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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, 1, 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. 1, p. 20-35Article in journal (Refereed) Epub ahead of print
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)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: 2019-07-25Bibliographically 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
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
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: 2019-05-28Bibliographically 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
Karimi Neghlani, P., Sadeghimeresht, E., Deng, D., Gruber, H., Andersson, J. & Nylen, P. (2018). Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718. The International Journal of Advanced Manufacturing Technology, 99(S1), 2903-2913
Open this publication in new window or tab >>Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718
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2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 99, no S1, p. 2903-2913Article in journal (Refereed) Published
Abstract [en]

Effects of build layout and orientation consisting of (a) height from the build plate (Z-axis), (b) distance between samples, and (c) location in the build plate (X-Y plane) on porosity, NbC fraction, and hardness in electron beam melted (EBM) Alloy 718 were studied. The as-built samples predominantly showed columnar structure with strong ˂001˃ crystallographic orientation parallel to the build direction, as well as NbC and ÎŽ-phase in inter-dendrites and grain boundaries. These microstructural characteristics were correlated with the thermal history, specifically cooling rate, resulted from the build layout and orientation parameters. The hardness and NbC fraction of the samples increased around 6% and 116%, respectively, as the height increased from 2 to 45 mm. Moreover, by increasing the height, formation of ÎŽ-phase was also enhanced associated with lower cooling rate in the samples built with a greater distance from the build plate. However, the porosity fraction was unaffected. Increasing the sample gap from 2 to 10 mm did not change the NbC fraction and hardness; however, the porosity fraction increased by 94%. The sample location in the build chamber influenced the porosity fraction, particularly in interior and exterior areas of the build plate. The hardness and NbC fraction were not dependent on the sample location in the build chamber. © 2018, The Author(s).

Keywords
3D printers, Cooling, Electron beam melting, Electron beams, Grain boundaries, Hardness, Location, Niobium compounds, Porosity, Alloy 718, Build direction, Columnar structures, Crystallographic orientations, Micro-structural characteristics, Micro-structural characterization, Orientation parameter, Sample location, Porous plates
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13043 (URN)10.1007/s00170-018-2621-6 (DOI)000452076900065 ()2-s2.0-85053670925 (Scopus ID)
Funder
European Regional Development Fund (ERDF)Knowledge Foundation
Note

First Online: 17 September 2018

Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2019-05-28Bibliographically approved
Sadeghimeresht, E., Reddy, L., Hussain, T., Huhtakangas, M., Markocsan, N. & Joshi, S. V. (2018). Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings. Materials & design, 148, 17-29
Open this publication in new window or tab >>Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings
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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.

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)
Funder
Knowledge Foundation, RUN 20160201Region Västra Götaland, RUN 2016-01489
Note

Available online 22 March 2018.

Available from: 2018-04-09 Created: 2018-04-09 Last updated: 2019-05-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-7663-9631

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