| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of cracks even when used under warming/cooling. SOLUTION: On the surface of a base material 15 composed of a cemented carbide or a cermet, a platinum group based metal plating layer 16 is formed as a cutting layer. The metal plating layer 16 is formed into an optical face shape by superprecision cutting, so as to be finished with a desired precision. Since the linear expansion coefficient of the base material 15 composed of a cemented carbide consisting essentially of tungsten carbide is 9-10×10<SP>-6</SP>, but the linear expansion coefficient of the platinum group based metal plating layer 16 is 6-10×10<SP>-6</SP>, cracks can be prevented eve if it used under warming/cooling, and further, since cracks are hardly caused, the plating layer 16 can be thickly formed. COPYRIGHT: (C)2009,JPO&INPIT
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