[Problem]

To provide a coated cutting tool having excellent fracture resistance and thus allowing for the extension of tool life.

[Means for Resolution]

A covered cutting tool having a cemented carbide and a covering layer formed on the cemented carbide. The covered cutting tool includes a rake face, a flank face, and a cutting edge line part located between the rake face and the flank face. The coating layer includes a compound layer containing a compound having a composition represented by (Al.sub.xTi.sub.1-x)N. The average thickness T.sub.1 of the covering layer in the cutting edge line part and the average thickness T.sub.2 of the coating layer in the rake face at a position 2 mm or more away from the cutting edge line part toward the rake face are within specific ranges and satisfy T.sub.2 <T.sub.1. The residual stress S.sub.1 of the cemented carbide in the cutting edge line part and the residual stress S2 of the cemented carbide in the rake face at a position 2 mm or more away from the cutting edge line part toward the rake face satisfy S.sub.2 <S.sub.1.

A cutting tool includes a substrate and a hard layer, wherein the hard layer includes a first unit layer and a second unit layer being alternately layered in the hard layer, a thickness of the first unit layer is 2 to 100 nm, a thickness of the second unit layer is 2 to 100 nm, the first unit layer is composed of Ti.sub.aAl.sub.bB.sub.cN, the second unit layer is composed Ti.sub.dAl.sub.eB.sub.fN, an atomic ratio a satisfy 0.25≤a<0.45, an atomic ratio b satisfy 0.55≤b<0.75, an atomic ratio c satisfy 0<c≤0.1, a total of the atomic ratios a, b and c is 1, an atomic ratio d satisfy 0.35≤d<0.55, an atomic ratio e satisfy 0.45≤e<0.65, an atomic ratio f satisfy 0<f≤0.1, a total of the atomic ratios d, e and f is 1, the atomic ratios a and d satisfy 0.05≤d−a≤0.2, and the atomic ratios b and e satisfy 0.05≤b−e≤0.2.

The present invention relates to a cutting tool composed of a hard base material, such as cemented carbide, cermet, ceramic, and cubic boron nitride, and a hard coating film formed on the hard base material. A hard coating film for a cutting tool according to the present invention is formed in a multi-layered structure on a base material of a cutting tool, wherein the hard coating film includes one or more layers of a coating film made of an oxide and one or more layers of a coating film made of a nitride, and is characterized in that the O/(O+N) ratio in an edge center of the cutting tool is lower than the O/(O+N) ratio in a region 100 μm or further away from the edge center in the entire hard coating film.

A coated cutting tool including a substrate and a single layer or multi-layer hard material coating is provided. The substrate is selected from cemented carbide, cermet, ceramics, cubic boron nitride (cBN), polycrystalline diamond, steel or high-speed steel. The hard material coating includes at least one layer of gamma-Al.sub.2O.sub.3, exhibiting particularly high hardness and reduced Young's modulus. The gamma-Al.sub.2O.sub.3 layer of the coated cutting tool is obtainable by means of a reactive magnetron sputtering process using at least one Al target, wherein the deposition is carried out using a reaction gas composition of argon (Ar) and oxygen (O.sub.2) at a total reaction gas pressure within the range from at least 1 Pa to at most 5 Pa, at an O.sub.2 partial pressure within the range from 0.001 Pa to 0.1 Pa, and at a temperature within the range from 400° C. to 600° C.

A surface-coated cutting tool includes a substrate and a coating film that coats the substrate, wherein the coating film includes a WC.sub.1-x layer composed of a compound represented by WC.sub.1-x, where x is more than or equal to 0.54 and less than or equal to 0.58, and the compound represented by WC.sub.1-x includes a hexagonal crystal structure.

Provided is a cemented carbide having superior wear resistance and fracture resistance. A cemented carbide containing 50.0 mass % or more and 94.5 mass % or less of tungsten carbide, 5.0 mass % or more and 12.0 mass % or less of Co, and 0.5 mass % or more and 4.0 mass % or less of Ru, the cemented carbide comprising a WC phase that includes tungsten carbide as a main component, and a binder phase that binds the WC phase, wherein the binder phase contains Co, the lattice constant of Co in the binder phase is 3.580 Å or more and 3.610 Å or less, and the saturation magnetization of the cemented carbide is 40% or more and 58% or less.

A coated cutting tool of the present invention comprises a substrate and a coating layer formed on a surface of the substrate, wherein the coating layer comprises a lower layer and an upper layer formed on a surface of the lower layer, the lower layer comprises a specified Ti compound layer having a specified average thickness, the upper layer comprises an α-aluminum oxide layer having a specified average thickness, the Ti compound layer comprises at least one Ti carbonitride layer, the Ti carbonitride is composed of Ti(C.sub.xN.sub.1-x) (0.65<x≤0.90), and a texture coefficient TC(331) of a (331) plane in the Ti carbonitride layer satisfies a specified range.

In a vanadium nitride film formed on a surface of a base material, a ratio V [at %]/N [at %] between a vanadium element concentration and a nitrogen element concentration in the film is 1.08 or more and a chlorine element concentration in the film is 1 at % or more and 5 at % or less.

A coated cutting tool according to the present invention is a coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, wherein: the coating layer comprises a lower layer, an intermediate layer formed on a surface of the lower layer, and an upper layer formed on a surface of the intermediate layer; the lower layer is a predetermined Ti compound layer with a predetermined average thickness; the intermediate layer is an α-type aluminum oxide layer with a predetermined average thickness; the upper layer is a Ti carbonitride layer with a predetermined average thickness; and a texture coefficient of a predetermined plane of each of the α-type aluminum oxide layer and the Ti carbonitride layer falls within a predetermined range.

Provided is a coated cutting tool having a base material side single layer portion and a laminated portion provided as a hard coating in order from a base material side. The base material side single layer portion is formed of a nitride-based hard coating in which a proportion of Al is highest among metal (including metalloid) elements, a sum of Al and Cr in a content ratio (atomic ratio) is 0.9 or more, and at least B is contained. In the laminated portion, a nitride-based a layer in which a proportion of Ti is highest among metal (including metalloid) elements and at least B is contained, and a nitride-based b layer in which a proportion of Al is highest among metal (including metalloid) elements and at least Cr and B are contained are alternately laminated.