Evaluation of the Materials Technology Required for a 760ºC Power Steam Boiler John P. Shingledecker and Ian G. Wright Oak Ridge National Laboratory Oak Ridge, TN, USA The U.S. Ultra-supercritical (USC) Steam Boiler Consortium, funded by the U.S. Department of Energy and the Ohio Coal Development Office, has been working for five years to develop the necessary materials technology to construct a steam power boiler with final steam conditions of 760ºC and 35MPa. One large component of this work is to evaluate the properties of the materials chosen for such a boiler. While long-term creep strength of base metal is initially used to set temperatures, stresses, and simple design rules, it is clear from in-plant experience that the limiting material strength factors are not always directly related to base-material strength. Rather, fabrication variables (including weldment properties and cold work effects), component behavior (as manifested in multi-axial creep deformation), and operational issues (including large thermal transients induced during emergency shutdown procedures) all must be considered in evaluating the materials technology for a new high-temperature plant. Much of the understanding of these issues has been gained through in-plant usage of ferrite steels. However, little knowledge exists for in-plant usage of nickel-based superalloys. With this in mind, an extensive effort is being made at the Oak Ridge National Laboratory (ORNL) to evaluate the materials technology being developed in the U.S. USC steam boiler program. This poster illustrates the progress of this work, which includes: long-term creep testing; pressurized creep testing of tube bends to evaluate cold-work effects; weldment creep tests in various geometries to evaluate welds and potential design issues; notched bar and pressurized creep tests for evaluating multiaxial creep effects; and thermal shock testing to evaluate materials resistance to large thermal transients. In addition to the diverse mechanical testing being performed, ORNL also is using computational modeling, electron microscopy studies, and more advanced tools (including synchrotron radiation) to better understand fundamental materials issues, and to provide guidance to the consortium’s efforts. __________________ Research sponsored by the Office of Coal and Power R&D, Office of Fossil Energy, U. S. Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC.
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