Polycrystalline cubic boron nitride Composite sheet, PCBN is made of cubic boron nitride mixed powder and hard alloy substrate under high temperature and pressure synthesis of a new composite super-hard material, its hardness only to Diamond, PCBN along with the CBN high hardness, high wear resistance and cemented carbide substrate with good impact toughness. Cubic boron nitride layer is composed of numerous fine-grained CBN no regular connection, the particles messy orientation, avoiding the single crystal anisotropy; also it has many excellent properties, such as high hardness（HV2500~5000 can be used for machining high hardness materials; also having a ratio of carbide and ceramic, higher wear resistance, at the same time, PCBN has a high thermal stability and chemical inertness, at 1000 ℃does not occur when the oxidation phenomenon, with iron-based materials at 1200~1300 ℃does not occur when a chemical reaction, in addition, it has good thermal conductivity and a low coefficient of friction in the machining accuracy, cutting performance, tool life, and other aspects show the incomparable superiority. Currently widely used in high-speed cutting, to car instead of grinding, hard-State cutting, dry cutting and other fields, especially suitable for grey cast iron, hardened steel and heat-resistant alloy machining.