Ta_xHf_(1-x)B_2-SiC multiphase oxidation protective coating for SiC-coated carbon/carbon composites

摘要

A Ta_xHf_(1-x)B_2-SiC coating was prepared by in-situ reaction method on SiC coated C/C composites. Ta_xHf_(1-x)B_2 phase is the form of solid solution between TaB_2 and HfB_2. Isothermal oxidation behavior at 1773 K and ablation behavior of the coated C/C were tested. Ta_xHf_(1-x)B_2-SiC/SiC coating could protect the C/C from oxidation at 1773 K for 1480 h and ablation above 2200 K for 40 s. During oxidation, oxides of Ta and Hf atoms exist as "pinning phases" in the compound glass layer consisted of outer Ta-Si-O compound silicate layer and inner SiO_2 glass layer, which was responsible for the excellent oxidation resistance.