CN113046585B - Preparation method and application of high-entropy alloy for extremely cold environment - Google Patents

Abstract

The invention discloses a preparation method and application of a high-entropy alloy for an extremely cold environment. (1) Mixing cobalt, chromium, iron, nickel and manganese according to atomic percentage to obtain mixed metal powder; (2) melting the mixed metal powder into molten metal; (3) coating a lubricant in the mold in the deposition cavity, and introducing inert gas after drying; (4) injecting molten metal into a molten metal bag, introducing inert gas, and performing atomization deposition on the molten metal in a mold to obtain a high-entropy alloy ingot; (5) placing the high-entropy alloy ingot in a vacuum heating furnace for heat treatment and water cooling; (6) then, carrying out hot extrusion on the high-entropy alloy ingot to obtain a high-entropy alloy bar; (7) removing oxide skin on the surface of the high-entropy alloy bar; (8) and then placing the high-entropy alloy bar in a vacuum nitriding device, introducing mixed gas of argon and nitrogen for nitriding treatment, and forming a nitriding layer on the surface of the high-entropy alloy bar to obtain the high-entropy alloy for the extremely cold environment. The application comprises the following steps: the obtained high-entropy alloy is used as polar region mining and drilling equipment.

Description

Preparation method and application of high-entropy alloy for extremely cold environment

technical field

The invention relates to the technical field of high-entropy alloys, in particular to a preparation method and application of a high-entropy alloy for extremely cold environments.

Background technique

In recent years, with the continuous advancement of industrialization and the increase of population, the demand for energy has continued to increase, and the excessive production of energy in land, offshore and deep sea areas has led to a global energy shortage. The scope of human exploration of energy has gradually expanded to the Antarctic and Arctic circles. The Arctic is recognized by scientists as a place to store future energy, and oil and gas resources have been developed centered on countries adjacent to the Arctic Circle. Under the action of alternating stress for a long time, the steel used for mining and drilling in polar regions has an increased tendency to fracture and failure at low temperature, and the steel becomes brittle and more prone to brittle fracture failure. In recent years, my country has carried out large-scale scientific research work in the Antarctic and Arctic regions, and the minimum temperature of the environment has reached -80 °C. Therefore, while improving the strength of steel, it is also necessary to ensure a certain low temperature toughness and plasticity, and the existing materials are difficult to effectively meet the requirements of use, and a metal material with toughness and fatigue fracture characteristics at extremely low temperature is urgently needed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a high-entropy alloy for extremely cold environments, the CoCrFeNiMn high-entropy alloy prepared by the method of the present invention has high hardness and high low-temperature toughness, and can be used for mining in polar regions and steel for drilling equipment .

The present invention is achieved through the following technical solutions:

A preparation method of high-entropy alloy for extremely cold environment, comprising the following steps:

(1) Mixing powder: mix cobalt, chromium, iron, nickel, manganese elemental powder according to the atomic percentage of the high-entropy alloy to obtain mixed metal powder;

(2) smelting: melting the mixed metal powder to obtain molten metal;

(3) Apply lubricant: apply lubricant in the circular mold on the worktable in the deposition cavity, and after drying, introduce an inert gas to form a protective atmosphere;

(4) deposition: the molten metal is injected into the molten metal bag and an inert gas is introduced, and the molten metal is atomized and deposited in the mold to obtain a CoCrFeNiMn high-entropy alloy ingot;

(5) homogenization treatment: the CoCrFeNiMn high-entropy alloy ingot is placed in a vacuum heating furnace for heat treatment, and then water-cooled;

(6) hot extrusion: the CoCrFeNiMn high-entropy alloy ingot after the homogenization treatment is hot-extruded to obtain a CoCrFeNiMn high-entropy alloy rod;

(7) descaling: remove the oxide scale on the surface of the CoCrFeNiMn high-entropy alloy bar;

(8) Nitriding treatment: place the descaled CoCrFeNiMn high-entropy alloy bar in a vacuum nitriding device, and introduce a mixed gas of argon and nitrogen for high-temperature nitriding treatment. A nitrided layer is formed on the surface of the alloy bar, that is, a CoCrFeNiMn high-entropy alloy for extremely cold environments is obtained.

Further, in step (1), the atomic percentages of the cobalt, the chromium, the iron, the nickel and the manganese are 1:1:1:1:1; the cobalt, the chromium, the The purity of the iron, the nickel and the manganese was 99.9%.

Further, step (2) smelting: adding the mixed metal powder into the crucible smelting furnace of the spray deposition equipment and melting at 1500-1600° C. to obtain molten metal.

Further, the lubricant described in step (3) is water-based colloidal graphite, DFY-1 type fat-based paint or spindle oil; the inert gas is argon, and the flow rate of the argon is 80-100sccm .

Further, step (4) deposition: the molten metal is injected into the molten metal bag and argon gas of 0.9-1.2 MPa is passed in, the molten metal is atomized through a nozzle with a diameter of φ3±0.05mm, and the metal The liquid was atomized and deposited in a circular mold to obtain CoCrFeNiMn high-entropy alloy ingots with a size of φ50cm×80cm.

Further, step (5) homogenization treatment: the CoCrFeNiMn high-entropy alloy ingot is placed in a vacuum heating furnace at 900-1100°C for heat treatment for 6-12 hours; the water cooling temperature is 0-20°C.

Further, step (6) hot extrusion: the homogenized CoCrFeNiMn high-entropy alloy ingot is preheated at 800-900 ° C for 8-10 hours, and then hot extrusion is performed, and the extrusion ratio is 10- 20, the extrusion speed is 1-3mm/s; the CoCrFeNiMn high-entropy alloy rod is obtained.

Further, step (7) descaling: remove 1-1.5mm of oxide scale on the surface of the CoCrFeNiMn high-entropy alloy bar by a numerically controlled lathe.

Further, the temperature of the nitriding treatment in step (8) is 500-1000 ° C, and the nitriding treatment time is 2-12 hours; the flow rate of the argon gas is 40-100 sccm, and the flow ratio of the argon gas to the nitrogen gas is 1 : (0.2-1); the thickness of the nitride layer is 2-3mm.

An application of high-entropy alloys for extremely cold environments, the high-entropy alloys prepared by the above preparation method are used as steel materials for mining and drilling equipment in polar regions.

Beneficial effects of the present invention:

The CoCrFeNiMn high-entropy alloy for extremely cold environment prepared by the method of the invention has a uniform and dense structure, and the small grain size is about 20-30 μm. The dense structure has few defects, so the prepared CoCrFeNiMn high-entropy alloy has high tensile strength. In addition, at low temperature, the stacking fault energy of CoCrFeNiMn decreases with the temperature, and the deformation mechanism of the alloy changes, from dislocation slip to twinning process, which avoids the occurrence of cold brittle fracture due to dislocation plugging. High low temperature toughness. The preparation method of the invention is completed by spray forming and nitriding technology, the method has high production efficiency, is conducive to large-scale production to obtain large-sized alloy ingots, and the prepared high-entropy alloy bar has a high-hardness surface and high low-temperature toughness. , which can be used as steel for mining and drilling equipment in polar regions. In the preparation method of the present invention, before the nitriding treatment, the surface of the CoCrFeNiMn high-entropy alloy bar has a large amount of turning to remove the oxide layer, which is conducive to the solid solution of nitrogen atoms into the alloy; in addition, the high-entropy alloy composition of the present invention contains relatively high atoms. The percentage of manganese element is also conducive to the solid solution of nitrogen atoms into the alloy, so a thicker nitride layer can be formed, which further improves the hardness and low temperature toughness of the obtained alloy.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

A preparation method of high-entropy alloy for extremely cold environment, comprising the following steps:

(1) Mixing powder: uniformly mix cobalt, chromium, iron, nickel, and manganese elemental powder according to the atomic percentage of the high-entropy alloy to obtain mixed metal powder; the cobalt, the chromium, the iron, the nickel and the atomic percentage of the manganese is 1:1:1:1:1; the purity of the cobalt, the chromium, the iron, the nickel and the manganese is 99.9%;

(2) smelting: the above mixed metal powder is poured into the crucible melting furnace of the spray deposition equipment and melted at 1500 ° C to obtain molten metal;

(3) Coating lubricant: coating water-agent colloidal graphite lubricant in the circular mold on the worktable in the deposition cavity, and feeding high-purity argon gas after drying to form a protective atmosphere; and the argon gas flow rate is 100sccm;

(4) Deposition: The above-mentioned molten metal is injected into the molten metal bag and high-purity argon gas of 1.2 MPa is passed in, the molten metal is atomized through a nozzle with a diameter of φ3mm, and the molten metal is atomized and deposited on a circular mold Inside, a CoCrFeNiMn high-entropy alloy ingot with a size of φ50cm×80cm was obtained;

(5) homogenization treatment: the obtained CoCrFeNiMn high-entropy alloy ingot is placed in a vacuum heating furnace at 1000 ° C for heat treatment for 12 hours, and then placed in 20 ° C of water for cooling;

(6) Hot extrusion: Preheat the homogenized CoCrFeNiMn high-entropy alloy ingot at 800 °C for 8 hours, and then perform hot extrusion, the extrusion ratio is 10, and the extrusion speed is 3 mm/s; Obtain CoCrFeNiMn high-entropy alloy rods;

(7) Descale: remove the 1.0mm-thick scale on the surface of the CoCrFeNiMn high-entropy alloy bar by a numerically controlled lathe;

(8) Nitriding treatment: the CoCrFeNiMn high-entropy alloy bar after descaling was placed in a vacuum nitriding device, and a mixed gas of argon and nitrogen was introduced for nitriding treatment at 600° C. for 12 hours. A nitrided layer is formed on the surface of the CoCrFeNiMn high-entropy alloy bar to obtain a CoCrFeNiMn high-entropy alloy for extremely cold environments; and the flow rate of argon gas introduced is 40sccm, and the flow ratio of argon gas to nitrogen gas is 1:0.2.

Test: The surface hardness of the CoCrFeNiMn high-entropy alloy for extreme cold environment obtained in the above-mentioned Example 1 was measured by a hardness tester to be 8GPa; the tensile strength measured by the tensile test in liquid nitrogen (-196°C) was 802MPa, and the elongation was 68%; it can be seen that The high-entropy alloy prepared by the invention has good elongation at extremely low temperature and good low-temperature toughness on the surface.

Application: The CoCrFeNiMn high-entropy alloy prepared by the present invention has a high hardness surface and high low temperature toughness, and can be used as steel for mining and drilling equipment in polar regions.

Example 2

A preparation method of high-entropy alloy for extremely cold environment, comprising the following steps:

(1) Mixing powder: uniformly mix cobalt, chromium, iron, nickel, and manganese elemental powder according to the atomic percentage of the high-entropy alloy to obtain mixed metal powder; the cobalt, the chromium, the iron, the nickel and the atomic percentage of the manganese is 1:1:1:1:1; the purity of the cobalt, the chromium, the iron, the nickel and the manganese is 99.9%;

(2) smelting: the above mixed metal powder is poured into the crucible melting furnace of the spray deposition equipment and melted at 1550 ° C to obtain molten metal;

(3) coating lubricant: coating water-agent colloidal graphite lubricant in the circular mold on the worktable in the deposition cavity, and feeding high-purity argon gas after drying to form a protective atmosphere; and the flow rate of the argon gas is 80sccm;

(4) Deposition: The above-mentioned molten metal is poured into the molten metal bag, and high-purity argon gas of 1.1 MPa is passed in, and the molten metal is atomized through a nozzle with a diameter of φ3.05 mm, and the molten metal is atomized and deposited on a circle. In the mold, a CoCrFeNiMn high-entropy alloy ingot with a size of φ50cm×80cm was obtained;

(5) Homogenization treatment: the obtained CoCrFeNiMn high-entropy alloy ingot is placed in a vacuum heating furnace at 950 ° C for heat treatment for 10 hours, and then placed in 15 ° C of water for cooling;

(6) Hot extrusion: preheat the CoCrFeNiMn high-entropy alloy ingot after homogenization treatment at 900 ° C for 8 hours, and then perform hot extrusion, the extrusion ratio is 15, and the extrusion speed is 2 mm/s; Obtain CoCrFeNiMn high-entropy alloy rods;

(7) Descale: remove the 1.2mm-thick scale on the surface of the CoCrFeNiMn high-entropy alloy bar by a numerically controlled lathe;

(8) Nitriding treatment: the CoCrFeNiMn high-entropy alloy bar after descaling was placed in a vacuum nitriding device, and a mixed gas of argon and nitrogen was introduced for nitriding treatment at 500° C. for 8 hours. A nitrided layer is formed on the surface of the CoCrFeNiMn high-entropy alloy bar to obtain a CoCrFeNiMn high-entropy alloy for extremely cold environments; the flow rate of argon gas introduced is 60sccm, and the flow ratio of argon gas to nitrogen gas is 1:0.4.

Test: The surface hardness of the CoCrFeNiMn high-entropy alloy for extremely cold environments obtained in the above-mentioned Example 2 was measured by a hardness tester to be 10.2GPa; the tensile strength measured by the tensile test in liquid nitrogen (-196°C) was 799MPa, and the elongation was 70%; It can be seen that the high-entropy alloy prepared by the present invention has better elongation at extremely low temperature, and has good low-temperature toughness on the surface.

Application: The CoCrFeNiMn high-entropy alloy prepared by the present invention has a high hardness surface and high low temperature toughness, and can be used as steel for mining and drilling equipment in polar regions.

Example 3

A preparation method of high-entropy alloy for extremely cold environment, comprising the following steps:

(1) Mixing powder: uniformly mix cobalt, chromium, iron, nickel, and manganese elemental powder according to the atomic percentage of the high-entropy alloy to obtain mixed metal powder; the cobalt, the chromium, the iron, the nickel and the atomic percentage of the manganese is 1:1:1:1:1; the purity of the cobalt, the chromium, the iron, the nickel and the manganese is 99.9%;

(2) Smelting: adding the mixed metal powder to the crucible melting furnace of the spray deposition equipment and melting at 1580 ° C to obtain molten metal;

(3) Apply lubricant: apply DFY-1 grease-based paint lubricant in the circular mold on the worktable in the deposition cavity, and after drying, pass high-purity argon gas to form a protective atmosphere; and the argon gas flow rate is 100sccm;

(4) Deposition: The above-mentioned molten metal is poured into the molten metal bag, and high-purity argon gas of 0.9 MPa is passed through. In the mold, a CoCrFeNiMn high-entropy alloy ingot with a size of φ50cm×80cm was obtained;

(5) Homogenization treatment: the obtained CoCrFeNiMn high-entropy alloy ingot is placed in a vacuum heating furnace at 900 ° C for heat treatment for 8 hours, and then placed in 10 ° C of water for cooling;

(6) Hot extrusion: Preheat the CoCrFeNiMn high-entropy alloy ingot after homogenization treatment at 850 ° C for 8 hours, and then perform hot extrusion, the extrusion ratio is 20, and the extrusion speed is 2 mm/s; Obtain CoCrFeNiMn high-entropy alloy rods;

(7) Descale: remove the 1.5mm thick scale on the surface of the CoCrFeNiMn high-entropy alloy bar by a numerically controlled lathe;

(8) Nitriding treatment: the CoCrFeNiMn high-entropy alloy bar after descaling was placed in a vacuum nitriding device, and a mixed gas of argon and nitrogen was introduced to carry out nitriding treatment at 1000° C. for 2 hours. A nitrided layer is formed on the surface of the CoCrFeNiMn high-entropy alloy bar to obtain a CoCrFeNiMn high-entropy alloy for extremely cold environments; and the flow rate of argon gas introduced is 80sccm, and the flow ratio of argon gas to nitrogen gas is 1:0.6.

Test: The surface hardness of the CoCrFeNiMn high-entropy alloy for extreme cold environment obtained in the above-mentioned Example 3 was measured by a hardness tester to be 11.98GPa; the tensile strength measured by the tensile test in liquid nitrogen (-196°C) was 801MPa, and the elongation was 68%; It can be seen that the high-entropy alloy prepared by the present invention has better elongation at extremely low temperature, and has good low-temperature toughness on the surface.

Application: The CoCrFeNiMn high-entropy alloy prepared by the present invention has a high hardness surface and high low temperature toughness, and can be used as steel for mining and drilling equipment in polar regions.

Example 4

A preparation method of high-entropy alloy for extremely cold environment, comprising the following steps:

(1) Mixing powder: uniformly mix cobalt, chromium, iron, nickel, and manganese elemental powder according to the atomic percentage of the high-entropy alloy to obtain mixed metal powder; the cobalt, the chromium, the iron, the nickel and the atomic percentage of the manganese is 1:1:1:1:1; the purity of the cobalt, the chromium, the iron, the nickel and the manganese is 99.9%;

(2) Smelting: the above-mentioned mixed metal powder is poured into the crucible melting furnace of the spray deposition equipment and melted at 1600 ° C to obtain molten metal;

(3) coating lubricant: coating spindle oil in the circular mold on the worktable in the deposition cavity, and feeding high-purity argon gas after drying to form a protective atmosphere; and the argon gas flow rate is 90sccm;

(4) Deposition: Add the above-mentioned molten metal into the molten metal bag and pass high-purity argon gas of 1.0 MPa, atomize the molten metal through a nozzle with a diameter of φ3.0 mm, and atomically deposit the molten metal on a circular A CoCrFeNiMn high-entropy alloy ingot with a size of φ50cm×80cm can be obtained in the mold;

(5) Homogenization treatment: the obtained CoCrFeNiMn high-entropy alloy ingot is placed in a vacuum heating furnace at 1100 ° C for heat treatment for 6 hours, and then placed in 5 ° C of water for cooling;

(6) Hot extrusion: preheat the CoCrFeNiMn high-entropy alloy ingot after homogenization treatment at 900 ° C for 8 hours, and then perform hot extrusion, the extrusion ratio is 10, and the extrusion speed is 3 mm/s; Obtain CoCrFeNiMn high-entropy alloy rods;

(7) Descale: remove the 1.3mm thick scale on the surface of the CoCrFeNiMn high-entropy alloy bar by a CNC lathe;

(8) Nitriding treatment: place the CoCrFeNiMn high-entropy alloy bar after descaling in a vacuum nitriding device, and introduce a mixed gas of argon and nitrogen for nitriding treatment at 800° C. for 5 hours. A nitrided layer is formed on the surface of the CoCrFeNiMn high-entropy alloy rod to obtain a CoCrFeNiMn high-entropy alloy for extremely cold environments; and the flow rate of argon gas introduced is 100sccm, and the flow ratio of argon gas to nitrogen gas is 1:0.8.

Test: The surface hardness of the CoCrFeNiMn high-entropy alloy for extreme cold environments obtained in Example 4 was measured by a hardness tester, and the surface hardness was 12.2GPa; the tensile strength measured by the tensile test in liquid nitrogen (-196°C) was 804MPa, and the elongation was 69%; It can be seen that the high-entropy alloy prepared by the present invention has better elongation at extremely low temperature, and has good low-temperature toughness on the surface.

Application: The CoCrFeNiMn high-entropy alloy prepared by the present invention has a high hardness surface and high low temperature toughness, and can be used as steel for mining and drilling equipment in polar regions.

Example 5

A preparation method of high-entropy alloy for extremely cold environment, comprising the following steps:

(1) Mixing powder: uniformly mix cobalt, chromium, iron, nickel, and manganese elemental powder according to the atomic percentage of the high-entropy alloy to obtain mixed metal powder; the cobalt, the chromium, the iron, the nickel and the atomic percentage of the manganese is 1:1:1:1:1; the purity of the cobalt, the chromium, the iron, the nickel and the manganese is 99.9%;

(2) smelting: the above mixed metal powder is poured into the crucible melting furnace of the spray deposition equipment and melted at 1500 ° C to obtain molten metal;

(3) Coating lubricant: coating water-agent colloidal graphite lubricant in the circular mold on the worktable in the deposition cavity, and feeding high-purity argon gas after drying to form a protective atmosphere; and the argon gas flow rate is 100sccm;

(4) Deposition: The above-mentioned molten metal is injected into the molten metal bag and the high-purity argon gas of 1.2MPa is passed in, the molten metal is atomized through a nozzle with a diameter of φ3.0mm, and the molten metal is atomized and deposited on the circular A CoCrFeNiMn high-entropy alloy ingot with a size of φ50cm×80cm can be obtained in the mold;

(5) homogenization treatment: the obtained CoCrFeNiMn high-entropy alloy ingot is placed in a vacuum heating furnace at 1050 ° C for heat treatment for 9 hours, and then placed in 20 ° C of water for cooling;

(6) Hot extrusion: Preheat the CoCrFeNiMn high-entropy alloy ingot after homogenization treatment at 800 ° C for 9 hours, and then perform hot extrusion, the extrusion ratio is 10, and the extrusion speed is 3 mm/s; Obtain CoCrFeNiMn high-entropy alloy rods;

(7) Descale: remove the 1.1mm thick oxide scale on the surface of the CoCrFeNiMn high-entropy alloy bar by a numerically controlled lathe;

(8) Nitriding treatment: the CoCrFeNiMn high-entropy alloy bar after descaling was placed in a vacuum nitriding device, and a mixed gas of argon and nitrogen was introduced for nitriding treatment at 700° C. for 8 hours. A nitrided layer is formed on the surface of the CoCrFeNiMn high-entropy alloy bar to obtain a CoCrFeNiMn high-entropy alloy for extremely cold environments; and the flow rate of argon gas introduced is 50 sccm, and the flow ratio of argon gas to nitrogen gas is 1:1.

Test: The surface hardness of the CoCrFeNiMn high-entropy alloy for extreme cold environment obtained in Example 5 was measured by a hardness tester, and the surface hardness was 12.1GPa; the tensile strength measured by the tensile test in liquid nitrogen (-196°C) was 805MPa, and the elongation was 70%; It can be seen that the high-entropy alloy prepared by the present invention has better elongation at extremely low temperature, and has good low-temperature toughness on the surface.

Application: The CoCrFeNiMn high-entropy alloy prepared by the present invention has a surface with high hardness and high low temperature toughness, and can be used as steel for mining and drilling equipment in polar regions.

It can be seen from the test results of the above examples 1-5 that the CoCrFeNiMn high-entropy alloy prepared by the preparation method of the present invention has excellent mechanical properties such as hardness, tensile strength and low temperature toughness, and can be used for mining in polar regions , Steel for drilling equipment. The above-mentioned preferred embodiments of the present invention are only used to explain the present invention, and are not intended to limit the present invention. Any obvious changes or changes derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims (8)

1. A preparation method of a high-entropy alloy for an extremely cold environment is characterized by comprising the following steps:

(1) powder preparation: mixing simple substance powder of cobalt, chromium, iron, nickel and manganese according to the atomic percentage of the high-entropy alloy to obtain mixed metal powder;

(2) smelting: melting the mixed metal powder to obtain molten metal;

(3) coating a lubricant: coating a lubricant in a mould in the deposition cavity, drying and introducing inert gas to form a protective atmosphere;

(4) deposition: injecting the molten metal into a molten metal bag, introducing inert gas, and performing atomization deposition on the molten metal in the mold to obtain a CoCrFeNiMn high-entropy alloy ingot;

(5) homogenizing: placing the CoCrFeNiMn high-entropy alloy ingot in a vacuum heating furnace for heat treatment, and then cooling by water;

(6) hot extrusion: carrying out hot extrusion on the homogenized CoCrFeNiMn high-entropy alloy ingot to obtain a CoCrFeNiMn high-entropy alloy bar;

(7) descaling: removing the oxide skin on the surface of the CoCrFeNiMn high-entropy alloy bar;

(8) nitriding treatment: placing the CoCrFeNiMn high-entropy alloy bar subjected to descaling in a vacuum nitriding device, introducing mixed gas of argon and nitrogen for high-temperature nitriding treatment, and forming a nitride layer on the surface of the CoCrFeNiMn high-entropy alloy bar to obtain a high-entropy alloy for an extremely cold environment;

the temperature of the nitriding treatment in the step (8) is 500-; the flow rate of the argon gas is 40-100sccm, and the flow rate ratio of the argon gas to the nitrogen gas is 1: (0.2-1); the thickness of the nitride layer is 2-3 mm;

the high-entropy alloy is used as a material for polar region mining and drilling equipment.

2. A method for preparing a high entropy alloy for extremely cold environments as claimed in claim 1, wherein the atomic percentages of the cobalt, the chromium, the iron, the nickel and the manganese in step (1) are 1: 1: 1: 1: 1; the purity of the cobalt, the chromium, the iron, the nickel and the manganese was 99.9%.

3. The preparation method of the high-entropy alloy for the extremely cold environment according to claim 1, wherein the step (2) is to smelt: and (3) adding the mixed metal powder into a crucible smelting furnace of the spray deposition equipment to be melted at 1500-1600 ℃ to obtain molten metal.

4. A method for preparing a high-entropy alloy for extremely cold environments as claimed in claim 1, wherein the lubricant in step (3) is aqueous colloidal graphite, DFY-1 type fat-based paint or spindle oil; the inert gas is argon, and the flow rate of the argon is 80-100 sccm.

5. A method for preparing a high-entropy alloy for extremely cold environments according to claim 1, wherein the deposition in the step (4): and (3) injecting the molten metal into a molten metal bag, introducing argon gas of 0.9-1.2MPa, atomizing the molten metal through a nozzle with the diameter of phi 3 +/-0.05 mm, and atomizing and depositing the molten metal in a circular mold to obtain the CoCrFeNiMn high-entropy alloy ingot with the size of phi 50cm multiplied by 80 cm.

6. A method for preparing a high-entropy alloy for an extremely cold environment according to claim 1, wherein the homogenization treatment in the step (5): placing the CoCrFeNiMn high-entropy alloy ingot in a vacuum heating furnace at the temperature of 900-1100 ℃ for heat treatment for 6-12 hours; the water cooling temperature is 0-20 ℃.

7. A method for preparing a high-entropy alloy for an extremely cold environment according to claim 1, wherein the step (6) of hot extrusion: preheating the homogenized CoCrFeNiMn high-entropy alloy ingot at the temperature of 800-900 ℃ for 8-10 hours, and then carrying out hot extrusion, wherein the extrusion ratio is 10-20, and the extrusion speed is 1-3 mm/s; obtaining the CoCrFeNiMn high-entropy alloy bar.

8. The method for preparing the high-entropy alloy for the extremely cold environment according to claim 1, wherein the descaling in the step (7): and removing 1-1.5mm of surface oxide skin of the CoCrFeNiMn high-entropy alloy bar by using a numerical control lathe.