Thermo-chemical surface instabilities of SiC-ZrB2 ceramics in high enthalpy dissociated supersonic airflows

Abstract The response of three different SiC-ZrB 2 ceramics obtained by hot-pressing was studied at typical conditions of thermal protection systems of a re-entry spacecraft. Button-like lab-scale demonstrators were manufactured and tested in high enthalpy dissociated supersonic airflows using an arc-jet ground facility. Under severe aero-heating of up to 21 MJ/kg of specific total enthalpy and 3.5 MW/m 2 of (cold-wall) heat flux the SiC-ZrB 2 UHTC buttons endured rather well, though thermo-chemical surface instabilities started taking place for side wall surface temperatures of some buttons above 2050 K. The experimental determinations of the surface temperature, correlated to the microstructure changes occurred during testing, allowed to interpret the observed phenomena. Potentials and limits of the oxidation-resistant SiC-ZrB 2 system to withstand such extreme conditions were outlined.