| 1. |
- Larché, Nicolas, et al.
(författare)
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Internal corrosion of copper-nickel alloy tubes 90/10 and 70/30 in chlorinated seawater for shell and tube heat exchangers
- 2019
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Article number 13338Corrosion Conference and Expo 2019; Nashville; United States; 24 March 2019 through 28 March 2019;ACE - Int. Corros. Conf. Ser.. - : National Assoc. of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- The corrosion resistance of copper-nickel 90/10 and 70/30 tubes for heat exchangers was evaluated in 0.5 ppm-chlorinated seawater, under controlled service conditions in a bespoke test loop. The results were compared to Al-Brass tubes tested under the same conditions. Copper-Nickel 90/10 tubes were tested with two different geometries: internal smooth surface and internal finned surface (helix geometry). Internal pitting corrosion resistance was evaluated under simulated heat transfer conditions at two controlled skin temperatures from the internal and the external parts of the tubes for 6 months, at 50°C (Tskin-in)/35°C (Tseawater) and 70°C (Tskin-in)/35°C (Tseawater). For all the tested copper alloys, the uniform corrosion was very low and negligible. For both temperatures, CuNi 90/10 was globally more resistant to localized corrosion than CuNi70/30. The most corrosion resistant configuration was the CuNi 90/10 with the internal finned geometry. The best corrosion resistance compared to the smooth geometry might be attributed to different hydrodynamic conditions at the seawater/metal interface.
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| 2. |
- Rinaldi, A., et al.
(författare)
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Materials for high temperature liquid lead storage for concentrated solar power (Csp) air tower systems
- 2021
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- Today the technical limit for solar towers is represented by the temperature that can be reached with current accumulation and exchange fluids (molten salts are generally adopted and the max temperatures are generally below 600◦ C), even if other solutions have been suggested that reach 800◦ C. An innovative solution based on liquid lead has been proposed in an ongoing experimental project named Nextower. The Nextower project aims to improve current technologies of the solar sector by transferring experience, originally consolidated in the field of nuclear plants, to accumulate heat at higher temperatures (T = 850–900◦ C) through the use of liquid lead heat exchangers. The adoption of molten lead as a heat exchange fluid poses important criticalities of both corrosion and creep resistance, due to the temperatures and structural stresses reached during service. Liquid lead corrosion issues and solutions in addition to creep-resistant material selection are discussed. The experimental activities focused on technical solutions adopted to overcome these problems in terms of the selected materials and technologies. Corrosion laboratory tests have been designed in order to verify if structural 800H steel coated with 6 mm of FeCrAl alloy layers are able to resist the liquid lead attack up to 900◦ C and for 1000 h or more. The metallographic results were obtained by mean of scanning electron microscopy with an energy dispersive microprobe confirm that the 800H steel shows no sign of corrosion after the completion of the tests.
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| 3. |
- Linder, Clara, et al.
(författare)
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Corrosion resistance of additively manufactured aluminium alloys for marine applications
- 2024
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Ingår i: npj Materials Degradation. - : Springer. - 2397-2106. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing opens new possibilities for designing light-weight structures using aluminium alloys. The microstructure of two Al alloys and their corrosion resistance in NaCl and natural seawater environments were investigated. The newly designed Al-Mn-Cr-Zr based alloy showed a higher corrosion resistance than reference AlSi10Mg alloy in both environments in as printed and heat-treated conditions. The corrosion initiated in the Al matrix along the precipitates in the alloys where the Volta potential difference was found the highest. The coarser microstructure and precipitate composition of the new Al-alloy led to the formation of a resistant passive film which extended the passivity region of the Al-Mn-Cr-Zr alloy compared to the AlSi10Mg alloy. The effect of heat treatment could be seen in the microstructure as more precipitates were found in between the melt pool boundaries, which affected the corrosion initiation and slightly the pitting resistance. Overall, this study shows that a newly designed Al-alloy for additive manufacturing has a suitable corrosion resistance for applications in marine environments.
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| 4. |
- Stålnacke, E., et al.
(författare)
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Corrosion–microstructure interrelations in new low-lead and lead-free brass alloys
- 2020
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Ingår i: Materials Science and Technology. - : Taylor and Francis Ltd.. - 0267-0836 .- 1743-2847. ; 36:8, s. 917-924
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Tidskriftsartikel (refereegranskat)abstract
- Stress-relieving heat treatment has been reported to deplete the corrosion resistance of new low-lead and lead-free brass alloys. How the heat treatment, processing and material composition relates to the microstructure and corrosion performance is not well understood. The present study aims to fill this knowledge gap by mapping stress-relieving annealing conditions and different standardised compositions to their respective microstructures and dezincification performance. It was found that loss of corrosion resistance was only the most severe for alloys with higher aluminium and iron content. These alloys displayed significant precipitation of intermetallic aluminium arsenide particles on grain boundaries, twins and lead particles, as well as the formation of β-phase along grain boundaries.
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| 5. |
- Cassagne, Thierry B., et al.
(författare)
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Replacing titanium in sea water plate heat exchangers
- 2010
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Ingår i: NACE - International Corrosion Conference Series.
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Konferensbidrag (refereegranskat)abstract
- The use of titanium plate heat exchangers is widespread for Offshore and Coastal installations where seawater cooling is required. Several years ago difficulties to supply titanium Grade 1 for this application triggered the need for qualification of other alloys for this application. Applications using passive alloys are especially susceptible to crevice corrosion when exposed to hot seawater. Since titanium is the most corrosion resistant alloy in seawater only highly corrosion resistant alloys could be considered for its replacement in plate heat exchangers. In addition since they need to be shaped into plates by cold pressing only alloys with a high formability could be selected. This narrowed even further candidate alloys for plate heat exchangers. In this study nickel chromium molybdenum alloys and a highly alloyed stainless steel were tested between 30 and 70°C in natural seawater with up to 1 ppm free chlorine. Rather than using short term electrochemical testing that is often difficult to compare with service performance long term exposure tests (up to 18 months) of real plate heat exchangers were carried out. These tests are considered to be more representative of actual service conditions. The results of these tests and their significance are discussed and compared with previous reported work.
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| 6. |
- Karasev, Andrey, et al.
(författare)
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Characterization of non-metallic inclusions in corrosion -resistance nickel - Based EP718 and 718 alloys by using electrolytic extraction method
- 2019
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Ingår i: E3S Web of Conferences. - : EDP Sciences. - 2267-1242.
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Konferensbidrag (refereegranskat)abstract
- It is known that non-metallic inclusions (NMI) that are formed during steel production and heat treatment can significantly affect the properties of final steel products. Therefore, it is very important to be able to determine the content of harmful NMI in steels. Nickel-based alloys are widely used in the oil and gas recovery industry, due to a good combination of strength and corrosion properties. Earlier studies have shown that the corrosion properties in immersion test and electrochemical tests for Ni-based EP718 alloys are slightly lower than that for 718 alloys. The focus in this study was the influence of different NMI on the corrosion resistance of these alloys. The characteristics of inclusions (such as size, morphology, and chemical composition) were analysed by using the electrolytic extraction method followed by three-dimensional investigations using SEM in combination with EDS. It was found that some non-metallic inclusions in EP718 alloys significantly reduce its corrosion resistance. It was also shown that a primary dissolution of the metal matrix occurs around certain inclusions during electrolytic extraction. Based on obtained results, the corrosion active non-metallic inclusions can be determined in these Nickel-base alloys and some recommendations for optimization of their production technology can be formulated.
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| 7. |
- Westin, Elin M., et al.
(författare)
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Laser welding of a lean duplex stainless steel
- 2007
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Ingår i: 26th International Congress on Applications of Lasers and Electro-Optics, ICALEO 2007. - 9780912035888 ; , s. 335-344
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Konferensbidrag (refereegranskat)abstract
- Nd:YAG laser welding and laser gas tungsten arc (GTA) hybrid welding of the lean duplex stainless steel LDX 2101® (EN 1.4162, UNS S32101) were performed with and without filler wire and nitrogen additions to the shielding gas. The high energy density associated with laser welding of duplex stainless steels can affect the mechanical strength and corrosion resistance negatively. The high solidification rates and cooling rates characteristic of laser welding may cause ferritization and chromium nitride precipitation. However, due to the balanced composition of LDX 2101, the austenite reformation in the weld metal and the heat affected zone (HAZ) was satisfactory as confirmed by tensile test results, corrosion performance in terms of critical pitting temperature (CPT) and hardness measurements. Transmission electron microscopy (TEM) was conducted on simulated HAZs to study the effect of cooling rate on precipitate formation. Furthermore, Laser-GTA hybrid welding of the galvanized carbon steel Dogal® DP 600 onto LDX 2101 in lap joints was successful without porosity or liquid metal embrittlement (LME), and with sufficient tensile strength.
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| 8. |
- Asala, Gbenga, et al.
(författare)
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Hot corrosion behaviour of wire-arc additive manufactured Ni-based superalloy ATI 718Plus®
- 2019
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 158
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Tidskriftsartikel (refereegranskat)abstract
- The hot corrosion behaviour of wire-arc additive manufactured and wrought ATI 718Plus® are studied. ATI 718Plus® produced by the additive manufacturing process, in the as-processed condition, exhibits a significantly lower hot corrosion resistance in comparison to the wrought alloy. Analytical electron microscopy and spectroscopy techniques, with corroboration by thermodynamic calculations, are used to identify the underlying cause of the poor hot corrosion resistance. Based on the understanding accrued from the analyses, post-processing heat treatments are used to improve the hot corrosion resistance, which is valuably pertinent to the application of ATI 718Plus® produced by additive manufacturing in hot corrosive environments. © 2019 Elsevier Ltd
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