PRODUCTION OF DIAMOND-COATED CUTTING TOOL MADE OF TUNGSTEN-CARBIDE-BASED SINTERED HARD ALLOY

摘要

PURPOSE:To produce a cutting tool made of WC-base sintered hard alloy excellent in peeling resistance by subjecting the surface of a base material composed of a sintered hard alloy having a specific composition consisting of Co and WC to grinding, to heat treatment, and to chemical etching, coating the above surface with artificial diamond, and carrying out heat treatment. CONSTITUTION:The surface of a base material composed of a WC-base sintered hard alloy having a composition consisting of 1-25wt.% Co as a binding phase forming component and the balance WC as a dispersed phase forming component with inevitable impurities is ground to = about 1.0mum average surface roughness. Subsequently, this base material is heat-treated in a nonoxidizing atmosphere at about 1000-1500 deg.C, by which Co is subjected to solid-phase diffusion into the surface. Chemical etching is applied to the base material after the above heat treatment by means of an aqueous solution of nitride acid, etc., by which Co is removed over the range from the base-material surface to a depth of =3mum and a Co-deficient layer is formed. Then, this base material is immersed into a suspended and dispersed solution of fine hard grains and ultrasonic waves are allowed to function. The surface of the above Co-deficient layer activated by the above procedure is coated with artificial diamond by a vapor phase synthetic method, and heat treatment is performed in a vacuum, atmosphere at a temp. where a liquid phase does not occur. By this method, the long-life diamond-coated cutting tool made of WC-base sintered hard alloy excellent in peeling resistance can be obtained.