Diffusion and Infiltration Mechanisms of Cobalt through Diamond Layer during the Sintering of Polycrystalline Diamond Compacts

The mechanisms of solid cobalt diffusion, molten cobalt infiltration and two wave-like cobalt peaks movement through diamond layer during the sintering process were discussed theoretically according to the experiment data. Results show that the solid cobalt diffusion coefficient under 5.8 GPa and at 1 300 ℃ is about 1.610-7 cm2/s, which is almost the mean value between the solid cobalt diffusion coefficient (310-10 cm2/s) at the same temperature under atmospheric pressure and the liquid cobalt diffusion coefficient (510-5 cm2/s) under 5.8 GPa and at 1 300 ℃. It also shows that the infiltration time of molten cobalt through diamond layer for diamond grain size 10 m and 1 m are about 0.5 s and 28 s respectively, and the moving velocity of the two wave-like cobalt peaks were about 50 m/s and 100 m/s, respectively.