Characteristics of diamond regrowth in a synthetic diamond compact

Abstract

A transmission electron microscopic study of a commercial sintered diamond compact is reported that identifies and characterizes the diamond that has regrown between the grains of the original diamond powder during the high-pressure, high-temperature manufacturing process of the compact. The majority of the original grains are strongly deformed whereas the regrown diamond shows little or no plastic deformation. The dislocations in diamond regrown between the original grains occur in low-angle boundaries and other configurations typical of grown-in dislocations in crystals. The manufacturing process involves infiltrating the diamond aggregate by molten cobalt, and the regrown diamond is characterized by the presence of cobalt inclusions in sizes ranging from a few tenths of a micrometre down to a few nanometres, possessing the same orientation and lattice parameter as the diamond host. Graphite inclusions also occur in regrown diamond, few in comparison with cobalt inclusions and in random orientation. The graphite crystals exhibit axial ratios, (c/a), lowered by several per cent due to the containment pressure exerted by the diamond host.