Cemented carbide contains first hard-phase particles containing WC, second hard-phase particles which contain carbonitride containing at least Ti and Nb, and a metallic binder phase containing an iron-group element. The second hard-phase particle includes a granular core portion. The core portion contains composite carbonitride expressed as Ti.sub.1XYNb.sub.XW.sub.YC.sub.1ZN.sub.Z, where X is not smaller than 0.1 and not greater than 0.2, Y is not smaller than 0 and not greater than 0.05, and Z is not smaller than 0.3 and not greater than 0.6. The cemented carbide has an absolute value of a difference not greater than 10, between a ratio (%) of an area occupied by the second hard-phase particles at a surface thereof and a ratio (%) of an area occupied by the second hard-phase particles in a region extending from the surface by 0.5 mm in a direction of depth.

The disclosure relates to a method for preparing Ti(C,N)-based superhard metal composite materials, with Ti(C,N) powder and (W,Mo,Ta)(C,N) powder as main raw materials and Co powder as binding phase for preparation, thereby obtaining a material in which a microstructure is a double-core rim structure that has both a black core rim and a white core rim. The material has a complete and evenly distributed double-core rim structure. In the condition that the ensured hardness of the material is not reduced and even slightly increased, the toughness of the material is significantly improved, wherein the fracture toughness of the material is in the range of 11.3 to 12.5 MPa.Math.m.sup.1/2.

The disclosure relates to a method for preparing Ti(C,N)-based superhard metal composite materials, with Ti(C,N) powder and (W,Mo,Ta)(C,N) powder as main raw materials and Co powder as binding phase for preparation, thereby obtaining a material in which a microstructure is a double-core rim structure that has both a black core rim and a white core rim. The material has a complete and evenly distributed double-core rim structure. In the condition that the ensured hardness of the material is not reduced and even slightly increased, the toughness of the material is significantly improved, wherein the fracture toughness of the material is in the range of 11.3 to 12.5 MPa.Math.m.sup.1/2.

A hard material includes a first hard phase containing titanium carbonitride as a major constituent and a binder phase containing an iron group element as a major constituent. In any surface or cross-section of the hard material, the grain size D50 at a cumulative percentage of 50% of a grain size distribution by area of the first hard phase is 1.0 m or more, and the average aspect ratio of first hard phase particles having grain sizes larger than or equal to D50 is 2.0 or less.

A complex carbonitride powder contains Ti as a main component element and at least one additional element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si. The complex carbonitride powder includes a plurality of complex carbonitride particles containing Ti and the additional element. The plurality of complex carbonitride particles include a plurality of homogeneous composition particles where average concentrations of Ti and the additional element in each complex carbonitride particle have a difference in a range of greater than or equal to 5 atom % and less than or equal to 5 atom % from average concentrations of Ti and the additional element in the whole complex carbonitride powder. A cross-sectional area of the homogeneous composition particles is greater than or equal to 90% of a cross-sectional area of the complex carbonitride particles 1p.

A complex carbonitride powder contains Ti as a main component element and at least one additional element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si. The complex carbonitride powder includes a plurality of complex carbonitride particles containing Ti and the additional element. The plurality of complex carbonitride particles include a plurality of homogeneous composition particles where average concentrations of Ti and the additional element in each complex carbonitride particle have a difference in a range of greater than or equal to 5 atom % and less than or equal to 5 atom % from average concentrations of Ti and the additional element in the whole complex carbonitride powder. A cross-sectional area of the homogeneous composition particles is greater than or equal to 90% of a cross-sectional area of the complex carbonitride particles 1p.

Cermet contains a hard phase which contains carbonitride containing Ti and Nb and a metallic binder phase containing an iron-group element. The hard phase includes a granular core portion and a peripheral portion which covers at least a part of the core portion. The core portion contains composite carbonitride expressed as Ti.sub.1-X-YNb.sub.XW.sub.YC.sub.1-ZN.sub.Z, where Y is not smaller than 0 and not greater than 0.05 and Z is not smaller than 0.3 and not greater than 0.6. The peripheral portion is composed to be higher in content of W than the core portion.

Cermet contains a hard phase which contains carbonitride containing Ti and Nb and a metallic binder phase containing an iron-group element. The hard phase includes a granular core portion and a peripheral portion which covers at least a part of the core portion. The core portion contains composite carbonitride expressed as Ti.sub.1-X-YNb.sub.XW.sub.YC.sub.1-ZN.sub.Z, where Y is not smaller than 0 and not greater than 0.05 and Z is not smaller than 0.3 and not greater than 0.6. The peripheral portion is composed to be higher in content of W than the core portion.

A cemented carbide includes second hard phase grains, wherein the second hard phase grains includes a core portion, and in a case where a total of 70 unit regions that are each constituted of a square having each side of 8m are provided by successively arranging 7 unit regions in a longitudinal direction and 10 unit regions in a lateral direction in an electron microscope image of any cross section of the cemented carbide captured at a magnification of 1500, where the total number of core portions in the total of 70 unit regions is calculated, and where a percentage of the number of core portions in each of the unit regions with respect to the total number of core portions is calculated, the number of unit regions in which the percentage is less than 0.43% or more than 2.43% is less than or equal to 10.

A cemented carbide includes second hard phase grains, wherein the second hard phase grains includes a core portion, and in a case where a total of 70 unit regions that are each constituted of a square having each side of 8m are provided by successively arranging 7 unit regions in a longitudinal direction and 10 unit regions in a lateral direction in an electron microscope image of any cross section of the cemented carbide captured at a magnification of 1500, where the total number of core portions in the total of 70 unit regions is calculated, and where a percentage of the number of core portions in each of the unit regions with respect to the total number of core portions is calculated, the number of unit regions in which the percentage is less than 0.43% or more than 2.43% is less than or equal to 10.