Turning of Hardened Ferrous Materials with Homogeneous CBN (Cubic Boron Nitride) Tool Tips

摘要

The properties of amborite, presented in the form of homogeneous polycrystalline boron nitride disposable tool chips, are discussed. In its physical properties Amborite differs substantially from commonly used conventional cutting media (high speed steel, sintered carbides, cemented oxides) and approaches diamond in hardness while coming between cemented oxides and K10 sintered carbide in bending strength. The thermal conductivity of Amborite is vastly superior to that of cemented oxide and approaches that of metallic abrasives with the result that thermal stresses in the cam remain negligible during both interrupted and cooled cutting, eliminating the risk of stress cracks as encountered with cemented oxides. The great hardness of Amborite permits a reduction in cutting forces, which partly consist of frictional forces in turn determined by hardness differences between material and cam. In cutting behavior Amborite resembles sintered carbide rather than cemented oxide and like the former is subject to cratering wear of the cutting surface.