RMI- C/C-SiC-ZrSi2 composite serving in inert atmosphere up to 2100 °C: Thermal shock resistance, microstructure and damage mechanism

Abstract

Thermal shock resistance (TSR) and related damage mechanism of C/C-SiC-ZrSi2 composites produced via Si-Zr alloy melt infiltration was investigated using a newly-developed equipment at superior high temperatures up to 2100 °C in an inert atmosphere. TSR was characterized by the residual strength and mass variation of the composites subjecting to thermal shock tests with different cycles and temperatures. Results indicated that TSR and damage of the composites were closely dependent on the testing cycles and especially temperatures. Strength of the composites was generally decreased with the increasing tested cycles. Slight strength reduction subjected to the low testing temperatures (<1300 °C) were detected because almost no crack propagation occurred in the C-SiC-ZrSi2 matrix. At relatively higher temperatures (1300–1700 °C), thermal stress caused by temperature gradient and thermal expansion coefficient mismatch was greatly increased. Consequently, matrix crack propagating into the intra fiber bundles and interfacial layers with much longer propagation paths were generated. Repeated thermal stress during cycled thermal shock tests weakened the interface bonding in the composites, and resulted in the delamination and interfacial debonding with obvious strength degradation. At ultrahigh temperatures (≥1700 °C), matrix pores were produced due to ZrSi2 evaporation. Combining effect by thermal stress and ZrSi2 evaporation caused severe damage to the composites with sharp strength reduction.