Low-temperature self-lubricating high-entropy alloy wire and preparation method and application thereof

Abstract

The present application belongs to the technical field of electric arc additive manufacturing and low-temperature material, and more particularly relates to a low-temperature self-lubricating high-entropy alloy wire, a preparation method and application thereof. The low-temperature self-lubricating high-entropy alloy wire provided by the present application comprises a coating layer and a powder core; the coating layer is Ni; the composition of the powder core comprises Co, Cr, Fe, Ni, Mo, a low-melting-point metal, Cu@graphene (copper-coated graphene composite powder) and RE; the low-melting-point metal comprises at least one of Sn, Bi and Zn. In the powder core of the present application, Cu@graphene, the strengthening phase Mo and the low-melting-point metal with lubricating effect are added, which cooperates with the CoCrFeNi-based powder and the rare earth intermediate alloy powder, so as to improve the wear resistance and lubricity under low-temperature working conditions, and on the basis of reducing wear damage, the wire has good comprehensive mechanical properties.

Description

Technical Field

[0001] This invention belongs to the fields of electric arc additive manufacturing technology and low-temperature materials technology, and more specifically relates to a low-temperature self-lubricating high-entropy alloy wire, its preparation method and application. Background Technology

[0002] Arc additive manufacturing technology is widely used in the fabrication of cryogenic equipment and components due to its advantages such as high efficiency and low cost. Alloy wire, as a core consumable, directly determines the quality of the cladding layer. Commonly used wires for cryogenic arc additive manufacturing are mainly stainless steel, titanium alloys, and nickel-based alloys.

[0003] Stainless steel, combined with corrosion-resistant elements such as Co and Mo, primarily focuses on low-temperature corrosion resistance; titanium alloys enhance low-temperature stability through the addition of elements like Al and V; and nickel-based alloys mainly focus on low-temperature strength and toughness. It is evident that their compositional designs are limited in their specific applications and lack design considerations for low-temperature lubrication systems. This results in commonly used low-temperature wires exhibiting high low-temperature friction coefficients and insufficient wear resistance in applications such as LNG carriers, LNG / ethylene carriers, polar research vessels, icebreakers, acoustic and spatial detection, satellites, and spacecraft engines.

[0004] Currently, the consumables commonly used in arc additive manufacturing are mainly divided into two categories: traditional wire and powder-core wire. However, both have significant limitations. The wire-forming process of traditional wire involves multiple steps such as powder mixing, melting, casting, hot rolling, drawing, annealing, and straightening. The process is cumbersome and lengthy, resulting in high energy consumption and high equipment investment. In addition, waste is easily generated during long-processing, keeping costs high. Although the process of powder-core wire is relatively simple, involving rolling a metal strip into a U-shaped groove, gravity filling it with metal powder, and then closing it with rollers to form a coating structure, it faces the problem of low filling rate. Due to the thin outer skin and the tendency of gravity filling to form pores, the filling rate is usually only 20-30%. At the same time, the composition is not uniform, and uneven powder distribution can easily lead to defects such as component segregation, loose structure, pores, and cracks in the cladding layer, resulting in significant fluctuations in properties such as hardness, wear resistance, and toughness, and insufficient stability. In addition, both types of wires lack designs for self-lubricating properties: traditional wires rely solely on the inherent properties of the base metal, resulting in a high coefficient of friction at low temperatures; existing powder-core wires are mostly Al-based, with the addition of ceramic phases such as Al2O3 to improve wear resistance, but such additions reduce the overall mechanical properties of the wires in low-temperature environments, thus failing to meet the requirements for low-temperature wear-resistant components such as liquefied natural gas carriers, polar research vessels, and satellite and spacecraft engines.

[0005] It is evident that how to shorten the processing steps, reduce costs, increase the filling rate of the powder core, solve the problem of unevenness caused by the flow of the powder core due to gravity and other reasons during the use of the powder core filament, and ensure the quality of the subsequent cladding layer has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention addresses the problems of long and costly traditional wire processing, low filling rate of powder-core wire leading to porosity and cracks in the cladding layer due to easy component flow, and the lack of targeted self-lubricating design, high low-temperature friction coefficient, insufficient wear resistance, and difficulty in balancing mechanical properties in existing commonly used low-temperature wires such as stainless steel, titanium alloys, and nickel-based alloys. It provides a low-temperature self-lubricating high-entropy alloy wire, its preparation method, and its applications to solve the aforementioned problems of existing technologies. This invention achieves the technical goals of short processing flow, high filling rate, stable and non-flowing composition, and synergistic low-temperature self-lubrication and toughness, reducing production costs, ensuring cladding layer quality, and meeting the repair and preparation needs of wear-resistant parts for low-temperature equipment.

[0007] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is to provide a low-temperature self-lubricating high-entropy alloy wire, wherein the low-temperature self-lubricating high-entropy alloy wire includes a cladding layer and a powder core; The coating layer is Ni; The powder core is composed of Co, Cr, Fe, Ni, Mo, low melting point metals, Cu@graphene (copper-coated graphene composite powder), and RE; The low-melting-point metal includes at least one of Sn, Bi, and Zn.

[0008] Furthermore, by atomic percentage, the low-temperature self-lubricating high-entropy alloy wire comprises: The composition comprises 5-8 at.% low-melting-point metals, 1-2 at.% RE, 5-8 at.% Mo, 2-8 at.% Cu@graphene, with the balance being equal proportions of Co, Cr, Fe, and Ni; wherein the Cu@graphene is expressed as Cu in atomic percentage.

[0009] Furthermore, the RE includes at least one of La, Ce, Pr, Nd, and Y, preferably Ce, La, or Y.

[0010] Furthermore, the atomic ratio of Cu to graphene in the Cu@graphene is (45:55)-(60:40), preferably 52:48.

[0011] The low-melting-point metal used in the low-temperature self-lubricating high-entropy alloy wire of this invention is a low-melting-point metal with lubricating properties.

[0012] The second technical solution of this invention provides a method for preparing the above-mentioned low-temperature self-lubricating high-entropy alloy wire, comprising the following steps: Weigh out CoCrFeNi-based powder, Mo element powder, rare earth intermediate alloy powder, Cu@graphene (copper-coated graphene composite powder), low-melting-point metal and Ni tube as raw materials; The CoCrFeNi-based powder, Mo element powder, rare earth intermediate alloy powder, and Cu@graphene are used as core powders, which are mixed and dried to obtain pretreated core powders. The pretreated core powder is filled into the pretreated Ni tube and vibrated to compact it, so that the filling rate reaches 35%~40%. Then, a low-melting-point metal is prepared as a melt and injected into the Ni tube to fill the pores. The tube is then welded and sealed. Subsequently, aluminum is plated on the outer layer of the Ni tube, and vent holes are set at both ends. The tube is then hot-extruded to reduce the diameter, resulting in a coarse wire blank with a filling rate of 55%~60%. The outer aluminum film of the coarse wire blank is etched away to obtain the low-temperature self-lubricating high-entropy alloy wire.

[0013] Furthermore, the CoCrFeNi base powder is a powder of elemental elements Co, Cr, Fe, and Ni, or a mixture of at least one of elemental elements Co, Cr, Fe, and Ni with CoCrFeNi high-entropy alloy powder.

[0014] Furthermore, the rare earth master alloy powder includes RE-Ni master alloy powder and / or RE-Fe master alloy powder, preferably at least one of Ce-Ni alloy, La-Ni alloy, Y-Ni alloy, Ce-Fe alloy, La-Fe alloy and Y-Fe alloy.

[0015] In this invention, Ni is mainly provided by Ni tube and Ni in core powder. Co, Cr, Fe, Ni and other elements can be added in the form of element powder or alloy powder. When high-entropy alloy powder is used, the sum of the Ni content provided by Ni tube and Ni content in base powder satisfies the above ratio, so that the final deposited alloy satisfies the composition design of (CoCrFeNi)-based high-entropy alloy.

[0016] Furthermore, the Cu@graphene is prepared by a sol-gel method, the steps of which include: Graphene was dispersed in an aqueous ethanol solution to obtain a graphene suspension. Copper salt and citric acid are added to the graphene suspension to form a sol (achieving Cu²⁺ ionization). + Uniformly adsorbed on the graphene surface); The sol was treated in a water bath at 80°C for 6 hours, followed by vacuum drying at 120°C for 12 hours (to remove solvent and set the shape while avoiding Cu). 2+ The process involves oxidation followed by high-temperature reduction under argon protection to form a coating layer, yielding the Cu@graphene.

[0017] Optionally, the ratio of graphene to aqueous ethanol solution is 0.05-0.20 mmol:100-200 mL.

[0018] Optionally, the volume fraction of the ethanol aqueous solution is 40-80 vol.

[0019] Optionally, the copper salt includes at least one of copper nitrate, copper chloride, and copper acetate.

[0020] Optionally, the molar ratio of the copper salt to citric acid is 1:2.

[0021] Optionally, the complexation temperature is 25-60 °C and the time is 30-120 min.

[0022] Optionally, the high-temperature reduction treatment is performed at a temperature of 400-700 ℃ for a time of 30-120 min.

[0023] Optionally, the atomic percentage of Cu to graphene in the Cu@graphene is (45:55)-(60:40), preferably 52:48.

[0024] Furthermore, the mixing speed is 30-50 rpm, and the time is 3 hours.

[0025] Furthermore, the drying process is carried out at a temperature of 80°C for 2 hours.

[0026] Furthermore, the preparation steps of the pretreated Ni tube are as follows: tail welding and sealing, grinding and ultrasonic cleaning with anhydrous ethanol for 15 minutes, drying at 60°C to remove oxide scale and oil stains.

[0027] Furthermore, the vibration compaction treatment is performed at a frequency of 55 Hz for 15 minutes.

[0028] Furthermore, the temperature of the hot extrusion reduction is 400-450℃, and the extrusion ratio is 5:1.

[0029] During hot extrusion diameter reduction, the material undergoes plastic flow under high temperature and pressure, accompanied by pore compression, which in turn increases the density of the material.

[0030] The third technical solution of the present invention provides an application of the above-mentioned low-temperature self-lubricating high-entropy alloy wire in arc additive remanufacturing.

[0031] The matrix system used in this invention is a CoCrFeNi-based high-entropy alloy, which is strengthened by adding Mo to form a CoCrFeNiMo system. The general formula for the cladding layer formed in additive remanufacturing is as follows: (CoCrFeNi) 1-x-y-z-w Mo x REy Cu@graphene z Z w ; In this invention, the Ni tube and its internal filler powder melt simultaneously during arc additive deposition, participating in the alloying reaction of the molten pool. By adjusting the wall thickness, outer diameter, and core filling rate of the Ni tube, the Ni content in the deposited metal can be controlled, allowing it to form a multi-principal element alloy system with CoCrFeNi as the main component, incorporating Co, Cr, and Fe. Furthermore, the (CoCrFeNi)-based high-entropy alloy system involved in this invention is not a strictly equiatomic system, but rather a near-equiatomic or equiatomic multi-principal element alloy system composed primarily of Co, Cr, Fe, and Ni.

[0032] The fourth technical solution of the present invention provides the application of a low-melting-point metal in the preparation of a low-temperature self-lubricating high-entropy alloy wire for arc additive manufacturing, wherein the low-melting-point metal is used to form a lubricating phase to reduce the friction coefficient of the cladding layer in a low-temperature environment; the low-melting-point metal includes at least one of Sn, Bi and Zn.

[0033] The fifth technical solution of the present invention provides an application of Cu@graphene in the preparation of low-temperature self-lubricating high-entropy alloy wires for arc additive manufacturing, wherein the Cu@graphene is used to synergistically improve strength and lubrication performance; the Cu@graphene is prepared by the sol-gel method.

[0034] Furthermore, the preparation steps of the Cu@graphene include: Graphene was dispersed in an aqueous ethanol solution to obtain a graphene suspension. Copper salt and citric acid are added to the graphene suspension to form a sol (achieving Cu²⁺ ionization). + Uniformly adsorbed on the graphene surface); The sol was treated in a water bath at 80°C for 6 hours, followed by vacuum drying at 120°C for 12 hours (to remove solvent and set the shape while avoiding Cu). 2+ The process involves oxidation followed by high-temperature reduction under argon protection to form a coating layer, yielding the Cu@graphene.

[0035] Optionally, the ratio of graphene to aqueous ethanol solution is 0.05-0.20 mmol:100-200 mL.

[0036] Optionally, the volume fraction of the ethanol aqueous solution is 40-80 vol.

[0037] Optionally, the copper salt includes at least one of copper nitrate, copper chloride, and copper acetate.

[0038] Optionally, the molar ratio of the copper salt to citric acid is 1:2.

[0039] Optionally, the complexation temperature is 25-60 °C and the time is 30-120 min.

[0040] Optionally, the high-temperature reduction treatment is performed at a temperature of 400-700 ℃ for a time of 30-120 min.

[0041] Optionally, the atomic percentage of Cu to graphene in the Cu@graphene is 45:55-60:40, preferably 52:48.

[0042] The sixth technical solution of the present invention provides an application of the above-mentioned low-temperature self-lubricating high-entropy alloy wire in the preparation of a low-temperature self-lubricating cladding layer.

[0043] The present invention discloses the following technical effects: This invention achieves the following effects through a synergistic design of multiple fillers, semi-melt binders, and self-lubricating components: 1. Solve the problem of low filling rate: Vibration compaction lays the foundation for densification, and then low melting point metal melt is used to vibrate and fill the pores for further densification, so that the filling rate is increased to 55%~60%, far exceeding that of traditional powder core wire. 2. Solving the problem of uneven composition: The permanent coating of Ni tube and the fusion bonding of refractory metal with low melting point metal make the powder core form a stable semi-molten state, which maintains the uniformity of composition during use and thus ensures the quality of the cladding layer. 3. Improved low-temperature performance: Copper-coated graphene composite powder and low-melting-point metals with lubricating properties provide self-lubricating function and reduce the coefficient of friction at low temperatures; rare earth powder purifies the grains; CoCrFeMo-based powder ensures toughness and improves tensile strength and wear resistance. 4. Simplify processes and reduce costs: Eliminate the traditional smelting, casting, sintering, and hot rolling processes for wire materials, as well as the multiple roll coating processes for powder core wire materials, thereby reducing equipment investment and shortening the production cycle. Attached Figure Description

[0044] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The macroscopic surface morphology of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1.

[0045] Figure 2 The image shows a low-magnification metallographic image of the surface of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1.

[0046] Figure 3 This is a high-magnification metallographic image of the surface of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1.

[0047] Figure 4 The image shows the macroscopic morphology of the surface of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1 after cladding.

[0048] Figure 5 The image shows the cross-sectional metallographic image of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1 after cladding.

[0049] Figure 6 Metallographic image of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1 after cladding. Detailed Implementation

[0050] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0051] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0052] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0053] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0054] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0055] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0056] Unless otherwise specified, room temperature and ambient temperature in the specific embodiments of this invention refer to 20-30℃.

[0057] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0058] In some specific embodiments, the present invention provides a method for preparing a low-temperature self-lubricating high-entropy alloy wire, the steps of which include: Preparation of S1, Cu@graphene (copper-coated graphene): Graphene (0.05-0.20 mmol) was added to an ethanol-water solution (40-80% by volume, 100-200 mL), and ultrasonically stirred at high speed (1000 rpm) to prepare a uniform graphene suspension. Then, a copper salt (at least one of copper nitrate, copper chloride, and copper acetate) was added and complexed with citric acid at 25-60 °C for 30-120 min to achieve uniform adsorption of Cu²⁺ on the graphene surface, forming a sol. The resulting sol was treated in a water bath at 80 °C for 6 h, followed by vacuum drying at 120 °C for 12 h (to remove solvent and fix the structure while avoiding Cu²⁺). 2+ The process involves oxidation followed by high-temperature reduction under argon protection (400-700 °C, 30-120 min) to form a coating layer, yielding Cu@graphene (copper-coated graphene composite powder). In Cu@graphene, the atomic ratio of Cu to graphene is 45:55-60:40; the molar ratio of copper salt to citric acid is 1:2. S2. Raw material preparation: Prepare CoCrFeNi-based powder, Mo elemental powder for strengthening phase, rare earth intermediate alloy powder, Cu@graphene powder, low melting point metal and Ni tube according to the following atomic percentages; the particle size of each powder is controlled within the range of 15-45μm. Low melting point metal 5-8 at.%, RE 1-2 at.%, Mo 5-8 at.%, Cu@graphene 2-8 at.%, balance being equal proportions of Co, Cr, Fe, and Ni; wherein, the Cu@graphene is expressed as Cu in atomic percentage; RE includes at least one of La, Ce, Pr, Nd, and Y; A is at least one of Sn, Bi, and Zn; CoCrFeNi base powder is an elemental powder of Co, Cr, Fe, and Ni, or a mixture of CoCrFeNi high-entropy alloy powder; rare earth master alloy powder includes RE-Ni master alloy powder and / or RE-Fe master alloy powder, with an RE content of 20-30 at.%; S3. CoCrFeNi base powder, Mo elemental powder for strengthening phase, rare earth intermediate alloy powder and Cu@graphene are used as core powder. They are mixed with 0.1% ethanol by weight of the core powder and added to a V-type mixer. The mixture is stirred for 3 hours at 40 rpm to ensure that the core powder is fully and evenly mixed. After mixing, the mixture is dried at 80℃ for 2 hours and then passed through a 200-mesh sieve to obtain pretreated core powder with uniform composition and good flowability. S4. Use 800-grit sandpaper to lightly polish the inner and outer walls of the Ni tube to remove surface oxide scale and oil stains and weld the bottom. Put the polished Ni tube into an ultrasonic cleaner and use anhydrous ethanol as the cleaning agent to clean for 15 minutes to completely remove residual impurities. Then put it into a forced-air drying oven and dry at 60°C for 30 minutes to obtain a pre-treated Ni tube for later use. S5. Fix the pretreated Ni tube vertically on the vibration table, set the frequency to 55Hz and the amplitude to 0.8mm, slowly pour the pretreated core powder into the Ni tube with a funnel, vibrate to compact for 15min, and add pretreated core powder every 5min during this period to reduce the gap between the pretreated core powder and make the filling rate reach 35%-40%. S6. Place the low-melting-point metal A into a constant-temperature heating furnace and keep it at that temperature for 30 minutes to form a uniform melt. Then turn on the vibration table at a frequency of 50 Hz and an amplitude of 0.5 mm to slowly inject the melt into the Ni tube. During the injection process, a sealing pressure head is set at the Ni tube opening. The melt is pushed by air pressure to flow rapidly into the gap between the powder cores until the melt surface is flush with the Ni tube opening. Then turn off the vibration table and place the Ni tube at room temperature to cool naturally to room temperature. After the low-melting-point metal melt solidifies, it fills the pores of the core powder and bonds with the remaining metal powder. S7. After cooling, use Ni wire as welding wire to seal the Ni tube. Electroplat the sealed Ni tube with an aluminum film, controlling the aluminum film thickness to be 5~8μm. After the film is coated, drill a 0.8mm vent hole at each end of the Ni tube to prevent cracking during extrusion. Place the Ni tube with the vent holes in a forced-air drying oven and preheat it at 400-450℃ for 30min. Feed the preheated composite into the extruder barrel and hot extrude it at an extrusion speed of 5~10mm / s with an extrusion ratio of 5:1. After extrusion, a coarse wire blank with a uniform diameter is obtained, so that the filling rate reaches 55%~60%. S8. Immerse the coarse wire blank in a 5wt% dilute hydrochloric acid solution and stir. Observe the dissolution of the aluminum film during the process. Once the aluminum film is completely dissolved, immediately remove the wire and rinse it repeatedly with clean water 3 to 5 times to remove residual hydrochloric acid. Then, perform slight cold drawing to ensure a diameter tolerance of ±0.05mm to obtain a low-temperature self-lubricating high-entropy alloy wire.

[0059] This invention employs a composite filling technology that combines core powder vibration compaction with low-melting-point metal vibration filling, resulting in a final product filling rate of 55% to 60%.

[0060] This invention uses a finished Ni tube as a permanent outer sheath, with an outer aluminum-plated film to prevent oxidation. The Ni tube is retained after etching, and the low-melting-point metal is fused to bond with the refractory metal to form a semi-molten state, ensuring structural stability.

[0061] The present invention adds Cu@graphene and low-melting-point metal with lubricating effect to the powder core, and in combination with CoCrFeNi-based powder, reinforcing phase Mo and rare earth intermediate alloy powder, improves wear resistance and lubrication under low temperature conditions, and can reduce wear damage while ensuring that the wire has good comprehensive mechanical properties.

[0062] This invention integrates the processes of "powder mixing-filling-sealing-coating-extrusion-etching", eliminating the traditional melting, sintering, and multi-roll coating steps, and pre-drilled vent holes to avoid extrusion cracking, thus achieving short-process molding.

[0063] The low-temperature self-lubricating high-entropy alloy wire prepared by this invention is particularly suitable for the repair and preparation of low-temperature equipment and wear-resistant parts such as liquefied natural gas ships, liquefied petroleum gas / ethylene ships, polar research vessels, icebreakers, deep space exploration, satellites, and spacecraft engines.

[0064] Example 1 The preparation steps of low-temperature self-lubricating high-entropy alloy wire include: Preparation of S1, Cu@graphene (copper-coated graphene): Graphene (0.10 mmol) was added to an ethanol-water solution (60% v / v, 150 mL) and ultrasonically stirred at high speed (1000 rpm) to prepare a uniform graphene suspension. Then, copper salt (0.2 mmol, copper nitrate) and citric acid (0.40 mmol) were added and complexed at 35 °C for 100 min to achieve uniform adsorption of Cu²⁺ on the graphene surface, forming a sol. The resulting sol was treated in a water bath at 80 °C for 6 h, followed by vacuum drying at 120 °C for 12 h (to remove solvent and fix the structure while avoiding Cu²⁺). 2+ The process involves oxidation followed by high-temperature reduction under argon protection (500 °C, 60 min) to form a coating layer, yielding Cu@graphene (copper-coated graphene composite powder). In Cu@graphene, the atomic ratio of Cu to graphene is 52:48. S2. Raw material preparation: Prepare CoCrFeNi base powder, Mo elemental powder for strengthening phase, rare earth master alloy powder (Ce-Ni master alloy powder, Ce content is 30 at.%), Cu@graphene powder, low melting point metal powder (Sn and Bi, atomic ratio is 42:58) and Ni tubes according to the following atomic percentages; the particle size of each powder is controlled within the range of 15-45μm. The composition comprises 6.5 at.% low-melting-point metal, 1.5 at.% RE, 6 at.% Mo, 5 at.% Cu@graphene, with the balance being equal proportions of Co, Cr, Fe, and Ni; wherein the Cu@graphene is expressed as Cu in atomic percentage. CoCrFeNi-based powder is an elemental powder containing Co, Cr, Fe, and Ni. S3. CoCrFeNi base powder, Mo elemental powder for strengthening phase, rare earth intermediate alloy powder and Cu@graphene powder are used as core powder. They are mixed with 0.1% ethanol by weight of the core powder and added to a V-type mixer. The mixture is stirred for 3 hours at 40 rpm to ensure that the core powder is fully and evenly mixed. After mixing, the core powder is dried at 80℃ for 2 hours and then passed through a 200-mesh sieve to obtain pretreated core powder with uniform composition and good flowability. S4. Use 800-grit sandpaper to lightly polish the inner and outer walls of the Ni tube to remove surface oxide scale and oil stains and weld the bottom. Put the polished Ni tube into an ultrasonic cleaner and use anhydrous ethanol as the cleaning agent to clean for 15 minutes to completely remove residual impurities. Then put it into a forced-air drying oven and dry at 60°C for 30 minutes to obtain a pre-treated Ni tube for later use. S5. Fix the pretreated Ni tube vertically on the vibration table, set the frequency to 55Hz and the amplitude to 0.8mm, slowly pour the pretreated core powder into the Ni tube with a funnel, vibrate to compact for 15min, and add pretreated core powder every 5min during this period to reduce the gap between the pretreated core powder and make the filling rate reach 35%-40%. S6. Place the low-melting-point metal A into a constant-temperature heating furnace and keep it at that temperature for 30 minutes to form a uniform melt. Then turn on the vibration table at a frequency of 50 Hz and an amplitude of 0.5 mm to slowly inject the melt into the Ni tube. During the injection process, a sealing pressure head is set at the Ni tube opening. The melt is pushed by air pressure to flow rapidly into the gap between the powder cores until the melt surface is flush with the Ni tube opening. Then turn off the vibration table and place the Ni tube at room temperature to cool naturally to room temperature. After the low-melting-point metal melt solidifies, it fills the pores of the core powder and bonds with the remaining metal powder. S7. After cooling, use Ni wire as welding wire to seal the Ni tube. Electroplat the sealed Ni tube with an aluminum film, controlling the aluminum film thickness to be 5~8μm. After the film is coated, drill a 0.8mm vent hole at each end of the Ni tube to prevent cracking during extrusion. Place the Ni tube with the vent holes into a forced-air drying oven and preheat it to 400℃ for 30min. Feed the preheated composite into the extruder barrel and hot extrude it at an extrusion speed of 8mm / s with an extrusion ratio of 5:1. After extrusion, a coarse wire blank with a uniform diameter is obtained with a filling rate of 58.5%. S8. Immerse the coarse wire blank in a 5wt% dilute hydrochloric acid solution and stir. Observe the dissolution of the aluminum film during the process. Once the aluminum film is completely dissolved, immediately remove the wire and rinse it repeatedly with clean water 5 times to remove residual hydrochloric acid. Then, perform slight cold drawing to ensure a diameter tolerance of ±0.05mm to obtain a low-temperature self-lubricating high-entropy alloy wire.

[0065] Example 2 Compared with Example 1, the difference is that the atomic percentages are: 5 at.% low melting point metal, 1 at.% RE, 5 at.% Mo, 2 at.% Cu@graphene, and the balance is equal proportions of Co, Cr, Fe, and Ni.

[0066] Example 3 Compared with Example 1, the difference is that the atomic percentages are: 8 at.% low melting point metal, 2 at.% RE, 8 at.% Mo, 8 at.% Cu@graphene, and the balance is equal proportions of Co, Cr, Fe, and Ni.

[0067] Comparative Example 1 The difference compared to Example 1 is that the atomic ratio of Cu to graphene in Cu@graphene is 63:37.

[0068] Comparative Example 2 Compared with Example 1, the difference is that the atomic percentages are: RE 1.5 at.%, Mo 6 at.%, Cu@graphene 5 at.%, with the balance being equal proportions of Co, Cr, Fe, and Ni, i.e., no low-melting-point metals are added.

[0069] Comparative Example 3 Compared with Example 1, the difference is that the atomic percentages are: 6.5 at.% low melting point metal, 1.5 at.% RE, 6 at.% Mo, and the balance is equal proportions of Co, Cr, Fe, and Ni, that is, Cu@graphene is not added.

[0070] Comparative Example 4 Compared with Example 1, the difference is that the atomic percentages are: RE 1.5 at.%, Mo 6 at.%, and the balance is equal proportions of Co, Cr, Fe, and Ni, that is, Cu@graphene and low-melting-point metals are not added.

[0071] Test case Figure 1 The macroscopic surface morphology of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1.

[0072] Figure 2 The image shows a low-magnification metallographic image of the surface of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1.

[0073] Figure 3 This is a high-magnification metallographic image of the surface of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1.

[0074] The alloy wires prepared in the examples and comparative examples were used as consumables and adapted to the electric arc additive manufacturing equipment. The process parameters of additive current 135A, voltage 20V, and wire feeding speed 4m / min were set, and additive manufacturing was carried out by melting the alloy wires by electric arc.

[0075] Figure 4 The image shows the macroscopic morphology of the surface of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1 after cladding.

[0076] Figure 5 The image shows the cross-sectional metallographic image of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1 after cladding.

[0077] Figure 6 Metallographic image of the low-temperature self-lubricating high-entropy alloy wire prepared in Example 1 after cladding.

[0078] Another control group was set up, using the alloy wire prepared in Example 1 as consumable. In the above-mentioned arc additive manufacturing process, an ultrasonic vibration device was introduced below the molten pool with an ultrasonic frequency of 20kHz and a power of 800W, which was continuously applied to the deposition process.

[0079] The parameter data of the cladding layer obtained by the above-mentioned electric arc additive manufacturing are shown in Table 1 below.

[0080] Table 1 As can be seen from the data comparison in Table 1, this invention, by introducing Cu@graphene lubricating phase, low-melting-point metal with lubricating properties, and rare-earth intermediate alloy into the CoCrFeNiMo high-entropy alloy matrix, and combining it with vibration compaction and melt filling preparation processes, can significantly improve the filling rate and compositional stability of the core wire, effectively suppress the flow and segregation of the core wire during the arc additive manufacturing process, and obtain a dense cladding layer with few defects. Specifically, the introduction of Cu@graphene facilitates the formation of a stable solid lubricating film at the low-temperature friction interface, while the low-melting-point metal not only improves the core wire filling rate during preparation and service but also participates in the formation of the lubricating phase during friction. The synergistic effect of these two components enables the material to simultaneously possess excellent self-lubricating and wear-resistant properties under low-temperature conditions. The results of Comparative Examples 2-4 show that without any single key component, it is difficult to simultaneously achieve high filling rate, compositional stability, and excellent low-temperature friction and wear performance, thus fully demonstrating the necessity and synergy of the key technical features in this invention.

[0081] The alloy wire prepared using Example 1 can obtain a deposition layer with good forming quality and relatively uniform structure, indicating that the alloy wire itself can achieve excellent arc additive forming effect; and the introduction of ultrasonic vibration can further improve the flow state of the molten pool and have a certain strengthening effect on the deposition structure and properties.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0083] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-temperature self-lubricating high-entropy alloy wire, characterized in that, The low-temperature self-lubricating high-entropy alloy wire includes a coating layer and a powder core. The coating layer is Ni; The powder core is composed of Co, Cr, Fe, Ni, Mo, low melting point metals, Cu@graphene, and RE; The Cu@graphene is a copper-coated graphene composite powder; The low-melting-point metal includes at least one of Sn, Bi, and Zn; The low-temperature self-lubricating high-entropy alloy wire, by atomic percentage, comprises: 5-8 at.% low-melting-point metal, 1-2 at.% RE, 5-8 at.% Mo, 2-8 at.% Cu@graphene, with the balance being equal proportions of Co, Cr, Fe, and Ni; wherein, the Cu@graphene is included in the atomic percentage as Cu. The RE includes at least one of La, Ce, Pr, Nd, and Y; The atomic ratio of Cu to graphene in the Cu@graphene is (45:55)-(60:40); The preparation steps of the low-temperature self-lubricating high-entropy alloy wire include: Weigh out CoCrFeNi-based powder, Mo element powder, rare earth intermediate alloy powder, Cu@graphene, low melting point metal and Ni tube as raw materials; The CoCrFeNi-based powder, Mo element powder, rare earth intermediate alloy powder, and Cu@graphene are used as core powders, which are mixed and dried to obtain pretreated core powders. The pretreated core powder is filled into the pretreated Ni tube and vibrated to compact it, so that the filling rate reaches 35%~40%. Then, a low melting point metal is prepared as a melt and injected into the Ni tube to fill the pores. The end is welded and sealed. Then, aluminum is plated on the outer layer of the Ni tube, and vent holes are set at both ends. Hot extrusion is performed to reduce the diameter to obtain a coarse wire blank with a filling rate of 55%~60%. The outer aluminum film of the coarse wire blank is etched away to obtain the low-temperature self-lubricating high-entropy alloy wire.

2. A method for preparing the low-temperature self-lubricating high-entropy alloy wire according to claim 1, characterized in that the step... include: Weigh out CoCrFeNi-based powder, Mo element powder, rare earth intermediate alloy powder, Cu@graphene, low melting point metal and Ni tube as raw materials; The CoCrFeNi-based powder, Mo element powder, rare earth intermediate alloy powder, and Cu@graphene are used as core powders, which are mixed and dried to obtain pretreated core powders. The pretreated core powder is filled into the pretreated Ni tube and vibrated to compact it, so that the filling rate reaches 35%~40%. Then, a low melting point metal is prepared as a melt and injected into the Ni tube to fill the pores. The end is welded and sealed. Then, aluminum is plated on the outer layer of the Ni tube, and vent holes are set at both ends. Hot extrusion is performed to reduce the diameter to obtain a coarse wire blank with a filling rate of 55%~60%. The outer aluminum film of the coarse wire blank is etched away to obtain the low-temperature self-lubricating high-entropy alloy wire.

3. The preparation method according to claim 2, characterized in that, The CoCrFeNi base powder is a powder of elemental elements Co, Cr, Fe, and Ni, or a mixture of at least one of elemental elements Co, Cr, Fe, and Ni with CoCrFeNi high-entropy alloy powder. And / or, the rare earth master alloy powder includes RE-Ni master alloy powder and / or RE-Fe master alloy powder; And / or, the Cu@graphene is prepared by the sol-gel method.

4. The preparation method according to claim 2, characterized in that, The mixing speed is 30-50 rpm, and the time is 3 hours; And / or, the drying process is carried out at a temperature of 80°C for 2 hours; And / or, the preparation steps of the pretreated Ni tube are: tail welding and sealing, grinding and cleaning, and drying.

5. The preparation method according to claim 2, characterized in that, The vibration compaction process is performed at a frequency of 55 Hz for 15 minutes. And / or, the temperature of the hot extrusion reduction is 400-450°C, and the extrusion ratio is 5:

1.

6. The application of the low-temperature self-lubricating high-entropy alloy wire of claim 1 in arc additive remanufacturing.

7. The application of a low-melting-point metal in the preparation of the low-temperature self-lubricating high-entropy alloy wire as described in claim 1, characterized in that, The low-melting-point metal includes at least one of Sn, Bi, and Zn; The low-temperature self-lubricating high-entropy alloy wire is used in arc additive manufacturing.

8. An application of Cu@graphene in the preparation of the low-temperature self-lubricating high-entropy alloy wire as described in claim 1, characterized in that, The low-temperature self-lubricating high-entropy alloy wire is used in arc additive manufacturing.

9. The application of the low-temperature self-lubricating high-entropy alloy wire of claim 1 in the preparation of a low-temperature self-lubricating cladding layer.

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