A surface-coated cutting tool has a hard coating layer and a tool body, which is coated with a lower layer including a TiCN layer having at least an NaCl type face-centered cubic crystal structure and an upper layer formed of a TiAlCN layer having a single phase crystal structure of NaCl type face-centered cubic crystals or a mixed phase crystal structure of NaCl type face-centered cubic crystals and hexagonal crystals. The tool body is further coated with an outermost surface layer including an Al.sub.2O.sub.3 layer, when the layer of a complex nitride or complex carbonitride of Ti and Al is expressed by the composition formula: (Ti.sub.1-xAl.sub.x)(C.sub.yN.sub.1-y), the average amount Xave of Al in Ti and Al and the average amount Yave of C in C and N (both Xave and Yave are atomic ratios) respectively satisfy 0.60≦Xave≦0.95 and 0≦Yave≦0.005.

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 3.1 μm and not more than 5.4 μm, and that the diamond layer has a plurality of cavities at a portion bordering on the base material.

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.

In a surface-coated cutting tool, an A layer made of an (Al.sub.1-xTi.sub.x)N layer (0.35≦x≦0.6 by an atom ratio) and a B layer made of a (Al.sub.1-y-zTi.sub.ySi.sub.z)N layer (0.35≦y≦0.6 and 0.01≦z≦0.1 by an atom ratio) are layered on a surface of a tool body in which at least a cutting edge is made of a cBN sintered body. A layer thickness ratio of the A layer and the B layer (t.sub.B/t.sub.A) is 2 to 5, an X-ray diffraction intensity ratio I(200)/I(111) as the entire hard coating layer is more than 3 and 12 or less, a full width at half maximum of a peak of I(200) is 0.3 to 1.0, the I.sub.A(200)/I.sub.A(111) of the A layer is 2 to 10, and a full width at half maximum of the peak of the I.sub.A(200) is 0.3 to 1.0.

A composite diamond body includes a diamond base material and a stable layer disposed on the diamond base material. The stable layer may have a thickness of 0.001 μm or more and less than 10 μm, and may include a plurality of layers. A composite diamond tool includes the composite diamond body. There are thus provided highly wear-resistant composite diamond body and composite diamond tool that are even applicable to mirror-finish planarization of a workpiece which reacts with diamond to cause the diamond to wear.

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).