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Ni-based coatings for high temperature corrosion protection
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-7663-9631
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomass/waste-fired boilers severely suffer from high temperature corrosion of critical load-bearing components, e.g. water-wall and superheater tubes, due to presence of Cl-containing corrosive species. Deposition of a dense and adherent Ni-based coating by high velocity air-fuel (HVAF) thermal spray technique is a promising approach to extend the component's lifetime and, hence, increase the thermal/electrical efficiency of the boilers. In this research, high temperature corrosion of candidate Ni-based coatings –Ni21Cr, Ni21Cr7AlY, Ni5Al, Ni21Cr9Mo, Ni21Cr9Mo-SiO2 – sprayed by HVAF has been investigated through detailed laboratory studies in ambient air, moisture and HCl-laden environments. The exposures were conducted at 600 °C for up to 168 h with and without presence of KCl salt. All coatings were highly protective in all environments in the absence of KCl due to formation of corresponding protective scales of alumina or chromia on the coating surface. When KCl was introduced, chromia-forming coatings degraded through a two-stage mechanism; 1) formation of K2CrO4 and Cl- followed by diffusion of Cl- through oxide grain boundaries, leading to formation of Cl2, metal chlorides as well as a nonprotective oxide, and 2) inward diffusion of the formed Cl2 through defects in the non-protective oxide, leading to metal chloride evaporation and breakaway oxidation. The corrosion behavior of the chromia-forming Ni21Cr coating was improved by addition of alloying elements such as Al and Mo. It was also shown that adding dispersed SiO2 further increased the corrosion resistance of the coatings. The oxide scale formed in the presence of SiO2 effectively suppressed Cl- ingress and lowered the corrosion rate, since the formed oxide was continuous, adherent andrich in Cr. The performance of the coatings in the complex Cl-containing environment was ranked as (from highest to lowest corrosion resistance); Ni21Cr9Mo-SiO2 > Ni21Cr7AlY > Ni5Al > Ni21Cr9Mo > Ni21Cr, confirming the enhanced corrosion protection of chromia-forming coatings in the presence of alloying elements and dispersed SiO2.

Place, publisher, year, edition, pages
Trollhättan: University West , 2018. , p. 78
Series
PhD Thesis: University West ; 23
Keywords [en]
Thermal Spray Coating; HVAF; High Temperature Corrosion Protection; Composition; Microstructure; Dispersed Oxide
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-12277ISBN: 978-91-87531-70-5 (print)ISBN: 978-91-87531-69-9 (electronic)OAI: oai:DiVA.org:hv-12277DiVA, id: diva2:1203387
Public defence
2018-05-31, F104, Trollhättan, 10:15 (English)
Opponent
Supervisors
Available from: 2018-05-04 Created: 2018-05-03
List of papers
1. A comparative study on Ni-based coatings prepared by HVAF, HVOF, and APS methods for corrosion protection applications
Open this publication in new window or tab >>A comparative study on Ni-based coatings prepared by HVAF, HVOF, and APS methods for corrosion protection applications
2016 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 8, p. 1604-1616Article 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
Keywords
Thermal Spraying, Process optimization, Corrosion, OCP, Potentiodynamic polarization
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9926 (URN)10.1007/s11666-016-0474-9 (DOI)000390041000016 ()2-s2.0-84994756460 (Scopus ID)
Note

Ingår i lic avhandling

Available from: 2016-09-22 Created: 2016-09-22 Last updated: 2018-05-03Bibliographically approved
2. Isothermal oxidation behavior of HVAF-sprayed Ni and NiCr coatings in H2-H2O environment
Open this publication in new window or tab >>Isothermal oxidation behavior of HVAF-sprayed Ni and NiCr coatings in H2-H2O environment
2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 317, p. 17-25Article in journal (Refereed) Published
Abstract [en]

The formation of a protective chromia scale on stainless steels is known to be suppressed by the presence of water vapor in reducing conditions. Thermal spray coatings present a promising approach to improve the durability of steels by transferring the first line of oxidation attack from the bulk steel to the coating. In the present work, isothermal oxidation behavior of Ni and NiCr coatings deposited by High-Velocity Air Fuel (HVAF) process on 304L stainless steel was investigated at 600 degrees C for 168 h. Ar-10%H-2-20%H2O was selected as the oxidation environment to study the oxidation behavior of the coatings in a low pO(2) environment containing H2 and H2O. BIB/ SEM, EDS, and XRD techniques were used to characterize the as-sprayed coatings and to investigate the oxidation mechanisms in the coated samples. Results showed that both Ni and NiCr coatings imparted oxidation protection to the 304L substrate. The chromia-forming 304L steel presented a duplex but non-protective oxide scale comprising of an outer Fe3O4 layer on an inner (Fe, Cr)(3)O-4-spinel oxide. In contrast, the NiCr coating presented superior oxidation behavior due to the formation of a continuous, thin, and slow-growing Cr2O3 scale. The Ni coating, too, protected the substrate owing to limited nucleation and growth of the deleterious NiO scale in the low-oxygen -activity environment. (C) 2017 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
HVAF; Coating; Oxidation; Water vapor; Hydrogen; Low-oxygen-activity; Pressure
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11396 (URN)10.1016/j.surfcoat.2017.03.049 (DOI)000401204600003 ()2-s2.0-85016073438 (Scopus ID)
Funder
Region Västra Götaland, RUN 2016-01489
Note

Projekt PROSAM

Available from: 2017-08-25 Created: 2017-08-25 Last updated: 2018-05-03Bibliographically approved
3. KCl-Induced High Temperature Corrosion Behavior of HVAF-Sprayed Ni-Based Coatings in Ambient Air
Open this publication in new window or tab >>KCl-Induced High Temperature Corrosion Behavior of HVAF-Sprayed Ni-Based Coatings in Ambient Air
Show others...
2018 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 500-511Article in journal (Refereed) Published
Abstract [en]

KCl-induced high temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y, and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168h. The coatings were deposited onto 16Mo3 steel - a widely used boiler tube material.Uncoated substrate, 304L and Sanicro25 were used as reference materials in the test environment.SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples.The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for Page 1 of 23ASM the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst): Ni5Al >Ni21Cr> Ni21Cr7Al1Y>Ni21Cr9Mo.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials Composite Science and Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-11959 (URN)10.1007/s11666-017-0684-9 (DOI)000425622500022 ()
Conference
International Thermal Spray Conference & Exposition, ITSC 2017, Düsseldorf, Germany, June 7-9, 2017
Funder
Knowledge Foundation, SCoPe: Dnr 20160201
Note

This article is an invited paper selected from presentations at the 2017 International Thermal Spray Conference, held June 7–9, 2017, in Düsseldorf, Germany, that has been expanded from the original presentation.

Available from: 2017-12-29 Created: 2017-12-29 Last updated: 2018-05-03Bibliographically approved
4. Chlorine-induced high temperature corrosion of HVAF-sprayed Ni-based alumina and chromia forming coatings
Open this publication in new window or tab >>Chlorine-induced high temperature corrosion of HVAF-sprayed Ni-based alumina and chromia forming coatings
Show others...
2018 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 132, no March, p. 170-184Article in journal (Refereed) Published
Abstract [en]

Chlorine-induced corrosion of HVAF-sprayed Ni21Cr and Ni5Al coatings was investigated in 5 vol.% O2 + 500vppm HCl + N2 with and without KCl at 600 °C up to 168 h. Both coatings were protective in the absence of KCl. With KCl, Ni21Cr degraded through a two-stage mechanism: 1) formation of K2CrO4 followed by diffusion of Cl− through the oxide grain boundaries to yield chlorine and a non-protective oxide, and 2) inward diffusion of chlorine though defects in the non-protective oxide, leading to breakaway oxidation. Cl−/Cl2 could not diffuse through the protective alumina scale formed on Ni5Al, hence the corrosion resistance increased.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Thermal spray coating, NiCr, NiAl, High-Velocity Air Fuel (HVAF), biomass-/waste-fired boiler, fireside corrosion
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials Composite Science and Engineering
Identifiers
urn:nbn:se:hv:diva-11960 (URN)10.1016/j.corsci.2017.12.033 (DOI)
Funder
Knowledge Foundation, DNR 20160201
Available from: 2017-12-29 Created: 2017-12-29 Last updated: 2018-05-03Bibliographically approved
5. Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings
Open this publication in new window or tab >>Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings
Show others...
2018 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 148, p. 17-29Article in journal (Refereed) Published
Abstract [en]

The oxidation performance of NiCrAlY and NiCrMo coatings thermally sprayed by high velocity air-fuel (HVAF) technique has been investigated in a chloridizing-oxidizing environment, with and without a KCl deposit, at 600 °C for up to 168 h. Both coatings protected the substrate in the absence of KCl due to formation of a dense Cr-rich oxide scale. In the presence of KCl, Cl−/Cl2 diffused through a non-protective and porous NiCr2O4 scale formed on NiCrAlY, leading to formation of volatile CrCl3. On the other hand, Mo in NiCrMo stimulated the formation of a more protective Cr-rich oxide scale which increased the corrosion resistance by reducing Cl−/Cl2 diffusion.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Air; Aluminum corrosion; Boiler corrosion; Chromium compounds; Corrosion protection; Corrosion resistance; High temperature corrosion; Potassium compounds; Scale (deposits); Sprayed coatings; Ternary alloys, Fireside corrosion; High velocity air fuels; NiCrAlY; NiCrMo; Thermal spray coatings, Chlorine compounds
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-12245 (URN)10.1016/j.matdes.2018.03.048 (DOI)000430079200003 ()2-s2.0-85044482024 (Scopus ID)
Note

Available online 22 March 2018.

Available from: 2018-04-09 Created: 2018-04-09 Last updated: 2018-05-14Bibliographically approved

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Sadeghimeresht, Esmaeil

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