Abstract
A new test rig was developed to conduct creep evaluation in steam. The isothermal creep performance for ferritic 9Cr and ferritic/martensitic Gr.91 steels was superior at 650 °C in steam than in air. Microstructure characterization revealed the presence of an adherent and continuous (Fe,Cr)-rich inner oxide layer because of crack healing by re-oxidation. Stress calculation based on a composite structure showed that the longer lifetimes in steam were likely due a transfer of load from the alloy to the inner scale. However, a significant decrease of the Gr91 creep lifetime was observed in steam at 650 °C when the specimens were thermally cycled every 10 h. This could be explained by localized cracking of the load-bearing inner layer.
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Acknowledgements
The authors would like to acknowledge J. Moser, T. Lowe and T. Jordan for assistance with the experimental work. They also thank M. Brady, Y. Yamamoto and B.A. Pint for reviewing the manuscript. This material is based upon work supported by the US Department of Energy, Office of Fossil Energy, under the Crosscutting Research Program.
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Dryepondt, S., McClurg, D.R. Creep Performance of Advanced 9Cr–1Mo Steels in Steam Environment. Oxid Met 87, 481–490 (2017). https://doi.org/10.1007/s11085-017-9753-1
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DOI: https://doi.org/10.1007/s11085-017-9753-1