Silicon Carbide Ceramic Materials with Improved High-Temperature-Strength and Process of Making the Same

摘要

PURPOSE: Silicon carbides with high temperature strength and high toughness are provided for use as high temperature structural materials such as cutting tools, car engines and bearings. CONSTITUTION: Silicon carbides are prepared by the following steps of: wet ball-milling raw materials comprising beta-SiC powder(=3micrometer), 0.5-10wt.% of alpha-SiC powder(=3micrometer), 2-25wt.% of sintering aid selected from 1-12wt.% of AlN and 2-25wt.% of Er2O3 or 1-12wt.% of AlN and 2-25wt.% of Yb2O3, 0.1-3wt.% of organic binder such as polyethylene glycol or polyvinyl alcohol, and 40-90wt.% of solvent such as methyl alcohol or ethyl alcohol, wherein the quantity of each component is based on the total amount of ceramics(SiC + sintering aid); drying and pressing; sintering at 1800-1900deg.C; thermal treating at 1950-2100deg.C under the pressure(2-300atm.) of N2 or inert gas for 10hrs. to accelerate forming of AlN-SiC solid solution. The resultant silicon carbides comprising platelet SiC particles and high melting boundary phase(mainly Er2O3 or Yb2O3) have more than 6MN/m¬3/2 of fracture toughness and 5000kg/cm¬2 of strength at 1600deg.C.