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 0.4 or more and less than 0.55, 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 45 nm or less, one multilayer structure layer and one lone layer forming a repetitive unit having a thickness with an average value of 20 nm to 50 nm, a maximum value of 40 nm to 60 nm, and a minimum value of 10 nm to 30 nm.

A surface-coated cutting tool includes a lower layer including a Ti compound layer, an intermediate layer including an α-Al.sub.2O.sub.3 layer, and an upper layer including a Zr-containing α-Al.sub.2O.sub.3 layer. The outermost layer of the lower layer contains 0.5 to 3 at % of oxygen. The frequencies of inclination angles between a normal line to a (0001) plane of Al.sub.2O.sub.3 grains of the intermediate layer and a normal line to a surface of a tool body have a highest peak in an inclination angle division of 0 to 10°. The ratio of the frequencies is 50 to 70%. The frequencies between the normal line to the (0001) plane of Al.sub.2O.sub.3 grains of the entirety of the intermediate and the upper layers and the normal line to the tool body surface have a highest peak in an inclination angle division of 0 to 10°. The ratio of the frequencies is 75% or more.

This surface-coated cutting tool includes a cutting tool body made of tungsten carbide-based cemented carbide and a hard coating layer deposited on a surface of the cutting tool body, in which the hard coating layer has at least one (Ti.sub.1-xAl.sub.x)N layer (0.4≦X≦0.7, X is an atomic ratio) with an average layer thickness of 0.5 to 10 μm, the (Ti, Al)N layer has a cubic crystal structure, and Ia−Ib<5 is satisfied when Ia (%) is an average absorptance of the hard coating layer at a wavelength of 400 to 500 nm and Ib (%) is an average absorptance of the hard coating layer at a wavelength of 600 to 700 nm.

A coated cutting tool includes a substrate of cemented carbide, cermet, ceramics, steel or cubic boron nitride, a multi-layered wear resistant coating and at least two refractory coating layers deposited. The at least two refractory coating layers include a first coating layer and a second coating layer deposited on top of each other. The first coating layer is titanium aluminium nitride or carbonitride Ti.sub.1-uAl.sub.uC.sub.vN.sub.w, with 0.2≦u≦1.0, 0≦v≦0.25 and 0.7≦w≦1.15 deposited by CVD. The second coating layer is titanium carbonitride Ti.sub.xC.sub.yN.sub.1-y, with 0.85≦x≦1.1 and 0.4≦y≦0.85, and is deposited on top of the first coating layer by MT-CVD. The second Ti.sub.xC.sub.yN.sub.1-y coating layer has a columnar grain morphology and the overall fiber texture of the Ti.sub.xC.sub.yN.sub.1-y coating layer is characterized by a texture coefficient TC (1 1 1)>2.

A coated tool is, for example, a cutting tool which is provided with a base material and a coating layer located on the base material, wherein a cutting edge and a flank surface are located on the coating layer, the coating layer has a portion in which at least a titanium carbonitride layer and an aluminum oxide layer having an a-type crystal structure are laminated in this order, and, with regard to a texture coefficient (Tc) (hkl) which is calculated on a basis of a peak of the aluminum oxide layer analyzed by an X-ray diffraction analysis, a texture coefficient (Tc1) (146) as measured from a surface side of the aluminum oxide layer in the flank surface is 1 or more.

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 0.4 or more and less than 0.55, 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 40 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 50 nm to 100 nm, a maximum value of 90 nm to 110 nm, and a minimum value of 40 nm to 60 nm.

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 0.55 or more and 0.7 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 45 nm or less, one multilayer structure layer and one lone layer forming a repetitive unit having a thickness with an average value of 20 nm to 50 nm, a maximum value of 40 nm to 60 nm, and a minimum value of 10 nm to 30 nm.

A cubic boron nitride sintered body has between 50% and 75% cubic boron nitride by volume and between 25% and 50% binder phase by volume, and inevitable impurities. The binder phase contains an Al compound and a Zr compound. The Al compound contains Al and one or more of N, O and B; and the Zr compound contains Zr and one or more of C, N, O and B. At a polished surface of the cubic boron nitride sintered body, 40% or more of the Zr compounds satisfy the ratio 0.25≦n/N≦0.8, where: N represents the number of line segments drawn radially at equal intervals from a center of gravity of a given Zr compound to a boundary with a non-Zr compound; and n represents the number among those N line segments which intersect a boundary between the given Zr compound and cubic boron nitride.

A sintered body of the present invention is a sintered body including a first material and cubic boron nitride. The first material is partially-stabilized ZrO.sub.2 including 5 to 90 volume % of Al.sub.2O.sub.3 dispersed in crystal grain boundaries or crystal grains of partially-stabilized ZrO.sub.2.

The present invention provides a diamond coated tool which is resistant to exfoliation at an interface between a base material and a diamond layer. The diamond coated tool of the present invention is a diamond coated tool including a base material and a diamond layer coating a surface of the base material, and characterized in that the surface of the base material has an arithmetic average roughness Ra of not less than 0.1 μm and not more than 10 μm and an average length of roughness profile elements RSm of not less than 1 μm and not more than 100 μm, and that the diamond layer has a plurality of cavities extending from a portion bordering on the base material in a crystal growth direction.