CUTTING TOOL MADE OF SURFACE COATED TUNGSTEN CARBIDE-BASE SINTERED HARD ALLOY EXCELLENT IN ADHESIVE STRENGTH OF HARD COATING LAYER

摘要

PURPOSE:To obtain a long-life cutting tool made of surface coated WC-base sintered hard alloy excellent in adhesive strength of hard coating layer by forming a hard coating layer of metal carbide, etc., on the surface of a base material made of WC-base sintered hard alloy in which Co content in the surface part is reduced. CONSTITUTION:In a base material composed of a WC-base sintered hard alloy containing Co as a binding phase forming component, the content of the above Co in the surface part is reduced to 90% of Co content in the inner part. Further, it is preferable that the grain of WC as a hard phase forming component in the surface part is coarser by 10% than the grain of WC in the inner part. Subsequently, a hard coating layer which consists of a single layer composed of one kind among the carbides, nitrides, and oxides of the group IVa, Va, and VIa metals, solid-, solutions of two or more kinds among the above, and Al2O3 or a multilayer composed of two or more kinds among the above is formed on the surface of the above base material. By this method, the cutting tool made of the surface coated WC-base sintered hard alloy excellent in the adhesive strength of the above hard coating layer to the base-material surface, showing superior wear resistance and breaking resistance, and capable of maintaining cutting property over a long period can be obtained.