One of the most critical components for oil and gas cirling is the rock bit, which crushes, abrades, or shears the rock in order to move deeper. Figure 1 is a cutaway schematic of a three-cone rock bit. The buttons or inserts on the rock bits are the means by which a bit drills through rock. These buttons or inserts are typically made of tungsten carbide-cobalt (WC-Co). Over the last fifty years, insert materials for three-cone bits in oil and gas-drilling applications have shown little deviation from the original materials. Raw materials and processes have improved, but the buttons still consist of a homogeneous mixture of carbide grains within varying amounts of cobalt. As expected, when a grade is modified to increase wear resistance and hardness, the toughness is reduced. For example, by reducing the cobalt content and/or grain size, hardness is increased. As a result of this rigid relationship, the drilling industry looked at alternate ways to improve toughness without sacrificing wear resistance or any other critical properties. This article first discusses conventional technology, and then describes some of the newer alternatives, including coarsegrain carbides, double-cemented carbides, and diamond-enhanced inserts.
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