Polycrystalline diamond mini-cubes for sawing applications

摘要

Diamond grits are indispensable for sawing granite or concrete. Each year about 1 000 tons of diamond grits are consumed for such purposes. In all cases, mono crystalline diamond is used. However,polycrystalline grits (polygrits) are generally better performed than mono grits as abrasives. For example, poly grits of cubic boron nitride (e. g. Borazon(R) CBN-550 of Diamond Innovations) can cut faster and they last longer than mono grits (e. g. Borazon(R) CBN-500).Polygrits of alumina (e. g. Cubitron(R) of 3 M) also out perform by far glassy grits (e. g. white alumina). For diamond superabrasives, micron polygrits formed by shock waves may polish as fast as mono grits of the same size, but without causing as much scratches due to the presence of smaller sintered grains. The improved performance of poly grits is attributed to their ability to micro chipping that renews the sharp cutting corners from time to time. By contrast, mono grits tend to round off at low cutting force or macro fracture at high cutting force, so they may lose the cutting ability rapidly.For sawing granite with mesh sizes 40/50 or coarser, poly grits of diamond have not been available until recently. In this research, we have made polygrits in mini cube with sizes of 18/20, 20/25, and 30/40. Turbo grinders and wire saws were made by brazing both mono grits and polygrits on steel substrates. Cutting performance on granite demonstrated that grinding speed was faster with turbo grinder, and the surface finish was smoother with wire saw for poly grits than mono ones.Polygrits and mono grits of diamond were mixed for comparison (upper left). Polygrits of mini cubes were brazed on the pearl of a wire saw (upper right). Mono diamond grits were brazed on a turbo grinder (bottom diagrams).