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Development of High-Performance Ni-Fe-based Superalloys for Land-Based Industrial Gas Turbine Wheels

Mukhopadhyay, Semanti
http://rave.ohiolink.edu/etdc/view?acc_num=osu1689911098528297

Abstract Details

2023, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
Background: A land-based Industrial gas turbine (9HA) lies at the heart of two world records for efficient power generation. Based on thermodynamic principles, the efficiency of gas turbines is dictated by their operating temperatures. Thus, the drive for more efficient power generation ultimately revolves around increasing the operating temperature of gas turbine engines. Specifically, developing a more efficient powerplant requires a gas turbine wheel operating at or above 1200°F (649°C). However, because of the massive size of such turbine wheels (average reported diameters are about 40''), no current superalloy can meet the above temperature goals. In fact, because of its large size, maintaining microstructural stability during the thermomechanical processing of gas turbine wheels is a herculean task. The Unknown: However, most polycrystalline superalloys, including the current state-of-the-art wheel material (Alloy 706), exhibit a hierarchy of microstructures spanning multiple length scales. In that case, microstructural optimization reliant on intragranular precipitate phases alone may not achieve the desired high-temperature performance. Objectives and Findings: The present research focused on optimizing the microstructure of polycrystalline superalloys through concurrent multi-scale structure-property correlation studies. Specifically, I looked at three aspects of the hierarchical nature of the microstructure observed in any typical polycrystalline superalloy: (1) intragranular precipitate distribution, (2) precipitation and consequent precipitate-free zones near annealing twin boundaries, and (3) secondary precipitate evolution on high angle grain boundaries. Our results indicate that unless alloy development strategies utilize a simultaneous optimization approach for these three aspects, achieving the desired high performance in Ni-Fe-based superalloys is difficult. Results from several advanced characterization experiments using various in-situ and ex-situ characterization techniques, Such As Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Electron Dispersive Spectroscopy (EDS), are presented to support our findings.
Michael J. Mills (Advisor)
Materials Science
Superalloys; 718; Electron Microscopy; Annealing Twin Boundary; Strain Localization; Characterization; Deformation Mechanism, Creep, Tensile Test, Ni-Fe-based Superalloys, DC-STEM, STEM-HAADF, Aberration Corrected STEM, STEM-EDS, Alloy Development, Microstructural Engineering

Recommended Citations

Citations

  • Mukhopadhyay, S. (2023). Development of High-Performance Ni-Fe-based Superalloys for Land-Based Industrial Gas Turbine Wheels [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1689911098528297

    APA Style (7th edition)

  • Mukhopadhyay, Semanti. Development of High-Performance Ni-Fe-based Superalloys for Land-Based Industrial Gas Turbine Wheels. 2023. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1689911098528297.

    MLA Style (8th edition)

  • Mukhopadhyay, Semanti. "Development of High-Performance Ni-Fe-based Superalloys for Land-Based Industrial Gas Turbine Wheels." Doctoral dissertation, Ohio State University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=osu1689911098528297

    Chicago Manual of Style (17th edition)

osu1689911098528297
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This open access ETD is published by The Ohio State University and OhioLINK.
Release 3.2.12