Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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
Influence of carbides and nitrides on corrosion initiation of advanced alloys: A local probing study
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Advanced alloys often present precipitated carbides and nitrides in their microstructure following exposure to elevated temperatures. These secondary phases are usually undesirable, because potentially deleterious for the corrosion and mechanical performances of the material. Carbides and nitrides are enriched in key alloying elements that are subtracted from their surrounding matrix areas, creating alloying element depleted zones, which might become initial sites for corrosion initiation. In this study, the influence of micro- and nano-sized precipitated carbides and nitrides on the corrosion initiation of biomedical CoCrMo alloys and duplex stainless steels has been investigated at microscopic scale, by using a combination of local probing techniques. The microstructures of the alloys were first characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and magnetic force microscopy (MFM). The Volta potential mapping of carbides and nitrides revealed their higher nobility compared to the matrix, and particularly compared to their surrounding areas, suggesting the occurrence of some alloying element depletion in the latter locations, which may lead to a higher susceptibility for corrosion initiation. In-situ electrochemical AFM studies performed at room temperature showed passive behavior for large potential ranges for both alloy families, despite the presence of the precipitated carbides or nitrides. At high anodic applied potential, at which transpassive dissolution occurs, preferential dissolution started from the areas adjacent to the precipitated carbides and nitrides, in accordance with the Volta potential results. Thus, the presence of carbides and nitrides doesn’t largely affect the corrosion resistance of the tested advanced alloys, which maintain passive behavior when exposed to highly concentrated chloride solutions at room temperature with no applied potential. The effect of nitrides on the corrosion initiation of duplex stainless steels was investigated also at temperatures above the critical pitting temperature (CPT). Depending on the type, distribution and size range of the precipitated nitrides different corrosion behaviors were observed. Intragranular (quenched-in) nano-sized nitrides (ca. 50-100 nm) finely dispersed in the ferrite grains have a minor influence on the corrosion resistance of the material at temperatures above the CPT, while larger intergranular (isothermal) nitrides (ca. 80-250 nm) precipitated along the phase boundaries cause a detrimental reduction of the corrosion resistance of the material, in particular of the austenite phase

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xiv, 59 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:34
Keyword [en]
carbides, nitrides, microstructure, CoCrMo alloys, duplex stainless steels, localized corrosion, transpassive dissoluti on, elemental depletion, AFM, TEM, SEM.
National Category
Corrosion Engineering
Identifiers
URN: urn:nbn:se:kth:diva-129356ISBN: 978-91-7501-841-6 (print)OAI: oai:DiVA.org:kth-129356DiVA: diva2:651807
Public defence
2013-10-18, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130927

Available from: 2013-09-27 Created: 2013-09-27 Last updated: 2013-09-27Bibliographically approved
List of papers
1. Influence of metal carbides on dissolution behavior of biomedical CoCrMo alloy: SEM, TEM and AFM studies
Open this publication in new window or tab >>Influence of metal carbides on dissolution behavior of biomedical CoCrMo alloy: SEM, TEM and AFM studies
Show others...
2011 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, no 25, 9413-9419 p.Article in journal (Refereed) Published
Abstract [en]

The influence of precipitate carbides on dissolution tendency and behavior of a biomedical CoCrMo alloy was investigated at microscopic scale. SEM/EDS, TEM/EDS and XRD were performed to characterize crystallographic structure and composition of different precipitate carbides. Scanning Kelvin probe force microscope (SKPFM) was used to evaluate relative nobility of the carbides. In addition to polarization curves, in situ electrochemical AFM (EC-AFM) measurements were performed to investigate the effect of the carbides on local dissolution processes. SEM/EDS, TEM/EDS and XRD characterizations showed non-uniform structure and composition of Cr and Mo carbides. SKPFM analysis suggested the carbide boundaries as preferential sites for corrosion/dissolution process. Cyclic polarization curves of the alloy in phosphate-buffered saline (PBS) solution showed a large current density increase above a certain potential, but only a small hysteresis loop during reverse scan. No noticeable pitting corrosion was observed by SEM after the experiments. In situ AFM images of the sample in PBS showed a stable surface at potentials in the passive region and around the potential corresponding to the current increase and slight etching-like dissolution around the carbides at higher potentials. Carbide boundaries are preferential sites for metal dissolution and carbides with non-uniform composition might exhibit different dissolution rates.

Keyword
CoCrMo alloy, Carbides, TEM, SKPFM, In situ EC-AFM
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-47972 (URN)10.1016/j.electacta.2011.08.028 (DOI)000295997000057 ()2-s2.0-80053279459 (Scopus ID)
Note
QC 20111117Available from: 2011-11-17 Created: 2011-11-15 Last updated: 2017-12-08Bibliographically approved
2. Influence of Grain Boundaries on Dissolution Behavior of a Biomedical CoCrMo Alloy: In-Situ Electrochemical-Optical, AFM and SEM/TEM Studies
Open this publication in new window or tab >>Influence of Grain Boundaries on Dissolution Behavior of a Biomedical CoCrMo Alloy: In-Situ Electrochemical-Optical, AFM and SEM/TEM Studies
Show others...
2012 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, no 9, C422-C427 p.Article in journal (Refereed) Published
Abstract [en]

In this study, preferential sites for metal dissolution during anodic polarization were investigated for a biomedical CoCrMo alloy. As-cast and heat treated materials were compared through a combination of complementary techniques. Scanning Kelvin probe force microscopy mapping suggested the matrix areas adjacent to the carbides to be preferential sites for metal dissolution. By means of in situ electrochemical-optical microscopy it was observed that localized dissolution initiated from the matrix areas adjacent to carbides and grain boundaries in both materials at high anodic potential. By using scanning electron microscopy and transmission electron microscopy/energy dispersive spectroscopy analysis, submicron-sized carbides were found along the grain boundaries, and significant Cr depletion was detected across the grain boundaries for both materials, providing an explanation for the initiation of metal dissolution. A slightly higher metal dissolution was observed for the as-cast sample at high anodic potential, probably due to a more heterogeneous microstructure.

Keyword
Probe Force Microscopy, Duplex Stainless-Steel, Cr-Mo Alloy, Corrosion, Implants, Mechanisms, Particles, Depletion, Carbides, Fatigue
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-104283 (URN)10.1149/2.056209jes (DOI)000309104400031 ()2-s2.0-84875539098 (Scopus ID)
Note

QC 20121109

Available from: 2012-11-09 Created: 2012-10-31 Last updated: 2017-12-07Bibliographically approved
3. Nature of current increase for a CoCrMo alloy: "transpassive" dissolution vs. water oxidation
Open this publication in new window or tab >>Nature of current increase for a CoCrMo alloy: "transpassive" dissolution vs. water oxidation
2013 (English)In: International Journal of Electrochemical Science, ISSN 1452-3981, E-ISSN 1452-3981, Vol. 8, no 10, 11791-11804 p.Article in journal (Refereed) Published
Abstract [en]

The “transpassive” behavior of a CoCrMo alloy has been investigated to clarify the nature of the current increase at high anodic potential (0.5-0.7 VAg/AgCl). The total amount of released metal ions was determined after the potentiostatic measurements. According to the calculation through Faradays’ law, the metal dissolution only contributes to part of the total current recorded. Electrochemical AFM mapping did not show pronounced topography changes at 0.65 VAg/AgCl, while light optical microscopy observation revealed fast evolution of oxygen bubbles. Evidently water oxidation is another important process largely contributing to the current increase at the high potential.

Keyword
CoCrMo alloy, transpassivity, metal dissolution, water oxidation, AFM
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-129348 (URN)000326501800012 ()2-s2.0-84886479232 (Scopus ID)
Note

QC 20131203

Available from: 2013-09-27 Created: 2013-09-27 Last updated: 2017-12-06Bibliographically approved
4. Study of corrosion behavior of a 22% Cr duplex stainless steel: influence of nano-sized chromium nitrides and exposure temperature
Open this publication in new window or tab >>Study of corrosion behavior of a 22% Cr duplex stainless steel: influence of nano-sized chromium nitrides and exposure temperature
2013 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 113, 280-289 p.Article in journal (Refereed) Published
Abstract [en]

Chromium nitrides may precipitate in duplex stainless steels during processing and their influence on the corrosion behavior is of great importance for the steel performance. In this study, the influence of nano-sized quenched-in chromium nitrides on the corrosion behavior of a heat treated 2205 duplex stainless steel was investigated at room temperature and 50 °C (just above critical pitting temperature). The microstructure was characterized by SEM/EDS and AFM analyses, and quenched-in nitrides precipitated in the ferrite phase were identified by TEM analysis. Volta potential mapping at room temperature suggests lower relative nobility of the ferrite matrix. Electrochemical polarization and in-situ AFM measurements in 1 M NaCl solution at room temperature show a passive behavior of the steel despite the presence of the quenched-in nitrides in the ferrite phase, and preferential dissolution of ferrite phase occurred only at transpassive conditions. At 50 °C, selective dissolution of the austenite phase was observed, while the ferrite phase with the quenched-in nitrides remained to be stable. It can be concluded that the finely dispersed quenched-in nitrides do not cause localized corrosion, whereas the exposure temperature has a strong influence on the corrosion behavior of the duplex stainless steel.

Keyword
Duplex stainless steel, quenched-in nitrides, exp osure temperature, localized corrosion, AFM
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-129350 (URN)10.1016/j.electacta.2013.09.056 (DOI)000330491500038 ()2-s2.0-84886128481 (Scopus ID)
Note

QC 20140122

Available from: 2013-09-27 Created: 2013-09-27 Last updated: 2017-12-06Bibliographically approved
5. Study of Corrosion Behavior of a 2507 Super Duplex Stainless Steel: Influence of Quenched-in and Isothermal Nitrides
Open this publication in new window or tab >>Study of Corrosion Behavior of a 2507 Super Duplex Stainless Steel: Influence of Quenched-in and Isothermal Nitrides
2014 (English)In: International Journal of Electrochemical Science, ISSN 1452-3981, E-ISSN 1452-3981, Vol. 9, no 1, 61-80 p.Article in journal (Refereed) Published
Abstract [en]

Precipitation of different types of chromium nitrides may occur during processing of super duplex stainless steels, affecting the properties of the material. In this study the influence of quenched-in (size range ca. 50-100 nm) and isothermal (size range ca. 80-250 nm) types of nitrides on the corrosion behavior of a 2507 super duplex stainless steel has been investigated at room temperature and at 90 degrees C (above the critical pitting temperature) in 1 M NaCl solution. The microstructure has been characterized by scanning electron microscopy and magnetic force microscopy. The isothermal nitrides exhibit a higher Volta potential compared to the matrix, but such difference could not be observed for the quenched-in nitrides. In-situ electrochemical AFM measurements at room temperature show stable surfaces for a wide range of applied potentials despite the presence of either type of nitrides. In the transpassive region isothermal nitrides appear to be slightly more deleterious than quenched-in nitrides. At 90 degrees C isothermal nitrides largely reduce the corrosion resistance of the austenite phase, while the quenched-in nitrides reduce the corrosion resistance of the material to a much lesser extent. The size difference between isothermal and quenched-in chromium nitrides may be crucial, in particular above the critical pitting temperature.

Keyword
Duplex stainless steel, nitrides, exposure tempera ture, atomic force microscopy, corrosion
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-129354 (URN)000328931100006 ()2-s2.0-84891050891 (Scopus ID)
Note

QC 20140123. Updated from accepted to published.

Available from: 2013-09-27 Created: 2013-09-27 Last updated: 2017-12-06Bibliographically approved

Open Access in DiVA

Thesis(8948 kB)567 downloads
File information
File name FULLTEXT01.pdfFile size 8948 kBChecksum SHA-512
ccf80f4767615061d5cf7e00f23fe1aa10bf7290f31e8ec98f6401b3527375dafc9ec9c15cf31c4cb93ade8032ce33260d6de219304a1f286bdc1cadaf79131f
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Bettini, Eleonora
By organisation
Surface and Corrosion Science
Corrosion Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 567 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 570 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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