CN1210203C - Preparation of tungsten carbide powder - Google Patents

Abstract

The invention discloses a method for preparing tungsten carbide powder. Firstly, put the raw material powder of W 50at% with purity >99% and C 50at% with purity >99% into a ball mill, and vacuumize to 10 ^-2 to 10 ^-4 Pa, and filled with argon protection, the pressure is kept in the range of 1.0 to 1.5 atm (1 atm = 101325Pa), and ball milled at room temperature; then the powder obtained by ball milling is decomposed under the protection of argon at a temperature of 700 ° C to 900 ° C. After heat treatment in the furnace. The present invention can control the ball milling time to obtain powders with different particle sizes, it only involves the reaction between W and C two phases, and it is carried out under a protective atmosphere, and the product has high purity; the annealing temperature is much lower than the conventional preparation temperature, which reduces energy consumption and inhibits crystallization. grain growth; the production process is simple and does not require complex equipment, and the existing process can be improved to produce qualified products, which is conducive to popularization and application.

Description

A method for preparing tungsten carbide powder

Technical field

The invention relates to a method for preparing tungsten carbide (WC) powder.

Background technique

Transition metal carbides have the advantages of high melting point, high hardness, high wear resistance and good high temperature oxidation resistance, and stable chemical properties, and are widely used in industrial production, especially tungsten carbide has good comprehensive properties. The most important material for making drawing dies, cutting tools, wear-resistant coatings and metal matrix composite reinforcements, etc.

At present, the commonly used methods for preparing tungsten carbide are as follows:

(1) Using elemental metal W to react directly with stone mill powder or carbon black (C) at high temperature (~1400°C), the basic principle is:

      

(2) Utilize metal oxide of tungsten to react with stone mill or carbon black:

       

Both of the above two methods can obtain tungsten carbide powder, but the reaction is required to be carried out at high temperature, and a high-temperature industrial furnace is required, which not only has high equipment cost, but also consumes a lot of energy and time. In addition, there are impurity phases in the powder, and the particle size of the product is not easy to control.

(3) Self-propagating high-temperature synthesis (SHS) also uses the following reactions to prepare tungsten carbide:

       

This method is to ignite the mixture of metal W and carbon in a certain atmosphere (protective gas such as N ₂ , Ar, etc.) , so that the reaction continues without the supply of external heat, so the synthesis reaction spreads to the entire reactant body in the form of a combustion wave, and the reactants are transformed into products during the forward movement of the combustion wave. However, this method also needs to be ignited at high temperature, and the reaction process is uncontrollable.

The above-mentioned methods are all high-temperature reactions, and most of the synthesized tungsten carbides are in the form of blocks, which need to be further dispersed and ground to obtain alloy powders that meet the size and composition requirements.

(4) Mechanical alloying method (MA), which is a new method of preparing tungsten carbide and other materials, by ball milling solid powder containing W (generally pure tungsten powder or WO ₃ powder) and stone mill or carbon black Powder, tungsten carbide powder can be obtained at room temperature. The basic principle of the reaction applied in this method is the same as the previous method, namely

;or

The advantage of this method is that it does not require high-temperature equipment and can greatly reduce energy consumption. However, the ball milling time is usually very long, generally more than 100 hours, so the productivity is relatively low.

Contents of Invention

The purpose of the present invention is to provide a method for preparing tungsten carbide powder. First, the mixed powder of W and C is ball milled to obtain a metastable solid solution phase, and then the solid solution is annealed at a temperature much lower than that of conventional methods. Obtain tungsten carbide powder.

The technical scheme that the present invention adopts comprises following two steps:

1) Ball milling process: first put the raw material powder of W 50at% with a purity >99% and C50at% with a purity >99% into a planetary high-energy ball mill, vacuumize to 10 ^-2 ~ 10 ^-4 Pa, and fill it with argon Gas protection, the pressure is kept in the range of 1.0-1.5atm (1atm=1.0×10 ⁵ Pa); then the raw materials are reacted in a planetary ball mill with a rotation speed of 100-350r/min, and the ball-to-material ratio is selected as 10:1-30:1 , the reaction temperature is room temperature, after 4 ~ 30h of ball milling.

2) Annealing process: The powder obtained by ball milling is heat-treated in an argon-protected annealing furnace at a temperature of 700°C to 900°C for 1 to 2 hours, and the tungsten carbide powder that meets the requirements can be prepared.

The advantages of the present invention are: (1) The particle size and composition of the tungsten carbide powder can be controlled, powders with different particle sizes can be obtained under different ball milling times, and the crystal grains of the obtained powder can be refined to the nanometer level (10-100nm). In addition, this method only involves the two-phase reaction of W and C, and under a protective atmosphere, the introduction of impurities and the generation of oxides can be avoided, so the purity of the product is high; Improve the preparation efficiency of the product, and reduce the wear of the ball milling tool, and reduce the chance of introducing impurities; (3) the temperature of the annealing treatment is far lower than the preparation temperature in the conventional method, which is helpful for reducing energy consumption and inhibiting grain growth. (4) The production process is simple, the process is mature, and does not require complicated equipment, and the investment is small. Only the existing process can be improved to produce qualified products, which is conducive to popularization and application.

Description of drawings

Figure 1 is the XRD analysis results of W ₅₀ C ₅₀ at different ball milling stages;

Fig. 2 is the XRD analysis result of the ball milled product after annealing treatment.

Detailed ways

Example 1:

First, put W 50at% with a purity of >99% and C50at% with a purity >99% in accordance with the WC stoichiometric ratio into a planetary high-energy ball mill, vacuumize to 10 ^-2 Pa, and fill with argon at 1.2 atm (1 atm =101325Pa); then the mixed powder reacts in a planetary ball mill with a rotational speed of 300r/min, and ball mills for 4h. Take out the ball-milled product and treat it in an annealing furnace at 900°C for 1 hour under the protection of argon to obtain tungsten carbide powder. The X-ray analysis results of the ball milled product and the annealed product are shown in Figure 1 and Figure 2 respectively. It can be seen that there are no other impurity phases in the product, and the obtained tungsten carbide powder is of high purity.

Example 2:

Put the mixed powder of W 50at% with a purity >99% and C 50at% with a purity >99% into a planetary ball mill, evacuate to 10 ^-2 Pa, and fill with argon at 1.2 atm; then the mixed powder is rotated at 300r/min React in a planetary ball mill, and ball mill for 28 hours. Take out the ball-milled product and treat it in an annealing furnace at 700°C for 1 hour under the protection of argon to obtain tungsten carbide powder. The X-ray analysis results of the ball milled product and the annealed product are shown in Figure 1 and Figure 2 respectively. It can be seen that there are no other impurity phases in the product, and what is obtained is tungsten carbide powder with high purity (>98%).

Claims (1)

1. A method for preparing tungsten carbide powder is characterized in that it comprises the following two steps: 1) Ball milling process: first put the raw material powder of W 50at% with a purity >99% and C 50at% with a purity >99% into a planetary high-energy ball mill, vacuumize to 10 ^-2 ~ 10 ^-4 Pa, and fill it with Protected by argon, the pressure is kept at 1.0-1.5 atm; then the raw materials are reacted in a planetary ball mill with a rotational speed of 100-350r/min, the ball-material ratio is selected as 10:1-30:1, the reaction temperature is room temperature, and after 4-30h ball mill; 2) Annealing process: The powder obtained by ball milling is heat-treated in an argon-protected annealing furnace at a temperature of 700°C to 900°C for 1 to 2 hours to prepare tungsten carbide powder.

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