Low-temperature aluminizing material and method for preparing the same

Abstract

The application belongs to the technical field of materials, and discloses a low-temperature aluminizing material and a preparation method thereof. The low-temperature aluminizing material comprises dry materials, and the dry materials comprise the following raw materials: 1-5 parts of ammonium chloride, 0.5-1 part of modified carbon nanotubes and 100-200 parts of a permeation aid. The silane coupling agent modified carbon nanotubes effectively improve the dispersibility of the carbon nanotubes in the low-temperature aluminizing material, and the micro-pipe formed by the silane coupling agent modified carbon nanotubes added in the low-temperature aluminizing material helps the gaseous AlCl3 to quickly diffuse to the surface in the solidified aluminizing layer, realizes rapid aluminizing, and improves the production efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and particularly relates to a low-temperature aluminizing material and a preparation method thereof. BACKGROUND

[0002] With the rise of China's economic level, the demand for electricity of residents and industries is increasing, and the oxidation resistance of materials needs to be greatly improved.

[0003] To solve the above problems, the current ways to solve the problem are: one is to perform surface modification on the existing material to prepare an aluminizing layer with excellent oxidation resistance without changing the original mechanical properties of the substrate. Two is to develop new alloy materials.

[0004] Aluminum-containing intermetallic compounds or alloys are widely used in the preparation of high-temperature aluminizing layers because they can selectively oxidize to form an aluminum oxide film with certain density, stability and good adhesion, and the substrate is isolated from the oxidizing medium in the vapor. There are many methods for preparing aluminizing layers, such as chemical vapor deposition aluminizing, powder embedding aluminizing, and slurry aluminizing. Among them, slurry aluminizing is the simplest and most cost-effective operation, suitable for large-scale industrial production.

[0005] In the process of preparing the aluminizing layer, the traditional aluminizing heat treatment temperature is as high as 850-1050℃, while the tempering temperature of the martensitic heat-resistant steel commonly used in power plants is about 760℃. At a temperature much higher than the tempering temperature of the martensitic heat-resistant steel, the original mechanical properties will inevitably deteriorate. In addition, the solidified slurry layer of the traditional slurry aluminizing is too dense, and the gas-phase AlCl3 formed during the aluminizing process can only diffuse slowly through the solid slurry layer to reach the substrate surface, reducing the concentration of active aluminum atoms on the surface of the workpiece and thus reducing the aluminizing efficiency. SUMMARY

[0006] In view of the shortcomings of the prior art described above, the purpose of the present application is to provide a low-temperature aluminizing material and a preparation method thereof, in order to solve the problems existing in the prior art.

[0007] To achieve the above-mentioned purpose, the present application specifically adopts the following technical solutions.

[0008] The first aspect of the present application protects a low-temperature aluminizing slurry, which comprises a dry material, and the dry material comprises the following raw materials:

[0009] Ammonium chloride 1-5 parts

[0010] Modified carbon nanotubes 0.5-1 parts

[0011] Permeation agent 100-200 parts.

[0012] According to the technical scheme of the present application, the weight parts of the ammonium chloride can be 1-3 parts, 2.2-4 parts, or 3.8-5 parts. In a certain preferred embodiment, it is 1 part, 1.5 parts, 3 parts, or 5 parts.

[0013] According to the technical scheme of the present application, the weight parts of the modified carbon nanotubes can be 0.5-0.8 parts, 0.6-0.9 parts, or 0.7-1 part. In a certain preferred embodiment, it is 0.5 parts, 0.82 parts, 0.68 parts, or 1 part.

[0014] According to the technical scheme of the present application, the weight parts of the modified carbon nanotubes can be 100-150 parts, 130-180 parts, or 160-200 parts. In a certain preferred embodiment, it is 100 parts, 150 parts, 180 parts, or 200 parts.

[0015] According to the technical scheme of the present application, the infiltrating agent is selected from one or more of aluminum powder, iron-aluminum powder, aluminum oxide powder, and ammonium chloride.

[0016] Preferably, the particle size of the infiltrating agent is 500-800 mesh.

[0017] Preferably, the atomic ratio of iron to aluminum in the iron-aluminum powder is (45-50):(50-55). More preferably, the atomic ratio of iron to aluminum in the iron-aluminum powder can be (45-48):(50-55), or (47-50):(50-55). In a certain preferred embodiment, it is 47:52.

[0018] Preferably, the infiltrating agent is a mixture of aluminum powder, iron-aluminum powder, aluminum oxide powder, and ammonium chloride.

[0019] More preferably, the mass ratio of the aluminum powder, iron-aluminum powder, aluminum oxide powder, and ammonium chloride is (5-25):(20-40):(20-65):(1-5). Specifically, the mass ratio can be (5-25):(20-40):(20-65):(1-5), or (5-25):(20-40):(20-65):(1-5), or (5-25):(20-40):(20-65):(1-5). In a certain preferred embodiment, it is 5:40:50:1.5, 12:34:20:5, 19:28:65:1, or 25:20:35:3.

[0020] More preferably, the infiltrating agent is the mixture obtained by ball milling.

[0021] Further preferably, the rotation speed of the ball mill is 200-400 r / min. Specifically, the rotation speed of the ball mill can be 200-300 r / min, 250-320 r / min, or 300-400 r / min. In a preferred embodiment, it is 200 r / min, 300 r / min, or 400 r / min.

[0022] Further preferably, the ball milling time is 8-15 h. Specifically, the ball milling time can be 8-11 h, 10-13 h, or 11-15 h. In a preferred embodiment, it is 10 h, 12 h, 15 h, or 8 h.

[0023] Preferably, the sieve residue of the aluminum powder through a 200-mesh sieve is ≤1%.

[0024] Preferably, the sieve residue of the iron-aluminum powder through a 200-mesh sieve is ≤1%.

[0025] Preferably, the sieve residue of the aluminum oxide powder through a 200-mesh sieve is ≤1%.

[0026] Preferably, the sieve residue of the ammonium chloride through a 200-mesh sieve is ≤1%.

[0027] According to the technical solution of the present application, the preparation method of the modified carbon nanotube is as follows: dispersing a silane coupling agent in a solvent, mixing with carbon nanotubes, solid-liquid separation, drying, and obtaining the modified carbon nanotube.

[0028] Preferably, the silane coupling agent is selected from KH-570.

[0029] Preferably, the length of the carbon nanotube is 2-20 μm, and the diameter is 2-30 nm.

[0030] Preferably, the solvent is selected from one or both of water and toluene.

[0031] Preferably, the mass-volume ratio of the carbon nanotube and KH-570 is (1.0-2.0) g:(20-30) mL.

[0032] More preferably, the mass-volume ratio of the carbon nanotube and KH-570 can be (1.0-2.0) g:(20-25) mL, (1.0-2.0) g:(24-26) mL, or (1.0-2.0) g:(25-30) mL. In a preferred embodiment, it is 1 g:20 mL, 1.4 g:23 mL, 1.8 g:26 mL, or 2.0 g:30 mL.

[0033] Preferably, the mixing is by magnetic stirring.

[0034] More preferably, the stirring speed is 50-100 r / min, and the stirring time is 10-15 h.

[0035] Preferably, the solid-liquid separation is by centrifugation. More preferably, the centrifugation speed is 2000-3000 r / min, and the centrifugation time is 5-8 min.

[0036] Preferably, the drying temperature is 50-80℃.

[0037] More preferably, the drying temperature can be 50-65℃, 55-70℃, or 65-80℃. In a preferred embodiment, it is 60℃, 50℃, 70℃, or 80℃.

[0038] Preferably, the drying time is 15-20 h.

[0039] More preferably, the drying time can be 15-17 h, 16-19 h, or 17-20 h. In a preferred embodiment, it is 18 h, 20 h, or 17 h.

[0040] Preferably, the solid-liquid separation is followed by post-treatment, which includes washing.

[0041] More preferably, the washing is performed 3-10 times with water and toluene.

[0042] According to the technical solution of the present application, the low-temperature aluminizing material further comprises a wet material selected from one or both of a binder and a diluent, and the mass-to-volume ratio of the dry material and the wet material is (100-210) g:(60-100) mL.

[0043] Preferably, the mass-to-volume ratio of the dry material and the wet material can be (100-150) g:(60-100) mL, (140-180) g:(60-100) mL, or (170-210) g:(60-100) mL. In a preferred embodiment, it is 202 g:100 mL, 182.32 g:88 mL, 153.68 g:74 mL, or 105.5 g:60 mL.

[0044] Preferably, the binder is selected from aluminum dihydrogen phosphate.

[0045] Preferably, the diluent is selected from ethanol.

[0046] Preferably, the volume ratio of the binder and the diluent is (10-20):(50-80).

[0047] More preferably, the volume ratio of the binder and the diluent can be (10-20):(50-65), (10-20):(60-75), or (10-20):(70-80). In a preferred embodiment, the volume ratio is 20:80, 18:70, 14:60, or 10:50.

[0048] The second aspect of the present application protects a method for preparing a low-temperature aluminizing material as described above, comprising the following steps:

[0049] 1) activating the penetrant;

[0050] 2) mixing ammonium chloride, modified carbon nanotubes, and the activated penetrant to obtain the low-temperature aluminizing material.

[0051] According to the technical solution of the present application, the activation is performed in a protective atmosphere.

[0052] Preferably, the protective atmosphere is argon.

[0053] Preferably, the activation temperature is 800-900℃.

[0054] More preferably, the activation temperature can be 800-850℃, 840-880℃, or 860-900℃. In a preferred embodiment, the activation temperature is 800℃, 830℃, 860℃, 830℃, or 900℃.

[0055] Preferably, the activation time is 2-4h.

[0056] More preferably, the activation time can be 2-3h, 2.5-3.5h, or 3-4h. In a preferred embodiment, the activation time is 2h, 2.5h, 3h, or 4h.

[0057] The third aspect of the present application protects an aluminized layer or an article comprising an aluminized layer, wherein the aluminized layer is obtained by applying the low-temperature aluminizing material slurry described above to the surface of a component; and the article comprises the aluminized layer and the component covered by the aluminized layer.

[0058] According to the technical solution of the present application, the component is a metal component.

[0059] Preferably, the metal component is a martensitic steel.

[0060] More preferably, the martensitic steel is T92 steel.

[0061] The fourth aspect of the present application protects a method for preparing the product as described above, wherein the low-temperature aluminizing material is sprayed on the surface of the component, dried and solidified, and heat treated to aluminize the component to obtain the product.

[0062] According to the technical scheme of the present application, the drying temperature is 80-100℃.

[0063] Preferably, the drying temperature can be 80-90℃, 85-95℃, or 90-100℃. In a preferred embodiment, it is 90℃.

[0064] According to the technical scheme of the present application, the drying time is 10-20min.

[0065] Preferably, the drying time can be 10-15min, 14-18min, or 16-20min. In a preferred embodiment, it is 15min.

[0066] According to the technical scheme of the present application, the solidification temperature is 200-220℃.

[0067] Preferably, the solidification temperature can be 200-210℃, 208-218℃, or 210-220℃. In a preferred embodiment, it is 210℃.

[0068] According to the technical scheme of the present application, the solidification time is 20-40min.

[0069] Preferably, the solidification time can be 20-28min, 25-35min, or 34-40min. In a preferred embodiment, it is 30min.

[0070] According to the technical scheme of the present application, the heat treatment temperature is 600-800℃.

[0071] Preferably, the heat treatment temperature can be 600-750℃, 650-750℃, or 700-800℃. In a preferred embodiment, it is 700℃.

[0072] According to the technical scheme of the present application, the heat treatment time is 2-10h.

[0073] Preferably, the heat treatment time can be 2-6h, 4-8h, or 6-10h. In a preferred embodiment, it is 6h.

[0074] According to the technical scheme of the present application, the heat treatment is performed in a protective atmosphere.

[0075] Preferably, the protective atmosphere is argon.

[0076] Compared with the prior art, the present application has the following beneficial effects:

[0077] The low-temperature aluminizing material of the present application effectively improves the dispersibility of carbon nanotubes in the slurry by modifying the carbon nanotubes with KH-570. The micro-pipe formed by the modified carbon nanotubes added to the low-temperature aluminizing material helps the gaseous AlCl3 to quickly diffuse to the surface in the solidified slurry layer, realizes rapid aluminizing, and improves the production efficiency. In addition, the addition of iron-aluminum powder in the slurry can play a buffering role. When the active aluminum atom content in the slurry is relatively high, the iron-aluminum powder reacts with the active aluminum atoms to form Fe-Al intermetallic compounds with high aluminum content. When the aluminum content in the slurry is relatively low, the iron-aluminum powder can release aluminum to form gaseous AlCl3, appropriately improve the active aluminum atom concentration, and significantly increase the aluminizing layer thickness. When the low-temperature aluminizing material of the present application is used for aluminizing at a temperature lower than the tempering temperature of the martensitic heat-resistant steel, the matrix structure and mechanical properties will not change. BRIEF DESCRIPTION OF DRAWINGS

[0078] Figure 1 X-ray diffraction patterns of the aluminized layers of Example 5, Example 6, Example 7, Example 8, Comparative Example 1, and Comparative Example 2 of the present application are shown.

[0079] Figure 2 Scanning electron microscope images of the cross sections of the aluminized layers of Example 5 of the present application are shown.

[0080] Figure 3 Scanning electron microscope images of the cross sections of the aluminized layers of Example 6 of the present application are shown.

[0081] Figure 4 Scanning electron microscope images of the cross sections of the aluminized layers of Example 7 of the present application are shown.

[0082] Figure 5 Scanning electron microscope images of the cross sections of the aluminized layers of Example 8 of the present application are shown.

[0083] Figure 6 Scanning electron microscope images of the cross sections of the aluminized layers of Comparative Example 1 of the present application are shown.

[0084] Figure 7 Scanning electron microscope images of the cross sections of the aluminized layers of Comparative Example 2 of the present application are shown. DETAILED DESCRIPTION

[0085] The purpose of this invention is to provide a low-temperature aluminizing material, its preparation method, and its application. The dispersibility of carbon nanotubes modified with KH-570 in the slurry is improved, and the microchannels formed by the KH-570-modified carbon nanotubes facilitate the rapid diffusion of activated AlCl3 gas to the surface of the metal component in an overly dense slurry layer. This allows for aluminizing heat treatment below the tempering temperature of martensitic heat-resistant steel, achieving rapid aluminizing and improving production efficiency. Furthermore, the addition of iron-aluminum powder acts as a buffer, inhibiting the formation of brittle Fe2Al5 and FeAl3 phases in the aluminized layer due to excessive active aluminum atoms on the matrix surface. It also acts as an aluminizing aid, providing an aluminum source and significantly thickening the aluminized layer.

[0086] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0087] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0088] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0089] The sources and parameters of each raw material component used in the following embodiments and comparative examples of this application are shown in Table 1.

[0090] Table 1. Raw material sources and parameters

[0091] Ingredient name Parameter Aluminum powder Residue on a 200 mesh sieve ≤ 1% Iron-aluminum powder Residue on a 200 mesh sieve ≤ 1%; wherein Fe, 47 at.%; Al, 52 at.% Aluminum oxide powder Residue on a 200 mesh sieve ≤ 1% Ammonium chloride Residue on a 200 mesh sieve ≤ 1% Carbon nanotubes Length 110 μm, diameter 15 nm

[0092] Examples 1-4: Preparation of Modified Carbon Nanotubes

[0093] Referring to the formulation in Table 2, carbon nanotubes were dispersed in water, and ultrasonic dispersion was performed for 15 min to obtain a carbon nanotube aqueous solution; KH-570 was dissolved in toluene to obtain a toluene solution of KH-570; the carbon nanotube aqueous solution and the toluene solution of KH-570 were stirred by a magnetic stirrer, and centrifugal separation was performed to obtain a precipitate; the precipitate was washed with deionized water and toluene three times, and then was placed in a vacuum drying oven for drying to obtain modified carbon nanotubes.

[0094] Table 2 Raw materials and preparation parameters of modified carbon nanotubes

[0095] Substance Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Carbon nanotubes (g) 1.0 1.4 1.8 2.0 - 1.4 Water (mL) 100 160 220 300 - 160 Ultrasonic dispersion (min) 18 10 14 20 - 10 KH-570 (mL) 20 23 26 30 - - Toluene (mL) 20 28 35 40 - - Stirring (r / min and h) 50 and 10 68 and 12 75 and 14 100 and 15 - 68 and 12 Centrifugation (r / min and min) 2000 and 5 2400 and 6 2600 and 7 2000 and 8 - 2400 and 6 Drying (°C and h) 60 and 18 50 and 20 70 and 17 80 and 17 50 and 20

[0096] Preparation of low-temperature aluminizing material in Example 5-10

[0097] Referring to the formulation in Table 3, aluminum powder, iron-aluminum powder, aluminum oxide powder and ammonium chloride were ball milled in a planetary ball mill, and then sintered in an argon-filled tube furnace to activate to obtain a ball-milled and activated penetrant.

[0098] Table 3 Raw materials and preparation parameters of penetrant

[0099] Substance Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Wherein: aluminum powder (g) 15 15 15 15 5 25 15 15 Wherein: iron-aluminum powder (g) 30 30 30 30 40 20 30 30 Wherein: aluminum oxide powder (g) 54 54 54 54 53 50 54 54 Wherein: ammonium chloride (g) 1.0 1.0 1.0 1.0 2 5 1.0 1.0 Ball milling time (h) 10 12 15 8 10 10 Ball milling speed (r / min) 300 400 200 400 300 300 Infiltrant activation temperature (°C) 800 850 900 830 850 850 Infiltrant activation time (h) 4 3 2 3 4 4

[0100] Referring to the formulation in Table 4, the modified carbon nanotubes obtained in Example 2 were mixed with the penetrant obtained in Table 3, ammonium chloride, a binder and a diluent to obtain a low-temperature aluminizing material.

[0101] Table 4 Raw material formulation table of Example 5-10 and Comparative Example 1-2

[0102] Substance Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Ammonium chloride (g) 1.5 1.5 4.0 4.0 1.0 5.0 1.5 4 Modified carbon nanotubes (g) 1.0 1.0 0.5 1.0 1.0 1.0 - Unmodified carbon nanotubes 1.0 g Binder (mL) 15 15 15 15 20 20 15 15 Diluent (mL) 60 60 60 60 80 80 60 60 Infiltrant (g) 150 150 200 200 150 100 150 200

[0103] Based on the low-temperature aluminizing materials obtained in Example 5, Example 6, Example 7 and Example 8 in Table 4, a T92 steel was used as a metal component to prepare an article containing an aluminized layer after being coated with the low-temperature aluminizing material.

[0104] Pretreatment of the metal component: the T92 steel polished with sandpaper was degreased, and the low-temperature aluminizing material was uniformly sprayed on the degreased T92 steel to be penetrated, and then air-dried under natural conditions. The degreasing was performed by placing the T92 steel in a beaker containing alcohol, and then placing the beaker in an ultrasonic cleaner for degreasing for 20-25 min.

[0105] The article containing an aluminized layer was prepared using the low-temperature aluminizing material of Example 5, including the following steps:

[0106] The T92 steel after oil removal was placed on a workbench, and the low-temperature aluminizing material of Example 5 which was stirred uniformly was uniformly sprayed on the aluminizing part of the T92 steel after oil removal, and then the sprayed T92 steel was placed in a natural condition for air drying to obtain the air-dried metal member. The spraying thickness was 300 μm.

[0107] The air-dried metal member was placed in an oven for drying, and then the dried metal member was placed in a muffle furnace for solidification to obtain the solidified metal member. The drying was carried out in an oven at 90°C for 15 min, and the solidification was carried out in a muffle furnace at 210°C for 30 min.

[0108] The solidified metal member was placed in a tube furnace filled with argon and heat-treated at 700°C for 1 h to diffuse aluminizing, and then the metal member was taken out after the furnace was cooled to below 50°C to obtain the product containing an aluminized layer.

[0109] The product containing an aluminized layer was prepared by using the low-temperature aluminizing material of Example 6, including the following steps:

[0110] The difference from the preparation method of Example 5 was that the low-temperature aluminizing material of Example 6 was uniformly sprayed on the aluminizing part of the T92 steel after oil removal, and the heat treatment temperature was 650°C, and the other steps were the same as those of Example 5 to obtain the product containing an aluminized layer.

[0111] The product containing an aluminized layer was prepared by using the low-temperature aluminizing material of Example 7, including the following steps:

[0112] The difference from the preparation method of Example 5 was that the low-temperature aluminizing material of Example 7 was uniformly sprayed on the aluminizing part of the T92 steel after oil removal, and the heat treatment temperature was 650°C, and the other steps were the same as those of Example 5 to obtain the product containing an aluminized layer.

[0113] The product containing an aluminized layer was prepared by using the low-temperature aluminizing material of Example 8, including the following steps:

[0114] The difference from the preparation method of Example 5 was that the low-temperature aluminizing material of Example 8 was uniformly sprayed on the aluminizing part of the T92 steel after oil removal, and the heat treatment temperature was 650°C, and the other steps were the same as those of Example 5 to obtain the product containing an aluminized layer.

[0115] The products containing an aluminized layer obtained by Example 5, Example 6, Example 7 and Example 8 were analyzed by X-ray diffraction and the cross section of the aluminized layer was observed by scanning electron microscopy.

[0116] Figure 1 The X-ray diffraction patterns of the aluminized layers of Example 5, Example 6, Example 7 and Example 8.

[0117] From Figure 1As is apparent, the aluminized layer of Example 5, Example 6, Example 7, and Example 8 consists of FeAl phase.

[0118] Figure 2 A scanning electron microscope image of the cross section of the aluminized layer of Example 5.

[0119] From Figure 2 As is apparent, the thickness of the aluminized layer is 50 ± 2 μm.

[0120] Figure 3 A scanning electron microscope image of the cross section of the aluminized layer of Example 6.

[0121] From Figure 2 As is apparent, the thickness of the aluminized layer is 56 ± 2 μm.

[0122] Figure 4 A scanning electron microscope image of the cross section of the aluminized layer of Example 7.

[0123] From Figure 4 As is apparent, the thickness of the aluminized layer is 56 ± 2 μm.

[0124] Figure 5 A scanning electron microscope image of the cross section of the aluminized layer of Example 8.

[0125] From Figure 5 As is apparent, the thickness of the aluminized layer is 56 ± 2 μm.

[0126] Comparative Example 1

[0127] Comparative Example 1 differs from Example 5 in that no carbon nanotubes are added, and the specific formulation and process are shown in Tables 2, 3, and 4, and the rest is the same as Example 5, to obtain an article containing an aluminized layer, with a spray thickness of 300 μm.

[0128] The cross section of the aluminized layer is analyzed by X-ray diffraction and observed by scanning electron microscope.

[0129] Figure 1 An X-ray diffraction pattern of the surface aluminized layer of the article obtained in Comparative Example 1.

[0130] From Figure 1 As is apparent, the surface aluminized layer of Comparative Example 1 consists of FeAl.

[0131] Figure 6 A scanning electron microscope image of the cross section of the surface aluminized layer of the article obtained in Comparative Example 1.

[0132] From Figure 6 As is apparent, the thickness of the aluminized layer of Comparative Example 1 is 16 ± 2 μm.

[0133] Comparative Example 2

[0134] Comparative Example 1 differs from Example 5 in that the carbon nanotubes are not modified, and the specific formulation and process are shown in Tables 2, 3 and 4, and the rest is the same as Example 5, to obtain an aluminized product containing an aluminized layer with a spray thickness of 300 μm.

[0135] The cross section of the aluminized layer was analyzed by X-ray diffraction and observed by scanning electron microscopy.

[0136] Figure 1 The X-ray diffraction pattern of the aluminized layer of Comparative Example 2.

[0137] It can be seen that the aluminized layer of Comparative Example 2 is composed of FeAl phase. Figure 1

[0138] Figure 7 The scanning electron micrograph of the cross section of the aluminized layer of Comparative Example 2.

[0139] It can be seen that the thickness of the aluminized layer of Comparative Example 2 is 35 ± 2 μm. Figure 7 It can be seen from

[0140] Figure 2 3 It can be seen from Examples 4 and 5 that the thickness of the aluminized layer formed by the low-temperature aluminizing material of the present application is significantly higher than that of Comparative Examples 1 and 2, and the completeness is also better than that of Comparative Examples 1 and 2.

[0141] The low-temperature aluminizing material of the present application effectively improves the dispersibility of the carbon nanotubes in the slurry by modifying the carbon nanotubes with KH-570. The micro-pipe formed by the modified carbon nanotubes added in the slurry helps the gaseous AlCl3 to quickly diffuse to the surface in the solidified slurry layer, realizes rapid aluminizing, and improves the production efficiency. The high content of iron-aluminum powder added in the slurry can play a buffering role. When the content of active aluminum atoms in the slurry is high, the iron-aluminum powder reacts with the active aluminum atoms to form Fe-Al intermetallic compounds with high aluminum content. When the aluminum content in the slurry is low, the iron-aluminum powder can release aluminum to form gaseous AlCl3, appropriately increase the concentration of active aluminum atoms, and significantly increase the thickness of the aluminized layer. When the low-temperature aluminizing material of the present application is used for aluminizing at a temperature lower than the tempering temperature of the martensitic heat-resistant steel (less than 850 ℃), the matrix structure and mechanical properties will not change.

[0142] The above examples only illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.​​​

Claims

1. A low-temperature aluminizing material suitable for martensitic steel, said low-temperature aluminizing material comprising dry material, characterized in that, The dry material is composed of the following raw materials in parts by weight: 1-5 parts of ammonium chloride 0.5 to 1 part of modified carbon nanotubes 100-200 parts of penetrant; The infiltrator is a mixture of aluminum powder, iron-aluminum powder, alumina powder, and ammonium chloride; The modified carbon nanotubes are prepared by dispersing a silane coupling agent in a solvent, mixing it with carbon nanotubes, separating the solid and liquid phases, and drying to obtain the modified carbon nanotubes. The silane coupling agent is selected from KH-570; The mass-to-volume ratio of the carbon nanotubes and the silane coupling agent is (1.0–2.0):(20–30) mL; The solvent is selected from one or both of toluene and water.

2. The low-temperature aluminizing material as described in claim 1, characterized in that, Includes at least one of the following technical features: The carbon nanotubes described have a length of 2–20 μm and a diameter of 2–30 nm. The drying temperature is 50–80°C.

3. The low-temperature aluminizing material as described in claim 2, characterized in that, The mass ratio of aluminum powder, iron-aluminum powder, alumina powder and ammonium chloride in the penetrant is (5-25):(20-40):(20-65):(1-5).

4. The low-temperature aluminizing material as described in claim 1, characterized in that, The low-temperature aluminizing material also includes a wet material, which is selected from one or two of the binder and diluent.

5. The low-temperature aluminizing material as described in claim 4, characterized in that, The binder is selected from aluminum dihydrogen phosphate; And / or, the diluent is selected from ethanol; And / or, the volume ratio of the adhesive to the diluent is (10-20):(50-80); And / or, the mass-to-volume ratio of the dry material to the wet material is (101.5-206) g: (60-100) mL.

6. The method for preparing the low-temperature aluminizing material according to any one of claims 1-5, characterized in that, Includes the following steps: 1) Activate the penetrant; 2) Mix ammonium chloride, modified carbon nanotubes and activated aluminizing agent to obtain the low-temperature aluminizing material.

7. The preparation method according to claim 6, characterized in that, The activation process is as follows: activation at 800-900°C in a protective atmosphere.

8. An aluminized layer or an article comprising an aluminized layer, characterized in that, The aluminized layer is obtained by coating with the low-temperature aluminizing material according to any one of claims 1-5; the article includes the aluminized layer and a component covered by the aluminized layer, wherein the component is made of martensitic steel.

9. The method for preparing the article as described in claim 8, characterized in that, The low-temperature aluminizing material is sprayed onto the surface of the component, dried and cured, and then heat-treated to aluminize, thus obtaining the product.

10. The preparation method according to claim 9, characterized in that, The drying temperature is 80–100°C; And / or, the drying time is 10 to 20 minutes; And / or, the curing temperature is 200–220°C; And / or, the curing time is 20 to 40 minutes; And / or, the temperature of the heat treatment is 650–700°C; And / or, the heat treatment time is 1 to 6 hours; And / or, the heat treatment is performed in a protective atmosphere.

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