Method for manufacturing tungsten-based alloy through arc plasma

Abstract

The invention discloses a method for manufacturing tungsten-based alloy by using arc plasma, which belongs to the technical field of plasma-oriented materials in fusion reactors, and adopts a manufacturing method combining the arc plasma and a hot-pressing Joule apparatus, and tungsten filaments and other metal wires are used as raw materials to prepare the tungsten-based alloy by using the arc plasma and the hot-pressing Joule apparatus. The method comprises the following steps that firstly, a tungsten wire and other metal wire discs are fixed in a wire feeding system, the distance between the wire and a plasma arc nozzle is adjusted, and inert protective gas is coaxially introduced into the plasma nozzle; secondly, a wire feeding system is started, a plasma arc is started, and molten metal drops fall into a carbon mold; and thirdly, the carbon mold containing the tungsten-based alloy obtained in the second step is put into a hot-pressing Joule instrument, the tungsten-based alloy is pressurized and heated at the same time, and the tungsten-based alloy is obtained.

Description

Technical Field

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

[0002] Fusion reactors operate under extreme conditions such as high heat loads and high-energy particles, requiring materials with high-temperature strength, ductility, and excellent radiation resistance. Tungsten-based alloys, due to their excellent mechanical properties and radiation resistance, have become a research hotspot for fusion reactor structural materials. Because tungsten-based alloys contain multiple main elements, each with varying physical and chemical properties such as atomic radius and melting point, element segregation is prone to occur during the preparation process, making it difficult to ensure compositional uniformity. This leads to uneven alloy properties, compromising its performance in fusion reactors. Furthermore, tungsten has a high melting point of 3410°C, and sintering densification typically requires temperatures exceeding 70% of the melting point to achieve high density. However, tungsten has a relatively low recrystallization temperature, ranging from 1150°C to 1350°C, and the finer the grain size, the lower the recrystallization temperature. Consequently, the high temperatures required to achieve high density during sintering cause grain growth, making it difficult to simultaneously achieve high density and small grain size. To address the above issues, the present invention adopts a manufacturing method that combines arc plasma and hot-pressing Joule meter. Arc plasma can melt high-melting-point tungsten and other metal wires, easily forming high-density alloys. The hot-pressing Joule meter (heating rate of 100-500°C / s) is different from the conventional sintering method (0.5-50°C / min). Its fast heating rate and short sintering time can effectively suppress the grain growth of tungsten-based alloys during the sintering process, thus easily forming high-density small-grain tungsten-based alloys. Summary of the Invention

[0003] In order to solve the problems in the background technology, the present invention proposes a tungsten-based alloy material manufactured by arc plasma and a preparation method thereof.

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

[0005] A method for producing a tungsten-based alloy using arc plasma, comprising the following steps:

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

[0007] Step 2: Start the wire feeding system, turn on the plasma arc, and drop the molten metal droplets into the carbon mold 5-10 cm away 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 meter and perform the following steps in sequence:

[0009] Evacuate to 50-300 Pa, then heat to 700-1000°C at a rate of 5-10°C / s, and keep warm for 2-30 minutes;

[0010] Inert gas is introduced, and the temperature is increased to 1800~2000℃ at a heating rate of 100~500℃ / s, and kept at this temperature for 0.01~5h. The pressure is 50~300MPa.

[0011] In the above technical solution, the other metal wires described in step one include one or a combination of copper wire, titanium wire, molybdenum wire, rhenium wire, vanadium wire, tantalum wire, yttrium wire, and zirconium wire; the diameter of the 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 in step 1 is argon or helium, or a mixture of the two, and the gas flow rate is 5 L / min to 50 L / min.

[0013] In the above technical solution, the parameters of the plasma arc discharge in step 2 are: input current 50A~300A, arc voltage 5V~20V.

[0014] In the above technical solution, the temperature in step 3 is preferably 700° C. and the holding time is preferably 2 to 30 minutes.

[0015] In the above technical solution, a gradient temperature control of 5~10℃ / s is adopted when the hot pressing joule analyzer is heated 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 1800-2000°C insulation stage in step three, the argon pressure is maintained at 50-300 MPa, and the heating rate is 100-500°C / s, preferably 500°C / s.

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

[0019] Beneficial effects:

[0020] The beneficial effects of the present invention compared to the prior art are:

[0021] 1) Inert gas is used as the conducting medium in the hot pressure joulemeter to avoid oxidation of tungsten metal.

[0022] 2) The rapid heating rate in the hot pressing joule analyzer is higher than that in conventional sintering, so it is beneficial for preparing smaller tungsten grains.

[0023] 3) The hardness of the prepared tungsten alloy is increased by 30~100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The preferred embodiments of the present invention will be described in further detail below 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 1 is a graph showing the hardness test results of tungsten-copper alloy, wherein (a) is the hardness of the tungsten-copper alloy of the present invention, and (b) is the hardness of a conventional sintered tungsten-copper alloy. DETAILED DESCRIPTION

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

[0028] Example 1:

[0029] A tungsten wire and a copper wire, each with a diameter of 1 mm, were fixed to a wire feeding system. The distance between the wire and the plasma arc nozzle was adjusted to 1 mm. Argon was coaxially introduced into the plasma nozzle as a shielding gas at a gas flow rate of 5 L / min. The wire feeding system was started, and the plasma arc was initiated with an input current of 100 A and an arc voltage of 5 V. A droplet of molten metal was 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-pressing Joulemeter, evacuated to 50 Pa, and heated to 700°C at a rate of 5°C / s. The temperature was then maintained for 120 seconds. Argon was then introduced, and the temperature was increased to 1800°C at a rate of 500°C / s. The pressure was then reduced to 300 MPa and maintained for 0.5 h.

[0030] Example 2:

[0031] Fix tungsten wire, copper wire and titanium wire with a diameter of 1mm in the wire feeding system, adjust the distance between the wire and the plasma arc nozzle to 5mm, and coaxially introduce helium as a protective gas into the plasma nozzle with a gas flow rate of 5L / min. Start the wire feeding system, turn on the plasma arc, input current of 300A, and arc voltage of 20V. Let the molten metal droplet fall into the carbon mold at a distance of 10cm from the nozzle. Place the carbon mold of the tungsten-based alloy prepared in the previous step into the vacuum chamber of the hot pressing Joule instrument, evacuate to 300Pa, heat to 700℃ at a rate of 10℃ / s, keep warm for 1800s, then introduce argon, heat to 2000℃ at a heating rate of 500℃ / s, pressure of 50MPa, and keep warm for 5h.

[0032] Test results and analysis:

[0033] like Figure 1 As shown, the tungsten-based alloy grains are granular, with an average size of ≤5μm and a density of ≥99%. 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 Joules instrument heats the preform at an ultra-high speed of 500°C / s to 1800°C. Densification is achieved under high pressure of 200MPa and a 0.5h hold, while avoiding grain coarsening caused by prolonged high temperatures. This demonstrates that the rapid heating of the hot-pressing Joules instrument effectively suppresses abnormal grain growth.

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

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

[0036] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present 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 the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for producing a tungsten-based alloy by arc plasma, characterized in that: The following steps are involved: Step 1: Fix the tungsten wire and other metal wire reels in the wire feeding system, adjust the distance between the wire and the plasma arc nozzle, and coaxially introduce inert shielding gas into the plasma nozzle; Step 2: Start the wire feeding system, turn on the plasma arc, and drop the molten metal droplets into the carbon mold 5-10 cm away 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 meter and perform the following steps in sequence: Vacuum to 50~300Pa; Heat up to 700-1000°C at a rate of 5-10°C / s and keep warm for 2-30 minutes; Inert gas is introduced, and the temperature is increased to 1800~2000℃ at a heating rate of 100~500℃ / s, and kept at this temperature for 0.01~5h. The pressure is 50~300MPa.

2. The method for producing tungsten-based alloy by arc plasma according to claim 1, characterized in that: The other metal wires described in step 1 include one or a combination of copper wire, titanium wire, molybdenum wire, rhenium wire, vanadium wire, tantalum wire, yttrium wire, and zirconium wire.

3. The method for producing tungsten-based alloy by arc plasma according to claim 1, characterized in that: The diameter of the tungsten wire and other metal wires in step 1 is 0.05mm~3mm.

4. The method for producing tungsten-based alloy by arc plasma according to claim 1, characterized in that: In step 1, the wire feeding speed is 3 mm / s to 20 mm / s.

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

6. The method for producing tungsten-based alloy by arc plasma according to claim 1, characterized in that: The parameters of the plasma arc discharge in step 2 are: input current 50A~300A, arc voltage 5V~20V.

7. The method for producing tungsten-based alloy by 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 producing tungsten-based alloy by arc plasma according to claim 1, characterized in that: In step 3, the temperature range is 700°C to 1000°C, the holding time is preferably 2 to 30 minutes, and a gradient temperature control of 5 to 10°C / s is used to avoid alloy oxidation.

9. The method for producing tungsten-based alloy by arc plasma according to claim 1, characterized in that: In step 3, during the 1800-2000°C holding stage, the inert gas pressure is 50-300 MPa; the heating rate is 100-500°C / s, and the holding time is 0.01-5 hours.

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

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