Tungsten Carbide Button Processing Optimization (2/2)

However, high cost of equipment needed for hot isostatic pressing, productivity is relatively low, so another low pressure - hot isostatic pressing (LP-HIP) emerges. It will degrease and be densified in the furnace once completed, combined with vacuum sintering at relatively low temperatures and pressures, argon Ar as a medium hot isostatic pressing. This approach simplifies the process, saving energy consumption, to avoid the occurrence of the workpiece is difficult to control the carbon content in the production finally direct contact with air, which greatly eliminates the tooth carbide ball inside the residual porosity, grain refinement, effective by eliminating the hot isostatic pressing coarse-grained, cobalt pool and other defects, significantly improves the mechanical properties of tungsten carbide buttons.

The quenching - aging main principle is  Co binder phase can occur under certain conditions allotropic transformation, which was at room temperature HCP ε-Co, plasticity is poor, and when the temperature raises it can be converted face-centered cubic structure α-Co with good plasticity. In the quenching process, Co binder phase transition occurs rapidly cooled to room temperature and dissolved, so that α-Co is preserved. After aging, tungsten carbide buttons can be made in the supersaturated vacancies move grain boundaries or dislocations, etc. disappear, thereby reducing the lattice distortion, high stress relaxation area, making the overall flexural strength has been significantly improved. Currently, some quenching – aging treatments have been applied in production, such as vacuum oil quenching - natural aging, vacuums gas quenching – tempering and so on. They can be based maintaining tungsten carbide buttons on the other properties, and improve the hardness and toughness of buttons.

Conventional tungsten carbide buttons are round-shaped and bullet-shaped. In the process of drilling, round-shaped buttons will be easily passivated, and the bullet-shaped has shrill crown, which will be easily broken caused by insufficient strength of the matrix in some high impact loads or hard rock crushing conditions. Therefore, to improve tungsten carbide button shape has also become one of the research directions of researchers and scholars. Resistant carbide button is composed of a ball cap and approximate cone shape. In the process of breaking rocks in spherical cap shape be spherical die broken, approximate cone crusher is dovetail die, the two complement each other to get a good rock-breaking effect. It has higher drilling rate, excellent impact resistance, especially in some deep and long distance drilling, it has a good self-sharpening and does not need to be dragged, which remarkably improves the drilling efficiency. 

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