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Microstructure and High Temperature Oxidation Behavior of Cr-W Alloys

Description: Cr alloys containing 0-30%W by weight were investigated for use in elevated temperature applications. The alloys were melted in a water-cooled, copper-hearth arc furnace. Microstructure of the alloys was characterized using x-ray diffraction, scanning electron microscopy, and light microscopy. A pseudocyclic oxidation test was employed to study scale formation at 1000ºC in dry air. The scale was predominantly chromia and spalled upon cooling. Alloying with aluminum up to 8 weight percent reduced the spalling drastically. Furthermore, aluminizing the surface of the Cr-W alloys completely stopped the spalling.
Date: February 1, 2007
Creator: Dogan, O.N.
Partner: UNT Libraries Government Documents Department

Metallic Membrane Materials Development for Hydrogen Production from Coal Derived Syngas

Description: The goals of Office of Clean Coal are: (1) Improved energy security; (2) Reduced green house gas emissions; (3) High tech job creation; and (4) Reduced energy costs. The goals of the Hydrogen from Coal Program are: (1) Prove the feasibility of a 40% efficient, near zero emissions IGCC plant that uses membrane separation technology and other advanced technologies to reduce the cost of electricity by at least 35%; and (2) Develop H{sub 2} production and processing technologies that will contribute {approx}3% in improved efficiency and 12% reduction in cost of electricity.
Date: February 26, 2012
Creator: Dogan, O.N.; Howard, B.H. & Alman, D.E.
Partner: UNT Libraries Government Documents Department

Microstructure and Corrosion Behavior of the Cu-Pd-X Ternary Alloys for Hydrogen Separation Membranes

Description: CuPd alloys are among the most promising candidate materials for hydrogen separation membranes and membrane reactor applications due to their high hydrogen permeability and better sulfur resistance. In order to reduce the Pd content and, therefore, the cost of the membrane materials, efforts have been initiated to develop CuPdM ternary alloys having a bcc structure. The advantages of having Pd as a hydrogen separation membrane are: (1) high hydrogen selectivity; and (2) high hydrogen permeability. The disadvantages are: (1) high cost; (2) hydrogen embrittlement ({alpha} {yields} {beta} Pd hydride); and (3) sulfur poisoning. Experiments (XRD, SEM/EDS) verified that Mg, Al, La, Y and Ti are promising alloying elements to expand the B2 phase region in Cu-Pd binary system. HT-XRD showed that the B2 to FCC transition temperatures for Cu-Pd-X (X = Mg, Al, La, Y and Ti) are higher than that of Cu-Pd binary alloys. While the Cu-50Pd alloy had the highest corrosion resistance to the H2S containing syngas, the Cu-Pd-Mg alloy had a comparable resistance.
Date: February 26, 2012
Creator: Dogan, O.N.; Gao, M.C. & Howard, B.H.
Partner: UNT Libraries Government Documents Department

Welding of dissimilar alloys for high temperature heat exchangers for SOFC

Description: Reduction in the cost of balance of plant applications is one of the top priority focus areas for the successful implementation of solid oxide fuel cell technology. High temperature heat exchangers are employed to heat cathode air utilizing either hot gases coming from the anode side of the stack or other hot gases generated by external processes. In order to reduce the cost of heat exchangers, it may be necessary to apply several different materials, each in a different temperature zone, for the construction of the heat exchanger. This technique would require the joining of dissimilar materials in the construction. In this work, welding of commercial candidate dissimilar materials is explored. Filler materials were identified using equilibrium phase diagrams and thermodynamic simulation software. Autogenous welding was performed and the welding defects were characterized. Finally, experimental weld microstructures were compared to phases predicted by the simulations.
Date: October 1, 2006
Creator: Wilson, R.D.; Hatem, J.; Dogan, O.N. & King, P.E.
Partner: UNT Libraries Government Documents Department

High temperature corrosion of Cr-W alloys in simulated syngas

Description: Search for new high temperature materials for energy applications continues. This presentation will focus on degradation of Cr alloys containing 0-30%W by weight in a flowing gas mixture containing 30%CO, 8%CO2, 20%H2, 2%CH4, 0.8%H2S, 0.02%HCl, and 40%N2 by volume at temperatures up to 1000ºC. A pseudo-cyclic test involving heating the specimens, holding them at temperature for varying periods, and cooling them to room temperature was employed. Mass change of the specimens was determined after each cycle. Corrosion scale on the specimens was characterized using SEM, WDX, and XRD. Various sulfides, oxides, carbides, and nitrides were determined in different layers of the scale.
Date: February 1, 2007
Creator: Dogan, O.N.; Bullard, S.J. & Covino, B.S., Jr.
Partner: UNT Libraries Government Documents Department

Integrated Design and Rapid Development of Refractory Metal Based Alloys for Fossil Energy Applications

Description: One common barrier in the development of new technologies for future energy generating systems is insufficiency of existing materials at high temperatures (>1150oC) and aggressive atmospheres (e.g., steam, oxygen, CO2). To overcome this barrier, integrated design methodology will be applied to the development of refractory metal based alloys. The integrated design utilizes the multi-scale computational methods to design materials for requirements of processing and performance. This report summarizes the integrated design approach to the alloy development and project accomplishments in FY 2008.
Date: July 1, 2008
Creator: Dogan, O.N.; King, P.E. & Gao, M.C.
Partner: UNT Libraries Government Documents Department

An update on field test results for an engineered refractory for slagging gasifiers

Description: The widespread commercial adaptation of slagging gasifier technology to produce power, fuel, and/or chemicals from coal will depend in large measure on the technology’s ability to prove itself both economic and reliable. Improvements in gasifier reliability, availability, and maintainability will in part depend on the development of improved performance structural materials with longer service life in this application. Current generation refractory materials used to line the air-cooled, slagging gasifier vessel, and contain the gasification reaction, often last no more than three to 18 months in commercial applications. The downtime required for tear-out and replacement of these critical materials contributes to gasifier on-line availabilities that fall short of targeted goals. In this talk we will discuss the development of an improved refractory material engineered by the NETL for longer service life in this application, and provide an update on recent field test results.
Date: May 1, 2006
Creator: Dogan, O.N.; Alman, D.E.; Jablonski, P.D. & Hawk, J.A.
Partner: UNT Libraries Government Documents Department

Microstructural Stability and Oxidation Resistance of 9-12 Chromium Steels at Elevated Temperatures

Description: Various martensitic 9-12 Cr steels are utilized currently in fossil fuel powered energy plants for their good elevated temperature properties such as creep strength, steam side oxidation resistance, fire side corrosion resistance, and thermal fatigue resistance. Need for further improvements on the properties of 9-12 Cr steels for higher temperature (>600oC) use is driven by the environmental concerns (i.e., improve efficiency to reduce emissions and fossil fuel consumption). In this paper, we will discuss the results of the research done to explore new subsitutional solute solution and precipitate hardening mechanisms for improved strength of 9-12 Cr martensitic steels. Stability of the phases present in the steels will be evaluated for various temperature and time exposures. A comparison of microstructural properties of the experimental steels and commercial steels will also be presented. <br><br> The influence of a Ce surface treatment on oxidation behavior of a commercial (P91) and several experimental steels containing 9 to 12 weight percent Cr was examined at 650ºC in flowing dry and moist air. The oxidation behavior of all the alloys without the Ce modification was significantly degraded by the presence of moisture in the air during testing. For instance the weight gain for P91 was two orders of magnitude greater in moist air than in dry air. This was accompanied by a change in oxide scale from the formation of Cr-based scales in dry air to the formation of Fe-based scales in moist air. The Ce surface treatment was very effective in improving the oxidation resistance of the experimental steels in both moist and dry air. For instance, after exposure to moist air at 650ºC for 2000 hours, an experimental alloy with the cerium surface modification had a weight gain three orders of magnitude lower than the alloy without the Ce modification and two orders of ...
Date: May 1, 2006
Creator: Dogan, O.N.; Alman, D.E.; Jablonski, P.D. & Hawk, J.A.
Partner: UNT Libraries Government Documents Department

Steam turbine materials and corrosion

Description: Ultra-supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include power generation from coal at 60% efficiency, which would require steam temperatures of up to 760°C. This project examines the steamside oxidation of candidate alloys for use in USC systems, with emphasis placed on applications in high- and intermediate-pressure turbines. As part of this research a concern has arisen about the possibility of high chromia evaporation rates of protective scales in the turbine. A model to calculate chromia evaporation rates is presented.
Date: December 1, 2007
Creator: Holcomb, G.R.; Alman, D.E.; Dogan, O.N.; Rawers, J.C.; Schrems, K.K. & Ziomek-Moroz, M.
Partner: UNT Libraries Government Documents Department