Ablation behavior of ZrB2-SiC ultra high temperature ceramics under simulated atmospheric re-entry conditions

ZrB2-20vol%SiC ultra high temperature ceramic (UHTC) was prepared by hot-pressing. Ablation tests of the flat-face models were conducted under ground simulated atmospheric re-entry conditions using arc-jet testing with heat fluxes of 1.7 MW/m(2) and 5.4 MW/m(2) under subsonic conditions, respectively. There was little weight or configuration change after ablation at a heat flux of 1.7 MW/m(2). However, ZrB2-SiC composite underwent severe ablation and whose surface temperatures exceeded 2300 degrees C at a heat flux of 5.4 MW/m(2). Sharp-shape leading edge models were ablated under supersonic conditions with the stagnation pressure and Mach number of 1.2 atm and 2.7 M, respectively, and sharp-shaped leading edge C/SiC models were also ablated under the same condition for comparison. ZrB2-SiC composite exhibited an excellent thermal-oxidative and configurational stability in the simulated re-entry environment compared with C/SiC material. Results indicate that ZrB2-SiC ultra high temperature ceramics are the potential candidates for leading edges. The temperature limit for UHTC is controlled by the softening and degradation of the formed oxide scale. (c) 2008 Elsevier Ltd. All rights reserved.