| 摘要 |
A surface-coated cermet cutting tool is formed by depositing on a surface of a tool substrate made of WC-based cemented carbide or TiCN-based cermet a hard-coating layer composed of the following layers (a) and (b): (a) the lower layer is composed of one or more layers of TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer and has a total average layer thickness in the range of 3 to 20 µm, and (b) the upper layer is an aluminum oxide layer having an ±-type crystal structure when chemically deposited and has an average layer thickness in the range of 1 to 15 µm. In the case of the upper layer, the reformed ±-Al 2 O 3 layer shows distribution graphs of covalent lattice points of constituent atoms, which shows distribution ratios of individual £N+1 to total £N+1, having the highest peak at £3 and showing the distribution ratios of £3 to total £N+1 in the range of 60 to 80%, in this case, the crystal grains have a corundum-type hexagonal close-packed structure in which constituent atoms consisting of aluminum and oxygen exist in lattice points; the distribution of the lattice points (the covalent lattice points of constituent atoms) where the respective constituent atoms share one constituent atom between adjacent crystal grains at the interface of the crystal grains are calculated; a covalent lattice point configuration of constituent atoms, in which N lattice points sharing no constituent atom between the covalent lattice points of constituent atoms exist is represented by the £N+1. |
