Study of high-frequency microspark-erosion of boron-doped polycrystalline diamond

The native property of weakly conductive Boron-doped polycrystalline diamond (B-doped PCD) as a high-melting point, resistant, super-hard material makes it particularly difficult to machine. This paper focuses on the relative merits of eroding B-doped PCD by spark-erosion based on different power sources: commercial transistorized, Resistance-Capacitance (R-C), and designed high-frequency microspark-erosion power. Experimental results show B-doped PCD endures spark-erosion longer under commercial transistorized power although its Material-Erosion-Rate (MER) is higher. This greatly facilitates surrounding air scurries into the PCD matrix during melting and cooling. A poorer material-erosion-rate presents under R-C power due to its lower duty cycle. In contrast, dense eroded microcraters realizing a solid and regular distribution on the PCD matrix occur under high-frequency microspark-erosion power. The erosion-energy beam is supplied by a current train of high-frequency, high-peak and short-pulse-time, resulting relatively more diamond being vaporized than melted. The amount of eroded diamond is so little that debris is exceedingly slight and swiftly cleared away between each pulse-on-time. The extensive solid erosion craters resulting from the process are very useful as chip-pockets on the PCD wheel-tool for disposal of ground chips during microgrinding. Additionally, aspects relating to the merits of B-doped PCD are evaluated in detail: spark-erosion-ability (SEA) of B-doped PCD, surface roughness on B-doped PCD, depositional amounts of cobalt, and graphitization of diamond.