Performance of Wrought Superalloys in Extreme Environments
- ORNL
As power generation systems move towards higher efficiency operation above 700 °C, wrought superalloys are the leading structural alloy candidates, including precipitation strengthened (PS) alloys 740 and 282 for the highest temperatures. To evaluate the performance of these alloys for these applications, a range of 500–5000 h evaluations have been conducted in environments including steam, supercritical CO2 (sCO2) and simulated combustion exhaust with H2O and/or SO2 at 700–800 °C and compared to baseline exposures in laboratory air and 1 bar CO2. These alloys primarily rely on the formation of an external Cr-rich oxide layer or scale for environmental protection and the reaction rates in all of these conditions are similar and relatively low. However, compared to a conventional solid solution strengthened alloy, like 625, the mass gains are higher for PS alloys due to the internal oxidation of the γ' forming additions, Al and Ti. Post-exposure characterization has quantified the reaction products and the depth of internal oxidation is not a concern and does not appear to increase above the baseline behavior in laboratory air. Likewise, there is no indication of internal carburization in the sCO2 environment at 750 °C/300 bar. The addition of 0.1% SO2 in CO2-10% H2O at 800 °C actually suppressed the internal oxidation at 1 bar but SO2 may be a concern when the total pressure is higher.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Fossil Energy (FE)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1471929
- Country of Publication:
- United States
- Language:
- English
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