multi-principal element Al- Co- Cr- Cu- Fe- Ni high-entropy alloy (HEA) coating and preparation method thereof

Abstract

Disclosed is a multi-principal element Al—Co—Cr—Cu—Fe—Ni high-entropy alloy (HEA) coating. The multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating includes metal elements Al, Cu, Co, Cr, Fe, and Ni in a molar ratio of Al:Cu:Co:Cr:Fe:Ni of 0.7:0.3:1:1:1:1. Raw materials for Al and Cu are metal powders. A raw material for Co, Cr, Fe, and Ni is a CoCrFeNi alloy powder. A molar ratio of Co, Cr, Fe, and Ni in the CoCrFeNi alloy powder is 1:1:1.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This patent application claims the benefit and priority of Chinese Patent Application No. 202411450765.5 filed with the China National Intellectual Property Administration on Oct. 17, 2024, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.TECHNICAL FIELD

[0002] The present disclosure belongs to the technical field of surface coating modification for alloys, and specifically relates to a multi-principal element Al—Co—Cr—Cu—Fe—Ni high-entropy alloy (HEA) coating and a preparation method thereof.BACKGROUND

[0003] Titanium alloys exhibit low surface hardness, poor wear resistance, and inadequate high-temperature oxidation resistance, making the titanium alloys prone to surface defects such as pits and notches during service. TC4 titanium alloy is a material highly susceptible to surface damage. At a damaged site of a component made of TC4 titanium alloy, a fatigue crack tends to propagate rapidly to cause the partial fracture of the component, thereby compromising the reliability and safety of the component in service. Therefore, titanium alloy components in practical use often require a surface-strengthening treatment to improve the fatigue performance.

[0004] HEAs refer to alloys produced from five or more metallic elements in equal or near-equal proportions. Due to unique elemental compositions, atomic arrangements, and interaction potential fields, HEAs demonstrate the thermodynamic high-entropy effect, the kinetic sluggish diffusion effect, the structural lattice distortion effect, and the performance-related cocktail effect, and tend to form simple single-phase solid solutions, including body-centered cubic (BCC) structures, face-centered cubic (FCC) structures, and hexagonal close-packed (HCP) structures. Consequently, HEAs exhibit outstanding comprehensive properties, such as high strength / hardness and excellent high-temperature oxidation resistance, corrosion resistance, radiation resistance, and wear resistance. As a result, HEAs hold a promising prospect for applications in extreme service environments.

[0005] Surface modification methods for titanium alloys mainly include chemical heat treatment, ion implantation, micro-arc oxidation, electroplating, thermal spraying, laser surface alloying, laser cladding, etc. The laser cladding technology offers a high melting temperature and a high cooling rate, which could refine microstructures of a cladding layer. Additionally, the low dilution ratio of laser cladding could reduce the elemental interdiffusion between a cladding layer and elements of a substrate, and maintain the designed composition of a cladding layer while achieving the metallurgical bonding. Thus, the laser cladding technology shows unique advantages in manufacturing HEA coatings, and has been widely used for surface modification of titanium alloys.

[0006] Therefore, it is highly urgent and necessary to provide an HEA coating with high hardness, excellent wear resistance, and prominent high-temperature oxidation resistance to address the extreme service conditions of the existing titanium alloy components.SUMMARY

[0007] In view of this, an object of the present disclosure is to provide a multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating and a preparation method thereof. The coating prepared by the present disclosure demonstrates high hardness, excellent wear resistance, and prominent high-temperature oxidation resistance.

[0008] To achieve the above objects, the present disclosure provides a multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating, including metal elements Al, Cu, Co, Cr, Fe, and Ni in a molar ratio of: 0.7:0.3:1:1:1:1,

[0009] where each of raw materials for the Al and the Cu is a metal powder, and a raw material for the Co, the Cr, the Fe, and the Ni is a CoCrFeNi alloy powder; and

[0010] a molar ratio of Co, Cr, Fe, and Ni in the CoCrFeNi alloy powder is 1:1:1:1.

[0011] Compared with a direct use of independent Co, Cr, Fe, and Ni powders, the above technical solution could achieve the uniform composition distribution in the coating while ensuring the excellent fluidity of powders.

[0012] The present disclosure provides a method for preparing the multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating, including the following steps:

[0013] S1, weighing and mixing an Al powder, a Cu powder, and the CoCrFeNi alloy powder according to the molar ratio of Al:Cu:Co:Cr:Fe:Ni, subjecting a resulting mixture to ball-milling, and then drying to obtain a mixed powder;

[0014] S2, subjecting a titanium alloy substrate to surface pretreatment to obtain a pretreated titanium alloy substrate; and

[0015] S3, spreading and pressing the mixed powder on a surface of the pretreated titanium alloy substrate to obtain a preplaced powder layer, and subjecting the preplaced powder layer to laser cladding to obtain the multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating.

[0016] In some embodiments, in S1, the Al powder, the Cu powder, and the CoCrFeNi alloy powder each have a purity of not less than 99.9 wt. % and a particle size of 15 μm to 53 μm, and are all spherical powders.

[0017] In some embodiments, in S1, the ball-milling is conducted using a high-energy ball mill; and the ball-milling is conducted for 10 h at a rotational speed of 120 rpm, with a ratio of a ball to a material ratio being 4:1.

[0018] In some embodiments, in S1, the drying is conducted at 80° C. to 100° C. for 1 h to 2 h.

[0019] In some embodiments, the surface pretreatment in S2 is conducted by: polishing a surface of the titanium alloy substrate with a 400-grit sandpaper and a 600-grit sandpaper sequentially, rinsing and wiping the surface of the titanium alloy substrate with alcohol, and then drying in a drying oven at a temperature of 60° C. to 80° C. for 1 h to 2 h.

[0020] In some embodiments, in S3, a preplaced powder layer has a thickness of is 1 mm to 2 mm.

[0021] In some embodiments, in S3, the laser cladding is conducted under the following parameters: a power P of 1,100 W, a scanning speed v of 300 mm / min, a spot diameter D of 4 mm, a defocus amount of 13 mm, a pure Ar gas being adopted as a protective gas during a cladding process, and a gas flow rate of 15 L / min.

[0022] Some embodiments of the present disclosure exhibit at least the following beneficial effects:

[0023] 1) The multi-principal element HEA coating prepared by the laser cladding according to the present disclosure exhibits a favorable macroscopic morphology and achieves excellent metallurgical bonding with the substrate.

[0024] 2) The multi-principal element HEA coating prepared by the laser cladding according to the present disclosure has uniform and dense microstructures, and includes face-centered cubic (FCC) and body-centered cubic (BCC) structures and a small amount of a Laves strengthening phase, and presents grain morphologies including at least one selected from the group consisting of equiaxed and columnar grains. The multi-principal element HEA coating exhibits significantly-improved hardness and wear resistance compared to the substrate.

[0025] 3) In the present disclosure, four principal elements of Co, Cr, Fe, and Ni in an equimolar ratio could form CoCrFeNi HEA with a single FCC phase. The addition of Cu promotes the transition of an alloy microstructure toward the FCC phase. The addition of Al facilitates the transition of an alloy microstructure toward the BCC phase. In the present disclosure, Al and Cu are incorporated at specific amounts to form the optimal microstructures, such that the alloy demonstrates a favorable strength-ductility balance. As a result, the coating has both the strength and ductility enhanced.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a macroscopic morphology of a coating prepared in Example 1;

[0027] FIG. 2 shows X-ray diffraction (XRD) patterns of coatings prepared in Example 1 and Comparative Examples 1 to 2;

[0028] FIG. 3 shows a scanning electron microscopy (SEM) image of the coating prepared in Example 1; and

[0029] FIG. 4 is a hardness distribution line chart for the coating prepared in Example 1 and a substrate.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Multiple exemplary embodiments of the present disclosure are now described in detail. The detailed description should not be considered as a limitation to the present disclosure, but should be understood as a detailed description of some aspects, features, and embodiments of the present disclosure.

[0031] It should be understood that terms described in the present disclosure are merely used to describe specific embodiments and are not intended to limit the present disclosure. In addition, for a numerical range in the present disclosure, it should be understood that each intermediate value between an upper limit and a lower limit of the range is also specifically disclosed. Each small range between any stated value or an intermediate value in a stated range and any other stated value or an intermediate value in the stated range is also included in the present disclosure. Upper and lower limits of each of these small ranges can independently be included in or excluded from the range.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the art described in the present disclosure. Although only preferred methods and materials are described in the present disclosure, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present disclosure. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and / or materials related to the documents. In case of conflict with any incorporated documents, the content of this specification shall prevail.

[0033] It is obvious to a person skilled in the art that a plurality of modifications and variations can be made to the specific embodiments of the specification of the present disclosure without departing from the scope or spirit of the present disclosure. Other embodiments derived from the specification of the present disclosure are obvious to a person skilled in the art. The specification and embodiments of the present disclosure are merely exemplary.

[0034] As used herein, the terms such as “including”, “comprising”, “having”, “containing”, etc. are all open-ended, which means including but not limited to.Example 1

[0035] A multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating was prepared through the following steps:

[0036] (1) An Al powder, a Cu powder, and a CoCrFeNi alloy powder were weighed. A molar ratio of Al:Cu:Co:Cr:Fe:Ni was 0.7:0.3:1:1:1:1. A molar ratio of Co, Cr, Fe, and Ni in the CoCrFeNi alloy powder was 1:1:1:1.

[0037] The Al powder, the Cu powder, and the CoCrFeNi alloy powder each had a purity of not less than 99.9 wt. % and a particle size of 40 μm, and were all spherical powders.

[0038] (2) The Al powder, the Cu powder, and the CoCrFeNi alloy powder were added to a planetary high-energy ball mill. A resulting mixture was subjected to ball-milling for 10 h at a rotational speed of 120 rpm, with a ratio of a ball to a material being 4:1, and then drying at 90° C. for 1 h to 2 h to obtain a mixed powder.

[0039] (3) A titanium alloy substrate Ti-6Al-4V (the Ti-6Al-4V contains 5.5% to 6.75% by mass of Al and 3.5% to 4.5% by mass of V, and the balance is Ti) was subjected to surface pretreatment under the following steps: a surface of the titanium alloy substrate was polished with a 400-grit sandpaper and a 600-grit sandpaper sequentially to remove oxides and oil stains on the surface of the titanium alloy substrate, and then rinsed and wiped with alcohol, and finally dried in a drying oven at 70° C. for 2 h to obtain a pretreated titanium alloy substrate.

[0040] (4) The mixed powder obtained in the step (2) was spread and pressed on a surface of the pretreated titanium alloy substrate obtained in the step (3) to form a preplaced layer with a thickness of 1.5 mm. The preplaced layer was subjected to laser cladding to obtain the multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating. The laser cladding was conducted under the following parameters: a power P of 1,100 W, a scanning speed v of 300 mm / min, a spot diameter D of 4 mm, a defocus amount of 13 mm, a pure Ar gas being adopted as a protective gas during a cladding process, and a gas flow rate of 15 L / min.

[0041] FIG. 1 shows a macroscopic morphology of the coating prepared in Example 1.

[0042] FIG. 3 shows an SEM image of the coating prepared in Example 1. It can be seen that the coating exhibits uniform and dense microstructures without significant defects, and presents grain morphologies including equiaxed and columnar grains.Example 2

[0043] A multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating was prepared specifically through the following steps:

[0044] (1) An Al powder, a Cu powder, and a CoCrFeNi alloy powder were weighed. A molar ratio of Al:Cu:Co:Cr:Fe:Ni should be 0.7:0.3:1:1:1:1. A molar ratio of Co, Cr, Fe, and Ni in the CoCrFeNi alloy powder was 1:1:1:1.

[0045] The Al powder, the Cu powder, and the CoCrFeNi alloy powder each had a purity of no less than 99.9 wt. % and a particle size of 53 μm, and were all spherical powders.

[0046] (2) The Al powder, the Cu powder, and the CoCrFeNi alloy powder were added to a planetary high-energy ball mill. A resulting mixture was subjected to ball-milling for 10 h at a rotational speed of 120 rpm with a ratio of a ball to a material being 4:1, and then drying at 100° C. for 2 h to obtain a mixed powder.

[0047] (3) A titanium alloy substrate Ti-6Al-4V was subjected to surface pretreatment under the following steps: a surface of the titanium alloy substrate was polished with a 400-grit sandpaper and a 600-grit sandpaper sequentially to remove oxides and oil stains on the surface of the titanium alloy substrate, and then rinsed and wiped with alcohol, and finally dried in a drying oven at 80° C. for 2 h to obtain a pretreated titanium alloy substrate.

[0048] (4) The mixed powder obtained in the step (2) was spread and pressed on a surface of the pretreated titanium alloy substrate obtained in the step (3) to form a preplaced layer with a thickness of 2 mm. The preplaced layer was subjected to laser cladding to obtain the multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating. The laser cladding was conducted under the following parameters: a power P of 1,100 W, a scanning speed v of 300 mm / min, a spot diameter D of 4 mm, a defocus amount of 13 mm, a pure Ar gas being adopted as a protective gas during a cladding process, and a gas flow rate of 15 L / min.Example 3

[0049] A multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating was prepared specifically through the following steps:

[0050] (1) An Al powder, a Cu powder, and a CoCrFeNi alloy powder were weighed. A molar ratio of Al:Cu:Co:Cr:Fe:Ni was 0.7:0.3:1:1:1:1. A molar ratio of Co, Cr, Fe, and Ni in the CoCrFeNi alloy powder was 1:1:1:1.

[0051] The Al powder, the Cu powder, and the CoCrFeNi alloy powder each had a purity of not less than 99.9 wt. % and a particle size of 15 μm, and were all spherical powders.

[0052] (2) The Al powder, the Cu powder, and the CoCrFeNi alloy powder were added to a planetary high-energy ball mill. A resulting mixture was subjected to ball-milling for 10 h at a rotational speed of 120 rpm with a ratio of a ball to a material being 4:1, and then drying at 80° C. for 1 h to obtain a mixed powder.

[0053] (3) A titanium alloy substrate Ti-6Al-4V was subjected to surface pretreatment under the following steps: a surface of the titanium alloy substrate was polished with a 400-grit sandpaper and a 600-grit sandpaper sequentially to remove oxides and oil stains on the surface of the titanium alloy substrate, and then rinsed and wiped with alcohol, and finally dried in a drying oven at 60° C. for 2 h to obtain a pretreated titanium alloy substrate.

[0054] (4) The mixed powder obtained in the step (2) was spread and pressed on a surface of the pretreated titanium alloy substrate obtained in the step (3) to form a preplaced layer with a thickness of 1 mm. The preplaced layer was subjected to laser cladding to obtain the multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating. The laser cladding was conducted under the following parameters: a power P of 1,100 W, a scanning speed v of 300 mm / min, a spot diameter D of 4 mm, a defocus amount of 13 mm, a pure Ar gas being adopted as a protective gas during a cladding process, and a gas flow rate of 15 L / min.Comparative Example 1

[0055] This comparative example was the same as the method in Example 1, except that the Cu powder was not adopted and a molar ratio of Al:Co:Cr:Fe:Ni was 1:1:1:1:1.Comparative Example 2

[0056] This comparative example was the same as the method in Example 1, except that the Al powder was not adopted and a molar ratio of Cu:Co:Cr:Fe:Ni was 1:1:1:1:1.Comparative Example 3

[0057] This comparative example was the same as the method in Example 1, except that Co, Cr, Fe, and Ni powders were used instead of the CoCrFeNi alloy powder, and a molar ratio of Co, Cr, Fe, and Ni was 1:1:1:1.Test Example 11. The titanium alloy substrates with coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2 were cut into rectangular specimens of 20 mm×10 mm×10 mm by wire electrical discharge machining. Cutting surfaces of coatings of the specimens were polished with 240-grit, 600-grit, 800-grit, 1,200-grit, and 2,000-grit sandpapers sequentially to remove oil stains and oxides on the surfaces until smooth, and then finely polished using a silica fine polishing suspension with a particle size of 0.12 μm until no visible scratches remained, and ultrasonically cleaned with absolute ethanol. Phase analysis was then conducted, and resulting XRD patterns are shown in FIG. 2. It can be seen that a phase structure of the coating prepared in Example 1 includes FCC and BCC solid solutions, indicating a relatively-simple structure.

[0059] 2. The HEA coating prepared in Example 1 was characterized for mechanical properties. A hardness of the HEA coating prepared in Example 1 was shown in FIG. 4. As shown in FIG. 4, Al0.7CoCrCu0.3FeNi HEA coating with a dual-phase structure exhibits a significantly-improved hardness compared to the substrate. An average hardness of the coating is 723.66 HV0.5, an average hardness of the substrate is 342.1 HV0.5. The hardness of the coating is 2.12 times the hardness of the substrate, indicating a remarkable improvement in hardness.

[0060] Moreover, average hardness values of the coatings prepared in Comparative Examples 1 to 3 on the substrate were measured to be 701.59 HV0.5, 694.70 HV0.5, and 716.19 HV0.5, respectively.

[0061] The above are merely preferred embodiments of the present disclosure, and are not intended to limit the present disclosure, and various modifications and changes may be made by a person skilled in the art to the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present disclosure shall fall within the scope of the present disclosure.

Claims

1. A multi-principal element Al—Co—Cr—Cu—Fe—Ni high-entropy alloy (HEA) coating, comprising metal elements Al, Cu, Co, Cr, Fe, and Ni in a molar ratio of Al:Cu:Co:Cr:Fe:Ni of 0.7:0.3:1:1:1:1, whereineach of raw materials for the Al and the Cu is a metal powder; anda raw material for the Co, the Cr, the Fe, and the Ni is a CoCrFeNi alloy powder, and a molar ratio of the Co, the Cr, the Fe, and the Ni in the CoCrFeNi alloy powder is 1:1:1:1.

2. A method for preparing the multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating of claim 1, comprising the following steps:S1, weighing and mixing an Al powder, a Cu powder, and the CoCrFeNi alloy powder according to the molar ratio of Al:Cu:Co:Cr:Fe:Ni, subjecting a resulting mixture to ball-milling, and then drying to obtain a mixed powder;S2, subjecting a titanium alloy substrate to surface pretreatment to obtain a pretreated titanium alloy substrate; andS3, spreading and pressing the mixed powder on a surface of the pretreated titanium alloy substrate to obtain a preplaced layer, and subjecting the preplaced powder layer to laser cladding to obtain the multi-principal element Al—Co—Cr—Cu—Fe—Ni HEA coating.

3. The method of claim 2, wherein in S1, the Al powder, the Cu powder, and the CoCrFeNi alloy powder each have a purity of not less than 99.9 wt. % and a particle size of 15 micrometres (μm) to 53 μm, and are all spherical powders.

4. The method of claim 2, wherein in S1, the ball-milling is conducted using a high-energy ball mill; and the ball-milling is conducted for 10 hours (h) at a rotational speed of 120 revolutions per minute (rpm), with a ratio of a ball to a material being 4:1.

5. The method of claim 2, wherein in S1, the drying is conducted at a temperature of 80° C. to 100° C. for 1 h to 2 h.

6. The method of claim 2, wherein the surface pretreatment in S2 is conducted by: polishing a surface of the titanium alloy substrate with a 400-grit sandpaper and a 600-grit sandpaper sequentially, rinsing and wiping the surface of the titanium alloy substrate with alcohol, and then drying in a drying oven at a temperature of 60° C. to 80° C. for 1 h to 2 h.

7. The method of claim 2, wherein the titanium alloy substrate in S2 is Ti-6Al-4V.

8. The method of claim 2, wherein in S3, the preplaced powder layer has a thickness of 1 millimeter (mm) to 2 mm.

9. The method of claim 2, wherein in S3, the laser cladding is conducted under the following parameters: a power P of 1,100 watt (W), a scanning speed v (velocity) of 300 mm / min (mm / minute), a spot diameter D of 4 mm, a defocus amount of 13 mm, a pure Ar gas being adopted as a protective gas during a cladding process, and a gas flow rate of 15 L(liters) / min.

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