| 主权项 |
1. A surface-coated boron nitride sintered body tool, in which at least a cutting edge portion includes a cubic boron nitride sintered body and a coating film formed on a surface of the cubic boron nitride sintered body,
said cubic boron nitride sintered body comprising 30 vol % or more and 80 vol % or less of cubic boron nitride particles, and further comprising a binder phase including at least one compound selected from the group consisting of nitride, carbide, boride, oxide, and solid solutions thereof in group 4 elements, group 5 elements and group 6 elements in a periodic table, an aluminum compound, and inevitable impurities, said coating film including an A layer and a B layer, said A layer including MLaza1 (M represents one or more of group 4 elements, group 5 elements and group 6 elements in the periodic table, Al and Si; La represents one or more of B, C, N, and O; and za1 is 0.85 or more and 1.0 or less), said B layer being formed by alternately stacking one or more of each of two or more compound layers having different compositions, said compound layers each having a thickness of 30 nm or more and 300 nm or less, one of said compound layers being a B1 compound layer, said B1 compound layer including (Ti1-xb1-yb1Sixb1M1yb1)(C1-zb1Nzb1) (M1 represents one or more of group 4 elements except for Ti, group 5 elements and group 6 elements in the periodic table, and Al; xb1 is 0.01 or more and 0.25 or less; yb1 is 0 or more and 0.7 or less; and zb1 is 0.4 or more and 1 or less), one of said compound layers being a B2 compound layer, said B2 compound layer being different from said B1 compound layer, and including (Al1-xb2M2xb2)(C1-zb2Nzb2) (M2 represents one or more of group 4 elements, group 5 elements and group 6 elements in the periodic table, and Si; xb2 is 0.2 or more and 0.7 or less; and zb2 is 0.4 or more and 1 or less), t2/t1 that is a ratio between an average thickness t1 of said B1 compound layers and an average thickness t2 of said B2 compound layers satisfying a relation of 0.5<t2/t1≦10.0, and said A layer having a thickness of 0.2 μm or more and 10 μm or less, said B layer having a thickness of 0.1 μm or more and 5 μm or less, and said coating film having an entire thickness of 0.5 μm or more and 15 μm or less, and assuming that a thickness of said B1 compound layer is indicated as t10, a thickness of said B2 compound layer is indicated as t20, and a thickness ratio between said B1 compound layer and said B2 compound layer that are in contact with each other is indicated as t20/t10, said t20/t10 gradually decreasing from a cubic boron nitride sintered body-side toward an A layer-side, a relation of 1.0<t20/t10≦5.0 being satisfied on said cubic boron nitride sintered body-side, and a relation of 0.5<t20/t10<3.0 being satisfied on said A layer-side. |
