Cast infiltration coating and preparation method thereof, and air intake duct with cast infiltration layer

Abstract

The present application relates to the field of coating technology, and in particular to a cast-infiltration coating and a preparation method thereof, and an air intake duct with a cast-infiltration layer. The cast-infiltration coating comprises: 30%-50% by weight of alloy powder; 3%-7% by weight of binder; 1%-2% by weight of rare earth metal oxide; 0.1%-2.0% by weight of pH regulator; and, the remaining amount of dispersion medium, wherein the dispersion medium comprises the following components in parts by weight: 30-50 parts of water, 1-5 parts of organic solvent, 1-3 parts of defoaming agent, and 5-20 parts of poly(methyl)acrylate polymer. The cast-infiltration coating can avoid excessive precipitation of the alloy powder, and when precipitation occurs, the precipitation can be redispersed by simple stirring, and the cast-infiltration layer formed is more dense, reducing the occurrence of local acid etching and slowing down the acid etching rate, thereby improving the acid corrosion resistance and uniformity of the cast-infiltration coating.

Description

Technical Field

[0001] The present application relates to the technical field of coatings, and in particular to a cast infiltration coating and a preparation method thereof, and an air intake duct with a cast infiltration layer. Background Art

[0002] Cast infiltration is the process of using the residual heat from the solidification of the poured metal to form a cast-infiltration layer of alloy or ceramic powder on the surface of the casting with special properties. The cast-infiltration layer is generally wear-resistant, corrosion-resistant, and heat-resistant. The quality of the cast-infiltration layer depends on the performance of the cast-infiltration coating. Existing cast-infiltration coatings are generally high-density metal particles with a large specific gravity and easy precipitation, resulting in reduced heat resistance, suspension, and adhesion of the cast-infiltration coating. The cast-infiltration coating will be washed away during the pouring of molten steel or iron. In addition, the acid corrosion resistance of existing cast-infiltration coatings is not high enough. When the cast-infiltration layer is used in acidic environments, such as the engine intake duct, it is still prone to localized or large-scale corrosion.

[0003] During engine operation, some high-temperature exhaust gas flows into the intake duct through the EGR system, where it mixes with fresh air and is then sent into the cylinder for combustion. However, after shutdown, the engine temperature drops, and the remaining water vapor in the intake duct condenses into water droplets when it cools. These droplets adhere to the inner surface of the intake duct. The accumulated water in the intake duct reacts with compounds such as sulfur dioxide produced during engine combustion to form acidic substances, which corrode the intake duct. Therefore, improving the acid corrosion resistance and uniformity of cast-infiltration coatings is of great significance. Summary of the Invention

[0004] The present application discloses a cast infiltration coating and a preparation method thereof, and an air intake duct with a cast infiltration layer, so as to solve the problems of low acid corrosion resistance and uniformity of existing cast infiltration coatings.

[0005] To achieve the above objectives, this application provides the following technical solutions:

[0006] In the first aspect, the present application provides a cast infiltration coating, which includes: 30%-50% by weight of alloy powder; 3%-7% by weight of binder; 1%-2% by weight of rare earth metal oxide; 0.1%-2.0% by weight of pH regulator; and, the remaining amount of dispersion medium, wherein the dispersion medium includes the following components in parts by weight: 30-50 parts of water, 1-5 parts of organic solvent, 1-3 parts of defoaming agent, and 5-20 parts of poly(meth)acrylate polymer.

[0007] Furthermore, the alloy powder is high carbon ferrochrome powder; the particle size of the alloy powder is 15-40 microns.

[0008] Furthermore, the binder is di(methacryloyloxyethyl) hydrogen phosphate.

[0009] Furthermore, the rare earth metal oxide includes at least one of yttrium oxide or cerium oxide.

[0010] Furthermore, the organic solvent is an organic solvent having a boiling point higher than that of water, and the defoaming agent is a silicone defoaming agent.

[0011] In the second aspect, a method for preparing the cast infiltration coating of the first aspect is provided, the method comprising the following steps: dispersing rare earth metal oxide, binder and alloy powder into a dispersion medium in a mass ratio of 1-2:3-7:30-50 to obtain a mixed slurry; adding a pH regulator to the mixed slurry and adjusting the pH to 8-9 to obtain the cast infiltration coating.

[0012] Furthermore, the method further includes pre-processing the alloy powder, which includes the following steps:

[0013] The zirconium oxide and the alloy are mixed in a mass ratio of 15:1 to obtain a mixed powder;

[0014] The mixed powder is ball-milled using a high-energy ball mill to obtain alloy powder with a particle size of 10-15 microns.

[0015] Furthermore, the method further includes the step of preparing a dispersion medium: mixing water, an organic solvent and a defoaming agent, stirring the mixture at a stirring speed of 500-1000 r / min for 10-20 min, then adding a poly(meth)acrylate polymer, and dispersing the mixture at a dispersion speed of 500-1000 r / min for 0.5-1 h to obtain a dispersion medium.

[0016] Furthermore, the method also includes preparing a poly(meth)acrylate polymer: under the protection of high-purity argon, tetrahydrofuran and N-vinylcarbazole are mixed, and 1%-3% lithium chloride is added dropwise to the reaction system at a temperature of -60°C to -80°C with stirring, and the reaction is carried out for 1-1.5 hours; methacrylate is continuously added and the reaction is carried out for 1-1.5 hours; finally, 1%-3% methanol is added to terminate the reaction, and the precipitated solid is filtered out, the solid is dissolved in tetrahydrofuran, and then dripped into methanol for precipitation, and the filtration is repeated at least twice, and the precipitated solid is vacuum dried to obtain a poly(meth)acrylate polymer.

[0017] In a third aspect, the present application provides an air intake duct with a cast infiltration layer, which includes a pipe body, and the inner wall of the pipe body is provided with a cast infiltration layer prepared using the cast infiltration coating of the first aspect, and the thickness of the cast infiltration layer is 1-2 mm.

[0018] The technical solution of this application has the following beneficial effects:

[0019] The cast infiltration coating provided by the present application contains a dispersion medium including a poly(meth)acrylate polymer, which helps to evenly disperse the alloy powder and avoid excessive precipitation of the alloy powder. When precipitation occurs, the precipitation can be redispersed by simple stirring, which makes it easy to produce in an automated process. In addition, the cast infiltration coating with the addition of rare earth metal oxides forms a denser cast infiltration layer, reduces the occurrence of local acid corrosion, slows down the acid corrosion rate, and thus improves the acid corrosion resistance and uniformity of the cast infiltration coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of the air inlet duct with a cast-infiltration layer in Example 1 of the present application;

[0021] Figure 2 This is a cross-sectional view of the air intake duct with the cast-infiltration layer after acid etching in Example 1 of the present application;

[0022] Figure 3 This is a cross-sectional view of the air intake duct in Comparative Example 2 of the present application;

[0023] Figure 4 Polarization curve diagram of the air inlet in Example 1 and Comparative Example 3 of the present application;

[0024] Figure 5 Impedance spectra of the air intake duct in Example 1 and Comparative Example 3 of the present application;

[0025] Figure 6 This is a comparison chart of the acid corrosion rate of the air intake in Example 1 and Comparative Example 3 of the present application.

[0026] Figure numbers: 100 - cast-infiltrated layer; 200 - tube body. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of this application more clear, this application will be further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0028] The application scenarios described in the embodiments of this application are intended to more clearly illustrate the technical solutions of the embodiments of this application and do not constitute a limitation on the technical solutions provided by the embodiments of this application. Persons skilled in the art will appreciate that, as new application scenarios emerge, the technical solutions provided by the embodiments of this application are equally applicable to similar technical problems. In the description of this application, unless otherwise specified, "multiple" means two or more.

[0029] Existing cast-infiltration coatings are generally high-density metal particles with a large specific gravity and are easy to precipitate. Moreover, the acid corrosion resistance of existing cast-infiltration coatings is not high enough. When the cast-infiltration layer is used in an acidic environment, it is still prone to local or large-area corrosion.

[0030] In view of this, an embodiment of the present application provides a cast infiltration coating, which includes: 30%-50% by weight of alloy powder; 3%-7% by weight of binder; 1%-2% by weight of rare earth metal oxide; 0.1%-2.0% by weight of pH regulator; and, the remaining amount of dispersion medium, wherein the dispersion medium includes the following components in parts by weight: 30-50 parts of water, 1-5 parts of organic solvent, 1-3 parts of defoaming agent, and 5-20 parts of poly(meth)acrylate polymer.

[0031] In an optional solution of the embodiment of the present application, the alloy powder may be high-carbon ferrochrome powder, wherein the high-carbon ferrochrome powder includes the following components in parts by weight: C: 3-5%, Cr: 50-65%, and the balance Fe.

[0032] In an optional solution of the embodiment of the present application, the particle size of the alloy powder is 15-40 microns.

[0033] In an optional embodiment of the present application, the binder is di(methacryloyloxyethyl) hydrogen phosphate. Di(methacryloyloxyethyl) hydrogen phosphate has a bis(propylene) structure, exhibits good stability in high-temperature environments, and produces low gassing. This effectively avoids the formation of pores and slag holes in the casting caused by the poor thermal stability of the binder, thereby improving the quality of the cast-infiltrated layer.

[0034] In an optional embodiment of the present application, the rare earth metal oxide includes at least one of yttrium oxide or cerium oxide. The addition of the rare earth element results in a denser cast-infiltration layer, which reduces the occurrence of localized acid corrosion. It also effectively reduces corrosion current, slows the corrosion rate, and improves the corrosion resistance of the cast-infiltration layer.

[0035] In an optional solution of the embodiment of the present application, the pH adjuster can be an organic amine, for example, ethanolamine, diethanolamine or triethanolamine. The pH value of the casting coating is adjusted to between 8 and 9 by adding the pH adjuster.

[0036] It can be understood that the cast infiltration coating in the embodiment of the present application is added with an aqueous dispersion medium, which can prevent the alloy powder from excessively precipitating in the coating, and in the event of precipitation, the precipitate can be redispersed by simple stirring, which is easy to produce in an automated process.

[0037] The organic solvent is an organic solvent having a boiling point higher than that of water, and illustratively, the organic solvent may be ethylene glycol; the defoaming agent is an organosilicon defoaming agent, and illustratively, the defoaming agent may be organosilicon.

[0038] The composition of the cast infiltration coating has been explained above, and the preparation method of the cast infiltration coating of the present application will be specifically described below.

[0039] The preparation method of the cast infiltration coating in the embodiment of the present application comprises the following steps:

[0040] Rare earth metal oxide, binder and alloy powder are dispersed in a dispersion medium in a mass ratio of 1-2:3-7:30-50 to obtain a mixed slurry; a pH regulator is added to the mixed slurry and the pH is adjusted to 8-9 to obtain a cast infiltration coating.

[0041] An optional solution of the embodiment of the present application further includes pre-treatment of the alloy powder, and the pre-treatment includes the following steps:

[0042] 1) Mixing zirconium oxide and alloy in a mass ratio of 15:1 to obtain a mixed powder;

[0043] 2) The mixed powder is ball milled using a high-energy ball mill to obtain alloy powder with a particle size of 10-15 microns.

[0044] The ball milling time can be adjusted to obtain a mixed powder with a preset particle size. The ball milling frequency is 100-200 r / min, and the mixing time is between 10 min and 30 min.

[0045] In an optional scheme of the embodiment of the present application, the step of preparing a dispersion medium is further included: mixing water, an organic solvent and a defoaming agent, stirring for 10 min to 20 min at a stirring speed of 500-1000 r / min, then adding a poly(meth)acrylate polymer, and dispersing for 0.5-1 h at a dispersion speed of 500-1000 r / min to obtain a dispersion medium.

[0046] Among them, the organic solvent is ethylene glycol and the defoaming agent is silicone.

[0047] An optional scheme of the embodiment of the present application also includes preparing a poly(meth)acrylate polymer: under the protection of high-purity argon, tetrahydrofuran and N-vinylcarbazole are mixed, and 1%-3% lithium chloride is added dropwise to the reaction system under ice bath conditions at a temperature of -60°C--80°C while stirring, and the reaction is carried out for 1-1.5 hours; methacrylate is continued to be added and the reaction is carried out for 1-1.5 hours; finally, 1%-3% methanol is added to terminate the reaction, and the precipitated solid is filtered out, the solid is dissolved with tetrahydrofuran, and then dripped into methanol for precipitation, and the precipitated solid is vacuum dried after repeated filtration at least twice to obtain a poly(meth)acrylate polymer.

[0048] The poly(meth)acrylate polymer may be a methacrylate containing N-vinylcarbazole polymer units. Its synthesis mainly includes the following steps:

[0049] 1) N-vinyl carbazole is reacted with 2-isocyanatoethyl methacrylate to synthesize a methacrylate monomer containing an N-vinyl carbazole structure;

[0050] 2) Polymerizing the methacrylate monomer of N-vinylcarbazole to obtain a poly(meth)acrylate polymer.

[0051] Based on the same inventive concept, an embodiment of the present application also provides an air intake duct with a cast infiltration layer. The air intake duct includes a tube body, and the inner wall of the tube body is provided with a cast infiltration layer prepared using the cast infiltration coating in various possible embodiments of the present application. The thickness of the cast infiltration layer is 1-2 mm.

[0052] The structure of the air intake duct with the cast-infiltration layer is explained above. The preparation method of the air intake duct with the cast-infiltration layer of the present application will be described in detail below.

[0053] The method for preparing the air intake duct in the embodiment of the present application comprises the following steps:

[0054] 1) Applying the casting coating to the inner wall of the mold and heating it to form a coating layer;

[0055] 2) Pour the molten metal into the mold at a pouring temperature of 1400-1500℃. After cooling, take out the casting.

[0056] In an optional scheme of the embodiment of the present application, the casting mold in step 1) is a sand mold for the cylinder head intake duct, that is, the casting infiltration coating is applied to the surface of the sand mold. Specifically, the thickness of each coating is 400-600 microns. After coating, it is dried at 180-200°C for 0.5-1h, and repeatedly brushed 2-3 times to ensure that the thickness of the coating layer is 1-2mm.

[0057] In an optional embodiment of the present application, the molten metal in step 2) comprises the following chemical composition by weight: C: 3.25-3.33%, S: 0.06-0.12%, Si: 1.5-1.7%, Mn: 0.6-1%, P: ≤0.06%, with the balance being Fe. The material prepared from this molten metal composition exhibits excellent overall mechanical properties, a low melting point, a low alloying element content, and good liquid flowability, which facilitates surface infiltration.

[0058] The cast infiltration coating and its preparation method, the air intake duct with a cast infiltration layer and its preparation method in this application are further described in detail below in conjunction with specific embodiments and comparative examples.

[0059] Example 1

[0060] This embodiment provides a cast-infiltration coating and an air intake duct having a cast-infiltration layer. The preparation method of the air intake duct includes the following steps:

[0061] A) Prepare the molten metal: Quickly and accurately add the recycled materials, scrap steel, etc. into the electric furnace, then add silicon carbide, manganese silicon alloy, recarburizer, ferrosilicon and ferrosulfur, and adjust the contents of C, S, Si, Mn and P in the molten metal to meet the following composition: C%: 3.25-3.33, S%: 0.06-0.12, Si%: 1.5-1.7, Mn%: 0.6-1, P% ≤ 0.06.

[0062] B) Configure casting coating:

[0063] ①Preparation of dispersant:

[0064] Under the protection of high-purity argon, tetrahydrofuran and N-vinylcarbazole were added to a flask with a stirring device, and the flask was placed in an ice bath (-60°C--80°C). 1%-3% lithium chloride was slowly added dropwise to the reaction system under stirring, and the reaction was carried out for 1 hour. Methacrylate was continuously added at this temperature and the reaction was carried out for 1 hour. Finally, 1%-3% methanol was added dropwise to terminate the reaction, and the precipitated solid was filtered. The solid was dissolved with a small amount of tetrahydrofuran and then dropped into methanol for precipitation. After repeated filtration twice, the precipitated solid was vacuum dried to obtain N-vinylcarbazole-poly(meth)acrylate polymer.

[0065] ②Preparation of dispersion medium:

[0066] Water, an organic solvent, ethylene glycol, and a defoaming agent, silicone, are mixed and dispersed at 500-1000 r / min for 10 minutes; then, a dispersant, N-vinylcarbazole-poly(meth)acrylate polymer, is added and dispersed at 500-1000 r / min for 0.5-1 hour to obtain a dispersion medium, wherein the mass ratios of water, organic solvent, defoaming agent, and poly(meth)acrylate polymer are 30-50:1-5 and 1-3:5-20.

[0067] ③ Pretreatment of alloy powder:

[0068] The zirconium oxide and the alloy are mixed in a mass ratio of 15:1 to obtain a mixed powder;

[0069] The mixed powder is ball-milled with a high-energy ball mill at a frequency of 100-200 r / min for 1-30 minutes to obtain a pre-treated alloy powder with a particle size of 15-40 microns and a fineness of 10-15 microns.

[0070] ④ Add rare earth cerium oxide and the pretreated alloy powder to the dispersion medium obtained in step ② to obtain a mixed slurry, wherein the mass percentage of the alloy powder in the mixed slurry is 30%-50%, and the mass percentage of rare earth cerium oxide in the mixed slurry is 1%-2%. Add 3%-7% by mass of the adhesive di(methacryloyloxyethyl) hydrogen phosphate to the dispersion system, and then add the pH adjuster ethanolamine to adjust the pH of the dispersion system to 8-9 to obtain a cast infiltration coating.

[0071] C) Spraying: Apply the cast infiltration coating to the inner wall of the air inlet sand mold with a coating thickness of 1-2mm; heat and dry at 180-200℃ for 0.5-1h to harden the coating.

[0072] D) Casting: The molten metal prepared in step A) is poured into a casting mold at a pouring temperature of 1500°C. After the molten metal is completely solidified and cooled to room temperature, the casting is removed to obtain an air inlet duct with a cast-infiltrated layer.

[0073] Figure 1 This is a schematic structural diagram of the air inlet duct with a cast-infiltration layer in Example 1 of the present application. Figure 2 This is a cross-sectional view of the air inlet with the cast-infiltration layer after acid etching in Example 1 of the present application, referring to Figure 1 and Figure 2 On the surface of the pipe body 200 of the air inlet duct, there is a 1-2 mm cast-infiltration layer 100 with a surface hardness of 1800 HV. After acid etching, the cast-infiltration layer 100 is substantially undamaged.

[0074] Comparative Example 1-2

[0075] Comparative Examples 1-2 are both air intake ducts with cast infiltration layers. The specific steps can refer to Example 1. The difference is that the dispersion medium in Comparative Example 1 is replaced by water. The air intake duct in Comparative Example 1 cannot form a cast infiltration layer, and the alloy powder will be dispersed by water. The binder in Comparative Example 2 is phenolic resin. Figure 3 This is a cross-sectional view of the air intake duct in comparative example 2 of the present application, referring to Figure 3 In Comparative Example 2, the uniformity of the cast-infiltrated layer 100 on the surface of the tube body 200 is poor, and the cast-infiltrated layer 100 has many pores, resulting in a decrease in the performance of the cast-infiltrated layer 100.

[0076] Comparative Example 3

[0077] Comparative Example 3 is an existing air inlet without a cast-infiltration layer.

[0078] The acid erosion rate of the air intake in the above embodiment 1 and comparative examples 1-3 was tested under the same conditions. Figure 4 is a polarization curve diagram of the air inlet in Example 1 and Comparative Example 3 of the present application, Figure 5The impedance spectra of the air intake in Example 1 and Comparative Example 3 of the present application are as follows: Figure 6 The comparison chart of the acid erosion rate of the air inlet in Example 1 and Comparative Example 3 of the present application is shown in FIG. Figures 4 to 6 The impedance of the air intake duct with the cast-infiltration layer in Example 1 is significantly higher than that of the air intake duct without the cast-infiltration layer in Comparative Example 3. Figure 4 and Figure 5 The data in the calculation is Figure 6 The acid erosion rate of the intake duct is Figure 6 The acid corrosion rate of the air intake duct in Example 1 is significantly lower than the acid corrosion rate of the air intake duct in Comparative Example 3.

[0079] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A cast infiltration coating, characterized in that: include: 30%-50% by weight of alloy powder; 3%-7% by weight of a binder; 1%-2% by weight of rare earth metal oxides; 0.1%-2.0% by weight of a pH adjuster; and, The remaining amount of the dispersion medium comprises the following components in parts by weight: 30-50 parts of water, 1-5 parts of an organic solvent, 1-3 parts of a defoaming agent, and 5-20 parts of a poly(meth)acrylate polymer; The binder is di(methacryloyloxyethyl) hydrogen phosphate; and the alloy powder is high-carbon ferrochrome powder.

2. The cast infiltration coating according to claim 1, characterized in that The particle size of the alloy powder is 15-40 microns.

3. The cast infiltration coating according to claim 1, characterized in that The rare earth metal oxide includes at least one of yttrium oxide and cerium oxide.

4. The cast infiltration coating according to claim 1, characterized in that The organic solvent is an organic solvent with a boiling point higher than that of water, and the defoaming agent is an organosilicon defoaming agent.

5. A method for preparing the cast infiltration coating according to any one of claims 1 to 4, characterized in that: The steps include: Dispersing the rare earth metal oxide, the binder, and the alloy powder into the dispersion medium in a mass ratio of 1-2:3-7:30-50 to obtain a mixed slurry; The pH regulator is added to the mixed slurry, and the pH is adjusted to 8-9 to obtain the cast infiltration coating.

6. The method according to claim 5, characterized in that The method further includes pre-treating the alloy powder, wherein the pre-treating comprises the following steps: The zirconium oxide and the alloy are mixed in a mass ratio of 15:1 to obtain a mixed powder; The mixed powder is ball-milled using a high-energy ball mill to obtain the alloy powder with a particle size of 10-15 microns.

7. The method according to claim 5, characterized in that The step of preparing the dispersion medium is also included: Water, an organic solvent and a defoamer are mixed, stirred at 500-1000 r / min for 10-20 min, and then poly(meth)acrylate polymer is added and dispersed at a dispersion speed of 500-1000 r / min for 0.5-1 h to obtain the dispersion medium.

8. The method according to claim 7, characterized in that Also included is the preparation of poly(meth)acrylate polymers: Under the protection of high-purity argon, tetrahydrofuran and N-vinylcarbazole are mixed, and 1%-3% lithium chloride is added dropwise to the reaction system at a temperature of -60°C to -80°C with stirring, and the reaction is carried out for 1-1.5 hours; methacrylate is continuously added and the reaction is carried out for 1-1.5 hours; finally, 1%-3% methanol is added to terminate the reaction, and the precipitated solid is filtered. The solid is dissolved in tetrahydrofuran and then dripped into methanol for precipitation. After repeated filtration at least twice, the precipitated solid is vacuum dried to obtain a poly(meth)acrylate polymer.

9. An air intake duct with a cast infiltration layer, characterized in that: The invention comprises a tube body, wherein the inner wall of the tube body is provided with a cast infiltration layer prepared by using the cast infiltration coating according to any one of claims 1 to 4, and the thickness of the cast infiltration layer is 1 to 2 mm.

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