Improved vacuum tribological properties of sintered polycrystalline diamond compacts treated by high temperature annealing

Triboenvironment Dependent Chemical Modification of Sliding Interfaces in Ultrananocrystalline Diamond Nanowall Film: Correlation with Friction and Wear

“…Therefore, in this condition, graphitization of the sliding interfaces can be considered for improving the tribological properties significantly. 42 The evidence of graphitized sliding interfaces is well investigated by Raman spectroscopy (Figure 6) and XPS (Figure 9). For clear understanding, the graphitized ball scar is schematically given in Figure 10c and the bar graph in Figure 10d.…”

“…This can be explained by the lack of external passivation when chemical adsorbate is absent to passivate the unsaturated bonds at the sliding interfaces. , However, hydrogenated UNCD films show low/ultralow friction value in high vacuum condition due to the passivation mechanism. , This was performed by the hydrogen atoms/molecules intrinsically present in the films. Moreover, at moderate temperature, surface graphitization of diamond films was favorable in reducing the friction in air and vacuum conditions. , Furthermore, an ultralow friction coefficient with high wear resistance was measured at 200 °C in UNCD films which was explained by the formation of chemically passivated sliding interfaces. However, at higher temperature, tribological performances of these films were significantly degraded and failure happened mainly due to the oxidation and amorphization/polymerization at the sliding interfaces .…”

“…In this case, atmospheric water vapor is restricted during the tribology test and the passivation mechanism of dangling bonds at contact interfaces is energetically not favorable. Therefore, in this condition, graphitization of the sliding interfaces can be considered for improving the tribological properties significantly . The evidence of graphitized sliding interfaces is well investigated by Raman spectroscopy (Figure ) and XPS (Figure ).…”

“…Moreover, at moderate temperature, surface graphitization of diamond films was favorable in reducing the friction in air and vacuum conditions. 41,42 Furthermore, ultra-low friction coefficient with high wear resistance was measured at 200 o C in UNCD films and this was explained by the formation of chemically passivated sliding interfaces. However, at higher temperature, tribological performance of these 6 films were significantly degraded and failure happened mainly due to oxidation and amorphization/polymerization of the sliding interfaces.…”

Optical Quality Laser Polishing of CVD Diamond by UV Pulsed Laser Irradiation

“…Surface micro-bump structures also appear after the first laser scan as a result of graphitized material swelling, which can be observed in Figure 3a. It is known that the temperature for diamond graphitization is around 700 °C, [45,46] which is much lower than the melting point (≈3550 °C). Laser graphitization is much easier than diamond melting.…”