Shear bits, also known as drag bits or fixed cutter bits, drill rock substantially faster than roller-cone bits. At present their use is limited to soft and medium formations. It would be highly desirable to expand their use into hard rock, both for drilling of oil and gas and for geothermal applications. A new type of heat resistant, polycrystalline diamond-containing hard rock cutter will developed in this project. While composite polycrystalline diamond-tungsten carbide/cobalt cutters have excellent abrasion resistance, they are highly sensitive to the high temperatures that occur when sufficiently drilling hard rock. Although some polycrystalline diamond materials are known to resist high temperatures, they are not available in the sizes and shapes needed for fast-cutting shear bits, nor is there a means known for bonding thermally stable polycrystalline diamond to a tungsten carbide/cobalt support. Therefore, this project will develop a cutter consisting of thermally stable polycrystalline diamond bonded to a tungsten carbide/ cobalt substrate, which would enable a much more efficient use of thermally stable diamond than previously possible. Phase I will develop a process for economically producing thermally stable polycrystalline diamond disks to exact net shape, investigate several processes for bonding the thermally stable disk to a tungsten carbide support, complete an engineering design of bonding equipment.
Commercial Applications and Other Benefits as described by the awardee:Development of a thermally stable diamond disk, together with a high-strength, low-stress bond to a tungsten carbide/cobalt support, will lead to a cutter that will withstand high impact forces and high cutting temperatures. This will enable the use of shear bits in harder formations than hitherto possible. The thermally stable cutter will also find application in bearings for mud motors and gauge protectors for stabilizers and roller-cone bits.
