Sintering and properties of Ultra High Temperature Ceramics for aerospace applications

The Ultra High Temperature Ceramics (UHTCs) represent a very interesting family of materials and therefore they are the subject of increasing attention from 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 lifetime. 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. Thus, in diborides-based compounds, at temperatures above 1600°C, the oxidation resistance is generally much better than that of traditional SiC-based ceramics thanks to the formation of multi-oxide scales composed of a refractory oxide (skeleton) and a glass component. Since 2006, Onera actively takes part in several programmes to investigate such materials as well for hypersonic civil flights as for propulsion systems. Diverse manufacturing processes and compositions have been studied in theses projects. In this paper, we present different type of materials developed for some specific applications: leading edges, air intakes, uncooled injectors of future hypersonic civil aircrafts flying up to Mach 6.