Microstructural Changes in Inconel^® 740 After Long-Term Aging in the Presence and Absence of Stress

Journal Article · Tue Nov 18 00:00:00 EST 2014 · JOM. Journal of the Minerals, Metals & Materials Society

DOI:https://doi.org/10.1007/s11837-014-1208-4· OSTI ID:1286735

Unocic, Kinga A. ^[1]; Shingledecker, John Paul ^[2]; Tortorelli, Peter F. ^[1]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
2. Electric Power Research Inst. (EPRI), Palo Alto, CA (United States)

The Ni-based alloy, Inconel^® 740, is being extensively examined for use in advanced ultrasupercritical steam boilers because its precipitation-strengthened microstructure appears to offer the necessary creep strength under the high temperatures and pressures (up to 760°C and 35 MPa) needed for high efficiency power generation. However, because this application requires extremely long lifetimes under these conditions (up to 30 years), long-term microstructure stability is a major concern. In this study, results from microstructural analyses of Inconel 740 specimens aged at 700 and 750°C in the presence and absence of creep loading for times up to ~31,000 h are presented. The primary focus was on the development of the eta η (Ni₃Ti) phase and coarsening of coherent γ'-Ni₃(Al,Ti) precipitates and its depletion near eta/matrix interfaces. Finally, however, despite these processes, Inconel 740 showed adequate long-term microstructural stability to assure adequate creep strength for the intended application.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1286735
• Journal Information: JOM. Journal of the Minerals, Metals & Materials Society, Vol. 66, Issue 12; ISSN 1047-4838
• Publisher: Springer
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE