Oxidation of PM1000 and C/C-SiC exposed to Highly Dissociated Oxygen and Nitrogen Flows

The present work investigates the formation and stability of different oxides on PM1000, an Oxide dispersion-strengthened (ODS) Ni-Cr superalloy, and on SiC coated C/C-SiC after being exposed to highly dissociated nitrogen and oxygen flows in a Plasma Wind Tunnel (PWT). PM1000 and C/C-SiC are candidate materials for reentry vehicles Thermal Protection System (TPS) and were used e.g. on the European eXPErimental Re-entry Testbed (EXPERT). The surface characterisation covers the identification of the oxide layers formed on the specimen's surface via X-ray Diffraction (XRD) and Energy-Dispersive X-ray spectroscopy (EDX). Grain sizes are assessed from XRD patterns and different topographical features are identified for Cr2O3 and NiO on PM1000 samples from Secondary Electron Microscopy (SEM). Surface spectral and total normal emissivities of the different oxides are assessed showing a significant dependency on the oxide, which is verified with previous investigations on ground and with flight data from the FOTON capsule.