New Low-cobalt Tungsten Carbide Composite Material

Tungsten carbide (WC) is an important type of cemented carbide. It is widely used in modern tool materials, wear-resistant, corrosion-resistant and high-temperature resistant materials. It is known as the teeth of modern industry.

In the process of sintering cemented carbide, pure WC material is difficult to be sintered and compacted. Even if the sintering is dense, the sintering temperature is often above 2000 °C. Such a high sintering temperature is also a damage to the equipment itself, and the fracture toughness after sintering is insufficient. Cobalt (Co) as a binder phase in WC sintering, WC has very good wettability, and can reduce the sintering temperature of WC to 1400 °C. When sintering, Co becomes liquid phase, greatly increasing the diffusion rate of WC particles and making the sintering dense.  After sintering, the tungsten carbide composite usually has a fracture toughness of 12 MPa•m1/2.

However, China's cobalt resources are extremely scarce, the international cobalt price is very strong, and there are many unstable factors in the supply of Co raw materials.  At the same time, Co as a binder reduces the hardness, corrosion resistance and high temperature resistance of WC materials, and limits the application of WC materials in some extreme service environments. Therefore, it is very important to find a common source of materials that does not form a binder phase in WC instead of Co.

At present, in the study of unbonded phase WC materials, the addition of ceramic phase is an idea. Some researchers have proposed a preparation method of a new low-cobalt content tungsten carbide composite material, and a new material is selected instead of Co to prepare high strength, high wear resistance, low adhesion tungsten carbide composite, the process includes:

1. Mix WC powder and tungsten powder in proportion and heat to 500-600 ° C for 15-20 min to decarburize the surface of tungsten carbide to form a mixture of tungsten and tungsten oxide, then pass argon reduction and heat to 650.  750 ° C, holding 10-20 min, to obtain a composite powder of tungsten and tungsten carbide;

2. After weighing Al2O3, ZrO2, cobalt and cerium oxide, add the composite powder described in step a, add 100-150 parts of ethanol or water, and mix the ball mill for 15-30 minutes to form a mixed slurry ;

3. The mixed slurry is dried to a moisture or ethanol amount of ≤ 1%, and is sintered in a sintering furnace at a sintering temperature of 1400-1500 ° C, a pressure of 40-50 MPa, and a holding time of 10-15 min;

In the new low-cobalt content tungsten carbide composite material, tungsten carbide is used as the main raw material, and the ceramic materials Al2O3 and ZrO2 are used together to form a stable three-phase structure, and the structure is dense, which enhances the wear resistance of the composite material and does not affect  The hardness of the tungsten carbide material itself.  At the same time, metal materials such as cobalt, cerium oxide and tungsten powder are added, and a certain amount of molybdenum powder can be added to enhance the high temperature resistance and oxidation resistance of the composite material, and the prepared composite material has high temperature resistance and wear resistance. Strong, reducing the amount of cobalt, and avoiding the formation of a binder phase, the structure is more stable.

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