| 摘要 |
PROBLEM TO BE SOLVED: To provide a machining tool made of surface-covered cemented carbide having a hard covering layer exhibiting an excellent chipping resistance in intermittent heavy-duty machining. SOLUTION: To the surface of the cemented carbide body based on tungsten carbide, a hard covering layer having a total mean thickness of 5-25μm is formed by chemical evaporation, wherein the hard covering layer is composed of (a) a Ti-compound layer consisting of one or more of layers of TiC, TiN, TiCN, TiCO and TiCNO each of which has a mean thickness of 0.1-5μm and has a granular crystalline structure and in which a residual tensile stress exists, (b) a TiCN layer having a mean thickness of 2-15μm and composed of an upper layer where a residual compressive stress exists and a lower layer where a residual tensile stress exists, (c) a TiN layer having a mean thickness of 2-15μm and composed of an upper layer where a residual compressive stress exists and a lower layer where a residual tensile stress exists, and (d) an Al2O3 layer which has a mean thickness of 0.5-10μm and a granular crystalline structure and in which a residual tensile stress exists.
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