Ceramic composite and method.

摘要

Ceramic composite is cold formed into a machinable article which resists corrosion/erosion by molten metal is obtd. by: (i) blending a mixt. of 18.5-29 wt.% mullite, 18-35 wt.% AlN and balance as at least 40 wt.% BN; (ii) milling to an average size below 5 micron; (iii) coating the particles with a resinous lubricant comprising a soln. of vinyl chloride-vinyl acetate in organic solvent; (iv) pressing the mixt. to shape; and (v) pressureless sintering. Also claimed is hot-pressing a BN ceramic composite of the above compsn. at 1650-1900 deg.C and 1800-2500 psi, and preventing fracture by gradually decreasing pressure during cooling. The mixt. pref. includes 1-5 wt.% CaO and is milled to 3-5 micron average particle size; a pre-blend is formed comprising the CaO and equal amts. of a proportion of the other components of the mixt. The organic solvent is methylethyl ketone. The cold shapes are pressed to 55-66% theoretical density and sintering is at a heating rate below 400 deg.C/hr.