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A comparative study on Ni-based coatings prepared by HVAF, HVOF, and APS methods for corrosion protection applications
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
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0001-7787-5444
2016 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 8, 1604-1616 p.Article in journal (Refereed) Published
Abstract [en]

Selection of the thermal spray process is the most important step towards a proper coating solution for a given application as important coating characteristics such as adhesion, and microstructure, etc. are highly dependent on it. In the present work, a process-microstructure-properties-performance correlation study was performed in order to figure out the main characteristics and corrosion performance of the coatings produced by different thermal spray techniques such as high-velocity airfuel (HVAF), high-velocity oxy fuel (HVOF), and atmospheric plasma spraying (APS). Previously optimized HVOF and APS process parameters were used to deposit Ni, NiCr, and NiAl coatings and compare with HVAF-sprayed coatings with randomly selected process parameters. As the HVAF process presented the best coating characteristics and corrosion behavior, various process parameters,e.g., feed rate and stand off distance (SoD) were investigated to systematically optimize the HVAF coatings in terms of high density and corrosion properties. The coatings with lower porosity and better corrosion behavior were obtained at an average SoD of 300 mm for the Ni and NiAl coatings and a SoDof 250 mm for the NiCr coating. Increasing the feed rate to 150 g/min in the Ni and NiAl coatings decreased the coating pores and accordingly increased the Rp.

Place, publisher, year, edition, pages
Materials Park, OH: ASM International, 2016. Vol. 25, no 8, 1604-1616 p.
Keyword [en]
Thermal Spraying, Process optimization, Corrosion, OCP, Potentiodynamic polarization
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-9926DOI: 10.1007/s11666-016-0474-9ISI: 000390041000016ScopusID: 2-s2.0-84994756460OAI: oai:DiVA.org:hv-9926DiVA: diva2:972689
Note

Ingår i lic avhandling

Available from: 2016-09-22 Created: 2016-09-22 Last updated: 2017-04-20Bibliographically approved
In thesis
1. Corrosion Behavior of HVAF-Sprayed Bi-Layer Coatings
Open this publication in new window or tab >>Corrosion Behavior of HVAF-Sprayed Bi-Layer Coatings
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In a variety of engineering applications, components are subjected to corrosive environment. Protective coatings are essential to improve the functional performances and/or extend the lifetime of the components. Thermal sprayingas a cost-effective coating deposition technique offers high flexibility in coatings' chemistry/morphology/microstructure design. However, the inherent pores formed during spraying limit the use of coatings for corrosion protection. The recently developed supersonic spray method, High-Velocity-Air-Fuel (HVAF), brings significant advantages in terms of cost and coating properties. Although severely reduced, the pores are not completely eliminated even with the HVAF process. In view of the above gap to have a high quality coating, bi-layer coatings have been developed to improve the corrosion resistance of the coatings. In a bi-layer coating, an intermediate layer is deposited on the substrate before spraying the coating. The electrochemical behavior of each layer is important to ensure a good corrosion protection. The corrosion behavior of the layers strongly depends on coating composition and microstructure, which are affected by feedstock material and spraying process. Therefore, the objective of the researchis to explore the relationships between feedstock material, spraying process, microstructure and corrosion behavior of bi-layer coatings. A specific motivationis to understand the corrosion mechanisms of the intermediate layer which forms the basis for developing superior protective coatings. Cr3C2-NiCr top layer and intermediate layers (Fe-, Co- and Ni-based) were sprayed by different thermal spraying processes. Microstructure analysis, as well as various corrosion tests, e.g., electrochemical, salt spray and immersion tests were performed. The results showed a direct link between the corrosion potential (Ecorr) of the intermediate layer and the corrosion mechanisms. It was found that the higher corrosion resistance of Ni-based coatings than Fe- and Co-based coatings was due to higher Ecorr of the coating in the galvanic couple with top layers. Inter-lamellar boundaries and interconnected pores reduced the corrosion resistance of intermediate layers, however a sufficient reservoir of protective scale-forming elements (such as Cr or Al) improved the corrosion behavior.

Place, publisher, year, edition, pages
Trollhättan: University West, 2016. 59 p.
Series
Licentiate Thesis: University West, 10
Keyword
Thermal spray coating, HVAF, Corrosion protection, Galvanic corrosion, Composition, Microstructure, EIS, Polarization, OCP
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9929 (URN)978-91-87531-33-0 (ISBN)978-91-87531-32-3 (ISBN)
Presentation
2016-09-30, C118, University West, Trollhättan, 10:15 (English)
Supervisors
Available from: 2016-09-30 Created: 2016-09-22 Last updated: 2016-09-30Bibliographically approved

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