Suppression of abnormal grain growth in fine grained polycrystalline diamond materials (PCD)

During the sintering of fine grained (0.5 μm) polycrystalline diamond (PCD) composite materials under high pressure-high temperature (HPHT) conditions, abnormal grain growth (AGG) of the diamond was observed. These abnormally grown diamond grains were up to several hundreds of microns in diameter. Diamond enhanced carbide substrates were used to suppress the abnormal grain growth. Electron backscattered diffraction was used to obtain grain orientation of the single crystals. The AGG was explained in a framework of the changed driving forces of the grain growth due to different initial carbon concentrations in the melt, particle size distribution and growth mechanisms.

► Ultrahigh pressure experiments used to study abnormal grain growth (AGG) in PCD. ► The AGG mechanism is discussed in terms of driving forces. ► The driving forces are initial C concentration in the melt and grain size. ► Carbon saturation in liquid cobalt is a key factor for controlling diamond AGG.