| 摘要 |
PROBLEM TO BE SOLVED: To provide a cutting tool made of a surface coated boron nitride sintered material with a hard coating layer exhibiting excellent chipping resistance and heat-resistant plastic deformability. SOLUTION: The cutting tool comprises the hard coating layer formed on the surface of a tool substrate composed of a cubic boron nitride sintered material. The hard coating layer is composed of (a) a lower layer formed of a compound nitride layer of Ti, Al and Y (yttrium) having the average layer thickness of 0.5-10μm and satisfying a composition formula: [Ti<SB>1-(X+Z)</SB>Al<SB>X</SB>Y<SB>Z</SB>]N, wherein X is 0.40-0.60, and Z is 0.005-0.05 at the atomic ratio, and (b) an upper layer formed of a heat-transformedα-type Al<SB>2</SB>O<SB>3</SB>layer formed by applying heat treatment in a state of forming a titanium oxide layer by vapor deposition in the average thickness of 0.05-1μm on the surface of an Al<SB>2</SB>O<SB>3</SB>layer having aκ-type orθ-type crystal structure and the average layer thickness of 0.5-10μm formed by vapor deposition, to transform the crystal structure of the Al<SB>2</SB>O<SB>3</SB>layer having theκ-type orθ-type crystal structure, into anα-type crystal structure. COPYRIGHT: (C)2006,JPO&NCIPI
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