Tungsten Carbide Buttons Optimization
Gradient structure: The top layer of gradient cemented carbide contains WC much to resist abrasion. The middle layer contains an amount of Co, so it has good toughness. This structure is beneficial for drilling, which has larger impact loads and longer working life. For instance, using φ45mm drill bit with DP55 cone button in limestone tunnel drilling, the average working life of gradient structure is 3121m at 1.96m/min compare with the ordinary 1000m at 1.48m/min. Many researchers overseas proves that the amount of carbon practical needs 0.1% -0.4% lower than theoretical value, and an appropriate increase in carburizing temperature conducive to migrate to the liquid Co sintered body inside. In addition, the different size of the sintered body should choose different respective carburizing time.
Adding elements: As we know, some manufactory would add a little TaC, which can improve alloy binder component for enhancing the wear resistance, toughness and strength. While it means that more cost and if add excessively, the results would reverse. After the addition of Ni, P in WC-Co cemented carbide can be formed Ni-Co-P, Ni-P and Co-P. The eutectic temperature of Co-P is 1020 degrees, the eutectic temperature of Ni-P is 880 degrees, and Co 1340 degrees lower than the melting point of 1495 degrees and WC-Co's. The main reason is that P atomic adsorption and segregation in Ni, Co particle surface, thereby reducing the energy of surface of Ni, Co particles. Therefore, such alloys in the liquid phase, and it makes early appearance dissolution and precipitation and the formation of the skeleton of solid particles also occurred in advance to make the process more fully sintered at a relatively low temperature. So it can effectively accelerate the speed of hard densification and improve the performance of tungsten carbide button.
For profile: With the development of deep drilling and oilfield excavation, the performance of tungsten carbide button is also concerned. Most of profiles of tungsten carbide button are ball-shaped, and bullet-shaped. But it would be easily deactivate when we use the ball-shaped and the bullet-shaped would be vulnerable because of lackness of the matrix under a large impact. Based on the effective mechanism of spherical broken rock and bending stress curve theory, some researchers design blunt-resistant tungsten carbide button. It combines the advantages of the ball-shaped with the bullet-shaped, which is composed of two parts, a spherical cap and a cone. Spherical side is used in ball-shaped pressing die, and another approximate cone side is used in wedge pressing so that the effect of rock breaking is improved.
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