Scale Formation and Degradation of Diffusion Coatings Deposited on 9% Cr Steel in Molten Solar Salt
Source abstract
Abstract
The employment of ferritic-martensitic steels e.g., P91, as structural materials in concentrated solar power (CSP) plants can significantly increase cost-efficiency. However, their application is strongly restricted by their lower corrosion resistance in molten nitrates, compared to austenitic steels or Ni-based alloys. In this study, Cr-, Al-, and Cr/Al-diffusion coatings were deposited on P91 via pack cementation in order to improve its scaling behavior in molten solar salt (MSS). The corrosion behavior of coated specimens was investigated with respect to uncoated P91 in MSS at 600 °C for up to 1000 h. The exposure in MSS resulted in a thick, highly porous, and multi-layered oxide scale on uncoated P91 consisting of hematite, magnetite, and sodium ferrite. On the other hand, the scale grown on the chromized P91 comprised of a thin Cr-rich inner layer, which shifted breakaway to prolonged exposure durations. The aluminized specimens both formed very thin, highly protective alumina scales with localized protrusions.
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Research context
OpenAlex topics: Solar Thermal and Photovoltaic Systems · Phase Change Materials Research · High-Temperature Coating Behaviors
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
DECHEMA-Forschungsinstitut, Theodor-Heuss-Allee 25 60486 Frankfurt (Main), Germany
Funding
Horizon 2020
References (56)
Show source-provided references
1. Advanced heat transfer fluids for direct molten salt line-focusing CSP plants10.1016/j.pecs.2018.02.002 ↗
2. Corrosion behavior of stainless and low-chromium steels and IN625 in molten nitrate salts at 600 C10.1016/j.solmat.2015.08.011 ↗
3. Innovation in concentrated solar power10.1016/j.solmat.2011.05.020 ↗
4. Heat transfer fluids for concentrating solar power systems—A review10.1016/j.apenergy.2015.01.125 ↗
5. Concentrating solar power tower technology: Present status and outlook10.1515/nleng-2017-0171 ↗
6. Agüero, A., Audigié, P., Rodríguez, S., Encinas-Sánchez, V., de Miguel, M.T., and Pérez, F.J. (2018). Protective coatings for high temperature molten salt heat storage systems in solar concentration power plants. AIP Conference Proceedings, AIP Publishing.10.1063/1.5067095 ↗
7. Bonk, A., Braun, M., Hanke, A., Forstner, J., Rückle, D., Kaesche, S., Sötz, V.A., and Bauer, T. (2018). Influence of different atmospheres on molten salt chemistry and its effect on steel corrosion. AIP Conference Proceedings, AIP Publishing.10.1063/1.5067097 ↗
8. A review of the chemical and physical properties of molten alkali nitrate salts and their effect on materials used for solar central receivers
9. Corrosion of iron stainless steels in molten nitrate salt10.1016/j.egypro.2014.03.095 ↗
10. High temperature corrosion beneath nitrate melts10.1002/maco.201307076 ↗
11. Corrosion behavior of structural materials for potential use in nitrate salts based solar thermal power plants10.1149/2.0501708jes ↗
12. Slurry aluminizing: A solution for molten nitrate salt corrosion in concentrated solar power plants10.1016/j.solmat.2015.11.024 ↗
13. Molten salt corrosion of stainless steels and low-Cr steel in CSP plants10.1007/s11085-012-9310-x ↗
14. Molten nitrate salts at 600 and 680 C: Thermophysical property changes and corrosion of high-temperature nickel alloys10.1016/j.solener.2014.01.028 ↗
15. Selman, R., and Braunstein, J. The hot corrosion of metals by molten salts. Proceedings of the Second International Symposium on Molten Salts.
16. Tortorelli, P.F., Bishop, P.S., and DiStefano, J.R. (1989). Selection of Corrosion-Resistant Materials for Use in Molten Nitrate Salts ORNL/TM-11162.10.2172/5236321 ↗
17. Bradshaw, R.W., and Clift, W.M. (2010). Effect of Chloride Content of Molten Nitrate Salt on Corrosion of A516 Carbon Steel.10.2172/1002088 ↗
18. High temperature corrosion in molten solar salt: The role of chloride impurities10.1002/maco.201609300 ↗
19. Electrochemical impedance spectroscopy (EIS): An efficient technique for monitoring corrosion processes in molten salt environments in CSP applications10.1016/j.solmat.2018.11.007 ↗
20. Bradshaw, R.W., and Goods, S.H. (2001). Corrosion Resistance of Stainless Steels During Thermal Cycling in Alkali Nitrate Molten Salts.10.2172/1020472 ↗
21. Corrosion of stainless steels and carbon steel by molten mixtures of commercial nitrate salts10.1361/10599490417542 ↗
22. Corrosion in molten nitrate-nitrite salts10.1007/BF03259692 ↗
23. Fähsing, D. (2015). Ferritisch Martensitische Stähle: Verbesserung der Oxidationsbeständigkeit in Wasserdampfhaltigen Hochtemperaturatmosphären. [Ph.D. Thesis, RWTH Aachen, Shaker Verlag].
24. Aluminide slurry coatings for protection of ferritic steel in molten nitrate corrosion for concentrated solar power technology10.1063/1.4984416 ↗
25. High temperature molten salt corrosion behavior of aluminide and nickel-aluminide coatings for heat storage in concentrated solar power plants10.1016/j.surfcoat.2018.05.081 ↗
26. Corrosion testing of diffusion-coated steel in molten salt for concentrated solar power tower systems10.1016/j.surfcoat.2018.08.097 ↗
27. (2011). Material Data Sheet P91/T91, Thyssen Krupp Materials International.
28. Goward, G.W. (1976, January 17). Protective Coatings for High Temperature Alloys: State of Technology. Proceedings of the Symposium on Properties of High-Temperature Alloys with Emphasis on Environmental Effects, New York, NY, USA.
29. Lang, E. (1983). Protective Coatings for High Temperature Materials: Chemical Vapour Deposition and Pack Cementation Processes. Coatings for High Temperature Applications, Applied Science Publishers.
30. Pack cementation processes10.1179/mst.1986.2.3.201 ↗
31. Diffusion coatings for high temperature corrosion protection of 9–12% Cr steels10.1179/174327805X66272 ↗
32. (2015). ISO 17245:2015 Corrosion of Metals and Alloys—Test Method for High Temperature Corrosion Testing of Metallic Materials by Immersing in Molten Salt or Other Liquids under Static Conditions, ISO.
33. Ferritic–martensitic steels: Improvement of the oxidation behavior in steam environments via diffusion coatings10.1016/j.surfcoat.2013.09.018 ↗
34. Stern, K.H. (1996). Pack cementation diffusion coatings. Metallurgical and Ceramic Protective Coatings, Chapman & Hall.10.1007/978-94-009-1501-5 ↗
35. Diffusion chromizing of ferrous alloys10.1016/0257-8972(89)90040-6 ↗
36. Long exposure steam oxidation testing and mechanical properties of slurry aluminide coatings for steam turbine components10.1016/j.surfcoat.2005.07.080 ↗
37. Creep behavior of pack cementation aluminide coatings on grade 91 ferritic–martensitic alloy10.1016/j.surfcoat.2013.12.008 ↗
38. Development of novel diffusion coatings for 9–12% Cr ferritic-martensitic steels10.1002/maco.200503918 ↗
39. Formation of aluminide coatings on Fe-based alloys by chemical vapor deposition10.1016/j.surfcoat.2008.01.023 ↗
40. Improvements in the thermodynamic and kinetic considerations on the coating design for diffusion coatings formed via pack cementation10.1002/maco.201407810 ↗
41. Touloukian, Y.S., Kirby, R.K., Taylor, R.E., and Desai, P.D. (1970). Thermal Expansion of Metallic Elements and Alloy, Plenum Publishing Corporation.
42. Fireside Corrosion of Chromium-and Aluminum-Coated Ferritic–Martensitic Steels10.1007/s11085-016-9684-2 ↗
43. Effect of nitrogen on the formation and oxidation behavior of iron aluminide coatings10.1016/j.surfcoat.2005.07.081 ↗
44. The Al–Cr–Fe system–Phases and phase equilibria in the Al-rich corner10.1016/S0925-8388(96)02719-3 ↗
45. Al–Cr–Fe phase diagram. Isothermal Sections in the region above 50 at% Al10.1016/j.calphad.2013.12.007 ↗
46. Evolution of aluminide coating microstructure on nickel-base cast superalloy CM-247 in a single-step high-activity aluminizing process10.1007/s11661-998-0042-0 ↗
47. Fitzpatrick, M.E., Fry, A.T., Holdway, P., Kandil, F.A., Shackleton, J., and Suominen, L. (2005). Determination of Residual Stresses by X-ray Diffraction Measurement Good Practice Guide 52, National Physical Laboratory.
48. New methods for diffraction stress measurement: A critical evaluation of new and existing methods10.1107/S0021889800004258 ↗
49. Steam oxidation of aluminide coatings under high pressure and for long exposures10.1016/j.corsci.2018.08.053 ↗
50. Oxidation of NiAl and FeAl10.1016/S0966-9795(99)00037-0 ↗
51. The influence of alloying elements on the development and maintenance of protective scales10.1007/BF01046725 ↗
52. Composition, microstructure, and water vapor effects on internal/external oxidation of alumina-forming austenitic stainless steels10.1007/s11085-009-9161-2 ↗
53. Initial oxidation of Fe–Al and Fe–Cr–Al alloys: Cr as an alumina booster10.1007/s11085-011-9258-2 ↗
54. Strain Determination in Thermally-Grown Alumina Scales Using Fluorescence Spectroscopy10.1007/BF02153461 ↗
55. Thermodynamic modeling of the (Al2O3 + Na2O), (Al2O3 + Na2O + SiO2), and (Al2O3 + Na2O + AlF3 + NaF) systems10.1016/j.jct.2012.09.002 ↗
56. Corrosion of alumina-forming austenitic steel in molten nitrate salts by gravimetric analysis and impedance spectroscopy10.1002/maco.201307422 ↗