Visualizing time-dependent microstructural and chemical evolution during molten salt corrosion of Ni-20Cr model alloy using correlative quasi in situ TEM and in situ synchrotron X-ray nano-tomography

Bawane, Kaustubh; Liu, Xiaoyang; Gakhar, Ruchi; Woods, Michael E.; Ge, Mingyuan; Xiao, Xianghui; Lee, Ivan; Halstenberg, Philip; Dai, Sheng; Mahurin, Shannon M.; Pimblott, Simon M.; Wishart, James F.; Chen‐Wiegart, Yu‐chen Karen; He, Lingfeng

doi:10.1016/j.corsci.2021.109962

Cited by 25 publications

(26 citation statements)

References 54 publications

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“…Therefore, we propose an alternative explanation that small Nirich grains were liberated from the foil due to the dissolution of Cr. Previous X-ray tomography and quasi in situ TEM observations of NiCr wires in molten KCl -MgCl 2 showed dealloying, grain boundary attacks, and salt penetration in cracks and pores [26][27][28]. Such dealloying leaves behind a sponge-like structure of Ni-rich grains that would easily detach into the solution.…”

Section: Discussionmentioning

confidence: 95%

In-situ analysis of corrosion products in molten salt: concurrent X-ray absorption and electrochemistry reveal both ionic and metallic species

Fayfar

Zheng

Sprouster

et al. 2022

Preprint

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Understanding and controlling the physical and chemical processes at molten salt‐alloy interfaces is vital for molten‐salt nuclear reactors. Corrosion processes in molten salts are highly dependent on the redox potential of the solution that changes with the addition of fission and corrosion products. Therefore, reactor designers develop online electrochemical methods of salt monitoring. But electrochemical spectroscopy relies on the deconvolution of broad peaks, a process that may be imprecise in the presence of multiple species in the solution. Here, we describe our developments towards monitoring the concentration and the chemical state of corrosion products in the melt by a combination of electrochemistry and X-ray absorption spectroscopy. We placed NiCr foil in molten FLiNaK and found the presence of both Ni2+ ions and metallic Ni in the melt, which we attribute to the disintegration of the corroding foil due to Cr dealloying. Although extremely challenging, spectroelectrochemical measurements add a promising rich new data stream for online salt monitoring.

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Section: Discussionmentioning

confidence: 95%

In-situ analysis of corrosion products in molten salt: concurrent X-ray absorption and electrochemistry reveal both ionic and metallic species

Fayfar

Zheng

Sprouster

et al. 2022

Preprint

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“…Bawane directly observed the morphological evolution in real time during the molten salt corrosion of the Ni-20Cr model alloy by using quasi-in situ TEM and in situ X-ray nanotomography. [12] However, it is still a great challenge to reveal the microscopic mechanisms of corrosion process of alloys, e.g., quantitative characterization of the diffusion of ions and the evolution of ion concentration. This gets worse when it comes to the corrosion process of aluminum alloys involving up to 6 electrochemical reactions and concentration evolution of 8 ions.…”

Section: Introductionmentioning

confidence: 99%

“…It is still a great challenge to quantify the influence of an individual factor, such as temperature, the concentration of salt and pH value, on the kinetics of corrosion process. [12,14,15] Numerical simulation is an effective approach to solve this problem in terms of the limitations of experimental study. [11,16] The phase field method is a powerful tool to study the morphological evolution of corroded surfaces, and the diffusion kinetics of ions in electrolyte.…”

Section: Introductionmentioning

confidence: 99%

A New Multi‐Phase Field Model for the Electrochemical Corrosion of Aluminum Alloys

Chen

Tang

et al. 2022

Advcd Theory and Sims

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A profound understanding on the corrosion kinetics and mechanisms is crucial to help improve the corrosion resistance of alloys. Corrosion of aluminum alloys is very complex due to the interplay among a bunch of electrochemical reactions, and the influences of diversified precipitates. In this work, a new multi-phase field method is constructed to quantitatively analyze the corrosion kinetics of aluminum alloys, and a semi-implicit algorithm is developed to solve the numerical divergence resulted by the terms of reactions in concentration equations. Then, this new method is successfully used to simulate the pitting processes in the cases of a uniform matrix, a polycrystalline matrix, and a non-uniform matrix with secondary phase for aluminum alloys. More generally, the framework of this multi-phase field model can potentially be used to study the corrosion of other alloy systems, and microstructure evolution of a broad range of electrochemistry processes.

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“…Elucidating molten salt corrosion susceptibility requires delving further into the corrosion mechanism of MCFR structural materials, expanding on the relationship between alloy composition and microstructure on the kinetics and thermodynamics of the corrosion process. To assess changes in alloy composition and microstructure at a length scale indicative for elucidating the corrosion mechanism, a suite of advanced characterization techniques is needed (Indacochea et al, 2001;Shankar et al, 2013;Salinas-Solano et al, 2014;Vignarooban et al, 2014;Gomez-Vidal and Tirawat, 2016;Liu et al, 2017;Wang et al, 2017;Sun et al, 2018a;Ding et al, 2018;Ding et al, 2019;Jalbuena et al, 2019;Yu et al, 2019;Grégoire et al, 2020;JagadeeswaraRao and Ningshen, 2020;Knosalla et al, 2020;Yang et al, 2020;Bawane et al, 2021;Caldwell et al, 2021;Gill et al, 2021;Patel et al, 2021;Pragnya et al, 2021). More importantly, these characterization techniques need to be employed in a corroborative manner through a multi-modal approach to develop a comprehensive assessment of the corrosion mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…Electrochemical studies and XAS enabled characterizing changes in the molten salt during the corrosion process, with XAS providing an opportunity for in situ analysis as the corrosion process is observed in real-time. Bawane et al combined a quasi in situ TEM analysis with synchrotron nano-tomography to assess chemical and microstructural changes at the onset (<60 s) towards maturity (>2 h) of the corrosion propagation in Ni-20Cr model alloys in KCl-MgCl 2 (Bawane et al, 2021). Quasi in situ TEM provided a novel perspective for capturing time-sensitive changes at a length scale appropriate for assessing kinetic details of chemical evolution and initial crack propagation; However, given the small sampling volume it is not appropriate for a representative assessment of microstructural changes.…”

Section: Introductionmentioning

confidence: 99%

Assessing the interfacial corrosion mechanism of Inconel 617 in chloride molten salt corrosion using multi-modal advanced characterization techniques

Copeland-Johnson¹,

Murray²,

Cao³

et al. 2022

Front. Nucl. Eng.

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The United States Department of Energy (DOE) has committed to expanding the domestic clean energy portfolio in response to the rising challenges of energy security in the wake of climate change. Accordingly, the construction of a series of Generation IV reactor technologies are being demonstrated, including sodium-cooled, small modular, and molten chloride fast reactors (MCFRs). To date, there are no fully qualified structural materials for constructing MCFRs. A number of commercial structural alloys have been considered for the construction of MCFRs, including alloys from the Inconel and Hastelloy series. Informed qualification of structural materials for the construction of MCFRs in the future can only be ensured by expanding the current fundamental knowledgebase of information pertaining to material performance under environmental stressors relevant to operation of the reactor, including corrosion susceptibility. The purpose of this investigation is to illustrate how a correlative multi-modal electron microscopy characterization approach, including the novel application of focused-ion beam 3D reconstruction capabilities, can elucidate the corrosion mechanism of a candidate structural material Inconel 617 for MCFR in NaCl-MgCl2 eutectic salt at 700°C for 1,000 h. Evidence of intergranular corrosion, Ni and Fe dealloying, and Cr-O enrichment along the grain boundary, which most likely corresponds to Cr2O3, is a phenomenon that has been documented in other Ni-based superalloys exposed to chloride molten salt systems. Additional corrosion products, including the formation of insoluble MgAl2O4, within the porous network produced by the salt attack is a novel observation. In addition, Mo3Si5 and τ2 precipitates are detected in the alloy bulk and are dissolved by the salt. Furthermore, the lack of detection of design γ′ precipitates in Inconel 617 after 1,000 h could indicate that the molten salt corrosion mechanism has indirectly induced a phase transformation of Al2TiNi (τ2) and Ni3(Al,Ti) (γ’) phase. This investigation provides a comprehensive understanding of molten salt corrosion mechanisms in a complex material system such as a commercial structural alloy for applications in MCFRs.

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Visualizing time-dependent microstructural and chemical evolution during molten salt corrosion of Ni-20Cr model alloy using correlative quasi in situ TEM and in situ synchrotron X-ray nano-tomography

Cited by 25 publications

References 54 publications

In-situ analysis of corrosion products in molten salt: concurrent X-ray absorption and electrochemistry reveal both ionic and metallic species

In-situ analysis of corrosion products in molten salt: concurrent X-ray absorption and electrochemistry reveal both ionic and metallic species

A New Multi‐Phase Field Model for the Electrochemical Corrosion of Aluminum Alloys

Assessing the interfacial corrosion mechanism of Inconel 617 in chloride molten salt corrosion using multi-modal advanced characterization techniques

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