the Invention

[0006] This disclosure aims to at least address one of the technical problems of short service life and limited lifespan of aluminum coatings in existing thermal power pipelines, and provides a method to improve the corrosion resistance of aluminum compound cladding coatings.

[0007] This disclosure proposes a method for improving the corrosion resistance of aluminum compound cladding coatings, wherein...

[0008] The methods include:

[0009] Solid-phase cladding powder and liquid-phase binder are mixed, stirred, and ball-milled to obtain cladding slurry;

[0010] The workpiece to be plated is surface cleaned and preheated.

[0011] The cladding slurry is sprayed onto the surface of the workpiece to be plated, and then dried and cured to form a pre-coated layer on the workpiece surface.

[0012] The workpiece with a pre-coated coating is placed in an inert atmosphere for laser cladding treatment, and after cooling, an aluminide cladding coating is obtained.

[0013] Optionally, the solid phase cladding powder includes an aluminum infiltration source, a modifier, and an activator.

[0014] Optionally, the aluminum diffusion source is NiAl and Al.

[0015] Optionally, the modifier is Si and Pt.

[0016] Optionally, the activator is NH4Cl.

[0017] Optionally, the NiAl content is 50-70%;

[0018] The Al content is 15-40%;

[0019] The Si content is 0-5%;

[0020] The Pt content is 0-5%;

[0021] The NH4Cl content is 0-5%.

[0022] Optionally, the liquid phase binder is any one of ethyl acetate, polyvinyl alcohol, sodium carboxymethyl cellulose, and nitrocellulose.

[0023] Optionally, the content of the liquid phase binder is 10-30% of the mass of the solid phase cladding powder.

[0024] Optionally, in laser cladding, the laser power is 2-2.8KW, the scanning rate is 20-40mm / s, the spot diameter is 2-5mm, the workpiece rotation speed is 0-5r / min, and the Ar gas flow rate is 15-20L / min.

[0025] Optionally, the thickness of the sprayed coating is 1-5 mm;

[0026] The thickness of the aluminide cladding coating is 1.15-2.95 mm.

[0027] This disclosure proposes a method for improving the corrosion resistance of aluminum compound cladding coatings. The method includes: mixing solid-phase cladding powder and liquid-phase binder, followed by stirring and ball milling to obtain a cladding slurry; cleaning and preheating the surface of the workpiece to be plated; spraying the cladding slurry onto the surface of the workpiece, followed by drying and curing to form a pre-coated layer on the workpiece surface; and placing the workpiece with the pre-coated layer under an inert atmosphere for laser cladding treatment, followed by cooling to obtain the aluminum compound cladding coating. This disclosure achieves the preparation of a thicker coating by first mixing solid-phase cladding powder and liquid-phase binder, spraying it onto the workpiece surface, and then using a laser cladding process, effectively increasing the corrosion resistance of the coating. This process has high repeatability and strong practicality and universality. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating a method for improving the corrosion resistance of an aluminide cladding coating according to an embodiment of the present disclosure.

[0029] Figure 2 This is a cross-sectional morphology diagram of the aluminide cladding coating in Embodiment 4 of this disclosure; wherein, Figure 2 (A) in the figure is a cross-sectional topography of the coating; Figure 2 (B) in the image is a magnified view of (A). Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining this disclosure and are not intended to limit the disclosure. The described embodiments are some, but not all, of the embodiments of this disclosure. Based on the described embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this disclosure.

[0031] like Figure 1 As shown, this disclosure proposes a method S100 for improving the corrosion resistance of aluminide cladding coatings, comprising the following specific steps S110 to S140:

[0032] S110. The solid phase cladding powder and liquid phase binder are mixed, and then stirred and ball-milled to obtain the cladding slurry.

[0033] Specifically, the components of the solid-phase cladding powder are sieved through a 1000-mesh sieve, and then the components are ball-milled in a planetary ball mill at a speed of 350-400 rpm for 12-24 hours. Afterward, the mixed solid-phase cladding powder is mixed with a liquid-phase binder and stirred thoroughly for 2-4 hours, then ball-milled again in a planetary ball mill at a speed of 350-400 rpm for 8-12 hours to obtain the cladding slurry. In other words, the solid-phase cladding powder is first pre-mixed by ball milling, and then the solid-phase cladding powder and liquid-phase binder are ball-milled.

[0034] In some preferred embodiments, the solid phase cladding powder is an aluminum infiltration source, a modifier, and an activator. Of course, the total percentage content of each component in the solid phase cladding powder is 100%.

[0035] As a further preferred embodiment, the aluminum source is NiAl and Al, with NiAl content being 50-70% and Al content being 15-40% by mass percentage. For example, the NiAl content is preferably 50%, 55%, 60%, 65%, or 70%, and the Al content is preferably 15%, 20%, 25%, 30%, 35%, or 40%.

[0036] In this embodiment, NiAl is used as one of the components of the aluminum diffusion source, which can form an active intermediate AlCl with NH4Cl. x This promotes the generation of active aluminum atoms and their penetration into the matrix. Secondly, the component can be directly clad into the diffusion layer, improving its wear resistance and corrosion resistance. Furthermore, the component can inhibit the generation of brittle aluminum-rich phases such as NiAl3 and Ni2Al3 in the diffusion layer, thereby enhancing the wear resistance of the coating and extending the service life of the pipe.

[0037] As a further preferred embodiment, the modifier is Si and Pt, wherein the Si content is 0-5% by mass percentage, and the Pt content is preferably 0-5%. That is, in some preferred embodiments, the solid-phase cladding powder may not include the modifier, may only include the Si component, may only include the Pt component, or may include both Si and Pt components.

[0038] As a further preferred embodiment, the Si content is preferably 1%, 2%, 3%, 4%, or 5%, and the Pt content is preferably 1%, 2%, 3%, 4%, or 5%.

[0039] In this embodiment, the solid-phase cladding powder not only contains metal powder but also includes modifying elements. The addition of Si (Si) can form a continuous SiO2 passivation film, improving oxidation resistance and heat corrosion resistance. The addition of Pt (Pt) can provide channels for Al, forming a dense oxide layer, inhibiting or reducing the outward diffusion of alloying elements, accelerating the transformation of θ-Al2O3 to α-Al2O3, improving film-substrate adhesion, effectively inhibiting internal oxidation and internal sulfidation, and enhancing the coating's heat corrosion resistance.

[0040] As a further preferred embodiment, the activator is NH4Cl, and the content of NH4Cl is 0-5% by mass percentage, for example, 1%, 2%, 3%, 4%, 5%. That is, in some preferred embodiments, the solid phase cladding powder may not include an activator.

[0041] It should be understood that when halides NH4Cl are added to solid cladding powder, the component can play a role in promoting penetration and activation, thereby improving the penetration rate and coating quality.

[0042] In some preferred embodiments, the liquid phase binder is ethyl acetate. Of course, the liquid phase binder can also be other high-temperature organic binders, such as polyvinyl alcohol, sodium carboxymethyl cellulose aqueous solution, nitrocellulose binder, etc. This liquid phase binder component can form a slurry of metal powder that adheres to the substrate surface, and after drying and curing, forms a more uniform and dense coating layer. Simultaneously, it can prevent the metal powder from adhering to each other and forming metal sintered products, which would lead to uneven diffusion layers. Furthermore, other liquid phase binders such as ethyl acetate volatilize during laser cladding and will not affect the process.

[0043] As a further preferred embodiment, the content of the liquid phase binder is 10-30% of the mass of the solid phase cladding powder, for example, 10%, 15%, 20%, 25%, 30%.

[0044] S120. Perform surface cleaning and preheating treatment on the workpiece to be plated.

[0045] Specifically, the workpiece to be plated is cleaned with a high-pressure water gun for 5-10 minutes to remove oil stains, dirt, and oxide scale from the surface. Simultaneously, the workpiece can be rinsed with alcohol or acetone to provide a clean, metallic-luster surface for subsequent slurry spraying. Afterward, the workpiece is preheated at 200-250℃ using medium-frequency induction heating for 30-60 minutes.

[0046] S130. Spray the cladding slurry onto the surface of the workpiece to be plated, and dry and cure it to form a pre-coated layer on the surface of the workpiece.

[0047] Specifically, the cladding slurry obtained in step S110 is sprayed onto the surface of the workpiece after the treatment in step S120 in one go, and then air-dried for 24-48 hours. After that, it is cured at 300-450℃ for 24-48 hours to obtain a pre-sprayed coating on the surface of the workpiece. The thickness of the pre-sprayed coating is 1-5mm and the coating coverage is not less than 98%. If the slurry layer is too thin, it will not provide sufficient penetration source. If it is too thick, it will easily crack and peel off, affecting the uniformity of the penetration layer thickness.

[0048] It should be understood that this embodiment involves spraying the slurry to a suitable thickness in one go, and multiple layers of spraying are not allowed.

[0049] In this embodiment, the segmented slurry curing process combining natural air drying and low-temperature curing effectively avoids the microcracks and micropores 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] S140. The workpiece with the pre-coated coating is placed in an inert atmosphere for laser cladding treatment, and after cooling, an aluminide cladding coating is obtained.

[0051] In some preferred embodiments, during laser cladding, the laser power is 2-2.8KW, the scanning rate is 20-40mm / s, the spot diameter is 2-5mm, the workpiece rotation speed is 0-5r / min, and the Ar gas flow rate is 15-20L / min.

[0052] It should be understood that after obtaining the aluminide cladding coating, the residue on the workpiece surface should be treated, for example, by using a high-pressure water gun or high-pressure airflow to rinse the residue on the workpiece surface and then air-drying it naturally.

[0053] In some other preferred embodiments, the thickness of the resulting aluminide cladding coating is 1.15-2.95 mm.

[0054] The method described in this embodiment is applicable to the preparation of anti-oxidation coatings for austenitic steel and high-temperature alloy components used in large boilers, oil and gas field pipelines, and other workpieces with large length-to-diameter ratios and various complex shapes.

[0055] In this embodiment, a thicker aluminide cladding coating can be obtained by combining laser cladding with aluminizing. This process has concentrated heat, short action time, small heat-affected zone, high bonding strength between the coating and the base material, high coating production efficiency, controllable thickness, and high process repeatability, making it highly practical and universal.

[0056] In this embodiment, by adjusting the main process parameters such as the content of solid cladding components, the content of modifiers, the thickness of the sprayed coating, and the laser cladding parameters, an aluminum compound cladding coating with a thickness of 1.15-2.95 mm and good metallurgical bonding with the substrate was prepared. The obtained aluminum compound cladding coating showed an oxidation resistance 19-65 times higher than the base material in a 600℃ pure water vapor environment and a oxidation resistance 20-78 times higher than the base material in a 650℃ pure water vapor environment. This indicates that the aluminum compound cladding coating prepared by this method effectively improves the oxidation resistance of the alloy base material in a water vapor environment.

[0057] The following will further illustrate the method for improving the corrosion resistance of aluminide cladding coatings with several specific examples:

[0058] Example 1

[0059] Step 1: Weigh the solid components according to the mass ratio, including 50% NiAl, 40% Al, 2% NH4Cl, 4% Si and 4% Pt, and place them in a planetary ball mill and ball mill at 400 rpm for 12 hours to obtain solid cladding powder; then, add 10% ethyl acetate and stir thoroughly for 4 hours, and place it in a planetary ball mill and ball mill at 400 rpm for 12 hours. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0060] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 250°C with medium frequency for 45 minutes, and apply a pre-formulated slurry layer with a thickness of 3 mm by spraying, maintaining a coating coverage of no less than 98%. Then, allow the workpiece to air dry naturally for 48 hours and cure it at 450°C for 48 hours.

[0061] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2KW, the scanning rate is 40mm / s, the spot diameter is 5mm, the workpiece rotation speed is 5r / min, and the Ar gas flow rate is 20L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure gas to remove residue, and obtain an aluminide cladding coating with a thickness of 2.35mm, as shown in Table 1.

[0062] Example 2

[0063] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in the laser processing parameters in step 3 is changed to 2.8KW. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 2.45mm, as shown in Table 1.

[0064] Example 3

[0065] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in step 3 is changed to 2.8KW, the scanning rate is 20mm / s, the Ar gas flow rate is 15L / min, and the rotation speed is 4r / min. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 2.18mm, as shown in Table 1.

[0066] Example 4

[0067] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in step 3 is changed to 2.8KW, the scanning rate is 20mm / s, the spot diameter is 2mm, and the Ar gas flow rate is 15L / min. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 1.15mm, as shown in Table 1.

[0068] like Figure 2 As shown, based on the cross-sectional morphology, the infiltrated layer has a uniform structure, moderate thickness, and sufficient Al atom diffusion. The infiltrated layer and the matrix have a good metallurgical bond and are not easy to fall off.

[0069] Example 5

[0070] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in step 3 is changed to 2.5KW, the scanning rate is 30mm / s, the spot diameter is 2mm, the Ar gas flow rate is 18L / min, and the rotation speed is 2r / min. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 1.54mm, as shown in Table 1.

[0071] Example 6

[0072] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in step 3 is changed to 2.4KW, the scanning rate is 25mm / s, the spot diameter is 2mm, the Ar gas flow rate is 15L / min, and the rotation speed is 2r / min. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 2.32mm, as shown in Table 1.

[0073] Example 7

[0074] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in step 3 is changed to 2.8KW, the scanning rate is 35mm / s, and the spot diameter is 3mm. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 2.41mm, as shown in Table 1.

[0075] Example 8

[0076] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in step 3 is changed to 2.6KW, the scanning rate is 25mm / s, the spot diameter is 3mm, the Ar gas flow rate is 18L / min, and the rotation speed is 4r / min. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 2.37mm, as shown in Table 1.

[0077] Example 9

[0078] The steps in this example are the same as in Example 1, keeping the same ratio of solid phase cladding powder and liquid phase binder. The difference is that the laser power in step 3 is changed to 2.8KW, the spot diameter is 4mm, and the rotation speed is 4r / min. After processing, the thickness of the aluminide cladding coating formed on the workpiece surface is 2.68mm, as shown in Table 1.

[0079] In summary, as shown in Examples 1-9, the thickness of the infiltration layer is approximately 1.15-2.95 mm, and more preferably, the thickness of the infiltration layer is greater than 2 mm, which is much higher than the current coating thickness and meets the long-term application requirements of the pipe.

[0080] Table 1. Laser cladding process parameters and coating thicknesses for Examples 1-9

[0081]

[0082]

[0083] Example 10

[0084] Step 1: Weigh the solid components according to the mass ratio, including 70% NiAl, 15% Al, 5% NH4Cl, 5% Si and 5% Pt, and place them in a planetary ball mill at 350 rpm for 24 h to obtain solid cladding powder; then, add 30% ethyl acetate and stir thoroughly for 2 h, and place it in a planetary ball mill at 400 rpm for 12 h. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0085] Step 2: Clean the workpiece surface with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 200℃ for 60 minutes using medium frequency. Apply a pre-applied slurry layer with a thickness of 5 mm using spraying, ensuring the coating coverage is not less than 98%. After that, allow the workpiece to air dry naturally for 24 hours and then cure it at 300℃ for 48 hours.

[0086] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2.5KW, the scanning rate is 20mm / s, the spot diameter is 2mm, the workpiece rotation speed is 5r / min, and the Ar gas flow rate is 15L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure gas to remove residue. The thickness of the aluminide cladding coating formed on the workpiece surface is 1.65mm, as shown in Table 2.

[0087] Example 11

[0088] Step 1: Weigh the solid components according to the mass ratio, including 50% NiAl, 40% Al, 5% NH4Cl and 5% Pt, and place them in a planetary ball mill at 400 rpm for 24 hours to obtain solid cladding powder; then, add 20% ethyl acetate and stir thoroughly for 2 hours, and place it in a planetary ball mill at 350 rpm for 8 hours. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0089] Step 2: Clean the workpiece surface with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 250°C with medium frequency for 30 minutes, and apply a pre-formulated slurry layer with a thickness of 2 mm by spraying, maintaining a coating coverage of no less than 98%. Then, allow the workpiece to air dry naturally for 24 hours and cure it at 450°C for 48 hours.

[0090] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2.8KW, the scanning rate is 40mm / s, the spot diameter is 3mm, the workpiece rotation speed is 2r / min, and the Ar gas flow rate is 15L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure airflow to remove any residue. The thickness of the aluminide cladding coating formed on the workpiece surface is 2.36mm, as shown in Table 2.

[0091] Example 12

[0092] Step 1: Weigh the solid components according to the mass ratio, including 50% NiAl, 40% Al, 5% NH4Cl and 5% Si, and place them in a planetary ball mill at 400 rpm for 12 hours to obtain solid cladding powder; then, add 20% ethyl acetate and stir thoroughly for 2 hours, and place it in a planetary ball mill at 350 rpm for 12 hours. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0093] Step 2: Clean the workpiece surface with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 200℃ for 60 minutes using medium frequency. Apply a pre-applied slurry layer with a thickness of 5 mm using spraying, ensuring the coating coverage is not less than 98%. After that, allow the workpiece to air dry naturally for 24 hours and then cure it at 400℃ for 48 hours.

[0094] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2.8KW, the scanning rate is 20mm / s, the spot diameter is 3mm, the workpiece rotation speed is 5r / min, and the Ar gas flow rate is 15L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure airflow to remove any residue. The thickness of the aluminide cladding coating formed on the workpiece surface is 2.43mm, as shown in Table 2.

[0095] Example 13

[0096] Step 1: Weigh the solid components according to the mass ratio, including 60% NiAl, 30% Al, 5% Si and 5% Pt, and place them in a planetary ball mill and ball mill at 400 rpm for 24 hours to obtain solid cladding powder; then, add 30% ethyl acetate and stir thoroughly for 2 hours, and place it in a planetary ball mill and ball mill at 400 rpm for 12 hours. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0097] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 250°C with medium frequency for 45 minutes, and apply a pre-formulated slurry layer with a thickness of 5 mm by spraying, ensuring that the coating coverage is not less than 98%. After that, let the workpiece air dry naturally for 24 hours, and then cure it at 450°C for 48 hours.

[0098] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2KW, the scanning rate is 30mm / s, the spot diameter is 5mm, the workpiece rotation speed is 5r / min, and the Ar gas flow rate is 18L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure airflow to remove residue. The thickness of the aluminide cladding coating formed on the workpiece surface is 2.40mm, as shown in Table 2.

[0099] Example 14

[0100] Step 1: Weigh the solid components according to the mass ratio, including 65% NiAl, 25% Al, 2% NH4Cl, 4% Si and 4% Pt, and place them in a planetary ball mill at 350 rpm for 12 hours to obtain solid cladding powder; then, add 30% ethyl acetate and stir thoroughly for 4 hours, and place it in a planetary ball mill at 400 rpm for 8 hours. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0101] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 250°C with medium frequency for 60 minutes, and apply a pre-formulated slurry layer with a thickness of 4 mm by spraying, maintaining a coating coverage of no less than 98%. Then, allow the workpiece to air dry naturally for 36 hours and cure it at 450°C for 48 hours.

[0102] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2.8KW, the scanning rate is 40mm / s, the spot diameter is 5mm, the workpiece rotation speed is 4r / min, and the Ar gas flow rate is 20L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure airflow to remove any residue. The thickness of the aluminide cladding coating formed on the workpiece surface is 2.42mm, as shown in Table 2.

[0103] Example 15

[0104] Step 1: Weigh the solid components according to the mass ratio, including 65% NiAl, 25% Al, 4% NH4Cl, 2% Si and 4% Pt, and place them in a planetary ball mill at 350 rpm for 24 h to obtain solid cladding powder; then, add 20% ethyl acetate and stir thoroughly for 4 h, and place it in a planetary ball mill at 400 rpm for 8 h. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0105] Step 2: Clean the workpiece surface with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 250°C with medium frequency for 60 minutes, and apply a pre-formulated slurry layer with a thickness of 5 mm by spraying, maintaining a coating coverage of no less than 98%. Then, allow the workpiece to air dry naturally for 48 hours and cure it at 450°C for 48 hours.

[0106] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2.8KW, the scanning rate is 40mm / s, the spot diameter is 4mm, the workpiece rotation speed is 4r / min, and the Ar gas flow rate is 15L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure airflow to remove any residue. The thickness of the aluminide cladding coating formed on the workpiece surface is 2.73mm, as shown in Table 2.

[0107] Example 16

[0108] Step 1: Weigh the solid components according to the mass ratio, including 65% NiAl, 30% Al, 1% NH4Cl, 2% Si and 2% Pt, and place them in a planetary ball mill and ball mill at 400 rpm for 24 hours to obtain solid cladding powder; then, add 30% ethyl acetate and stir thoroughly for 4 hours, and place it in a planetary ball mill and ball mill at 400 rpm for 8 hours. After completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0109] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and rinse it with alcohol or acetone. Then, preheat the workpiece at 250°C with medium frequency for 60 minutes, and apply a pre-formulated slurry layer with a thickness of 5 mm by spraying, maintaining a coating coverage of no less than 98%. Then, allow the workpiece to air dry naturally for 24 hours and cure it at 450°C for 48 hours.

[0110] Step 3: Place the workpiece under Ar for laser cladding. The laser power is 2.8KW, the scanning rate is 35mm / s, the spot diameter is 4mm, the workpiece rotation speed is 2r / min, and the Ar gas flow rate is 18L / min. After completion, cool to room temperature and rinse the workpiece surface with high-pressure airflow to remove residue. The thickness of the aluminide cladding coating formed on the workpiece surface is 2.77mm, as shown in Table 2.

[0111] In summary, as shown in Examples 10-16, changing the ratio of solid cladding powder results in a coating thickness of more than 2 mm. This indicates that when the components of the solid cladding powder are within the above-mentioned ratio range and the laser cladding process parameters are also within the range given above, the coating thickness is mostly more than 2 mm, effectively improving the service life of the pipe.

[0112] Table 2. Laser cladding process parameters and coating thicknesses for Examples 10-16

[0113]

[0114] This disclosure proposes a method for improving the corrosion resistance of aluminide cladding coatings, which has the following advantages compared to the prior art:

[0115] First, this disclosure achieves the effects of promoting penetration and activation by adding halide NH4Cl to the slurry components, thereby improving the penetration rate and coating quality.

[0116] Secondly, by introducing modifying elements Si and Pt into solid powder, this disclosure can accelerate the oxide film transformation process and form a sparingly soluble silica protective layer, thereby enhancing the coating's resistance to oxidation and corrosion.

[0117] Third, this disclosure uses laser cladding process to prepare coatings, which has concentrated heat, short action time, small heat-affected zone in cladding area, and high bonding strength between coating and base material.

[0118] Fourth, the present invention prepares coatings through an integrated laser cladding process production line, which has high coating production efficiency, controllable thickness, and high process repeatability, and has strong practicality and universality.

[0119] Fifth, the method disclosed herein is applicable to austenitic steel and high-temperature alloy components used in large boilers, oil and gas field pipelines, and other workpieces with large length-to-diameter ratios and various complex shapes. It is highly practical, has a high diffusion rate, excellent membrane-substrate adhesion, and excellent benefits for industrial mass production.

[0120] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method of improving the corrosion resistance of an aluminide overlay coating, characterized by, The method comprises the following steps: Mixing solid phase cladding powder and liquid phase binder, stirring, ball milling to obtain cladding slurry; the solid phase cladding powder comprises aluminum source, modifier and activator, the aluminum source is NiAl and Al, the modifier is Si and Pt, and the activator is NH4C; Carrying out surface cleaning and preheating treatment on the workpiece to be plated; Spraying the cladding slurry to the surface of the workpiece to be plated, drying and curing to form a preset spraying layer on the surface of the workpiece; Placing the workpiece with the preset spraying layer in an inert atmosphere to carry out laser cladding treatment, and obtaining an aluminide cladding coating after cooling; in the laser cladding treatment, the laser power is 2-2.8KW, the scanning speed is 20-40mm / s, the spot diameter is 2-5mm, the workpiece rotation speed is 0-5r / min, and the Ar gas flow is 15-20L / min; The thickness of the aluminide cladding coating is 1.15-2.95mm.

2. The method of claim 1, wherein, The content of NiAl is 50-70%; The content of Al is 15-40%; The content of Si is 0-5%; The content of Pt is 0-5%; The content of NH4C is 0-5%.

3. The method of claim 1, wherein, The liquid phase binder is any one of ethyl acetate, polyvinyl alcohol, sodium carboxymethyl cellulose and nitrocellulose.

4. The method of claim 3, wherein, The content of the liquid phase binder is 10-30% of the mass of the solid phase cladding powder.

5. The method of claim 1, wherein, The thickness of the spraying layer is 1-5mm.

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