ORALS

SESSION: CorrosionTueAM-R7	Macdonald International Symposium (Intl Sympos. on Corrosion for Sustainable Development)
Tue. 29 Nov. 2022 / Room: Andaman 2
Session Chairs: Shujiang Geng; Session Monitor: TBA

11:55: [CorrosionTueAM02] OS
Thermally Conversion (Cu,Fe)3O4 Spinel Coating on Solid Oxide Fuel Cell Interconnect Steel
Shujiang Geng¹ ; Fuhui Wang¹ ; ¹Northeastern University, Shenyang, China;
Paper Id: 206 [Abstract]

Ferritic stainless steels have been widely employed as solid oxide fuel cell (SOFC) interconnects owing to their low cost, coefficient of thermal expansion match with other SOFC components, and good oxidation resistance and acceptable electrical conductivity of Cr2O3. However, they are confronted with several problems during operation in SOFC cathode working condition such as the evaporation of Cr2O3 which results in cathode Cr-poisoning and subsequent degradation of cell performance [1-5]. Therefore, it is necessary to develop electrically conductive coating on them in order to block Cr2O3 evaporation. So far, CuFe2O4 spinel coating is a promising coating to improve the electrical conductivity of the surface oxide scale thermally formed on the steel. In present paper, CuFe alloy layer has been deposited on ferritic stainless steel (SUS 430) by magnetron sputtering method. The coated steels were evaluated in air at 800C corresponding to SOFC cathode environment. It was found that the coated steel initially experienced a large mass gain, followed by slight increase with time. The CuFe alloy layer was mainly converted into CuFe2O4 spinel layer beneath which a Cr-rich layer was grown from the steel substrate upon thermal exposure. The Cr-free outer layer not only suppressed Cr migration outward but also reduced the surface oxide scale area specific resistance (ASR) of the coated steel. <br />Keywords: (CuFe)3O4 coating, Solid oxide fuel cell interconnect, Oxidation, Electrical property

References:
1. H. Falk-Windisch, J. E. Svensson, J. Froitzheim. Effect of temperature on chromium vaporization and oxide scale growth on interconnect steels for Solid Oxide Fuel Cells. Journal of Power Sources.287,25 (2015).\n2. M. Stanislowski, E. Wessel, K. Hilpert, T. Markus, L. Singheiser. Chromium Vaporization from High-Temperature Alloys. Journal of The Electrochemical Society.154,A295 (2007).\n3. S. P. Jiang, X. Chen. Chromium deposition and poisoning of cathodes of solid oxide fuel cells – A review. International Journal of Hydrogen Energy.39,505 (2014).\n4. Z. Xu, W. Xu, E. Stephens, B. Koeppel. Mechanical reliability and life prediction of coated metallic interconnects within solid oxide fuel cells. Renewable Energy.;113,1472 (2017).\n5. W. N. Liu, X. Sun, E. Stephens, M. A. Khaleel. Life prediction of coated and uncoated metallic interconnect for solid oxide fuel cell applications. Journal of Power Sources.189,1044 (2009).

SESSION: CorrosionTuePM1-R7	Macdonald International Symposium (Intl Sympos. on Corrosion for Sustainable Development)
Tue. 29 Nov. 2022 / Room: Andaman 2
Session Chairs: Junhua Dong; Session Monitor: TBA

14:00: [CorrosionTuePM105] OS
Designing High Temperature Protective Bondcoat for Ni-base Single Crystal Superalloys
Zebin Bao¹ ; Shenglong Zhu¹ ; Fuhui Wang² ; ¹Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China; ²Northeastern University, Shenyang, China;
Paper Id: 216 [Abstract]

To meet the sustaining request of enhancing thrust-load ratio, single crystal (SX) superalloy, film cooling and thermal barrier coating system (TBCs) have been perspectively utilized in advanced areo engines. Usually, the coating system consists of an oxidation resistant bondcoat and a heat resistant top coat. During service of SX superalloy components at high temperature, the element interdiffusion between bondcoat and superalloy substrate may instigate serious deterioration of mechanical property (e.g., creep resistance and rupture life) of SX superalloy by forming topologically-close-packed (TCP) phases and second reaction zone (SRZ) [1]. Another impact of such interdiffusion is the loss of beneficial element and undesirable oxidation of refratory elements at surface [2]. Thus, to inhibit or mitigate the interdiffusion is one of the key points to design protective bondcoat for Ni-base SX superalloys [3]. In this study, a Re-base diffusion barrier (DB) has been sucessfully incorporated between the state-of-the-art bondcoat of (Ni,Pt)Al and the Ni-base SX superalloy. In contrast to normal (Ni,Pt)Al coating, the coating with Re-base DB showed better oxidation resistance and less interdiffusion, which further resulted in thinner formation of SRZ and TCP precipitates. Mechanisms responsible for the enhanced performance during the oxidation tests will be intensively discussed.

References:
[1] D.K. Das, K.S. Murphy, S. MA, T.M. Pollock, Formation of secondary reaction zones in diffusion aluminide coated Ni-base single-crystal superalloys containing ruthenium, Metall. Mater. Trans. A 39 (2008) 1647–1657.\n[2] N. D. Souza, D. Welton, G.D West, I.M. Edmonds, On the roles of oxidation and vaporization in surface micro-structural instability during solution heat treatment of Ni-base superalloys, Metall. Mater. Trans. A 45 (2014) 5968–5981.\n[3] C.A. Guo, W. Wang, Y.X. Cheng, S.L. Zhu, F.H. Wang, Yttria partially stabilised zirconia as diffusion barrier between NiCrAlY and Ni-base single crystal René N5 superalloy, Corros. Sci. 94 (2015) 122–128.

SESSION: CorrosionTuePM1-R7	Macdonald International Symposium (Intl Sympos. on Corrosion for Sustainable Development)
Tue. 29 Nov. 2022 / Room: Andaman 2
Session Chairs: Junhua Dong; Session Monitor: TBA

14:25: [CorrosionTuePM106] OS
Galvanic corrosion mechanism of cn Al–BN cbradable ceal coating cystem in chloride colution
Bing Lei¹ ; Guozhe Meng² ; Ying Li³ ; Fuhui Wang⁴ ; ¹School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai, China; ²School of Chemical Engineering and Technology, Sun Yat-sen University, zhuhai, China; ³Institute of Metal Research,Chinese Academy of Sciences, Shenyang, China; ⁴Northeastern University, Shenyang, China;
Paper Id: 220 [Abstract]

In this study[1], we investigated the galvanic corrosion performance of an Aluminum–Boron Nitride (Al–BN) abradable seal coating system (with a Ni5Al bond layer and a 0Cr17Ni4Cu4Nb substrate) in chloride solution by electrochemical methods. Galvanic interaction of the coating system during corrosion has been confirmed, while the Al–BN layer assumes anodic character, while the bond NiAl and substrate act as cathodes. Negative difference effect (NDE)[2] was tested during the anodic dissolution of Al-BN top layer, which indicated that about 13% of the anodic current of the Al–BN layer was compensated by hydrogen evolution by NDE. In addition, a three-stage process occurred during the anodic dissolution of the coupled coating system, consisting of a spontaneous pitting stage I under charge transfer control with a decreasing rate, a corrosion developing stage ІІ under mass transfer control with an increasing rate, and a final steady stage III. Precipitation of Al(OH)3 restricts[3] the oxygen transport process to the cathode and induces localized acidification of the occluded pores of the Al–BN layer, which was the mechanism that could explain the changes of corrosion performance during the three immersion stages of Al–BN coating system. The study suggests that galvanic corrosion of the porous multi-layer Al–BN abradable coating system is mostly influenced by its corrosion product deposition.

References:
[1]Lei, B.; Li, M.; Zhao, Z.; Wang, L.; Li, Y.; Wang, F. Corrosion mechanism of an Al–BN abradable seal coating system in chloride solution. Corros. Sci. 2014, 79, 198–205
[2]Yu, Y.; Li, Y. New insight into the negative difference effect in aluminium corrosion using in-situ electrochemical ICP-OES.Corros. Sci. 2020, 168, 108568
[3] Håkansson, E.; Hoffman, J.; Predecki, P.; Kumosa, M. The role of corrosion product deposition in galvanic corrosion of aluminum/carbon systems. Corros. Sci. 2017, 114, 10–16.