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.

Disclosed are a composite sintered body for a cutting tool and a cutting tool using the same. The composite sintered body for a cutting tool has enhanced heat conductivity and electrical conductivity to be strong against abrasion by heat and impact and to be capable of minimizing an influence on an edge during an Electrical Discharge Machine (EDM) operation.

A cutting tool comprises a rake face and a flank face, the cutting tool being composed of a substrate made of a cubic boron nitride sintered material and a coating provided on the substrate, the coating including a MAlN layer, when a cross section of the MAlN layer is subjected to an electron backscattering diffraction image analysis to determine a crystal orientation of each of the crystal grains of the M.sub.xAl.sub.1−xN and a color map is created based thereon, then on the color map, the flank face having the MAlN layer occupied in area by 45% to 75% by crystal grains of the M.sub.xAl.sub.1−xN having a (111) plane with a normal thereto extending in a direction within 25 degrees with respect to a direction in which a normal to the flank face extends, the MAlN layer having a residual stress of −2 GPa to −0.1 GPa.

Provided is a cubic boron nitride sintered body including more than or equal to 85 volume percent and less than 100 volume percent of cubic boron nitride particles, and a remainder of a binder, wherein the binder contains WC, Co, and an Al compound, the binder contains W.sub.2Co.sub.21B.sub.6, and, when I.sub.A represents an X-ray diffraction intensity of a (111) plane of the cubic boron nitride particles, I.sub.B represents an X-ray diffraction intensity of a (100) plane of the WC, and I.sub.C represents an X-ray diffraction intensity of a (420) plane of the W.sub.2Co.sub.21B.sub.6, a ratio I.sub.C/I.sub.A of the I.sub.C to the I.sub.A is more than 0 and less than 0.10, and a ratio I.sub.C/I.sub.B of the I.sub.C to the I.sub.B is more than 0 and less than 0.40.

A cubic boron nitride sintered material includes: more than 80 volume % and less than 100 volume % of cubic boron nitride grains; and more than 0 volume % and less than 20 volume % of a binder phase. The binder phase includes: at least one selected from a group consisting of a simple substance, an alloy, and an intermetallic compound selected from a group consisting of a group 4 element, a group 5 element, a group 6 element in a periodic table, aluminum, silicon, cobalt, and nickel. A dislocation density of the cubic boron nitride grains is more than or equal to 1×10.sup.15/m.sup.2 and less than or equal to 1×10.sup.17/m.sup.2.

A cubic boron nitride sintered material includes: 20 to 80 volume % of cBN grains; and 20 to 80 volume % of a binder phase, wherein the binder phase includes first binder grains and second binder grains, in each of the first binder grains, a ratio of the number of atoms of the first metal element to a total of the number of atoms of the titanium and the first metal element is more than or equal to 0.01% and less than 10%, in each of the second binder grains, the ratio is more than or equal to 10% and less than or equal to 80%, and an average grain size of the second binder grains is more than or equal to 0.2 μm and less than or equal to 1 μm.

A cubic boron nitride sintered material includes: more than or equal to 20 volume % and less than 80 volume % of cubic boron nitride grains; and more than 20 volume % and less than or equal to 80 volume % of a binder phase, and when a carbon content is measured from a cubic boron nitride grain into the binder phase in a direction perpendicular to an interface between the cubic boron nitride grain and the binder phase using TEM-EDX, a first region having a carbon content larger than an average value of a carbon content of the binder phase exists, the interface exists in the first region, and a length of the first region is more than or equal to 0.1 nm and less than or equal to 10 nm.

A cubic boron nitride sintered material includes: more than 80 volume % and less than 100 volume % of cubic boron nitride grains; and more than 0 volume % and less than 20 volume % of a binder phase. The binder phase includes: at least one selected from a group consisting of a simple substance, an alloy, and an intermetallic compound selected from a group consisting of a group 4 element, a group 5 element, a group 6 element in a periodic table, aluminum, silicon, cobalt, and nickel. A dislocation density of the cubic boron nitride grains is more than or equal to 1×10.sup.15/m.sup.2 and less than or equal to 1×10.sup.17/m.sup.2.

A cutting tool includes a base material, and a coating film covering the base material in contact with the base material. The base material is a cubic boron nitride sintered material. The coating film is a ceramic. An amount of oxygen in the coating film is less than or equal to 0.040 mass percent.

Bearing steel comprising cubic boron nitride (c-BN) and/or nickel coated cBN spark plasma sintered at a temperature in the range of 850-1050° C. is disclosed. The tribological and corrosion resistance of the bearing steel improved with increasing the amount of c-BN. Further improvement in the properties was achieved with the incorporation of nickel coated c-BN, which caused a phase transition of the bearing steel from magnetic to non-magnetic phase accompanied by interdiffusion enhancement between the matrix and c-BN reinforcement.