Fracture Toughness Behavior Of ß-Sialon Composites with Carbon-Coated Silicon Carbide Whiskers

″s-SIALON″ matrix composites with 10-30 vol% silicon carbide (SiC) whiskers, both uncoated and coated with carbon, were hot isostatically pressed (HIP′ed) by the glassencapsulation method. TEM micrographs of the composites with carbon-coated whiskers showed that carbon layers remain between the whiskers and p-sialon grains. The fracture toughness of composites with 10-30 vol% carbon-coated whiskers increased with increasing whisker content, but composites with 10 vol% whiskers had almost the same toughness as monolithic s-SIALONs. Composites with 30 vol% uncoated whiskers had slightly less toughness than the monolithic sialons. The 100-hr oxidation test at 1350°C in air confirmed that the oxidation resistance of the composites with carbon-coated whiskers is excellent and equivalent to that of monolithic s-SIALON s.