Abstract
The oxidation behavior of an ultra-high temperature ceramic (UHTC) based on HfB2 with 20vol% SiC and was studied following two 10 min arc-jet test cycles with nominal heat flux of 350 W cm−2, stagnation pressure of 7 kPa, and a sustained peak surface temperature of 2360 °C. Microstructure characterization revealed a modified, layered structure comprising ∼390 μm of porous HfO2 at the surface and an underlying ∼740 μm porous region containing un-oxidized HfB2 over the bulk UHTC, unaffected below the oxidation front. The SiC presumably undergoes active oxidation, as commonly reported for temperatures above ∼1600 ± 100 °C. However, unlike typical of exposures below ∼2000 °C no molten silicate phase was present at the surface to mediate the exchange of oxidant and gaseous reaction products. Additionally, a HfC impurity phase oxidizes concurrently with SiC rather than HfB2. A thermodynamic analysis is provided to explain the observed behavior and the differences with lower temperature scenarios in the literature.
Original language | English (US) |
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Pages (from-to) | 3697-3707 |
Number of pages | 11 |
Journal | Journal of the European Ceramic Society |
Volume | 36 |
Issue number | 15 |
DOIs | |
State | Published - Nov 1 2016 |
Bibliographical note
Publisher Copyright:© 2016 Elsevier Ltd
Keywords
- Hafnium boride
- Hafnium carbide
- Oxidation
- Silicon carbide
- Ultra high temperature ceramic