Accumulation of Creep Damage in a Siliconized Silicon Carbide

Abstract

The accumulation of creep damage in a siliconized silicon carbide was investigated as a function of applied stress, creep strain, and microstructure. At 1100°C, creep damage was observed to accompany deformation in specimens tested to creep strains greater than 0.10%, under applied stresses greater than 137 MPa. At low creep strains, creep damage occurred in regions of the microstructure of high silicon carbide content. As deformation progressed, creep damage extended into regions of the microstructure of lower silicon carbide content. The area density and area fraction of cavities were found to increase linearly with creep strain. From these results, a threshold stress for the formation of creep damage was determined to be 132 MPa at 1100°C. It was suggested that the formation of creep damage was controlled by the heterogeneous nucleation of cavities at the silicon-silicon carbide interface, with the aid of high localized stresses and iron impurities in the silicon phase.