Fabrication of Nanograined Silicon Carbide by Ultrahigh‐Pressure Hot Isostatic Pressing

Abstract

Dense nanograined SiC ceramics were obtained by using hot isostatic pressing (HIP). The starting powder was ultrafine β‐SiC powder, which had a mean particle size of 30 nm and contained 3.5 wt% free carbon. SiC powders‐both boron‐doped and undoped‐were densified via HIP under an ultrahigh pressure of 980 MPa at a temperature of 1600°C. Both doped and undoped SiC attained the same density (3.12 g/cm 3 ) (relative density of 97.1%). The average grain sizes of boron‐doped and undoped SiC were 200 and 30 nm, respectively. The compressive flow stress of undoped SiC was 3 times higher than that of boron‐doped SiC at temperatures of 1800° and 1700°C; however, the flow stresses of both materials were almost the same at 1600°C. The HIPed SiC that was doped with boron could be deformed at a stress that was one‐third lower than that of hot‐pressed boron‐ and carbon‐doped SiC with a grain size of 0.8 µm.