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

摘要

PROBLEM TO BE SOLVED: To provide a coating tool having a hard coating layer equipped with excellent chipping resistance and defect resistance in high-speed intermittent cutting work and exerting excellent wear resistance over a long term use.SOLUTION: In a surface-coated cutting tool, a hard coating layer includes at least a composite nitride or composite carbonitride layer represented by a composition formula: (TiAl)(CN); a periodic density change exists in the crystal grain of the composite nitride or carbonitride having an NaCl type face-centered cubic structure; the direction of the periodic density change includes at least a direction in which the angle between that direction and a plane parallel to a tool substrate surface is within 30 degrees; the above layer has preferably a columnar structure; an area ratio in which the periodic density changes of Ti and Al exist is 40 area% or more; the period of density change is 1-10 nm, and the difference between the average maximal and minimal values of an Al inclusion ratio x changing periodically is 0.01 to 0.1; and fine crystal grains having a hexagonal crystal structure of an average crystal grain size of 0.01-0.3 μm exist 5 area% or less in a crystal grain boundary.SELECTED DRAWING: Figure 3