High Toughness Super Coarse Crystalline Cemented Carbide Made from Tungsten Carbide

With the continuous development of cemented carbide industry, the demand for tungsten carbide is increasing. The tungsten carbide powder prepared by the traditional method has a high aggregation degree, which is liable to cause the larger average particle size and the smaller particle size. As a result, the difficulty in manufacturing high-quality cemented carbide is increased, making it difficult for the cemented carbide products to achieve a high degree of uniformity in wear resistance and toughness.

A method of preparing high toughness super coarse crystalline cemented carbide is proposed. The process steps are as follows: mixing, wet grinding, drying, prefiring, wet mixing, drying, forming agent, granulating, pressing molding and vacuum low pressure integrated sintering. Examples are as follows:

(1) With cobalt powder and tungsten carbide powder, the mass ratio of cobalt powder and tungsten carbide powder is 2.5: 97.5, and tungsten carbide powders with Fsss grain size of 17.2 ~ 18 μm tungsten carbide powder, the particle size of cobalt powder is 1.4 ~ 2 μm.

(2) The wet mill is ball milling, the ball milling medium is acetone, the ratio of the ball is 3: 1, the ratio of solid to liquid is 5: 1, the wet milling time is 10 hours. After wet grinding, the mixture is dried and the mixture is prefired after the drying. The pre firing treatment is 700°C after 3 hours, and then the heat preservation is 55~65 minutes.

(3) When the prefired mixture is added to the metal cobalt powder and Co₂W₄C nanoparticles, the ratio of cobalt powder to the mass of cobalt and tungsten carbide in the mixture is 11.5: 88.5, and the ratio of Co₂W₄C nanoparticles to the mass ratio of cobalt and Co₂W₄C nanoparticles in the mixture is 1: 0.052 and heated to 58~62°C. The maximum temperature of the vacuum and low pressure integrated sintering is 1450°C by drying, adding forming agent, granulating, pressing forming and vacuum low pressure integrated sintering for 4 hours.

100 samples of high toughness super coarse tungsten cobalt tungsten carbide (the standard product of shape 6.5*5.25*20 μm) were tested. The average grain size of WC was 5.2 μm, the average bending strength was 3400MPa, and the average hardness was HRA88.5. It can be seen from the data that the improved method has achieved a good match between strength and microhardness, thus greatly improving the comprehensive properties of the alloy. 

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