Estimation of Damage in Refractory Materials after Progressive Thermal Shocks with Resonant Frequency Damping Analysis

This work correlates damping measurements and the microstructural changes in refractory castables after these have been exposed to thermal shocks in air. In accordance with DIN EN 993 – 11, refractory samples based on tabular alumina with the addition of partially stabilized zirconia (PSZ) were progressively subjected to thermal shocks in air at different temperatures (750, 850, 950 and 1050 °C). White fused alumina samples were also exposed to the same thermal shocks at 950 °C. Evaluation of the thermal shock damage to the high-alumina refractory castables was based on the dynamic Young‘s modulus and damping characterization data obtained by means of the impulse excitation technique (IET), in accordance with ASTM E1876 – 07. Scanning electron microscopy (SEM) was also performed to enable understanding of the elastic changes in these refractory formulations. The results show that the damping increase in PSZ castables may be explained by crack nucleation and propagation while such phenomena do not occur in WFA castable.