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MICROSTRUCTURAL EVOLUTION IN ADVANCED BOILER MATERIALS FOR ULTRA-SUPERCRITICAL COAL POWER PLANTS

WU, QUANYAN
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154363707

Abstract Details

2006, PhD, University of Cincinnati, Engineering : Materials Science.
The goal of improving the efficiency of pulverized coal powerplants has been pursued for decades. The need for greater efficiency and reduced environmental impact is pushing utilities to ultra supercritical conditions (USC), i.e. steam temperatures approaching 760°C under a stress of 35 MPa. The long-term creep strength and environmental resistance requirements imposed by these conditions are clearly beyond the capacity of the currently used ferritic steels and other conventional alloys. As part of a large DOE-funded consortium, new and existing materials based on advanced austenitic stainless steels and nickel base superalloys are being evaluated for these very demanding applications.In the present work, the nickel base superalloys of Inconel 617, CCA617, Haynes 230 and Inconel 740, and austenitic alloys Super 304H and HR6W, were evaluated on their microstructural properties over elevated temperature ageing and creep rupture conditions. The materials were aged for different lengths of time at temperatures relevant to USC applications, i.e., in the range from 700 to 800°C. The precipitation behaviors, namely of the γ’, carbides and γ phase in some conditions in nickel base superalloys, carbides in Haynes 230, Cu-rich precipitates in Super 304H and Laves phase particles in HR6W, were studied in detail using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and related analytical techniques. Particular attention has been given on the structure, morphology and compositional distinctiveness of various phases (including γ, γ’, carbides, secondary phase precipitates, and other types of particles) and their nature, dislocation structures and other types of defects. The results were presented and discussed in light of associated changes in microhardness in the cases of aged samples, and in close reference to mechanical testing (including tensile and creep rupture tests) wherever available. Several mechanical strengthening mechanisms were proposed and the results were calculated using the corresponding modeling equations. They were then compared to the mechanical properties recorded separately. These findings documented the microstructural responses of candidate alloys for USC applications from sample treatments that were related to the conditions of that from USC, and thus provided inputs to both assessment and predictions of mechanical behaviors of these alloys under USC service conditions.
Dr. Vijay Vasudevan (Advisor)
199 p.
Engineering, Materials Science
nickel base superalloys; microstructure; transmission electron microscopy; high temperature strength; Inconel 617; CCA617; Haynes 230; Inconel 740; Super 304H; HR6W

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Citations

  • WU, Q. (2006). MICROSTRUCTURAL EVOLUTION IN ADVANCED BOILER MATERIALS FOR ULTRA-SUPERCRITICAL COAL POWER PLANTS [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154363707

    APA Style (7th edition)

  • WU, QUANYAN. MICROSTRUCTURAL EVOLUTION IN ADVANCED BOILER MATERIALS FOR ULTRA-SUPERCRITICAL COAL POWER PLANTS. 2006. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154363707.

    MLA Style (8th edition)

  • WU, QUANYAN. "MICROSTRUCTURAL EVOLUTION IN ADVANCED BOILER MATERIALS FOR ULTRA-SUPERCRITICAL COAL POWER PLANTS." Doctoral dissertation, University of Cincinnati, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154363707

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Cincinnati and OhioLINK.
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