Method for improving corrosion resistance of aluminide cladding coating

Abstract

The present invention relates to the technical field of material surface alloying and coating preparation. Disclosed is a method for improving the corrosion resistance of an aluminide cladding coating. The method comprises: S110, mixing a solid-phase cladding powder and a liquid-phase binder, and stirring and ball-milling same to obtain a cladding slurry; S120, cleaning and preheating the surface of the workpiece to be plated; S130, spraying the cladding slurry onto the surface of the workpiece to be plated, drying and curing same to form a preset spray coating on the surface of the workpiece; and S140, placing the workpiece having the preset spray coating in an inert atmosphere for laser cladding treatment, and cooling same to obtain the aluminide cladding coating. In the method, the solid-phase cladding powder and the liquid-phase binder are first mixed and sprayed onto the surface of the workpiece, and then a relatively thick coating can be prepared by means of a laser cladding process, thereby effectively improving the corrosion resistance of the coating. The process has high repeatability, and has strong practicability and universality.

Description

Method for improving corrosion resistance of aluminide cladding coating

[0001] Cross-reference to related applications

[0002] This application claims priority to the Chinese patent application No. 202410975830.X, filed on July 19, 2024, and entitled "A method for improving corrosion resistance of aluminide cladding coating", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure belongs to the technical field of material surface alloying and coating preparation, and particularly relates to a method for improving corrosion resistance of aluminide cladding coating. BACKGROUND

[0004] Laser cladding technology, as a new type of surface modification technology that emerged in the 1970s with the development of high-power lasers, is a surface strengthening method that rapidly heats and melts alloy powder or ceramic powder and the surface of the substrate under the action of a laser beam, and forms a metallurgical bonded surface coating on the substrate surface after cooling, thereby significantly improving the wear resistance, corrosion resistance, oxidation resistance and other properties of the substrate surface.

[0005] Due to the advantages of laser cladding technology such as fast cooling speed, low coating dilution rate, and small part distortion, the coating prepared by laser cladding technology has the characteristics of uniform and dense organization, strong bonding force with the substrate, etc., and is widely used in the preparation of coating materials. In particular, laser cladding technology has almost no restrictions on powder selection, so various metal powders can be used to meet the use requirements.

[0006] As a coating material, Al powder has high corrosion resistance, making the corrosion resistance of aluminum profile powder coating more excellent than that of traditional coatings, and effectively protecting the surface of aluminum profiles from corrosion by various corrosive substances such as acid, alkali, salt, and oil. Secondly, the hardness of aluminum profile powder coating is higher than that of traditional coatings, which can effectively improve the strength and wear resistance of the surface of aluminum profiles. Furthermore, aluminum profile powder coating does not contain organic solvents and does not produce volatile organic compounds, meeting environmental protection requirements.

[0007] In the current laser cladding process, various metal powders are usually simultaneously cladded on the surface of the workpiece. The prepared Al coating is relatively thin, only a few microns or tens of microns thick, and the bonding force between the coating and the substrate is weak. Although it can appropriately improve the service life of the pipe in the early stage of use, the coating will still fall off with the continuous corrosion of coal smoke and water vapor, and the coating quality is poor. Therefore, in order to improve the corrosion resistance of the coating, it is urgent to further improve this kind of coating to meet the requirements of long-term use of the pipeline and reduce the cost of thermal power.

[0008] SUMMARY

[0009] The present disclosure aims to at least solve one of the technical problems of short service life of existing thermal power pipelines and limited service life of aluminum coating, and provide a method for improving the corrosion resistance of aluminide cladding coating.

[0010] The present disclosure provides a method for improving the corrosion resistance of aluminide cladding coating, which comprises:

[0011] Mixing the solid-phase cladding powder and the liquid-phase binder, and performing stirring and ball milling to obtain cladding slurry;

[0012] Performing surface cleaning and preheating treatment on the workpiece to be plated;

[0013] Spraying the cladding slurry to the surface of the workpiece to be plated, and performing drying and solidification treatment to form a pre-sprayed layer on the surface of the workpiece;

[0014] Placing the workpiece with the pre-sprayed layer in an inert atmosphere to perform laser cladding treatment, and obtaining an aluminide cladding coating after cooling.

[0015] Optionally, the solid-phase cladding powder comprises aluminum penetrant, modifier and activator.

[0016] Optionally, the aluminum penetrant is NiAl and Al.

[0017] Optionally, the modifier is Si and Pt.

[0018] Optionally, the activator is NH4Cl.

[0019] Optionally, the content of NiAl is 50-70%.

[0020] The content of Al is 15-40%.

[0021] The content of Si is 0-5%.

[0022] The content of Pt is 0-5%.

[0023] The content of NH4Cl is 0-5%.

[0024] Optionally, the liquid-phase binder is any one of ethyl acetate, polyvinyl alcohol, sodium carboxymethyl cellulose and nitrocellulose.

[0025] Optionally, the content of the liquid-phase binder is 10-30% of the mass of the solid-phase cladding powder.

[0026] Optionally, 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 rate is 15-20L / min.

[0027] Optionally, the thickness of the sprayed layer is 1-5 mm.

[0028] The thickness of the aluminide cladding coating is 1.15-2.95 mm.

[0029] The present disclosure provides a method for improving the corrosion resistance of an aluminide cladding coating, which comprises the following steps: mixing solid-phase cladding powder and liquid-phase binder, stirring and ball-milling to obtain cladding slurry; performing surface cleaning and preheating treatment on a workpiece to be plated; spraying the cladding slurry onto the surface of the workpiece to be plated and performing drying and solidification treatment to form a pre-sprayed layer on the surface of the workpiece; placing the workpiece with the pre-sprayed layer in an inert atmosphere and performing laser cladding treatment, and obtaining the aluminide cladding coating after cooling. The present disclosure can realize the preparation of a relatively thick coating and effectively increase the corrosion resistance of the coating by first mixing solid-phase cladding powder and liquid-phase binder, then spraying the mixture onto the surface of a workpiece, and finally using a laser cladding process. The process has high repeatability, strong practicability and universality. BRIEF DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is a flow block diagram of the method for improving the corrosion resistance of an aluminide cladding coating according to an embodiment of the present disclosure;

[0031] FIG. 2 is a cross-sectional morphology diagram of the aluminide cladding coating according to Embodiment 4 of the present disclosure; wherein (A) in FIG. 2 is a cross-sectional morphology diagram of the coating, and (B) in FIG. 2 is a local enlarged view of (A). DETAILED DESCRIPTION

[0032] To make the skilled in the art better understand the technical solutions of the present disclosure, the present disclosure will be described in further detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and do not limit the disclosure. The described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present disclosure.

[0033] As shown in FIG. 1, the present disclosure provides a method S100 for improving the corrosion resistance of an aluminide cladding coating, which comprises the following specific steps S110-S140:

[0034] S110, mixing solid-phase cladding powder and liquid-phase binder, stirring and ball-milling to obtain cladding slurry.

[0035] Specifically, each component in the solid phase cladding powder is sieved through a 1000 mesh sieve, and then each component is placed in a planetary ball mill for ball milling mixing, with a ball milling speed of 350-400 rpm and a ball milling time of 12-24 h. After that, the mixed solid phase cladding powder is mixed with the liquid phase binder, and after being fully stirred for 2-4 h, the mixture is placed in a planetary ball mill for ball milling mixing, with a ball milling speed of 350-400 rpm and a ball milling time of 8-12 h, to obtain the cladding slurry. That is, the solid phase cladding powder is first ball-mixed for pre-mixing, and then the solid phase cladding powder is ball-mixed with the liquid phase binder.

[0036] In some optional embodiments, the solid phase cladding powder is an aluminum infiltration source, a modifier, and an activator, and of course, the total percentage content of each component in the solid phase cladding powder is 100%.

[0037] As an optional solution, the aluminum infiltration source is NiAl and Al, and the content of NiAl is 50-70% and the content of Al is 15-40% by mass percentage. For example, the content of NiAl is preferably 50%, 55%, 60%, 65%, or 70%, and the content of Al is preferably 15%, 20%, 25%, 30%, 35%, or 40%.

[0038] In the present embodiment, by taking NiAl as one of the components of the aluminum infiltration source, this component can form an active intermediate AlCl x with NH4Cl, thereby promoting the generation of active aluminum atoms and the speed of infiltration into the matrix, secondly, this component can also be directly cladded into the infiltration layer to improve the wear resistance and corrosion resistance of the infiltration layer, and thirdly, this component can also inhibit the generation of brittle aluminum-rich phases such as NiAl3 and Ni2Al3 in the infiltration layer, thereby enhancing the wear resistance of the coating and prolonging the service life of the pipe.

[0039] As an optional solution, the modifier is Si and Pt, wherein the content of Si is 0-5% and the content of Pt is preferably 0-5% by mass percentage. That is, in some optional embodiments, the solid phase cladding powder can not include a modifier, can only include a Si component, can only include a Pt component, and of course, can also include both Si and Pt components.

[0040] As an optional solution, the content of Si is preferably 1%, 2%, 3%, 4%, or 5%, and the content of Pt is preferably 1%, 2%, 3%, 4%, or 5%.

[0041] In the embodiment, the solid-phase cladding powder not only contains metal powder, but also contains modified elements. The addition of the modified element Si can form a continuous SiO2 passivation film, thereby improving the oxidation resistance and heat corrosion resistance. The addition of the modified element Pt can provide a channel for the Al element, form a dense oxide, inhibit or reduce the outward diffusion of alloy elements, accelerate the transition of θ-Al2O3 to α-Al2O3, improve the film-substrate adhesion, effectively inhibit internal oxidation and internal sulfuration, and improve the heat corrosion resistance of the coating.

[0042] As an optional solution, the activator is NH4Cl, and the content of NH4Cl is 0-5% by mass, for example, 1%, 2%, 3%, 4%, or 5%. That is, in some optional embodiments, the solid-phase cladding powder can not include an activator.

[0043] It should be understood that, when the halide NH4Cl is added to the solid-phase cladding powder, the component can play a role in catalyzing and activating, thereby improving the infiltration speed and the quality of the coating.

[0044] In other optional embodiments, the liquid-phase binder is ethyl acetate. Of course, the liquid-phase binder can also be other high-temperature organic binders, for example, polyvinyl alcohol, carboxymethyl cellulose sodium aqueous solution, nitrocellulose binder, etc. This liquid-phase binder component can adhere the metal powder slurry to the surface of the substrate, and after drying and solidification treatment, a more uniform and dense coating layer is formed. At the same time, it can prevent the mutual adhesion of metal powders to form metal sintering, resulting in uneven infiltration layer. Furthermore, the evaporation of ethyl acetate and other liquid-phase binders during laser cladding does not affect the process.

[0045] As an optional solution, 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%, or 30%.

[0046] S120, surface cleaning and preheating treatment are performed on the workpiece to be plated.

[0047] Specifically, the workpiece to be plated is cleaned for 5-10 min using a high-pressure water gun to remove oil stains, dust, and other contaminants on the surface of the workpiece and remove the oxide skin. At the same time, the workpiece can be washed with alcohol or acetone to provide a clean and metallic luster surface for subsequent slurry spraying. Then, the workpiece is subjected to medium-frequency preheating treatment at 200-250°C for 30-60 min.

[0048] S130, the cladding slurry is sprayed onto the surface of the workpiece to be plated, and drying and solidification treatment is performed to form a pre-sprayed layer on the surface of the workpiece.

[0049] Specifically, the cladding slurry obtained in step S110 is sprayed onto the surface of the workpiece treated in step S120 once, and naturally air-dried for 24-48 h, and then cured at 300-450 ℃ for 24-48 h, so as to obtain a preset sprayed layer on the surface of the workpiece. The thickness of the preset sprayed layer is 1-5 mm, and the coating coverage is not less than 98%. The slurry layer is too thin to provide sufficient penetration, and is too thick to easily crack and peel off, affecting the uniformity of the thickness of the permeation layer.

[0050] It should be understood that the present embodiment is to spray the slurry once to a suitable thickness, and cannot be sprayed in multiple layers.

[0051] In the present embodiment, the segmented slurry curing process by adopting natural air-drying combined with low-temperature curing effectively avoids the micro-cracks and micro-pores of the slurry layer due to thermal stress when directly dried, and enhances the bonding strength of the slurry layer and the surface of the workpiece.

[0052] S140, the workpiece with the preset sprayed layer is placed in an inert atmosphere for laser cladding treatment, and an aluminide cladding coating is obtained after cooling.

[0053] In some optional embodiments, in the laser cladding treatment, the laser power is 2-2.8 KW, the scanning speed is 20-40 mm / s, the spot diameter is 2-5 mm, the workpiece rotation speed is 0-5 r / min, and the Ar gas flow rate is 15-20 L / min.

[0054] It should be understood that after obtaining the aluminide cladding coating, the residue on the surface of the workpiece should also be treated, for example, the surface residue of the workpiece is washed by a high-pressure water gun or a high-pressure gas flow, and is naturally air-dried.

[0055] In other optional embodiments, the thickness of the obtained aluminide cladding coating is 1.15-2.95 mm.

[0056] The method of the present embodiment is suitable for the preparation of an oxidation-resistant coating of austenitic steel and high-temperature alloy parts for large-scale boilers, oil and gas field transportation pipelines and other workpieces with large length-diameter ratios and various complex shapes.

[0057] In the present embodiment, a relatively thick aluminide cladding coating can be obtained by combining the laser cladding process with aluminizing. The process has the advantages of concentrated heat, short action time, small heat-affected zone of the cladding area, high bonding strength of the coating and the base material, high production efficiency of the coating, controllable thickness, high process repeatability, strong practicality and universality.

[0058] In the embodiment, the main process parameters such as the solid phase cladding component content, the modifier additive content, the spraying layer thickness and the laser cladding parameters are adjusted to prepare the aluminide cladding coating with a thickness of 1.15-2.95 mm and good metallurgical bonding with the substrate. The aluminide cladding coating has an oxidation resistance capacity 19-65 times higher than that of the base material in a 600℃ pure water vapor environment and 20-78 times higher than that of the base material in a 650℃ pure water vapor environment, which shows that the aluminide cladding coating prepared by the method effectively improves the oxidation resistance capacity of the alloy base material in the water vapor environment.

[0059] The method for improving the corrosion resistance of the aluminide cladding coating will be further described below in combination with several specific examples.

[0060] Example 1

[0061] Step 1, the solid phase components are weighed according to the mass ratio, including 50% of NiAl, 40% of Al, 2% of NH4Cl, 4% of Si and 4% of Pt, which are placed in a planetary ball mill for ball milling at 400 rpm for 12 h to obtain the solid phase cladding powder; then, 10% of ethyl acetate is added and fully stirred for 4 h, and then placed in a planetary ball mill for ball milling at 400 rpm for 12 h, and the uniformly mixed slurry, i.e. the cladding slurry, is obtained.

[0062] Step 2, the workpiece surface is cleaned with a high-pressure water gun for 5 min and then washed with alcohol or acetone; then, the workpiece is preheated at 250℃ for 45 min by medium frequency, the slurry layer thickness is preset to 3 mm by spraying treatment, and the coating coverage rate is kept not less than 98%; then, the workpiece is naturally air-dried for 48 h and solidified at 450℃ for 48 h.

[0063] Step 3, the workpiece is placed under Ar for laser cladding, the laser power is 2 KW, the scanning rate is 40 mm / s, the spot diameter is 5 mm, the workpiece rotation speed is 5 r / min, and the Ar gas flow rate is 20 L / min; after completion, the workpiece surface residue is washed with high-pressure airflow, and the aluminide cladding coating is obtained, which has a thickness of 2.35 mm, as shown in Table 1.

[0064] Example 2

[0065] The steps of the example are the same as those of Example 1, the same solid phase cladding powder and liquid phase binder ratio are preserved, and the difference lies in that the laser power in the laser treatment parameters of Step 3 is changed to 2.8 KW, and the aluminide cladding coating formed on the workpiece surface has a thickness of 2.45 mm after treatment, as shown in Table 1.

[0066] Example 3

[0067] The steps of the present example are the same as those of Example 1, the same solid phase cladding powder and liquid phase binder ratio are maintained, the difference lies in that the laser power in the laser treatment parameters of step 3 is changed to 2.8 KW, the scanning speed is 20 mm / s, the Ar gas flow is 15 L / min, and the rotating speed is 4 r / min. After treatment, the thickness of the aluminide cladding coating formed on the surface of the workpiece is 2.18 mm, as shown in Table 1.

[0068] Example 4

[0069] The steps of the present example are the same as those of Example 1, the same solid phase cladding powder and liquid phase binder ratio are maintained, the difference lies in that the laser power in the laser treatment parameters of step 3 is changed to 2.8 KW, the scanning speed is 20 mm / s, the spot diameter is 2 mm, and the Ar gas flow is 15 L / min. After treatment, the thickness of the aluminide cladding coating formed on the surface of the workpiece is 1.15 mm, as shown in Table 1.

[0070] As shown in FIG. 2, according to the cross-sectional morphology, the infiltration layer has uniform structure, moderate thickness, and sufficient Al atom diffusion, and the infiltration layer and the substrate are in good metallurgical bonding and are not easy to fall off.

[0071] Example 5

[0072] The steps of the present example are the same as those of Example 1, the same solid phase cladding powder and liquid phase binder ratio are maintained, the difference lies in that the laser power in the laser treatment parameters of step 3 is changed to 2.5 KW, the scanning speed is 30 mm / s, the spot diameter is 2 mm, the Ar gas flow is 18 L / min, and the rotating speed is 2 r / min. After treatment, the thickness of the aluminide cladding coating formed on the surface of the workpiece is 1.54 mm, as shown in Table 1.

[0073] Example 6

[0074] The steps of the present example are the same as those of Example 1, the same solid phase cladding powder and liquid phase binder ratio are maintained, the difference lies in that the laser power in the laser treatment parameters of step 3 is changed to 2.4 KW, the scanning speed is 25 mm / s, the spot diameter is 2 mm, the Ar gas flow is 15 L / min, and the rotating speed is 2 r / min. After treatment, the thickness of the aluminide cladding coating formed on the surface of the workpiece is 2.32 mm, as shown in Table 1.

[0075] Example 7

[0076] The steps of the present example are the same as those of Example 1, the same solid phase cladding powder and liquid phase binder ratio are maintained, the difference lies in that the laser power in the laser treatment parameters of step 3 is changed to 2.8 KW, the scanning speed is 35 mm / s, and the spot diameter is 3 mm. After treatment, the thickness of the aluminide cladding coating formed on the surface of the workpiece is 2.41 mm, as shown in Table 1.

[0077] Example 8

[0078] The steps of this example are the same as Example 1, the same solid phase cladding powder and liquid phase binder ratio are preserved, the difference lies in changing the laser power in the laser processing parameters of step 3 to 2.6KW, the scanning speed to 25mm / s, the spot diameter to 3mm, the Ar gas flow to 18L / min, and the rotation speed to 4r / min. After processing, the thickness of the aluminide cladding coating formed on the surface of the workpiece is 2.37mm, as shown in Table 1.

[0079] Example 9

[0080] The steps of this example are the same as Example 1, the same solid phase cladding powder and liquid phase binder ratio are preserved, the difference lies in changing the laser power in the laser processing parameters of step 3 to 2.8KW, the spot diameter to 4mm, and the rotation speed to 4r / min. After processing, the thickness of the aluminide cladding coating formed on the surface of the workpiece is 2.68mm, as shown in Table 1.

[0081] In summary, according to Examples 1-9, the thickness of the infiltration layer is about 1.15-2.95mm, more preferably, the thickness of the infiltration layer is greater than 2mm, which is much higher than the current coating thickness, meeting the long-term application requirements of the pipe.

[0082] Table 1 Laser cladding process parameters and coating thickness of Examples 1-9

[0083] Example 10

[0084] Step 1, weigh the solid phase 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 350rpm for 24h to obtain a solid phase cladding powder; then, add 30% ethyl acetate and stir thoroughly for 2h, then place it in a planetary ball mill at 400rpm for 12h, and after completion, obtain a uniformly mixed slurry, which is the cladding slurry.

[0085] Step 2, clean the surface of the workpiece with a high-pressure water gun for 5min, and then rinse it with alcohol or acetone; then, preheat the workpiece at 200℃ for 60min, and use spray processing to pre-set the slurry layer thickness to 5mm, keeping the coating coverage rate not less than 98%; then, let the workpiece air dry for 24h, and solidify it at 300℃ for 48h.

[0086] Step 3, the workpiece is placed under Ar for laser cladding, the laser power is 2.5 KW, the scanning rate is 20 mm / s, the spot diameter is 2 mm, the workpiece rotation speed is 5 r / min, and the Ar gas flow is 15 L / min; after completion, it is cooled to room temperature and the workpiece surface residue is washed with high-pressure airflow, and an aluminide cladding coating with a thickness of 1.65 mm is formed on the surface of the workpiece, as shown in Table 2.

[0087] Example 11

[0088] Step 1, the solid phase ingredients are weighed according to the mass ratio, including 50% NiAl, 40% Al, 5% NH4Cl and 5% Pt, which are placed in a planetary ball mill at 400 rpm for 24 h to obtain solid phase cladding powder; then, 20% ethyl acetate is added and stirred thoroughly for 2 h, and then placed in a planetary ball mill at 350 rpm for 8 h, and then a uniformly mixed slurry is obtained, which is the cladding slurry.

[0089] Step 2, the workpiece surface is cleaned with a high-pressure water gun for 5 min, and then washed clean with alcohol or acetone; then, the workpiece is preheated at 250°C for 30 min, the slurry layer is pre-set to a thickness of 2 mm by spraying treatment, and the coating coverage is maintained at not less than 98%; then, the workpiece is naturally air-dried for 24 h, and solidified at 450°C for 48 h.

[0090] Step 3, the workpiece is placed under Ar for laser cladding, the laser power is 2.8 KW, the scanning rate is 40 mm / s, the spot diameter is 3 mm, the workpiece rotation speed is 2 r / min, and the Ar gas flow is 15 L / min; after completion, it is cooled to room temperature and the workpiece surface residue is washed with high-pressure airflow, and an aluminide cladding coating with a thickness of 2.36 mm is formed on the surface of the workpiece, as shown in Table 2.

[0091] Example 12

[0092] Step 1, the solid phase ingredients are weighed according to the mass ratio, including 50% NiAl, 40% Al, 5% NH4Cl and 5% Si, which are placed in a planetary ball mill at 400 rpm for 12 h to obtain solid phase cladding powder; then, 20% ethyl acetate is added and stirred thoroughly for 2 h, and then placed in a planetary ball mill at 350 rpm for 12 h, and then a uniformly mixed slurry is obtained, which is the cladding slurry.

[0093] Step 2, the workpiece surface is cleaned with a high-pressure water gun for 5 min, and then washed clean with alcohol or acetone; then, the workpiece is preheated at 200°C for 60 min, the slurry layer is pre-set to a thickness of 5 mm by spraying treatment, and the coating coverage is maintained at not less than 98%; then, the workpiece is naturally air-dried for 24 h, and solidified at 400°C for 48 h.

[0094] Step 3, the workpiece is placed under Ar for laser cladding, the laser power is 2.8 KW, the scanning rate is 20 mm / s, the spot diameter is 3 mm, the workpiece rotation speed is 5 r / min, and the Ar gas flow is 15 L / min; after completion, it is cooled to room temperature and the workpiece surface residue is washed with high-pressure airflow, and an aluminide cladding coating with a thickness of 2.43 mm is formed on the surface of the workpiece, as shown in Table 2.

[0095] Example 13

[0096] Step 1, the solid phase ingredients are weighed according to the mass ratio, including 60% of NiAl, 30% of Al, 5% of Si and 5% of Pt, which are placed in a planetary ball mill at 400 rpm for 24 h to obtain solid phase cladding powder; then, 30% of ethyl acetate is added and stirred thoroughly for 2 h, and then placed in a planetary ball mill at 400 rpm for 12 h, and after completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0097] Step 2, the workpiece surface is cleaned with a high-pressure water gun for 5 min and washed clean with alcohol or acetone; then, the workpiece is preheated at 250°C for 45 min, the prepositioned slurry layer thickness is 5 mm by using spray treatment, and the coating coverage is maintained at not less than 98%; then, the workpiece is naturally air-dried for 24 h and solidified at 450°C for 48 h.

[0098] Step 3, the workpiece is placed under Ar for laser cladding, the laser power is 2 KW, the scanning rate is 30 mm / s, the spot diameter is 5 mm, the workpiece rotation speed is 5 r / min, and the Ar gas flow is 18 L / min; after completion, it is cooled to room temperature and the workpiece surface residue is washed with high-pressure airflow, and an aluminide cladding coating with a thickness of 2.40 mm is formed on the surface of the workpiece, as shown in Table 2.

[0099] Example 14

[0100] Step 1, the solid phase ingredients are weighed according to the mass ratio, including 65% of NiAl, 25% of Al, 2% of NH4Cl, 4% of Si and 4% of Pt, which are placed in a planetary ball mill at 350 rpm for 12 h to obtain solid phase cladding powder; then, 30% of ethyl acetate is added and stirred thoroughly for 4 h, and then placed in a planetary ball mill at 400 rpm for 8 h, and after completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0101] Step 2, the workpiece surface is cleaned with a high-pressure water gun for 5 min and washed clean with alcohol or acetone; then, the workpiece is preheated at 250°C for 60 min, the prepositioned slurry layer thickness is 4 mm by using spray treatment, and the coating coverage is maintained at not less than 98%; then, the workpiece is naturally air-dried for 36 h and solidified at 450°C for 48 h.

[0102] Step 3, the workpiece is placed under Ar for laser cladding, the laser power is 2.8 KW, the scanning rate is 40 mm / s, the spot diameter is 5 mm, the workpiece rotation speed is 4 r / min, and the Ar gas flow is 20 L / min; after completion, it is cooled to room temperature and the workpiece surface residue is washed with high-pressure airflow, and an aluminide cladding coating with a thickness of 2.42 mm is formed on the surface of the workpiece, as shown in Table 2.

[0103] Example 15

[0104] Step 1, the solid phase ingredients are weighed according to the mass ratio, including 65% of NiAl, 25% of Al, 4% of NH4Cl, 2% of Si and 4% of Pt, which are placed in a planetary ball mill at 350 rpm for 24 h to obtain solid phase cladding powder; then, 20% of ethyl acetate is added and stirred thoroughly for 4 h, and then placed in a planetary ball mill at 400 rpm for 8 h, and after completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0105] Step 2, the workpiece surface is cleaned with a high-pressure water gun for 5 min and washed clean with alcohol or acetone; then, the workpiece is preheated at 250°C for 60 min, the slurry layer thickness is preset to 5 mm by spray treatment, and the coating coverage is maintained at not less than 98%; then, the workpiece is naturally air-dried for 48 h and solidified at 450°C for 48 h.

[0106] Step 3, the workpiece is placed under Ar for laser cladding, the laser power is 2.8 KW, the scanning rate is 40 mm / s, the spot diameter is 4 mm, the workpiece rotation speed is 4 r / min, and the Ar gas flow is 15 L / min; after completion, it is cooled to room temperature and the workpiece surface residue is washed with high-pressure airflow, and an aluminide cladding coating with a thickness of 2.73 mm is formed on the surface of the workpiece, as shown in Table 2.

[0107] Example 16

[0108] Step 1, the solid phase ingredients are weighed according to the mass ratio, including 65% of NiAl, 25% of Al, 4% of NH4Cl, 2% of Si and 4% of Pt, which are placed in a planetary ball mill at 350 rpm for 24 h to obtain solid phase cladding powder; then, 20% of ethyl acetate is added and stirred thoroughly for 4 h, and then placed in a planetary ball mill at 400 rpm for 8 h, and after completion, a uniformly mixed slurry is obtained, which is the cladding slurry.

[0109] Step 2, the workpiece surface is cleaned with a high-pressure water gun for 5 min and washed clean with alcohol or acetone; then, the workpiece is preheated at 250°C for 60 min, the slurry layer thickness is preset to 5 mm by spray treatment, and the coating coverage is maintained at not less than 98%; then, the workpiece is naturally air-dried for 48 h and solidified at 450°C for 48 h.

[0110] Step 3, the workpiece is placed under Ar laser cladding, the laser power is 2.8KW, the scanning speed is 35mm / s, the spot diameter is 4mm, the workpiece rotation speed is 2r / min, the Ar gas flow is 18L / min; after completion, cool to room temperature and flush the workpiece surface residue with high pressure airflow, the aluminide cladding coating formed on the workpiece surface is 2.77mm thick, as shown in Table 2.

[0111] In summary, according to Examples 10-16, changing the ratio of solid phase cladding powder, the thickness of the infiltration layer is mostly above 2mm, which shows that when the components of the solid phase cladding powder are within the above ratio range and the laser cladding process parameters are within the range given in the foregoing, the thickness of the coating obtained is mostly above 2mm, effectively improving the service life of the pipe.

[0112] Table 2 Laser cladding process parameters and coating thickness of Examples 10-16

[0113] The present disclosure proposes a method for improving the corrosion resistance of aluminide cladding coating, which has the following beneficial effects compared with the prior art:

[0114] Firstly, the present disclosure adds halide NH4Cl to the slurry components, which has the effect of catalyzing infiltration and activation, improving the infiltration speed and coating quality;

[0115] Secondly, the present disclosure introduces modified elements Si and Pt into the solid phase powder, which can accelerate the oxide film transformation process and form a difficultly soluble silicon oxygen protective layer, enhancing the oxidation and corrosion resistance of the coating;

[0116] Thirdly, the present disclosure prepares the coating by laser cladding process, which has the advantages of concentrated heat, short action time, small heat affected zone of cladding area, and high bonding strength of the coating and the base material;

[0117] Fourthly, the present disclosure prepares the coating by an integrated laser cladding process production line, which has the advantages of high coating production efficiency, controllable thickness, high process repeatability, strong practicality and universality;

[0118] Fifthly, the method of the present disclosure is suitable for austenitic steel and high-temperature alloy parts used in large long-diameter ratio and various complex-shaped workpieces such as large boilers and oil and gas pipeline, which has strong practicality, high infiltration rate, excellent film-base bonding force, and excellent industrial batch production benefits.

[0119] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present disclosure, but the present disclosure is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also considered as the protection scope of the present 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 and ball milling to obtain cladding slurry; Surface cleaning and preheating treatment of the workpiece to be plated; Spraying the cladding slurry on the surface of the workpiece to be plated, drying and curing to form a pre-spraying layer on the surface of the workpiece; Placing the workpiece with the pre-spraying layer in an inert atmosphere for laser cladding treatment, and obtaining an aluminide cladding coating after cooling.

2. The method of claim 1, wherein, The solid phase cladding powder comprises aluminum source, modifier and activator.

3. The method of claim 2, wherein, The aluminum source is NiAl and Al.

4. The method of claim 2, wherein, The modifier is Si and Pt.

5. The method of claim 2, wherein, The activator is NH4Cl.

6. The method according to any one of claims 2 to 5, characterized in that, 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 NH4Cl is 0-5%.

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

8. The method of claim 7, wherein, The content of the liquid phase binder is 10-30% of the mass of the solid phase cladding powder.

9. The method of claim 1, wherein, 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 rate is 15-20L / min.

10. The method of claim 1, wherein, The thickness of the spraying layer is 1-5mm; The thickness of the aluminide cladding coating is 1.15-2.95mm.

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