Ultra High Temperature Ceramics for aerospace applications

The Ultra High Temperature Ceramics (UHTCs) are of great interest for different engineering sectors and notably the aerospace industry. Indeed, hypersonic flights, re-entry vehicles, propulsion applications and so on, require new materials that can perform in oxidizing or corrosive atmospheres at temperatures higher than 2000°C and sometimes, for long life-time. To fulfil these requirements, UHTCs seems to be one of the most promising candidates and among this family, ZrB2 and HfB2-based composites are the most attractive. Since 2006, Onera actively takes part in several programs to investigate such materials as well for hypersonic civil flights as for propulsion systems. Several manufacturing processes and compositions have been studied to assess the influence of the microstructure and the composition on mechanical properties and oxidation behaviour. For example, HfB2/SiC composites exhibit high mechanical properties at room temperature (Hv10 = 17.5 GPa and K1C = 6.7 MPa.m1/2) and high oxidation resistance above 1600°C compared to traditional SiC-based ceramics thanks to the formation of multi-oxide scales composed of a refractory oxide (skeleton) and a glass component.