A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A coated tool in the present disclosure includes a base and a coating layer located on a surface of the base. The coating layer includes an intermediate layer including Ti, and an Al.sub.2O.sub.3 layer. The Al.sub.2O.sub.3 layer is located in contact with the intermediate layer at a position further away from the base than the intermediate layer. The intermediate layer includes a plurality of first protrusions protruding toward the Al.sub.2O.sub.3 layer. An average distance between the plurality of first protrusions is 70-120 nm. A cutting tool in the present disclosure includes a holder which is extended from a first end toward a second end and includes a pocket on a side of the first end, and the coated tool located in the pocket.

A coated cutting tool is provided. The cutting tool is CVD coated and has a substrate of cemented carbide, wherein a metallic binder in the cemented carbide includes Ni. The CVD coating has an inner layer of TiN and a subsequent layer of TiCN and a layer of Al.sub.2O.sub.3 located between the TiCN layer and an outermost surface of the coated cutting tool.

A coated tool in the present disclosure includes a base and a coating layer located on a surface of the base. The coating layer includes a TiCN layer, an intermediate layer including Ti, and an Al.sub.2O.sub.3 layer in this order from a side of the base. The Al.sub.2O.sub.3 layer is located in contact with the intermediate layer at a position further away from the base than the intermediate layer. The intermediate layer includes a plurality of first protrusions protruding toward the Al.sub.2O.sub.3 layer. An average area of the plurality of first protrusions is 1700 nm.sup.2 or less. A cutting tool in the present disclosure includes a holder which is extended from a first end toward a second end and includes a pocket on a side of the first end, and the coated tool located in the pocket.

The present invention relates to a cutting tool, which performs, like a drill or a ball end mill, cutting while rotating in a state in which the center of the tip end is in contact with a work material, and includes a wear-resistant layer formed at the tip end thereof, wherein a portion of the wear-resistant layer is selectively removed through tip end polishing from the center of the tip end of the drill or the ball end mill to a predetermined area, so as to restrain micro-brittle wear generated in an ultra-low speed region, and thus remarkably improving the cutting lifespan of the cutting tool such as the drill or the ball end mill.

A cutting insert of a substantially horizontal cylindrical segment shape may include top and bottom surfaces having a circular segment shape. The cutting insert may include a convex side and a flat side. The cutting insert may include a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert may include a hole extending from the convex side towards the flat side. The hole may be positioned at a center of a surface of the flat side.

A coated cutting tool includes a substrate of cemented carbide and a coating. The cemented carbide is made of WC and a binder phase of one or more of Co, Fe and Ni. The carbon content in the cemented carbide is a substoichiometric carbon content SCC, wherein −0.13 wt %≤SCC<0 wt %, or −0.30 wt %≤SCC≤−0.16 wt %. The coating includes one or more layers being a metal carbide, metal nitride or metal carbonitride, the metal being at least one of Zr and Hf, and wherein Ti is present in an amount of at most 10 at-% of the amount metal. The one or more layers is situated between the substrate and the aluminum oxide layer.

A cutting blade having a plurality of different coatings on surfaces thereof, including an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, wherein the upper surface intersects the side surface to form at least one cutting edge unit, the cutting edge unit includes a main cutting edge and a secondary cutting edge, the upper surface includes at least one set of cutting planes, the cutting planes include a main cutting surface and a secondary cutting surface, the main cutting surface intersects the side surface to form the main cutting edge, the secondary cutting surface intersects the side surface to form the secondary cutting edge, a main coating is provided on the main cutting surface, a secondary coating is provided on the secondary cutting surface, and the main coating and the secondary coating are independent from each other.

A surface-coated cutting tool has a hard coating layer including an upper layer α, an adhesion layer β, and a lower layer γ. The upper layer α is formed of an α-Al.sub.2O.sub.3 layer formed under low temperature conditions. The adhesion layer β includes a TiCN layer having a thickness of 0.5 μm or more in an outermost layer and contains 0.5 to 3 μm to a maximum depth of 0.5 μm toward the inside in a layer thickness direction of the TiCN layer from the interface between the TiCN layer and the upper layer α. The lower layer γ is formed of (Ti.sub.1-XAl.sub.X)(C.sub.YN.sub.1-Y) of a single phase of a NaCl type face-centered cubic structure, in which an average content ratio X.sub.avg of Al and an average content ratio Y.sub.avg of C in this composition formula satisfy 0.60≤X.sub.avg≤0.95 and 0≤Y.sub.avg≤0.005.

Provided is a ceramic sintered body having high wear resistance and chipping resistance. Also provided are an insert, a cutting tool and a friction stir welding tool, each of which uses such a high-performance ceramic sintered body. The ceramic sintered body includes Al.sub.2O.sub.3 (alumina), WC (tungsten carbide) and ZrO.sub.2 (zirconia), wherein Zr (zirconium) element is present at either one or both of: (1) a grain boundary between crystal grains of the Al.sub.2O.sub.3; and (2) a grain boundary of crystal grains of the Al.sub.2O and crystal grains of the WC, wherein the ceramic sintered body contains 55.0 to 97.5 vol % of the WC, 0.1 to 18.0 vol % of the ZrO.sub.2, and the balance being the Al.sub.2O.sub.3, and wherein the ZrO.sub.2 is in a phase of tetragonal structure (T) or a mixed phase of tetragonal structure (T) and monoclinic structure (M).