Formation of the Structure and Phase Composition of Polycrystalline Diamond with Cobalt Infiltration in the System Diamond – Hard Alloy

Abstract

Polycrystalline diamond composites (PCD) were obtained by cobalt infiltration from a hard-alloy substrate into a porous diamond layer at temperature 1600°C and pressure 6.0 GPa in a cubic hydrostatic-compression press. To improve the thermal stability of the composite the upper layer of the cobalt was etched by hydrofluoric acid to depth 150 μm. Transmission electron microscopy (TEM) was used to analyze the interaction at grain-binder and grain-grain boundaries. After cobalt infiltration a nanodiamond phase and a cubic cobalt-carbide phase CoC_x are present on the grain-binder intergrain boundaries while after etching of the cobalt bulbous structures were found in the surface layer of the sintered polycrystalline diamond composite.