Surface-coated boron nitride sintered body tool

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 being formed of columnar crystals and including MLazai (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 of columnar crystals and 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 0.5 nm or more and 300 nm or less,
• said compound layers each having a thickness of 0.5 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 A1;
• 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 (A11−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),
• said A layer having a thickness of 0.2 μm or more and 10 μm or less, said B layer having a thickness of 0.05 μm or more and 5 μm or less, and said coating film having an entire thickness of 0.3 μm or more and 15 μm or less, and
• a particle size Wa of each of said columnar crystals included in said A layer being 10 nm or more and 400 nm or less, and a particle size Wb of each of said columnar crystals included in said B layer being 5 nm or more and 70 nm or less.