TOOL COMPRISED OF A SILICON NITRIDE SINTERED BODY

摘要

A tool comprised of a silicon nitride sintered body which is excellent in toughness as well as wear resistance can be provided in an economical manner. The novel feature of the tool is that the silicon nitride crystal grains comprise 50 to 90% by volume of hexagonal pillar crystals having a minor axis of at most 1.0 mu m and 5 to 30% by volume of hexagonal pillar or columnar crystals having a minor axis of at least 1.5 mu m. As the silicon nitride starting powder, there is preferably used a mixture of at least two silicon nitride powders prepared by the imide decomposition method, direct metallic silicon nitriding method and silica reducing method.