Chromium-molybdenum-aluminum alloys with oxidation-resistance imparted by thermal pre-treatment
AssigneeWisconsin Alumni Research Foundation
InventorsDan Thoma, Michael Niezgoda
Life of this patent
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Abstract
Ternary chromium-molybdenum-aluminum (CrMoAl) alloys that form oxidation-resistant surface films for high-temperature applications are provided. Also provided are methods for thermally pre-treating the alloys to form the oxidation resistant surface films. The surface films have a stratified structure that includes an exterior surface oxide layer comprising chromium oxides and aluminum oxides and an interior aluminum nitride-rich region comprising aluminum nitride precipitates dispersed in a CrMoAl alloy matrix. The interior aluminum nitride precipitates act as oxygen sinks to sequester oxygen diffusing inward into the CrMoAl to prevent further oxidation of the underlying bulk alloy.
Claims20
An article of manufacture comprising a single-phase ternary chromium-molybdenum-aluminum alloy having the composition Cr(1-x-y)MoxAly, where 0.10≤x≤0.20 and 0.10≤y≤0.20.
A method of fabricating an article of manufacture comprising a single-phase ternary chromium-molybdenum-aluminum alloy having the composition Cr(1-x-y)MoxAly, where 0.10≤x≤0.20 and 0.10≤y≤0.20, the method comprising forming a melt composed of stoichiometric quantities of Cr, Mo, and Al and cooling the melt to solidify the single-phase ternary chromium-molybdenum-aluminum alloy having the composition Cr(1-x-y)MoxAly, where 0.10≤x≤0.20 and 0.10≤y≤0.20, wherein the solidified single-phase ternary chromium-molybdenum-aluminum alloy is formed into an article of manufacture by casting and cooling the melt, by forming a coating of the single-phase ternary chromium-molybdenum-aluminum alloy on a substrate, by laser powder bed fusion (LPBF), or by directed energy deposition (DED).
A method of forming an oxidation-resistant chromium-molybdenum-aluminum alloy, the method comprising:
- forming a single-phase ternary chromium-molybdenum-aluminum alloy having the composition Cr(1-x-y)MoxAly, where 0.10≤x≤0.20 and 0.10≤y≤0.20;
- and
- exposing the single-phase ternary chromium-molybdenum-aluminum alloy to a heated atmosphere comprising nitrogen gas and oxygen gas at a temperature, T, and for a time sufficient to form a stratified structure comprising:
- a base layer of a ternary chromium-molybdenum-aluminum alloy;
- a nitride-rich layer over the base layer, the nitride-rich layer comprising aluminum nitride precipitates dispersed in a chromium-molybdenum-aluminum alloy matrix;
- an oxide-rich layer over the nitride-rich layer, the oxide-rich layer comprising aluminum oxide precipitates dispersed in a chromium-molybdenum-aluminum alloy matrix;
- and
- a chromia-rich surface oxide layer over the oxide-rich layer, the chromia-rich surface oxide layer comprising chromium oxides and aluminum oxides.
Dependencies are inferred from the claim text.