Gradient Tungsten Carbide Button Process

At present, the main process of tungsten carbide button with gradient structure includes compound hard metal technique, powder layering compression (with different binder content), metal melt impregnation and so on. Compared with these processes, the lack of carbon carbide carburizing treatment method has many advantages, such as better wear resistance and toughness; according to different needs to use different combinations in different parts of the process flexibility and breadth of application have been greatly improved; equipment is simple, easy to operate, relatively low cost.

Carbide composite method uses cemented carbide powder with different particle sizes or particle size distribution is divided into regions having different cemented carbide and use, which can achieve different binder phase content in the cemented carbide sintered body interior. However, such fine-grained portion having higher binder phase content than the coarse-grained portion, there is a small difference in the wear resistance and toughness of different parts; use layered pressed powder (with different content of binder), you need to use a different focus on the binder content of cemented carbide powder was pressed layer by layer. As a result, not only complex process operation, and during sintering compacts easily generated between the different layers of binder content homogenized, so that differences in wear resistance and toughness of the alloy between the different parts are gradually narrowing; The molten metal impregnation method requires special equipment and the need to prepare the metal melt impregnation, and the gradient structure fabricated is limited to the surface area so the range of applications has been greatly limited.

The lack of carbon carbide carburizing treatment, is (the lack of carbon or low carbon) is generated in the carbide structure after sintering carbide mixing at a carbon content below stoichiometric conditions missing carbon phase -η phase. Whether or relative lack of free carbon-carbon phase will have a negative effect on the carbide products. Since η phase is too brittle to form micro-cracks on the surface easily, which causes the fracture of tungsten carbide in the process of using. For the drills with tungsten carbide button, the wear resistance is the primary factor. Tungsten carbide with low content of Co is difficult to be welded owing to welding stress produced may lead to the fracture of alloy. When carbide ball button fixed inserts welded steel body, the contact area between button and steel will appear gap in the drilling process, and gradually expand in the drilling process, the button broken finally, which generally occurs in the bottom surface of button.

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