CN107309434B - Preparation method and application of high-purity compact spherical molybdenum powder - Google Patents
Preparation method and application of high-purity compact spherical molybdenum powder Download PDFInfo
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- CN107309434B CN107309434B CN201710417547.5A CN201710417547A CN107309434B CN 107309434 B CN107309434 B CN 107309434B CN 201710417547 A CN201710417547 A CN 201710417547A CN 107309434 B CN107309434 B CN 107309434B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/06—Metallic powder characterised by the shape of the particles
- B22F1/065—Spherical particles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/06—Metallic material
- C23C4/08—Metallic material containing only metal elements
Abstract
The invention provides a preparation method and application of high-purity compact spherical molybdenum powder, and belongs to the technical field of preparation of spherical metal powder materials. The method takes the conventional reduced molybdenum powder as a raw material, actively controls the particle size range of the granulated molybdenum powder by adjusting the granulation process, further screens the molybdenum powder obtained after degumming, impurity removal and sintering, effectively controls the particle size of the granulated molybdenum powder before plasma spheroidization, and is favorable for controlling the particle size of the finally spheroidized molybdenum powder. The molybdenum powder after granulation and screening has narrow particle size distribution, and can effectively reduce vaporization and burning loss in the plasma spheroidization process of the molybdenum powder by matching with spheroidization process parameters such as input power, powder feeding rate, gas flow and the like, thereby being beneficial to the stability of the production process and greatly improving the production efficiency and the product quality; by introducing hydrogen into the degumming, impurity removal and sintering process of the molybdenum powder, the impurity content of the molybdenum powder before spheroidization is effectively reduced; meanwhile, the molybdenum powder is sieved, spheroidized, cooled and collected under the protection of argon, so that the oxygen content of the product is effectively reduced.
Description
Technical Field
The invention relates to a method for preparing high-purity compact spherical molybdenum powder with controllable particle size for 3D printing by taking reduced molybdenum powder as a raw material, and belongs to the technical field of preparation of spherical metal powder materials.
Background
Molybdenum is an important refractory rare metal, and is widely applied to the technical fields of modern industries such as aerospace, atomic energy, national defense, petrochemical industry, mechanical manufacturing, electronics, electricity, metallurgy, iron and steel and the like due to excellent mechanical property, conductivity, high temperature strength, corrosion resistance and oxidation resistance of molybdenum. With the rapid development of modern science and technology, particularly high-end technologies such as electronic information, aerospace and the like, the demand for high-performance and high-precision molybdenum products with complex shapes and uniform tissues is increased sharply. Due to the advantages of rapidness, flexibility, material saving and personalized customization, the additive manufacturing technology represented by the 3D printing technology has obvious advantages in the aspect of processing and forming of parts with high melting points, high performance and complex geometric shapes of traditional difficult-to-process materials such as tungsten, molybdenum, tantalum, niobium and the like, and is an important development direction of advanced manufacturing technology.
Molybdenum powder is a material basis for the development of a 3D printing technology of molybdenum parts, and the composition, morphology, particle size and distribution of the molybdenum powder directly influence the quality and performance of the 3D printing molybdenum parts. The molybdenum powder for 3D printing needs to have the characteristics of good sphericity, high density, low oxygen content and the like, and also needs to have uniform and controllable particle size, and can be industrially produced in batches at low cost.
At present, no mature preparation technology is available at home and abroad, and the method is suitable for producing the high-purity compact spherical molybdenum powder with controllable particle size for 3D printing. The molybdenum powder prepared by adopting the conventional reduction process has the advantages of mature process and lower cost, but the prepared molybdenum powder has irregular appearance, low density, serious powder agglomeration phenomenon and poor fluidity; the molybdenum powder prepared by means of atomization method or rotary electrode method is limited by the method, so that the defects of high impurity content, large particle size and difficulty in control of distribution generally exist, and meanwhile, the production cost is high and the process difficulty is high. Therefore, the molybdenum powder obtained by the existing production process is difficult to meet the requirement of the 3D printing technology on high-performance molybdenum powder, so that the preparation of the high-performance molybdenum powder for 3D printing, which has the advantages of uniform and controllable particle size distribution, low oxygen content, high density and good fluidity, becomes a difficult problem to be solved urgently in technical development.
Disclosure of Invention
The invention aims to provide a preparation method of high-purity compact spherical molybdenum powder aiming at the problems of poor fluidity, low density, high oxygen content, difficult control of powder particle size and the like of the molybdenum powder prepared by the existing production process. The method takes reduced molybdenum powder as a raw material to prepare high-purity compact spherical molybdenum powder with controllable particle size, and the molybdenum powder prepared by the method can meet the urgent need of the 3D printing field for high-performance molybdenum powder.
To achieve the above object, the solution of the present invention is as follows:
a preparation method of high-purity compact spherical molybdenum powder comprises the following steps:
step 1: mixing reduced molybdenum powder, a binder and deionized water to prepare slurry;
step 2: carrying out spray granulation on the slurry, and drying to obtain molybdenum powder aggregates;
and step 3: degumming, impurity removing and sintering the molybdenum powder aggregate to obtain granulated molybdenum powder;
and 4, step 4: sieving the granulated molybdenum powder to obtain the granulated molybdenum powder with the required particle size range;
and 5: sending the granulated molybdenum powder with the required particle size range to the core area of the plasma torch to obtain molten molybdenum powder;
step 6: and cooling and solidifying the molten molybdenum powder to obtain the high-purity compact spherical molybdenum powder.
In an alternative embodiment, the reduced molybdenum powder in the step 1 has a fisher particle size range of 0.5 μm to 6 μm, and a purity of more than 99.9% by mass fraction; the binder is polyvinyl alcohol; the content of the binder is 1-10% of the total mass of the binder and the deionized water; the mass percentage of the solid phase in the slurry is 30-70%.
In an alternative embodiment, the slurry is spray granulated in step 2 by a centrifugal spray dryer; the air inlet temperature of the spray drying of the centrifugal spray dryer is 150-250 ℃, and the air outlet temperature is 110-190 ℃; the radius of the centrifugal disc is 0.1m-0.3m, and the rotating speed range is 10000r/min-15000 r/min; the atomization pressure range is 0.2MPa-0.8 MPa.
In an optional embodiment, the degumming and impurity removal of the molybdenum powder aggregate in the step 3 are carried out in a hydrogen reducing atmosphere, hydrogen is not recycled, the degumming and impurity removal temperature is 700-1100 ℃, and the degumming and impurity removal time is 1-5 h; and 3, sintering the molybdenum powder aggregate in the hydrogen atmosphere at the sintering temperature of 1100-1500 ℃ for 1-3 h.
In an alternative embodiment, the sieving operation of the granulated molybdenum powder in the step 4 is performed under an argon atmosphere, and the granularity interval of the granulated molybdenum powder obtained by sieving is not more than 10 μm.
In an alternative embodiment, the power of the plasma torch in the step 5 is 30kW-100kW, the working gas is argon, the flow rate is 10slpm-50slpm, the side gas is argon, the flow rate is 30slpm-150slpm, and the system pressure of the plasma torch operation is 40kPa-98 kPa.
In an alternative embodiment, in step 5, the granulated molybdenum powder with the required particle size range is fed into the core region of the plasma torch by using a carrier gas, wherein the carrier gas is argon, the flow rate is 1slpm-10slpm, and the powder feeding rate of the granulated molybdenum powder is 40g/min-200 g/min.
In an alternative embodiment, the molten molybdenum powder in the step 6 is cooled and solidified in an argon atmosphere at a temperature not exceeding 30 ℃, and the cooling speed is not less than 1 x 104K/s。
In an alternative embodiment, the high-purity dense spherical molybdenum powder formed in the step 6 has a particle size range of 10 μm to 50 μm, a particle size interval of less than 10 μm, a spheroidization rate of more than 90%, and a molybdenum powder purity of more than 99.99% by mass fraction.
The high-purity compact spherical molybdenum powder prepared by the method is applied to the fields of 3D printing, powder metallurgy and thermal spraying. The invention has the advantages that:
(1) the conventional reduced molybdenum powder is used as a raw material, so that the purity of the raw material is high, the cost is low, the particle size distribution of the raw material molybdenum powder is wide, and the selection range of the raw material is expanded;
(2) the particle size range of molybdenum powder aggregates is actively controlled by adjusting a granulation process, and the granulated molybdenum powder obtained after degumming, impurity removal and sintering is further screened, so that the particle size of the molybdenum powder before plasma spheroidization can be effectively controlled, and the particle size control of the finally spheroidized molybdenum powder is facilitated;
(3) the molybdenum powder after granulation and screening has narrow particle size distribution, and can effectively reduce the vaporization and burning loss of the molybdenum powder in the plasma spheroidization process by matching with spheroidization process parameters such as adjustable input power, powder feeding speed, gas flow and the like, thereby being beneficial to the stability of the production process and greatly improving the production efficiency and the product quality;
(4) hydrogen is introduced into the degumming, impurity removal and sintering process of the molybdenum powder, so that the impurity content of the molybdenum powder before spheroidization is effectively reduced, and meanwhile, the sieving, spheroidization, cooling and collection of the molybdenum powder are operated under the argon protective atmosphere, so that the oxygen content of the product is effectively reduced.
(5) The spherical molybdenum powder obtained by the preparation method has the advantages of fine particle size, uniform and controllable distribution, low oxygen content of impurities, high density and good fluidity, greatly increases the additional value of the molybdenum powder, and meets the requirement of the 3D printing industry on high-performance molybdenum powder.
Drawings
Fig. 1 is a process flow diagram of a method for preparing high-purity dense spherical molybdenum powder for 3D printing according to an embodiment of the present invention;
fig. 2 is a scanning electron microscope photograph of the high-purity dense spherical molybdenum powder for 3D printing provided in embodiment 1 of the present invention;
fig. 3 is a scanning electron microscope photograph of the high-purity dense spherical molybdenum powder for 3D printing provided in embodiment 2 of the present invention;
fig. 4 is a scanning electron microscope photograph of the high-purity dense spherical molybdenum powder for 3D printing provided in example 3 of the present invention.
Detailed Description
The present invention is further illustrated by the following specific examples. It will be understood by those skilled in the art that the present invention is not limited thereto and that any modifications and variations made based on the present invention are within the scope of the present invention.
The embodiment of the invention provides a preparation method of high-purity compact spherical molybdenum powder, which comprises the following steps:
specifically, the reduced molybdenum powder in the embodiment of the invention is prepared by a conventional reduction process, the preferred Fisher size range of the reduced molybdenum powder is 0.5-6 μm, and the purity is more than 99.9% in mass percentage; the binder can be polymer-based or paraffin-based binders such as polyvinyl alcohol, polyethylene glycol, stearic acid, paraffin, and the like, and is preferably polyvinyl alcohol (PVA);
in the embodiment of the invention, firstly, uniformly mixing a binder and deionized water to prepare a solution A, then adding reduced molybdenum powder into the solution A, and mechanically stirring until the mixture is uniformly mixed to prepare slurry; wherein, the content of the binder in the solution A is 1 to 10 percent of the total mass of the solution A; the mass percentage of the solid phase in the slurry is 30-70%.
specifically, in the embodiment of the invention, the slurry is subjected to spray granulation by a centrifugal spray dryer, wherein the spray drying air inlet temperature of the centrifugal spray dryer is 150-250 ℃, and the air outlet temperature of the centrifugal spray dryer is 110-190 ℃; the radius of the centrifugal disc is 0.1m-0.3m, preferably 0.15m, and the rotating speed range is 10000r/min-15000 r/min; the atomization pressure range is 0.2MPa-0.8 MPa; the grain diameter of the obtained molybdenum powder aggregate ranges from 10 mu m to 50 mu m.
Step 3, carrying out degumming, impurity removal and sintering treatment on the molybdenum powder aggregate to obtain granulated molybdenum powder;
specifically, in the embodiment of the present invention, step 3 includes:
step 3 a: degumming and impurity removing treatment are carried out on the molybdenum powder aggregate in a muffle furnace, wherein the atmosphere is a hydrogen reducing atmosphere, and hydrogen is not recycled so as to facilitate the discharge of impurities; the degumming and impurity removal temperature is 700-1100 ℃, and the degumming and impurity removal time is 1-5 h; the purity of the molybdenum powder in the molybdenum powder aggregate after degumming and impurity removal is more than 99.99 percent (mass fraction);
and step 3 b: sintering the degummed molybdenum powder aggregate in a muffle furnace in a hydrogen atmosphere; the sintering temperature is 1100-1500 ℃; the sintering time is 1-3 h; the purity of the obtained granulated molybdenum powder after sintering is more than 99.99 percent (mass fraction).
Step 4, screening the granulated molybdenum powder to obtain granulated molybdenum powder with a required particle size range;
in the embodiment of the invention, the granulated molybdenum powder is screened in a glove box and in an argon environment, the particle size of the granulated molybdenum powder obtained by screening can be controlled according to requirements, and the particle size interval is only required to be not more than 10 mu m, so that the preparation method disclosed by the invention is not influenced.
Step 5, sending the granulated molybdenum powder with the required particle size range to a plasma torch core area to obtain molten molybdenum powder;
specifically, in the embodiment of the present invention, step 5 includes:
step 5 a: establishing a stable plasma torch with high energy density;
and step 5 b: utilizing carrier gas to send the granulated molybdenum powder with the screened required particle size range into the high-temperature area of the plasma torch core through a powder sending probe to obtain molten molybdenum powder;
in the embodiment of the invention, the optimal power of the plasma torch is 30kW-100kW, the working gas is high-purity argon, the flow rate is 10slpm-50slpm, the side gas is high-purity argon, the flow rate is 30slpm-150slpm, and the system pressure for the operation of the plasma torch is 40kPa-98 kPa; the carrier gas is high-purity argon, the flow rate is 1slpm-10slpm, and the powder feeding rate of the molybdenum powder is 40g/min-200 g/min.
And 6, cooling and solidifying the molten molybdenum powder to obtain the high-purity compact spherical molybdenum powder.
In the embodiment of the invention, after the screened granulated molybdenum powder is rapidly subjected to heat absorption and melting at the plasma torch core, the granulated molybdenum powder is spheroidized and densified under the action of surface tension, is separated from the plasma torch, freely falls into a heat exchange chamber, and is cooled and solidified under a very high temperature gradient to form high-purity dense spherical molybdenum powder; and opening the collector to collect the high-purity compact spherical molybdenum powder.
Specifically, in the embodiment of the invention, the atmosphere in the heat exchange chamber is a high-purity argon environment, the ambient temperature in the heat exchange chamber is not more than 30 ℃, and the cooling speed of the molybdenum powder is not less than 1 x 104K/s; the temperature of the spherical molybdenum powder after being cooled in the heat exchange chamber is not more than 30 ℃, and the powder collection operation is carried out in a glove box and under the environment of high-purity argon; the collected molybdenum powder has the particle size range of 10-50 mu m, the particle size interval of the molybdenum powder is less than 10 mu m, the spheroidization rate is more than 90 percent, and the purity of the molybdenum powder is more than 99.9 percent in percentage by mass.
The preparation method of the high-purity compact spherical molybdenum powder provided by the embodiment of the invention has the following beneficial effects:
(1) the conventional reduced molybdenum powder is used as a raw material, so that the purity of the raw material is high, the cost is low, the particle size distribution of the raw material molybdenum powder is wide, and the selection range of the raw material is expanded;
(2) the particle size range of molybdenum powder aggregates is actively controlled by adjusting a granulation process, and the granulated molybdenum powder obtained after degumming, impurity removal and sintering is further screened, so that the particle size of the molybdenum powder before plasma spheroidization can be effectively controlled, and the particle size control of the finally spheroidized molybdenum powder is facilitated;
(3) the molybdenum powder after granulation and screening has narrow particle size distribution, and can effectively reduce the vaporization and burning loss of the molybdenum powder in the plasma spheroidization process by matching with spheroidization process parameters such as adjustable input power, powder feeding speed, gas flow and the like, thereby being beneficial to the stability of the production process and greatly improving the production efficiency and the product quality;
(4) hydrogen is introduced into the degumming, impurity removal and sintering process of the molybdenum powder, so that the impurity content of the molybdenum powder before spheroidization is effectively reduced, and meanwhile, the sieving, spheroidization, cooling and collection of the molybdenum powder are operated under the argon protective atmosphere, so that the oxygen content of the product is effectively reduced.
(5) The spherical molybdenum powder obtained by the method has the advantages of fine particle size, uniform and controllable distribution, low oxygen content of impurities, high density and good fluidity, greatly increases the additional value of the molybdenum powder, and meets the requirement of the 3D printing industry on high-performance molybdenum powder.
The high-purity compact spherical molybdenum powder prepared by the preparation method of the high-purity compact spherical molybdenum powder provided by the embodiment of the invention can meet the requirement of the 3D field on high-performance molybdenum powder, can be applied to the 3D printing field, and can also be applied to the fields of novel powder metallurgy technologies such as powder injection molding, micro injection molding and gel casting molding, thermal spraying technology and the like.
The following are several specific embodiments of the invention:
example 1
The preparation method of the high-purity compact spherical molybdenum powder for 3D printing with the particle size range of 10-20 microns comprises the following steps:
And 2, carrying out spray granulation on the slurry B on a centrifugal spray dryer, wherein the air inlet temperature of the spray dryer is 170 ℃, the air outlet temperature of the spray dryer is 130 ℃, the radius of an atomizing disc is 0.15m, the rotating speed is 15000r/min, and the atomizing pressure is 0.75MPa, so that the particle size range of the molybdenum powder aggregate is 5-30 microns.
Step 3, carrying out degumming and impurity removal treatment on the molybdenum powder aggregate obtained by spray granulation by using a muffle furnace, wherein the degumming and impurity removal atmosphere is a hydrogen atmosphere, and hydrogen is not recycled so as to facilitate the discharge of impurities; degumming and impurity removing temperature is 750 ℃, degumming and impurity removing time is 1.5h, and loose granulation molybdenum powder with purity of more than 99.99 percent by mass is obtained.
And 4, sintering the degummed and impurity-removed loose granulated molybdenum powder by using a muffle furnace, wherein the sintering atmosphere is hydrogen, the sintering temperature is 1200 ℃, and the sintering time is 1.5h, so that the compact granulated molybdenum powder with the purity of more than 99.99 percent in percentage by mass is obtained.
And 5, vibrating and screening the sintered granulated molybdenum powder in a glove box and in an argon environment, and controlling the aperture interval of a screen mesh to obtain the denser granulated molybdenum powder with the particle size range of 10-20 microns.
And 6, establishing a high-frequency induction plasma torch with high energy density and stability by taking argon as working gas. The power of the plasma torch is 40kW, the working gas is high-purity argon, and the flow rate is 15 slpm; the side gas is high-purity argon with the flow rate of 40 slpm; the system pressure at which the torch was operated was 50 kPa.
Step 7, using argon gas as carrier gas, and sending the granulated molybdenum powder into a high-temperature area at the core part of the plasma torch through a powder feeding probe, wherein the flow rate of the carrier gas is 2 slpm; the powder feeding speed of the molybdenum powder is 50 g/min; the granulated molybdenum powder is melted in a plasma torch and is spheroidized and densified under the action of surface tension.
Step 8, separating the molten molybdenum powder from the plasma torch, and allowing the molten molybdenum powder to freely fall into a heat exchange chamber under the action of gravity; the heat exchange chamber is in a high-purity argon environment, and the ambient temperature is 28 ℃; the molybdenum powder is molten and dropped at 1 x 104K/s-1.5×104Cooling and solidifying under the temperature gradient of K/s to form compact spherical molybdenum powder.
Step 9, fully cooling the dense spherical molybdenum powder in a heat exchanger to 28 ℃, opening a collector in a glove box and in a high-purity argon environment, and collecting the molybdenum powder; the collected scanning electron microscope photo of the molybdenum powder is shown in figure 2, the molybdenum powder has a smooth surface, the density is more than 99%, the particle size of the molybdenum powder is 10-20 μm, the spheroidization rate is 93%, and the purity of the molybdenum powder is more than 99.99% in percentage by mass.
Example 2
The preparation method of the high-purity compact spherical molybdenum powder for 3D printing with the particle size of 20-30 mu m comprises the following steps:
And 2, carrying out spray granulation on the slurry B on a centrifugal spray dryer, wherein the air inlet temperature of the spray dryer is 200 ℃, the air outlet temperature of the spray dryer is 150 ℃, the radius of an atomizing disc is 0.15m, the rotating speed is 12000r/min, and the atomizing pressure is 0.5MPa, so that the particle size range of the molybdenum powder aggregate is 15-40 microns.
Step 3, carrying out degumming and impurity removal treatment on the molybdenum powder aggregate obtained by spray granulation by using a muffle furnace, wherein the degumming and impurity removal atmosphere is a hydrogen atmosphere, and hydrogen is not recycled so as to facilitate the discharge of impurities; degumming and impurity removing temperature is 900 ℃, degumming and impurity removing time is 2h, and loose granulation molybdenum powder with purity of more than 99.99 percent by mass is obtained.
And 4, sintering the degummed and impurity-removed loose granulated molybdenum powder by using a muffle furnace, wherein the sintering atmosphere is hydrogen, the sintering temperature is 1300 ℃, and the sintering time is 2 hours, so that the compact granulated molybdenum powder with the purity of more than 99.99 percent in percentage by mass is obtained.
And 5, vibrating and screening the sintered granulated molybdenum powder in a glove box and in an argon environment, and controlling the aperture interval of a screen mesh to obtain the denser granulated molybdenum powder with the particle size range of 20-30 microns.
And 6, establishing a high-frequency induction plasma torch with high energy density and stability by taking argon as working gas. The power of the plasma torch is 60kW, the working gas is high-purity argon, and the flow rate is 25 slpm; the side gas is high-purity argon, and the flow rate is 70 slpm; the system pressure at which the torch was operated was 70 kPa.
Step 7, using argon gas as carrier gas, and sending the granulated molybdenum powder into a high-temperature area at the core part of the plasma torch through a powder feeding probe, wherein the flow rate of the carrier gas is 5 slpm; the powder feeding rate of the molybdenum powder is 100 g/min; the granulated molybdenum powder is melted in a plasma torch and is spheroidized and densified under the action of surface tension.
Step 8, separating the molten molybdenum powder from the plasma torch, and allowing the molten molybdenum powder to freely fall into a heat exchange chamber under the action of gravity; the heat exchange chamber is in a high-purity argon environment, and the ambient temperature is 28 ℃; the molybdenum powder is molten and dropped at 1.2 multiplied by 104K/s-1.5×104Cooling and solidifying under the temperature gradient of K/s to form compact spherical molybdenum powder.
Step 9, fully cooling the dense spherical molybdenum powder in a heat exchanger to 28 ℃, and opening a collector in a glove box and in a high-purity argon environment to collect the molybdenum powder; the collected scanning electron microscope photo of the molybdenum powder is shown in fig. 3, the molybdenum powder has a smooth surface, the density is more than 99%, the particle size of the molybdenum powder is 20-30 μm, the spheroidization rate is 89%, and the purity of the molybdenum powder is more than 99.99% in percentage by mass.
Example 3
The preparation method of the high-purity compact spherical molybdenum powder for 3D printing with the particle size range of 30-40 mu m comprises the following steps:
And 2, performing spray granulation on the slurry B on a centrifugal spray dryer, wherein the air inlet temperature of spray drying is 240 ℃, the air outlet temperature is 180 ℃, the radius of an atomizing disc is 0.15m, the rotating speed is 11000r/min, and the atomizing pressure is 0.3MPa, so that the particle size range of the molybdenum powder aggregate is 25-50 microns.
Step 3, carrying out degumming and impurity removal treatment on the molybdenum powder aggregate obtained by spray granulation by using a muffle furnace, wherein the degumming and impurity removal atmosphere is a hydrogen atmosphere, and hydrogen is not recycled so as to facilitate the discharge of impurities; degumming and impurity removing temperature is 1000 ℃, degumming and impurity removing time is 2.5h, and loose granulation molybdenum powder with purity of more than 99.99 percent by mass is obtained.
And 4, sintering the degummed and impurity-removed loose and granulated molybdenum powder by using a muffle furnace, wherein the sintering atmosphere is hydrogen, the sintering temperature is 1400 ℃, and the sintering time is 2.5 hours, so that the compact granulated molybdenum powder with the purity of more than 99.99 percent in percentage by mass is obtained.
And 5, vibrating and screening the sintered granulated molybdenum powder in a glove box and in an argon environment, and controlling the aperture interval of a screen to obtain the denser granulated molybdenum powder with the particle size range of 30-40 microns.
And 6, establishing a high-frequency induction plasma torch with high energy density and stability by taking argon as working gas. The power of the plasma torch is 90kW, the working gas is high-purity argon, and the flow rate is 50 slpm; the side gas is high-purity argon, and the flow rate is 130 slpm; the system pressure at which the torch was operated was 90 kPa.
Step 7, using argon gas as carrier gas, and sending the granulated molybdenum powder into a high-temperature area at the core part of the plasma torch through a powder feeding probe, wherein the flow rate of the carrier gas is 10 slpm; the powder feeding rate of the molybdenum powder is 150 g/min; the granulated molybdenum powder is melted in a plasma torch and is spheroidized and densified under the action of surface tension.
Step 8, separating the molten molybdenum powder from the plasma torch, and allowing the molten molybdenum powder to freely fall into a heat exchange chamber under the action of gravity; heat exchangeThe chamber is a high-purity argon environment, and the ambient temperature is 28 ℃; the molybdenum powder is molten and dropped at not less than 1 x 104Cooling and solidifying under the temperature gradient of K/s to form compact spherical molybdenum powder.
Step 9, fully cooling the dense spherical molybdenum powder in a heat exchanger to 28 ℃, and opening a collector in a glove box and in a high-purity argon environment to collect the molybdenum powder; the collected scanning electron microscope photographs of the molybdenum powder are shown in FIG. 4, the molybdenum powder has a smooth surface, the density is more than 99%, the particle size of the molybdenum powder is 30-40 μm, the spheroidization rate is 85%, and the purity of the molybdenum powder is more than 99.99% in percentage by mass.
The invention has not been described in detail in part of the common general knowledge of those skilled in the art. The specific embodiments described are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
The present invention is not disclosed in the technical field of the common general knowledge of the technicians in this field.
Claims (7)
1. The preparation method of the high-purity compact spherical molybdenum powder is characterized by comprising the following steps of:
step 1: mixing reduced molybdenum powder with the Fisher size range of 0.5-6 mu m and the purity of more than 99.9 percent in terms of mass fraction, a binder and deionized water to prepare slurry;
step 2: carrying out spray granulation on the slurry, and drying to obtain molybdenum powder aggregates;
and step 3: degumming, impurity removal and sintering the molybdenum powder aggregate to obtain granulated molybdenum powder, wherein the degumming and impurity removal of the molybdenum powder aggregate are carried out in a hydrogen reducing atmosphere, and hydrogen is not recycled;
and 4, step 4: sieving the granulated molybdenum powder to obtain granulated molybdenum powder with a required particle size range, wherein the sieving operation of the granulated molybdenum powder is carried out in an argon environment, and the particle size interval of the granulated molybdenum powder obtained by sieving is not more than 10 mu m;
and 5: sending the granulated molybdenum powder with the required particle size range to a core area of a plasma torch to obtain molten molybdenum powder, wherein the power of the plasma torch is 30kW-100kW, the working gas is argon, the flow rate is 10slpm-50s lpm, the side gas is argon, the flow rate is 30slpm-150slpm, and the operating system pressure of the plasma torch is 40kPa-98 kPa;
step 6: cooling and solidifying the molten molybdenum powder in an argon atmosphere at the temperature of not more than 30 ℃, wherein the cooling speed is not less than 1 x 104K/s to obtain the high-purity compact spherical molybdenum powder.
2. The method for preparing high-purity dense spherical molybdenum powder according to claim 1, wherein: the binder is polyvinyl alcohol; the content of the binder is 1-10% of the total mass of the binder and the deionized water; the mass percentage of the solid phase in the slurry is 30-70%.
3. The method for preparing high-purity dense spherical molybdenum powder according to claim 1, wherein: in the step 2, the slurry is subjected to spray granulation by a centrifugal spray dryer; the air inlet temperature of the spray drying of the centrifugal spray dryer is 150-250 ℃, and the air outlet temperature is 110-190 ℃; the radius of the centrifugal disc is 0.1m-0.3m, and the rotating speed range is 10000r/min-15000 r/min; the atomization pressure range is 0.2MPa-0.8 MPa.
4. The method for preparing high-purity dense spherical molybdenum powder according to claim 1, wherein: the degumming and impurity removal temperature in the step 3 is 700-1100 ℃, and the degumming and impurity removal time is 1-5 h; and 3, sintering the molybdenum powder aggregate in the hydrogen atmosphere at the sintering temperature of 1100-1500 ℃ for 1-3 h.
5. The method for preparing high-purity dense spherical molybdenum powder according to claim 1, wherein: and 5, conveying the granulated molybdenum powder with the required particle size range into the core area of the plasma torch by using a carrier gas, wherein the carrier gas is argon, the flow rate is 1slpm-10slpm, and the powder conveying speed of the granulated molybdenum powder is 40g/min-200 g/min.
6. The method for preparing high-purity dense spherical molybdenum powder according to claim 1, wherein: the range of the grain diameter of the high-purity compact spherical molybdenum powder formed in the step 6 is 10-50 μm, the grain diameter interval is less than 10 μm, the spheroidization rate is more than 90%, and the purity of the molybdenum powder is more than 99.99% in terms of mass fraction.
7. Use of the high purity dense spherical molybdenum powder prepared by the preparation method according to any one of claims 1 to 6 in the fields of 3D printing, powder metallurgy and thermal spraying.
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| CN108115147A (en) * | 2017-12-04 | 2018-06-05 | 中国兵器科学研究院宁波分院 | A kind of complete closely knit, the spherical molybdenum powder of high apparent density the preparation method of cold spraying |
| CN107931622A (en) * | 2017-12-14 | 2018-04-20 | 西北有色金属研究院 | A kind of preparation method of refractory material spherical powder |
| MX2020009146A (en) * | 2018-03-05 | 2020-09-28 | Global Advanced Metals Usa Inc | Anodes containing spherical powder and capacitors. |
| CN109014198A (en) * | 2018-08-16 | 2018-12-18 | 北京科技大学 | A method of preparing the pure molybdenum part of high-performance |
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| CN109434117B (en) * | 2018-09-20 | 2021-12-07 | 中国航天空气动力技术研究院 | Preparation method of spherical zirconium-niobium alloy powder for 3D printing |
| CN109692965A (en) * | 2019-02-27 | 2019-04-30 | 北京工业大学 | A kind of preparation method of the spherical tungsten-molybdenum alloy powder of 3D printing |
| CN110576180B (en) * | 2019-09-25 | 2022-01-11 | 福建阿石创新材料股份有限公司 | Preparation method of molybdenum powder with low oxygen content |
| CN113000833A (en) * | 2021-02-23 | 2021-06-22 | 郑州大学 | Ti-6Al-4V alloy spherical powder for additive manufacturing and preparation method thereof |
| CN115502405A (en) * | 2022-09-07 | 2022-12-23 | 金川集团股份有限公司 | Method for preparing spherical nickel powder by using controllable plasma method |
| CN117000993B (en) * | 2023-08-04 | 2024-03-26 | 湖南宏承新材料科技有限公司 | Preparation method of tantalum powder for metal additive manufacturing |
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