Cutting tool insert

A cutting tool insert of a sintered ceramic material for machining ferrous materials, said ceramic material consisting essentially of at least 70% by volume of aluminum nitride, in which a hard substance selected from the group consisting of carbides, nitrides and borides of titanium, tungsten and niobium or mixtures thereof, and a metal oxide compound as additional component, are uniformly distributed, the hard substance being present in an amount of 7 to 29% by volume, the metal oxide compound being present in an amount of 1 to 15% by volume, and together with aluminum nitride make up at least 99.7% by volume;

• the ceramic material having no more than 0.3% by volume of impurities therein, produced by the process comprising:
• hot pressing a dry powder of the aluminum nitride, the hard substance and the metal oxide to form the cutting tool insert.

A cutting tool insert of a sintered ceramic material for machining ferrous materials, said ceramic material consisting essentially of at least 70% by volume of aluminum nitride, in which a hard substance selected from the group of carbides, nitrides and borides of titanium, tungsten and niobium or mixtures thereof, and a metal oxide compound as additional component, are uniformly distributed, the hard substance being present in an amount of 7 to 29% by volume, the metal oxide compound being present in an amount up to 15% by volume, and together with aluminum nitride make up at least 99.7% by volume;

• the ceramic material having no more than 0.3% by volume of impurities therein, produced by the process comprising:
• preparing a compact of the aluminum nitride, the hard substance and the metal oxide;
• and subjecting the compact to a sintering without pressure, said compact containing metal oxide compounds in an amount of at least 3 vol.-%.