CN113857474A - Preparation method of WC surface-coated Co powder added with Ce element - Google Patents
Preparation method of WC surface-coated Co powder added with Ce element Download PDFInfo
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- C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
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- C22C29/067—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds comprising a particular metallic binder
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- C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
- C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
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Abstract
The invention discloses a method for preparing WC surface-coated Co powder added with Ce element, which comprises the steps of mixing soluble cerium salt and soluble cobalt salt aqueous solution to obtain mixed solution; adding an ammonium oxalate aqueous solution and tungsten carbide into the mixed solution, uniformly stirring, and drying to obtain composite powder; and carrying out reduction reaction on the composite powder in a hydrogen protective atmosphere, and cooling to obtain the WC-Co-Ce composite powder. According to the preparation method, the surface layer of the WC powder can be uniformly coated with the cobalt element and the cerium element, so that the problems that the rare earth element is easy to oxidize when doped in the preparation process of the hard alloy by the traditional ball milling method and the uniformity of the rare earth in the mixed material is difficult to solve when the addition amount is small are solved, and the dispersibility of the rare earth element is improved; the preparation method has high repeatability, and can ensure the stability of the product.
Description
Technical Field
The invention relates to a preparation method of WC surface-coated Co powder added with Ce element, belonging to the technical field of powder metallurgy.
Background
In recent years, due to the continuous development of coal field mining and tunnel engineering technologies, hard alloy is used as a cutter head material of a coal mining machine and a tunnel tunneling shield machine, the coal mining machine and the tunnel tunneling shield machine are operated underground, the working environment is severe, the cutter head replacement and maintenance difficulty is high, the replacement and maintenance frequency is generally reduced as much as possible, and high wear resistance, high toughness and other performance requirements are provided for the hard alloy cutter head. Co is most widely applied due to the excellent wettability of the Co on WC, and the prepared WC-Co hard alloy has good mechanical property; the document (Houke faithful, Baikuai, development of hard alloy blades for shield machines [ J ]. powder metallurgy industry, 2009,19(03):36-40.) reports that for the conditions of serious abrasion, fracture failure and the like of the current shield cutters, the performance characteristics of toughness, wear resistance and the like of ultra-coarse grain hard alloy are analyzed, and the shield cutters have good adaptability to complex change working conditions of underground soil quality and water pressure in construction. WC and Co with the Fsss granularity of 16-28 mu m are used as raw materials, a novel alloy is prepared by adopting a phase change control technology and a densification treatment technology, the developed alloy material obtains good comprehensive performance, and the shield cutter is prepared and has the same using effect as that of an imported similar product after being examined; there have been patent reports on methods for producing super-coarse grain cemented carbide, such as a method for producing high-toughness super-coarse grain cemented carbide (201010553047.2); a preparation method (201010172891.0) of ultra-coarse grain hard alloy, and the like. The preparation of the ultra-coarse or ultra-coarse crystal hard alloy must adopt coarse crystal, ultra-coarse or ultra-coarse crystal raw materials. The traditional mechanical mixing process can reduce the granularity of tungsten carbide particles while improving the uniformity of mixed materials, so that the grain size of the sintered alloy is reduced to the fine grain standard. To further enhance performance, additives such as rare earths may further enhance the flexural strength, impact toughness, and durability of the cemented carbide.
However, in the conventional process for preparing hard alloy by solid-phase mixing, most of the rare earth elements are added in a solid powder form and mixed with other alloy powder, and rare earth oxide is added in a solid form, so that the heat strength of the alloy can be improved, but the thermoplasticity and the toughness of the alloy can be reduced; the pure rare earth element is added in a powder form, so that uniform dispersion is difficult to ensure due to small addition amount, and the hard alloy with more than coarse grains is more difficult, so that a brittle phase and a brittle interface of rare earth/hard phase are aggregated in the hard alloy, and the strength and toughness of the alloy interface are reduced; these problems severely affect the use of rare earth elements in cemented carbides at the present stage.
Disclosure of Invention
The invention provides a method for preparing WC surface-coated Co powder added with Ce element, which aims at solving the problems in the prior art, the WC-Co-Ce powder is obtained by chemical coating-hydrogen reduction, most of the Ce powder in the powder is coated in Co particles, so that the contact and oxidation with oxygen in the air are reduced, the cobalt element and the cerium element can be uniformly coated on the surface layer of the WC powder, the uniformity of the powder can be effectively improved, the repeatability of the preparation method is high, and the stability of the product can be ensured.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for preparing WC surface-coated Co powder added with Ce element comprises the following steps:
step 1: grinding and coarsening to form coarsened WC powder:
grinding WC powder for 1-5 h by adopting a mortar, and preparing components including HF and HNO3Pouring the grinded WC powder into the coarsening liquid, uniformly stirring, fully dispersing and coarsening, filtering to obtain coarsened WC powder, washing and drying；
Step 2: preparing a composite powder precursor:
dissolving soluble CoCl2And CeCl3Mixing the aqueous solutions to obtain a mixed solution; adding the coarsened WC powder into the mixed solution to ensure that the surface of the WC particles is fully contacted with the mixed solution, and then dropwise adding (NH) in an atomization-spraying manner4)2C2O4Uniformly stirring the aqueous solution to perform a precipitation reaction, and drying the aqueous solution after the precipitation reaction is finished to obtain composite powder precursor powder, wherein the precipitation reaction formula is as follows:
CoCl2·6H2O+4(NH4)2C2O4·H2O+2CeCl3→CoC2O4·2H2O↓+Ce2(C2O4)3+8NH4Cl+5H2O
and step 3: reducing a composite powder precursor:
adding composite powder precursor powder in H2Carrying out reduction reaction in a protective atmosphere, and cooling to obtain WC-Co-Ce composite powder, wherein the reduction reaction equation is as follows:
2CoC2O4·2H2O+Ce2(C2O4)3+17H2→2Co+2Ce+CO2↑+3CO↑+17H2O。
wherein, the concentration of each component of the coarsening liquid in the step 1 is as follows: the concentration of HF is 20-40 mL/L, and HNO3The concentration of (A) is 20-40 mL/L; the volume of the roughening liquid for roughening the WC powder at the first time is 400-600 mL, the uniform stirring time is 20-40 min, and the obtained product is washed by ionized water for 3-5 times.
And 2, an ultrasonic-standing mode is adopted to achieve the effect of full solid-liquid contact in the step 2, the ultrasonic time is 10-30 min, and the standing time is 2-4 h.
Preferably, when the reaction in the step 2 is carried out, continuously stirring and uniformly mixing in a mechanical stirring mode, wherein the rotating speed is 300-500 r/min, and the stirring time is 60-80 min; and after stopping stirring, standing the mixed solution for 20-30 minutes, and drying in a vacuum drying oven to obtain mixed powder precursor powder.
Preferably, CoCl in step 22And (NH)4)2C2O4The molar ratio of (A) to (B) is 1: 1.6-2.0. Further, the precipitation reaction time of the step 2 is 1-2 hours, and the precipitation reaction temperature is 50-60 ℃. Preferably 60 deg.c.
Further, the addition sequence of the precipitation reaction in the step 2 is as follows: (NH)4)2C2O4The aqueous solution was slowly added to CoCl2And CeCl3In the mixed aqueous solution of (NH)4)2C2O4The aqueous solution is added by adopting a full-automatic atomizer atomization-spraying mode, and the atomization-spraying speed is 50 mL/min.
Preferably, the pH value of the reaction solution in the step 2 is 4-7, more preferably 5-6, and Co element is prevented from forming Co (OH) under the alkaline condition2Preferentially precipitate out, and influence the generation of composite precipitates on the WC surface.
Preferably, grinding and separating agglomerated particles are carried out before the reduction reaction of the composite powder precursor powder in the step 3, and then screening is carried out by adopting a 200-mesh screen, wherein the grinding time is 10-30 min.
Preferably, the temperature of the reduction reaction in the step 3 is 500-800 ℃ and the time is 120-180 min. More preferably, the temperature is 500 ℃ and the time of the decomposition reaction is 120 min.
The invention has the beneficial effects that:
the invention provides a method for preparing WC surface-coated Co powder added with Ce element, which aims at solving the problems in the prior art, the WC-Co-Ce powder is obtained by chemical coating-hydrogen reduction, most of the Ce powder in the powder is coated in Co particles, so that the contact and oxidation with oxygen in the air are reduced, the cobalt element and the cerium element can be uniformly coated on the surface layer of the WC powder, and the uniformity of the powder can be effectively improved.
1. The invention firstly provides the method for preparing WC-Co-Ce alloy powder by using a chemical cladding method, and the method has great breakthrough in preparing materials of hard alloy. Different influencing factors (such as reaction time, reaction temperature, feed liquid concentration and the like) in the process of preparing the tungsten carbide-cobalt coarse-grain hard alloy powder by using a chemical coating method obtain a set of effective novel hard alloy powder preparation process.
2. The WC powder adopted by the invention adopts acid etching to carry out surface roughening, so that the contact area between the powder and the solution can be increased.
3. The chemical coating reaction is carried out under the acidic condition, so that Co element is effectively prevented from forming impurity substances (such as Co (OH)2) which are difficult to reduce under the alkaline condition, and incomplete coating of Co and Ce is avoided;
4. the chemical coating reaction of the invention adopts a spray-spray mode to add the reducing agent, thereby avoiding the generation of large-scale agglomerated particles of the coated particles.
5. Compared with the method for preparing the WC-Co-Ce composite powder, the method for preparing the WC-Co-Ce composite powder provided by the invention has the advantages that the structure of the coated Co is changed by adding the Ce, the coating uniformity is greatly improved, and the WC-Co-Ce composite powder which is uniformly dispersed is obtained.
6. The WC-Co-Ce composite powder is prepared by the method, Ce is uniformly coated on the surface layer of the WC powder, the agglomeration rate of the composite powder is reduced by adopting multiple means, and the dispersibility of rare earth elements is improved; the preparation method has high repeatability, and can ensure the stability of the product.
7. The hydrogen is adopted to reduce the cobalt salt and the rare earth salt to coat the particles, so that a part of coating layer in the form of Co-Ce alloy can be obtained, and the content of Ce oxide is reduced, thereby reducing the content of oxygen in the alloy and reducing the formation of harmful tissues; meanwhile, Ce in the Co-Ce alloy can absorb impurity elements in the alloy to form a strengthening phase structure, the strengthening phase structure and Co have good bonding strength, and the alloy performance can be effectively improved.
8. In the alloy material prepared by the invention, Co can well wet and wrap WC and rare earth; the invention has no special requirements on production equipment, only needs conventional equipment, and is beneficial to industrial popularization and application.
Drawings
FIG. 1(a) is a microscopic view of WC-Co-0.2% Ce composite powder;
FIG. 1(b) is a microscopic view of a WC-Co composite powder;
FIG. 1(c) is a high power WC-Co-0.2% Ce morphology and corresponding elemental scanning map.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
The present invention will be described in further detail with reference to the following embodiments, which are illustrative only and not limiting, and the scope of the present invention is not limited thereby.
The preparation method of the WC surface-coated Co powder added with the Ce element comprises the following steps:
(1) pretreating the surface of the tungsten carbide powder: grinding WC powder by using a mortar for 1-5 h, preparing a roughening solution, pouring the ground WC powder into the roughening solution, uniformly stirring, fully dispersing and roughening, filtering out the powder, washing and drying;
(2) preparing a composite powder precursor: dissolving soluble CoCl2And CeCl3Mixing the aqueous solutions to obtain a mixed solution; adding WC powder into the mixed solution to ensure that the surface of WC particles is fully contacted with the mixed solution, and then dropwise adding (NH)4)2C2O4Uniformly stirring the aqueous solution to perform a precipitation reaction, and drying after the precipitation reaction is finished to obtain a composite powder precursor;
the chemical reaction equation of the process is as follows:
CoCl2·6H2O+4(NH4)2C2O4·H2O+2CeCl3→CoC2O4·2H2O↓+Ce2(C2O4)3+8NH4Cl+5H2O
(3) reducing a composite powder precursor: the precursor of the composite powder is put in H2And sequentially carrying out reduction reaction in a protective atmosphere, and cooling to obtain the WC-Co-Ce composite powder.
The chemical reaction equation of the process is as follows:
2CoC2O4·2H2O+Ce2(C2O4)3+17H2→2Co+2Ce+CO2↑+3CO↑+17H2O。
the WC-Co-Ce composite powder prepared by the preparation method of the WC surface coated Co powder added with the Ce element mainly comprises the following components in percentage by weight:
co: 6% -12%, Ce: 0.2 to 0.6 percent, and the balance of WC.
Wherein the Fisher size of the WC powder is more than 5 μm, and the purity is 99.9%.
Several specific examples are given below:
example 1
Taking tungsten carbide powder with the average particle size of 4.95 microns and the purity of 99.9 percent, grinding the tungsten carbide powder for 2 hours, placing the tungsten carbide powder into 500mL of hydrofluoric acid-nitric acid mixed aqueous solution, and carrying out coarsening treatment under the condition of mechanical stirring, wherein the concentration of hydrofluoric acid is 30mL/L, the concentration of nitric acid is 30mL/L, the stirring time is 40min, the rotating speed is 300r/min, soaking the tungsten carbide powder for 20min after stirring, filtering the tungsten carbide powder by using a suction filter, washing the tungsten carbide powder for 3 times by using deionized water, and then placing the tungsten carbide powder into a drying box to be dried at the temperature of 60 ℃.
According to the mass percent, Ce is 0.2%, Co is 10%, WC is 89.8%, 1.82g CoCl2·6H2O and 0.016g CeCl3Dissolved in 50ml of an aqueous solution and sufficiently stirred. After completely dissolving, adding 4g of WC powder which is coarsened for the first time into the solution, carrying out ultrasonic treatment for 30min, standing for 2h, continuously stirring and uniformly mixing the solution at the temperature of 50 ℃ in a mechanical stirring manner, wherein the rotating speed is 300r/min, the stirring time is 20min, and then adding 1.95g of (NH)4)2C2O4·H2Dissolving O in 50ml of water solution, completely dissolving, and then adding CoCl after stirring uniformly2·6H2O、CeCl3And (NH) previously prepared by adding to the mixed solution of WC4)2C2O4Atomizing and spraying the aqueous solution for 5 minutes, and drying in a vacuum drying oven to obtain the WC-Co-Ce salt precursor mixture. Grinding and sieving the precursor, and then putting the precursor in a container H2Continuously calcining for 2h at 500 ℃ in the atmosphere, turning off a power supply, and cooling in the air to obtain the WC-Co-Ce composite powder.
From fig. 1, comparing the morphology of the composite powder after adding and not adding Ce rare earth, it can be seen from fig. 1(a) that Co/Ce particles in the coated powder are uniformly coated on the surface of WC particles in a dendritic form, wherein most of the Ce particles are coated by Co particles, and comparing fig. 1(b) that pure cobalt particles are in a strip shape, most of the length is longer than that of the WC particles, and most of the grains are exposed. Therefore, the uniformity of Co metal can be improved by adding rare earth Ce, and the morphology and uniformity change of the coated particles show that Ce and rare earth cooperate with Co to form a more uniform coating layer. Meanwhile, the WC-Co-Ce composite powder has the advantages of small apparent density, high chemical activity, good pressing performance and the like, and is favorable for further pressing and sintering.
Example 2
Taking tungsten carbide powder with the average particle size of 4.95 microns and the purity of 99.9%, grinding for 2 hours, placing the tungsten carbide powder into 500mL of hydrofluoric acid-nitric acid mixed aqueous solution, and roughening the tungsten carbide powder under the condition of mechanical stirring, wherein the concentration of hydrofluoric acid is 30mL/L, the concentration of nitric acid is 30mL/L, the stirring time is 40min, the rotating speed is 300r/min, soaking the tungsten carbide powder for 20min after stirring, filtering the WC powder which is ground and roughened by using a suction filter, washing the WC powder for 3 times by using deionized water, and then drying the WC powder in a drying oven at 60 ℃.
According to the mass percent of 0.4 percent of Ce, 10 percent of Co and 89.6 percent of WC, 1.82g of CoCl2·6H2O and 0.032g CeCl3Dissolved in 50ml of an aqueous solution and sufficiently stirred. After completely dissolving, adding 4g of WC powder which is coarsened for the first time into the solution, carrying out ultrasonic treatment for 30min, standing for 2h, continuously stirring and uniformly mixing the solution at the temperature of 50 ℃ in a mechanical stirring manner, wherein the rotating speed is 300r/min, the stirring time is 20min, and then adding 1.95g of (NH)4)2C2O4·H2Dissolving O in 50ml of water solution, completely dissolving, and then adding CoCl after stirring uniformly2·6H2O、CeCl3And (NH) previously prepared by adding to the mixed solution of WC4)2C2O4Atomizing and spraying the aqueous solution for 5 minutes, and drying in a vacuum drying oven to obtain the WC-Co-Ce salt precursor mixture. Grinding and sieving the composite powder precursor, and putting the powder precursor in a container H2Calcining at 500 deg.C for 2 hr, turning off power supply, and cooling in airTo obtain WC-Co-Ce composite powder.
Example 3
In order to compare the sintering performance and the mechanical performance of the WC-Co-Ce alloy prepared by the process with the mechanical mixing mode, tungsten carbide powder with the average particle size of 4.95 mu m and the purity of 99.9 percent and pure metal cobalt powder with the particle size of 1 mu m are taken, the two kinds of powder are prepared and then are respectively put into an agate mortar according to the mass ratio of 10wt percent of metal Co, meanwhile, absolute ethyl alcohol is added, wet grinding is carried out by a grinding pestle at a certain speed for 8 hours, and then drying is carried out in a vacuum drying oven for 2 hours to obtain WC-Co composite powder.
Example 4
Taking tungsten carbide powder with the average particle size of 4.95 microns and the purity of 99.9 percent, grinding the tungsten carbide powder for 2 hours, placing the tungsten carbide powder into 500mL of hydrofluoric acid-nitric acid mixed aqueous solution, and carrying out coarsening treatment under the condition of mechanical stirring, wherein the concentration of the hydrofluoric acid is 20mL/L, the concentration of the nitric acid is 20mL/L, the stirring time is 40min, the rotating speed is 300r/min, soaking the tungsten carbide powder for 20min after stirring, filtering the tungsten carbide powder by using a suction filter, washing the tungsten carbide powder for 3 times by using deionized water, and then placing the tungsten carbide powder into a drying box to be dried at the temperature of 60 ℃.
According to the mass percent of 0.6 percent of Ce, 10 percent of Co and 89.4 percent of WC, 1.82g of CoCl2·6H2O and 0.047g CeCl3Dissolved in 50ml of an aqueous solution and sufficiently stirred. After completely dissolving, adding 4g of WC powder which is coarsened for the first time into the solution, carrying out ultrasonic treatment for 30min, standing for 2h, continuously stirring and uniformly mixing the solution at the temperature of 50 ℃ in a mechanical stirring manner at the rotation speed of 300r/min for 20min, and adding 2.10g of (NH)4)2C2O4·H2Dissolving O in 50ml of water solution, completely dissolving, and then adding CoCl after stirring uniformly2·6H2O、CeCl3And (NH) previously prepared by adding to the mixed solution of WC4)2C2O4Atomizing and spraying the aqueous solution for 5 minutes, and drying in a vacuum drying oven to obtain the WC-Co-Ce salt precursor mixture. Grinding and sieving the precursor, and then putting the precursor in a container H2Continuously calcining for 2h at 500 ℃ in the atmosphere, turning off a power supply, and cooling in the air to obtain the WC-Co-Ce composite powder.
Example 5
Taking tungsten carbide powder with the average particle size of 4.95 microns and the purity of 99.9 percent, grinding the tungsten carbide powder for 2 hours, placing the tungsten carbide powder into 500mL of hydrofluoric acid-nitric acid mixed aqueous solution, and carrying out coarsening treatment under the condition of mechanical stirring, wherein the concentration of the hydrofluoric acid is 40mL/L, the concentration of the nitric acid is 40mL/L, the stirring time is 40min, the rotating speed is 300r/min, soaking the tungsten carbide powder for 20min after stirring, filtering the tungsten carbide powder by using a suction filter, washing the tungsten carbide powder for 3 times by using deionized water, and then placing the tungsten carbide powder into a drying box to be dried at the temperature of 60 ℃.
According to the mass percent, Ce is 0.3%, Co is 10%, WC is 89.7%, 1.82g CoCl2·6H2O and 0.024g CeCl3Dissolved in 50ml of an aqueous solution and sufficiently stirred. After completely dissolving, adding 4g of WC powder which is coarsened for the first time into the solution, carrying out ultrasonic treatment for 30min, standing for 2h, continuously stirring and uniformly mixing the solution at the temperature of 50 ℃ in a mechanical stirring manner, wherein the rotating speed is 300r/min, the stirring time is 20min, and then adding 1.95g of (NH)4)2C2O4·H2Dissolving O in 50ml of water solution, completely dissolving, and then adding CoCl after stirring uniformly2·6H2O、CeCl3And (NH) previously prepared by adding to the mixed solution of WC4)2C2O4Atomizing and spraying the aqueous solution for 5 minutes, and drying in a vacuum drying oven to obtain the WC-Co-Ce salt precursor mixture. Grinding and sieving the precursor, and then putting the precursor in a container H2Continuously calcining for 2h at 500 ℃ in the atmosphere, turning off a power supply, and cooling in the air to obtain the WC-Co-Ce composite powder.
The composite powder of the above example and the SD-E forming agent are mixed according to the proportion of 6 percent of the mass of the composite powder, and are granulated by a screen mesh and then are pressed into blanks, and the pressure of the press forming is 70 MPa. Placing the WC-Co-Ce composite powder compact into a vacuum sintering furnace for sintering and forming, wherein the furnace temperature is increased from room temperature to 200 ℃ at the speed of 2 ℃/min, preserving heat for 0.5h, then increased to 470 ℃ at the speed of 3 ℃/min, preserving heat for 1.5h, then increased to 900 ℃ at the speed of 6 ℃/min, preserving heat for 30min, then increased to 1250 ℃ at the speed of 8 ℃/min, preserving heat for 30min, finally increased to 1450 ℃ at the speed of 3 ℃/min, preserving heat for 1h, and then cooling to room temperature. And after the reaction is finished, closing the power supply, cooling to room temperature, and taking out the sample to obtain the WC-Co and WC-Co-Ce composite material hard alloy.
Then, the Rockwell hardness of the hard alloy is measured according to the GB/T3849.1-2015 standard by using a Rockwell hardness tester; calculating the density of the hard alloy according to GB/T3850-2015 standard test by a drainage method according to an Archimedes principle instrument; determining the impact toughness of the hard alloy by adopting a pendulum impact tester according to GB/T1817-2017; converting by using an electronic universal tester according to the test result of GB/T3851-2015 and combining a three-point test bending formula to obtain the bending strength of the hard alloy; the test results are shown in Table 1.
Table 1 cemented carbide test results
As can be seen from Table 1, under the condition of the same cobalt content, the density, Rockwell hardness, bending strength and impact toughness of the hard alloy prepared by the chemical coating method are all higher than those of the hard alloy prepared by the hand mixing process, which indicates that the chemical coating method is beneficial to improving the overall mechanical property of the hard alloy. Meanwhile, compared with the Hard alloy without the rare earth, the bending strength of the Hard alloy with the rare earth, which is prepared by the ball milling and mixing method at present, is improved by 180-300 MPa (Liu S. study on ray-earth processed Metals in China [ J ]. International Journal of reflective Metals and Hard Materials,2009,27(3): 528-Materials 534.), and the bending strength of the Hard alloy in the embodiments 1, 2, 4 and 5 is respectively improved by 307MPa, 358MPa, 390MPa and 421MPa, and the improvement effect is obviously better than that of the Hard alloy without the rare earth.
Claims (10)
1. A method for preparing WC surface-coated Co powder added with Ce element is characterized by comprising the following steps:
step 1: grinding and coarsening to form coarsened WC powder:
grinding WC powder for 1-5 h by adopting a mortar, and preparing components including HF and HNO3Pouring the grinded WC powder into the coarsening liquid, uniformly stirring, fully dispersing and coarsening, and thenFiltering out the coarsened WC powder, washing and drying;
step 2: preparing a composite powder precursor:
dissolving soluble CoCl2And CeCl3Mixing the aqueous solutions to obtain a mixed solution; adding the coarsened WC powder into the mixed solution to ensure that the surface of the WC particles is fully contacted with the mixed solution, and then dropwise adding (NH) in an atomization-spraying manner4)2C2O4Water solution, evenly stirring to carry out precipitation reaction, drying after the precipitation reaction is finished to obtain composite powder precursor powder, wherein the precipitation reaction equation is as follows:
CoCl2·6H2O+4(NH4)2C2O4·H2O+2CeCl3→CoC2O4·2H2O↓+Ce2(C2O4)3+8NH4Cl+5H2O
and step 3: reducing a composite powder precursor:
adding composite powder precursor powder in H2Carrying out reduction reaction in a protective atmosphere, and cooling to obtain WC-Co-Ce composite powder, wherein the reduction reaction equation is as follows:
2CoC2O4·2H2O+Ce2(C2O4)3+17H2→2Co+2Ce+CO2↑+3CO↑+17H2O。
2. the method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein the method comprises the following steps: step 1, the concentration of each component of the coarsening liquid is as follows: the concentration of HF is 20-40 mL/L, and HNO3The concentration of (A) is 20-40 mL/L; the volume of the roughening liquid for roughening the WC powder at the first time is 400-600 mL, the uniform stirring time is 20-40 min, and the obtained product is washed by ionized water for 3-5 times.
3. The method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein step 2 adopts an ultrasonic-standing mode to achieve the effect of full solid-liquid contact, the ultrasonic time is 10-30 min, and the standing time is 2-4 h.
4. The method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein during the reaction in step 2, the mixture is continuously stirred and mixed uniformly in a mechanical stirring mode, the rotating speed is 300-500 r/min, and the stirring time is 60-80 min; and after stopping stirring, standing the mixed solution for 20-30 minutes, and drying in a vacuum drying oven to obtain mixed powder precursor powder.
5. The method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein the method comprises the following steps: CoCl in step 22And (NH)4)2C2O4The molar ratio of (A) to (B) is 1: 1.6-2.0.
6. The method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein the method comprises the following steps: and 2, the precipitation reaction time is 1-2 h, and the precipitation reaction temperature is 50-60 ℃.
7. The method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein the precipitation reaction in step 2 is added in the following order: (NH)4)2C2O4The aqueous solution was slowly added to CoCl2And CeCl3In the mixed aqueous solution of (NH)4)2C2O4The aqueous solution is added by adopting a full-automatic atomizer atomization-spraying mode, and the atomization-spraying speed is 50 mL/min.
8. The method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein the pH value of the reaction solution in the step 2 is 4-7, and Co element is prevented from forming Co (OH) under alkaline condition2Preferentially precipitate out, and influence the generation of composite precipitates on the WC surface.
9. The method for preparing WC surface-coated Co powder added with Ce according to claim 1, wherein the composite powder precursor powder in step 3 is ground and separated into agglomerated particles before reduction reaction, and then sieved by a 200-mesh screen for 10-30 min.
10. The method for preparing WC surface-coated Co powder added with Ce element according to claim 1, wherein the temperature of the reduction reaction in step 3 is 500-800 ℃ and the time is 120-180 min.
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