The density of the sintered composites was measured using the samples cut from the gauge section by the Archimedes method with reagent-grade water as the medium. The crystal structure of the SiC whisker, ZrO2 powder and sintered composites was characterized using X-ray diffractometer (Rigaku D/max-2400,Tokyo, Japan) using CuKa (k = 1.54 Å) radiation. The microstructure of the sintered composites was observed by scanning electron microscopy (SEM, S-4700; Hitachi, Tokyo, Japan) on polished and thermally etched surfaces. The hardness and fracture toughness were determined using indentation technique (HMV-G20ST; SHI-MADZU, Tokyo, Japan) on the polished surface of the composite,using the indentation load of 19.6 N for 15 s. More than ten indentations were made on each sample to obtain reliable data. The indentation size and crack length were measured from SEM images. same power compacts by conventional sintering at 1400◦C for 2 h in a tube furnace.