A coated cutting tool comprising a cemented carbide and a coating layer formed on a surface of the cemented carbide, wherein: an average thickness of the coating layer is from 5.0 m or more to 30.0 m or less; and in the cemented carbide, when regarding a region thereof which ranges from the surface of the cemented carbide to a depth of 20.0 m in a direction opposite to the coating layer as a surface region, and also regarding a region thereof on a side opposite to the coating layer across the surface region as an inner region, an average value of KAM values in the surface region KAM.sub.s and an average value of KAM values in the inner region KAM.sub.i satisfy a condition represented by formula (1) below.
0.00|KAM.sub.sKAM.sub.i|0.10(1)

Provided is a ceramic sintered body having high wear resistance and chipping resistance. Also provided are an insert, a cutting tool and a friction stir welding tool, each of which uses such a high-performance ceramic sintered body. The ceramic sintered body includes Al.sub.2O.sub.3 (alumina), WC (tungsten carbide) and ZrO.sub.2 (zirconia), wherein Zr (zirconium) element is present at either one or both of: (1) a grain boundary between crystal grains of the Al.sub.2O.sub.3; and (2) a grain boundary of crystal grains of the Al.sub.2O and crystal grains of the WC, wherein the ceramic sintered body contains 55.0 to 97.5 vol % of the WC, 0.1 to 18.0 vol % of the ZrO.sub.2, and the balance being the Al.sub.2O.sub.3, and wherein the ZrO.sub.2 is in a phase of tetragonal structure (T) or a mixed phase of tetragonal structure (T) and monoclinic structure (M).

A surface-coated cutting tool including a substrate including a rake face and a flank face and a coating which covers a surface of the substrate is provided. The substrate is made of a cBN sintered material or a ceramic sintered material. The coating includes an alternating layer. The alternating layer is made by alternately stacking a first layer and a second layer different in composition from the first layer. The first layer contains Al, Cr, and N. The second layer contains Ti, Al, and N. A ratio T1/T2 between a thickness Ti of the first layer and a thickness T2 of the second layer is not lower than 0.1 and lower than 1. There are thirty or more interfaces at which the first layer and the second layer are in contact with each other.

A surface-coated cutting tool including a substrate including a rake face and a flank face and a coating which covers a surface of the substrate is provided. The substrate is made of a cBN sintered material or a ceramic sintered material. The coating includes an alternating layer. The alternating layer is made by alternately stacking a first layer and a second layer different in composition from the first layer. The first layer contains Al, Cr, and N. The second layer contains Ti, Al, and N. A ratio T1/T2 between a thickness Ti of the first layer and a thickness T2 of the second layer is not lower than 0.1 and lower than 1. There are thirty or more interfaces at which the first layer and the second layer are in contact with each other.

In a surface-coated cutting tool, an A layer made of an (Al.sub.1-xTi.sub.x)N layer (0.35x0.6 by an atom ratio) and a B layer made of a (Al.sub.1-y-zTi.sub.ySi.sub.z)N layer (0.35y0.6 and 0.01z0.1 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.

In a surface-coated cutting tool, an A layer made of an (Al.sub.1-xTi.sub.x)N layer (0.35x0.6 by an atom ratio) and a B layer made of a (Al.sub.1-y-zTi.sub.ySi.sub.z)N layer (0.35y0.6 and 0.01z0.1 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 method of providing a self-healing coating includes providing substrate, applying a layer of an aluminum-containing MAX phase material and another material to the substrate. The method includes exposing the layer to a temperature greater than 2000 F. to form alpha aluminum.

A method of providing a self-healing coating includes providing substrate, applying a layer of an aluminum-containing MAX phase material and another material to the substrate. The method includes exposing the layer to a temperature greater than 2000 F. to form alpha aluminum.

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 0.25n/N0.8, 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 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 0.25n/N0.8, 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.