A method for preparing aluminum-based amorphous alloy powder and coating for low-temperature high-speed flame spraying.

Abstract

This invention discloses an aluminum-based amorphous alloy powder and coating preparation method for low-temperature high-speed flame spraying. The method involves preparing an aluminum-based amorphous alloy coating containing 5.8-8.4 at.% rare earth elements Y / La / Gd using low-temperature high-speed flame spraying. First, the raw materials for preparing the aluminum-based amorphous alloy are added to a vacuum melting furnace for melting, atomization, and powder screening. Then, the prepared powder is used to prepare an aluminum-based coating using a low-temperature high-speed flame spraying process. The coating provided by this invention has an amorphous content higher than 85%, exhibits excellent corrosion resistance, and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-based amorphous alloy technology, and relates to a method for preparing aluminum-based amorphous alloy powder and coating for low-temperature high-speed flame spraying. Background Technology

[0002] Aerospace materials need to withstand extreme environments, such as high-speed flight, pressure changes, and vacuum environments. Especially for aircraft operating over the ocean, the high salt spray, high humidity and heat, and high sunlight of the marine environment cause severe corrosion to some components (propeller blades, wing parts, etc.), making long-term service unsustainable. Therefore, aerospace vehicles not only need high strength, lightweight, and high-temperature resistance, but in some cases, corrosion resistance is also necessary to ensure long-term stable and safe operation. Protecting aircraft components from corrosive environments has become a focus of attention in recent years.

[0003] Aluminum-based amorphous alloys are prepared under ultra-rapid solidification conditions. Their atomic arrangement exhibits long-range disorder and short-range order, and they lack the grain boundaries and dislocations that often cause corrosion in crystalline materials. They generally possess excellent corrosion resistance and high mechanical properties. However, bulk aluminum-based amorphous alloys have poor mechanical properties, are brittle, and suffer from low amorphous content and numerous internal defects. Coatings can avoid these drawbacks, and their lightweight nature facilitates the engineering applications of aluminum-based amorphous alloys. However, typical thermal spraying flame temperatures exceed 2000℃, at which point aluminum undergoes overmelting, oxidation, and crystallization. Low-Temperature High-Velocity Air-Fuel (LT-HVAF) is based on High-Velocity Air-Fuel (HVAF). It reduces the combustion chamber outlet diameter and the kerosene-to-oxygen ratio, increases the combustion chamber pressure (over 15 bar), and adds a cooling medium (water, nitrogen, etc.). This achieves the goal of increasing the flame velocity (up to 700 m / s) and reducing the flame temperature (approximately 1600 °C), thus meeting the conditions for preparing aluminum-based amorphous coatings.

[0004] Chinese patent CN109440048A discloses an ultra-high density aluminum-based amorphous coating and its preparation method. The HVAF technology yields an aluminum-based amorphous coating with high density and good corrosion resistance. However, the temperature during coating preparation still far exceeds the melting point of the aluminum-based amorphous alloy, resulting in an amorphous content of only about 70%, indicating significant room for improvement.

[0005] In summary, existing methods for increasing the amorphous content of aluminum-based amorphous alloy coatings are not entirely reasonable and cannot achieve high amorphous content coatings, thus hindering performance improvement. Therefore, exploring methods to increase the amorphous content of aluminum-based amorphous alloy coatings, starting from the design and preparation process of aluminum-based amorphous alloy systems, has significant academic and practical value. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a powder for low-temperature high-speed flame spraying of aluminum-based amorphous alloys for preparing coatings, thereby overcoming the shortcomings of existing thermally sprayed aluminum-based amorphous alloy coatings with low amorphous content.

[0007] The second objective of this invention is to provide a method for preparing aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying.

[0008] The third objective of this invention is to provide a method for preparing a low-temperature, high-speed flame-sprayed aluminum-based amorphous alloy coating.

[0009] To achieve the above objectives, the present invention provides an aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying. The powder contains the following elements by atomic percentage: rare earth elements: 5.8-8.4%; Ni: 5-8%; Co: 1.2-2.6%; Al as the balance, wherein the rare earth elements are a combination of one to three of Y, La, Gd, Ce, and Sc.

[0010] Furthermore, the aluminum-based amorphous alloy powder is spherical or near-spherical with a particle size of 15μm to 45μm.

[0011] The present invention also provides a method for preparing the above-mentioned aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying, comprising the following steps:

[0012] S1. Prepare the raw materials by using high-purity Al, Ni, Co, Y, La, Gd, Ce, and Sc, and mixing them according to the atomic percentage ratio of the aluminum-based amorphous alloy composition.

[0013] S2. The mixed raw materials obtained in step S1 are melted in a vacuum melting furnace to obtain aluminum-based alloy ingots. The melting process is repeated 5 times, with the vacuum degree of the melting chamber being less than 1.0 × 10⁻⁶ during the melting process. -5 Pa;

[0014] S3. The aluminum-based alloy ingot obtained in step S2 is used to prepare aluminum-based amorphous alloy powder by vacuum gas atomization. The atomizing gas is argon. Alloy powder with a particle size of 15μm to 45μm is screened by sieving process.

[0015] Furthermore, in step S1, the purity of Al is 99.99 wt.%, the purity of Ni is 99.95 wt.%, the purity of Co is 99.98 wt.%, the purity of Y is 99.90 wt.%, the purity of La is 99.98 wt.%, the purity of Gd is 99.90 wt.%, the purity of Ce is 99.90 wt.%, and the purity of Sc is 99.90 wt.%.

[0016] This invention also provides a method for preparing a low-temperature, high-speed flame-sprayed aluminum-based amorphous alloy coating, which specifically comprises the following steps:

[0017] S1. Substrate pretreatment: The carbon steel substrate surface is pretreated by degreasing, rust removal and sandblasting;

[0018] S2. Preparation of aluminum-based amorphous alloy coating: The aluminum-based amorphous alloy powder as described above is sprayed onto the substrate surface using a low-temperature high-speed flame spraying process to obtain an amorphous alloy coating.

[0019] Furthermore, the sandblasting process in step S1 involves hot sandblasting the substrate twice and cold sandblasting once, with the sandblasting material being 80-mesh white corundum.

[0020] Furthermore, the process parameters for low-temperature high-speed flame spraying in step S2 are as follows: air pressure 80-85 PSI, propane pressure 70-75 PSI, nitrogen pressure 20-25 psi, hydrogen pressure 10-12 psi, spraying distance 200-250 mm, powder feed rate 14-16 g / min, and spray gun moving speed 800-1200 mm / s; cooling for 10 seconds after each complete spraying pass, and for every 5 complete spraying passes, cooling for 1-2 minutes, until the coating thickness reaches 350 micrometers.

[0021] The low-temperature high-speed flame-sprayed aluminum-based amorphous alloy coating prepared by this invention involves microscopic control of the powder system, adding 5.8-8.4 at.% of rare earth elements Y / La / Gd / Ce / Sc, and preparing the coating via LT-HVAF. The coating exhibits good adhesion to the substrate, high amorphous content, low porosity, and excellent corrosion resistance. Preferably, the atomic percentage content of each element in the powder is: Y / La / Gd: 5.8-8.4%; Ni: 5-8%; Co: 1.2-2.6%; Al as the balance.

[0022] After the powder is sprayed with a low-temperature high-speed flame, the resulting coating has an amorphous content of ≥85% and a porosity of ≤0.5%, exhibiting good corrosion resistance, easy industrialization, and broad application prospects.

[0023] This invention selects AlNiCoY, AlNiCoYLa, and AlNiCoYLaCe amorphous alloy powders with strong amorphous forming ability. The addition of trace amounts of rare earth elements significantly increases the absolute value of the mixing enthalpy of the alloy system, thereby improving the amorphous forming ability (GFA). The spraying speed of this process allows the particles to cool at a rate higher than the critical rate for amorphous formation, and the use of nitrogen instead of oxygen as the carrier gas reduces the content of oxides and crystalline phases in the coating. These factors result in a uniform coating structure distribution, the absence of defects such as structural segregation, and improved corrosion resistance.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention provides an aluminum-based amorphous alloy powder and coating preparation method for low-temperature high-speed flame spraying. The prepared aluminum-based amorphous alloy coating has an increased amorphous content by adding different rare earth elements and using low-temperature high-speed flame spraying. The prepared aluminum-based amorphous alloy coating has a small porosity and a high amorphous content, and excellent corrosion resistance. Attached Figure Description

[0026] Figure 1 The images shown are SEM scans of the aluminum-based amorphous alloy powders prepared in Examples 1 to 3 of this invention.

[0027] Figure 2 The X-ray diffraction patterns are those of the aluminum-based amorphous alloy powders prepared in Examples 1 to 3 of the present invention.

[0028] Figure 3 The images show the cross-sectional SEM morphology of the aluminum-based amorphous alloy coatings prepared in Examples 1 to 3 and Comparative Example 1 of this invention.

[0029] Figure 4 The X-ray diffraction patterns are those of the aluminum-based amorphous alloy coatings prepared in Examples 1 to 3 and Comparative Example 1 of the present invention.

[0030] Figure 5 The potentiodynamic polarization curves of the coatings in Comparative Example 1 and Examples 1, 2, and 3 in 3.5 wt.% NaCl solution are shown. Detailed Implementation

[0031] The essential features and significant advantages of the present invention are further illustrated below through examples and comparative examples. The present invention is by no means limited to the examples stated herein.

[0032] Example 1 (with Y added)

[0033] The prepared aluminum-based amorphous alloy powder has the following composition: Al 81 Ni8Co 2.6 Y 8.4(at.%), high-purity Al (99.99 wt.%), Ni (99.95 wt.%), Co (99.98 wt.%), and Y (99.90 wt.%) were selected and formulated according to the required atomic percentage ratios: Al: 81%; Ni: 8%; Co: 2.6%; Y: 8.4%. Aluminum-based alloy ingots were obtained by vacuum melting in a furnace, and the melting process was repeated five times. Aluminum-based amorphous alloy powder was prepared from the aluminum-based alloy ingots using a vacuum gas atomization method, and the powder was screened to obtain a particle size of 15 μm-45 μm.

[0034] The carbon steel substrate surface is pretreated by removing rust and oil, and then hot sandblasted twice and cold sandblasted once. The sandblasting material is 80-mesh white corundum.

[0035] Aluminum-based amorphous alloy powder is sprayed onto the substrate surface using LT-HVAF technology. The spraying process parameters are set as follows: air pressure 80-85 PSI, propane pressure 70-75 PSI, nitrogen pressure 20-25 PSI, hydrogen pressure 10-12 PSI, spraying distance 200-250 mm, powder feed rate 14-16 g / min, and spray gun movement speed 800-1200 mm / s. Each coat (one coat for the entire board) is allowed to cool for approximately 10 seconds. For every five coats, a cooling period of 1-2 minutes is allowed until the coating thickness reaches 350 micrometers. The commonly used optimal parameters are: air pressure 83 PSI, propane pressure 74 PSI, nitrogen pressure 23 PSI, hydrogen pressure 11 PSI, spraying distance 220 mm, powder feed rate 15 g / min, and spray gun movement speed 1000 mm / s.

[0036] Example 2 (with the addition of Y and La)

[0037] The prepared aluminum-based amorphous alloy powder has the following composition: Al 85 Ni 6.5 Co 2.5 Y4La2 (at.%) was prepared by selecting high-purity Al (99.99 wt.%), Ni (99.95 wt.%), Co (99.98 wt.%), Y (99.90 wt.%), and La (99.98 wt.%), and formulating the components according to the required atomic percentage ratio: Al: 85%; Ni: 6.5%; Co: 2.5%; Y: 4%; La: 2%. The aluminum-based alloy ingot was obtained by vacuum melting in a furnace and the melting process was repeated five times. The aluminum-based alloy ingot was then used to prepare aluminum-based amorphous alloy powder using a vacuum gas atomization method, and the powder was screened to obtain an aluminum-based amorphous alloy powder with a particle size of 15 μm-45 μm.

[0038] The carbon steel substrate surface is pretreated by removing rust and oil, and then hot sandblasted twice and cold sandblasted once. The sandblasting material is 80-mesh white corundum.

[0039] Aluminum-based amorphous alloy powder is sprayed onto the substrate surface using LT-HVAF technology. The spraying process parameters are set as follows: air pressure 80-85 PSI, propane pressure 70-75 PSI, nitrogen pressure 20-25 PSI, hydrogen pressure 10-12 PSI, spraying distance 200-250 mm, powder feed rate 14-16 g / min, and spray gun movement speed 800-1200 mm / s. Each coat (one coat for the entire board) is allowed to cool for approximately 10 seconds. For every five coats, a cooling period of 1-2 minutes is allowed until the coating thickness reaches 350 micrometers. The commonly used optimal parameters are: air pressure 83 PSI, propane pressure 74 PSI, nitrogen pressure 23 PSI, hydrogen pressure 11 PSI, spraying distance 220 mm, powder feed rate 15 g / min, and spray gun movement speed 1000 mm / s.

[0040] Example 3 (with addition of Y, La, and Ce)

[0041] The prepared aluminum-based amorphous alloy powder has an Al composition. 88 Ni5Co 1.2 Y2La 1.9 Ce 1.9 (at.%), high-purity Al (99.99 wt.%), Ni (99.95 wt.%), Co (99.98 wt.%), Y (99.90 wt.%), La (99.98 wt.%), and Ce (99.90 wt.%) were selected and formulated according to the required atomic percentage ratio: Al: 88%; Ni: 5%; Co: 1.2%; Y: 2%; La: 1.9%; Ce: 1.9%. The aluminum-based alloy ingot was obtained by vacuum melting in a furnace and the melting process was repeated five times. The aluminum-based alloy ingot was then used to prepare aluminum-based amorphous alloy powder using a vacuum gas atomization method. The powder was then screened to obtain aluminum-based amorphous alloy powder with a particle size of 15 μm-45 μm.

[0042] The carbon steel substrate surface is pretreated by removing rust and oil, and then hot sandblasted twice and cold sandblasted once. The sandblasting material is 80-mesh white corundum.

[0043] Aluminum-based amorphous alloy powder is sprayed onto the substrate surface using LT-HVAF technology. The spraying process parameters are set as follows: air pressure 80-85 PSI, propane pressure 70-75 PSI, nitrogen pressure 20-25 PSI, hydrogen pressure 10-12 PSI, spraying distance 200-250 mm, powder feed rate 14-16 g / min, and spray gun movement speed 800-1200 mm / s. Each coat (one coat for the entire board) is allowed to cool for approximately 10 seconds. For every five coats, a cooling period of 1-2 minutes is allowed until the coating thickness reaches 350 micrometers. The commonly used optimal parameters are: air pressure 83 PSI, propane pressure 74 PSI, nitrogen pressure 23 PSI, hydrogen pressure 11 PSI, spraying distance 220 mm, powder feed rate 15 g / min, and spray gun movement speed 1000 mm / s.

[0044] Comparative Example 1

[0045] This comparative example uses a non-optimal parameter range to compare and verify the influence of spraying process parameters on coating results and performance.

[0046] The carbon steel substrate surface is pretreated by removing rust and oil, and then hot sandblasted twice and cold sandblasted once. The sandblasting material is 80-mesh white corundum.

[0047] The aluminum-based amorphous alloy powder prepared in Example 1 was sprayed onto the substrate surface using HVAF technology. The spraying process parameters were set as follows: air pressure 83 PSI, propane pressure 80 PSI, nitrogen pressure 25 PSI, hydrogen pressure 35 PSI, spraying distance 200 mm, powder feeding rate 15 g / min, and spray gun moving speed 800 mm / s.

[0048] like Figure 1 The images shown are scanning electron microscope (SEM) images of the aluminum-based amorphous alloy powders prepared in Examples 1 to 3. Figure 1 It can be seen that the aluminum-based amorphous alloy powders prepared in Examples 1 to 3 are mostly spherical or near-spherical in shape, and are smooth and without defects.

[0049] like Figure 2 The image shows the XRD diffraction patterns of the aluminum-based amorphous alloy powders prepared in Examples 1 to 3. The amorphous content was calculated using the Verdon method with MDIJade 6.5 software. Figure 2 It can be seen that the amorphous content of the aluminum-based amorphous alloy powder prepared in Example 1 is as high as 90%, the amorphous content of the aluminum-based amorphous alloy powder prepared in Example 2 is as high as 98%, and the amorphous content of the aluminum-based amorphous alloy powder prepared in Example 3 is as high as 95%.

[0050] The cross-sectional morphology of the aluminum-based amorphous alloy coatings in Examples 1 to 3 and Comparative Example 1 are compared, such as Figure 3 As shown. From Figure 3 It can be seen that the coatings of Examples 1 to 3 and Comparative Example 1 all exhibit good adhesion to the substrate, with tight internal overlap, porosity below 1%, and coating thickness exceeding 300 μm. However, it can be observed that under the same shooting conditions, the aluminum-based amorphous alloy coating in Comparative Example 1 is significantly darker, indicating severe oxidation of the coating, which affects its long-term corrosion resistance and consequently the long-term use of the equipment used to apply the coating.

[0051] Figure 4 The images show the XRD diffraction patterns of the aluminum-based amorphous alloy coatings in Examples 1 to 3 and Comparative Example 1. Figure 4 It can be seen that α-Al and Al2O3 phases were observed in the aluminum-based amorphous alloy coatings of Examples 1 to 3 and Comparative Example 1. The amorphous phase content of the comparative example coating was calculated to be approximately 56% using the Verdon method with MDI Jade 6.5 software. In contrast, the XRD diffraction patterns of the aluminum-based amorphous alloy coatings in Examples 1 to 3 showed only one broad diffraction peak between 2θ = 30 and 50°, with a small amount of crystalline peaks present, and amorphous contents of 89%, 86%, and 87%, respectively. This indicates that the preparation method of the aluminum-based amorphous alloy coating provided by this invention effectively improves the amorphous content of the aluminum-based amorphous coating.

[0052] contrast Figure 2 The amorphous content of the aluminum-based amorphous alloy powder shows that the amorphous structure of the aluminum-based amorphous alloy powder prepared by the method provided in this invention is reduced by a maximum of only 12% to the prepared aluminum-based amorphous alloy coating. However, the amorphous structure of the coating prepared by the method in Comparative Example 1 can be reduced by up to 34%, indicating that the coating prepared by the method provided in this invention can retain a higher amorphous content.

[0053] The corrosion resistance of the aluminum-based amorphous alloy coatings prepared in Examples 1 to 3 and Comparative Example 1 was evaluated using potentiodynamic polarization curves. Figure 5 The figure shows the potentiodynamic polarization curves of four coatings in a 3.5 wt.% NaCl solution. From... Figure 5 It can be seen that the cathodic and anodic polarization curves of the aluminum-based amorphous alloy coatings prepared in Examples 1 to 3 show a similar trend to those of the comparative example coatings, indicating that all four coatings have obvious passivation regions. The self-corrosion current densities of Comparative Example 1 and Examples 1, 2, and 3 are 8.15 μA / cm². 2 2.52μA / cm 2 3.37μA / cm 2 and 3.63 μA / cm 2It can be seen that the coatings of Examples 1, 2, and 3 have lower self-corrosion current densities, and the coatings of the surface examples have lower electrochemical reaction kinetic rates in the corrosive solution, exhibiting superior anti-corrosion performance.

[0054] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying, characterized in that: The powder contains the following elemental percentages by atomic percentage: rare earth elements: 5.8-8.4%; Ni: 5-8%; Co: 1.2-2.6%; Al as the balance, with rare earth elements being Y, La, and Ce; the aluminum-based amorphous alloy powder is spherical or near-spherical with a particle size of 15μm~45μm; the amorphous content in the powder is 95%; the preparation method of this aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying includes the following steps: S1. Produce raw material proportions by using high-purity Al, Ni, Co, Y, La, and Ce, and mixing them according to the atomic percentage of the aluminum-based amorphous alloy composition to obtain the raw materials; S2. The mixed raw materials obtained in step S1 are melted in a vacuum melting furnace to obtain aluminum-based alloy ingots. The melting process is repeated 5 times, with the vacuum degree of the melting chamber being less than 1.0 × 10⁻⁶ during the melting process. -5 Pa; S3. The aluminum-based alloy ingot obtained in step S2 is used to prepare aluminum-based amorphous alloy powder by vacuum gas atomization. The atomizing gas is argon. Alloy powder with a particle size of 15μm to 45μm is screened by sieving process. The process parameters for the low-temperature high-speed flame spraying are as follows: air pressure 80-85 PSI, propane pressure 70-75 PSI, nitrogen pressure 20-25 psi, hydrogen pressure 10-12 psi, spraying distance 200-250 mm, powder feed rate 14-16 g / min, and spray gun moving speed 800-1200 mm / s; cooling for 10 seconds after each complete spraying pass, and for every 5 complete spraying passes, cooling for 1-2 minutes, until the coating thickness reaches 350 micrometers.

2. The aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying according to claim 1, characterized in that: In step S1, the purity of Al is 99.99 wt.%, the purity of Ni is 99.95 wt.%, the purity of Co is 99.98 wt.%, the purity of Y is 99.90 wt.%, the purity of La is 99.98 wt.%, and the purity of Ce is 99.90 wt.%.

3. A method for preparing a low-temperature, high-speed flame-sprayed aluminum-based amorphous alloy coating, characterized in that: The preparation method is carried out according to the following steps: S(1). Substrate pretreatment: The carbon steel substrate surface is pretreated by degreasing, rust removal and sandblasting; S(2). Preparation of aluminum-based amorphous alloy coating: The aluminum-based amorphous alloy powder as described in claim 1 or 2 is sprayed onto the surface of the substrate to obtain an amorphous alloy coating by a low-temperature high-speed flame spraying process; Among them, the sandblasting pretreatment in step S(1) is to hot sandblast the substrate twice and cold sandblast once, and the sandblasting material is 80-mesh white corundum; The process parameters for low-temperature high-speed flame spraying in step S(2) are as follows: air pressure 80-85 PSI, propane pressure 70-75 PSI, nitrogen pressure 20-25 psi, hydrogen pressure 10-12 psi, spraying distance 200-250 mm, powder feeding rate 14-16 g / min, and spray gun moving speed 800-1200 mm / s; cooling for 10 seconds after each complete spraying, and for every 5 complete sprayings, cooling for 1-2 minutes until the coating thickness reaches 350 micrometers.

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