A cutting tool includes: a substrate; and a coating film disposed on the substrate, wherein the coating film includes an α-Al.sub.2O.sub.3 layer, the α-Al.sub.2O.sub.3 layer includes a plurality of α-Al.sub.2O.sub.3 crystal grains, and has a TC(006) of more than 5 in texture coefficient TC(hkl), and an elastic modulus E1 of the α-Al.sub.2O.sub.3 layer at a room temperature and an elastic modulus E2 of the α-Al.sub.2O.sub.3 layer at 800° C. represent a relation of the following expression B-1:

0<{(E1−E2)/E1}×100<10  Expression B-1.

A cutting tool includes: a substrate; and a coating film disposed on the substrate, wherein the coating film includes an α-Al.sub.2O.sub.3 layer, the α-Al.sub.2O.sub.3 layer includes a plurality of α-Al.sub.2O.sub.3 crystal grains, and has a TC (006) of more than 5 in texture coefficient TC (hkl), and a plastic deformation amount hp of the α-Al.sub.2O.sub.3 layer at 800° C. is 0 nm or more and 100 nm or less.

A cutting tool includes: a substrate; and a coating film disposed on the substrate, wherein the coating film includes an α-Al.sub.2O.sub.3 layer, the α-Al.sub.2O.sub.3 layer includes a plurality of α-Al.sub.2O.sub.3 crystal grains, and has a TC(006) of more than 5 in texture coefficient TC(hkl), and a hardness H1 of the α-Al.sub.2O.sub.3 layer at a room temperature and a hardness H2 of the α-Al.sub.2O.sub.3 layer at 800° C. represent a relation of the following expression A-1:

0<{(H1−H2)/H1}×100<60   Expression A-1.

A cutting tool includes a substrate and a coated film arranged on the substrate. The coated film includes a first layer. The first layer includes a plurality of crystal grains. The crystal grains are composed of Al.sub.xTi.sub.1−xC.sub.yN.sub.1−y, wherein x is more than 0.65 and less than 0.95, and y is not less than 0 and less than 0.1. In a first region, the crystal grains have an average aspect ratio of not more than 3.0. In a second region, the crystal grains have an average aspect ratio of more than 3.0 and not more than 10.0. The crystal grains include crystal grains having a cubic crystal structure. The first layer has a ratio of an area occupied by the crystal grains having a cubic crystal structure of not less than 90%. The first layer has a thickness of not less than 2 m and not more than 20 m.

A bore cutting tool for cutting metal workpieces includes a tool substrate and a tool coating on a surface of the tool substrate. The bore cutting tool includes a plurality of pits in the surface of the tool substrate and wherein the tool coating extends over the pits such that the pit surface includes the tool coating. In this way, the pit dimensions can be retained over prolonged tool life and the pits, with their coated surface, are particularly effective at retaining lubricant so that the thickness of a lubricant film can be increased as compared to a tool without the coated pits. In the embodiments, the pits are formed by laser etching and are present only on the cylindrical land. Average pit depth is suitably in the range 8 μm to 25 μm, average pit width and pit length is independently selected from 40 μm to 250 μm and average pit density may be 20 to 30 pits/mm.sup.2.

A cutting tool includes: a substrate; a hard layer provided on the substrate; and a titanium carbonitride layer provided on the hard layer, wherein a thickness of the titanium carbonitride layer is more than or equal to 2 μm, a hardness of the titanium carbonitride layer at a room temperature is more than or equal to 35 GPa, and a Young's modulus of the titanium carbonitride layer at the room temperature is less than or equal to 650 GPa.

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.

A surface-coated cutting tool comprises a tool substrate comprising a cBN sinter and a hard coating layer including a lower sublayer α and an upper sublayer β on the surface of the cutting edge; wherein α satisfies (Al.sub.1-xTi.sub.x)N (0.40≤x≤0.60); β satisfies (Al.sub.1-y-zTi.sub.yB.sub.z)N (0.40≤y≤0.60 and 0.01≤z≤0.10); in the sublayer β, the variation in the concentration of the B component is repeated; the average Bmaxav of the maxima in the concentration of the B component satisfies z<Bmaxav≤2.0×z, and the average Bminav of the minima in the concentration of the B component satisfies 0≤Bminav<z; and the average thickness tα of α and the average thickness tβ of β satisfy expression: 2.0≤<tβ/tα≤6.0; and the residual stress σ of the overall hard coating layer satisfies −2.0 GPa≤σ≤−0.5 GPa.

A coated tool in a non-limiting embodiment of the present disclosure includes a base and a coating film located on the base. The coated tool includes a first surface, a second surface adjacent to the first surface, and a cutting edge located on at least a part of a ridge part of the first surface and the second surface. The coating film includes an AlTiN film including Ti, Al and N. A first Al ratio and a second Al ratio are 0.7 or more. The first Al ratio is Al/(Al+Ti) at a point located 0.1 mm away from the cutting edge, and the second Al ratio is Al/(Al+Ti) at a point located 0.2 mm away from the cutting edge in the first surface. The second Al ratio is larger than the first Al ratio.

A coated cutting tool is provided which allows for satisfactory machining over a long period of time, particularly in the machining of difficult-to-machine materials with low thermal conductivity. The coated cutting tool includes a substrate and a coating layer formed on a surface of the substrate, wherein: at least one layer of the coating layer comprises a predetermined layer containing a compound having a composition represented by the formula: (Al.sub.XTi.sub.1-X)N [wherein x denotes an atomic ratio of the Al element based on a total of the Al element and the Ti element, and x satisfies 0.60≤x≤0.85]; a value of an orientation index TC (311) of a cubic (311) plane of the predetermined layer is from 2.5 or more to 4.2 or less; and an average thickness of the predetermined layer is from 1.0 μm or more to 12.0 μm or less.