Rapidly sintered rhenium plate and preparation method thereof

Abstract

The invention discloses a rapidly sintered rhenium plate and a preparation method thereof, and relates to the field of powder metallurgy. The preparation method comprises the following steps: putting a mold filled with rhenium powder into spark plasma sintering equipment, vacuumizing, introducing hydrogen-containing mixed gas, carrying out a gradient pressurization-pulse sintering process, heating the rhenium powder to a target temperature at a rate of 80-200 DEG C / min, carrying out heat preservation, synchronously applying axial pressure, controlling the pressure to be 8-12 Mpa when the temperature is less than 1000 DEG C, controlling the pressure to be greater than or equal to 15 Mpa when the temperature is greater than or equal to 1000 DEG C, and carrying out sintering for 2-3 hours; and cooling, demolding, reducing and annealing in a hydrogen atmosphere, and grinding to obtain the rhenium plate. Rapid sintering densification of pure rhenium is achieved through the spark plasma sintering technology, the temperature rising time is greatly shortened, step pressure rising is carried out before the nucleation stage of heating sintering, it is avoided that moving filling of rhenium powder is hindered by high pressure at the low temperature, size homogenization is promoted, and the prepared rhenium plate is good in uniformity and high in density and purity; and the oxygen content is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of powder metallurgy, in particular to a rapid sintering rhenium plate and a preparation method thereof. BACKGROUND

[0002] The melting point of metallic rhenium is as high as 3180℃. Due to its high melting point, good plasticity, high strength, high creep resistance, strong corrosion resistance and good thermal fatigue resistance, it is suitable for working in ultra-high temperature and strong thermal shock working mitigation, and has become an irreplaceable material in the fields of aerospace engine single crystal blades, nuclear reactor neutron reflector, medical gamma knife radiation source packaging and other cutting-edge fields.

[0003] Rhenium is the most work-hardened metal, which greatly limits its cold working capacity. At present, the process route of powder metallurgy and cold rolling is mostly used for preparing rhenium plate. The cold rolling process cannot well control the reduction of the edge of the plate, so that the edge change of the rolled piece is inconsistent with the middle change, leading to serious edge cracking of the plate. Meanwhile, high temperature annealing to eliminate work hardening will cause non-uniform growth of grains in the later recrystallization treatment stage, thereby seriously affecting the uniformity and final performance of the rhenium plate. The traditional powder metallurgy process has multiple stages of sintering and long process in the preparation process of rhenium products, resulting in long production cycle, and the forming rate of the plate blank is only about 70%, which is more demanding on the particle size distribution, morphology and bulk density of the raw material powder, and seriously restricts the industrialized preparation of pure rhenium special-shaped components. SUMMARY

[0004] The present application provides a rapid sintering rhenium plate and a preparation method thereof, which can reduce the particle size and morphology requirements of the raw material rhenium powder, and rapidly prepare a rhenium plate with high purity, high density and low oxygen content in a short process and short time.

[0005] In order to solve the above technical problems, one of the objects of the present application is to provide a preparation method of a rapid sintering rhenium plate, comprising the following steps:

[0006] (1) Fill the rhenium powder into the mold and put it into the discharge plasma sintering equipment, wash it with inert gas after vacuumizing, then pass in the mixed gas containing hydrogen and inert gas after vacuumizing again, and use the discharge plasma sintering system to implement gradient pressurization-pulse sintering process, rapidly heat the rhenium powder to the target temperature at a heating rate of 80-200℃ / min, and keep the temperature at the target temperature, the heating and keeping temperature process are synchronous, the axial pressure is 8-12Mpa when the temperature is <1000℃, and the axial pressure is ≥15Mpa when the temperature is ≥1000℃, and then rapidly cool to obtain a rhenium plate blank;

[0007] (2) After the rhenium plate blank is demolded, reduction annealing is carried out in a hydrogen atmosphere, and a rhenium plate is obtained after grinding.

[0008] The present application adopts the spark plasma sintering technology to realize the rapid sintering densification of pure rhenium, and can realize the preparation of high-density and complex-shaped sintered blanks according to the size of the mold. The spark plasma sintering technology (SPS) is to realize the synergistic effect of nanoscale spark plasma activation and joule heating effect by applying pulse direct current in the axial pressure field, to reach the sintering temperature in a short time, and to greatly shorten the heating time. The greater the pressure loaded during the heating and sintering process, the higher the density of the sintered rhenium plate, but too high pressure at the low temperature stage will hinder the movement of the powder, so the step-by-step pressure increase is carried out before the nucleation stage. The uniformity of the rhenium plate is good due to the uniform conduction of the upper and lower pressure during the sintering nucleation process, which makes the rhenium powder move and fill during the sintering process. At the same time, in the process of rapid densification sintering, a small amount of hydrogen is doped in the mixed gas, which can avoid the oxidation of rhenium powder during sintering and reduce the oxygen content of rhenium plate.

[0009] As a preferred solution, in step (1), the mixed gas includes hydrogen gas with a volume fraction of 1vt%-3vt% and the balance of inert gas. A small amount of hydrogen gas in the mixed gas can reduce the oxygen content of the prepared rhenium plate. Since the explosion limit of hydrogen in air is 4-75vt%, it is necessary to avoid the risk of explosion due to too high concentration of hydrogen.

[0010] As a preferred solution, in step (1), the volume fraction of hydrogen in the mixed gas is any one or any two of the range values of 1vt%, 1.5vt%, 2vt%, 2.5vt%, 3vt%.

[0011] As a preferred solution, in step (1), the inert gas is at least one of argon, nitrogen, helium, neon, krypton, xenon, and preferably argon.

[0012] As a preferred solution, in step (1), the target temperature is 1900-2200℃, and the holding time of the target temperature is 1-4h.

[0013] As a preferred solution, in step (1), the target temperature is any one or any two of the range values of 1900℃, 1950℃, 2000℃, 2050℃, 2100℃, 2150℃, 2200℃, and the holding time of the target temperature is any one or any two of the range values of 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h.

[0014] As a preferred solution, in step (1), the axial pressure is any one or any two of the range values of 8Mpa, 9Mpa, 10Mpa, 11Mpa, 12Mpa when the temperature is <1000℃.

[0015] As a preferred solution, in step (1), when the temperature is ≥ 1000℃, the axial pressure is set to any one or a range value of any two of 15Mpa, 16Mpa, 17Mpa, 18Mpa, 19Mpa, 20Mpa.

[0016] As a preferred solution, in step (1), the rhenium powder has a Fisher particle size of 3-40μm, and a purity satisfying a rhenium content > 99.99wt%.

[0017] As a preferred solution, in step (1), the mold is a graphite mold, and a 0.5-1mm carbon paper is laid in the inner surface of the mold.

[0018] As a preferred solution, in step (1), a 0.5-1mm carbon paper is laid on the inner bottom surface of the mold in advance, and after the rhenium powder is filled into the mold, a 0.5-1mm carbon paper is laid on the inner top surface of the mold, so as to facilitate subsequent demolding.

[0019] As a preferred solution, in step (2), the reduction annealing temperature is 1200-1500℃, the reduction annealing time is 1-2h, and the hydrogen flow rate is 2-10L / min.

[0020] As a preferred solution, in step (2), the rhenium slab is ground to a thickness of a target thickness size by using a diamond grinding wheel.

[0021] To solve the above technical problems, a second object of the present application is to provide a rapid sintering rhenium plate.

[0022] As a preferred solution, the rhenium plate has an oxygen content ≤ 0.02wt%, a purity ≥ 99.99wt%, and a density ≥ 20g / cm 3 .

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The present application uses a spark plasma sintering technology to realize rapid sintering densification of pure rhenium, reaches a sintering temperature in a short time, greatly shortens the heating time, and can realize the preparation of high-density and complex-shaped sintered slabs according to the size of the mold. The sintering nucleation process is carried out by stepwise pressure increase before the nucleation stage of heating and sintering. The uniformity of the prepared rhenium plate is good, the density and purity are high, and the rhenium powder moves and fills during the sintering process due to the uniform conduction of the upper and lower pressures.

[0025] 2. In the rapid densification sintering process of the present application, a small amount of hydrogen is doped in the mixed gas. The trace amount of hydrogen in the mixed gas can avoid the oxidation of the rhenium powder during the sintering process, reduce the oxygen content of the prepared rhenium plate, and at the same time control the hydrogen concentration below the explosion limit in the gas to avoid the risk of explosion due to high hydrogen concentration.

[0026] 3、The application adopts annealing in a hydrogen atmosphere in the reduction annealing stage, which can release the internal stress generated by rapid heating and cooling in the sintering process and the internal stress generated by pressure sintering, thereby improving the mechanical properties of the sintered rhenium plate.

[0027] 4、Compared with the traditional process, the application avoids the influence of rhenium powder pressing performance, improves the rhenium plate blank pressing forming rate, has low requirements for rhenium powder morphology, particle size and bulk density, shortens the sintering time, does not need to use cold isostatic pressing process, shortens the process flow and reduces the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 : is a flowchart of the preparation method of the rapid sintering rhenium plate in the embodiment of the application;

[0029] Figure 2 : is a metallographic microstructure diagram of the rapid sintering rhenium plate in embodiment 1 of the application;

[0030] Figure 3 : is a metallographic microstructure diagram of the rapid sintering rhenium plate in embodiment 2 of the application;

[0031] Figure 4 : is a metallographic microstructure diagram of the rapid sintering rhenium plate in comparative example 3 of the application. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0033] It should be understood that the terms described in the application are only for describing the specific embodiments, and are not used to limit the application. In addition, for the numerical range in the application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the range, and any other stated value or intermediate value in the range is also included in the application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0034] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0035] As used in this article:

[0036] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0037] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0038] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0039] "Parts by mass" is a basic unit of measurement that expresses the proportional relationship between the masses of multiple components. One part can represent any unit mass. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0040] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0041] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", etc., indicating orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0042] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are all commercially available, and the same raw materials were used in parallel experiments.

[0043] Example 1

[0044] A method for preparing rapidly sintered rhenium plates, such as... Figure 1 As shown, it includes the following steps:

[0045] (1) Select rhenium powder with a Fisher particle size of 15.2μm and a purity of 99.992%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0046] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, an argon-hydrogen mixture with a hydrogen volume content of 3% is introduced. Hydrogen gas can reduce the oxygen content in the rhenium plate. Under the protection of the mixed atmosphere, the gradient pressure-pulse sintering process is implemented using the spark plasma sintering system (SPS) to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain a dense rhenium plate blank.

[0047] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2200℃ at a heating rate of 180℃ / min, and held at the target temperature for 2 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 10 MPa, and when the temperature is ≥1000℃, the axial pressure is set to 18 MPa.

[0048] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1300℃ for 1 hour. The hydrogen flow rate is controlled at 2L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.5mm by a diamond grinding wheel to obtain the rhenium plate.

[0049] Example 2

[0050] A method for preparing rapidly sintered rhenium plates, such as... Figure 1 As shown, it includes the following steps:

[0051] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0052] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, an argon-hydrogen mixture with a hydrogen volume content of 3% is introduced. Hydrogen gas can reduce the oxygen content in the rhenium plate. Under the protection of the mixed atmosphere, the gradient pressure-pulse sintering process is implemented using the spark plasma sintering system (SPS) to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain a dense rhenium plate blank.

[0053] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2000℃ at a heating rate of 150℃ / min, and held at the target temperature for 3 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 10 MPa, and when the temperature is ≥1000℃, the axial pressure is set to 20 MPa.

[0054] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0055] Comparative Example 1

[0056] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0057] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0058] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, pure argon gas is introduced. Under the protection of an inert atmosphere, the spark plasma sintering system (SPS) is used to implement the gradient pressure-pulse sintering process to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain rhenium plate blanks.

[0059] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2000℃ at a heating rate of 150℃ / min, and held at the target temperature for 3 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 10 MPa, and when the temperature is ≥1000℃, the axial pressure is set to 20 MPa.

[0060] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0061] Comparative Example 2

[0062] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0063] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0064] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, an argon-hydrogen mixture with a hydrogen volume content of 3% is introduced. Hydrogen gas can reduce the oxygen content in the rhenium plate. Under the protection of the mixed atmosphere, the powder is pressurized and rapidly heated to sinter using a spark plasma sintering system (SPS). The temperature is rapidly raised to the target temperature of 2000℃ at a heating rate of 150℃ / min and held at the target temperature for 3 hours. An axial pressure of 20 MPa is applied simultaneously during the heating and holding process. Then, the plate blank is rapidly cooled to obtain the rhenium plate blank.

[0065] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0066] Comparative Example 3

[0067] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0068] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0069] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, pure argon gas is introduced. Under the protection of an inert atmosphere, the powder is sintered by pressurization and rapid heating using a spark plasma sintering system (SPS). The temperature is rapidly raised to the target temperature of 2000℃ at a heating rate of 150℃ / min and held at the target temperature for 3 hours. An axial pressure of 20 MPa is applied simultaneously during the heating and holding process. Then, it is rapidly cooled to obtain a rhenium plate blank.

[0070] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0071] Comparative Example 4

[0072] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0073] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0074] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, an argon-hydrogen mixture with a hydrogen volume content of 3% is introduced. Hydrogen gas can reduce the oxygen content in the rhenium plate. Under the protection of the mixed atmosphere, the gradient pressure-pulse sintering process is implemented using the spark plasma sintering system (SPS) to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain a dense rhenium plate blank.

[0075] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2000℃ at a heating rate of 150℃ / min, and held at the target temperature for 3 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 6 MPa, and when the temperature is ≥1000℃, the axial pressure is set to 18 MPa.

[0076] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0077] Comparative Example 5

[0078] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0079] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0080] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, an argon-hydrogen mixture with a hydrogen volume content of 3% is introduced. Hydrogen gas can reduce the oxygen content in the rhenium plate. Under the protection of the mixed atmosphere, the gradient pressure-pulse sintering process is implemented using the spark plasma sintering system (SPS) to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain a dense rhenium plate blank.

[0081] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2000℃ at a heating rate of 150℃ / min, and held at the target temperature for 3 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 15MPa, and when the temperature is ≥1000℃, the axial pressure is set to 20MPa.

[0082] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0083] Comparative Example 6

[0084] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0085] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0086] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, an argon-hydrogen mixture with a hydrogen volume content of 3% is introduced. Hydrogen gas can reduce the oxygen content in the rhenium plate. Under the protection of the mixed atmosphere, the gradient pressure-pulse sintering process is implemented using the spark plasma sintering system (SPS) to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain a dense rhenium plate blank.

[0087] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2000℃ at a heating rate of 150℃ / min, and held at the target temperature for 3 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 10 MPa, and when the temperature is ≥1000℃, the axial pressure is set to 12 MPa.

[0088] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0089] Comparative Example 7

[0090] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0091] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0092] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, an argon-hydrogen mixture with a hydrogen volume content of 3% is introduced. Hydrogen gas can reduce the oxygen content in the rhenium plate. Under the protection of the mixed atmosphere, the gradient pressure-pulse sintering process is implemented using the spark plasma sintering system (SPS) to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain a dense rhenium plate blank.

[0093] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2000℃ at a heating rate of 250℃ / min, and held at the target temperature for 3 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 10 MPa, and when the temperature is ≥1000℃, the axial pressure is set to 20 MPa.

[0094] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0095] Comparative Example 8

[0096] A method for preparing a rapid sintering rhenium plate includes the following steps:

[0097] (1) Select rhenium powder with a Fisher particle size of 23.7μm and a purity of 99.993%. Line the inner wall of the graphite mold with carbon paper with a thickness of 0.5mm. Fill the graphite mold cavity with three-dimensional vibration. After filling and leveling the powder, line the upper surface of the material with carbon paper with a thickness of 0.5mm for later demolding.

[0098] (2) The graphite mold containing rhenium powder is placed in the spark plasma sintering furnace. After evacuation, it is purged with argon gas. After evacuation again, pure hydrogen gas is introduced. The spark plasma sintering system (SPS) is used to implement the gradient pressure-pulse sintering process to pressurize and rapidly heat the powder for sintering. Then, it is rapidly cooled to obtain a dense rhenium plate blank.

[0099] The gradient pressure-pulse sintering process is as follows: the temperature is rapidly increased to the target temperature of 2000℃ at a heating rate of 150℃ / min, and held at the target temperature for 3 hours. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 10 MPa, and when the temperature is ≥1000℃, the axial pressure is set to 20 MPa.

[0100] (3) After the rhenium plate blank is demolded, the carbon paper on the surface of the rhenium plate blank is briefly removed with a tool. Then, the rhenium plate blank is subjected to reduction annealing in a hydrogen atmosphere at 1400℃ for 1 hour. The hydrogen flow rate is controlled at 3L / min to eliminate internal stress and reduce surface oxides. The annealed rhenium plate blank is ground to a thickness of 2.6mm by a diamond grinding wheel to obtain the rhenium plate.

[0101] Performance testing

[0102] 1. The rhenium plates prepared in the examples and comparative examples were observed under a metallographic microscope to check for uniformity of microstructure. The metallographic microstructure results obtained from Examples 1-2 and Comparative Example 3 are as follows: Figures 2-4 As shown.

[0103] 2. The rhenium plates prepared in the examples and comparative examples were tested for purity using a glow discharge mass spectrometer (calculated by difference method, excluding gaseous elements). The test results are shown in Table 1 below.

[0104] 3. The rhenium plates prepared in the examples and comparative examples were subjected to density tests using Archimedes' displacement method and an analytical balance. The test results are shown in Table 1 below.

[0105] 4. The oxygen content of the rhenium plates prepared in the examples and comparative examples was tested using an oxygen and nitrogen analyzer. The test results are shown in Table 1 below.

[0106] Table 1 - Performance test results of rhenium plates prepared in the embodiments and comparative examples of this application

[0107]

[0108]

[0109] As shown in Table 1 and Figures 1-2 As shown in Examples 1-2 of this application, the powder is subjected to gradient pressure-pulse sintering process in an argon-hydrogen mixed atmosphere using a spark plasma sintering system. In order to avoid excessive pressure hindering the movement of powder in the low-temperature stage, the axial pressure is stepped up before the nucleation stage, so as to achieve rapid pressure sintering into a dense sintered rhenium plate blank in a short time. Then, reduction annealing is carried out in a hydrogen atmosphere to eliminate internal stress and reduce surface oxides. The prepared rhenium plate has a uniform internal microstructure, no pores on the surface and inside, high density, low oxygen content, and good uniformity.

[0110] As shown in Table 1 and Figure 3 As shown, compared to Example 2, the powders in Comparative Examples 1 and 3 were subjected to pressurized rapid heating sintering in a pure argon inert gas atmosphere. Because no hydrogen was introduced during the sintering process, the oxygen content of the prepared rhenium plates increased, even exceeding the oxygen content requirement of less than 0.03 wt% specified in the non-ferrous metal industry standard YS / T 1018-2015 "Rhenium Particles," thus failing to meet application requirements. In Comparative Examples 2 and 3, the axial pressure was not increased in stages before the nucleation stage during pressurized rapid heating sintering; instead, it was directly pressurized to 20 MPa. The excessive axial pressure at lower temperatures caused the powder to move easily, resulting in protrusions on the surface of the prepared rhenium plates, uneven internal structure, and reduced density and purity.

[0111] As shown in Table 1, in Example 2, the axial pressure was 10 MPa when the temperature was <1000℃ and 20 MPa when the temperature was ≥1000℃ during the sintering process. In contrast, in Comparative Example 4, the axial pressure was 6 MPa when the temperature was <1000℃ and 18 MPa when the temperature was ≥1000℃ during the sintering process. The axial pressure was too low in the low-temperature stage, making it difficult for the powder to move and nucleate, resulting in a significant decrease in the purity of the final sintered rhenium plate. In contrast, in Comparative Example 5, the axial pressure was 15 MPa when the temperature was <1000℃ during the sintering process. The axial pressure was too high in the low-temperature nucleation stage, causing the powder to move easily, resulting in an uneven internal structure and a significant decrease in density in the prepared rhenium plate. Compared to Example 2, Comparative Example 6 sets the axial pressure to 12 MPa when the temperature is ≥1000℃ during the heating sintering process. The axial pressure of the high-temperature sintering is too low, resulting in insufficient power for pore shrinkage and powder movement. During the nucleation and recrystallization processes, the gas is trapped in the middle of the crystal or at the grain boundaries, resulting in the rhenium plate having too low density.

[0112] As shown in Table 1, the heating rate of rhenium powder in Example 2 during the sintering process was 150°C / min, while the heating rate of rhenium powder in Comparative Example 7 was 250°C / min. The heating rate was too fast. Since the sintering densification process requires the movement and shrinkage of the powder, the removal of low-melting-point impurities and the elimination of gases also require time. If the heating is too fast, the movement and shrinkage will be incomplete, and the removal of impurities and gases will be incomplete.

[0113] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for preparing a rapidly sintered rhenium plate, characterized in that, Includes the following steps: (1) Rhenium powder is filled into a mold and placed in a spark plasma sintering equipment. After vacuuming, it is purged with inert gas. After vacuuming again, a mixed gas containing hydrogen and inert gas is introduced. The spark plasma sintering system is used to implement a gradient pressure-pulse sintering process. The rhenium powder is rapidly heated to the target temperature at a heating rate of 80-200℃ / min and held at the target temperature. Axial pressure is applied simultaneously during the heating and holding process. When the temperature is <1000℃, the axial pressure is 8-12 MPa. When the temperature is ≥1000℃, the axial pressure is set to ≥15 MPa. After the holding is completed, the rhenium plate blank is rapidly cooled to obtain the rhenium plate blank. (2) After the rhenium plate blank is demolded, it is subjected to reduction annealing in a hydrogen atmosphere and then ground to obtain rhenium plate.

2. The method for preparing a rapid sintering rhenium plate as described in claim 1, characterized in that, In step (1), the mixed gas comprises hydrogen with a volume fraction of 1vt%-3vt% and the balance being an inert gas.

3. The method for preparing a rapid sintering rhenium plate as described in claim 1, characterized in that, In step (1), the inert gas is at least one of argon, nitrogen, helium, neon, krypton, and xenon.

4. The method for preparing a rapid sintering rhenium plate as described in claim 1, characterized in that, In step (1), the target temperature is 1900-2200℃, and the holding time at the target temperature is 1-4h; And / or, when the temperature is ≥1000℃, the axial pressure is set to 15-20 MPa.

5. The method for preparing a rapid sintering rhenium plate as described in claim 1, characterized in that, In step (1), the rhenium powder has a Fisher particle size of 3-40 μm and a purity that meets the requirement of rhenium content > 99.99 wt%.

6. The method for preparing a rapid sintering rhenium plate as described in claim 1, characterized in that, In step (1), the mold is a graphite mold, and the inner surface of the mold is covered with 0.5-1mm of carbon paper.

7. The method for preparing a rapid sintering rhenium plate as described in claim 1, characterized in that, In step (2), the reduction annealing temperature is 1200-1500℃, the reduction annealing time is 1-2h, and the hydrogen flow rate is 2-10L / min.

8. The method for preparing a rapid sintering rhenium plate as described in claim 1, characterized in that, In step (2), the rhenium plate blank is ground with a diamond grinding wheel to the target thickness.

9. A rapidly sintered rhenium plate prepared by the method for preparing a rapidly sintered rhenium plate as described in any one of claims 1-8.

10. The rapid sintering rhenium plate as described in claim 9, characterized in that, The rhenium plate has an oxygen content ≤0.02wt%, a purity ≥99.99wt%, and a density ≥20g / cm³. 3 .

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