Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method
University West, Department of Engineering Science, Division of Welding Technology. Innovatum AB., Trollhättan, Trollhättan, Sweden. (PTW)ORCID iD: 0000-0001-6242-3517
University West, Department of Engineering Science, Division of Welding Technology. (PTW)ORCID iD: 0000-0001-8822-2705
KTH Royal Institute of Technology, Department of Chemical Science and Engineering, Division of Surface and Corrosion Science, Stockholm, Sweden, Department of Corrosion in Energy and Processing Industry, Swerea KIMAB AB, P.O. Box 7047, Kista, Sweden.
The University of Manchester, School of Materials, Manchester, United Kingdom.
Show others and affiliations
2018 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, p. 390-400Article in journal (Refereed) Published
Abstract [en]

A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures. © 2018 The Authors

Place, publisher, year, edition, pages
Elsevier Inc. , 2018. Vol. 139, p. 390-400
Keywords [en]
Austenite; Chromium compounds; Cold rolling; Embrittlement; Hardness; Heat treatment; Microstructure; Nitrogen; Nitrogen compounds; Phase equilibria; Schematic diagrams; Stainless steel, Chi phase; Functionally graded microstructures; Nitrogen loss; R phase; Sigma phase, Temperature
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-12235DOI: 10.1016/j.matchar.2018.03.024ISI: 000431469300042Scopus ID: 2-s2.0-85044113030OAI: oai:DiVA.org:hv-12235DiVA, id: diva2:1194729
Note

Available online 19 March 2018

Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2018-08-30Bibliographically approved
In thesis
1. Super duplex stainless steels: Microstructure and propertiesof physically simulated base and weld metal
Open this publication in new window or tab >>Super duplex stainless steels: Microstructure and propertiesof physically simulated base and weld metal
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

High-temperature processing and application of super duplex stainless steel(SDSS) are associated with the risk of changes in the ferrite/austenite balance and precipitation of secondary phases. This study was therefore aimed at improving knowledge about effects of thermal cycles on the microstructure and properties of SDSS base and weld metal. Controlled and repeatable thermal cycles were physically simulated using the innovative multiple TIG reheating/remelting and the arc heat treatment techniques. In the first technique, one to four autogenous TIG-remelting passes were applied. During arc heat treatment, a stationary arc was applied on a disc mounted on a water-cooled chamber thereby subjecting the material to a steady state temperature gradient from 0.5 minute to 600 minutes. Microstructures and properties were assessed and linked to thermal history through thermal cycle analysis, thermodynamic calculations and temperature field modelling, Remelting studies showed that nitrogen loss from the melt pool was a function of arc energy and initial nitrogen content and could cause highly ferritic microstructures. Heat affected zones were sensitized by nitride formation next to the fusion boundary and sigma phase precipitation in regions subjected to peak temperatures of 828-1028°C. Accumulated time in the critical temperature range, peak temperature and the number of thermal cycles are the most relevant criteria when evaluating the risk of sigma phase precipitation. Arc heat treatment produced graded microstructures in SDSS base and weld metal with the formation of a ferritic region at high temperature due to solid-state nitrogen loss, precipitation of sigma, chi, nitrides, and R-phase with different morphologies at 550-1010°C and spinodal decomposition below 500°C. This caused sensitization and/or increased hardness and embrittlement. Results were summarized as time-temperature-precipitation and properties diagrams for base and weld metal together with guidelines for processing and welding of SDSS.

Place, publisher, year, edition, pages
Trollhättan: University West, 2018. p. 102
Series
PhD Thesis: University West ; 24
Keywords
Super duplex stainless steel; weld metal; physical simulation; phase balance; precipitation; secondary phases; corrosion; nitrogen loss; arc heat treatment; production technology
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-12850 (URN)978-91-87531-98-9 (ISBN)978-91-87531-97-2 (ISBN)
Public defence
2018-09-28, F127, lhättan, 09:00 (English)
Supervisors
Available from: 2018-09-04 Created: 2018-08-30

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Hosseini, VahidKarlsson, LeifWessman, Sten

Search in DiVA

By author/editor
Hosseini, VahidKarlsson, LeifWessman, Sten
By organisation
Division of Welding Technology
In the same journal
Materials Characterization
Manufacturing, Surface and Joining Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 74 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf