A metastable precursor powder containing 20-60 pct si3n4 was prepared from si, al2o3, and al or aln by controlled nitridation. The powder was processed to sialon by doping the precursor powder with a sintering aid, cold-pressing or slip-casting, and sintering in n2. The sialon is used to make valve components and metal die- casting molds. Thus, a mixture of si 77.4, Al2o3 11.3 and al 11.3 Mol pct are mixed, screened through 50 mesh, agglomerated with water to approximately 20 mesh, dried, prereacted at 500 deg c for 1 h in n2 at 3 psig, and reacted with n2 at 1,380 deg c and 3 psi for 4 h to prepare the precursor powder. The precursor powder was mixed with 5 wt pct gd2o3 sintering aid milled, screened through 50 mesh, cold pressed at 20,000 psi, and sintered at 1,700 deg c in n2 for 1 h at 5 psi.
U.S. Pat. 4,184,884, Jan. 22, 1980; Chem. Abstr. 91:215,597Q