Microstructure–mechanical properties correlation in siliconized silicon carbide ceramics

The microstructure and high temperature mechanical properties of siliconized silicon carbide ceramics (reaction bonded, reaction formed, and biomorphic SiC) have been investigated. The microstructural differences between these materials have been analyzed. Reaction formed and biomorphic SiC show better, high temperature compressive creep resistance and strength than reaction bonded SiC. Additionally, these two materials show a continuous decrease in the creep rate, which is more pronounced at higher temperature and silicon content. This behavior is explained in detail by using a model of creep controlled by a viscous intergranular phase. The maximum strengths were exhibited by the biomorphic SiC when compressed in the axial direction. The strength of reaction formed SiC is roughly the average between the strength of biomorphic SiC compressed in the axial and radial directions. The dependence of the high temperature compressive strength with the microstructure, and volume fraction of SiC is discussed in terms of the minimum solid area approach.