Aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying and coating preparation method

Abstract

The invention discloses aluminum-based amorphous alloy powder for low-temperature high-speed flame spraying and a coating preparation method. According to the method, the aluminum-based amorphous alloy coating containing 4.4-8.4 at.% of rare earth element Y / La / Gd is prepared through low-temperature high-speed flame spraying. The method comprises the following steps: firstly, adding raw materials for preparing the aluminum-based amorphous alloy into a vacuum smelting furnace for smelting, atomizing and screening powder; and then preparing the aluminum-based coating from the prepared powder by adopting a low-temperature high-speed flame spraying process. The amorphous content of the coating is higher than 85%, and the coating has excellent corrosion resistance and wide application prospects.

Description

Technical Field

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

[0002] Aerospace materials need to withstand some extreme environments, such as high-speed flight, pressure changes, and vacuum environments. In particular, when aircraft (such as airplanes) operate over the ocean, some parts (propeller blades, wing parts, etc.) are subject to severe corrosion due to the "three highs" of high salt spray, high humidity and heat, and high sunshine in the marine environment, making it difficult for them to serve for a long time. Therefore, aerospace vehicles not only need to have high strength, light weight, and high temperature resistance, but also need to take into account their corrosion resistance in some cases to ensure the long-term stable and safe operation of the aircraft. How to protect aircraft parts from damage in a corrosive environment has become a focus of attention in recent years.

[0003] Aluminum-based amorphous alloy materials are prepared under ultra-rapid cooling and solidification conditions. Their atomic arrangement is characterized by long-range disorder and short-range order. There are no defects such as grain boundaries and dislocations that often cause corrosion in crystalline materials. They generally have excellent corrosion resistance and high mechanical properties. Since blocky aluminum-based amorphous alloys have poor mechanical properties, high brittleness, low amorphous content, and many internal defects, the coating can avoid these shortcomings, and its lightweight characteristics are more conducive to the engineering application of aluminum-based amorphous alloys. However, the general thermal spraying flame temperature is higher than 2000°C, and the aluminum element will overmelt, oxidize, and crystallize at this temperature. Low-Temperature High-Velocity Air-Fuel (LT-HVAF) is based on supersonic flame spraying (High-Velocity Air-Fuel, HVAF), which reduces the combustion chamber outlet diameter and the kerosene and oxygen ratio, increases the combustion chamber pressure (over 15 bar), and adds cooling media (water, nitrogen, etc.), thereby achieving the purpose of increasing the flame flow speed (up to 700m / s) and reducing the flame temperature (about 1600℃), which can meet the conditions for preparing aluminum-based amorphous coatings.

[0004] The Chinese patent with publication number CN109440048A discloses an ultra-high density aluminum-based amorphous coating and its preparation method. The aluminum-based amorphous coating obtained by HVAF technology has high density and good corrosion resistance. However, the temperature in the coating preparation process of this method is still far higher than the melting point of the aluminum-based amorphous alloy, resulting in an amorphous content of only about 70%, which still has a lot of room for improvement.

[0005] In summary, the existing preparation methods for increasing the amorphous content of aluminum-based amorphous alloy coatings are not reasonable and cannot meet the requirements for preparing coatings with higher amorphous content, resulting in difficulty in improving coating performance. Therefore, starting from the concept of aluminum-based amorphous alloy system design and preparation process, finding a method to increase the amorphous content of aluminum-based amorphous alloy coatings has important academic significance and practical value. Summary of the invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide an aluminum-based amorphous alloy powder for low-temperature high-velocity flame spraying for preparing coatings to solve the shortcoming of low amorphous content in existing thermal sprayed aluminum-based amorphous alloy coatings.

[0007] The second object of the present invention is to provide a method for preparing aluminum-based amorphous alloy powder for low-temperature high-velocity flame spraying.

[0008] The third object of the present invention is to provide a method for preparing a low-temperature high-velocity flame sprayed aluminum-based amorphous alloy coating.

[0009] In order to achieve the above-mentioned purpose, the present invention provides an aluminum-based amorphous alloy powder for low-temperature high-velocity flame spraying, wherein the content of each element in the powder in atomic percentage is: rare earth elements: 5.8-8.4%; Ni: 5-8%; Co: 1.2-2.6%; Al is the balance, wherein the rare earth elements are a combination of 1 to 3 of Y, La, Gd, Ce, and Sc.

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

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

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

[0013] S2. The mixed raw material obtained in step S1 is melted in a vacuum melting furnace to obtain an aluminum-based alloy ingot, and the melting is repeated 5 times. The vacuum degree of the melting chamber during the melting is less than 1.0×10 -5 Pa;

[0014] S3. The aluminum-based alloy ingot obtained in step S2 is subjected to a vacuum gas atomization method to prepare aluminum-based amorphous alloy powder, wherein the atomizing gas is argon gas, and alloy powder having a particle size of 15 μm to 45 μm is screened out through a screening process.

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

[0016] The present invention also provides a method for preparing an aluminum-based amorphous alloy coating by low-temperature high-velocity flame spraying, and the preparation method is specifically carried out in the following steps:

[0017] S1. Substrate pretreatment: Degreasing, rust removal and sand blowing pretreatment of the carbon steel substrate surface;

[0018] S2. Preparation of aluminum-based amorphous alloy coating: spraying the aluminum-based amorphous alloy powder as described in claim 1 or 2 onto the surface of the substrate using a low-temperature high-velocity flame spraying process to obtain an amorphous alloy coating.

[0019] Furthermore, the sand blasting treatment in step S1 is to perform hot sand blasting on the substrate twice and cold sand blasting once, and the sand blasting material is 80-mesh white corundum.

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

[0021] The low-temperature high-velocity flame sprayed aluminum-based amorphous alloy coating prepared by the present invention is prepared by micro-controlling the powder system, adding 4.4-8.4at.% of rare earth elements Y / La / Gd / Ce / Sc, and preparing the coating through LT-HVAF. The coating is well combined with the substrate, has a high amorphous content, low porosity, and excellent corrosion resistance. Preferably, the content of each element in the powder by atomic percentage is: Y / La / Gd: 5.8-8.4%; Ni: 5-8%; Co: 1.2-2.6%; Al is the balance.

[0022] After the powder is sprayed by low-temperature high-velocity flame, the prepared coating has an amorphous content of ≥85% and a porosity of ≤0.5%. It has good corrosion resistance, is easy to industrialize, and has broad application prospects.

[0023] The present invention selects AlNiCoY, AlNiCoYLa and AlNiCoYLaCe amorphous alloy powders with strong amorphous forming ability. The addition of trace rare earth elements significantly increases the absolute value of the mixing enthalpy of the alloy system and improves the amorphous forming ability (GFA). The spraying speed of the process makes the cooling speed of the particles higher than the critical rate of amorphous formation, and nitrogen is used instead of oxygen as the carrier gas to reduce the content of oxides and crystallized phases of the coating. The above reasons make the coating structure evenly distributed, without defects such as structural segregation, and improve the corrosion resistance of the coating.

[0024] The beneficial effects of the present invention are:

[0025] The present invention provides an aluminum-based amorphous alloy powder and a coating preparation method for low-temperature high-velocity flame spraying. The prepared aluminum-based amorphous alloy coating is prepared by adding different rare earth elements and adopting low-temperature high-velocity flame spraying to increase the amorphous content of the aluminum-based amorphous alloy coating; the prepared aluminum-based amorphous alloy coating has a smaller porosity and a higher amorphous content, and has excellent anti-corrosion performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the SEM scanning image of the aluminum-based amorphous alloy powder prepared in Example 1 to Example 3 of the present invention.

[0027] Figure 2 1 is the X-ray diffraction pattern of the aluminum-based amorphous alloy powder prepared in Examples 1 to 3 of the present invention.

[0028] Figure 3 The cross-sectional SEM morphologies of the aluminum-based amorphous alloy coatings prepared in Examples 1 to 3 of the present invention and Comparative Example 1 are shown.

[0029] Figure 4 1 is the X-ray diffraction pattern of the aluminum-based amorphous alloy coating prepared in Examples 1 to 3 of the present invention and Comparative Example 1.

[0030] Figure 5 Potentiodynamic polarization curves of the coatings of Comparative Example 1 and Examples 1, 2 and 3 in 3.5 wt.% NaCl solution. DETAILED DESCRIPTION

[0031] The essential features and significant advantages of the present invention are further illustrated below by way of examples and comparative examples, but the present invention is by no means limited to the described examples.

[0032] Example 1 (addition of Y)

[0033] The composition of the prepared aluminum-based amorphous alloy powder is Al 81 Ni8Co 2.6 Y 8.4(at.%), select high-purity Al (99.99wt.%), Ni (99.95wt.%), Co (99.98wt.%), Y (99.90wt.%), and mix them according to the atomic percentage of the required components, Al: 81%; Ni: 8%; Co: 2.6%; Y: 8.4%; use a vacuum melting furnace to melt to obtain an aluminum-based alloy ingot, and repeat the melting 5 times. The aluminum-based alloy ingot is used to prepare aluminum-based amorphous alloy powder by vacuum gas atomization method, and the aluminum-based amorphous alloy powder with a particle size of 15μm-45μm is screened.

[0034] The surface of the carbon steel substrate is pretreated to remove rust and oil, and then the substrate is hot sandblasted twice and cold sandblasted once. The sandblasting material is 80 mesh white corundum.

[0035] The LT-HVAF technology is used to spray aluminum-based amorphous alloy powder on the substrate surface. The spraying process parameters are set as follows: air pressure 80-85PSI, propane pressure 70-75PSI, nitrogen pressure 20-25PSI, hydrogen pressure 10-12PSI, spray distance 200-250mm, powder feeding rate 14-16g / min, spray gun moving speed 800-1200mm / s. Each spraying (spraying the entire plate once) is cooled for about 10 seconds, and each spraying is an integer multiple of 5 times, and the cooling is 1-2min until the coating thickness reaches 350 microns. The commonly used better parameters are: air pressure 83PSI, propane pressure 74PSI, nitrogen pressure 23PSI, hydrogen pressure 11PSI, spray distance 220mm, powder feeding rate 15g / min, spray gun moving speed 1000mm / s.

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

[0037] The composition of the prepared aluminum-based amorphous alloy powder is Al 85 Ni 6.5 Co 2.5 Y4La2 (at.%), select high-purity Al (99.99wt.%), Ni (99.95wt.%), Co (99.98wt.%), Y (99.90wt.%), La (99.98wt.%), and mix according to the atomic percentage of the required components, Al: 85%; Ni: 6.5%; Co: 2.5%; Y: 4%; La: 2%;; A vacuum melting furnace is used to melt to obtain an aluminum-based alloy ingot, and the melting is repeated 5 times. The aluminum-based alloy ingot is used to prepare aluminum-based amorphous alloy powder by vacuum gas atomization method, and the aluminum-based amorphous alloy powder with a particle size of 15μm-45μm is screened.

[0038] The surface of the carbon steel substrate is pretreated to remove rust and oil, and then the substrate is hot sandblasted twice and cold sandblasted once. The sandblasting material is 80 mesh white corundum.

[0039] The LT-HVAF technology is used to spray aluminum-based amorphous alloy powder on the substrate surface. The spraying process parameters are set as follows: air pressure 80-85PSI, propane pressure 70-75PSI, nitrogen pressure 20-25PSI, hydrogen pressure 10-12PSI, spray distance 200-250mm, powder feeding rate 14-16g / min, spray gun moving speed 800-1200mm / s. Each spraying (spraying the entire plate once) is cooled for about 10 seconds, and each spraying is an integer multiple of 5 times, and the cooling is 1-2min until the coating thickness reaches 350 microns. The commonly used better parameters are: air pressure 83PSI, propane pressure 74PSI, nitrogen pressure 23PSI, hydrogen pressure 11PSI, spray distance 220mm, powder feeding rate 15g / min, spray gun moving speed 1000mm / s.

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

[0041] The prepared aluminum-based amorphous alloy powder composition is Al 88 Ni5Co 1.2 Y2L 1.9 Ce 1.9 (at.%), select high-purity Al (99.99wt.%), Ni (99.95wt.%), Co (99.98wt.%), Y (99.90wt.%), La (99.98wt.%), Ce (99.90wt.%), and mix according to the atomic percentage of the required components, Al: 88%; Ni: 5%; Co: 1.2%; Y: 2%; La: 1.9%; Ce: 1.9% A vacuum melting furnace is used to melt to obtain an aluminum-based alloy ingot, and the melting is repeated 5 times. The aluminum-based alloy ingot is used to prepare aluminum-based amorphous alloy powder by vacuum gas atomization. Aluminum-based amorphous alloy powder with a particle size of 15μm-45μm is obtained by screening.

[0042] The surface of the carbon steel substrate is pretreated to remove rust and oil, and then the substrate is hot sandblasted twice and cold sandblasted once. The sandblasting material is 80 mesh white corundum.

[0043] The LT-HVAF technology is used to spray aluminum-based amorphous alloy powder on the substrate surface. The spraying process parameters are set as follows: air pressure 80-85PSI, propane pressure 70-75PSI, nitrogen pressure 20-25PSI, hydrogen pressure 10-12PSI, spray distance 200-250mm, powder feeding rate 14-16g / min, spray gun moving speed 800-1200mm / s. Each spraying (spraying the entire plate once) is cooled for about 10 seconds, and each spraying is an integer multiple of 5 times, and the cooling is 1-2min until the coating thickness reaches 350 microns. The commonly used better parameters are: air pressure 83PSI, propane pressure 74PSI, nitrogen pressure 23PSI, hydrogen pressure 11PSI, spray distance 220mm, powder feeding rate 15g / min, spray gun moving speed 1000mm / s.

[0044] Comparative Example 1

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

[0046] The surface of the carbon steel substrate is pretreated to remove rust and oil, and then the substrate is 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 on the substrate surface using HVAF technology. The spraying process parameters were set as follows: air pressure 83PSI, propane pressure 80PSI, nitrogen pressure 25PSI, hydrogen pressure 35PSI, spraying distance 200mm, powder feeding rate 15g / min, and spray gun moving speed 800mm / s.

[0048] like Figure 1 The following 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 nearly spherical in structure, smooth and without defects.

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

[0050] Comparing the cross-sectional morphologies of the aluminum-based amorphous alloy coatings in Examples 1 to 3 and Comparative Example 1, Figure 3 As shown. Figure 3 It can be seen that the coatings of Examples 1 to 3 and Comparative Example 1 are well bonded to the substrate, the coatings are tightly overlapped, the porosity is less than 1%, and the coating thickness is more than 300 μm. However, it can be seen that under the same shooting conditions, the color of the aluminum-based amorphous alloy coating in Comparative Example 1 is obviously dark black, indicating that the aluminum-based amorphous alloy coating in Comparative Example 1 is severely oxidized, affecting the long-term corrosion resistance of the coating, and further affecting the long-term use of the equipment sprayed with the coating.

[0051] Figure 4 : is the XRD diffraction pattern of the aluminum-based amorphous alloy coating in Examples 1 to 3 and Comparative Example 1. Figure 4 It can be seen that α-Al phase and Al2O3 phase are observed in the aluminum-based amorphous alloy coatings of Examples 1 to 3 and Comparative Example 1. The amorphous content of the comparative coating calculated by the Verdon method using MDI Jade 6.5 software is about 56%. The XRD diffraction spectrum of the aluminum-based amorphous alloy coating in Examples 1 to 3 has only one broad diffraction peak between 2θ=30 and 50°, with a small amount of crystalline peaks, and the amorphous content is 89%, 86% and 87%, respectively. It shows that the preparation method of the aluminum-based amorphous alloy coating provided by the present invention effectively increases the amorphous content of the aluminum-based amorphous coating.

[0052] contrast Figure 2 It can be seen from the amorphous content of the aluminum-based amorphous alloy powder that the aluminum-based amorphous alloy powder prepared by the method provided by the present invention to the aluminum-based amorphous alloy coating prepared has a reduction in amorphous structure of only 12% at most, while when the coating is prepared by the method in Comparative Example 1, the reduction in amorphous structure can reach 34%, indicating that the coating prepared by the method provided by the present invention can maintain a higher amorphous content.

[0053] The anti-corrosion performance 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 potentiodynamic polarization curves of the four coatings in 3.5wt.% NaCl solution are shown. Figure 5 It can be seen that the range of the cathode polarization and anodic polarization curves of the aluminum-based amorphous alloy coatings prepared in Examples 1 to 3 shows a similar trend to that of the comparative coating, indicating that all four coatings have obvious passivation zones. The self-corrosion current density of comparative example 1 and examples 1, 2, and 3 is 8.15 μA / cm 2 , 2.52μA / cm 2 , 3.37μA / cm 2 and 3.63μA / cm 2It can be seen that the coatings of Examples 1, 2, and 3 have lower self-corrosion current density, and the electrochemical reaction kinetic rate of the surface example coatings in the corrosive solution is smaller, and they have more excellent anti-corrosion performance.

[0054] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An aluminum-based amorphous alloy powder for low-temperature high-velocity flame spraying, characterized in that: The powder contains the following elements in atomic percentage: rare earth elements: 5.8-8.4%; Ni: 5-8%; Co: 1.2-2.6%; Al is the balance, wherein the rare earth elements are a combination of one to three of Y, La, Gd, Ce and Sc.

2. The aluminum-based amorphous alloy powder for low-temperature high-velocity flame spraying according to claim 1, characterized in that: The aluminum-based amorphous alloy powder is spherical or nearly spherical, and has a particle size of 15 μm to 45 μm.

3. A method for preparing aluminum-based amorphous alloy powder for low-temperature high-velocity flame spraying as claimed in claim 1 or 2, characterized in that: The steps include: S1. Mixing raw materials, using high-purity Al, Ni, Co, Y, La, Gd, Ce, Sc, and mixing them according to the atomic percentage of the aluminum-based amorphous alloy components to obtain raw materials; S2. The mixed raw material obtained in step S1 is melted in a vacuum melting furnace to obtain an aluminum-based alloy ingot, and the melting is repeated 5 times. The vacuum degree of the melting chamber during the melting is less than 1.0×10 -5 Pa; S3. The aluminum-based alloy ingot obtained in step S2 is subjected to a vacuum gas atomization method to prepare aluminum-based amorphous alloy powder, wherein the atomizing gas is argon gas, and alloy powder having a particle size of 15 μm to 45 μm is screened out through a screening process.

4. The method for preparing aluminum-based amorphous alloy powder for low-temperature high-velocity flame spraying according to claim 3, characterized in that: In step S1, the purity of Al is 99.99wt.%, the purity of Ni is 99.95wt.%, the purity of Co is 99.98wt.%, the purity of Y is 99.90wt.%, the purity of La is 99.98wt.%, the purity of Gd is 99.90wt.%, the purity of Ce is 99.90wt.%, and the purity of Sc is 99.90wt.%.

5. A method for preparing a low-temperature high-velocity flame sprayed aluminum-based amorphous alloy coating, characterized in that: The preparation method is specifically carried out according to the following steps: S1. Substrate pretreatment: Degreasing, rust removal and sand blowing pretreatment of the carbon steel substrate surface; S2. Preparation of aluminum-based amorphous alloy coating: spraying the aluminum-based amorphous alloy powder as described in claim 1 or 2 onto the surface of the substrate using a low-temperature high-velocity flame spraying process to obtain an amorphous alloy coating.

6. The method for preparing the aluminum-based amorphous alloy coating by low-temperature high-velocity flame spraying according to claim 5, characterized in that: The sand blasting treatment in step S1 is to perform hot sand blasting on the substrate twice and cold sand blasting once, and the sand blasting material is 80-mesh white corundum.

7. The method for preparing the aluminum-based amorphous alloy coating by low-temperature high-velocity flame spraying according to claim 5, characterized in that: The process parameters of the low-temperature high-speed flame spraying in step S2 are: air pressure 80-85PSI, propane pressure 70-75PSI, nitrogen pressure 20-25psi, hydrogen pressure 10-12psi, spraying distance 200-250mm, powder feeding rate 14-16g / min, spray gun moving speed 800-1200mm / s; cooling for 10 seconds after each complete spraying, cooling for 1-2min after each integral multiple of 5 complete sprayings, until the coating thickness reaches 350 microns.

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