Characterization of high temperature creep in siliconized silicon carbide using ultrasonic techniques

Ultrasonic velocity and attenuation were both measured on samples containing various degrees of damage due to high temperature creep. These results were compared with parameters associated with creep damage such as strain and cavity formation, in order to better understand the mechanisms of creep in Si/SiC and to determine if ultrasonics can be used in evaluating the severity of damage.

The data indicated that both ultrasonic velocity and attenuation are directly related to creep strain and can be used in evaluating creep damage. Ultrasonic velocity was found to be exponentially related to creep strain. Cavity formation was found not to significantly affect either of the measured ultrasonic properties. The results indicated that Si/SiC behaves as a two phase material in that high frequency ultrasound propagates primarily through the silicon carbide phase and not by the silicon phase.