The present invention is directed to a surface-coated cubic boron nitride sintered material tool including a cBN substrate and a hard coating layer formed on a surface of the cBN substrate and having an alternate laminated structure of A layer and B layer. A peak of the grain size distribution of cBN grains in the cBN sintered material is present within a range of a grain size from 0.50 to 1.00 m. The A layer has a composition of (Ti.sub.1-xAl.sub.x)N (0.4x0.7 in an atomic ratio). The B layer has a composition of (Cr.sub.1-y-zAl.sub.yM.sub.z)N (0.03y0.6 and 0z0.05 in an atomic ratio). An X-ray diffraction peak of a (200) plane is present at a position of a diffraction angle of 43.6 plus or minus 0.1 degrees, and a plastic deformation work ratio of the B layer is 0.35 to 0.50.

In an embodiment, a cutting insert includes an upper surface, a one or more side surfaces, and a cutting edge. The upper surface includes a first corner portion, and a first side that is adjacent to the first corner portion. The side surfaces are adjacent to the upper surface. The cutting edge is disposed on at least a portion of a section where the upper surface and the side surfaces intersect. The cutting edge includes first, second, third and fourth cutting edges. The first cutting edge is disposed at the first corner portion and has a convex curved shape. The second cutting edge is next to the first cutting edge, and has a linear shape. The third cutting edge is next to the second cutting edge, and has a convex curved shape. The fourth cutting edge is next to the third cutting edge on the first side.

The present disclosure relates to a cutting tool of a cemented carbide substrate including WC and a binder phase having one or more of Co, Fe and Ni, wherein the cemented carbide also includes a finely dispersed eta phase of Me12C and/or Me6C carbides, where Me is one or more metals selected from W, Mo and the binder phase metals, wherein the substoichiometric carbon content in the cemented carbide is between 0.30 to 0.16 wt %. The disclosed cutting tool will achieve an improved resistance against comb cracks.

A cutting tool according to one aspect of the present disclosure includes an attaching portion, a cutting portion having a core portion and a surface portion, and a joint portion. The attaching portion includes a hard component and a hard material. The hard component is at least one selected from the group consisting of TiC, TiCN, W, WC, Al.sub.2O.sub.3, and a combination of at least one of CBN and diamond and at least one of W and WC. The hard material includes one or two or more types of iron group elements, and has a Young's modulus of not more than 350 GPa. The core portion includes a cemented carbide material. The surface portion includes PCD or CBN. The cutting portion has a chamfer portion. The surface portion includes a groove, a flank face, and a cutting edge. The cutting edge extends toward the attaching portion.

A cutting insert according to an aspect includes a top surface and a side surface. At least a part of a ridge line where the top surface and the side surface intersects is a cutting edge. The cutting edge includes a first portion located at a corner portion, a second portion adjacent to the first portion, a third portion close to the second portion, a fourth portion close to the third portion, and a fifth portion adjacent to the fourth portion. When viewed from directly above, a curvature radius of the second portion is less than a curvature radius of the first portion, a curvature radius of the third portion is greater than the curvature radius of the first portion, and a curvature radius of the fourth portion is less than the curvature radius of the third portion.

A cutting edge tip of a cubic boron nitride sintered body has improved joint strength to a substrate of a cemented carbide. A cutting edge tip of a cubic boron nitride sintered body has improved crater wear resistance. A tool 10 of the present invention includes a substrate 12 of a cemented carbide and a cutting edge tip 14 of a cubic boron nitride sintered body joined to the substrate 12. The cutting edge tip 14 has a thickness covering an upper surface 12a to a lower surface 12b of the substrate 12. The cubic boron nitride sintered body contains 50 volume % or more and 95 volume % or less of cubic boron nitride and 5 volume % or more and 50 volume % or less of a binder phase. The cubic boron nitride has an average grain size of 1.0 m or more and 6.0 m or less.

A surface-coated titanium carbonitride-based cermet cutting tool is a surface-coated TiCN-based cermet cutting tool in which a Ti compound layer that is a hard coating layer is deposited as a first layer on the surface of a TiCN-based cermet body containing W and Mo, and a Mo-enriched layer having an average thickness of 0.5 to 10 nm is formed at an interface between a TiCN phase of the body and the hard coating layer.

A surface-coated cutting tool includes a base material and a coating formed on the base material. The coating includes an -Al.sub.2O.sub.3 layer. The -Al.sub.2O.sub.3 layer contains -Al.sub.2O.sub.3 crystal grains and sulfur, and has a TC(006) of more than 5 in texture coefficient TC(hkl). The sulfur has a concentration distribution in which a concentration of the sulfur decreases in a direction away from a base-material-side surface of the -Al.sub.2O.sub.3 layer, in a thickness direction of the -Al.sub.2O.sub.3 layer.

In an embodiment, a cutting insert includes an upper surface, a one or more side surfaces, and a cutting edge. The upper surface includes a first corner portion, and a first side that is adjacent to the first corner portion. The one or more side surfaces are adjacent to the upper surface. The cutting edge is disposed on at least a portion of a section where the upper surface and the side surfaces intersect. When viewed from directly above, the cutting edge includes first, second, third and fourth cutting edges. The first cutting edge is disposed at the first corner portion and has a convex curved shape. The second cutting edge is next to the first cutting edge, and has a linear shape. The third cutting edge is next to the second cutting edge, and has a convex curved shape. The fourth cutting edge is next to the third cutting edge on the first side.

A coated cutting tool includes a substrate having a rake side, a clearance side and a cutting edge and a coating comprising a first layer and a second layer. The second layer has a sandwich structure of an inner layer, an intermediate layer and an outer layer, wherein the inner layer is exposed through an opening in the outer layer, the opening extending over at least a portion of the width of the cutting edge. Thereby, a double layer is provided in critical areas, whereas a single layer is provided in other areas. The double oxide layer is an aluminum oxide layer. A method for manufacturing the coated cutting tool is also provided.