CERMET OR CERAMIC/GLASS COMPOSITES INCLUDING SELF-REINFORCED BETA-SILICON NITRIDE, AND METHOD OF MAKING SAME

摘要

Infiltrate a porous, self-reinforced (beta)-Si3N4 preform with a metal or a crystallizable glass to yield a composite material. The preform possesses a low glass phase and has a density of from 50 to 70 percent of theoretical density. Prepare the (beta)-Si3N4 preform by subjecting a porous body formed from an (alpha)-Si3N4 powder composition to two sequential heat treatments. The first heat treatment occurs below the (alpha)- to (beta)-conversion temperature and results in a strengthened body that can be machined. The second heat treatment occurs above that temperature and yields the self-reinforced (beta)-Si3N4 preform. Conventional infiltration procedures with an infiltrant that is a metal or a glass results in an Si3N4/metal or Si3N4/glass composite material that has 50 to 70 percent of its volume occupied by (beta)-Si3N4 whiskers.