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Title: Studies of Scale Formation and Kinetics of Crofer 22 APU and Haynes 230 in Carbon Oxide-Containing Environment for SOFC Applications

Abstract

Significant progress in reducing the operating temperature of SOFCs below 800oC may allow the use of chromia-forming metallic interconnects at a substantial cost savings. Hydrogen is the main fuel for all types of fuel cells except direct methanol fuel cells. Hydrogen can be generated from fossil fuels, including coal, natural gas, diesel, gasoline, other hydrocarbons, and oxygenates (e.g., methanol, ethanol, butanol, etc.). Carbon oxides present in the hydrogen fuel can cause significant performance problems due to carbon formation (coking). Also, literature data indicate that in CO/CO2 gaseous environments, metallic materials that gain their corrosion resistance due to formation of Cr2O3, could form stable chromium carbides. The chromium carbide formation causes depletion of chromium in these alloys. If the carbides oxidize, they form non-protective scales. Considering a potential detrimental effect of carbon oxides on iron- and nickel-base alloy stability, determining corrosion performance of metallic interconnect candidates in carbon oxide-containing environments at SOFC operating temperatures is a must. In this research, the corrosion behavior of Crofer 22 APU and Haynes 230 was studied in a CO-rich atmosphere at 750°C. Chemical composition of the gaseous environment at the outlet was determined using gas chromatography (GC). After 800 h of exposure to the gaseousmore » environment the surfaces of the corroded samples were studied by scanning electron microscopy (SEM) equipped with microanalytical capabilities. X-ray diffraction (XRD) analysis was also used in this study.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
National Energy Technology Laboratory (NETL), Pittsburgh, PA, and Morgantown, WV
Sponsoring Org.:
USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
912710
Report Number(s):
DOE/NETL-2007-043
R&D Project: 220693; TRN: US200801%%1158
Resource Type:
Conference
Resource Relation:
Conference: Fuel Cell Seminar, Honolulu, HI, Nov. 13-17, 2006; Related Information: Extended abstract only published
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON; CARBON OXIDES; CHEMICAL COMPOSITION; CHROMIUM CARBIDES; CORROSION RESISTANCE; DIRECT METHANOL FUEL CELLS; FOSSIL FUELS; FUEL CELLS; GAS CHROMATOGRAPHY; HYDROCARBONS; HYDROGEN FUELS; KINETICS; NATURAL GAS; NICKEL BASE ALLOYS; SCANNING ELECTRON MICROSCOPY; SOLID OXIDE FUEL CELLS; X-RAY DIFFRACTION; materials science; engineering; synthetic fuels; energy conservation

Citation Formats

Ziomek-Moroz, M., Covino, B.S., Jr., Holcomb, G.R., Bullard, S.J., and Penner, L.R. Studies of Scale Formation and Kinetics of Crofer 22 APU and Haynes 230 in Carbon Oxide-Containing Environment for SOFC Applications. United States: N. p., 2006. Web.
Ziomek-Moroz, M., Covino, B.S., Jr., Holcomb, G.R., Bullard, S.J., & Penner, L.R. Studies of Scale Formation and Kinetics of Crofer 22 APU and Haynes 230 in Carbon Oxide-Containing Environment for SOFC Applications. United States.
Ziomek-Moroz, M., Covino, B.S., Jr., Holcomb, G.R., Bullard, S.J., and Penner, L.R. Sun . "Studies of Scale Formation and Kinetics of Crofer 22 APU and Haynes 230 in Carbon Oxide-Containing Environment for SOFC Applications". United States. doi:. https://www.osti.gov/servlets/purl/912710.
@article{osti_912710,
title = {Studies of Scale Formation and Kinetics of Crofer 22 APU and Haynes 230 in Carbon Oxide-Containing Environment for SOFC Applications},
author = {Ziomek-Moroz, M. and Covino, B.S., Jr. and Holcomb, G.R. and Bullard, S.J. and Penner, L.R.},
abstractNote = {Significant progress in reducing the operating temperature of SOFCs below 800oC may allow the use of chromia-forming metallic interconnects at a substantial cost savings. Hydrogen is the main fuel for all types of fuel cells except direct methanol fuel cells. Hydrogen can be generated from fossil fuels, including coal, natural gas, diesel, gasoline, other hydrocarbons, and oxygenates (e.g., methanol, ethanol, butanol, etc.). Carbon oxides present in the hydrogen fuel can cause significant performance problems due to carbon formation (coking). Also, literature data indicate that in CO/CO2 gaseous environments, metallic materials that gain their corrosion resistance due to formation of Cr2O3, could form stable chromium carbides. The chromium carbide formation causes depletion of chromium in these alloys. If the carbides oxidize, they form non-protective scales. Considering a potential detrimental effect of carbon oxides on iron- and nickel-base alloy stability, determining corrosion performance of metallic interconnect candidates in carbon oxide-containing environments at SOFC operating temperatures is a must. In this research, the corrosion behavior of Crofer 22 APU and Haynes 230 was studied in a CO-rich atmosphere at 750°C. Chemical composition of the gaseous environment at the outlet was determined using gas chromatography (GC). After 800 h of exposure to the gaseous environment the surfaces of the corroded samples were studied by scanning electron microscopy (SEM) equipped with microanalytical capabilities. X-ray diffraction (XRD) analysis was also used in this study.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

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  • Crofer 22 APU is a 22 weight percent Cr ferritic stainless steel developed at Forschugszentrum Jülich and manufactured by ThysennKrupp for application as an interconnect in SOFC. We have developed a cerium oxide surface treatment which greatly enhances the oxidation resistance of this and many other alloys. Minimizing scale growth is helpful for improving the performance in interconnect application; however, the overall performance is dependant upon such things as scale thickness, scale resistivity, etc. We report on the in-cell performance of cerium treated and conventional Crofer 22 APU and discuss the results in terms of the microstructure and scales thatmore » form.« less
  • Topography and phase composition of the scales formed on commercial ferritic stainless steels were studied in atmospheres simulating solid oxide fuel cell (SOFC) environments. The materials were studied in carbon-containing gases at 750°C. Surface characterization techniques, such as scanning electron microscopy and X-ray diffraction analysis were used in this study.
  • Abstract not provided.
  • The commercial Ni-base Haynes 230 alloy (Ni-Cr-Mo-W-Mn) was modified with two increased levels of Mn (1 and 2 wt per cent) and evaluated for its oxidation resistance under simulated SOFC interconnect exposure conditions. Oxidation rate, oxide morphology, oxide conductivity and thermal expansion were measured and compared with commercial Haynes 230. It was observed that additions of higher levels of Mn to the bulk alloy facilitated the formation of a bi-layered oxide scale that was comprised of an outer M3O4 (M=Mn, Cr, Ni) spinel-rich layer at the oxide – gas interface over a Cr2O3-rich sub-layer at the metal – oxide interface.more » The modified alloys showed higher oxidation rates and the formation of thicker oxide scales compared to the base alloy. The formation of a spinel-rich top layer improved the scale conductivity, especially during the early stages of the oxidation, but the higher scale growth rate resulted in an increase in the area-specific electrical resistance over time. Due to their face-centered cubic crystal structure, both commercial and modified alloys demonstrated a coefficient of thermal expansion that was higher than that of typical anode-supported and electrolyte-supported SOFCs.« less
  • As operating temperature of SOFC decreases, ferritic stainless steel has attracted a great deal of attention for its use as an interconnect in SOFCs because of its gas-tightness, low electrical resistivity, ease of fabrication, and cost-effectiveness. However, oxidation reaction of the metallic interconnects in a typical SOFC working environment is unavoidable. The growth stresses in the oxide scale and on the scale/substrate interface combined with the thermal stresses induced by thermal expansion coefficient mismatch between the oxide scale and the substrate may lead to scale delamination/buckling and eventual spallation during stack cooling, which can lead to serious cell performance degradation.more » Therefore, the interfacial adhesion strength between the oxide scale and substrate is crucial to the reliability and durability of the metallic interconnect in SOFC operating environments. In this paper, we investigated the effect of the surface conditions on the interfacial strength of oxide scale and SS441 substrate experimentally. Contrary to the conventional sense, it was found that rough surface of SS441 substrate will decrease the interfacial adhesive strength of the oxide scale and SS441 substrate« less