Ngk Spark Plug Company, Limited

501 Ngk Spark Plug Co. Ltd.

Hidetoshi Baba

Hiroshi Tanaka

A high-toughness ceramic tool material consisting essentially of 50-95% by volume of a main sialon base phase wherein at least 10% by volume of the sialon base phase consists of alpha-sialon, and 5-50% by volume of a SiC whisker phase. This ceramic material is produced by sintering a composition comprising:

High-toughness ceramic tool materials

A nitride based ceramic cutting tool is described comprising from 50 to 90% by weight Si.sub.2 N.sub.4, from 5 to 45% by weight TiN, and from 5 to 45% by weight sintering aid, said sintering aid comprising (1) at least one of Y.sub.2 O.sub.3 and Dy.sub.2 O.sub.3 and (2) Al.sub.2 O.sub.3 alone or a mixture of AlN and Al.sub.2 O.sub.3, said mixture comprising from 5 to 65% by weight AlN, and the weight ratio of (1) at least one of Y.sub.2 O.sub.3 and Dy.sub.2 O.sub.3 to (2) Al.sub.2 O.sub.3 alone or the AlN and Al.sub.2 O.sub.3 mixture being 3:1 to 1:3.

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Aichi, Japan

Hidetoshi Baba