A method of arc plasma production of tungsten-based alloys

Abstract

The application discloses a method for manufacturing tungsten-based alloy by arc plasma and belongs to the technical field of plasma-facing materials in fusion reactors. The method combines arc plasma and a hot-pressing Joule apparatus to manufacture tungsten-based alloy by taking tungsten wires and other metal wires as raw materials and performing the following steps: step one, fixing tungsten wires and other metal wires in a wire feeding system, adjusting the distance between the wires and a plasma arc nozzle, and feeding inert protective gas into the coaxial plasma nozzle; step two, starting the wire feeding system, starting the plasma arc, and dropping the molten metal droplets into a carbon mold; and step three, placing the carbon mold containing the tungsten-based alloy obtained in step two into the hot-pressing Joule apparatus to simultaneously pressurize and heat the tungsten-based alloy to obtain the tungsten-based alloy.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology for the first wall metal of fusion reactors, and in particular relates to a method for manufacturing tungsten-based alloys using electric arc plasma. Background Technology

[0002] Fusion reactors face extreme conditions such as high thermal loads and high-energy particles during operation, requiring materials with high-temperature strength, plasticity, and excellent radiation resistance. Tungsten-based alloys, due to their good mechanical properties and radiation resistance, have become a research hotspot for structural materials used in fusion reactors. However, because tungsten-based alloys contain multiple main elements with varying atomic radii, melting points, and other physicochemical properties, elemental segregation is prone to occur during preparation, making it difficult to ensure compositional homogeneity. This leads to inhomogeneous alloy properties, affecting their performance in fusion reactors. Furthermore, tungsten has a high melting point of 3410℃, and its densification typically requires reaching over 70% of its melting point temperature to achieve high density. However, tungsten has a relatively low recrystallization temperature, between 1150℃ and 1350℃, and the finer the grain, the lower the recrystallization temperature. This means that during sintering, the high temperatures required to achieve high density cause grain growth, making it difficult to simultaneously achieve high density and small grain size. To address the above issues, this invention employs a manufacturing method combining electric arc plasma and hot-pressing Joule apparatus. Electric arc plasma can melt high-melting-point tungsten and other metal wires, facilitating the formation of high-density alloys. The hot-pressing Joule apparatus (heating rate of 100~500℃ / s) differs from conventional sintering methods (0.5~50℃ / min) in that it has a faster heating rate and shorter sintering time, effectively suppressing grain growth in tungsten-based alloys during sintering, thus facilitating the formation of high-density, small-grained tungsten-based alloys. Summary of the Invention

[0003] To address the problems in the background art, this invention proposes a method for manufacturing tungsten-based alloy materials using electric arc plasma.

[0004] The technical solution of the present invention is as follows:

[0005] A method for manufacturing tungsten-based alloys using electric arc plasma includes the following steps:

[0006] Step 1: Fix the tungsten wire and other metal wire spools in the wire feeding system, adjust the distance between the wire and the plasma arc nozzle, and introduce inert protective gas coaxially into the plasma nozzle.

[0007] Step 2: Start the wire feeding system and turn on the plasma arc to drop molten metal droplets into the carbon mold at a distance of 5-10cm from the nozzle;

[0008] Step 3: Place the carbon mold containing tungsten-based alloy obtained in Step 2 into the vacuum chamber of the hot-pressing Joule apparatus, and proceed as follows:

[0009] Evacuate to 50~300Pa and heat to 700℃~1000℃ at a rate of 5~10℃ / s, and hold for 2~30min;

[0010] Inert gas is introduced, and the temperature is raised to 1800-2000℃ at a rate of 100-500℃ / s, held for 0.01-5h, and the pressure is 50-300MPa.

[0011] In the above technical solution, the other metal wires mentioned in step one include one or a combination of several of copper wire, titanium wire, molybdenum wire, rhenium wire, vanadium wire, tantalum wire, yttrium wire, and zirconium wire; the diameter of tungsten wire and other metal wires is 0.05mm~3mm, and the wire feeding speed is 3mm / s~20mm / s.

[0012] In the above technical solution, the inert protective gas mentioned in step one is one or a mixture of two of argon or helium, and the gas flow rate is 5L / min to 50L / min.

[0013] In the above technical solution, the parameters of the plasma arc discharge in step two are: input current 50A~300A, arc voltage 5V~20V.

[0014] In the above technical solution, the preferred temperature in step three is 700℃, and the preferred holding time is 2~30min.

[0015] In the above technical solution, the hot pressing Joule apparatus adopts a temperature gradient control of 5~10℃ / s during the stage of heating up to 700℃ to avoid alloy oxidation.

[0016] In the above technical solution, the carbon mold is made of graphite and is used to receive molten alloy droplets.

[0017] In the above technical solution, during the heat preservation stage of 1800~2000℃ in step three, the argon pressure is maintained at 50~300MPa, and the heating rate is 100~500℃ / s, preferably 500℃ / s.

[0018] In the above technical solution, the final tungsten-based alloy grain size is ≤5μm and the density is ≥99%.

[0019] Beneficial effects:

[0020] The advantages of this invention compared to the prior art are as follows:

[0021] 1) The use of inert gas as a conductive medium in the hot-press Joule apparatus avoids the oxidation of tungsten metal.

[0022] 2) The rapid heating rate in the hot-press Joule apparatus is higher than that in conventional sintering methods, which is beneficial for preparing smaller tungsten grains.

[0023] 3) The hardness of the prepared tungsten alloy was increased by 30-100%. Attached Figure Description

[0024] The preferred embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0025] Figure 1 This is a scanning electron microscope image of the tungsten-copper alloy of the present invention;

[0026] Figure 2 The figures show the hardness test results of tungsten-copper alloys, where (a) represents the hardness of the tungsten-copper alloy of the present invention, and (b) represents the hardness of conventional sintered tungsten-copper alloys. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0028] Example 1:

[0029] Tungsten and copper wires, each 1 mm in diameter, were fixed in the wire feeding system. The distance between the wires and the plasma arc nozzle was adjusted to 1 mm. Argon gas was coaxially introduced into the plasma nozzle as a protective gas at a flow rate of 5 L / min. The wire feeding system was started, the plasma arc was activated, and the input current was 100 A with an arc voltage of 5 V. Molten metal droplets were dropped into a carbon mold 5 cm from the nozzle. The resulting tungsten-based alloy carbon mold was placed in the vacuum chamber of a hot-press Joule apparatus, evacuated to 50 Pa, and heated to 700 °C at a rate of 5 °C / s, held for 120 s, then argon gas was introduced, and the temperature was increased to 1800 °C at a rate of 500 °C / s and a pressure of 300 MPa, held for 0.5 h.

[0030] Example 2:

[0031] Tungsten, copper, and titanium wires with a diameter of 1 mm were fixed in the wire feeding system. The distance between the wires and the plasma arc nozzle was adjusted to 5 mm. Helium gas was introduced coaxially into the plasma nozzle as a protective gas at a flow rate of 5 L / min. The wire feeding system was started, the plasma arc was activated, and the input current was 300 A with an arc voltage of 20 V. Molten metal droplets were dropped into a carbon mold 10 cm away from the nozzle. The carbon mold of the tungsten-based alloy prepared in the previous step was placed in the vacuum chamber of a hot-press Joule apparatus, evacuated to 300 Pa, heated to 700 °C at a rate of 10 °C / s, held for 1800 s, and then argon gas was introduced. The temperature was increased to 2000 °C at a rate of 500 °C / s and the pressure was 50 MPa, held for 5 h.

[0032] Test Results and Analysis:

[0033] like Figure 1 As shown, the tungsten-based alloy grains are granular with an average size ≤5μm and a density ≥99%. An arc plasma input current of 300A completely melts the metal wire, and the carbon mold rapidly cools to form a fine-grained preform. A hot-pressing Joule apparatus heats the material to 1800℃ at an ultra-high speed of 500℃ / s, achieving densification under a high pressure of 200MPa and a holding time of 0.5h, while simultaneously avoiding grain coarsening caused by prolonged high temperatures. This demonstrates that the rapid heating of the hot-pressing Joule apparatus effectively suppresses abnormal grain growth.

[0034] like Figure 2 As shown, Figure 2 (a) (the alloy of this invention): hardness value 249.89 HV0.3; Figure 2 (b) (Comparative example, elemental tungsten): Hardness value 186.08 HV0.3. Conclusion: Hardness improvement: The hardness of the tungsten-copper alloy of this invention is ≥240 HV0.3, which is 34.3% higher than that of conventionally synthesized tungsten-copper alloys. Figure 2 (a) vs Figure 2 (b)). Table 1 shows the densities of tungsten-copper alloys prepared by different methods.

[0035] Table 1 Density of tungsten-copper alloys prepared by different methods

[0036]

[0037] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. 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 this application. Therefore, this application 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 claimed herein.

Claims

1. A method for manufacturing tungsten-based alloys using electric arc plasma, characterized in that, Includes the following steps: Step 1: Fix the tungsten wire and other metal wire spools in the wire feeding system, adjust the distance between the wire and the plasma arc nozzle, and introduce inert protective gas coaxially into the plasma nozzle. Step 2: Start the wire feeding system and turn on the plasma arc to drop molten metal droplets into the carbon mold at a distance of 5-10cm from the nozzle; Step 3: Place the carbon mold containing tungsten-based alloy obtained in Step 2 into the vacuum chamber of the hot-pressing Joule apparatus, and proceed as follows: Evacuate to 50~300 Pa; Heat to 700℃~1000℃ at a rate of 5~10℃ / s, and hold for 2~30 minutes; Inert protective gas is introduced, and the temperature is raised to 1800~2000℃ at a heating rate of 100~500℃ / s, held for 0.01~5h, and the pressure is 50~300 MPa.

2. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, The other metal wires mentioned in step one include one or a combination of several of the following: copper wire, titanium wire, molybdenum wire, rhenium wire, vanadium wire, tantalum wire, yttrium wire, and zirconium wire.

3. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, In step one, the diameter of the tungsten wire and other metal wires is 0.05mm to 3mm.

4. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, In step one, the wire feeding speed is 3mm / s to 20mm / s.

5. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, The inert protective gas mentioned in step one is one or a mixture of two of argon or helium, and the gas flow rate is 5 L / min to 50 L / min.

6. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, The parameters for the plasma arc discharge described in step two are: input current 50A~300A, arc voltage 5V~20V.

7. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, The carbon mold is made of graphite and is used to receive molten alloy droplets.

8. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, In step three, the temperature range is 700℃~1000℃, the holding time is 2~30min, and a temperature gradient of 5~10℃ / s is used to avoid alloy oxidation.

9. The method for manufacturing tungsten-based alloys using arc plasma according to claim 1, characterized in that, The final tungsten-based alloy has a grain size of ≤5 μm and a density of ≥99%.

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