Thermo-chemical surface instabilities of SiC-ZrB 2 ceramics in high enthalpy dissociated supersonic airflows

Abstract

The response of three different SiC-ZrB2 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 21MJ/kg of specific total enthalpy and 3.5 MW/m2 of (cold-wall) heat flux the SiC-ZrB2 UHTC buttons endured rather well, though thermo-chemical surface instabilities started taking place for side wall surface temperatures of some buttons above 2050K. 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-ZrB2 system to withstand such extreme conditions were outlined