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Sadeghi, E., Markocsan, N. & Joshi, S. V. (2019). Advances in Corrosion-Resistant Thermal Spray Coatings for Renewable Energy Power Plants. Part I: Effect of Composition and Microstructure. Journal of thermal spray technology (Print)
Open this publication in new window or tab >>Advances in Corrosion-Resistant Thermal Spray Coatings for Renewable Energy Power Plants. Part I: Effect of Composition and Microstructure
2019 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016Article in journal (Refereed) Epub ahead of print
Abstract [en]

Power generation from renewable resources has attracted increasing attention in recent years owing to the global implementation of clean energy policies. However, such power plants suffer from severe high-temperature corrosion of critical components such as water walls and superheater tubes. The corrosion is mainly triggered by aggressive gases like HCl, H2O, etc., often in combination with alkali and metal chlorides that are produced during fuel combustion. Employment of a dense defect-free adherent coating through thermal spray techniques is a promising approach to improving the performances of components as well as their lifetimes and, thus, significantly increasing the thermal/electrical efficiency of power plants. Notwithstanding the already widespread deployment of thermal spray coatings, a few intrinsic limitations, including the presence of pores and relatively weak intersplat bonding that lead to increased corrosion susceptibility, have restricted the benefits that can be derived from these coatings. Nonetheless, the field of thermal spraying has been continuously evolving, and concomitant advances have led to progressive improvements in coating quality; hence, a periodic critical assessment of our understanding of the efficacy of coatings in mitigating corrosion damage can be highly educative. The present paper seeks to comprehensively document the current state of the art, elaborating on the recent progress in thermal spray coatings for high-temperature corrosion applications, including the alloying effects, and the role of microstructural characteristics for understanding the behavior of corrosion-resistant coatings. In particular, this review comprises a substantive discussion on high-temperature corrosion mechanisms, novel coating compositions, and a succinct comparison of the corrosion-resistant coatings produced by diverse thermal spray techniques.

National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14700 (URN)10.1007/s11666-019-00938-1 (DOI)
Funder
Knowledge Foundation, (RUN 20160201Region Västra Götaland, RUN 2016-01489
Available from: 2019-11-15 Created: 2019-11-15 Last updated: 2019-11-15
Sadeghi, E. & Joshi, S. V. (2019). Chlorine-induced high-temperature corrosion and erosion-corrosion of HVAF and HVOF-sprayed amorphous Fe-based coatings. Surface & Coatings Technology, 371(S1), 20-35
Open this publication in new window or tab >>Chlorine-induced high-temperature corrosion and erosion-corrosion of HVAF and HVOF-sprayed amorphous Fe-based coatings
2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no S1, p. 20-35Article in journal (Refereed) Published
Abstract [en]

Chlorine-induced high-temperature corrosion and erosion-corrosion behavior of amorphous Fe-based coatings sprayed by high velocity air-fuel (HVAF) and high velocity oxy-fuel (HVOF) techniques were investigated. The coated specimens were first exposed to isothermal high-temperature corrosion at 600 °C in ambient air with and without KCl. The exposed specimens were then subjected to alumina erodent. The as-sprayed HVAF coating showed a more compact and uniform microstructure with a higher hardness leading to higher corrosion and erosion-corrosion resistance. After erosion, all the coatings similarly exhibited a combined brittle/ductile damage to surface oxide scale that previously formed in the corrosive environment. The corrosion and erosion-corrosion behavior of the coatings primarily relied on the uniformity of coatings’ microstructure and distribution of alloying elements to form the protective oxide scale in the corrosive environment, which can resist against erodent in the erosive media. © 2019 Elsevier B.V.

Keywords
Air, Alloying elements, Alumina, Aluminum oxide, Chlorine, Corrosion resistance, Corrosive effects, Erosion, Fuels, High temperature corrosion, HVOF thermal spraying, Microstructure, Potassium compounds, Scale (deposits), Sprayed coatings, Thermal spraying, Amorphous coating, Chlorine-induced high-temperature corrosion, Erosion - corrosions, HVAF, HVOF, Corrosion resistant coatings
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13514 (URN)10.1016/j.surfcoat.2019.01.080 (DOI)000472694300004 ()2-s2.0-85060532855 (Scopus ID)
Funder
Knowledge Foundation, RUN 20160201Region Västra Götaland, 2016-01489
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-10-16Bibliographically approved
Karimi Neghlani, P., Sadeghi, E., Ålgårdh, J. & Andersson, J. (2019). EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics. Materials Characterization, 148, 88-99
Open this publication in new window or tab >>EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics
2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 148, p. 88-99Article in journal (Refereed) Published
Abstract [en]

Electron beam melting-powder bed fusion (EBM-PBF) is an additive manufacturing process, which is able to produce parts in layer-by-layer fashion from a 3D model data. Currently application of this technology in parts manufacturing with high geometrical complexity has acquired growing interest in industry. To recommend the EBM process into industry for manufacturing parts, improved mechanical properties of final part must be obtained. Such properties highly depend on individual single melted track and single layer. In EBM, interactions between the electron beam, powder, and solid underlying layer affect the geometrical (e.g., re-melt depth, track width, contact angle, and track height) and microstructural (e.g., grain structure, and primary dendrite arm spacing) characteristics of the melted tracks. The core of the present research was to explore the influence of linear energy input parameters in terms of beam scanning speed, beam current as well as focus offset and their interactions on the geometry and microstructure of EBM-manufactured single tracks of Alloy 718. Increased scanning speed led to lower linear energy input values (<0.9 J/mm) in an specific range of the focus offset (0–10 mA) which resulted in instability, and discontinuity of the single tracks as well as balling effect. Decreasing the scanning speed and increasing the beam current resulted in higher melt pool depth and width. By statistical evaluations, the most influencing parameters on the geometrical features were primarily the scanning speed, and secondly the beam current. Primary dendrite arm spacing (PDAS) slightly decreased by increasing the scanning speed using lower beam current values as the linear energy input decreased. By increasing the linear energy input, the chance of more equiaxed grain formation was high, however, at lower linear energy input, mainly columnar grains were observed. The lower focus offset values resulted in more uniform grains along the 〈001〉 crystallographic direction. © 2018 Elsevier Inc. 

Keywords
3D printers; Contact angle; Dendrites (metallography); Design of experiments; Electron beam melting; Electron beams; Scanning; Speed, Alloy 718; Geometrical characteristics; Powder bed; Single-tracks; Solidified microstructures, Geometry
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13365 (URN)10.1016/j.matchar.2018.11.033 (DOI)2-s2.0-85058512738 (Scopus ID)
Funder
European Regional Development Fund (ERDF)Knowledge Foundation
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-02-28Bibliographically approved
Zhang, P., Sadeghi, E., Chen, S., Li, X.-H., Markocsan, N., Joshi, S. V., . . . Peng, R. L. n. (2019). Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings. Surface & Coatings Technology, 364, 43-56
Open this publication in new window or tab >>Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings
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2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 364, p. 43-56Article in journal (Refereed) Published
Abstract [en]

Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

Keywords
Oxidation, Transient to alpha transformation, Surface treatment, Polishing, Shot-peening, Photo-stimulated luminescence spectroscopy
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13736 (URN)10.1016/j.surfcoat.2019.02.068 (DOI)000463302800006 ()2-s2.0-85062231529 (Scopus ID)
Funder
Swedish Energy Agency, KME-703
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-07-01Bibliographically approved
Eklund, J., Phother, J., Sadeghi, E., Joshi, S. V. & Liske, J. (2019). High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications. Oxidation of Metals, 91(5-6), 729-747
Open this publication in new window or tab >>High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications
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2019 (English)In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 91, no 5-6, p. 729-747Article in journal (Refereed) Published
Abstract [en]

The present study investigates the initial corrosion behaviour of HVAF-sprayed NiCr, NiAl and NiCrAlY coatings in two different environments, O 2 + H 2 O and O 2 + H 2 O + KCl at 600 °C for up to 168 h in order to evaluate the possibility of utilizing such coatings in biomass- and waste-fired boilers. SEM/EDX analysis showed that all coatings displayed a protective behaviour in O 2 + H 2 O. Upon addition of KCl (O 2 + H 2 O + KCl), the corrosion behaviour of the NiCr coating drastically changed as it formed a thick oxide layer and displayed major chlorine diffusion down to the substrate. The NiCrAlY coating displayed a significantly better corrosion resistance with only minor oxide formation. The NiAl coating exhibited a protective behaviour similar to when exposed in the absence of KCl indicating that a thin protective oxide has formed on the coating surface. The performance of the NiAl and NiCrAlY coatings is promising for future studies with long-term exposures in more corrosive environments such as in a biomass- and waste-fired boiler. © 2019, The Author(s).

Keywords
Aluminum alloys; Aluminum corrosion; Binary alloys; Biomass; Boiler corrosion; Boilers; Chlorine compounds; Chromium alloys; Corrosion resistance; Corrosion resistant coatings; Corrosive effects; Diffusion coatings; High temperature applications; High temperature corrosion; Sprayed coatings; Wastes, Corrosion behaviour; Corrosive environment; HVAF; Long term exposure; Ni-based coatings; NiCrAlY coating; Protective oxides; Waste-fired boilers, Potassium compounds
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13758 (URN)10.1007/s11085-019-09906-0 (DOI)000467574600011 ()2-s2.0-85062942037 (Scopus ID)
Funder
Knowledge Foundation, RUN 2016-0201Region Västra Götaland, RUN 2016-01489
Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-06-05
Jafari, R. & Sadeghi, E. (2019). High-temperature corrosion performance of HVAF-sprayed NiCr, NiAl, and NiCrAlY coatings with alkali sulfate/chloride exposed to ambient air. Corrosion Science, 160, Article ID 108066.
Open this publication in new window or tab >>High-temperature corrosion performance of HVAF-sprayed NiCr, NiAl, and NiCrAlY coatings with alkali sulfate/chloride exposed to ambient air
2019 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 160, article id 108066Article in journal (Refereed) Published
Abstract [en]

The high-temperature corrosion of high velocity air-fuel (HVAF) thermal spray Ni21Cr, Ni5Al, and Ni21Cr7AlY coatings was investigated at 600 °C for 168 h in ambient air under KCl and 50-50 mol% KCl–K2SO4 salts. Chlorination-oxidation cycle and breakdown of the corrosion products layer were the dominant corrosion mechanism in the chromia-forming Ni21Cr and Ni21Cr7AlY coatings exposed to KCl. KCl–K2SO4 was less corrosive to the chromia-forming coatings as K2SO4 was less reactive to the protective Cr-rich oxide. The alumina-forming NiAl exhibited a better corrosion performance under KCl, though it partially suffered from selective sulfidation when exposed to the mixed salt. © 2019 Elsevier Ltd

Place, publisher, year, edition, pages
Pergamon Press, 2019
Keywords
Air; Alumina; Aluminum alloys; Aluminum oxide; Binary alloys; Chlorine compounds; Chromium compounds; Corrosion protection; High temperature corrosion; Nickel coatings; Potash; Sprayed coatings; Sulfur compounds, A. KCl-K2SO4B; Alkali sulfates; Corrosion mechanisms; Corrosion performance; Corrosion products; High velocity air fuels; Nickel-based coatings; NiCrAlY coating, Aluminum corrosion
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-14490 (URN)10.1016/j.corsci.2019.06.021 (DOI)2-s2.0-85071852542 (Scopus ID)
Funder
Knowledge Foundation, RUN 20160201Region Västra Götaland
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-11-15Bibliographically approved
Sadeghi, E., Karimi Neghlani, P., Momeni, S., Seifi, M., Eklund, A. & Andersson, J. (2019). Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718. Materials Characterization, 150, 236-251
Open this publication in new window or tab >>Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718
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2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 150, p. 236-251Article in journal (Refereed) Published
Abstract [en]

The effect of thermal post treatments consisting of heat treatment (HT), hot isostatic pressing (HIP), and combined HIP-HT on microstructure and oxidation behavior of Alloy 718 manufactured by electron beam powder bed fusion (EB-PBF) technique was investigated. Oxidation of the as-built and post-treated specimens was performed in ambient air at 650, 750, and 850 °C for up to 168 h. Directional columnar-grained microstructure, pores and fine Nb-rich carbides were observed in the as-built specimen. The HT specimen presented the columnar microstructure, plate-like δ phase at grain boundaries, and pores. The dominant grain crystallographic orientation was changed from 〈001〉 in the as-built specimen to 〈101〉 after HT. No grain boundary δ phase was observed in the HIPed specimen, but recrystallization occurred in both the HIP and HIP-HT specimens due to a rapid cooling after HIPing motivating the nucleation of fine grains with limited time to grow. After oxidation exposure at 650 and 750 °C for 168 h, no big difference between weight changes of the as-built and post-treated specimens was noted, whereas at 850 °C, the combined HIP-HT specimen showed the most promising corrosion resistance with the least weight change. At 850 °C, a protective scale of Cr 2 O 3 rich in Cr, Ti, and Ni as well as an internal oxide (branched structure of alumina) developed in all the specimens, while, only a protective Cr 2 O 3 scale was found at 650 and 750 °C. The HIP-HT specimen at 850 °C developed an oxide scale, which was denser and more adherent in comparison to the oxide scales formed on the other three specimens, associated with its limited defect distribution and more homogenized microstructure. Moreover, the δ phase formed close to the surface of the exposed specimens during the oxidation exposure at 850 °C most probably led to nucleation and growth of the oxide scale. © 2019 Elsevier Inc.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Additive manufacturing, Electron beam powder bed fusion, Alloy 718, Oxidation, Heat treatment, Hot isostatic pressing
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13740 (URN)10.1016/j.matchar.2019.02.016 (DOI)000462420900027 ()2-s2.0-85062014143 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-05-10Bibliographically approved
Sadeghimeresht, E., Reddy, L., Hussein, T., Markocsan, N. & Joshi, S. V. (2018). Chlorine-induced high temperature corrosion of HVAF-sprayed Ni-based alumina and chromia forming coatings. Corrosion Science, 132(March), 170-184
Open this publication in new window or tab >>Chlorine-induced high temperature corrosion of HVAF-sprayed Ni-based alumina and chromia forming coatings
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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.

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
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11960 (URN)10.1016/j.corsci.2017.12.033 (DOI)000424961000016 ()2-s2.0-85039789597 (Scopus ID)
Funder
Knowledge Foundation, DNR 20160201
Available from: 2017-12-29 Created: 2017-12-29 Last updated: 2019-10-21Bibliographically approved
Sadeghimeresht, E., Markocsan, N., Hussain, T., Huhtakangas, M. & Joshi, S. V. (2018). Effect of SiO2 Dispersion on Chlorine-Induced High-Temperature Corrosion of High-Velocity Air-Fuel Sprayed NiCrMo Coating. Corrosion, 74(9), 984-1000
Open this publication in new window or tab >>Effect of SiO2 Dispersion on Chlorine-Induced High-Temperature Corrosion of High-Velocity Air-Fuel Sprayed NiCrMo Coating
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2018 (English)In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 74, no 9, p. 984-1000Article in journal (Refereed) Published
Abstract [en]

NiCrMo coatings with and without dispersed SiO2 were deposited using high-velocity air-fuel technique. Thermogravimetric experiments were conducted in 5% O-2 + 500 vppm HCl + N-2 with and without a KCl deposit at 600 degrees C for up to 168 h. The SiO2-containing coating showed lower weight change as a result of formation of a protective and adherent Cr-rich oxide scale. SiO2 decelerated short-circuit diffusion of Cr3+ through scale's defects, e.g., vacancies, and promoted the selective oxidation of Cr to form the protective Cr-rich oxide scale. Furthermore, the presence of SiO2 led to less subsurface depletion of Cr in the coating, and accordingly less corrosion of the substrate. The formed corrosion product on the SiO2-free coating was highly porous, non-adherent, and thick.

Keywords
Thermal Spray Coating, Chlorine-Induced High Temperature Corrosion, NiCrMo, SiO2Dispersion, HighVelocity Air-Fuel (HVAF), Biomass-/Waste-Fired Boiler
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12903 (URN)10.5006/2802 (DOI)000442637200005 ()2-s2.0-85052839267 (Scopus ID)
Funder
Knowledge Foundation, RUN 20160201Region Västra Götaland, RUN 2016-01489
Note

Published Online: April 24, 2018

Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2019-05-28Bibliographically approved
Sadeghimeresht, E., Eklund, J., Simon, J. P., Liske, J., Markocsan, N. & Joshi, S. V. (2018). Effect of water vapor on the oxidation behavior of HVAF-sprayed NiCr and NiCrAlY coatings. Materials and corrosion - Werkstoffe und Korrosion, 69(10), 1431-1440
Open this publication in new window or tab >>Effect of water vapor on the oxidation behavior of HVAF-sprayed NiCr and NiCrAlY coatings
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2018 (English)In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 69, no 10, p. 1431-1440Article in journal (Refereed) Published
Abstract [en]

Isothermal oxidation behavior of NiCr and NiCrAlY coatings deposited onto low alloy 16Mo3 steel by high-velocity air fuel (HVAF) process was investigated in 5% O-2+20% H2O+N-2 at 600 degrees C for 168h. Whereas NiCrAlY showed lower mass gain compared to NiCr, both coatings succeeded in maintaining the integrity with the substrate during the exposure without any breakaway oxidation. A thin Cr-rich oxide scale (Cr2O3) formed on NiCr, and a thin mixed oxide scale (Al2O3 with NiCr2O4) formed on NiCrAlY significantly increasing the oxidation protection in the presence of water vapor.

Keywords
NiCr, NiCrAlY, oxidation protection, thermal spray coating, water vapor
National Category
Manufacturing, Surface and Joining Technology Corrosion Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13036 (URN)10.1002/maco.201710005 (DOI)000446266800012 ()2-s2.0-85047644588 (Scopus ID)
Funder
Knowledge Foundation, RUN 2016-0201Region Västra Götaland, RUN 2016-01489
Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2019-05-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-7663-9631

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