Friction and wear behavior of polycrystalline diamond at temperatures up to 700 °C

Abstract The friction and wear behavior of the polycrystalline diamond (PCD) were evaluated in ambient air at temperatures up to 700 °C using a ball-on-disk high temperature tribometer. The wear surface features of the PCD were examined by scanning electron microscopy. Energy dispersive X-ray analysis was used to investigate the chemical composition. XRD experiments were performed to study the crystal structure of the PCD specimens at different temperatures. Results showed that the friction coefficient of the PCD is different depending on the temperature, and decreases with the increase of temperature. The PCD exhibited the lowest friction coefficient of approximately 0.16 in the case of 700 °C sliding operation. The difference of the worn surface features of the PCD after sliding at different temperatures is related to the chemical transformation during sliding wear tests. The surface damage of the PCD appears to happen around 600 °C accompanied by extensive Co phase extrusion out of PCD. Numerous micro-cracks both at the grain boundaries and in the grains are observed with the increase of temperature to 700 °C. At this temperature, surface graphitization of diamond is to be expected, and the formation of graphite on the wear track is beneficial to the reduction of friction coefficient.