A cubic boron nitride sintered material comprises 30% by volume or more and 80% by volume or less of cubic boron nitride grains and 20% by volume or more and 70% by volume or less of a binder phase, the cubic boron nitride grains having a dislocation density of 3×10.sup.17/m.sup.2 or more and 1×10.sup.20/m.sup.2 or less.

Disclosed are a coated cutting tool in which a coating layer is formed and a method for making the coating layer. The coating layer of the cutting tool of the present disclosure is formed on the whole or part of a substrate, and includes an MT-TiCN layer and an α-Al.sub.2O.sub.3 layer which are formed of columnar grains. The MT-TiCN layer has texture coefficients of TC(311)>1.5 and TC(422)>1.5 and is formed of TiCN deposited by a chemical vapor deposition method within the range of 800° C. to 950° C., and the α-Al.sub.2O.sub.3 layer is formed of columnar grains and has TC(006)>4. The coating layer of the present disclosure may form a coating layer (coating) having excellent wear resistance and chipping resistance by depositing, an α-Al.sub.2O.sub.3 layer having a strong orientation in a <001> crystallographic direction with excellent adhesion, without using an HT-TiCN layer as in the related art.

Provided is a coated cutting tool having improved wear resistance and fracture resistance and a long tool life. The coated cutting tool include a substrate and a coating layer formed on the substrate, wherein the coating layer has an alternately laminated structure of a first layer and a second layer, the first layer contains a compound having a composition represented by (Al.sub.aM.sub.bTi.sub.1-a-b, wherein M represents at least one of a Mo element and a W element, and 0.75≤a≤0.90 and 0.00<b≤0.20 are satisfied, the second layer contains a compound having a composition represented by (Al.sub.cM.sub.dTi.sub.1-c-d)N, wherein M represents at least one of a Mo element and a W element, and 0.75≤c≤0.90 and 0.00≤d≤0.20 are satisfied, the compound contained in the second layer being different from the compound contained in the first layer, at least one of a and c is 0.80 or more and, and an average thickness of the alternately laminated structure is 0.5 μm or more and 5.0 μm or less.

A cubic boron nitride sintered material comprises cubic boron nitride particles and a bonding material, wherein the bonding material comprises at least one first metallic element selected from the group consisting of titanium, zirconium, vanadium, niobium, hafnium, tantalum, chromium, rhenium, molybdenum, and tungsten; cobalt; and aluminum; the cubic boron nitride sintered material has a first interface region sandwiched between an interface between the cubic boron nitride particles and the bonding material, and a first virtual line passing through a point 10 nm apart from the interface to the bonding material side; and when an element that is present at the highest concentration among the first metallic elements in the first interface region is defined as a first element, an atomic concentration of the first element in the first interface region is higher than an atomic concentration of the first element in the bonding material excluding the first interface region.

A cubic boron nitride (cBN)-based composite including about 30-65 vol. % cBN, about 3-30 vol. % zirconium (Zr)-containing compounds, about 0-10 vol. % cobalt-tungsten-borides (Co.sub.xW.sub.yB.sub.z), about 2-30 vol. % aluminum oxide (Al.sub.2O.sub.3), about 0.5-10 vol. % tungsten borides, and less than or equal to about 5 vol. % aluminum nitride (AlN).

A method for coating a substrate 11 is disclosed. The method includes at least the following steps: depositing a first base layer 22 comprising a nitride of at least Al and Cr on the substrate 11 by physical vapor deposition at a gradually increasing substrate bias voltage from a first substrate bias voltage to a second substrate bias voltage; depositing a second base layer 23 comprising a nitride of at least Al and Cr on the first base layer 22 by physical vapor deposition at a constant substrate bias voltage that is greater or equal to the second substrate bias voltage; and depositing an outermost indicator layer 24 on the second base layer 23, wherein the outermost indicator layer 24 comprises a nitride of Si and Me, wherein Me is at least one of Ti, Zr, Hf, and Cr, wherein the outermost indicator layer 24 is deposited by physical vapor deposition at a substrate bias voltage that is less than the constant substrate bias voltage applied during deposition of the second base layer 23.

The cubic boron nitride sintered material is a cubic boron nitride sintered material comprising: cubic boron nitride particles in an amount of 70 vol % or more and less than 100 vol %, and a bonding material, wherein the bonding material includes an aluminum compound, and includes cobalt as a constituent element; the cubic boron nitride sintered material has a first region in which a space between adjacent cubic boron nitride particles is 0.1 nm or more and 10 nm or less; and when the first region is analyzed by using an energy dispersive X-ray analyzer equipped with a transmission electron microscope, the atom % of aluminum in the first region is 0.1 or more.

A cutting insert may include a base member. The base member may include a first surface, a second surface adjacent to the first surface, and a first cutting edge located in at least a part of a first ridge line which the first surface intersects with the second surface. The base member may include a hard phase containing a titanium carbonitride, and a binding phase containing at least one of cobalt and nickel. The hard phase may include a first hard phase observed on a higher angle side, and a second hard phase observed on a lower angle side in a comparison of (422) plane peak in an X-ray diffraction analysis. A compressive residual stress of the second hard phase in the second surface may be less than a compressive residual stress of the second hard phase in the first surface.

A cutting tool comprising a substrate and a coating film disposed on the substrate, wherein the coating film comprises a first layer; the first layer has a thickness of 0.2 μm or more and 9 μm or less; the first layer is composed of Ti.sub.(1-x-y)Al.sub.xM.sub.yN, wherein M is at least one element such as zirconium; in the first layer, x and y change along the thickness direction of the first layer; a maximum value of x, x.sub.max, is 0.20 or more and 0.70 or less; a minimum value of x, x.sub.min, is 0 or more and 0.6 or less; x.sub.max and x.sub.min satisfy 0.01≤x.sub.max−x.sub.min≤0.7; a maximum value of y, y.sub.max, is 0.01 or more and 0.20 or less; a minimum value of y, y.sub.min, is 0 or more and 0.19 or less; and y.sub.max and y.sub.min satisfy 0.01≤y.sub.max−y.sub.min≤0.2.

A cutting tool, including a cutting edge portion composed of a cubic boron nitride sintered material, wherein the cutting edge portion has: a flank face; a rake face contiguous to the flank face; and a cutting edge positioned on a ridgeline of the flank face and the rake face, an arithmetical mean height Sa of the flank face is 0.5 μm or more and 3.0 μm or less, the Sa is measured in accordance with ISO25178-2:2012, and an oxygen concentration of the flank face is 10 mass % or more and 50 mass % or less.