| 摘要 |
PROBLEM TO BE SOLVED: To eliminate an occurrence of chipping of a cutting edge even in high speed/ feed cutting work on cast iron or steel, which is subjected to severe cutting condition, and to give excellent cutting property for a long period by taking advantage of the fact that a columnar Al2 O3 layer has higher strength and higher ductility compared with a granular Al2 O3 layer. SOLUTION: A cemented carbide cutting tool covered with a hard covering layer is formed by chemically/physically vapor-depositing both one or more out of Ti- compound layers consisting of hard covering layers containing an Al2 O3 layer, e.g. Ti-C layer, Ti-N layer, Ti-CN layer, Ti-O2 layer, Ti-CO layer, Ti-NO layer, and Ti- CNO layer, and a hard covering layer consisting of an Al2 O3 layer on the surface of a WC-group cemented carbide substrate to the mean thickness of 2 to 20μm. In this case, Al2 O3 layer constituting the hard covering layer should be such that the main body of Al2 O3 is of anα-type crystal structure, the crystalline structure of the upper side part is different from that of the lower side part (substrate side), the upper side part is constituted of the columnar Al2 O3 layer having the crystalline structure in which columnar grains are arranged in parallel in the longitudinal direction, and the lower side part is constituted of the granular Al2 O3 layer having the granular crystalline structure.
|
