A hard coating, which is to be disposed to cover a surface of a substrate, has a total thickness of 0.5-20 m, and includes an A layer and nanolayer-alternated layer that are alternately laminated by physical vapor deposition. The nanolayer-alternated layer includes a B layer and a C layer that are alternately laminated. The A layer has a thickness of 50-1000 nm and is AlCr nitride that is represented by a composition formula of [Al.sub.1-UCr.sub.U]N wherein an atomic ratio U is 0.20-0.80. The B layer has a thickness of 1-100 nm and is TiAl nitride that is represented by a composition formula of [Ti.sub.1-WAl.sub.W]N wherein an atomic ratio W is 0.30-0.85. The C layer has a thickness of 1-100 nm and is TiSi nitride that is represented by a composition formula of [Ti.sub.1-YSi.sub.Y]N wherein an atomic ratio Y is 0.05-0.45. The nanolayer-alternated layer has a thickness of 50-1000 nm.

A hard material which, when used as a material of a sintered material, makes it possible to obtain a sintered material with excellent abrasion resistance, a sintered material, a cutting tool including the sintered material, a method for manufacturing the hard material and a method for manufacturing the sintered material are provided. The hard material contains aluminum, nitrogen, and at least one element selected from the group consisting of titanium, chromium, and silicon, and has a cubic rock salt structure.

In an embodiment, a cutting insert includes an upper surface, a one or more side surfaces, and a cutting edge. The upper surface includes a first corner portion, and a first side that is adjacent to the first corner portion. The one or more side surfaces are adjacent to the upper surface. The cutting edge is disposed on at least a portion of a section where the upper surface and the side surfaces intersect. When viewed from directly above, the cutting edge includes first, second, third and fourth cutting edges. The first cutting edge is disposed at the first corner portion and has a convex curved shape. The second cutting edge is next to the first cutting edge, and has a linear shape. The third cutting edge is next to the second cutting edge, and has a convex curved shape. The fourth cutting edge is next to the third cutting edge on the first side.

A coated cutting tool includes a substrate having a rake side, a clearance side and a cutting edge and a coating comprising a first layer and a second layer. The second layer has a sandwich structure of an inner layer, an intermediate layer and an outer layer, wherein the inner layer is exposed through an opening in the outer layer, the opening extending over at least a portion of the width of the cutting edge. Thereby, a double layer is provided in critical areas, whereas a single layer is provided in other areas. The double oxide layer is an aluminum oxide layer. A method for manufacturing the coated cutting tool is also provided.

A hard material layer system with a multilayer structure, comprising alternating layers A and B, with A layers having the composition Me.sub.ApAO.sub.nAN.sub.mA in atomic percent and B layers having the composition Me.sub.BpBO.sub.nBN.sub.mB in atomic percent, where the thermal conductivity of the A layers is greater than the thermal conductivity of the B layers. Me.sub.A and Me.sub.B each comprise at least one metal of the group Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Al, p.sub.A indicates the atomic percentage of Me.sub.A and p.sub.B indicates the atomic percentage of Me.sub.B and the following is true: P.sub.A=P.sub.B, n.sub.A indicates the oxygen concentration in the A layers in atomic percent and n.sub.B indicates the oxygen concentration in the B layers in atomic percent and the following is true: n.sub.A<n.sub.B, and m.sub.A indicates the nitrogen concentration in the A layers in atomic percent and m.sub.B indicates the nitrogen concentration in the B layers in atomic percent and the following is true: p.sub.A/(n.sub.A+m.sub.A)=p.sub.B/(n.sub.B+m.sub.B).

A surface-coated cutting tool according to the present invention includes a coating. The coating has an -Al.sub.2O.sub.3 layer. The -Al.sub.2O.sub.3 layer includes a lower layer portion and an upper layer portion. When respective crystal orientations of crystal grains of -Al.sub.2O.sub.3 are specified by performing EBSD analyses with an FE-SEM on a cross-section obtained when the -Al.sub.2O.sub.3 layer is cut along a plane including a normal line of a surface of the -Al.sub.2O.sub.3 layer and a color map is prepared based on the crystal orientations, in the color map, an area in the upper layer portion occupied by the crystal grains of which normal direction of a (001) plane is within 10 with respect to a normal direction of the surface of the -Al.sub.2O.sub.3 layer is equal to or more than 90%, and such an area in the lower layer portion is equal to or less than 50%.

Methods of forming a drill bit or boring tool having a cutting edge that includes a pair of generally smooth curvilinear shaped portions that are positioned near the radial outer portions of the cutting edge and connected to one another by a pair of generally linear portions that traverse a longitudinal centerline of the tool.

A surface-coated cutting tool according to the present invention includes a coating. The coating has an -Al.sub.2O.sub.3 layer. The -Al.sub.2O.sub.3 layer includes a lower layer portion and an upper layer portion. When respective crystal orientations of crystal grains of -Al.sub.2O.sub.3 are specified by performing EBSD analyses with an FE-SEM on a cross-section obtained when the -Al.sub.2O.sub.3 layer is cut along a plane including a normal line of a surface of the -Al.sub.2O.sub.3 layer and a color map is prepared based on the crystal orientations, in the color map, an area in the upper layer portion occupied by the crystal grains of which normal direction of a (001) plane is within 10 with respect to a normal direction of the surface of the -Al.sub.2O.sub.3 layer is equal to or more than 90%, and such an area in the lower layer portion is equal to or less than 50%.

The present invention relates to a coated cutting tool including a substrate and a coating. The coating has, from about 0.5 to about 10 m, a nano-multilayer of alternating nanolayers of a first nanolayer type of Ti.sub.1-xAl.sub.xN, wherein 0.45x<0.67, a second nanolayer type of Cr.sub.1-yAl.sub.yN, wherein 0.60y0.80, and a third nanolayer type of Ti.sub.1-zSi.sub.zN, wherein 0.14z0.25. An average nanolayer thickness of each of the nanolayer types Ti.sub.1-xAl.sub.xN, Cr.sub.1-yAl.sub.yN and Ti.sub.1-zSi.sub.zN in the nano-multilayer is 1 nm but <3 nm.

A drill bit or boring tool having cutting edge that includes a pair of generally smooth curvilinear shaped portions that are positioned near the radial outer portions of the cutting edge and connected to one another by a pair of generally linear portions that traverse the longitudinal centerline of the tool.