Boride reinforced light refractory high-entropy alloy coating and preparation method thereof

Abstract

The invention provides a boride reinforced light refractory high-entropy alloy coating, and belongs to the technical field of alloy surface coating modification. The preparation method comprises the following steps: (1) preparing the following components in atomic percent: 24.39-25% of Al; the content of Nb is 24.39 to 25 percent; ti: 24.39%-25%; v: 24.39% to 25%; b, weighing 0-2.44% of each powder, mixing, and carrying out ball milling to obtain mixed alloy powder; (2) the surface of the titanium alloy matrix is pretreated; and (3) the mixed alloy powder is dried and then preset on the surface of a pretreated titanium alloy matrix to form a prefabricated layer, then laser cladding is conducted to obtain the boride reinforced light refractory high-entropy alloy coating, metallurgical bonding is formed between the coating and the matrix, obvious cracks and holes do not exist, the macroscopic morphology is good, the microstructure is mainly a dendritic structure, and the heat conductivity is high. The above shows that an expected effect is achieved. The high-entropy alloy coating obtained by the process improves the strength and wear resistance of the titanium alloy, so that the high-entropy alloy coating can be applied to aerospace, rail transit or marine ships and has a wider application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy surface coating modification, and in particular relates to a boride-reinforced lightweight refractory high-entropy alloy coating and a preparation method thereof. Background Art

[0002] Titanium alloys are widely used in aerospace and many other fields due to their low density, high specific strength, small specific modulus, and good high temperature resistance. However, they have poor wear resistance, low hardness, and poor thermal conductivity. When the operating temperature exceeds 650°C, their surface will be severely oxidized, thus affecting their service life and application range. Therefore, titanium alloy surface modification has always been a hot topic in the field of surface engineering.

[0003] Laser cladding technology refers to a process in which powder is heated by a laser beam in different conveying modes and then coated on the surface of a substrate, and a surface coating that is metallurgically bonded with the substrate material is formed, thereby improving the hardness, strength, wear resistance, corrosion resistance, heat resistance, and oxidation resistance of the substrate material. Compared with other surface modification technologies, laser cladding has a high laser energy density, a low dilution rate, and can form a good metallurgical bond between the coating and the substrate. Moreover, since the laser cladding process is a process of rapid heating and rapid cooling, its solidification rate is as high as 103-106℃ / s, so it is easy to obtain a dense fine-grained structure or even an amorphous phase.

[0004] Therefore, there is a need for a coating with high hardness and good wear resistance that can be prepared using laser cladding technology, which can enable TC4 to adapt to complex service environments. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a boride-reinforced lightweight refractory high-entropy alloy coating and a preparation method thereof. The AlNbTiVBx high-entropy alloy coating of the present invention has high bonding strength with the substrate, small thermal deformation of the substrate, low dilution rate, and high hardness.

[0006] In order to achieve the above object, the present invention provides a boride reinforced lightweight refractory high entropy alloy coating, which is prepared from the following atomic percentage powders:

[0007] Al: 24.39~25%; Nb: 24.39~25%; Ti: 24.39~25%; V: 24.39~25%; B: 0~2.44%. .

[0008] In the present invention, the above components are used to improve the performance of titanium alloy, wherein boron is a lightweight element, which has a significant solid solution strengthening effect when added to the alloy, and boron mainly exists in the alloy in the form of solid solution and boride. During the laser cladding process, the boron element has a deoxidation and slag-forming effect, which can well improve the morphology and structure of the coating, and avoid the generation of defects such as impurities and pores caused by oxidation. Because boron and titanium have a large negative mixing enthalpy, TiB2 will be generated to enhance the strength of the high entropy alloy coating, thereby improving the performance of the titanium alloy to a greater extent.

[0009] The present invention also provides a method for preparing the above-mentioned boride reinforced lightweight refractory high entropy alloy coating, comprising the following steps:

[0010] 1) weighing the powder raw materials according to the atomic percentage, mixing and ball milling to obtain a mixed alloy powder;

[0011] 2) The mixed alloy powder is dried and pre-placed on the substrate surface to form a prefabricated layer, and then laser cladding is performed to obtain a boride-reinforced lightweight refractory high-entropy alloy coating.

[0012] Preferably, each powder raw material is a spherical powder with a purity of ≥99.99% and a particle size of 100 to 200 meshes.

[0013] Preferably, the ball milling in step (1) is performed using a planetary ball mill; the rotation speed of the planetary ball mill is 180 to 200 rpm, the ball-to-material ratio is 4:1, and the ball milling time is 5 to 8 hours.

[0014] Preferably, the titanium alloy matrix is ​​Ti-6A1-4V.

[0015] Preferably, in step (2), the drying temperature is 90° C. and the drying time is 3 to 5 hours.

[0016] Preferably, the laser cladding parameters in step (2) are as follows: laser power is 1300W, scanning speed is 300mm / min -1 , the spot diameter is 4 mm, the protective gas is argon, and the gas flow rate is 10 L / min.

[0017] The beneficial effects of the present invention include at least:

[0018] (1) The AlNbTiVBx high entropy alloy coating in the present invention forms a good metallurgical bond with the substrate, the substrate and the cladding layer have a high bonding strength, and the thermal deformation of the substrate is small and the dilution rate is low.

[0019] (2) The AlNbTiVBx high entropy alloy cladding layer of the present invention has a uniform dendrite structure, and the cladding layer has high hardness, high temperature oxidation resistance and corrosion resistance.

[0020] (3) The raw material system in the present invention can be adapted to the laser cladding technology. The laser cladding method is highly automated in preparing the coating and can also accurately control the surface properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning cross-sectional macroscopic morphology image of Example 1.

[0022] Figure 2 This is the dendrite scanning morphology of Example 2.

[0023] Figure 3 The microhardness variation diagram of Examples 1 to 3. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0026] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0027] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0029] The raw material powder used in the following examples is a spherical powder with a purity of ≥99.99% and a particle size of 100 to 200 meshes.

[0030] Example 1

[0031] A method for preparing a powder of a boride-reinforced lightweight high-entropy alloy coating comprises the following steps:

[0032] (1) According to the components and their atomic percentages, 25.0% Al, 25.0% Nb, 25.0% Ti, and 25.0% V were placed in a planetary ball mill for ball milling. The ball milling method was dry grinding. The ball milling speed was 180 rpm, the ball-to-material ratio was 4:1, and the ball milling time was 5 h to obtain a composite powder.

[0033] (2) Pretreatment of the titanium alloy substrate surface: Use 300-grit sandpaper to grind the oxide layer and impurities on the substrate surface, and then use alcohol ultrasonic cleaning and blow drying for later use.

[0034] (3) The ball-milled composite powder was placed in a drying oven at 90°C for 3-5 hours, and then the powder was pre-placed on the substrate surface to form a prefabricated layer of 1.0-1.5 mm, followed by laser cladding, wherein the laser power was 1300 W and the scanning speed was 300 mm / min. -1 , the spot diameter is 4 mm, the protective gas is argon, and the gas flow rate is 10 L / min.

[0035] Example 2

[0036] A method for preparing a powder of a boride-reinforced lightweight high-entropy alloy coating comprises the following steps:

[0037] (1) The high entropy alloy material described in this embodiment is composed of five metal element powders of Al, Nb, Ti, V, and B. The components and their atomic percentages are 24.69% Al, 24.69% Nb, 24.69% Ti, 24.69% V, and 1.23% B. Each powder is weighed using an electronic balance. Then, each powder is placed in a planetary ball mill and ball milled. The ball milling method is dry milling, the ball milling speed is 180-200 rpm, the ball-to-material ratio is 4:1, and the ball milling time is 5-8 hours, and then a composite powder is obtained.

[0038] (2) Pretreatment of the titanium alloy substrate surface: Use 300-grit sandpaper to grind the oxide layer and impurities on the substrate surface, and then use alcohol ultrasonic cleaning and blow drying for later use.

[0039] (3) The ball-milled composite powder was placed in a drying oven at 90°C for 3-5 hours, and then the powder was pre-placed on the substrate surface to form a prefabricated layer of 1.0-1.5 mm, followed by laser cladding, wherein the laser power was 1300 W and the scanning speed was 300 mm / min.-1 , the spot diameter is 4 mm, the protective gas is argon, and the gas flow rate is 10 L / min.

[0040] Example 3

[0041] A method for preparing a powder of a boride-reinforced lightweight high-entropy alloy coating comprises the following steps:

[0042] (1) The high entropy alloy material described in this embodiment is composed of five metal element powders of Al, Nb, Ti, V, and B. The components and their atomic percentages are 24.39% Al, 24.39% Nb, 24.39% Ti, 24.39% V, and 2.44% B. Each powder is weighed using an electronic balance. Then, each powder is placed in a planetary ball mill and ball milled. The ball milling method is dry milling, the ball milling speed is 180-200 rpm, the ball-to-material ratio is 4:1, and the ball milling time is 5-8 hours, and then a composite powder is obtained.

[0043] (2) Pretreatment of the titanium alloy substrate surface: Use 300-grit sandpaper to grind the oxide layer and impurities on the substrate surface, and then use alcohol ultrasonic cleaning and blow drying for later use.

[0044] (3) The ball-milled composite powder was placed in a drying oven at 90°C for 3-5 hours, and then the powder was pre-placed on the substrate surface to form a prefabricated layer of 1.0-1.5 mm, followed by laser cladding, wherein the laser power was 1300 W and the scanning speed was 300 mm / min. -1 , the spot diameter is 4 mm, the protective gas is argon, and the gas flow rate is 10 L / min.

[0045] Experimental Example 1

[0046] The cladding layers obtained in Examples 1 and 2 were ground and polished with 600-3000 grit sandpaper and photographed with a scanning electron microscope. Figure 1-2 As shown, the coating has a complete macroscopic appearance, forms a good metallurgical bond with the substrate, and the cladding layer has no obvious defects.

[0047] For the cladding layers obtained in Examples 1 to 3, 5 points were selected at different positions on the substrate and the coating to measure the hardness, and the average value was taken after removing the maximum and minimum values. The experimental results are shown in Table 1.

[0048] Table 1

[0049]

[0050] According to the test results of Example 1, the AlNbTiV system coating significantly improves the hardness of the TC4 substrate compared with the substrate; according to the test results of Examples 2-3, the hardness of the coating is improved after adding the B element, which is mainly because B and Ti have a large mixing enthalpy to generate a brittle and hard second phase TiB2.

[0051] The parameters of the cladding layers obtained in Examples 1 to 3 are shown in Table 2.

[0052] Table 2

[0053]

[0054] It is determined through various parameters that each powder in the present invention forms a high entropy alloy coating on the surface of the titanium alloy substrate after laser cladding.

[0055] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A boride-reinforced lightweight refractory high-entropy alloy coating, characterized in that: Prepared from powders with the following atomic percentages: Al: 24.39~25%; Nb: 24.39~25%; Ti: 24.39~25%; V: 24.39~25%; B: 0~2.44%.

2. The method for preparing the boride-reinforced lightweight refractory high-entropy alloy coating according to claim 1, characterized in that: The following steps are involved: 1) weighing the powder raw materials according to the atomic percentage, mixing and ball milling to obtain a mixed alloy powder; 2) pretreating the surface of the titanium alloy substrate; 3) After drying, the mixed alloy powder is pre-placed on the surface of the pretreated titanium alloy substrate to form a prefabricated layer, and then laser cladding is performed to obtain a boride-reinforced lightweight refractory high-entropy alloy coating.

3. The preparation method according to claim 2, characterized in that: The powder raw materials are spherical powders with a purity of ≥99.99% and a particle size of 100-200 meshes.

4. The preparation method according to claim 2, characterized in that: In the step (1), a planetary ball mill is used for ball milling; the rotation speed of the planetary ball mill is 180-200 rpm, the ball-to-material ratio is 4:1, and the ball milling time is 5-8 hours.

5. The preparation method according to claim 2, characterized in that: The titanium alloy substrate pretreatment method in step (2) is: using 300-mesh sandpaper to grind the oxide layer and impurities on the surface of the substrate, and then ultrasonically cleaning with alcohol and blowing dry.

6. The preparation method according to claim 2 or claim 5, characterized in that: The titanium alloy matrix is ​​Ti-6A1-4V.

7. The preparation method according to claim 2, characterized in that: In the step (3), the drying temperature is 90° C. and the drying time is 3 to 5 hours.

8. The preparation method according to claim 2, characterized in that: The laser cladding parameters in step (3) are as follows: laser power is 1300W, scanning speed is 300mm / min -1 , the spot diameter is 4 mm, the protective gas is argon, and the gas flow rate is 10 L / min.

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