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US 5,668,069 AGranted
Cutting tool composed of silicon nitride
AssigneeKYOCERA Corporation
InventorsMasahiro Sato, Yukiyasu Aoyama, Nobuoki Takagi, Shoji Kohsaka
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AssigneeKYOCERA Corporation
InventorsMasahiro Sato, Yukiyasu Aoyama, Nobuoki Takagi, Shoji Kohsaka
Estimating the term…
A cutting tool composed of silicon nitride comprising chiefly a .beta.-silicon nitride crystal phase and containing a grain boundary phase of rare earth elements, silicon, aluminum, oxygen and nitrogen, wherein the cutting surface is constituted by at least a fired surface or a surface formed by removing and polishing the fired surface by an amount of not larger than 10 .mu.m, and has in the mirror surface thereof a micro-Vicker's hardness which is higher than that of the interior thereof and is not smaller than 16 GPa. The cutting tool has a cutting surface that can be easily worked enabling the cost of working to be decreased, and has a highly hard layer that is suited for cutting cast iron and the like materials featuring increased durability and extended cutting life.
A cutting tool composed of silicon nitride comprising chiefly a .beta.-silicon nitride crystal phase and containing a grain boundary phase of rare earth elements, silicon, aluminum, oxygen and nitrogen, wherein the cutting surface is constituted by at least a fired surface or a surface formed by removing and polishing the fired surface by an amount of not larger than 10 .mu.m, and has in the mirror surface thereof a micro-Vicker's hardness which is higher than that of the interior thereof and is not smaller than 16 Gpa, wherein the cutting tool contains 1 to 10 mole % of rare earth element calculated as an oxide, 1 to 10 mole % of aluminum calculated as an oxide, and 3 to 20 mole % of impurity oxygen calculated as SiO.sub.2, the total amount of these calculated values being 5 to 25 mole %.
Dependencies are inferred from the claim text.