CN113800522A - Method for preparing high-purity compact tungsten carbide-cobalt composite spherical powder material - Google Patents
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Abstract
The invention discloses a method for preparing a high-purity compact tungsten carbide-cobalt composite spherical powder material, which comprises the steps of mechanical mixing, spray granulation, atmosphere calcination degreasing and radio frequency plasma spheroidization/densification, wherein the tungsten carbide of the tungsten carbide-cobalt composite powder is 80-95% by mass, and the cobalt of the tungsten carbide-cobalt composite powder is 5-20% by mass. The invention has the advantages that: the high-purity compact spherical tungsten carbide-cobalt composite powder prepared by adopting mechanical mixing, spray granulation, atmosphere high-temperature calcination degreasing and combining with a radio frequency plasma spheroidizing process is particularly suitable for 3D printing, powder metallurgy, thermal spraying and other processes, has high sphericity, narrow particle size distribution and excellent flow property, ensures good powder laying or filling effect in the using process, and is beneficial to obtaining high-density formed products.
Description
Technical Field
The invention relates to the technical field of 3D printing, the technical field of powder metallurgy materials, the technical field of thermal spraying materials and the technical field of hard alloys, in particular to a method for preparing a high-purity compact tungsten carbide-cobalt composite spherical powder material.
Background
Tungsten carbide has the advantages of high melting point, high hardness, poor electric and thermal conductivity, stable chemical property and the like, is an ideal material for preparing wear-resistant and corrosion-resistant products, and is widely applied to the fields of aerospace, machinery, petrochemical industry, metallurgy, electric power engineering and the like. Because tungsten carbide has high melting point, high hardness and obvious brittleness, and is difficult to form by adopting traditional casting, machining and other methods, the tungsten carbide powder is rarely used in the fields of 3D printing, powder metallurgy, thermal spraying and the like independently, and other metals or alloys such as Co, Ni, Cr, Cu, Ni-Cr and the like are usually required to be added as a binding phase to prepare a composite powder material for use.
The commonly used preparation methods of the tungsten carbide-cobalt composite powder material comprise a sintering crushing method, a traditional agglomeration sintering method and the like, but the preparation methods are complex, have the problems of long production period, low production efficiency, large energy consumption and the like, and have the common technical problems of irregular powder appearance, poor sphericity, poor flow property, uneven component distribution, uncontrollable impurity content and the like.
Further, similar reports also appear in the prior patent publications:
reduction and mechanical mixing to prepare tungsten carbide-cobalt composite powder, and the patent publication number is CN 106583707A:
sodium ammonium paratuberate is adopted to prepare sodium-containing yellow tungsten oxide in an industrial rotary kiln, then the sodium-containing yellow tungsten oxide is subjected to reverse hydrogen reduction in a fourteen-tube reduction furnace to prepare ultra-coarse tungsten powder, the ultra-coarse tungsten powder is mixed with pure carbon black, the ultra-coarse tungsten carbide powder is prepared in a continuous high-temperature large-Tan-tube furnace, and finally the ultra-coarse tungsten carbide powder and pure spherical cobalt powder are mixed in a double-cone mixer to prepare the ultra-coarse tungsten carbide cobalt composite powder. The method has the advantages of complex process flow, low purity of the ultra-coarse tungsten powder, difficult control of the content of carbon element in the tungsten carbide powder, uneven distribution of cobalt element in the composite powder, irregular powder morphology and poor sphericity, can not meet the requirement of screening and obtaining narrow-interval powder products in the fields of 3D printing, thermal spraying and the like, and is not beneficial to practical large-scale application.
The technology for preparing the nano tungsten carbide-cobalt composite powder by a chemical method has the following patent publication No. CN 103056381A: the product prepared by the method is nano composite powder, the powder has irregular shape, the purity is difficult to control, and the fluidity still cannot meet the fields of 3D printing, thermal spraying and the like.
Technology for preparing tungsten carbide-cobalt composite powder in fluidization mode
The fluidization preparation method of the tungsten carbide cobalt composite powder is CN 101767204A: the method takes the tungsten-cobalt composite oxide powder as a raw material, the tungsten-cobalt composite oxide powder is prepared by adopting a fluidized bed reduction technology, the control difficulty of the element components of the composite powder is high, the production efficiency is not high, and the prepared powder is in a non-spherical shape and does not meet the requirements of the fields of 3D printing, thermal spraying and the like.
The technology for preparing tungsten carbide-cobalt composite powder by granulation and sintering has patent publication No. CN 102876907A: the technology mixes tungsten carbide powder and cobalt powder according to a certain proportion, prepares slurry, carries out spray granulation, carries out screening and degreasing treatment, and rapidly sinters in a vertical high-temperature sintering furnace to finally obtain spherical tungsten carbide-cobalt composite powder. The method is a preparation technology of near-spherical tungsten carbide-cobalt composite powder in the field of mainstream thermal spraying at present. However, the composite powder prepared by the method has low binding force between cobalt and tungsten carbide powder, and the stability of the processing technology is poor due to powder crushing in the practical application process. Most importantly, a large number of cavities are formed in the granulated and sintered composite powder, so that the granulated and sintered composite powder is not dense, and the loose packing density and the tap density are low, so that a large number of micropores and air gaps exist in products in the fields of 3D printing, thermal spraying or injection molding, and the comprehensive mechanical property of the product is further influenced.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for preparing a high-purity compact tungsten carbide-cobalt composite spherical powder material.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the preparation method of the high-purity compact tungsten carbide-cobalt composite spherical powder material comprises the working procedures of mechanical mixing, spray granulation, atmosphere calcination degreasing and radio frequency plasma spheroidization/densification, wherein the tungsten carbide of the tungsten carbide-cobalt composite powder is 80-95% by weight, and the cobalt of the tungsten carbide-cobalt composite powder is 5-20% by weight.
The mechanical mixing process includes: weighing raw material powder with the mass corresponding to that of the tungsten carbide and the cobalt, drying in vacuum, and then loading into a V-shaped mixer for mixing for 60-300min to prepare the tungsten carbide-cobalt composite powder body which is uniformly mixed.
The spray granulation step includes:
s1 is mixed with deionized water according to the mass ratio of 1-4, and 2-5 wt.% of binder is slowly added, stirred and heated until completely dissolved, so as to form uniform and stable slurry.
S2, the slurry prepared in the step S1 is granulated through a centrifugal spray drying tower to obtain a granulated composite powder, and then the granulated composite powder enters the atmosphere calcination degreasing process.
The atmosphere calcination degreasing step includes: and (5) calcining the tungsten carbide-cobalt composite powder with the nearly spherical shape obtained after the granulation in the step S2 for 1-4h under the atmosphere of argon at the temperature of 500-850 ℃ to fully decompose, volatilize and remove the binder in the tungsten carbide-cobalt composite powder.
It should be noted that the rf plasma spheroidizing/densifying process includes:
s1, the tungsten carbide-cobalt granulation composite powder which is calcined and degreased in the atmosphere and has a nearly spherical shape is screened by a 270-mesh sieve, undersize is taken, and the undersize is put into a powder feeding system of a radio frequency plasma spheroidizing powder making device PFD-401;
s2, starting a system torch and a powder feeding probe cooling water system, and purifying a reaction chamber, a powder feeder and a powder collector of the radio frequency plasma spheroidizing powder making device in a mode of repeatedly vacuumizing and filling argon; inputting a certain amount of argon continuous airflow into a plasma reactor, wherein the central gas argon flow is 14-20L/min, the sheath gas argon flow is 40-60L/min, the pressure of the reaction chamber is set to be 1.5-2.5psia, a radio frequency induction coil is loaded with high voltage, the voltage is 6-8kV, simultaneously, arc striking discharge is carried out, argon is ionized to generate an argon plasma torch, the plasma power is 30kW, a certain amount of high-purity hydrogen is slowly added into the sheath gas, and the hydrogen flow is 3-10L/min; simultaneously, slowly increasing the power and the pressure of the reaction chamber to 40kW and 14.5-16.5psia respectively; the whole plasma reactor is kept in dynamic balance of certain pressure, and the stable operation of the radio frequency plasma torch is ensured.
S3, conveying the tungsten carbide-cobalt granulated composite powder with a nearly spherical shape into a high-temperature area at the center of a plasma torch for heating by utilizing carrier gas; the heating time ends with the gas/powder flow "flying off" the plasma torch for a duration of about 100 and 200 milliseconds. The granulated composite powder is sent into a central high-temperature area of a plasma torch, under the action of four heat transfer mechanisms of radiation, convection, conduction and chemistry, a large amount of heat is absorbed, the surface of the particle is rapidly heated and melted, when more than 50% of the weight of the particle is melted, the melted particle forms liquid drops with high sphericity under the action of surface tension, and is rapidly cooled under an extremely high temperature gradient, so that spherical particles are formed; wherein the temperature gradient is 103-106K/m。
S4 after the spheroidizing of the RF plasma, the system is vacuumized to 1.5-2.5psia and purified for 1-2 times to collect the high-purity compact tungsten carbide-cobalt spherical composite spherical powder.
Further, the binder is paraffin or polyethylene glycol, and is stirred and heated for 1-3 h.
Further, the feeding speed of the spray drying tower is 20-80ml/min, the inlet temperature is controlled at 250 ℃ of 200-; and granulating to obtain tungsten carbide-cobalt composite powder containing the binder, wherein the particle size is 15-53 mu m, and the morphology is nearly spherical.
Further, in the step S1, the rotational speed of the PFD-401 turntable is adjusted to 2.0 to 5.0RPM, the flow rate of carrier gas argon is 0 to 3.5L/min, the flow rate of dispersion gas argon is 0 to 2.0L/min, the flow rate of center gas argon is 14 to 20L/min, the flow rate of sheath gas argon is 40 to 60L/min, the flow rate of sheath gas hydrogen is 3 to 10L/min, the power is 40kW, and the powder feeding rate of the tungsten carbide-cobalt granulation composite powder is 30 to 120 g/min.
The invention has the beneficial effects that:
1. the high-purity compact spherical tungsten carbide-cobalt composite powder prepared by adopting mechanical mixing, spray granulation, atmosphere high-temperature calcination degreasing and combining with a radio frequency plasma spheroidizing process is particularly suitable for 3D printing, powder metallurgy, thermal spraying and other processes, has high sphericity, narrow particle size distribution and excellent flow property, ensures good powder laying or filling effect in the using process, and is beneficial to obtaining high-density formed products. Solves the problems that the contents of carbon, tungsten and cobalt elements are difficult to control, the distribution of the cobalt elements is uneven, the powder appearance is irregular, the sphericity is poor, the flow property is poor, the interior of particles is not compact and the like in the chemical preparation process.
2. The spheroidization and densification of the granulated tungsten carbide-cobalt composite powder are carried out by adopting a radio frequency plasma spheroidization process, the plasma ultrahigh temperature characteristic (8000-.
Drawings
FIG. 1 is a schematic process flow diagram of the present invention;
FIG. 2 is a scanning electron microscope topography of the tungsten carbide-cobalt granulated composite powder prior to RF plasma spheroidization/densification in accordance with the present invention;
FIG. 3 is a scanning electron microscope topography of the tungsten carbide-cobalt granulated composite powder after spheroidization/densification by RF plasma.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, and it should be noted that the present embodiment is based on the technical solution, and the detailed implementation and the specific operation process are provided, but the protection scope of the present invention is not limited to the present embodiment.
As shown in fig. 1, the present invention is a method for preparing a high-purity dense tungsten carbide-cobalt composite spherical powder material, wherein the preparation of the high-purity dense tungsten carbide-cobalt composite spherical powder comprises the steps of mechanical mixing, spray granulation, atmosphere calcination degreasing and radio frequency plasma spheroidization/densification, wherein the tungsten carbide of the tungsten carbide-cobalt composite powder is 80-95% by mass, and the cobalt of the tungsten carbide-cobalt composite powder is 5-20% by mass.
The mechanical mixing process includes: weighing raw material powder with the mass corresponding to that of the tungsten carbide and the cobalt, drying in vacuum, and then loading into a V-shaped mixer for mixing for 60-300min to prepare the tungsten carbide-cobalt composite powder body which is uniformly mixed.
The spray granulation step includes:
s1 is mixed with deionized water according to the mass ratio of 1-4, and 2-5 wt.% of binder is slowly added, stirred and heated until completely dissolved, so as to form uniform and stable slurry.
S2, the slurry prepared in the step S1 is granulated through a centrifugal spray drying tower to obtain a granulated composite powder, and then the granulated composite powder enters the atmosphere calcination degreasing process.
The atmosphere calcination degreasing step includes: and (5) calcining the tungsten carbide-cobalt composite powder with the nearly spherical shape obtained after the granulation in the step S2 for 1-4h under the atmosphere of argon at the temperature of 500-850 ℃ to fully decompose, volatilize and remove the binder in the tungsten carbide-cobalt composite powder.
It should be noted that the rf plasma spheroidizing/densifying process includes:
s1, the tungsten carbide-cobalt granulation composite powder which is calcined and degreased in the atmosphere and has a nearly spherical shape is screened by a 270-mesh sieve, undersize is taken, and the undersize is put into a powder feeding system of a radio frequency plasma spheroidizing powder making device PFD-401;
s2, starting a system torch and a powder feeding probe cooling water system, and purifying a reaction chamber, a powder feeder and a powder collector of the radio frequency plasma spheroidizing powder making device in a mode of repeatedly vacuumizing and filling argon; inputting a certain amount of argon continuous airflow into a plasma reactor, wherein the central gas argon flow is 14-20L/min, the sheath gas argon flow is 40-60L/min, the pressure of the reaction chamber is set to be 1.5-2.5psia, a radio frequency induction coil is loaded with high voltage, the voltage is 6-8kV, simultaneously, arc striking discharge is carried out, argon is ionized to generate an argon plasma torch, the plasma power is 30kW, a certain amount of high-purity hydrogen is slowly added into the sheath gas, and the hydrogen flow is 3-10L/min; simultaneously, slowly increasing the power and the pressure of the reaction chamber to 40kW and 14.5-16.5psia respectively; the whole plasma reactor is kept in dynamic balance of certain pressure, and the stable operation of the radio frequency plasma torch is ensured.
S3, conveying the tungsten carbide-cobalt granulated composite powder with a nearly spherical shape into a high-temperature area at the center of a plasma torch for heating by utilizing carrier gas; the heating time ends with the gas/powder flow "flying off" the plasma torch for a duration of about 100 and 200 milliseconds. The granulated composite powder is sent into a central high-temperature area of a plasma torch, under the action of four heat transfer mechanisms of radiation, convection, conduction and chemistry, a large amount of heat is absorbed, the surface of the particle is rapidly heated and melted, when more than 50% of the weight of the particle is melted, the melted particle forms liquid drops with high sphericity under the action of surface tension, and is rapidly cooled under an extremely high temperature gradient, so that spherical particles are formed; wherein the temperature gradient is 103-106K/m。
S4 after the spheroidizing of the RF plasma, the system is vacuumized to 1.5-2.5psia and purified for 1-2 times to collect the high-purity compact tungsten carbide-cobalt spherical composite spherical powder.
Further, the binder is paraffin or polyethylene glycol, and is stirred and heated for 1-3 h.
Further, the feeding speed of the spray drying tower is 20-80ml/min, the inlet temperature is controlled at 250 ℃ of 200-; and granulating to obtain tungsten carbide-cobalt composite powder containing the binder, wherein the particle size is 15-53 mu m, and the morphology is nearly spherical.
Further, in the step S1, the rotational speed of the PFD-401 turntable is adjusted to 2.0 to 5.0RPM, the flow rate of carrier gas argon is 0 to 3.5L/min, the flow rate of dispersion gas argon is 0 to 2.0L/min, the flow rate of center gas argon is 14 to 20L/min, the flow rate of sheath gas argon is 40 to 60L/min, the flow rate of sheath gas hydrogen is 3 to 10L/min, the power is 40kW, and the powder feeding rate of the tungsten carbide-cobalt granulation composite powder is 30 to 120 g/min.
Example 1
Weighing raw material powder with corresponding mass according to the proportion of the tungsten carbide (94%) and the cobalt (6%) in the tungsten carbide-cobalt composite powder, vacuum drying, and mixing in a V-shaped mixer for 120 min. According to the mass ratio of the tungsten carbide-cobalt composite powder to the deionized water of 1: and 2, measuring corresponding deionized water, slowly adding 3.0 wt.% of polyethylene glycol, stirring and heating for 2 hours until the polyethylene glycol is completely dissolved, and obtaining uniform and stable slurry.
And (4) granulating the slurry through a centrifugal spray drying tower to obtain the granulated composite powder. Wherein the feeding rate of the spray drying tower is 40ml/min, the inlet temperature is controlled at 220 ℃, the outlet temperature is controlled at 110 ℃, and the rotating speed of the motor is 4500 r/min.
And calcining the tungsten carbide-cobalt composite powder obtained after granulation for 2.5 hours at the temperature of 750 ℃ under the argon atmosphere. And (3) sieving the tungsten carbide-cobalt granulation composite powder through a 270-mesh sieve, and taking undersize products.
And a radio frequency plasma powder-making device is adopted for spheroidization/densification treatment, the rotating speed of a spheroidization/densification treatment PFD-401 rotating disc is 3.5RPM, the flow of carrier gas argon is 2.0L/min, the flow of dispersion gas argon is 1.0L/min, and the powder feeding speed is about 50 g/min. The central gas argon flow is 19.5L/min, the sheath gas argon flow is 50L/min, the sheath gas hydrogen flow is 5L/min, and the power is 40 kW.
Example 2
Weighing raw material powder with corresponding mass according to the proportion of the tungsten carbide (92%) and the cobalt (8%) in the tungsten carbide-cobalt composite powder, vacuum drying, and mixing in a V-shaped mixer for 120 min. According to the mass ratio of the tungsten carbide-cobalt composite powder to the deionized water of 1: and 2, measuring corresponding deionized water, slowly adding 3.0 wt.% of polyethylene glycol, stirring and heating for 2 hours until the polyethylene glycol is completely dissolved, and obtaining uniform and stable slurry.
And (4) granulating the slurry through a centrifugal spray drying tower to obtain the granulated composite powder. Wherein the feeding rate of the spray drying tower is 40ml/min, the inlet temperature is controlled at 220 ℃, the outlet temperature is controlled at 110 ℃, and the rotating speed of the motor is 4500 r/min.
And calcining the tungsten carbide-cobalt composite powder obtained after granulation for 2.5 hours at the temperature of 750 ℃ under the argon atmosphere. And (3) sieving the tungsten carbide-cobalt granulation composite powder through a 270-mesh sieve, and taking undersize products.
And a radio frequency plasma powder-making device is adopted for spheroidization/densification treatment, the rotating speed of a rotating disc of the spheroidization/densification treatment PFD-401 is 4.0RPM, the flow of carrier gas argon is 2.0L/min, the flow of dispersion gas argon is 1.0L/min, and the powder feeding speed is about 60 g/min. The central gas argon flow is 19.5L/min, the sheath gas argon flow is 50L/min, the sheath gas hydrogen flow is 8L/min, and the power is 40 kW.
Example 3
Weighing raw material powder with corresponding mass according to the proportion of the tungsten carbide (88%) and the cobalt (12%) in the tungsten carbide-cobalt composite powder, drying in vacuum, and mixing in a V-shaped mixer for 120 min. According to the mass ratio of the tungsten carbide-cobalt composite powder to the deionized water of 1: and 2, measuring corresponding deionized water, slowly adding 3.0 wt.% of polyethylene glycol, stirring and heating for 2 hours until the polyethylene glycol is completely dissolved, and obtaining uniform and stable slurry.
And (4) granulating the slurry through a centrifugal spray drying tower to obtain the granulated composite powder. Wherein the feeding rate of the spray drying tower is 40ml/min, the inlet temperature is controlled at 220 ℃, the outlet temperature is controlled at 110 ℃, and the rotating speed of the motor is 4500 r/min.
And calcining the tungsten carbide-cobalt composite powder obtained after granulation for 2.5 hours at the temperature of 750 ℃ under the argon atmosphere. And (3) sieving the tungsten carbide-cobalt granulation composite powder through a 270-mesh sieve, and taking undersize products.
And a radio frequency plasma powder-making device is adopted for spheroidization/densification treatment, the rotating speed of a spheroidization/densification treatment PFD-401 rotating disc is 5.0RPM, the flow of carrier gas argon is 2.0L/min, the flow of dispersion gas argon is 2.0L/min, and the powder feeding speed is about 70 g/min. The central gas argon flow is 19.5L/min, the sheath gas argon flow is 50L/min, the sheath gas hydrogen flow is 10L/min, and the power is 40 kW.
Example 4
Weighing raw material powder with corresponding mass according to the proportion of the tungsten carbide (88%) and the cobalt (20%) in the tungsten carbide-cobalt composite powder, vacuum drying, and mixing in a V-shaped mixer for 120 min. According to the mass ratio of the tungsten carbide-cobalt composite powder to the deionized water of 1: and 2, measuring corresponding deionized water, slowly adding 3.0 wt.% of polyethylene glycol, stirring and heating for 2 hours until the polyethylene glycol is completely dissolved, and obtaining uniform and stable slurry.
And (4) granulating the slurry through a centrifugal spray drying tower to obtain the granulated composite powder. Wherein the feeding rate of the spray drying tower is 40ml/min, the inlet temperature is controlled at 220 ℃, the outlet temperature is controlled at 110 ℃, and the rotating speed of the motor is 4500 r/min.
And calcining the tungsten carbide-cobalt composite powder obtained after granulation for 2.5 hours at the temperature of 750 ℃ under the argon atmosphere. And (3) sieving the tungsten carbide-cobalt granulation composite powder through a 270-mesh sieve, and taking undersize products.
And a radio frequency plasma powder-making device is adopted for spheroidization/densification treatment, the rotating speed of a spheroidization/densification treatment PFD-401 rotating disc is 5.0RPM, the flow of carrier gas argon is 2.0L/min, the flow of dispersion gas argon is 2.0L/min, and the powder feeding speed is about 70 g/min. The central gas argon flow is 19.5L/min, the sheath gas argon flow is 50L/min, the sheath gas hydrogen flow is 10L/min, and the power is 40kW
Various other changes and modifications to the above-described embodiments and concepts will become apparent to those skilled in the art from the above description, and all such changes and modifications are intended to be included within the scope of the present invention as defined in the appended claims.
Claims (8)
1. The preparation method of the high-purity compact tungsten carbide-cobalt composite spherical powder material is characterized in that the preparation of the high-purity compact tungsten carbide-cobalt composite spherical powder comprises the working procedures of mechanical mixing, spray granulation, atmosphere calcination degreasing and radio frequency plasma spheroidization/densification, wherein the tungsten carbide of the tungsten carbide-cobalt composite powder is 80-95% by weight, and the cobalt of the tungsten carbide-cobalt composite powder is 5-20% by weight.
2. The method for preparing the high-purity compact tungsten carbide-cobalt composite spherical powder material according to claim 1, wherein the mechanical mixing process comprises the following steps: weighing raw material powder with the mass corresponding to that of the tungsten carbide and the cobalt, drying in vacuum, and then loading into a V-shaped mixer for mixing for 60-300min to prepare the tungsten carbide-cobalt composite powder body which is uniformly mixed.
3. The method for preparing the high-purity compact tungsten carbide-cobalt composite spherical powder material according to claim 1, wherein the spray granulation process comprises the following steps:
s1 is mixed with deionized water according to the mass ratio of 1-4, and 2-5 wt.% of binder is slowly added, stirred and heated until completely dissolved, so as to form uniform and stable slurry.
S2, the slurry prepared in the step S1 is granulated through a centrifugal spray drying tower to obtain a granulated composite powder, and then the granulated composite powder enters the atmosphere calcination degreasing process.
4. The method for preparing the high-purity compact tungsten carbide-cobalt composite spherical powder material according to claim 1 or 3, wherein the atmosphere calcination degreasing process comprises the following steps: and (5) calcining the tungsten carbide-cobalt composite powder with the nearly spherical shape obtained after the granulation in the step S2 for 1-4h under the atmosphere of argon at the temperature of 500-850 ℃ to fully decompose, volatilize and remove the binder in the tungsten carbide-cobalt composite powder.
5. The method for preparing the high-purity compact tungsten carbide-cobalt composite spherical powder material according to claim 1, wherein the radio frequency plasma spheroidization/densification process comprises:
s1, the tungsten carbide-cobalt granulation composite powder which is calcined and degreased in the atmosphere and has a nearly spherical shape is screened by a 270-mesh sieve, undersize is taken, and the undersize is put into a powder feeding system of a radio frequency plasma spheroidizing powder making device PFD-401;
s2, starting a system torch and a powder feeding probe cooling water system, and purifying a reaction chamber, a powder feeder and a powder collector of the radio frequency plasma spheroidizing powder making device in a mode of repeatedly vacuumizing and filling argon; inputting a certain amount of argon continuous airflow into a plasma reactor, wherein the central gas argon flow is 14-20L/min, the sheath gas argon flow is 40-60L/min, the pressure of the reaction chamber is set to be 1.5-2.5psia, a radio frequency induction coil is loaded with high voltage, the voltage is 6-8kV, simultaneously, arc striking discharge is carried out, argon is ionized to generate an argon plasma torch, the plasma power is 30kW, a certain amount of high-purity hydrogen is slowly added into the sheath gas, and the hydrogen flow is 3-10L/min; simultaneously, slowly increasing the power and the pressure of the reaction chamber to 40kW and 14.5-16.5psia respectively; the whole plasma reactor is kept in dynamic balance of certain pressure, and the stable operation of the radio frequency plasma torch is ensured.
S3, conveying the tungsten carbide-cobalt granulated composite powder with a nearly spherical shape into a high-temperature area at the center of a plasma torch for heating by utilizing carrier gas; the heating time ends with the gas/powder flow "flying off" the plasma torch for a duration of about 100 and 200 milliseconds. The granulated composite powder is sent into a central high-temperature area of a plasma torch, under the action of four heat transfer mechanisms of radiation, convection, conduction and chemistry, a large amount of heat is absorbed, the surface of the particle is rapidly heated and melted, when more than 50% of the weight of the particle is melted, the melted particle forms liquid drops with high sphericity under the action of surface tension, and is rapidly cooled under an extremely high temperature gradient, so that spherical particles are formed; wherein the temperature gradient is 103-106K/m。
S4 after the spheroidizing of the RF plasma, the system is vacuumized to 1.5-2.5psia and purified for 1-2 times to collect the high-purity compact tungsten carbide-cobalt spherical composite spherical powder.
6. The method for preparing the high-purity compact tungsten carbide-cobalt composite spherical powder material according to claim 3, wherein the binder is paraffin or polyethylene glycol, and the mixture is stirred and heated for 1-3 h.
7. The method for preparing the high-purity compact tungsten carbide-cobalt composite spherical powder material as claimed in claim 3, wherein the feeding rate of the spray drying tower is 20-80ml/min, the inlet temperature is controlled at 250 ℃ of 200-; and granulating to obtain tungsten carbide-cobalt composite powder containing the binder, wherein the particle size is 15-53 mu m, and the morphology is nearly spherical.
8. The method for preparing the high-purity compact tungsten carbide-cobalt composite spherical powder material according to claim 5, wherein in the step S1, the rotating speed of a PFD-401 rotating disc is adjusted to be 2.0-5.0RPM, the flow rate of carrier gas argon is adjusted to be 0-3.5L/min, the flow rate of dispersion gas argon is adjusted to be 0-2.0L/min, the flow rate of center gas argon is adjusted to be 14-20L/min, the flow rate of sheath gas argon is adjusted to be 40-60L/min, the flow rate of sheath gas hydrogen is adjusted to be 3-10L/min, the power is 40kW, and the powder feeding rate of the tungsten carbide-cobalt granulated composite powder is adjusted to be 30-120 g/min.
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