Thermal effects on tribological behaviors of polycrystalline cubic boron nitride

Abstract

In order to understand the thermal damage mechanisms of polycrystalline cubic boron nitride (PcBN) under elevated temperature and the following influences on its tribological behaviors, the physicochemical characteristic of annealed PcBN under various temperatures was investigated by X-ray diffraction, Scanning electron microscopy and energy dispersive x-ray spectroscopy measurements. Furthermore, the tribological behaviors of annealed PcBN sliding against the typical commercial AISI 52100 steel ball were evaluated. These results demonstrate that the new oxidation phase TiO2, which exhibits uniform whisker with nanorod shape owing to the effect of gas diffusion channels, is produced from the binder phases TiN and TiB2 above 800 °C. Moreover, the coefficient of friction (CoF) dependent on annealed temperatures is coincident with the changing tendency of wear volume of counter balls, where the CoF and wear volume bottomed at 800 °C. Below 800 °C, the wear mechanism is adhesive wear owing to the formation of the iron transfer film, while at 900 °C is abrasive wear because of the spalling off of grains acting as the three-body hard phases.