Oxidation resistance of multi-component carbide and boride UHTCS

Conference Dates

September 17-20, 2017


Bulk samples of high entropy ultra-high temperature ceramics (UHTCs) of the composition (HfNbTaTiZr)C and (HfNbTaTiZr)B2 were fabricated via high energy ball milling and spark plasma sintering. Oxidation behavior of this new class of UHTCs was tested at 1500⁰C and 1700⁰C using a resistive heating apparatus in 1 atmosphere reduced PO2 oxygen/argon gas mixtures for times between 5 minutes and 1 hour. Oxidation kinetics were determined from the variation of oxide thickness vs. time. Oxide composition and morphology were characterized using XRD, SEM, and EDS. A nearly continuous layer of complex oxides was observed on the surface, and a subsurface layer showed evidence of selective grain boundary oxidation. Rapid oxidation rates were observed for both carbide and boride at 1500⁰C, even in 1% O2/balance Ar. This work serves to further elucidate the oxidation behavior of a new class of ceramics that are proposed for ultra-high temperature applications where oxidation properties are of key importance.

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