CN113290250A - Melt atomization preparation method of high-entropy alloy powder - Google Patents
Melt atomization preparation method of high-entropy alloy powder Download PDFInfo
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- CN113290250A CN113290250A CN202110610140.0A CN202110610140A CN113290250A CN 113290250 A CN113290250 A CN 113290250A CN 202110610140 A CN202110610140 A CN 202110610140A CN 113290250 A CN113290250 A CN 113290250A
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/14—Making metallic powder or suspensions thereof using physical processes using electric discharge
Abstract
The invention discloses a melt atomization preparation method of high-entropy alloy powder, which comprises the following steps: weighing metal powder with a certain atomic ratio, and putting the metal powder into a vacuum smelting furnace for smelting to form molten metal; introducing inert gas into the reaction atomization chamber, and starting a high-frequency pulse power supply to enable the plasma torch to discharge after the duration of 25 s; introducing nitrogen into a plasma torch to generate nitrogen plasma, conveying a metal bar to the lower part of a nozzle of the plasma torch, and directly melting the metal bar into metal liquid drops under the action of plasma flow; the molten metal droplets are broken under the impact of high-speed gas flow of the gas nozzle and are wrapped, clamped and rapidly move downwards to the surface of the centrifugal disc to form a layer of metal liquid film; the metal liquid film is split at the edge of a centrifugal disc rotating at a super high speed and is cooled in the flying process to form metal micro-nano sphere powder. The invention can more effectively impact and crush the molten metal through the supersonic plasma, and the probability of large-particle powder or powder clusters is reduced to the minimum.
Description
Technical Field
The invention relates to a melt atomization preparation method, in particular to a melt atomization preparation method of high-entropy alloy powder.
Background
The powder metal material may be formed by various methods, such as by water atomization, gas atomization, plasma atomization or spinning disks. A common atomization process involves applying a fluid (water, gas, oil or plasma) onto a molten metallic material to form a plurality of particles. The cooling rate of molten metal during water atomization is much faster than in gas atomization, which results in irregularly shaped particles that are generally unsuitable for metal injection molding, thermal spraying, additive manufacturing processes such as selective laser sintering, electron beam melting, three-dimensional printing and other manufacturing techniques, with spherical particles being more preferred. Thus, powder metal materials formed by water atomization are often used in typical pressing and sintering processes.
In recent years, the plasma discharge powder making technology is rapidly developed, and the metal powder prepared by the method has the characteristics of good sphericity, no crucible melting, small powder granularity and the like. Because the requirements on the quality stability of metal materials and powder are continuously improved, the metal powder meeting the requirements is difficult to prepare by the traditional plasma method, and the preparation and the wide application of the metal powder are seriously restricted.
Compared with the traditional technology for preparing metal powder by plasma, the combined powder preparation method based on plasma melting and disc rotation atomization is characterized in that a metal bar is directly melted by high-temperature ion current ionized by a plasma torch, and a metal liquid film on the surface of the metal bar is subjected to centrifugal splitting by a centrifugal disc rotating at a high speed. The method is not influenced by the characteristics of the metal powder raw material, and the particle size and the oxygen content of the metal powder can be effectively ensured. In addition, unlike traditional gas jetting, the nozzle uses super high speed gas to change the motion locus of molten metal drop, so that the molten metal drop moves fast to the surface of the centrifugal disc and forms one stable metal liquid film for easy formation of fibrous centrifugal separation.
However, in the existing preparation method of high-entropy alloy powder, because the diameter of a metal bar is large, the volume of a metal molten drop formed in the melting process is large, the molten drop cannot be effectively split in the centrifugal atomization process, the particle size of the metal powder is difficult to guarantee, the powder preparation with stable quality cannot be realized, and the sphericity of the metal powder cannot be effectively guaranteed.
Disclosure of Invention
In order to overcome the defects of the technology, the invention provides the high-performance high-entropy alloy powder with ultra-fine particle size, high sphericity, low hollow rate, low oxygen content and excellent grain structure, and provides the melt atomization preparation method of the high-entropy alloy powder.
In order to solve the technical problems, the invention adopts the technical scheme that: a melt atomization preparation method of high-entropy alloy powder comprises the following steps:
s1, weighing metal powder with a certain atomic ratio, uniformly mixing, and putting into a vacuum melting furnace for melting to form molten metal;
s2, preheating inert gas to 220-250 ℃, introducing the inert gas into the reaction atomization chamber to extrude air in the atomization chamber, and starting a high-frequency pulse power supply to enable the plasma torch to discharge after the duration of 25S;
s3, introducing nitrogen into a plasma torch to generate nitrogen plasma, enabling the nitrogen plasma to enter a reaction atomization nozzle to form a 360-degree annular plasma beam, enabling the 360-degree annular plasma beam to form an atomization focus in the reaction atomization chamber, conveying a metal bar stock to the lower part of the plasma torch nozzle, and directly melting the metal bar stock into metal liquid drops under the action of plasma flow, wherein the aperture of a liquid outlet is 5.5mm, and the flow velocity of a melt flowing out of the liquid outlet is 12-16 kg/min;
s4, adding an additive into the molten metal droplets, wherein the additive forms a protective gas atmosphere surrounding the molten metal droplets, and the molten metal droplets are broken under the impact of high-speed gas flow of a gas nozzle and are wrapped to move downwards and quickly to the surface of a centrifugal disc to form a layer of metal liquid film;
s5, the metal liquid film is split at the edge of the centrifugal disc rotating at a super high speed and is cooled in the flying process to form metal micro/nano sphere powder.
Preferably, in step S1, the gas ionized by the plasma torch is an inert gas including any one or a combination of helium and argon.
Preferably, in step S2, the gas nozzle injects a gas to impact the molten metal droplets in a linear direction and in a multi-directional turbulent manner; the gas sprayed is inert gas, including any one or combination of helium and argon.
Preferably, the output power of the plasma torch is 250-550 kw; the rotation speed range of the centrifugal disc is 7000 and 70000 rpm.
Preferably, the metal bar stock is a metal bar stock or an alloy bar stock of iron, cobalt, nickel, copper.
Preferably, the additive includes at least one of K, Na, Zn, Mg, Li, Sr, Ca and Ba.
Preferably, the prepared metal micro-nano sphere powder is solid sphere powder with the particle size distribution of 30-110 microns, the sphericity of more than 95% and the oxygen content of less than 0.04%.
The invention has the advantages that the plasma heat source is utilized to directly melt the metal bar, thereby avoiding the contact of the crucible to pollute the molten metal; inert gas is used as a gas source, so that the oxygen content of the metal powder is effectively reduced, and the influence of the micro segregation of elements on the surface structure performance of the powder is reduced; the supersonic plasma can more effectively impact and crush the molten metal, and the probability of large-particle powder or powder clusters is reduced to the minimum; the metal liquid film is centrifugally split by the aid of the disc, the problem that the particle size distribution range is large after centrifugal atomization of traditional metal molten drops is solved, and the stability of powder quality can be further guaranteed by centrifugal secondary splitting of the disc.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
A melt atomization preparation method of high-entropy alloy powder comprises the following steps:
s1, weighing metal powder with a certain atomic ratio, uniformly mixing, and putting into a vacuum melting furnace for melting to form molten metal;
s2, preheating inert gas to 220-250 ℃, introducing the inert gas into the reaction atomization chamber to extrude air in the atomization chamber, and starting a high-frequency pulse power supply to enable the plasma torch to discharge after the duration of 25S; the expansion of the inert gas medium is increased by preheating, so that the using amount of the inert gas medium is saved, and the production cost is saved.
S3, introducing nitrogen into a plasma torch to generate nitrogen plasma, enabling the nitrogen plasma to enter a reaction atomization nozzle to form a 360-degree annular plasma beam, enabling the 360-degree annular plasma beam to form an atomization focus in the reaction atomization chamber, conveying a metal bar stock to the lower part of the plasma torch nozzle, and directly melting the metal bar stock into metal liquid drops under the action of plasma flow, wherein the aperture of a liquid outlet is 5.5mm, and the flow velocity of a melt flowing out of the liquid outlet is 12-16 kg/min;
the supersonic jet atomization is carried out by utilizing the 360-degree annular plasma, firstly, the high-temperature characteristic of the plasma ensures that the molten metal cannot be condensed in advance in the process of impact atomization, and the shape of liquid drops can be better controlled; secondly, 360 degrees surround the mode of evenly spraying atomizing, can guarantee that the metal liquid surface is by abundant impact atomization, has avoided the uneven problem of impact atomization in conventional single beam, 3 bundles of plasma atomization, and the particle size distribution of final assurance liquid drop is less.
Through improving atomizing gaseous medium temperature, reduce the bore of smelting mechanism liquid outlet and reduce the fuse-element flow, reduce the mutual violent collision between the initial breakage of fuse-element, promote the fuse-element and form the surface energy of powder in gas atomization flight process, reduce the cooling rate of fuse-element in the atomizing process to obtain high powder yield and high sphericity.
S4, adding an additive into the molten metal droplets, wherein the additive forms a protective gas atmosphere surrounding the molten metal droplets, and the molten metal droplets are broken under the impact of high-speed gas flow of a gas nozzle and are wrapped to move downwards and quickly to the surface of a centrifugal disc to form a layer of metal liquid film;
s5, the metal liquid film is split at the edge of the centrifugal disc rotating at a super high speed and is cooled in the flying process to form metal micro/nano sphere powder.
In step S1, the gas ionized by the plasma torch and the gas injected by the gas nozzle are inert gases, including any one or a combination of helium and argon. Compared with air or other active gases, the inert gas is beneficial to avoiding the oxidation of metal molten drops in the melting process, and meanwhile, the influence of the segregation of microscopic elements on the surface of the powder on the quality stability of the powder can be reduced under the protection of the inert gas. According to the physical characteristics of the metal bar, the gas ionized by the plasma torch and the gas sprayed by the gas nozzle can be gases with the same property or different properties, the gas at the nozzle can be inert gas which is easy to ionize and has small influence on metal molten drop elements, and the selection of the gas at the nozzle can be selected according to the characteristic of metal molten drop heat change, so that the metal powder preparation with high efficiency, high quality and stability is realized.
In step S2, the gas nozzle injects gas to impact the molten metal droplets in a linear direction and in a multi-directional disturbance manner; the centrifugal plate is beneficial to realizing multi-directional gas injection to a melting area, further changing the motion track of scattered metal droplets around and ensuring that the droplets quickly fly to the surface of the centrifugal plate.
Specifically, the output power of the plasma torch is 250-550 kw; the method not only can melt any conventional metal such as iron, cobalt, nickel, copper and the like, but also can melt difficult-to-process materials such as cobalt-based high-temperature alloy and the like, and has no special requirements on the characteristics of powder raw materials.
Specifically, the rotation speed range of the centrifugal disc is 7000-70000 rpm. Is favorable for ensuring the fibrous division of the metal liquid film on the surface of the centrifugal disc and further realizing the narrow particle size distribution and better sphericity of the metal powder.
Specifically, the metal bar stock is a metal bar stock or an alloy bar stock of iron, cobalt, nickel and copper.
Specifically, the additive includes at least one of K, Na, Zn, Mg, Li, Sr, Ca, and Ba. Additives added to the molten material will create a protective atmosphere that will act as a barrier to prevent impurities such as sulfur (S) and/or oxygen (O2) from entering or re-entering the molten metal material, pushing the impurities away from the molten material as the protective gas flows out of the melt. The additive forming the protective gas atmosphere can also react with dissolved sulphur in the melt and/or suspended oxides in the melt before the introduction of the additive.
The prepared metal micro-nano sphere powder is solid sphere powder with the particle size distribution of 30-110 microns, the sphericity of more than 95% and the oxygen content of less than 0.04%.
The present invention will be described in further detail with reference to specific examples.
A melt atomization preparation method of high-entropy alloy powder comprises the following steps:
s1, weighing metal powder with a certain atomic ratio, uniformly mixing, and putting into a vacuum melting furnace for melting to form molten metal;
s2, preheating inert gas to 225 ℃, introducing the inert gas into the reaction atomization chamber to extrude air in the atomization chamber, and starting a high-frequency pulse power supply to enable the plasma torch to discharge after the duration of 25S; the output power of the plasma torch is 550 kw;
s3, introducing nitrogen into a plasma torch to generate nitrogen plasma, enabling the nitrogen plasma to enter a reaction atomization nozzle to form a 360-degree annular plasma beam, enabling the 360-degree annular plasma beam to form an atomization focus in the reaction atomization chamber, conveying a metal bar material to the lower part of the plasma torch nozzle, and directly melting the metal bar material into metal liquid drops under the action of plasma flow, wherein the aperture of a liquid outlet is 5.5mm, and the flow velocity of a liquid flow of a melt flowing out of the liquid outlet is 16 kg/min;
s4, adding an additive into the molten metal droplets, wherein the additive forms a protective gas atmosphere surrounding the molten metal droplets, and the molten metal droplets are broken under the impact of high-speed gas flow of a gas nozzle and are wrapped to move downwards and quickly to the surface of a centrifugal disc to form a layer of metal liquid film; the rotating speed of the centrifugal disc is 70000rpm
S5, the metal liquid film is split at the edge of the centrifugal disc rotating at a super high speed and is cooled in the flying process to form metal micro/nano sphere powder.
The prepared metal micro-nano sphere powder is solid sphere powder with the granularity of 110 microns, the sphericity of more than 95 percent and the oxygen content of less than 0.04 percent.
The above embodiments are not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make variations, modifications, additions or substitutions within the technical scope of the present invention.
Claims (7)
1. A melt atomization preparation method of high-entropy alloy powder is characterized by comprising the following steps: the method comprises the following steps:
s1, weighing metal powder with a certain atomic ratio, uniformly mixing, and putting into a vacuum melting furnace for melting to form molten metal;
s2, preheating inert gas to 220-250 ℃, introducing the inert gas into the reaction atomization chamber to extrude air in the atomization chamber, and starting a high-frequency pulse power supply to enable the plasma torch to discharge after the duration of 25S;
s3, introducing nitrogen into a plasma torch to generate nitrogen plasma, enabling the nitrogen plasma to enter a reaction atomization nozzle to form a 360-degree annular plasma beam, enabling the 360-degree annular plasma beam to form an atomization focus in the reaction atomization chamber, conveying a metal bar stock to the lower part of the plasma torch nozzle, and directly melting the metal bar stock into metal liquid drops under the action of plasma flow, wherein the aperture of a liquid outlet is 5.5mm, and the flow velocity of a melt flowing out of the liquid outlet is 12-16 kg/min;
s4, adding an additive into the molten metal droplets, wherein the additive forms a protective gas atmosphere surrounding the molten metal droplets, and the molten metal droplets are broken under the impact of high-speed gas flow of a gas nozzle and are wrapped to move downwards and quickly to the surface of a centrifugal disc to form a layer of metal liquid film;
s5, the metal liquid film is split at the edge of the centrifugal disc rotating at a super high speed and is cooled in the flying process to form metal micro/nano sphere powder.
2. The melt atomization preparation method of high-entropy alloy powder according to claim 1, characterized in that: in step S1, the gas ionized by the plasma torch is an inert gas, which includes any one or a combination of helium and argon.
3. The melt atomization preparation method of high-entropy alloy powder according to claim 2, characterized in that: in step S2, the gas nozzle injects gas to impact the molten metal droplets in a linear direction and in a multi-directional disturbance manner; the gas sprayed is inert gas, including any one or combination of helium and argon.
4. The melt atomization preparation method of high-entropy alloy powder according to claim 3, characterized in that: the output power of the plasma torch is 250-550 kw; the rotating speed range of the centrifugal disc is 7000 and 70000 rpm.
5. The melt atomization preparation method of high-entropy alloy powder according to claim 4, characterized in that: the metal bar stock is a metal bar stock or an alloy bar stock of iron, cobalt, nickel and copper.
6. A melt atomization preparation method of high-entropy alloy powder according to claim 5, characterized in that: the additive includes at least one of K, Na, Zn, Mg, Li, Sr, Ca, and Ba.
7. A melt atomization preparation method of high-entropy alloy powder according to claim 5, characterized in that: the prepared metal micro-nano sphere powder is solid sphere powder with the particle size distribution of 30-110 microns, the sphericity of more than 95% and the oxygen content of less than 0.04%.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115194170A (en) * | 2022-07-21 | 2022-10-18 | 季华实验室 | Plasma atomization deposition method and equipment |
| CN115255390A (en) * | 2022-09-26 | 2022-11-01 | 中国人民解放军北部战区总医院 | Preparation method of zirconium-based amorphous alloy self-expansion aorta covered stent based on SLM |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115194170A (en) * | 2022-07-21 | 2022-10-18 | 季华实验室 | Plasma atomization deposition method and equipment |
| CN115255390A (en) * | 2022-09-26 | 2022-11-01 | 中国人民解放军北部战区总医院 | Preparation method of zirconium-based amorphous alloy self-expansion aorta covered stent based on SLM |
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