Ferritic Stainless Steel Interconnects Research Articles

(Mn,Co) 3O 4 spinel coatings on ferritic stainless steels for SOFC interconnect applications

(Mn,Co) 3O 4 spinel with a nominal composition of Mn 1.5Co 1.5O 4 demonstrates excellent electrical conductivity, satisfactory thermal and structural stability, as well as good thermal expansion match to ferritic stainless steel interconnects. A slurry-coating technique was developed for fabricating the spinel coatings onto the steel interconnects. Thermally grown layers of Mn 1.5Co 1.5O 4 not only significantly decreased the contact resistance between a LSF cathode and stainless steel interconnect, but also acted as a mass barrier to inhibit scale growth on the stainless steel and to prevent Cr outward migration through the coating. The level of improvement in electrical performance and oxidation resistance (i.e. the scale growth rate) was dependent on the ferritic substrate composition. For E-brite and Crofer22 APU, with a relatively high Cr concentration (27 wt% and 23%, respectively) and negligible Si, the reduction of contact ASR and scale growth on the ferritic substrates was significant. In comparison, limited improvement was achieved by application of the Mn 1.5Co 1.5O 4 spinel coating on AISI430, which contains only 17%Cr and a higher amount of residual Si.

Thermal Growth and Performance of Manganese Cobaltite Spinel Protection Layers on Ferritic Stainless Steel SOFC Interconnects

To protect solid oxide fuel cells (SOFCs) from chromium poisoning and improve metallic interconnect stability, manganese cobaltite spinel protection layers with a nominal composition of were thermally grown on Crofer22 APU, a ferritic stainless steel. Thermal, electrical, and electrochemical investigations indicated that the spinel protection layers not only significantly decreased the contact area specific resistance (ASR) between a LSF cathode and the stainless steel interconnect, but also inhibited the subscale growth on the stainless steel by acting as a barrier to the inward diffusion of oxygen. A long-term thermal cycling test demonstrated excellent structural and thermomechanical stability of these spinel protection layers, which also acted as a barrier to outward chromium cation diffusion to the interconnect surface. The reduction in the contact ASR and prevention of Cr migration achieved by application of the spinel protection layers on the cathode side of ferritic stainless steel interconnects resulted in improved stability and electrochemical performance of SOFCs.

Chemical Compatibility of Barium-Calcium-Aluminosilicate-Based Sealing Glasses with the Ferritic Stainless Steel Interconnect in SOFCs

In most planar solid oxide fuel cell (SOFC) stack designs, the interconnect, which is typically made from a ferritic stainless steel (SS), is hermetically sealed to the ceramic positive electrode-electrolyte-negative electrode by a sealing glass. To maintain the structural stability and minimize degradation of the stack performance, the sealing glass must be chemically compatible with the SS interconnect. In this study, a barium-calcium-aluminosilicate (BCAS)-based glass ceramic, specifically developed as a sealant in SOFC stacks, and a ferritic SS (AISI446) were selected as examples to increase the understanding of the chemical compatibility issues in SOFCs. Evaluation of the interfaces of coupon joints indicated that interactions between the BCAS glass ceramic and the ferritic SS were dependent on the exposure conditions. At the edges of joints, where oxygen or air was accessible, the interaction often led to the formation of while in the interior of the joints, chromium or chromia dissolved into the glass to form a thin layer of chromium-rich solid solution. It was also found that, in the interior of the joints, the interaction often resulted in the formation of pores aligned along the interface. It appears the pore formation along the interface can be avoided through a preheat treatment. © 2003 The Electrochemical Society. All rights reserved.

The influence of sulphur on the adhesion and growth mechanisms of chromia and alumina scales formed at high temperatures: the ‘sulphur effect’

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Lees D. G. 2003The influence of sulphur on the adhesion and growth mechanisms of chromia and alumina scales formed at high temperatures: the ‘sulphur effect’Proc. R. Soc. Lond. A.4591459–1466http://doi.org/10.1098/rspa.2002.1107SectionRestricted accessThe influence of sulphur on the adhesion and growth mechanisms of chromia and alumina scales formed at high temperatures: the ‘sulphur effect’ D. G. Lees D. G. Lees Manchester Materials Science Centre, University of Manchester and UMIST, Street, Manchester M1 7HS, UK Google Scholar Find this author on PubMed Search for more papers by this author D. G. Lees D. G. Lees Manchester Materials Science Centre, University of Manchester and UMIST, Street, Manchester M1 7HS, UK Google Scholar Find this author on PubMed Search for more papers by this author Published:08 June 2003https://doi.org/10.1098/rspa.2002.1107AbstractThe term ‘the sulphur effect’ as originally proposed consisted of two parts. Part 1 proposed that impurity sulphur segregates to the interface between chromia and alumina scales and the metal, that it has a deleterious effect on the adhesion and that reactive elements prevent this segregation. More recent evidence shows that the same effect can be obtained by other means, without the addition of reactive elements. Part 2 of the hypothesis relates to the effect of sulphur on the growth mechanism of these scales. It proposed that the oxide grain boundaries can transport cations or oxygen ions depending on whether sulphur is present or not. Sulphur has been shown to segregate to chromia grain boundaries, with the exception of low–angle grain boundaries. Therefore, according to the hypothesis, a scale which contains some grain boundaries that are low–angle and some that are not will grow by a mixture of oxygen and cation grain–boundary transport. A review of the experimental results shows that they can be accounted for on the basis of this hypothesis. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by Ma Z, Wang M, Zhang Y, Li K, Zhang M and Yang W (2022) Cu and Y doped (Co, Mn)3O4 spinel coatings on Crofer ferritic alloy by composite electrodeposition, Vacuum, 10.1016/j.vacuum.2022.111352, 204, (111352), Online publication date: 1-Oct-2022. Smialek J (2022) Invited Review Paper in Commemoration of Over 50 Years of Oxidation of Metals: Alumina Scale Adhesion Mechanisms: A Retrospective Assessment, Oxidation of Metals, 10.1007/s11085-021-10091-2, 97:1-2, (1-50), Online publication date: 1-Feb-2022. Wright I (2020) Cyclic oxidation behaviour of TP446, TP310, and IN617 in air at 871°C and 982°C, Materials at High Temperatures, 10.1080/09603409.2020.1811599, 37:6, (398-415), Online publication date: 1-Nov-2020. Al-Meshari A, Al-Rabie M and Al-Dajane M (2013) Failure Analysis of Furnace Tube, Journal of Failure Analysis and Prevention, 10.1007/s11668-013-9676-3, 13:3, (282-291), Online publication date: 1-Jun-2013. Shaigan N, Qu W, Ivey D and Chen W (2010) A review of recent progress in coatings, surface modifications and alloy developments for solid oxide fuel cell ferritic stainless steel interconnects, Journal of Power Sources, 10.1016/j.jpowsour.2009.09.069, 195:6, (1529-1542), Online publication date: 1-Mar-2010. Zhao X and Xiao P (2008) Effect of platinum on the durability of thermal barrier systems with a γ+γ′ bond coat, Thin Solid Films, 10.1016/j.tsf.2008.08.006, 517:2, (828-834), Online publication date: 1-Nov-2008. Hou P, Paulikas A, Veal B and Smialek J (2007) Thermally grown Al2O3 on a H2-annealed Fe3Al alloy: Stress evolution and film adhesion, Acta Materialia, 10.1016/j.actamat.2007.06.018, 55:16, (5601-5613), Online publication date: 1-Sep-2007. This Issue08 June 2003Volume 459Issue 2034 Article InformationDOI:https://doi.org/10.1098/rspa.2002.1107Published by:Royal SocietyPrint ISSN:1364-5021Online ISSN:1471-2946History: Published online08/06/2003Published in print08/06/2003 License: Citations and impact KeywordsSulphur EffectChromiaAluminaAdhesionGrowth MechanismReactive–Element Effect