CN114535588A

CN114535588A - Co/Ni Co-coated WC powder and preparation method thereof

Info

Publication number: CN114535588A
Application number: CN202210014740.5A
Authority: CN
Inventors: 徐文礼; 于淞百; 王义盛; 赵小鹏; 张建峰; 闵凡路; 刘凯; 李颜东; 王健; 崔士征
Original assignee: Hohai University HHU; CCCC Tunnel Engineering Co Ltd
Current assignee: Hohai University HHU; CCCC Tunnel Engineering Co Ltd
Priority date: 2022-01-07
Filing date: 2022-01-07
Publication date: 2022-05-27

Abstract

The invention discloses a Co/Ni Co-coated WC powder and a preparation method thereof, which comprises 3 steps of preparing coarsened WC powder, preparing a composite powder precursor and preparing the composite powder, wherein the invention adopts a coprecipitation-hydrogen reduction method to mix WC with Ni and Co, improves the agglomeration phenomenon of Ni in the traditional ball milling method, improves the wettability of bonding relative to WC by adding proper Co, is beneficial to discharging pores in the sintering process, reduces pores in the internal structure of the alloy, and inhibits the abnormal growth phenomenon of WC in a Ni bonding phase to a certain extent, thereby obtaining a WC-Ni/Co hard alloy material with high density, high strength and excellent corrosion resistance, the comprehensive performance of the WC-Ni/Co hard alloy material is obviously superior to that of the traditional WC-Ni hard alloy, and compared with a chemical plating method, the method has higher metal precipitation rate, no side reaction and no other components are introduced in the reaction process, the binder phase of the alloy is easily designed and the destruction of WC particles is reduced compared to the ball milling method.

Description

Co/Ni Co-coated WC powder and preparation method thereof

Technical Field

The invention relates to the technical field of powder metallurgy, in particular to Co/Ni Co-coated WC powder and a preparation method thereof.

Background

With the vigorous development of infrastructure construction and industrial production, the hard alloy is widely applied to the fields of tunnel engineering, coal field exploitation, stamping dies and the like by virtue of higher hardness, better toughness and excellent wear resistance. However, the conventional cemented carbide is subjected to long-term damage of load and abrasion in an actual working environment, so that the reliability of the conventional cemented carbide is reduced. With the increase of the application range and the increase of the service life of the tool material, the oxidation corrosion and the chemical corrosion caused by long-term work also become important reasons for replacing the hard alloy, not only the maintenance and updating cost of a processing machine is increased, but also unknown safety accidents can be caused, and the Co is favorable for improving the strength and the hardness of the hard alloy due to the excellent wettability of the Co on the hard phase, so that the WC-Co hard alloy has a leading position in various fields, but at present, the price of the cobalt which is a strategic scarce resource is expensive and rises year by year, and the tungsten carbide hard alloy (WC-Ni) taking the nickel as a main binder has the advantages of good corrosion resistance and high oxidation resistance and is lower in price compared with the cobalt, thereby receiving wide attention of people.

Although scientists at home and abroad have already carried out certain research on WC-Ni hard alloy, because of different bonding strengthening degrees of Ni and Co to hard phases, the WC-Ni hard alloy is lower than WC-Co hard alloy in some mechanical properties, aiming at the problems, researchers have optimized sintering process or added with a plurality of alloy elements and additives to strengthen the performance of the sintered alloy, the invention patent 'a preparation method of Ni bonding WC-based hard alloy' (application No. 200810046452.8) adopts a method combining vacuum quenching and deep cooling treatment to improve the uniformity of the structure after sintering and forming, but the subsequent procedures are complicated and other mechanical properties are not tested except the improvement of the hardness; the invention relates to a preparation method of a high-toughness WC-Fe-Ni hard alloy (application No. 202010781298.X), which takes Fe and Ni as binding phases, applies dynamic vibration pressure in the sintering process, obviously improves the hardness and fracture toughness, but does not obviously inhibit the phenomenon of abnormal growth of crystal grains from the microstructure; the invention discloses a chromium-containing WC-9Ni hard alloy (application No. 201710948765.1), which is added with an additive Cr to inhibit the dissolution, re-precipitation and growth of WC grains in the WC-9Ni hard alloy and refine the WC grains, thereby improving the hardness and the wear resistance.

The above patents still adopt the ball milling method to mix the alloy powder, but the ball milling method can cause the agglomeration of Ni powder when mixing WC and Ni powder, which is not beneficial to the uniform flow of the binding phase between WC in the sintering process, thereby resulting in poor alloy compactness, and simultaneously along with the phenomenon of abnormal growth of crystal grains, the mechanical property is poor, the ball milling process causes the distortion of WC grains, especially the crystal lattices of coarse crystal WC, and the powder granularity is difficult to control.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide Co/Ni Co-coated WC powder and a preparation method thereof, and solve the technical problem of poor mechanical property of the traditional hard alloy material.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of Co/Ni Co-coated WC powder comprises the following steps:

(1) preparation of coarsened WC powder: adding WC powder to HF andHNO₃mechanically stirring the mixture in the mixed acid, filtering, washing and drying the mixture after stirring to obtain coarsened WC powder;

(2) preparing a composite powder precursor: adding nickel salt and cobalt salt into deionized water to prepare Ni²⁺/Co²⁺Adjusting the pH value of the metal ion solution to 4-7, adding the coarsened WC powder obtained in the step (1), uniformly mixing, and dropwise adding (NH) in an atomization-spraying manner under the condition of stirring₄)₂C₂O₄Reacting the aqueous solution, standing, washing and drying after the reaction is finished to obtain a composite powder precursor;

(3) preparing composite powder: h, adding the composite powder precursor powder obtained in the step (2) into the mixture₂Carrying out reduction reaction in protective atmosphere, and cooling after the reaction is finished to obtain the WC-Ni/Co composite powder.

Preferably, in the step (1), the mass volume ratio of the WC powder to the mixed acid is 10g:400-600 ml.

Preferably, in step (1), HF and HNO₃The concentration of (A) is 20-40 ml/L.

Preferably, in step (1), the mechanical stirring time is 20-40 min.

Preferably, in the step (2), the nickel salt is NiCl₂·6H₂O, the addition amount is 2.4-3.7g, and the cobalt salt is CoCl₂·6H₂O, the addition amount is 1.05-1.8g, and the addition amount of the coarsened WC powder is 10 g.

Preferably, in step (2), (NH)₄)₂C₂O₄The concentration of the aqueous solution is 0.3-0.5mol/L, (NH)₄)₂C₂O₄The addition amount is 3-4 g.

Preferably, in the step (2), the stirring speed is 200-500 r/min.

Preferably, in the step (2), the reaction temperature is 50-60 ℃ and the reaction time is 60-80 min.

Preferably, in the step (3), the reaction temperature is 500-700 ℃, and the reaction time is 30-60 min.

The invention also provides Co/Ni Co-coated WC powder prepared by the preparation method, which consists of the following components in percentage by mass: the hard phase is WC with the mass fraction of 85-95%, the balance is a binder phase, and the binder phase is Ni and Co.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides Co/Ni Co-coated WC powder and a preparation method thereof, the invention firstly provides a method for preparing WC-Ni/Co alloy powder by using a coprecipitation-hydrogen reduction method, the method has great breakthrough in hard alloy preparation materials, and the reaction equation is as follows:

NiCl₂·6H₂O+(NH₄)₂C₂O₄·H₂O→NiC₂O₄·2H₂o ↓ (WC surface) +2NH₄Cl+5H₂O

CoCl₂·6H₂O+(NH₄)₂C₂O₄·H₂O→CoC₂O₄·2H₂O ↓ (WC surface) +2NH₄Cl+5H₂O

2NiC₂O₄·2H₂O+5H₂→ 2Ni (WC surface) + CO₂↑+3CO↑+17H₂O

2CoC₂O₄·2H₂O+5H₂→ 2Co (WC surface) + CO₂↑+3CO↑+17H₂O

(2) The invention provides Co/Ni Co-coated WC powder and a preparation method thereof, wherein the powder coating is carried out by adopting a coprecipitation-hydrogen reduction method, compared with a chemical plating method, the method has higher metal precipitation rate, has no side reaction in the reaction process, does not introduce other components, is easy to design a binding phase of an alloy, and can reduce the damage to WC particles compared with a ball milling method.

(3) The invention provides Co/Ni Co-coated WC powder and a preparation method thereof, wherein a coprecipitation-hydrogen reduction method is adopted for mixing WC, Ni and Co, the agglomeration phenomenon of Ni in the traditional ball milling method is improved, the wettability of bonding relative to WC is improved by adding proper Co, the discharge of pores in the sintering process is facilitated, pores in the internal structure of the alloy are reduced, and the abnormal growth phenomenon of WC in a Ni bonding phase is inhibited to a certain extent, so that a WC-Ni/Co hard alloy material with high density, high strength and excellent corrosion resistance can be obtained, and the comprehensive performance of the WC-Ni/Co hard alloy material is obviously superior to that of the traditional WC-Ni hard alloy.

(4) The invention provides Co/Ni Co-coated WC powder and a preparation method thereof, which lay theoretical and technical foundation for promoting low-cost tungsten carbide hard alloy with Co/Ni as a binder phase, have no special requirement on production equipment, only need conventional equipment, and are beneficial to industrial popularization and application.

Drawings

FIG. 1 is (a) WC base powder; (b) a WC-Ni/Co composite powder precursor; (c) schematic diagram of WC-Ni/Co composite powder.

Detailed Description

The present invention will be described in more detail with reference to specific preferred embodiments, but the present invention is not limited to the following embodiments.

It should be noted that, unless otherwise specified, the chemical reagents involved in the present invention are commercially available.

In this example, the Fisher size of the WC powder is larger than 5 μm, and the purity is 99.9%.

Example 1

(1) preparation of coarsened WC powder: taking 10g of tungsten carbide powder with the average particle size of 5.2 mu m and the purity of 99.9 percent, grinding the tungsten carbide powder, putting the ground tungsten carbide powder into 500mL of hydrofluoric acid-nitric acid mixed acid solution, wherein the concentration of hydrofluoric acid is 30mL/L, the volume of hydrofluoric acid is 250mL, the concentration of nitric acid is 30mL/L and the volume of nitric acid is 250mL, carrying out coarsening treatment under the condition of mechanical stirring at the rotating speed of 300r/min for 30min, standing the mixture for 10min after stirring, filtering the powder, washing the powder for 3 times by deionized water, and then putting the powder into a 60 ℃ oven for drying to obtain coarsened WC powder;

(2) preparing a composite powder precursor: 2.70g of NiCl₂·6H₂O and 1.35g CoCl₂·6H₂Dissolving O in 50ml of aqueous solution to prepare Ni²⁺/Co²⁺Uniformly mixing the solution, adjusting the pH value of the solution to be 5, adding 10g of coarsened WC powder, and performing ultrasonic treatment for 10min to obtain waterKeeping the bath temperature at 50 ℃, mixing evenly, and adding 3.4g (NH)₄)₂C₂O₄Adding a precipitator which is prepared into deionized water to be 0.3mol/L, and atomizing and spraying (NH)₄)₂C₂O₄Adding the aqueous solution into a WC solution for reaction at the stirring speed of 300r/min and the reaction temperature of 50 ℃ for 60min, standing for 10min after the reaction is finished, and then washing and drying to obtain composite powder precursor powder;

(3) preparing composite powder: grinding and sieving the composite powder precursor powder, and putting the powder in a container H₂Continuously calcining for 30min at 500 ℃ in the atmosphere, and then cooling to room temperature to obtain WC-Ni/Co composite powder.

FIG. 1(a) shows WC raw powder, and FIG. 1(b) shows Ni as a coating layer_0.75Co_0.25C₂O₄·2H₂The composite powder precursor powder of O can be seen to be a blocky or platelet-shaped accumulation body, the coating is tight, the powder is dispersed very uniformly, the diagram (c) of figure 1 is WC-Ni/Co composite powder, the product is coated on the surface of WC due to coprecipitation reaction, and the reduced binding phase continuously and smoothly covers the surface of WC particles, thereby being beneficial to further pressing and sintering.

Example 2

(2) preparing a composite powder precursor: mixing 3.70NiCl₂·6H₂O and 1.05CoCl₂·6H₂Dissolving O in 50ml of aqueous solution to prepare Ni²⁺/Co²⁺Solution and mixing are carried outMixing, adjusting pH of the solution to 5, adding 10g of coarsened WC powder, performing ultrasonic treatment for 10min, maintaining the temperature in water bath at 50 deg.C, mixing well, and adding 3.4g (NH)₄)₂C₂O₄Adding a precipitator which is prepared into deionized water to be 0.4mol/L, and atomizing and spraying (NH)₄)₂C₂O₄Adding the aqueous solution into a WC solution for reaction at a stirring speed of 300r/min and a reaction temperature of 50 ℃ for 60min, standing for 10min after the reaction is finished, and then washing and drying to obtain composite powder precursor powder;

Example 3

(1) preparing coarsened WC powder: taking 10g of tungsten carbide powder with the average particle size of 5.2 mu m and the purity of 99.9 percent, grinding the tungsten carbide powder, putting the ground tungsten carbide powder into 500mL of hydrofluoric acid-nitric acid mixed acid solution, wherein the concentration of hydrofluoric acid is 30mL/L, the volume of hydrofluoric acid is 250mL, the concentration of nitric acid is 30mL/L and the volume of nitric acid is 250mL, carrying out coarsening treatment under the condition of mechanical stirring at the rotating speed of 300r/min for 30min, standing the mixture for 10min after stirring, filtering the powder, washing the powder for 3 times by deionized water, and then putting the powder into a 60 ℃ oven for drying to obtain coarsened WC powder;

(2) preparing a composite powder precursor: 2.4g of NiCl₂·6H₂O and 1.20gCoCl₂·6H₂Dissolving O in 50ml of aqueous solution to prepare Ni²⁺/Co²⁺Mixing the solution uniformly, adjusting pH of the solution to 5, adding 10g of coarsened WC powder, performing ultrasonic treatment for 10min, keeping the temperature of the water bath at 50 ℃, mixing uniformly, and adding 3.4 (NH)₄)₂C₂O₄Adding a precipitator which is prepared into deionized water to be 0.5mol/L, and atomizing and spraying (NH)₄)₂C₂O₄Adding the aqueous solution into WC solution for reaction at a stirring speed of 300r/min and a reaction temperature of 50 ℃ for 60min, standing for 10min after the reaction is finished, and then washing and drying to obtain composite powder precursor powder;

Example 4

(2) preparing a composite powder precursor: mixing 2.7NiCl₂·6H₂O and 1.8gCoCl₂·6H₂Dissolving O in 50ml of aqueous solution to prepare Ni²⁺/Co²⁺Mixing the solution uniformly, adjusting pH of the solution to 5, adding 10g of coarsened WC powder, performing ultrasonic treatment for 10min, keeping the temperature of the water bath at 50 ℃, mixing uniformly, and adding 3.4g of (NH)₄)₂C₂O₄Adding a precipitator which is prepared into deionized water to be 0.5mol/L, and atomizing and spraying (NH)₄)₂C₂O₄Adding the aqueous solution into a WC solution for reaction at the stirring speed of 300r/min and the reaction temperature of 50 ℃ for 60min, standing for 10min after the reaction is finished, and then washing and drying to obtain composite powder precursor powder;

Comparative example 1

A preparation method of Ni-coated WC powder comprises the following steps:

(2) preparing a composite powder precursor: 4.05g of NiCl₂·6H₂Dissolving O in 50ml water solution to obtain solution, adjusting pH to 5, adding 10g of coarsened WC powder, performing ultrasonic treatment for 10min, maintaining temperature in water bath at 50 deg.C, mixing, and adding 3.4g (NH)₄)₂C₂O₄Adding 0.4mol/L precipitator into deionized water, and atomizing and spraying (NH)₄)₂C₂O₄Adding the aqueous solution into a WC solution for reaction at the stirring speed of 300r/min and the reaction temperature of 50 ℃ for 60min, standing for 10min after the reaction is finished, and then washing and drying to obtain composite powder precursor powder;

(3) preparing composite powder: grinding and sieving the composite powder precursor powder, and putting the powder in a container H₂Continuously calcining for 30min at 500 ℃ in the atmosphere, and then cooling to room temperature to obtain the WC-Ni composite powder.

The composite powders prepared in examples 1-4 and comparative example 1 were prepared into cemented carbide respectively, and the specific steps were as follows: mixing the composite powder with 5 wt% of polyvinyl alcohol aqueous solution, placing the mixed powder in a drying oven, drying, granulating by using a 200-mesh screen, then pressing into a blank, wherein the pressure for press forming is 150MPa, placing the composite powder blank in a vacuum sintering furnace for sintering and forming, raising the furnace temperature from room temperature to 240 ℃ at the speed of 4 ℃/min, preserving heat for 1h, raising the temperature to 500 ℃ at the speed of 4 ℃/min, preserving heat for 2h, raising the temperature to 950 ℃ at the speed of 8 ℃/min, preserving heat for 60min, raising the temperature to 1300 ℃ at the speed of 10 ℃/min, preserving heat for 60min, finally raising the temperature to 1450 ℃ at the speed of 3 ℃/min, preserving heat for 1h, cooling to room temperature, and taking out a sample to obtain the hard alloy composite material.

Calculating the density of the hard alloy according to GB/T3850-2015 standard test by using a drainage method and an Archimedes principle instrument; then, the Rockwell hardness of the hard alloy is measured by a Rockwell hardness tester according to the GB/T3849.1-2015 standard; determining the impact toughness of the hard alloy according to GB/T1817-2017 by adopting a pendulum impact tester; converting by using an electronic universal testing machine according to GB/T3851-2015 test results and combining a three-point test bending formula to obtain the bending strength of the hard alloy; the corrosion resistance of the hard alloy is obtained by electrochemical test, and the test result is shown in the following table:

as can be seen from the table, the introduction of Co into the system with Ni as the binder phase can improve the internal structure and mechanical properties of the hard alloy, compared with the hard alloy with pure Ni as the binder phase, the purity of the composite powder binder phase prepared by adopting the coprecipitation-high temperature reduction method is good, the WC-Ni/Co hard alloy has greatly improved relative density, Rockwell hardness, impact toughness and bending strength, the hard alloy with Ni as the binder phase generally has better corrosion resistance, and the simulation resistance value can maintain 5 multiplied by 10⁵And omega is about, which proves that the WC-Ni/Co prepared by coprecipitation-hydrogen reduction still keeps higher corrosion resistance while improving the mechanical property.

Finally, it is to be noted that: the above examples do not limit the invention in any way. It will be apparent to those skilled in the art that various modifications and improvements can be made to the present invention. Accordingly, any modification or improvement made without departing from the spirit of the present invention shall fall within the scope of the claims of the present invention.

Claims

1. A preparation method of Co/Ni Co-coated WC powder is characterized by comprising the following steps:

(1) preparation of coarsened WC powder: adding WC powder to HF and HNO₃Mechanically stirring in the mixed acid, filtering, washing and drying after stirring to obtain coarsened WC powder;

(2) preparing a composite powder precursor: adding nickel salt and cobalt salt into deionized water to prepare Ni^2＋/Co²⁺Adjusting the pH value of the metal ion solution to 4-7, adding the coarsened WC powder obtained in the step (1), uniformly mixing, and dropwise adding (NH) in an atomization-spraying manner under the condition of stirring₄)₂C₂O₄Reacting the aqueous solution, standing, washing and drying after the reaction is finished to obtain a composite powder precursor;

2. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (1), the mass-to-volume ratio of WC powder to mixed acid is 10g:400-600 ml.

3. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (1), HF and HNO₃The concentration of (A) is 20-40 ml/L.

4. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (1), the mechanical stirring time is 20-40 min.

5. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (2), the nickel salt is NiCl₂·6H₂O, the addition amount is 2.4-3.7g, and the cobalt salt is CoCl₂·6H₂O, the addition amount is 1.05-1.8g, and the addition amount of the coarsened WC powder is 10 g.

6. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (2), (NH)₄)₂C₂O₄The concentration of the aqueous solution is 0.3-0.5mol/L, (NH)₄)₂C₂O₄The addition amount is 3-4 g.

7. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (2), the stirring speed is 200-500 r/min.

8. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (2), the reaction temperature is 50-60 ℃ and the reaction time is 60-80 min.

9. The method for preparing Co/Ni Co-coated WC powder of claim 1, wherein in step (3), the reaction temperature is 500-700 ℃ and the reaction time is 30-60 min.

10. The Co/Ni Co-coated WC powder prepared by the preparation method according to any one of claims 1 to 9, which is characterized by comprising the following components in percentage by mass: the hard phase is WC with the mass fraction of 85-95%, and the balance is a binder phase which is Ni and Co.