Effect of quenching processes on microstructures and tribological behaviors of polycrystalline diamond compact (PCD/WC-Co) in annealing treatment

Enhanced tribological behaviors are urgently desired for scientists and engineers to improve the service life of polycrystalline diamond compact (PDC) instruments. Here, PDC samples, involved sintering a polycrystalline diamond (PCD) layer to a cemented carbide (WC-16wt%Co) substrate under high temperature/high pressure (HT/HP) condition, have been annealed at 500 degrees C in ambient air to achieve perfect wear resistances and low friction coefficients. The various quenching processes, such as air-quenching (AQ), water-quenching (WQ) and furnace-quenching (FQ), control the morphologies and chemical conversions of PDC surfaces, and eventually affect their tribological behaviors. The WQ process with the highest cooling rate can effectively remove the tiny diamond grains (TD grains, sizes of 0-5 mu m) on PDC surface before sliding test, which can greatly enhance the wear resistance and slightly increase the friction coefficient of PDC (< 0.1). Oppositely, the FQ process with the slowest cooling rate leads to decreasing of friction coefficient and deterioration of wear resistance of PDC. It is noted that the TD grain acts as a double-edged sword. On the one hand, it induces the formation of transfer film to decrease the friction coefficient of annealed PDC. On the other hand, it causes the extraction of medium size diamond grains (MD grains, sizes of 5-15 mu m) and eventually results in the wear of PDC. These results may give significant instructions for improving tribological behaviors of annealed PDC with selectable quenching processes.