A coated cutting tool having a substrate and a coating is provided. The coating includes an inner α-Al.sub.2O.sub.3-multilayer and an outer α-Al.sub.2O.sub.3-single-layer. The thickness of the inner α-Al.sub.2O.sub.3-multilayer is less than or equal to 35% of the sum of the thickness of the inner α-Al.sub.2O.sub.3-multilayer and the thickness of the outer α-Al.sub.2O.sub.3-single-layer. The sum of the thickness of the inner α-Al.sub.2O.sub.3-multilayer and the outer α-Al.sub.2O.sub.3-single-layer is 2-15 μm. The inner α-Al.sub.2O.sub.3-multilayer consists of alternating sublayers of α-Al.sub.2O.sub.3 and sublayers of TiCO, TiCNO, AlTiCO or AlTiCNO. The inner α-Al.sub.2O.sub.3-multilayer can include at least 5 sublayers of α-Al.sub.2O.sub.3.

A coated tool of the present disclosure may include a base and a coating layer covering at least a part of the base. The base may include a hard phase of a carbonitride including Ti and a binder phase including at least one of Co and Ni and has a thermal expansion coefficient at 25 to 1000° C. of 9.0×10.sup.−6/° C. or more. The coating layer may include a TiCN layer and an Al.sub.2O.sub.3 layer positioned on the TiCN layer. The TiCN layer may have a compressive stress of 250 to 500 MPa. The Al.sub.2O.sub.3 layer may have a thickness of 2 μm or more and a compressive stress of 450 MPa or more, and the value of the compressive stress is greater than the compressive stress of the TiCN layer.

A surface-coated cutting tool comprises a hard coating layer that includes a TiAlN layer and is provided on a surface of a cutting tool body. In case the composition of the TiAlN layer is expressed by a formula: (Ti.sub.xAl.sub.1-x)N, 0.10≤x≤0.35 (here, x is in atomic ratio) is satisfied. In the TiAlN layer, a high Ti band-like region is present in a direction at 30 degrees or less with respect to a line normal to the surface of the cutting tool body. An average composition X of the Ti component in the high Ti band-like region satisfies (x+0.01)≤X≤(x+0.05), an average width W of the high Ti band-like region is 30 to 500 nm, and an average area ratio St of the high Ti band-like region is 3 to 50 area %.

The present disclosure relates to a method of treating a cutting tool of a cemented carbide or cermet substrate, wherein the cutting tool is subjected to shot peening at a temperature of or above 100° C. The cutting tool typically has a rake face, a flank face and a cutting edge extending therebetween. The shot peening is performed at least on the rake face of the cutting tool. The present disclosure also relates to a cutting tool treated with the method.

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, the lower layer, the intermediate layer and the upper layer being laminated in order from the substrate side toward a surface side of the coating layer; the lower layer comprises a Ti compound layer; the intermediate layer contains α-Al.sub.2O.sub.3; the upper layer contains TiCN; an average thickness of each of the lower layer, the intermediate layer, and the upper layer is within a specific range; a ratio of a length of Σ3 grain boundaries to a total 100% length of all grain boundaries in a specific region of the upper layer is from 20% or more to 60% or less; and a ratio of (111)-oriented grains in the upper layer is 30 area % or more.

A cutting tool including a rake face, a flank face, and a cutting edge portion, comprising a substrate and an AlTiN layer, the AlTiN layer including cubic Al.sub.xTi.sub.1-xN crystal grains, Al having an atomic ratio x of 0.7 or more and less than 0.95, the AlTiN layer including a central portion, the central portion at the rake face being occupied in area by (111) oriented Al.sub.xTi.sub.1-xN crystal grains at a ratio of 50% or more and less than 80%, the central portion at the cutting edge portion being occupied in area by (111) oriented Al.sub.xTi.sub.1-xN crystal grains at a ratio of 80% or more.

A cutting tool comprising a base material and a coating, wherein the coating includes a first layer having a multilayer structure in which a first unit layer and a second unit layer are alternately stacked; a thickness of the first unit layer is 2 to 50 nm; a thickness of the second unit layer is 2 to 50 nm; a thickness of the first layer is 1.0 m or more and 20 m or less, the first unit layer is composed of Ti.sub.aAl.sub.bB.sub.cN, and the second unit layer is composed of Ti.sub.dAl.sub.eB.sub.fN, wherein 0.49a0.70, 0.190.40, 0.10<c0.20, a+b+c=1.00, 0.39d0.60, 0.29e0.50, 0.10<f0.20, d+e+f=1.00, 0.05ad0.20, and 0.05eb0.20 are satisfied, and a percentage of the number of atoms of titanium to the total number of atoms of titanium, aluminum and boron is 45% or more in the first layer.

A cutting tool comprising a base material and a coating, wherein the coating includes a first layer having a multilayer structure in which a first unit layer and a second unit layer; a thickness of the first unit layer is 2 nm or more and less than 50 nm; a thickness of the second unit layer is 2 nm or more and less than 50 nm; a thickness of the first layer is 1.0 m or more and 20 m or less, the first unit layer is Ti.sub.aAl.sub.bB.sub.cN, and the second unit layer is Ti.sub.dAl.sub.eB.sub.fN, wherein 0.54a0.75, 0.24b0.45, 0<c0.10, a+b+c=1.00, 0.44d0.65, -.34e0.55, 0<f0.10, d+e+f=1.00, 0.05ad0.20, and 0.05eb0.20 are satisfied, and a percentage of the number of atoms of titanium to the total number of atoms of titanium, aluminum and boron is 50% or more in the first layer.

A coated cutting tool includes a substrate with a coating having a total thickness of 0.25-30 m. 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 m arranged between the substrate and the second layer, and wherein the second layer is a Cr layer.

A surface-coated cutting tool includes a base material and a coating. A hard layer in the coating includes a plurality of crystal grains having a sodium chloride-type crystal structure. The crystal grain has a layered structure in which a first layer composed of nitride or carbonitride of Al.sub.xTi.sub.1-x and a second layer composed of nitride or carbonitride of Al.sub.yTi.sub.1-y are alternately stacked. The total thickness of the first layer and the second layer adjacent to each other is 3 nm or more and 40 nm or less. An angle of intersection between a normal direction to (111) plane that is a crystal plane of the crystal grain and the normal direction to the surface of the base material, an area ratio of the crystal grains having the angle of intersection of 0 degree or more to less than 10 degrees is 40% or more.