| 摘要 |
PROBLEM TO BE SOLVED: To increase the adhesion of coating film and to realize stable cutting over a long period by interposing a relatively soft secondary layer between a primary hard layer and a base alloy. SOLUTION: A secondary hard layer contg. at least one kind among the nitrides, carbon nitrides, nitrogen borides and carbon nitrogen borides of Zr is interposed below a coating film (a primary hard layer) composed of the nitrides, carbon nitrides or the like of Ti and Al. In this way, the high compressive stress of the primary hard layer is absorbed and relaxed to improve the adhesion of the coating film. Namely, the relatively soft coating film absorbs and relaxes the shearing stress generated on the boundaries owing to the high compressive stress. As for the conditions required for the coating film to be interposed, not only it is soft, but also it is preferable for the relaxation of the stress in the case the crystal grains are relatively coarse, and the smaller the face roughness is regulated, the more the adhesion is improved. For this purpose, the secondary hard layer contains the above Zr compounds. It is required that the thickness of the secondary hard layer is regulated to 0.05 to 5μm.
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