Improved aero-thermal resistance capabilities of ZrB2-based ceramics in hypersonic environment for increasing SiC content

The effects of SiC content on aero-thermal resistance capabilities of ZrB2-xSiC-5Y2O3 ceramics (x = 5,10,15,18.5 vol%) in atmospheric re-entry environment were investigated, exposing four hot-pressed button-like specimens to an arc-heated plasma wind tunnel supersonic flow (enthalpy up to 20 MJ/kg). As x increased, the maximum steady-state surface temperature decreased. A 400 K-spontaneous temperature jump was observed on the ZrB2-5SiC-5Y2O3 front surface, with final temperature exceeding 2750 K. The oxide scale consisted in Y-stabilized tetragonal/cubic zirconia, borosilicate glass, and Y2Si2O7 in minor amount. SEM-EDS documented the microstructural differences for varying x, correlating the aero-thermal behavior, including the temperature jump, to borosilicate glass durability.