A new strategy to intrinsically protect refractory metal based alloys at ultra high temperatures

•The protectiveness of refractory metal-based alloys can be realized if alloys contain required concentrations of Cr and Ta.•The oxide CrTaO4 reliably protects the refractory equatomic high entropy alloy Ta-Mo-Cr-Ti-Al by formation of a CrTaO4 scale.•CrTaO4 scale forms in a wide temperature range fr...

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Bibliographic Details
Published in:Corrosion science 2020-04, Vol.166, p.108475, Article 108475
Main Authors: Gorr, Bronislava, Müller, Franz, Schellert, Steven, Christ, Hans-Jürgen, Chen, Hans, Kauffmann, Alexander, Heilmaier, Martin
Format: Article
Language:English
Subjects:
Chromium
Cooling rate
CrTaO4
High entropy alloys
High temperature materials
Molybdenum
Oxidation
Oxidation resistance
Protective oxides
Refractory high entropy alloys
Resistance
Tantalum
Titanium
Ultrahigh temperature
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Summary:•The protectiveness of refractory metal-based alloys can be realized if alloys contain required concentrations of Cr and Ta.•The oxide CrTaO4 reliably protects the refractory equatomic high entropy alloy Ta-Mo-Cr-Ti-Al by formation of a CrTaO4 scale.•CrTaO4 scale forms in a wide temperature range from 500 °C to 1500 °C exhibiting low growth rates.•CrTaO4 possesses high adhesive properties.•Wide stability range of the stoichiometric composition that suppresses the formation of other (non-protective) oxides. Poor oxidation resistance represents one of the main shortcomings of refractory metal based alloys. This work shows an innovative way to intrinsically protect such materials. Our approach relies on the alloying with Cr and Ta allowing the formation of CrTaO4. The CrTaO4 scale formed on the novel refractory equiatomic high entropy alloy Ta-Mo-Cr-Ti-Al reveals a unique combination of the following properties: (i) easy formation in a wide temperature range from 500 °C to 1500 °C, (ii) excellent adherence after cooling, (iii) low growth rates, and (iv) wide stability range of the stoichiometric composition that suppresses the formation of non-protective oxides.
ISSN:0010-938X
1879-0496
DOI:10.1016/j.corsci.2020.108475