A base material for a hard sintered body includes a pillar portion having a central axis and extending in the axial direction of the central axis. The pillar portion has a first outer peripheral portion, a second outer peripheral portion, and a protruding stripe portion. In the cross-sectional view, one side portion of the first outer peripheral portion extending in a circumferential direction or a radial direction is located inside the other side portion. In the cross-sectional view, one side portion of the second outer peripheral portion extending in the circumferential direction or the radial direction is located outside the other side portion in the radial direction. The protruding stripe portion is located in a connection portion between the other side portion of the first outer peripheral portion and one side portion of the second outer peripheral portion, and protrudes outward.

A cutting tool includes a base material, and a coating film covering the base material in contact with the base material. The base material is a cubic boron nitride sintered material. The coating film is a ceramic. An amount of oxygen in the coating film is less than or equal to 0.040 mass percent.

A cutting insert has a surface that relates to cutting, the surface comprising cBN sintered material, ceramics, or cermet. The cutting insert comprises: a rake face; a flank face; a chamfer located between the rake face and the flank face; and a cutting edge formed by a ridgeline at which the flank face and the chamfer intersect. The cutting edge comprises a cutting edge portion for push cutting, a cutting edge portion for pull cutting, and a connecting cutting edge portion located between the cutting edge portion for push cutting and the cutting edge portion for pull cutting. In the chamfer located along the cutting edge, the chamfer located along the connecting cutting edge portion has a minimum width.

In one aspect, cutting tools are provided comprising radiation ablation regions defining at least one of refractory surface microstructures and/or nanostructures. For example, a cutting tool described herein comprises at least one cutting edge formed by intersection of a flank face and a rake face, the flank face formed of a refractory material comprising radiation ablation regions defining at least one of surface microstructures and surface nanostructures, wherein surface pore structure of the refractory material is not occluded by the surface microstructures and surface nanostructures.

A cBN sintered compact comprising a cubic boron nitride and a ceramic binder phase, wherein a cubic C-containing Ta compound in an amount of 1.0 to 15.0 vol % is dispersed in the ceramic binder phase and has a mean particle diameter of 50 to 500 nm.

A cBN-based ultra-high pressure sintered body contains cBN particles and a binder phase. The binder phase contains at least one of a nitride or oxide of Al or a nitride, carbide, or carbonitride of Ti, and a metal boride having an average particle diameter of 20 to 300 nm is dispersed in an amount of 0.1 to 5.0 vol % in the binder phase. The metal boride includes a metal boride (B) containing at least one of Nb, Ta, Cr, Mo, and W as a metal component and containing no Ti and a metal boride (A) containing only Ti as a metal component. In a case where a ratio (vol %) of the metal boride (A) in the metal boride is represented by V.sub.a and a ratio (vol %) of the metal boride (B) is represented by V.sub.b, a ratio of V.sub.b/V.sub.a is 0.1 to 1.0.

In one aspect, refractory coatings are described herein having multiple cubic phases. In some embodiments, a coating comprises a refractory layer of TiAlN deposited by PVD adhered to the substrate, the refractory layer comprising a cubic TiAlN phase and a cubic A1N phase, wherein a ratio of intensity in the X-ray diffractogram (XRD) of a (200) reflection of the cubic AlN phase to intensity of a (200) reflection of the cubic TiAlN phase, I(200)/I(200), is at least 0.5.

An insert includes a cBN sintered compact including cBN particles and a binder phase binding the cBN particles. The cBN particles occupy 60% or more of the cross-sectional area of the cBN sintered compact. The binder phase contains Al compound particles containing at least one of AN or Al.sub.2O.sub.3. A particle distribution of the Al compound particles in a cumulative distribution based on the number of the Al compound particles in a cross section of the cBN sintered compact is as follows. The proportion of the Al compound particles with the particle diameter of 0.3 μm or larger is 5% or more, and the proportion of the Al compound particles with the particle diameter of 0.5 μm or larger is less than 5%.

A cutting tool according to the present disclosure has a rake face, a flank face, and a cutting edge. The cutting edge is located between the rake face and the flank face. The cutting tool includes a substrate composed of a cubic boron nitride sintered material, and an oxide layer that covers the substrate and that constitutes at least part or whole of the rake face, the flank face, and the cutting edge. The oxide layer includes at least one element selected from a group consisting of titanium, aluminum, zirconium, and cobalt. A thickness of the oxide layer is 2 μm or less.

A method of producing a cubic boron nitride sintered material includes: forming an organic cubic boron nitride powder by attaching an organic substance onto a cubic boron nitride source material powder; preparing a powder mixture including more than or equal to 85 volume % and less than 100 volume % of the organic cubic boron nitride powder and a remainder of a binder source material powder by mixing the organic cubic boron nitride powder and the binder source material powder, the binder source material powder including WC, Co and Al; and obtaining the cubic boron nitride sintered material by sintering the powder mixture.