| 主权项 |
1. A surface-coated cutting tool comprising:
a cutting tool body made of tungsten carbide-based cemented carbide; and a hard coating layer that has an average thickness of 2 μm to 10 μm and is vapor-deposited on a surface of the cutting tool body, wherein the hard coating layer is made of a complex nitride layer of Al and Cr, a Cr content with respect to a total amount of Al and Cr being 0.2 to 0.5 in atomic ratio; a part of the hard coating layer, which is vapor deposited on a region of a flank face from a cutting edge on a flank face of the cutting tool body of the surface-coated cutting tool to a location 100 μm from the cutting edge on the flank face toward an opposite side thereof, has a granular crystal structure: an average grain size of granular crystals on a surface of the part of the hard coating layer formed on the region is 0.2 μm to 0.5 μm; an average grain size of granular crystals at an interface between the cutting tool body and the part of the hard coating layer on the region is smaller than the grain size of granular crystals on the surface of the part of the hard coating layer by 0.02 μm to 0.1 μm; a crystal grain size length ratio of crystal grains whose size is 0.15 μm or less is 20% or less, a compressive residual stress in the hard coating layer is 2.0 to 2.7 GPa, a crack occupancy ratio β/α is 0.3 to 1.0, α being an angle of the cutting edge of the surface-coated cutting tool in degrees, and β being an occupied angle of a continuous crack formed in the hard coating layer in a corner portion of a front-end cutting edge within the angle defined by α, a minimum width of the continuous crack being 30 nm, and an aspect ratio of crystal grains included in the granular crystal structure is 1 or more and 6 or less. |
