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4 results on '"A Stainless steel"'

1. The Effect of Sodium Hydroxide on Niobium Carbide Precipitates in Thermally Sensitised 20Cr-25Ni-Nb Austenitic Stainless Steel

Author

Choen May Chan, Thomas L Martin, Ronald N. Clark, Dirk Engelberg, Robert Burrows, W.S. Walters, and Geraint Williams

Subjects
Materials science, 020209 energy, General Chemical Engineering, C Inclusion, 02 engineering and technology, A Stainless steel, engineering.material, Electrochemistry, Corrosion, chemistry.chemical_compound, Corrosion inhibitor, B SEM, 0202 electrical engineering, electronic engineering, information engineering, Pitting corrosion, Dalton Nuclear Institute, General Materials Science, Austenitic stainless steel, B AFM, B Polarisation, Metallurgy, General Chemistry, C Alkaline corrosion, 021001 nanoscience & nanotechnology, Microstructure, ResearchInstitutes_Networks_Beacons/dalton_nuclear_institute, chemistry, Sodium hydroxide, engineering, B EIS, Niobium carbide, 0210 nano-technology, C Intergranular corrosion, C Pitting corrosion, SIMS
Abstract

Niobium-stabilised austenitic stainless steel (20Cr-25Ni-Nb) has been immersed in sodium hydroxide, which is used as a corrosion inhibitor. The work shows how NbC precipitates may be degraded by use of pH 13 NaOH. Initial electrochemical measurements indicate that there is no benefit to this pretreatment as regards long-term corrosion inhibition, and post corrosion imaging shows the initiation of pitting corrosion at Nb-rich precipitates still present in the microstructure.

Published
2020

2. The role of niobium carbides in the localised corrosion initiation of 20Cr-25Ni-Nb advanced gas-cooled reactor fuel cladding

Author

Ronald N. Clark, Tomas L. Martin, Geraint Williams, W.S. Walters, and Justin Searle

Subjects
Cladding (metalworking), Materials science, 020209 energy, General Chemical Engineering, Niobium, chemistry.chemical_element, C Inclusion, A Stainless steel, 02 engineering and technology, Carbide, Corrosion, chemistry.chemical_compound, B SEM, 0202 electrical engineering, electronic engineering, information engineering, General Materials Science, B AFM, Metallurgy, General Chemistry, 021001 nanoscience & nanotechnology, Anode, chemistry, Niobium carbide, Grain boundary, C Intergranular corrosion, C Pitting corrosion, 0210 nano-technology, Science, technology and society
Abstract

The role of niobium carbide (NbC) inclusions in directing the initiation of localised corrosion in sensitised 20Cr-25Ni-Nb stainless steel is investigated using a range of in-situ scanning techniques, allowing visualisation of corrosion behaviour over multiple length scales. Volta potential mapping shows NbC inclusions are up to 30 mV noble to the matrix, while chromium-depleted grain boundaries are up to 65 mV less noble. Corrosion initiation, shown by scanning vibrating electrode technique to comprise highly localised anode sites, is observed at grain boundaries, adjacent to the location of NbC inclusion clusters which remain unaffected by anodic dissolution of the surrounding matrix.

Published
2020

3. The effect of sodium hydroxide on niobium carbide precipitates in thermally sensitised 20Cr-25Ni-Nb austenitic stainless steel.

Author

Clark, Ronald N., Chan, C.M., Martin, Tomas L., Walters, W.S., Engelberg, Dirk, Burrows, Robert, and Williams, Geraint

Subjects
*AUSTENITIC stainless steel, *NIOBIUM compounds, *SODIUM hydroxide, *STAINLESS steel, *NIOBIUM, *PITTING corrosion, *CORROSION & anti-corrosives
Abstract

• Post corrosion imaging shows corrosion initiation at NbC inclusions. • Evidence that pH 13 NaOH pretreatment dissolves and degrades NbC inclusions. • In-situ time lapse microscopy technique tracks NbC modification by NaOH. • Pre-treatment indicates no benefit as regards long-term corrosion inhibition. Niobium-stabilised austenitic stainless steel (20Cr-25Ni-Nb) has been immersed in sodium hydroxide, which is used as a corrosion inhibitor. The work shows how NbC precipitates may be degraded by use of pH 13 NaOH. Initial electrochemical measurements indicate that there is no benefit to this pretreatment as regards long-term corrosion inhibition, and post corrosion imaging shows the initiation of pitting corrosion at Nb-rich precipitates still present in the microstructure. [ABSTRACT FROM AUTHOR]

Published
2020
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4. The role of niobium carbides in the localised corrosion initiation of 20Cr-25Ni-Nb advanced gas-cooled reactor fuel cladding.

Author

Clark, Ronald N., Searle, Justin, Martin, Tomas L., Walters, W.S., and Williams, Geraint

Subjects
*NUCLEAR fuels, *NIOBIUM, *NUCLEAR fuel claddings, *PITTING corrosion, *CARBIDES, *STAINLESS steel, *CRYSTAL grain boundaries
Abstract

• SKPFM highlights nobility of niobium carbides. • Evidence of intergranular pitting corrosion at niobium carbide inclusions. • EC-AFM provides evidence that intergranular pits form around inclusions. The role of niobium carbide (NbC) inclusions in directing the initiation of localised corrosion in sensitised 20Cr-25Ni-Nb stainless steel is investigated using a range of in-situ scanning techniques, allowing visualisation of corrosion behaviour over multiple length scales. Volta potential mapping shows NbC inclusions are up to 30 mV noble to the matrix, while chromium-depleted grain boundaries are up to 65 mV less noble. Corrosion initiation, shown by scanning vibrating electrode technique to comprise highly localised anode sites, is observed at grain boundaries, adjacent to the location of NbC inclusion clusters which remain unaffected by anodic dissolution of the surrounding matrix. [ABSTRACT FROM AUTHOR]

Published
2020
Full Text
View/download PDF

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