| 摘要 |
Coated cutting tools and coated cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a silicon nitride substrate body having at least one hard, intermediate adherent coating layer of a refractory material and an outer adherent coating layer. The intermediate adherent coating layer has a different chemical composition than the outer adherent coating layer. The silicon nitride substrate body consists essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from the group consisting of silicon dioxide, aluminum oxide, magnesium oxide, yttrium oxide, hafnium oxide, zirconium oxide, the lanthanide rare earth oxides, and mixtures thereof.
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