Ceramic based composites with improved fracture toughness

摘要

Composite materials, articles and cutting tools are prepared by densification to form a body comprising whiskers of hard refractory transition metal carbides, nitrides or carbonitrides uniformly distributed in a two-phase ceramic matrix. In one aspect of the invention, a first phase comprises silicon nitride grains and the second phase is an intergranular phase formed from one or more suitable densification aids. In another aspect, a first phase comprises silicon aluminum oxynitride grains and the second phase is formed from one or more suitable densification aids and alumina. Optionally, dispersoid particles and/or polycrystalline fibers may also be incorporated. The preferred composite article or cutting tool has a fracture toughness equal to or greater than about 3.5 MPa·m ^½. Methods for preparation and use are also described.