Tungsten Carbide Button — Ultra-fine Crystallization and Gradient Optimization

Tungsten carbide button is a kind of rock drilling tools composed of hard phase WC and binder phase Co and has high hardness, high strength, high wear resistance and good impact toughness. Compared similar products with other materials, it has higher drilling speed, extends the service life 5 – 6 times, which not only saves time, improves the efficiency, but also reduces the frequency of changing buttons and manual labor.

With the increasing complexity of environmental conditions, drilling of drill performance requirements are also increasing, especially the button used for high-pressure drilling not only high hardness and wear resistance, but also need good toughness to prevent brittle fracture. The fine grain structure can effectively improve the performance of the alloy, studies have shown that ultrafine-grained and nano-structured carbide button binder phase content in the same case, when the WC grain size of less than 1μm, the hardness and strength can be greatly improved, and with the further reduction in WC grain size, the performance increase rate is more significant. Although nano grain is small in size, it has larger specific surface area, higher surface activity. So it has some excellent properties of nanostructures, such as lowering the sintering temperature required to increase the hardness, strength, wear resistance and impact toughness of mono button, life extension and so on, is one of the hotspots carbide materials currently.

Gradient carbide is a kind of multi-phase structured carbide that developed in the end of 1980s. The most outstanding characteristic is the gradient component and distribution. The preparation principle gradient structure of cemented carbide is obtained using low-carbon carbide alloy containing η phase by vacuum sintering, and treated to alter the distribution of Co binder phase of different parts of button distributed in different carburizing atmosphere Co content. As a result the organizational structure of tungsten carbide button shows gradient distribution of Co, the outer layer – Co-depleted layer, the intermediate layer – Co-rich layer, the inner layer – WC, Co, η three phases microstructure. The outer layer due to the high content of WC has good wear resistance; the intermediate layer has higher content of Co, so the toughness is better.

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