亚微细硬质合金三牙轮钻齿的使用与失效分析

将钴含量为13％的亚微细晶粒硬质合金钻齿应用到81／2XA537三牙轮钻头上，并运用扫描电镜和光学显微镜等手段对亚微细晶粒硬质合金钻齿进行了失效分析。分析发现81／2XA537钻头的主要失效形式为崩齿和断齿。在断口分析的基础上，提出了亚微细硬质合金断裂机理为沿晶断裂，而常规硬质合金的断裂机理为穿晶断裂。由于生产工艺问题亚微细合金内部存在粗大的WC晶粒、晶粒偏析以及微裂纹，这些内部缺陷的存在使亚微细合金出现早期失效。

Application and Failure Analysis of Sub-micron Grained Cemented Carbide Insert of Three Roller Bits

The cemented carbide inserts made of sub-micron grained carbides tungsten and 13% cobalt were used on 81/2XA537 three-roller bits. The failure of sub-micron grain WC-Co cemented carbide inserts was analyzed by using scanning electron microscopy and optics microscope. The performance of the bits was also examined. It was revealed that the fracturing and cracking were the main types of failure of WC-Co inserts of 81/2XA537 bit. Based on the fracture analysis, it indicated that the rupture mechanism of sub-micron grained WC-Co cemented carbide inserts is different from conventional WC-Co cemented carbide inserts. It is transcrystalline fracture for sub-micron grained WC-Co cemented carbide inserts and the fracture for conventional cemented carbide inserts has occurred along the boundary of WC and Cobalt. The presence of abnormal large size carbides tungsten, discrete carbides tungsten agglomerate and micron flaw in sub-micron grained cemented carbide is responsible for their early failure.