Patent ID: 8017225

Claim:
A cutting tool made of surface-coated cubic boron nitride-based ultrahigh pressure sintered material, comprising: a main body consisting of ultrahigh pressure sintered material formed by ultrahigh pressure sintering of a compact having a composition of, in mass %, 13 to 30% of titanium nitride, 6.5 to 18% of aluminum and/or aluminum oxide and a balance of boron nitride, under an observation using a scanning electron microscope, the main body showing a texture such that an ultrahigh pressure sintering reaction product is present at the interface between a cubic boron nitride phase constituting a disperse phase and a titanium nitride phase constituting a continuous phase; and a hard coating that is vapor-deposited on the surface of the main body and has a lower layer of an average layer thickness in a range from 1.5 to 3 μm and an upper layer of an average layer thickness in a range from 0.3 to 3 μm, wherein: surface roughness Ra of the main body is 0.05 or more and 1.0 or less; the lower layer of the hard coating layer consists of a vapor-deposited composite nitride of Ti and Al having the composition of [Ti 1-X Al X ]N, where X is in a range from 0.40 to 0.60 in an atomic ratio; and the upper layer of the hard coating layer is vapor-deposited on the surface of the lower layer, having thin layers A consisting of a composite nitride of Ti and Al having the composition of [Ti 1-X Al X ]N, where X is in a range from 0.40 to 0.60 in an atomic ratio, and thin layers B consisting of a Ti nitride (TiN), and has a structure in which the thin layers A and the thin layers B are layered alternately such that an average layer thickness of each single thin layer A is in a range of 0.05 to 0.3 μm, an average layer thickness of each single thin layer B is in a range of 0.05 to 0.3 μm, wherein the hard coating further comprises a titanium nitride layer of 0.01 to 0.5 μm in thickness interposed between the main body and the lower layer.