Chipping Resistant Polycrystalline Diamond and Carbide Composite Materials for Roller Cone Bits

Abstract

Abstract Cemented tungsten carbide and polycrystalline diamond are the most critical materials used for roller cone bit cutting structure. Chipping and catastrophic breakage are the primary failure modes for the materials and hence the limiting factor of service life of a drill bit. Chipping and fracture resistance can be improved at the expense of hardness and wear resistance of the materials. This trade-off between wear resistance and chipping resistance hinders the development of super hard materials for demanding drilling applications. Functionally designed composite materials of polycrystalline diamond (PCD) and cemented tungsten carbide (WC-CO) that offer enhanced chipping resistance without significantly sacrificing wear resistance are studied and reported in this presentation. Specifically, one example of the functionally designed composite materials is a honeycomb structured composite of polycrystalline diamond (PCD) and WC-Co and its application for diamond enhanced inserts for roller cone bits. The PCD/WC-Co composite takes advantages of high modulus and superior wear resistance of diamond, while it mitigates chipping and cracking using the tougher WC-Co as cell boundaries. The overall engineering properties and performance are superior to that of pure PCD. Another example of functionally engineered hard materials is double cemented (DC) tungsten carbide. Double cemented tungsten carbide has 50% or higher fracture toughness than conventional cemented tungsten carbide at equivalent wear resistance. When compared to tool steels, DC carbide has equivalent fracture toughness but much higher wear resistance. Field tests of honeycomb structured diamond enhanced inserts (CDEI) demonstrated the controlled chipping characteristics and longer durability of components as compared to conventional homogeneous PCD materials with comparable wear resistance. DC carbide also exhibited excellent damage tolerance during field tests in demanding applications where excessive heat checking and fracturing of inserts are common failure modes.