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Electrochemical Behavior of Bilayer Thermal-Spray Coatings in Low-Temperature Corrosion Protection
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-7663-9631
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-9578-4076
2017 (English)In: Coatings, ISSN 2079-6412, Vol. 7, no 10, article id 162Article in journal (Refereed) Published
Abstract [en]

Cr3C2-NiCr coatings are greatly used to protect critical components in corrosive environments and to extend their lifetime and/or improve functional performance. However, the pores formed during spraying restrict the coating’s applicability area for many corrosion protection applications. To overcome this technical challenge, bilayer coatings have been developed, in which an additional layer (the so-called intermediate layer) is deposited on the substrate before spraying the Cr3C2-NiCr coating (the so-called top layer). The corrosion behavior of the bilayer coating depends on the composition and microstructure of each layer. In the present work, different single-layer coatings (i.e., Cr3C2-NiCr, Fe- and Ni-based coatings) were initially sprayed by a high-velocity air fuel (HVAF) process. Microstructure analysis, as well as electrochemical tests, for example, open-circuit potential (OCP) and polarization tests, were performed. The potential difference (Delta E) had a great influence on galvanic corrosion between the top and intermediate layers, and thus, the coatings were ranked based on the OCP values (from high to low) as follows: NiCoCrAlY > NiCr > Cr3C2-NiCr > NiAl > Fe-based coatings (alloyed with Cr) > pure Ni. The Ni-based coatings were chosen to be further used as intermediate layers with the Cr3C2-NiCr top layer due to their capabilities to show high OCP. The corrosion resistance (R-p) of the bilayer coatings was ranked (from high to low) as follows: NiCoCrAlY/Cr3C2-NiCr > NiCr/Cr3C2-NiCr > NiAl/Cr3C2-NiCr > Ni/Cr3C2-NiCr. It was shown that splat boundaries and interconnected pores are detrimental for corrosion resistance, however, a sufficient reservoir of protective scale-forming elements (such as Cr or/and Al) in the intermediate layer can significantly improve the corrosion resistance.

Place, publisher, year, edition, pages
MDPI AG , 2017. Vol. 7, no 10, article id 162
Keyword [en]
thermal-spray coating; Cr3C2-NiCr; corrosion protection; bilayer coating; high-velocity air fuel (HVAF)
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-11883DOI: 10.3390/coatings7100162ISI: 000414849800011OAI: oai:DiVA.org:hv-11883DiVA, id: diva2:1162969
Funder
Region Västra Götaland, RUN 2016-01489
Note

Projekt PROSAM

Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2017-12-29Bibliographically approved

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Sadeghimeresht, EsmaeilMarkocsan, Nicolaie

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