Selective active oxidation in hafnium boride-silicon carbide composites above 2000 °C

David L. Poerschke, Mark D. Novak, Najeb Abdul-Jabbar, Stephan Krämer, Carlos G. Levi

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

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 languageEnglish (US)
Pages (from-to)3697-3707
Number of pages11
JournalJournal of the European Ceramic Society
Volume36
Issue number15
DOIs
StatePublished - Nov 1 2016

Keywords

  • Hafnium boride
  • Hafnium carbide
  • Oxidation
  • Silicon carbide
  • Ultra high temperature ceramic

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