| 摘要 |
A cubic boron nitride sintered body is composed of cubic boron nitride (1) in an amount of 50 to 75% by volume inclusive and a binder phase and unavoidable impurities in the total amount of 25 to 50% by volume inclusive, wherein the binder phase contains an Al compound (3) and a Zr compound (2), the Al compound (3) contains Al and at least one element selected from N, O and B, the Zr compound (2) contains Zr and at least one element selected from C, N, O and B, and the number of pieces of the Zr compound (2) each of which has an n/N ratio of 0.25 to 0.8 inclusive is 40% or more relative to the total number of all pieces of the Zr compound (2) in which N represents the number of multiple line segments (5) each of which extends from the center of gravity (4) of a piece of the Zr compound (2) to a part having a chemical composition other than the Zr compound (2) and which are drawn radially at regular intervals in a polished surface of the cubic boron nitride sintered body and n represents the number of some of the line segments (5) each of which extends from the center of gravity (4) of the piece of the Zr compound (2) to the boundary between the Zr compound and a piece of cubic boron nitride in the polished surface of the cubic boron nitride sintered body. |
