Processing, damage tolerance and crack healing in the silicon carbide fabric-covered silicon carbide composite

摘要

SiC fabric with or without alumina powder was joined to the surfaces of SiC compact under the applied pressures of 5-39 MPa. The stress-strain curve, strength, damage tolerance using Vickers indentor and crack healing effect were investigated for both the SiC with and without SiC fabric layers. The strength of monolithic SiC was greatly decreased by the surface damage but easily recovered to the original strength by the healing at a relatively low temperature of 1100°C in air. When a simultaneous processing using an SiC compact covered with SiC fabric was applied, which promoted the densification of inside SiC compact, the surface SiC fabric dissolved in the liquid of sintering additives included in the SiC compact during the hot-pressing at 1950°C. The mechanical properties of this type composite were similar to those of monolithic SiC compact. The SiC fabric joined to dense SiC compact under a low applied pressure at 1300-1600°C prevented the propagation of the cracks formed by Vickers indentor and showed a significant nonlinear stress-strain curve. As a result, no change in the strength was measured before and after the introduction of cracks. However, increased joining pressure resulted in the creep rupture of dense inside SiC compact. Decrease of the joining temperature and decrease of the joining pressure were effective to increase the flexural strength.