ZrB2-SiC Sharp Leading Edges in High Enthalpy Supersonic Flows

Aero-thermodynamic tests have been carried out in an arc-jet supersonic plasma wind tunnel using a very sharp wedge made of ultra-high temperature ceramic (UHTC)in the ZrB2-SiC system. The comparison with a lower thermal conductivity ceramic material (Si3N4-MoSi2) with the same sharp shape,pointed out at the performance advantages of the UHTC material. When subjected to heat fluxes in the order of 7 MW/m2,the surface temperature of the UHTC wedge increased up to 2450°C near the leading edge. The present study demonstrated that the high thermally conductive UHTC survived such extreme conditions by re-distributing heat over colder regions downstream of the sharp tip. As a consequence, radiative equilibrium temperatures in the range 1400°C-1650°C were established over 85% of the exposed surface. On the other hand, the less thermally conductive Si3N4-MoSi2 material failed to withstand the same heat flux and underwent partial melting with significant mass loss. The post-test microstructural observations of the UHTC wedge proved to be a fundamental source of information which was input into a Computational Fluid Dynamics (CFD) code and by a thermal simulation software to simulate the experimental tests and correlate the in situ observations of the material evolution during testing.