Environmental response characteristics of substoichiometric ZrCx exposed to inductively coupled air plasma

Abstract

An inductively coupled plasma jet was used to elucidate fundamental response characteristics of substoichiometric zirconium carbide in a hypersonic-relevant environment. Specimens were subjected to high-enthalpy air at surface temperatures between 1850 and 2525 °C. Corrosion progressed linearly, though the most extreme condition exhibited diffusion-limiting behavior. Surface cracking shifted to porosity at higher temperatures, potentially indicating a shift in gas exchange character. Spectral emittance and optical bandgap differences were attributed to nitrogen, carbonates, and surface annealing. Bulk scale porosity decreased and developed gradients at higher temperatures. Final reaction products were identified as oxides and oxynitrides, while interfaces included oxynitrides, oxycarbides, carbonitrides, and carbon at lower temperatures. Plasma dwell time influenced local electron density of zirconium, possibly due to vacancies mediated by high temperatures and free electrons. This analysis quantifies high degrees of spatial and temporal dependence of composition and microstructure, necessitating multiphysics testing for efficient design and innovation of refractories for hypersonics.