Project No: FE0005868
Performer: University of Tennessee


Contacts
Robert Romanosky
Crosscutting Research Technology
Manager
National Energy Technology Laboratory
3610 Collins Ferry Road
P.O. Box 880 PO3D
Morgantown, WV 26507-0880
304-285-4721
Robert.Romanosky@netl.doe.gov

Richard Dunst
Project Manager
National Energy Technology Laboratory
626 Cochrans Mill Road
P.O. Box 10940 MS 922-273C
Pittsburgh, PA 15236-0940
412-386-6694
Richard.Dunst@netl.doe.gov

P. K. Liaw

Principal Investigator
427-B Dougherty Engineering Bldg.
Department of Materials Science and
Engineering
University of Tennessee
Knoxville, TN 37996-2200
865-974-6356
pliaw@utk.edu

Duration
Award Date:  10/01/2010
Project Date:  12/31/2014

Cost
DOE Share: $1,200,000.00
Performer Share: $333,680.00
Total Award Value: $1,533,680.00

Performer website: University of Tennessee - http://www.utk.edu

Crosscutting Research - Plant Optimization Technologies

Computational Design of Creep-Resistant Alloys and Experimental Validation in Ferritic Superalloys

Project Description

In order to improve the thermal efficiency of steam turbines and reduce carbon dioxide emissions by fossil-energy power plants, steam temperatures and pressures in ultra-supercritical steam turbines must be increased to 760 degrees Celsius (°C) and 35 megapascals (MPa), respectively.

The elevated temperature results in the development of a critical issue related to the creep strength—or ability to withstand temperature and strain induced deformation leading to failure—of current ferritic steels. This project will address this issue by targeting the development of computational tools to design and optimize ferritic superalloys. These tools will be used to measure microstructural characteristics of selected alloys to quantify the links among materials processing, microstructures, material properties, and performance. The information generated through utilizing these tools will allow researchers to gain an understanding of creep behavior in these high-temperature alloys.

Figure 1. Dispersion of B2-NiAl-type precipitates in a bcc-Fe matrix (G. Ghosh, unpublished research, NU).


Program Background and Project Benefits

The Advanced Research Materials Program addresses materials requirements for all fossil energy systems, including materials for advanced power generation technologies, such as coal gasification, heat engines, such as turbines, combustion systems, fuel cells, carbon capture technologies, and coal fuels technologies. The program is led by the National Energy Technology Laboratory (NETL) within the Office of Fossil Energy (FE) of the U.S. Department of Energy (DOE). It is implemented through research and development agreements with other national laboratories, industry, and academia.

The program strategy is to provide a materials technology base to assure the success of advanced power generation systems being pursued by DOE-FE. These systems, including advanced ultra-supercritical combustion systems, integrated gasification combined cycle plants, fuel cells, gas turbines, and carbon capture and storage technology, are being developed to fulfill the DOE’s mission to achieve near-zero emissions for power generation. The foundation of this technology, centered in high-temperature materials research, includes the development of new materials that have the potential to improve the performance and/or reduce the cost of existing fossil fuel technologies; development of materials for new systems and capabilities; development of a technology base in the synthesis processing life cycle analysis; and performance characterization of advanced materials.

In accordance with this goal, NETL is working with the University of Tennessee, Northwestern University, and the University of California, Berkeley, on the advancement of computational capabilities for the development of materials for the next generation FE power systems.

NETL is developing a technology base for the highly efficient, near-zero-emissions power plants of tomorrow. This project will make progress toward providing improved materials and computational modeling of these materials to allow for future implementation in fossil energy conversion technologies. These enhanced ferritic alloys and a better understanding of their creep behavior will enable a higher standard of fossil energy conversion to be realized, which will provide an overall higher energy output.

Goals and Objectives

The goal of this project is to develop computational tools required to design and optimize ferritic superalloys needed for fossil-energy power plants to operate at advanced steam turbine operating conditions.

The following objectives will be completed:



Accomplishments

Researchers have developed a Calculation of Phase Diagrams (CALPHAD) model of the aluminum-nickel-titanium (Al-Ni-Ti) system. The results of this model compare favorably to known phases and results of other modeling approaches. Researchers have calculated coherent interfacial energies involving intermetallic precipitates in iron-nickel-titanium-aluminum (Fe-Ni-Ti-Al) superalloys using first-principles methods. This data helps in the understanding and future modeling of the behavior of these alloys in advanced energy systems.

Researchers have initiated a systematic compression creep study of a complex alloy system known as FBB8 [Fe-6.5Al-10Cr-10Ni-3.4Mo-0.25Zr-0.005B, weight percent (wt.%)]. They have built upon the work of previous studies of the FBB8 alloy by investigating the creep properties of FBB8 with titanium additions of 2 and 6 wt.%. Several valuable results were obtained from this study. Both FBB8+2%Ti and FBB8+6%Ti were found to be more creep resistant at 700°C than the previously studied FBB8 alloy. At a given stress, the creep strain rate of the FBB8+6%Ti is approximately 10–50 times lower than that of the FBB8 alloy. The creep strain rate of the FBB8+2%Ti is three orders of magnitude lower, compared to the FBB8 alloy [in the stress range from 140 to 170 megapascals (MPa)]. In addition, significant increases in the threshold stress, below which no measureable creep strain is obtained in the laboratory time-scale, were observed in both Ti-bearing alloys. The threshold stress improves from 69 MPa in the FBB8 alloy to 100 and 140 MPa in the FBB8+6%Ti and FBB8+2%Ti alloys, respectively.