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.

To provide a tool that ensures improved durability even when a diamond coating containing boron is formed. A diamond coating (40) includes a first layer (41) that is formed as a layer on a surface layer side of the diamond coating (40) and is regarded as containing no boron, and a second layer (42) positioned on a side of a base material (30) with respect to the first layer (41) and contains at least 1000 ppm or more of the boron. Since the first layer (41) with a larger compressive stress is formed on the surface layer of the diamond coating (40), a crack generation from the surface layer side of the diamond coating (40) during the process can be reduced. Consequently, the durability of a tool (1) can be improved even when the diamond coating (40) containing 1,000 ppm or more of boron is formed.

A cutting part of a cutting insert may include a first surface including a corner, a first side, a first region, a second region and a third region. The first region may be located along the corner and the first side. The second region may be located at a more inner part than the first region. The third region may be located at a more inner part than the second region. A boundary between the corner and the first side may be a first point. A boundary between the first region and the second region may be a second point in a cross section that passes through the first point and is orthogonal to the first side. An imaginary straight line passing through the first point and the second point may be a first imaginary straight line. The first imaginary straight line may intersect with the third region.

A composite sintered material includes: a plurality of diamond grains having an average grain size of less than or equal to 10 μm; a plurality of cubic boron nitride grains having an average grain size of less than or equal to 2 μm; and a plurality of aluminum oxide grains having an average grain size of less than or equal to 0.5 μm; and a remainder of a binder phase, wherein at least parts of adjacent diamond grains are bound to one another, the binder phase includes cobalt, in the composite sintered material, a content of the diamond grains is from 30 to 92 volume %, a content of the cubic boron nitride grains is from 3 to 40 volume %, a content of the aluminum oxide grains is from 2 to 15 volume %, and a content of the cobalt is from 3 to 30 volume %.

A cutting tool, including a silicon nitride (Si.sub.3N.sub.4) ceramic substrate, and a diamond film coated on the surface of the Si.sub.3N.sub.4 ceramic substrate. The diamond film has a thickness of 7-12 μm. The cutting tool includes a tool nose, a blade, and a handle. The blade has a rake angle γ of 5-15°, a clearance angle α of 10-14°, and a helix angle of 15-45°. The blade includes four cutting edges.

A diamond-coated tool includes: a substrate; and a diamond layer that coats the substrate, wherein the diamond layer includes a first region that is in contact with the substrate, the first region includes a region S1 surrounded by an interface P between the substrate and the diamond layer and an imaginary plane V1 separated from the interface P by a distance of 2 μm, and the region S1 has crystal grains grown in random directions.

A throwaway insert includes a base and a cutting edge member. The cutting edge member includes: a rake face; a flank face extending to cross the rake face; a first connecting face connecting the flank face to a side surface of the base and extending to cross the rake face; and a first ridgeline formed by the rake face and the flank face and serving as a cutting edge. When viewed in a plan view from the upper surface of the base, the flank face and the first connecting face are located external to the base. A second ridgeline formed by the rake face and the first connecting face crosses the first ridgeline at an obtuse angle.

In a diamond-coated tool, a flank face of a tool base material includes a first flank face continuously extending to a cutting edge, a second flank face located farther away from the cutting edge than the first flank face and located outside the first flank face when viewed from an inside of the tool base material, and a flank face-side stepped portion connecting the first flank face and the second flank face. A diamond-coated layer is provided on the first flank face and the flank face-side stepped portion.

Provided is a cutting method of cutting, with a diamond cutting tool, a metal material having at least a solid solution layer on a surface, the solid solution layer containing nitrogen atoms as interstitial solid solution atoms. In this method, cutting is performed in a region where a nitrogen concentration is equal to or greater than a predetermined concentration, and cutting is not performed in a region where the nitrogen concentration is less than the predetermined concentration.

A rotary cutting tool includes a base material, a first diamond layer, and a second diamond layer. The base material includes a head portion, a body portion, and a shoulder portion defining a boundary portion between the head portion and the body portion. The first diamond layer covers the body portion and the shoulder portion and exposes the head portion. The second diamond layer covers the head portion, is provided on the first diamond layer in the shoulder portion, and does not cover the body portion.