Selective oxidation and nickel enrichment hinders the repassivation kinetics of multi-principal element alloy surfaces

Jia Chen; Zhengyu Zhang; Eitan Hershkovitz; Jonathan Poplawsky; Raja Shekar Bhupal Dandu; Chang Yu Hung; Wenbo Wang; Yi Yao; Lin Li; Hongliang Xin; Honggyu Kim; Wenjun Cai

doi:10.1016/j.actamat.2023.119490

Selective oxidation and nickel enrichment hinders the repassivation kinetics of multi-principal element alloy surfaces

Jia Chen, Zhengyu Zhang, Eitan Hershkovitz, Jonathan Poplawsky, Raja Shekar Bhupal Dandu, Chang Yu Hung, Wenbo Wang, Yi Yao, Lin Li, Hongliang Xin, Honggyu Kim, Wenjun Cai

Materials MicroAnalysis

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

Robust and sustained corrosion resistance in multi-principal element alloys (MPEA) requires rapid repassivation, i.e. regrowth of the passive layer once it is damaged or destroyed at the surface. In this study, we show that the repassivation of Al_0.1CrCoFeNi MPEA in 0.6 M NaCl solution is hindered at pH of ∼ 2.4 - 6.8 due to the formation of a Ni-enriched subsurface layer as a result of selective oxidation and dissolution of several principal elements, which can be fully restored at pH of ∼ 14 from the oxidation of all principal elements. Specifically, surface characterization via X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM), and atom probe tomography (APT), are coupled with density functional theory (DFT) calculations to determine surface composition, oxidation state, and electron work function to uncover the structural origin of the pH-dependent repassivation mechanisms. It was found that selective oxidation of Cr, Co, and Fe in the acidic to neutral solutions altered the surface composition to be significantly enriched in Ni as compared to the bulk. Once the original passive film is destroyed locally by either pitting or tribocorrosion, this altered surface composition exhibited a much poorer repassivation capability due to the increased electron work function and reduced surface reactivity at higher Ni concentration. These understandings could shed light on the future compositional design of non-equiatomic MPEAs towards sustained repassivation and corrosion resistance over a wide pH range.

Original language	English
Article number	119490
Journal	Acta Materialia
Volume	263
DOIs	https://doi.org/10.1016/j.actamat.2023.119490
State	Published - Jan 15 2024

Funding

This research was financially supported by the US National Science Foundation (Grant No. DMR-2104655/2104656 ). APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank James Burns for assistance in performing APT sample preparation and running the APT experiments. This work was performed in part at the Nanoscale Characterization and Fabrication Laboratory, which is supported by the Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure (NanoEarth), a member of the National Nanotechnology Coordinated Infrastructure (NNCI), supported by NSF ( ECCS 1542100 and ECCS 2025151 ). J.C. and W.C. gratefully acknowledge the discussion of XPS analysis and results with Dr. Weinan Leng of the Nanoscale Characterization and Fabrication Laboratory at Virginia Tech.

Funders	Funder number
Center for Nanophase Materials Sciences
Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure
National Science Foundation	ECCS 1542100, ECCS 2025151, DMR-2104655/2104656
U.S. Department of Energy
Office of Science
Oak Ridge National Laboratory

Keywords

Corrosion
High entropy alloys
Multi-principal element alloys
Repassivation
Tribocorrosion

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10.1016/j.actamat.2023.119490

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title = "Selective oxidation and nickel enrichment hinders the repassivation kinetics of multi-principal element alloy surfaces",

abstract = "Robust and sustained corrosion resistance in multi-principal element alloys (MPEA) requires rapid repassivation, i.e. regrowth of the passive layer once it is damaged or destroyed at the surface. In this study, we show that the repassivation of Al0.1CrCoFeNi MPEA in 0.6 M NaCl solution is hindered at pH of ∼ 2.4 - 6.8 due to the formation of a Ni-enriched subsurface layer as a result of selective oxidation and dissolution of several principal elements, which can be fully restored at pH of ∼ 14 from the oxidation of all principal elements. Specifically, surface characterization via X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM), and atom probe tomography (APT), are coupled with density functional theory (DFT) calculations to determine surface composition, oxidation state, and electron work function to uncover the structural origin of the pH-dependent repassivation mechanisms. It was found that selective oxidation of Cr, Co, and Fe in the acidic to neutral solutions altered the surface composition to be significantly enriched in Ni as compared to the bulk. Once the original passive film is destroyed locally by either pitting or tribocorrosion, this altered surface composition exhibited a much poorer repassivation capability due to the increased electron work function and reduced surface reactivity at higher Ni concentration. These understandings could shed light on the future compositional design of non-equiatomic MPEAs towards sustained repassivation and corrosion resistance over a wide pH range.",

keywords = "Corrosion, High entropy alloys, Multi-principal element alloys, Repassivation, Tribocorrosion",

author = "Jia Chen and Zhengyu Zhang and Eitan Hershkovitz and Jonathan Poplawsky and Dandu, {Raja Shekar Bhupal} and Hung, {Chang Yu} and Wenbo Wang and Yi Yao and Lin Li and Hongliang Xin and Honggyu Kim and Wenjun Cai",

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AU - Chen, Jia

AU - Zhang, Zhengyu

AU - Hershkovitz, Eitan

AU - Poplawsky, Jonathan

AU - Dandu, Raja Shekar Bhupal

AU - Hung, Chang Yu

AU - Wang, Wenbo

AU - Yao, Yi

AU - Li, Lin

AU - Xin, Hongliang

AU - Kim, Honggyu

AU - Cai, Wenjun

PY - 2024/1/15

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AB - Robust and sustained corrosion resistance in multi-principal element alloys (MPEA) requires rapid repassivation, i.e. regrowth of the passive layer once it is damaged or destroyed at the surface. In this study, we show that the repassivation of Al0.1CrCoFeNi MPEA in 0.6 M NaCl solution is hindered at pH of ∼ 2.4 - 6.8 due to the formation of a Ni-enriched subsurface layer as a result of selective oxidation and dissolution of several principal elements, which can be fully restored at pH of ∼ 14 from the oxidation of all principal elements. Specifically, surface characterization via X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM), and atom probe tomography (APT), are coupled with density functional theory (DFT) calculations to determine surface composition, oxidation state, and electron work function to uncover the structural origin of the pH-dependent repassivation mechanisms. It was found that selective oxidation of Cr, Co, and Fe in the acidic to neutral solutions altered the surface composition to be significantly enriched in Ni as compared to the bulk. Once the original passive film is destroyed locally by either pitting or tribocorrosion, this altered surface composition exhibited a much poorer repassivation capability due to the increased electron work function and reduced surface reactivity at higher Ni concentration. These understandings could shed light on the future compositional design of non-equiatomic MPEAs towards sustained repassivation and corrosion resistance over a wide pH range.

KW - Corrosion

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KW - Multi-principal element alloys

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KW - Tribocorrosion

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JO - Acta Materialia

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ER -

Selective oxidation and nickel enrichment hinders the repassivation kinetics of multi-principal element alloy surfaces

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