The hardest known materials

The superabrasive materials diamond and Cubic Boron Nitride (CBN) are the hardest materials known to this day. Therefore, their advantage compared to other grinding materials is the large resistance to mechanical abrasion. The degree of hardness that diamond and CBN show is considerably higher than those of conventional grinding materials, such as corundum and silicon carbide. Diamond are harder and more brittle than CBN. CBN is tougher, highly impact and termperature resistant.

Today mainly synthetically produced kinds of diamonds are used. The base material is graphite which is converted to a diamond by being submitted to a high pressure and high temperature synthesis. Pressure up to 60.000 bar is applied at a temperature of over 1500°C.

CBN is produced under similar conditions. In this case the base material is hexagonal boron nitride. Various synthesis conditions make it possible today to produce diamond and CBN grains with different crystal structures, hardness and breaking features for a variety of grinding applications. Moreover, grinding grains for resin bonds are additionally provided with metal coatings which improves the grain holding force inside the bonds and the heat flow.