SURFACE COATED CUTTING TOOL IN WHICH HARD COVERING LAYER EXHIBITS SUPERIOR PEELING RESISTANCE AND SUPERIOR CHIPPING RESISTANCE IN INTERMITTENTLY CUTTING HARD DIFFICULT-TO-CUT MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide a surface coated cutting tool in which a hard covering layer exhibits superior peeling resistance and superior chipping resistance in intermittently cutting a hard difficult-to-cut material.;SOLUTION: The cutting tool is formed by coating an uppermost surface of a tool substrate constituted of a tungsten carbide based cemented carbide or titanium carbonitride based cermet with at least an Nb boride layer with an average layer thickness of 0.5-5 μm. In the cutting tool, the Nb boride layer is constituted as a composition structure of a crystalline grain structure with multiple average grain sizes. The composition structure is constituted of: a secondary crystalline grain constituted of an aggregate of a primary crystalline grain with an average grain size of 5-20 nm and having an average grain size of 40-80 nm; and a tertiary crystalline grain constituted of an aggregate of the secondary crystalline grain and having an average grain size of 150-800 nm.;COPYRIGHT: (C)2012,JPO&INPIT