SURFACE-COATED CUTTING TOOL HAVING HARD COATING LAYER EXERTING EXCELLENT CHIPPING RESISTANCE

摘要

PROBLEM TO BE SOLVED: To provide a coated cutting tool which has a hard coating layer excellent in hardness and toughness, and which exerts chipping resistance and defect resistance over a long-term use.SOLUTION: The hard coating layer includes at least a composite nitride layer or composite carbonitride layer of Ti, Al and Si, the average content ratios of Al, Si and C, x, yand z(all are the atomic ratios) satisfy 0.60≤x≤0.88, 0.10≤y≤0.25 and 0≤z≤0.005, respectively. The composite nitride layer or composite carbonitride layer includes at least a phase of the composite nitride or composite carbonitride having an NaCl type structure. In the composite nitride or carbonitride having the NaCl type structure, the average particle width W of the crystal grain thereof is 0.05 to 1.0μm, and an average aspect ratio A is 5 or less, and one, or two or more crystal grains or amorphous phases selected from nitride, carbide and carbonitride of Si exist around the crystal grains.