A coated cutting tool has a substrate and a coating layer. At least one layer of the coating layer is a coarse grain layer with an average layer thickness of 0.2 to 10 μm and an average grain diameter in excess of 200 nm measured at the direction parallel to the interface of the coating layer. A composition of the layer is represented by (Al.sub.aTi.sub.bM.sub.c)X, wherein M represents at least one of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Y, B and Si, X represents at least one of C, N and O, and a, b and c represents atomic ratios of Al, Ti and M relative to one another such that 0.30≦a≦0.65, 0.35≦0.70, 0≦c≦0.20 and a+b+c=1.

A coated cutting tool includes a substrate and a coating layer formed onto the surface of the substrate. The coating layer contains an outermost layer. The outermost layer contains NbN. The NbN contains cubic NbN and hexagonal NbN. When a peak intensity at a (200) plane of cubic NbN is made I.sub.c, a peak intensity at a (101) plane of the hexagonal NbN is made I.sub.h1, and a sum of peak intensities at a (103) plane and a (110) plane of the hexagonal NbN is made I.sub.h2 in X-ray diffraction analysis, a ratio [I.sub.h1/(I.sub.h1+I.sub.c)] of I.sub.h1 based on a sum of I.sub.c and I.sub.h1 is 0.5 or more and less than 1.0, and a ratio [I.sub.h1/(I.sub.h1+I.sub.h2)] of I.sub.h1 based on a sum of I.sub.h1 and I.sub.h2 is 0.5 or more and 1.0 or less.

A coated cutting tool has a substrate and a coating layer formed onto a surface of the substrate. The coating layer contains a hard layer of a composition represented by (Ti.sub.xM.sub.1-x)N, wherein M represents at least one kind of an element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si and Y, and x represents an atomic ratio of a Ti element based on a sum of the Ti element and an M element, and satisfies 0.45≦x≦0.9. Also, an average grain size of grains constituting the hard layer is 200 nm or more and 600 nm or less, and the grains of the hard layer satisfy predetermined conditions.

A cutting tool includes a base body and a coating applied thereto. For providing a cutting tool, having both a hard coating that also exhibits fracture toughness, the coating includes at least one oxide layer deposited in the PVD process, consisting of at least 10 alternating single coats of Al.sub.2O.sub.3 and (Al.sub.x, Me.sub.1-x).sub.2O.sub.3, where 0<x<1, wherein Me is selected from one or more of the group of Si, Ti, V, Zr, Mg, Fe, B, Gd, La and Cr.

A coated cutting tool includes a substrate of cemented carbide, cermet, ceramics, steel or cubic boron nitride and a multi-layered wear resistant coating. The multi-layered wear resistant coating has a total thickness from 5 to 25 μm and includes refractory coating layers deposited by chemical vapour deposition (CVD) or moderate temperature chemical vapour deposition (MT-CVD). The multi-layered wear resistant coating has at least one pair of layers (a) and (b), with layer (b) being deposited immediately on top of layer (a). Layer (a) is a layer of aluminium nitride having hexagonal crystal structure (h-AlN) and a thickness from 10 nm to 750 nm. Layer (b) is a layer of titanium aluminium nitride or titanium aluminium carbonitride represented by the general formula Ti.sub.1-xAl.sub.xC.sub.yN.sub.z with 0.4≤x≤0.95, 0≤y≤0.10 and 0.85≤z≤1.15, having a thickness from 0.5 μm to 15 μm, and at least 90% of the Ti.sub.1-xAl.sub.xC.sub.yN.sub.z of layer (b) has a face-centered cubic (fcc) crystal structure.

The hard coating layer includes at least a complex nitride or carbonitride layer (2) expressed by a composition formula: (Ti.sub.1-x-yAl.sub.xMe.sub.y)(C.sub.zN.sub.1-z), Me being an element selected from Si, Zr, B, V, and Cr. The average content ratio X, the average content ratio Y, and the average content ratio Z satisfy 0.60≦x.sub.avg, 0.005≦y.sub.avg≦0.10, 0≦z.sub.avg≦0.005, and 0.605≦x.sub.avg+y.sub.avg≦0.95. There are crystal grains having a cubic structure in the crystal grains constituting the complex nitride or carbonitride layer (2). A predetermined periodic content ratio change of Ti, Al and Me exists in the crystal grains having the cubic structure.

A surface-coated cutting tool includes a base material and a coating formed on the base material. The coating includes an α-Al.sub.2O.sub.3 layer. The α-Al.sub.2O.sub.3 layer contains a plurality of α-Al.sub.2O.sub.3 crystal grains and a plurality of κ-Al.sub.2O.sub.3 crystal grains, and has a TC(006) of more than 5 in a texture coefficient TC(hkl). A ratio of C.sub.κ to a sum of C.sub.α and C.sub.κ: [C.sub.κ/(C.sub.α+C.sub.κ)×100](%) is 0.05 to 7%, where C.sub.α is a total number of peak counts of the α-Al.sub.2O.sub.3 crystal grains obtained from measurement data of x-ray diffraction for the coating, and C.sub.κ is a total number of peak counts of the κ-Al.sub.2O.sub.3 crystal grains obtained from the measurement data of the x-ray diffraction for the coating.

A cutting tool comprises a substrate and a coating layer provided on the substrate, the coating layer including a multilayer structure layer composed of a first unit layer and a second unit layer, and a lone layer, the lone layer including cubic Ti.sub.zAl.sub.1-zN crystal grains, an atomic ratio z of Ti in the Ti.sub.zAl.sub.1-zN being 0.5 or more and 0.65 or less, the lone layer having a thickness with an average value of 2.5 nm or more and 10 nm or less, the multilayer structure layer having a thickness with an average value of 10 nm or more and 95 nm or less, one multilayer structure layer and one lone layer forming a repetitive unit having a thickness with an average value of 30 nm to 70 nm, a maximum value of 40 nm to 100 nm, and a minimum value of 20 nm to 40 nm.

A surface-coated cutting tool includes a base material and a coating formed on the base material. The coating includes an α-Al.sub.2O.sub.3 layer containing a plurality of α-Al.sub.2O.sub.3 crystal grains. The α-Al.sub.2O.sub.3 layer includes a lower layer portion disposed at a side of the base material, an intermediate portion disposed on the lower layer portion, and an upper layer portion disposed on the intermediate portion. In a crystal orientation mapping performed on a polished cross-sectional surface of the α-Al.sub.2O.sub.3 layer using an EBSD, an area ratio of α-Al.sub.2O.sub.3 crystal grains with (001) orientation in the lower layer portion is less than 35%, an area ratio of α-Al.sub.2O.sub.3 crystal grains with (001) orientation in the intermediate portion is 35% or more, and an area ratio of α-Al.sub.2O.sub.3 crystal grains with (001) orientation in the upper layer portion is less than 35%.

A surface-coated cutting tool includes a base material and a coating formed on the base material. The coating includes an α-Al.sub.2O.sub.3 layer containing a plurality of α-Al.sub.2O.sub.3 crystal grains. The α-Al.sub.2O.sub.3 layer includes: a first region made up of an edge ridgeline, a region A of a rake face, and a region B of a flank face; a second region which is a region of the rake face except for the region A and covered with the coating; and a third region which is a region of the flank face except for the region B. The α-Al.sub.2O.sub.3 layer satisfies a relation b−a>0.5, where a is an average value of a TC(006) in the first region in texture coefficient TC(hkl) and b is an average value of the TC(006) in the second region or the third region in texture coefficient TC(hkl).