Provided is a coated cutting tool having improved wear resistance and fracture resistance and a prolonged tool life. The coated cutting tool includes a substrate and a coating layer formed on the substrate. The coating layer includes a first layer containing Ti(C.sub.x1N.sub.1-x1) and a second layer containing (Ti.sub.1-y1Al.sub.y1)N, particles in the first layer have an average particle size of 5 nm or more and less than 100 nm, 1.0≤I(111)/I(200)≤20.0 in the first layer, the first layer has an average thickness of 5 nm or more and 1.0 μm or less, 0.1≤I(111)/I(200)≤1.0 in the second layer, particles in the second layer have an average particle size of more than 100 nm and 300 nm or less, and the second layer has an average thickness of 5 nm or more and 2.0 μm or less.

A cemented carbide includes a first hard phase, a second hard phase, and a binder phase, wherein the first hard phase is composed of tungsten carbide grains, the second hard phase is composed of carbide grains including niobium or tantalum as a constituent element, the binder phase includes cobalt, nickel, and chromium as constituent elements, at least part of the carbide grains further include tungsten as a constituent element, and when a volume ratio of the second hard phase to the cemented carbide is represented by A volume % and a volume ratio of a total of a niobium element and a tantalum element to the cemented carbide is represented by B volume %, a ratio A/B of A to B is more than 1.2.

A cemented carbide includes a first hard phase, a second hard phase, and a binder phase, wherein the first hard phase is composed of tungsten carbide grains, the second hard phase is composed of carbide grains including niobium or tantalum as a constituent element, the binder phase includes cobalt, nickel, and chromium as constituent elements, at least part of the carbide grains further include tungsten as a constituent element, and when a volume ratio of the second hard phase to the cemented carbide is represented by A volume % and a volume ratio of a total of a niobium element and a tantalum element to the cemented carbide is represented by B volume %, a ratio A/B of A to B is more than 1.2.

A coated tool may include a base member and a coating layer located on the base member. The coating layer may include an alternating layer having first layers and second layers. The first layers may contain (Ti.sub.bNb.sub.dM.sub.e)C.sub.xN.sub.1-x (where M is one or more kinds selected from metals of Groups 4, 5 and 6 in the periodic table except for Ti and Nb, and Al, 0.2≤b≤0.8, 0.01≤d≤0.2, 0≤e≤0.7, b+d+e=1 and 0<x<1). The second layers may contain M′N (where M′ is metal of Groups 4, 5 and 6 in the periodic table except for Nb).

A coated tool may include a base member and a coating layer located on the base member. The coating layer may include an alternating layer having first layers and second layers. The first layers may contain (Ti.sub.bNb.sub.dM.sub.e)C.sub.xN.sub.1-x (where M is one or more kinds selected from metals of Groups 4, 5 and 6 in the periodic table except for Ti and Nb, and Al, 0.2≤b≤0.8, 0.01≤d≤0.2, 0≤e≤0.7, b+d+e=1 and 0<x<1). The second layers may contain M′N (where M′ is metal of Groups 4, 5 and 6 in the periodic table except for Nb).

Provided is a coated cutting tool that has a nitride hard coating that contains Ti at 70 at % to 95 at % and Si at 5 at % to 30 at % with respect to the total amount of metallic elements, and Ar at 0.05 at % to 0.20 at % with respect to the total amount of metallic and non-metallic elements, has a NaCl-type crystalline structure, exhibits maximum diffraction peak intensity in the (200) plane, and has an average grain size of 5 nm to 30 nm. When 100 at % is defined as the total of content rates of the metallic elements, nitrogen, oxygen, and carbon in a composition at intervals of 20 nm from a depth of 20 nm to 200 nm from a surface of the hard coating, the content rate of nitrogen is 50.0 at % or more.

Provided is a coated cutting tool that has a nitride hard coating that contains Ti at 70 at % to 95 at % and Si at 5 at % to 30 at % with respect to the total amount of metallic elements, and Ar at 0.05 at % to 0.20 at % with respect to the total amount of metallic and non-metallic elements, has a NaCl-type crystalline structure, exhibits maximum diffraction peak intensity in the (200) plane, and has an average grain size of 5 nm to 30 nm. When 100 at % is defined as the total of content rates of the metallic elements, nitrogen, oxygen, and carbon in a composition at intervals of 20 nm from a depth of 20 nm to 200 nm from a surface of the hard coating, the content rate of nitrogen is 50.0 at % or more.

An object of the invention is to provide a coated cutting tool whose tool life can be extended by having excellent wear resistance and fracture resistance. The coated cutting tool includes: a substrate; and a coating layer formed on a surface of the substrate, in which the coating layer includes a lower layer, an intermediate layer, and an upper layer in this order from a substrate side to a surface side of the coating layer, the lower layer includes one or more Ti compound layers formed of a specific Ti compound, the intermediate layer contains TiCNO, TiCO, or TiAlCNO, the upper layer contains α-type Al.sub.2O.sub.3, an average thickness of the lower layer is 2.0 μm or more and 8.0 μm or less, an average thickness of the intermediate layer is 0.5 μm or more and 2.0 μm or less and is 10% or more and 20% or less of a thickness of the entire coating layer, an average thickness of the upper layer is 0.8 μm or more and 6.0 μm or less, and in the intermediate layer, a ratio of a length of CSL grain boundaries to a total length 100% of a total grain boundary is 20% or more and 60% or less.

A coated cutting tool comprising a substrate comprising a cubic boron nitride sintered body and a coating layer formed on the substrate, wherein the coating layer comprises a Ti carbonitride layer comprising Ti(C.sub.xN.sub.1-x); an average thickness of the Ti carbonitride layer is 0.5 μm or more and 5.0 μm or less; in the Ti carbonitride layer, R75 is higher than R25; in the Ti carbonitride layer, a texture coefficient TC (111) of a (111) plane is 1.0 or more and 2.0 or less; and in X-ray diffraction measurement of the Ti carbonitride layer, an absolute value of a difference between a maximum value and a minimum value of 2θ is 0.1° or less on the (111) plane when the measurement is performed at each of ψ angles of 0°, 30°, 50° and 70°.

A coated cutting tool comprising a substrate comprising a cubic boron nitride sintered body and a coating layer formed on the substrate, wherein the coating layer comprises a Ti carbonitride layer comprising Ti(C.sub.xN.sub.1-x); an average thickness of the Ti carbonitride layer is 0.5 μm or more and 5.0 μm or less; in the Ti carbonitride layer, R75 is higher than R25; in the Ti carbonitride layer, a texture coefficient TC (111) of a (111) plane is 1.0 or more and 2.0 or less; and in X-ray diffraction measurement of the Ti carbonitride layer, an absolute value of a difference between a maximum value and a minimum value of 2θ is 0.1° or less on the (111) plane when the measurement is performed at each of ψ angles of 0°, 30°, 50° and 70°.