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Electron Probe Microanalysis (EPMA) Characterization of Scales Formed on Laves Phase Reinforced Cr Alloys at 1100°C in Air

Published online by Cambridge University Press:  02 July 2020

L.R. Walker  and
M.P. Brady
L.R. Walker
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN37831-6064
M.P. Brady
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN37831-6064
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Extract

Laves phase (Cr2X) strengthened Cr solid solution [Cr(X)]-based alloys are under development for a variety of high-temperature structural applications. Among the most promising alloys are castings based on the Cr(Ta)-Cr2Ta eutectic, which exhibit room-temperature fracture toughness in the 10-12 MPa√m range and creep rupture lives in excess of 1000 h at 1000° (138 MPa) in air. These alloys exhibit superior high-temperature oxidation resistance to previously developed Cr(Nb)-Cr2 Nb based alloys despite the general similarities of Ta and Nb. In order to optimize high-temperature oxidation resistance an understanding of why the Cr(Ta)-Cr2Ta alloys are more oxidation resistant is needed. Detailed EPMA characterization of the oxidized scaleswas initiated as a first steptowards gaining this understanding.

Fig. 1 shows a backscattered electron image of cast and heat treated and heat treated Cr-10Nb at.% after a 6 cycle, 120 h exposure at 1100°C in humid air. Most of the coupon was converted to a complex mixture of Cr-, Nb-, and Cr+ Nb- oxides.

Type
Oxidation/Corrosion
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 852 - 853
Copyright
Copyright © Microscopy Society of America

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References

1. Brady, M.P., Zhu, J.H., Liu, C.T., Tortorelli, P.F., Wright, J.L., and Carmichael, C.A., in Proceedings of the Twelfth Annual Conference on Fossil Energy Materials, Knoxville, TN, May 12-14, 1998, Judkins, R.R., Compiler, paper 4.9 (1998).Google Scholar

2. McKamey, C.G. and Liu, C.T., unpublished results, Oak Ridge National Laboratory (1998).Google Scholar