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 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 S.sub.2 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 comprising a base material and a coating arranged on the base material; wherein: the coating comprises an α-Al.sub.2O.sub.3 layer composed of a plurality of α-Al.sub.2O.sub.3 particles; the average particle diameter a of the α-Al.sub.2O.sub.3 particles in a first region of the α-Al.sub.2O.sub.3 layer is 0.10 μm or more and 0.30 μm or less; the average particle diameter b of the α-Al.sub.2O.sub.3 particles in a second region of the α-Al.sub.2O.sub.3 layer is 0.30 μm or more and 0.50 μm or less; the average particle diameter c of the α-Al.sub.2O.sub.3 particles in a third region of the α-Al.sub.2O.sub.3 layer is 0.10 μm or more and 0.30 μm or less; and the ratio b/a is 1.5 or more and 5.0 or less.

A coated cutting tool comprising: a substrate and a coating layer, wherein the coating layer includes a lower layer and an upper layer; the lower layer includes one or two or more specific Ti compound layers; the upper layer includes an α-type Al.sub.2O.sub.3 layer; an average thickness of the lower layer is 2.0 μm to 15.0 μm; an average thickness of the upper layer is 3.5 μm to 15.0 μm; in the upper layer, a ratio of a length of Σ3 grain boundaries to a total length of 100% of a total grain boundary is more than 50% and 80% or less, and a ratio of the length of Σ3 grain boundaries to a total length of 100% of CSL grain boundaries is 70% or more; and in the upper layer, a texture coefficient TC(0,0,12) of the α-type Al.sub.2O.sub.3 layer is 8.0 or more and 8.9 or less.

A coated cutting tool includes a substrate and a coating. The coating has an inner layer of 4-14 μm thick Ti.sub.1-xAl.sub.xN, an intermediate layer of 0.05-1 μm TiCN and at least one outer layer of 1-9 μm α-Al.sub.2O.sub.3. The α-Al.sub.2O.sub.3 layer exhibits an X-ray diffraction pattern, as measured using CuKα radiation and theta-2theta scan. A texture coefficient TC(hkl) is defined according to Harris formula, wherein the (hkl) reflections used are (0 2 4), (1 1 6), (3 0 0) and (0 0 12), I(hkl)=measured intensity (peak intensity) of the (hkl) reflection, I0(hkl)=standard intensity according to ICDD's PDF-card No. 00-042-1468, n=number of reflections used in the calculation, and 3<TC(0 0 12)<4.

A coated cutting tool includes a substrate with a coating having a total thickness of 0.25-30 μm. The coating has a first layer and a second layer, the first layer being a wear resistant PVD deposited layer having a thickness of 0.2-15 μm arranged between the substrate and the second layer, and wherein the second layer is a Cr layer.

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 coated tool includes a base and a coating layer located on the base. The coating layer includes a first layer having a thickness of 1 μm or more located near the base, and a second layer including Al.sub.2O.sub.3 particles which is in contact with the first layer and is located more away from the base than the first layer. A difference (A2−A1) between an erosion ratio A2 in the second layer and an erosion ratio A1 in the first layer is 0.60 to −0.30 μm/g. The erosion ratio is obtained by collision of a liquid A in which 3 mass % of spherical Al.sub.2O.sub.3 particles having a mean particle diameter of 1.1-1.3 μm is dispersed in pure water. A cutting tool includes a holder which includes a pocket, and the coated tool located in the pocket.

A surface coated cutting tool comprises a base material and a coating layer that coats the base material, the coating layer including an alternate layer composed of a first unit layer and a second unit layer alternately stacked, the first unit layer being composed of a nitride containing aluminum and zirconium, in the first unit layer, when the total number of metal atoms constituting the first unit layer is represented as 1, a ratio thereto of the number of atoms of the zirconium being not less than 0.65 and not more than 0.95, the second unit layer being composed of a nitride containing titanium and aluminum, in the second unit layer, when the total number of metal atoms constituting the second unit layer is represented as 1, a ratio thereto of the number of atoms of the aluminum being larger than 0.40 and not more than 0.70.

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 and an upper layer in this order from the substrate side; the lower layer comprises one or more Ti compound layers containing a Ti compound of Ti and an element of at least one kind selected from the group consisting of C, N, O and B; and the intermediate layer comprises an α-Al.sub.2O.sub.3 layer containing α-Al.sub.2O.sub.3; and the upper layer comprises a TiCN layer containing TiCN; an average thickness of the coating layer is within a specific range, and an average thickness of the upper layer is within a specific range; in a cross section perpendicular to the surface of the substrate, the grains in the TiCN layer constituting the upper layer satisfies a specific condition.