UHTC coatings for aerospace applications

During atmospheric re-entry, space shuttles are exposed to high temperatures above 2000 °C. Currently interesting thermostructural materials such as carbon/carbon composites, or Ceramic Matrix Composites (CMC) can encounter oxidation problems at these temperature levels. Adding a protective barrier is a means of preserving the integrity of spacecraft. Ultra-High Temperature Ceramics (UHTC) seem to be good candidates. Due to their high melting points, UHTC materials require relevant processes to be applied on thermostructural materials.

The scope of this study was dedicated to the implementation of plasma spray coating technology. ZrB₂-based coatings were sprayed under an inert atmosphere. Additives such as silicon carbide (SiC) were studied. Coatings were tested both using the MESOX set-up (air plasma), one device of the PROMES-CNRS solar facilities in Odeillo, and under a plasma jet in Vulcain set-up, one device of the CEA facilities. Materials were analyzed before and after oxidation tests by scanning electron microscopy, X-ray diffraction and electron probe microanalyser.