Effects of environmental atmospheres on tribological behaviors of sintered polycrystalline diamond sliding against silicon nitride

To explore the effect of various atmosphere the tribological behaviors of the sintered polycrystalline diamond compacts (PDCs), the friction and wear behaviors of PDCs sliding against Si3N4 balls were evaluated by a ball-on disk tribometer under nitrogen, argon, oxygen and air (10% relative humidity) environments, respectively. The energy dispersive X-ray spectrum (EDS), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscope (AFM) were conducted to investigate the microstructure evolution of worn surface. The results demonstrated that the low friction appeared in argon and nitrogen environment. The formations of consecutive carbonaceous transfer films on wear scars contributed to decrease the friction during sliding process. The wear of PDCs and Si3N4 balls were serious in argon and nitrogen environment, but slight in oxygen and air conditions. There is a direct relationship between material removal and running-in period. The passivation effect of dangling bond under oxygen and air conditions can shorten the running in period thus weaken the wear.