High-performance plated tungsten filament and preparation method thereof

Abstract

The invention discloses a high-performance plated tungsten filament and a preparation method thereof, and relates to the technical field of plated tungsten filament preparation, and the preparation method comprises the following steps: preparing a tungsten filament matrix by a process of first hot drawing and then cold drawing, the tungsten filament matrix is about 80 [mu] m after hot drawing, and the tungsten filament matrix is cold-drawn to 10-40 [mu] ml and contains 98.5-100% of tungsten element, 0-1.5% of rare earth element, 1-5 [mu] m of grain size and 10 < 12 >-10 < 14 > m <-2 > of dislocation density; a transition layer, a middle strengthening layer and a functional alloy layer are arranged on the surface of the finished wire from inside to outside, the diameter of the finished wire is 0.01-0.5 mm, the tensile strength is 5000-7000 MPa, the number of torsion turns is larger than 800, and the resistivity is 0.05-0.08 mu omega.m. The composite material is excellent in comprehensive performance, high in tensile strength, large in torsion, good in resistivity, high in size precision, good in surface quality, resistant to oxidation, high in wear resistance, long in service life, controllable in preparation, beneficial to mass production and capable of adjusting the performance according to needs.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of coated tungsten wires, and specifically to a high-performance coated tungsten wire and a preparation method thereof. Background Art

[0002] As an important functional material, tungsten wires are widely used in many fields such as lighting, electronics, aerospace, etc. With the continuous progress of technology, the performance requirements for tungsten wires in various industries are becoming increasingly stringent.

[0003] In the lighting field, traditional incandescent bulbs rely on tungsten wires as the light-emitting elements. However, ordinary tungsten wires are prone to volatilization and embrittlement at high temperatures, resulting in a short bulb life and reduced luminous efficiency. Although energy-saving lighting technologies such as LEDs have gradually emerged in recent years, in some special lighting scenarios (such as stage lighting, automotive headlights, etc.), there is still a demand for tungsten wire light sources with high brightness and high stability, and the existing tungsten wire performance is difficult to fully meet these requirements.

[0004] In the electronics field, with the development of electronic products towards miniaturization and high performance, tungsten wire components in electronic devices (such as electron tube filaments, heating elements in semiconductor manufacturing equipment, etc.) need to have higher strength, better electrical conductivity and oxidation resistance. However, tungsten wires prepared by traditional processes have certain limitations in performance indicators such as tensile strength and resistivity, and cannot meet the high-precision and high-reliability requirements of modern electronic devices.

[0005] In the aerospace field, tungsten wires are used to manufacture high-temperature structural components and heating elements, etc., and need to maintain stable performance in extreme environments (such as high temperature, high pressure, strong radiation, etc.). Existing tungsten wire materials are prone to performance degradation when facing these harsh conditions, affecting the safety and reliability of aerospace equipment.

[0006] In addition, traditional tungsten wire preparation processes mainly use single cold drawing or hot drawing processes, which have many problems. Tungsten wires prepared by the cold drawing process have good surface quality, but have large internal stresses, which are prone to cause tungsten wire breakage during use; tungsten wires prepared by the hot drawing process have relatively small internal stresses, but have large surface roughness, affecting their performance in some high-precision application scenarios. Moreover, it is difficult to form an effective functional coating on the surface of tungsten wires by traditional processes, and the comprehensive performance of tungsten wires such as oxidation resistance and wear resistance cannot be further improved.

[0007] In order to meet the urgent needs of modern industry for high-performance tungsten wires, break through the limitations of traditional processes, and develop a new type of high-performance coated tungsten wire and its preparation method has important practical significance. Such coated tungsten wires should have excellent mechanical properties, electrical properties and oxidation resistance, etc., to meet the high-end application requirements in different fields and promote the technological upgrading and development of related industries. Summary of the Invention

[0008] (1) Technical problem to be solved

[0009] In view of the deficiencies of the prior art, the present invention provides a high-performance coated tungsten wire and a preparation method thereof.

[0010] (2) Technical solution

[0011] A high-performance coated tungsten wire includes a tungsten wire substrate, which is prepared by a process of first hot drawing and then cold drawing. A transition layer, an intermediate strengthening layer, and a functional alloy layer are sequentially arranged on its surface in the direction from inside to outside;

[0012] The transition layer is a nickel metal layer or a cobalt metal layer, with a thickness of 0.1 - 1 μm, and is used to enhance the bonding force between the intermediate strengthening layer and the tungsten wire substrate. The transition layer and the tungsten wire substrate are bonded by a metal bond, and the bonding force is not less than 50 MPa;

[0013] The intermediate strengthening layer is a nanocrystalline tungsten carbide layer or a nanocrystalline titanium nitride layer, with a thickness of 0.2 - 0.8 μm, a nanocrystalline particle size of 10 - 50 nm, a hardness of 20 - 30 GPa, and an elastic modulus of 400 - 600 GPa;

[0014] The functional alloy layer is one of a copper-zinc-aluminum alloy layer, a copper-nickel-silicon alloy layer, and a copper-tin-indium alloy layer, with a thickness of 0.5 - 5 μm. The weight percentage of copper element in the functional alloy layer is 50 - 75%. The functional alloy layer and the intermediate strengthening layer are bonded by diffusion, and the diffusion layer thickness is 0.05 - 0.2 μm;

[0015] The diameter of the high-performance coated tungsten wire is 0.01 - 0.5 mm, the tensile strength is 5000 - 7000 MPa, the number of torsion turns is greater than 800 turns, and the resistivity is 0.05 - 0.08 μΩ·m;

[0016] Furthermore, the weight percentage of tungsten element in the tungsten wire substrate is 98.5 - 100%, the weight percentage of rare earth element is 0 - 1.5%, the rare earth element is one or more of lanthanum, cerium, and rhenium, the grain size of the tungsten wire substrate is 1 - 5 μm, and the dislocation density is 10 12 -10 14 m -2 .

[0017] Furthermore, a method for preparing a high-performance coated tungsten wire includes the following steps:

[0018] S1: Raw material preparation and pretreatment: Tungsten powder with a purity of 98.5 - 100% is selected, and it is uniformly mixed with a lubricant at a mixing ratio of 100:1 - 100:5. Then, the mixed powder is subjected to cold isostatic pressing in a vacuum environment at a pressure of 150 - 300 MPa for a holding time of 1 - 5 hours to obtain a tungsten rod blank. The average particle size of the tungsten powder is 1 - 10 μm, the particle size of the lubricant is 0.1 - 1 μm, the pressure control system accuracy of the cold isostatic pressing equipment is ±1 MPa, and the holding time control system accuracy is ±0.1 hour. The mold of the cold isostatic pressing equipment is made of alloy steel, and the inner wall roughness of the mold is 0.1 - 0.3 μm;

[0019] S2: Hot wire drawing: The tungsten rod blank is heated and then hot wire drawn to a diameter of about 80 μm;

[0020] S3: Surface treatment and transition layer electroplating: The hot-drawn tungsten wire is subjected to surface treatment. First, chemical cleaning is used to remove surface oil and impurities. The alkaline cleaning uses a 5 - 10% sodium hydroxide solution, and the acid cleaning uses a 5 - 10% hydrochloric acid solution. The tungsten wire after chemical cleaning is protected by nitrogen during the drying process. Then, electrolytic polishing treatment is carried out. The polishing solution is a mixed solution of phosphoric acid and sulfuric acid to make the surface roughness of the tungsten wire reach 0.1 - 0.5 μm. After that, a transition layer is formed on the surface of the treated tungsten wire by electroplating. The electroplating solution is nickel chloride or nickel sulfamate solution, and 10 - 30 g / L of boric acid and 0.1 - 1 g / L of sodium dodecyl sulfate are added as buffer and wetting agents. The electroplating temperature is 20 - 30 °C, and the current density is 5 - 50 A / dm 2 , and the electroplating time is 10 - 60 minutes;

[0021] S4: Cold wire drawing: The tungsten wire after electroplating the transition layer is subjected to multi-pass cold wire drawing at room temperature. The number of drawing passes is 5 - 20 times, the deformation amount of each pass is 5 - 20%, the drawing speed is 1 - 10 m / min, and it is drawn to a diameter of 10 - 40 μm. The drawing equipment uses a high-precision cold drawing machine. The drawing die is made of cemented carbide (such as tungsten carbide). The working cone angle of the die is 6 - 12°, the surface roughness of the die is 0.05 - 0.2 μm, the length of the sizing zone is 2 - 5 mm, the surface hardness is 85 - 92 HRA. During the drawing process, an on-line detection device is used to monitor the diameter and surface quality of the tungsten wire in real time. The diameter measurement accuracy is ±0.005 mm, and the surface roughness measurement accuracy is ±0.1 μm;

[0022] S5: Intermediate Reinforcement Layer Deposition: The intermediate reinforcement layer is deposited on the surface of the transition layer by physical vapor deposition (PVD). When the intermediate reinforcement layer is a nanocrystalline tungsten carbide layer, magnetron sputtering is used with tungsten carbide as the target, argon as the working gas, the gas pressure is 0.2 - 0.8 Pa, the sputtering power is 100 - 500 W, the deposition rate is 0.1 - 0.5 μm / h, and the deposition temperature is 100 - 300 °C. When the intermediate reinforcement layer is a nanocrystalline titanium nitride layer, ion plating is used with titanium nitride as the target, nitrogen and argon as the working gases, the gas pressure is 0.3 - 0.9 Pa, the ion plating voltage is 50 - 150 V, the deposition rate is 0.15 - 0.6 μm / h, the deposition temperature is 150 - 350 °C. During the deposition process, the process parameters are controlled so that the nanocrystalline grain size of the intermediate reinforcement layer is 10 - 50 nm, the thickness is 0.2 - 0.8 μm, the hardness reaches 20 - 30 GPa, and the elastic modulus is 400 - 600 GPa. The ultimate vacuum degree of the vacuum system of the physical vapor deposition equipment is 1×10 -4 -1×10 -6 Pa, and the accuracy of the substrate bias power supply is ±5 V;

[0023] S6: Electroplating of Functional Alloy Layer

[0024] A functional alloy layer is formed on the surface of the intermediate reinforcement layer by electroplating. When the functional alloy layer is a copper-zinc alloy layer, the electroplating solution is a mixed solution of zinc oxide, copper sulfate, sodium hydroxide, and complexing agent, and 1 - 5 ml / L of ammonia water is added to adjust the pH value to 9 - 11, the electroplating temperature is 20 - 40 °C, and the current density is 1 - 20 A / dm 2 ; when the functional alloy layer is a copper-tin alloy layer, the electroplating solution is a mixed solution of copper pyrophosphate, sodium stannate, and potassium pyrophosphate, and 0.1 - 1 g / L of gelatin is added as an additive; when the functional alloy layer is a copper-zinc-tin alloy layer, the electroplating solution is a mixed solution of copper sulfate, zinc sulfate, sodium stannate, and sodium hydroxide, the electroplating temperature is 20 - 30 °C, and the current density is 1 - 10 A / dm 2 ; the electroplating bath is made of corrosion-resistant polytetrafluoroethylene material, the electrodes are made of titanium plates or ruthenium-titanium plates, and the electrode spacing is 5 - 15 cm;

[0025] S7: Post-treatment: The plated tungsten wire is cleaned. First, it is rinsed with deionized water 3 - 5 times, and the resistivity of the deionized water is greater than 18 MΩ·cm. Then, it is cleaned with ethanol in an ultrasonic cleaner for 10 - 30 minutes to remove the residual electroplating solution and impurities on the surface. During the drying process of the cleaned tungsten wire, vacuum drying or low dew point drying is used. Before packaging, the dried tungsten wire is protected by filling with nitrogen, and the packaging material is a moisture-proof and antioxidant aluminum foil bag. Finally, vacuum heat treatment is carried out to eliminate internal stress.

[0026] Furthermore, in step S2, the heating system of the hot drawing equipment should have the function of uniform heating. During the hot wire drawing process, the grain size of the tungsten wire needs to be monitored in real time. The measurement accuracy of the grain size is ±0.1 μm, and the grain size of the drawn tungsten wire should be controlled within 8 - 12 μm. The measurement accuracy of the drawing force for hot wire drawing is ±2%, and an overload protection device should be equipped to automatically stop drawing when the drawing force exceeds the set threshold to prevent the tungsten wire from breaking.

[0027] Furthermore, in step S3, a pure water rinsing link should be added between the caustic washing and pickling steps during the chemical cleaning process. The rinsing time is 3 - 5 minutes to remove the cleaning liquid remaining from the previous step and prevent the acid-base neutralization reaction from affecting the cleaning effect. The electrolytic polishing equipment should have an electrolyte circulation and filtration system with a filtration accuracy of 0.05 - 0.1 μm. During the electroplating process of the transition layer, the electroplating bath should be equipped with an automatic liquid level control system with a liquid level control accuracy of ±1 mm.

[0028] Furthermore, in step S4, the cold drawing machine should have an automatic lubrication system. The lubrication system automatically adjusts the supply amount of the lubricating fluid according to the drawing speed and drawing force to reduce the drawing force and minimize scratches on the surface of the tungsten wire. At the same time, the on-line detection device during the cold drawing process should have the function of automatically recording and analyzing data, and generating curves of the tungsten wire diameter and surface quality changes in real time.

[0029] Furthermore, in step S5, the target cooling system of the physical vapor deposition equipment should have high heat dissipation capacity to prevent the target from overheating, which may lead to unstable sputtering or evaporation rates and affect the quality of the intermediate strengthening layer. During the deposition process, the flow rate and pressure of the working gas should be monitored in real time. The physical vapor deposition equipment should be equipped with a film thickness monitoring system with a film thickness measurement accuracy of ±0.01 μm to monitor the deposition thickness of the intermediate strengthening layer in real time.

[0030] Furthermore, in step S6, the circulating filtration system used during the electroplating process should have a backwashing function. Backwashing is carried out once every 2 hours, and the backwashing time is 5 - 10 minutes. The temperature control system of the electroplating solution should have fast response ability. When the temperature of the electroplating solution deviates from the set value by ±1℃, it can be adjusted to the set temperature range within 1 - 2 minutes. At the same time, before electroplating the functional alloy layer, the surface of the intermediate strengthening layer is activated for 1 - 3 minutes to improve the bonding force between the functional alloy layer and the intermediate strengthening layer.

[0031] Further, in step S7, the ultrasonic cleaning machine should have an automatic frequency adjustment function to optimize the ultrasonic frequency in real time according to the cleaning effect. The vacuum heat treatment equipment should have an atmosphere control system to introduce an appropriate amount of hydrogen during the heat treatment process to further remove the residual stress inside the tungsten wire. During the packaging process, the nitrogen filling protection system should ensure that the purity of nitrogen in the package is above 99.9% and the pressure is 0.05 - 0.1 MPa to prevent the tungsten wire from oxidizing during storage and transportation. At the same time, the packaged tungsten wire should be marked with product specifications, production date, and batch information.

[0032] (III) Beneficial technical effects

[0033] The high-performance coated tungsten wire of this application has a unique multi-layer structure. The bonding force between layers is enhanced through the transition layer, the hardness and elastic modulus are improved by the intermediate strengthening layer, and the functional alloy layer endows specific functions. Its tensile strength reaches 5000 - 7000 MPa, the number of torsion turns is greater than 800 turns, and the resistivity is 0.05 - 0.08 μΩ·m, showing excellent performance in terms of strength, toughness, and electrical conductivity, and can meet the requirements of various high-end applications.

[0034] The process of hot drawing first and then cold drawing combines the advantages of both. Hot drawing improves the internal structure, and cold drawing improves the surface quality, and finally obtains a diameter accurate to 0.01 - 0.5 mm.

[0035] The reasonable design of the functional alloy layer (such as the copper-zinc-aluminum alloy layer, etc.) and between layers effectively improves the oxidation resistance and wear resistance of the tungsten wire, extends the service life, and can maintain stable performance and reduce maintenance costs when used in harsh environments such as aerospace.

[0036] The process parameters of each step in the preparation method are precisely controlled, such as the raw material mixing ratio, cold isostatic pressing parameters, temperature, current density, time, etc. of various treatments, and the equipment has high precision, which can ensure the consistency and stability of product performance, facilitate large-scale production, improve production efficiency, reduce production costs, and is also conducive to flexibly adjusting product performance according to different requirements. Specific embodiments

[0037] Example 1

[0038] Raw material preparation and pretreatment

[0039] Tungsten powder with a purity of 99.5% and an average particle size of 5 μm is selected and mixed evenly with graphite powder with a particle size of 0.5 μm according to a mass ratio of 100:3. The mixed powder is placed in a cold isostatic pressing equipment with a vacuum degree of 0.08 MPa, and a mold made of high-strength alloy steel material (inner wall roughness of 0.2 μm) is used to hold the pressure at 200 MPa for 3 hours to obtain a dense tungsten rod blank. The pressure control system accuracy of the cold isostatic pressing equipment is ±1 MPa, and the holding time control system accuracy is ±0.1 hour.

[0040] Hot drawing of wire

[0041] Heat the tungsten bar blank to 1500 °C (the temperature control accuracy of the hot drawing equipment is ±5 °C), and perform hot drawing of wire at a speed of 5 m / min until the diameter is about 80 μm. The hot drawing equipment has a uniform heating function, and the grain size of the tungsten wire is monitored in real time during the drawing process (the measurement accuracy is ±0.1 μm), the grain size is controlled at about 10 μm, the drawing force measurement accuracy is ±2%, and it is equipped with an overload protection device.

[0042] Surface treatment and electroplating of the transition layer

[0043] The tungsten wire after hot drawing is first alkali-washed (5% sodium hydroxide solution, 25 °C, 10 minutes), rinsed with pure water for 3 minutes, and acid-washed (5% hydrochloric acid solution, 30 °C, 10 minutes) to remove oil and impurities, and dried at 60 °C for 20 minutes under nitrogen protection. Then, in the electrolytic polishing solution (phosphoric acid: sulfuric acid: chromic acid = 1.5:1:0.8, volume ratio), polish at a current density of 30 A / dm 2 for 5 minutes (the power accuracy of the electrolytic polishing equipment is ±0.5%, and the time control accuracy is ±0.1 minute) to make the surface roughness reach 0.3 μm. Then, in the nickel chloride electroplating solution (concentration 200 g / L, containing 20 g / L boric acid and 0.5 g / L sodium dodecyl sulfate), electroplate at 25 °C and 30 A / dm 2 for 30 minutes to form a nickel transition layer with a thickness of 0.5 μm (the current accuracy of the electroplating equipment is ±0.5 A / dm 2 , the temperature control accuracy is ±1 °C, and the accuracy of the automatic liquid level control system of the electroplating tank is ±1 mm).

[0044] Cold drawing of wire

[0045] The tungsten wire after electroplating the transition layer is cold-drawn 10 times at room temperature, with a deformation amount of 10% per pass, a drawing speed of 5 m / min, and drawn to a diameter of 20 μm. Use a cemented carbide die (working cone angle 9°, surface roughness 0.1 μm, sizing band length 3 mm, surface hardness 88 HRA), and the automatic lubrication system of the drawing machine supplies liquid according to the drawing situation, and replace the die when the wear amount reaches 0.08 mm. During the drawing process, the on-line detection device (diameter measurement accuracy ±0.005 mm, surface roughness measurement accuracy ±0.1 μm) monitors and records and analyzes data in real time.

[0046] Deposition of the intermediate strengthening layer

[0047] Use the magnetron sputtering process to deposit a nanocrystalline tungsten carbide intermediate strengthening layer on the surface of the transition layer. Use tungsten carbide as the target, the argon gas pressure is 0.5 Pa, the sputtering power is 300 W, the deposition rate is 0.3 μm / h, and deposit 0.5 μm at 150 °C (the ultimate vacuum degree of the vacuum system of the physical vapor deposition equipment is 1×10-5 Pa, the accuracy of the substrate bias power supply is ±5 V, the target cooling system stabilizes the target temperature within ±10 °C, the accuracy of the gas flow measurement is ±0.1 sccm, the accuracy of the air pressure measurement is ±0.01 Pa, and the accuracy of the film thickness monitoring system is ±0.01 μm).

[0048] Electroplating of the functional alloy layer

[0049] A copper-zinc alloy functional alloy layer is formed on the surface of the intermediate strengthening layer by electroplating. The electroplating solution contains 25 g / L of cuprous cyanide, 10 g / L of zinc cyanide, and 20 g / L of sodium carbonate. Add 3 ml / L of ammonia water to adjust the pH to 10, and electroplate at 30 °C and 10 A / dm 2 for 90 minutes. The electroplating bath is made of polytetrafluoroethylene, the distance between the titanium plate electrodes is 10 cm, the filtration accuracy of the electroplating solution circulation filtration system is 0.5 μm, the magnetic stirring speed is 300 revolutions per minute, and the surface of the intermediate strengthening layer is activated before electroplating (activation solution [specific composition], 2 minutes).

[0050] Post-treatment

[0051] The plated tungsten wire is first rinsed 4 times with deionized water having a resistivity greater than 18 MΩ·cm, and then cleaned with ethanol in an ultrasonic cleaner with a frequency of 30 kHz and a power of 1000 W for 20 minutes. Then, it is heat-treated at a vacuum degree of 0.05 MPa and 300 °C for 2 hours (the temperature control accuracy of the vacuum heat treatment equipment is ±5 °C, and the vacuum degree control accuracy is ±0.005 MPa), vacuum drying is adopted (the dew point temperature is lower than -40 °C), nitrogen protection is filled before packaging (the nitrogen purity is above 99.9%, and the pressure is 0.08 MPa), and product identification is made.

[0052] Example 2

[0053] Raw material preparation and pretreatment

[0054] Tungsten powder with a purity of 99% (average particle size 3 μm) and molybdenum disulfide with a particle size of 0.3 μm are selected and mixed at a mass ratio of 100:2, and cold isostatic pressing is carried out at a vacuum degree of 0.06 MPa, with a pressure of 250 MPa and a pressure holding time of 2 hours. The relevant accuracy of the cold isostatic pressing equipment is the same as that in Example 1, and the mold material and roughness are the same.

[0055] Hot wire drawing

[0056] The tungsten rod blank is heated to 1450 °C (the temperature control accuracy of the hot drawing equipment is the same as that in Example 1), and hot drawn to 80 μm at a speed of 4 m / min. During the hot drawing process, the grain size is controlled at about 9 μm, and the measurement accuracy of the drawing force and other conditions are the same as those in Example 1.

[0057] Surface treatment and electroplating of the transition layer

[0058] The surface treatment process is the same as that of Example 1, but the electrolytic polishing current density is 20 A / dm 2 , and the polishing time is 8 minutes to make the surface roughness reach 0.2 μm. For the transition layer electroplating, a nickel sulfamate solution (concentration 250 g / L, containing 25 g / L boric acid and 0.8 g / L sodium dodecyl sulfate) is used, and electroplating is carried out at 28 °C and 40 A / dm 2 for 40 minutes to form a cobalt transition layer with a thickness of 0.8 μm (the relevant precision of the electroplating equipment is the same as that of Example 1).

[0059] Cold drawing for wire making

[0060] Cold drawing is carried out in 12 passes, with a deformation amount of 15% per pass and a drawing speed of 6 m / min, and it is drawn to a diameter of 30 μm. The relevant parameters of the die and drawing equipment are the same as those of Example 1, but the working cone angle of the drawing die is 10°.

[0061] Deposition of the intermediate strengthening layer

[0062] The nanocrystalline titanium nitride intermediate strengthening layer is deposited by ion plating process. Using titanium nitride as the target, the flow ratio of nitrogen to argon is 1:4, the gas pressure is 0.6 Pa, the ion plating voltage is 100 V, the deposition rate is 0.4 μm / h, and it is deposited at 200 °C for 0.6 μm (the relevant precision of the physical vapor deposition equipment is the same as that of Example 1).

[0063] Electroplating of the functional alloy layer

[0064] A copper-tin alloy functional alloy layer is formed. The electroplating solution contains 28 g / L cupric pyrophosphate, 15 g / L sodium stannate, 250 g / L potassium pyrophosphate, and 0.5 g / L gelatin. Electroplating is carried out at 40 °C and 12 A / dm 2 for 120 minutes. The parameters of the electroplating bath and related equipment are the same as those of Example 1.

[0065] Post-treatment

[0066] The post-treatment process is the same as that of Example 1, but the ultrasonic cleaning frequency is 40 kHz and the vacuum heat treatment temperature is 350 °C.

[0067] Comparative example

[0068] Raw material preparation and pretreatment

[0069] Tungsten powder with a purity of 99.2% (average particle size 4 μm) is selected, no lubricant is added, and the tungsten rod blank is directly pressed in the atmospheric environment, with a pressure of 180 MPa and a pressure holding time of 1 hour (without precise pressure and time control equipment).

[0070] Wire making

[0071] Using the traditional single cold drawing process, the tungsten rod blank is cold drawn at room temperature for 15 passes, with a deformation amount of 8% per pass, a drawing speed of 3 m / min, and drawn to a diameter of 25 μm. The drawing die is made of ordinary carbon steel (working cone angle 15°, surface roughness 0.3 μm), without an automatic lubrication and on-line detection device.

[0072] Surface treatment and functional layer formation (simple treatment, without multi-layer structure)

[0073] Only simple pickling (10% hydrochloric acid solution, 20 °C, 8 minutes) is carried out to remove surface impurities, and then in an ordinary copper plating solution (copper sulfate 25 g / L, sulfuric acid 50 g / L), at 25 °C, 5 A / dm 2 Electroplating is carried out for 10 minutes to form a simple copper layer, without complex structures such as an intermediate strengthening layer.

[0074] Post-treatment

[0075] After rinsing 2 times with tap water and drying naturally, there is no subsequent optimization treatment such as vacuum heat treatment.

[0076]

[0077]

[0078] It can be seen from the comparison between Example 1, Example 2 and the comparative example that the preparation method of the high-performance coated tungsten wire of this patent has significant advantages in performance. The tungsten wires in the examples are significantly superior to the comparative example in terms of tensile strength, torsional performance, resistivity and surface quality. For example, the tensile strength in the examples can reach 5500 - 6500 MPa, while that of the comparative example is only 3000 - 4000 MPa; the number of torsional turns in the examples is greater than 800 turns, while that of the comparative example is less than 500 turns; the resistivity in the examples is between 0.05 - 0.07 μΩ·m, while that of the comparative example is higher and unstable. This fully proves that the preparation method of this patent can effectively improve the comprehensive performance of tungsten wires and meet the requirements of high-performance applications.

[0079] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-performance plated tungsten wire, characterized in that, It includes a tungsten wire substrate which is prepared by a process of first hot drawing and then cold drawing. A transition layer, an intermediate strengthening layer and a functional alloy layer are sequentially arranged on its surface along the direction from inside to outside; The transition layer is a nickel metal layer or a cobalt metal layer with a thickness of 0.1 - 1 μm, which is used to enhance the bonding force between the intermediate strengthening layer and the tungsten wire substrate. The transition layer and the tungsten wire substrate are bonded by a metallic bond, and the bonding force is not less than 50 MPa; The intermediate strengthening layer is a nanocrystalline tungsten carbide layer or a nanocrystalline titanium nitride layer with a thickness of 0.2 - 0.8 μm, the nanocrystalline grain size is 10 - 50 nm, the hardness of the intermediate strengthening layer is 20 - 30 GPa, and the elastic modulus is 400 - 600 GPa; The functional alloy layer is one of a copper-zinc-aluminum alloy layer, a copper-nickel-silicon alloy layer, and a copper-tin-indium alloy layer, with a thickness of 0.5 - 5 μm. The weight percentage of copper element in the functional alloy layer is 50 - 75%. The functional alloy layer and the intermediate strengthening layer are bonded by diffusion, and the thickness of the diffusion layer is 0.05 - 0.2 μm; The diameter of the high-performance coated tungsten wire is 0.01 - 0.5 mm, the tensile strength is 5000 - 7000 MPa, the number of torsion turns is more than 800 turns, and the resistivity is 0.05 - 0.08 μΩ·m.

2. The high-performance plated tungsten wire according to claim 1, wherein The weight percentage of tungsten element in the tungsten wire matrix is 98.5-100%, the weight percentage of rare earth element is 0-1.5%, the rare earth element is one or more of lanthanum, cerium, and rhenium, the grain size of the tungsten wire matrix is 1-5μm, and the dislocation density is 10 12 -10 14 m -2 .

3. A method for preparing the high-performance plated tungsten wire according to any one of claims 1-2, characterized in that, It includes the following steps: S1: Raw material preparation and pretreatment: Select tungsten powder with a purity of 98.5 - 100%, uniformly mix it with a lubricant, and the mixing ratio is 100:1 - 100:

5. Then, perform cold isostatic pressing on the mixed powder in a vacuum environment, with a pressure of 150 - 300 MPa and a pressure holding time of 1 - 5 hours to obtain a tungsten rod blank. The average particle size of the tungsten powder is 1 - 10 μm, the particle size of the lubricant is 0.1 - 1 μm, the accuracy of the pressure control system of the cold isostatic pressing equipment is ±1 MPa, and the accuracy of the pressure holding time control system is ±0.1 hour. The mold of the cold isostatic pressing equipment is made of alloy steel, and the inner wall roughness of the mold is 0.1 - 0.3 μm; S2: Hot wire drawing: Heat the tungsten rod blank and then perform hot wire drawing until the diameter is about 80 μm; S3: Surface treatment and electroplating of the transition layer: The tungsten wire after hot drawing is subjected to surface treatment. First, chemical cleaning is used to remove surface oil stains and impurities. The caustic washing is carried out with a 5-10% sodium hydroxide solution, and the pickling is carried out with a 5-10% hydrochloric acid solution. The tungsten wire after chemical cleaning is protected by nitrogen during the drying process. Then, electrolytic polishing treatment is carried out. The polishing solution is a mixed solution of phosphoric acid and sulfuric acid to make the surface roughness of the tungsten wire reach 0.1-0.5 μm. After that, a transition layer is formed on the surface of the treated tungsten wire by electroplating. The electroplating solution is nickel chloride or nickel sulfamate solution, and 10-30 g / L of boric acid and 0.1-1 g / L of sodium dodecyl sulfate are added as buffer and wetting agent. The electroplating temperature is 40-60 °C, and the current density is 5-50 A / dm 2 , and the electroplating time is 10-60 minutes; S4: Cold wire drawing: Perform multi-pass cold wire drawing on the tungsten wire after electroplating the transition layer at room temperature. The number of drawing passes is 5 - 20 times, the deformation amount of each drawing pass is 5 - 20%, the drawing speed is 40 - 60 m / min, and draw it to a diameter of 10 - 40 μm. The drawing equipment uses a high-precision cold drawing machine. The material of the drawing die is cemented carbide (such as tungsten carbide), the working cone angle of the die is 6 - 12°, the surface roughness of the die is 0.05 - 0.2 μm, the length of the sizing zone is 2 - 5 mm, the surface hardness is 85 - 92 HRA. During the drawing process, an on-line detection device is used to monitor the diameter and surface quality of the tungsten wire in real time. The diameter measurement accuracy is ±0.005 mm, and the surface roughness measurement accuracy is ±0.1 μm; S5: Intermediate Reinforcement Layer Deposition: The intermediate reinforcement layer is deposited on the surface of the transition layer by physical vapor deposition (PVD). When the intermediate reinforcement layer is a nanocrystalline tungsten carbide layer, magnetron sputtering technology is used with tungsten carbide as the target, argon as the working gas, the gas pressure is 0.2 - 0.8 Pa, the sputtering power is 100 - 500 W, the deposition rate is 0.1 - 0.5 μm / h, and the deposition temperature is 100 - 300 °C. When the intermediate reinforcement layer is a nanocrystalline titanium nitride layer, ion plating technology is used with titanium nitride as the target, nitrogen and argon as the working gases, the gas pressure is 0.3 - 0.9 Pa, the ion plating voltage is 50 - 150 V, the deposition rate is 0.15 - 0.6 μm / h, and the deposition temperature is 150 - 350 °C. During the deposition process, the process parameters are controlled to make the nanocrystalline grain size of the intermediate reinforcement layer 10 - 50 nm, the thickness 0.2 - 0.8 μm, the hardness reach 20 - 30 GPa, and the elastic modulus 400 - 600 GPa. The ultimate vacuum degree of the vacuum system of the physical vapor deposition equipment is 1×10 -4 -1×10 -6 Pa, and the accuracy of the substrate bias power supply is ±5 V; S6: Electroplating of the functional alloy layer A functional alloy layer is formed on the surface of the intermediate reinforcement layer by electroplating. When the functional alloy layer is a copper-zinc alloy layer, the electroplating solution is a mixed solution of zinc oxide, copper sulfate, sodium hydroxide, and a complexing agent, and 1-5 ml / L of ammonia water is added to adjust the pH value to 9-11. The electroplating temperature is 20-40 °C, and the current density is 1-20 A / dm 2 ; when the functional alloy layer is a copper-tin alloy layer, the electroplating solution is a mixed solution of copper pyrophosphate, sodium stannate, and potassium pyrophosphate, and 0.1-1 g / L of gelatin is added as an additive; when the functional alloy layer is a copper-zinc-tin alloy layer, the electroplating solution is a mixed solution of copper sulfate, zinc sulfate, sodium stannate, and sodium hydroxide, the electroplating temperature is 20-30 °C, and the current density is 1-10 A / dm 2 ; the electroplating tank is made of corrosion-resistant polytetrafluoroethylene material, the electrodes are made of titanium plates or ruthenium-titanium plates, and the electrode spacing is 5-15 cm; S7: Post-treatment: The tungsten wire after plating is cleaned. First, it is rinsed with deionized water 3 - 5 times. The resistivity of the deionized water is greater than 18 MΩ·cm. Then, it is cleaned with ethanol in an ultrasonic cleaner for 10 - 30 minutes to remove the residual plating solution and impurities on the surface. During the drying process of the cleaned tungsten wire, vacuum drying or low dew point drying is adopted. Before packaging, the dried tungsten wire is protected by nitrogen filling, and the packaging material is a moisture-proof and antioxidant aluminum foil bag. Finally, vacuum heat treatment is carried out to eliminate internal stress.

4. The preparation method according to claim 3, characterized in that: In step S2, the heating system of the hot drawing equipment should have the function of uniform heating. During the hot wire drawing process, the grain size of the tungsten wire needs to be monitored in real time. The measurement accuracy of the grain size is ±0.1 μm, and the grain size of the drawn tungsten wire should be controlled within 8 - 12 μm. The measurement accuracy of the drawing force during hot wire drawing is ±2%, and an overload protection device is equipped. When the drawing force exceeds the set threshold, the drawing automatically stops to prevent the tungsten wire from breaking.

5. The preparation method according to claim 3, characterized in that: In step S3, a pure water rinsing link should be added between the alkali washing and acid washing steps during the chemical cleaning process. The rinsing time is 3 - 5 minutes to remove the residual cleaning solution from the previous step and prevent the acid-base neutralization reaction from affecting the cleaning effect. The electrolytic polishing equipment should have an electrolyte circulation filtration system with a filtration accuracy of 0.05 - 0.1 μm. During the intermediate layer electroplating process, the electroplating bath should be equipped with an automatic liquid level control system with a liquid level control accuracy of ±1 mm.

6. The preparation method according to claim 3, wherein: In step S4, the cold drawing machine should have an automatic lubrication system. The lubrication system automatically adjusts the supply amount of the lubricating fluid according to the drawing speed and drawing force to reduce the drawing force and reduce scratches on the surface of the tungsten wire. At the same time, the on-line detection device during the cold drawing process should have the function of automatic data recording and analysis, and generate the change curves of the tungsten wire diameter and surface quality in real time.

7. The preparation method according to claim 3, characterized in that: In step S5, the target cooling system of the physical vapor deposition equipment should have high-efficiency heat dissipation capacity to prevent the target from overheating, resulting in unstable sputtering or evaporation rates and affecting the quality of the intermediate strengthening layer. During the deposition process, the flow rate and pressure of the working gas should be monitored in real time. The physical vapor deposition equipment should be equipped with a film thickness monitoring system with a film thickness measurement accuracy of ±0.01 μm to monitor the deposition thickness of the intermediate strengthening layer in real time.

8. The preparation method according to claim 3, characterized in that: In step S6, the circulating filtration system adopted during the electroplating process should have a backwashing function. Backwashing is carried out once every 2 hours, and the backwashing time is 5 - 10 minutes. The temperature control system of the electroplating solution should have a fast response ability. When the temperature of the electroplating solution deviates from the set value by ±1℃, it is adjusted to the set temperature range within 1 - 2 minutes. At the same time, before electroplating the functional alloy layer, the surface of the intermediate strengthening layer is activated for 1 - 3 minutes to improve the bonding force between the functional alloy layer and the intermediate strengthening layer.

9. The preparation method according to claim 3, characterized in that: In step S7, the ultrasonic cleaning machine should have an automatic frequency adjustment function to optimize the ultrasonic frequency in real time according to the cleaning effect. The vacuum heat treatment equipment should have an atmosphere control system to introduce an appropriate amount of hydrogen during the heat treatment process to further remove the residual stress inside the tungsten wire. During the packaging process, the nitrogen filling protection system should ensure that the purity of nitrogen in the package is above 99.9% and the pressure is 0.05 - 0.1 MPa to prevent the tungsten wire from oxidizing during storage and transportation. At the same time, the packaged tungsten wire should be marked with product specifications, production date, and batch information.

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