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
Development of a ferritic ductile cast iron for improved life in exhaust applications
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.ORCID iD: 0000-0001-5212-2227
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Due to coming emission legislations, the temperature is expected to increase in heavy-duty diesel engines, specifically in the hot-end of the exhaust system affecting components, such as exhaust- and turbo manifolds. Since the current material in the turbo manifold, a ductile cast iron named SiMo51, is operating close to its limits there is a need for material development in order to maintain a high durability of these components. When designing for increased life, many material properties need to be considered, for example, creep-, corrosion- and fatigue resistance. Among these, the present work focuses on the latter two up to 800°C improving the current material by additions of Cr, for corrosion resistance, and Ni, for mechanical properties. The results show improved high-temperature corrosion resistance in air from 0.5 and 1wt% Cr additions resulting in improved barrier layer at the oxide/metal interface. However, during oxidation in exhaust-gases, which is a much more demanding environment compared to air, such improvement could not be observed. Addition of 1wt% Ni was found to increase the fatigue life up to 250°C, resulting from solution strengthening of the ferritic matrix. However, Ni was also found to increase the oxidation rates, as no continuous SiO2-barrier layers were formed in the presence of Ni. Since none of the tested alloys showed improved material properties in exhaust gases at high temperature, it is suggested that the way of improving performance of exhaust manifolds is to move towards austenitic ductile cast irons or cast stainless steels. One alloy showing good high-temperature oxidation properties in exhaust atmospheres is an austenitic cast stainless steel named HK30. This alloy formed adherent oxide scales during oxidation at 900°C in gas mixtures of 5%O2-10%H2O-85%N2 and 5%CO2-10%H2O-85%N2 and in air. In the two latter atmospheres, compact scales of (Cr, Mn)-spinel and Cr2O3 were formed whereas in the atmosphere containing 5%O2 and 10%H2O, the scales were more porous due to increased Fe-oxide formation. Despite the formation of a protective, i.e. compact and adherent, oxide scale on HK30, exposure to exhaust-gas condensate showed a detrimental effect in form of oxide spallation and metal release. Thus, proving the importance of taking exhaust-gas condensation, which may occur during cold-start or upon cooling of the engine, into account when selecting a new material for exhaust manifolds. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 51 p.
Keyword [en]
Material development, SiMo51, HK30, exhaust manifolds, high-temperature corrosion, high-temperature low-cycle fatigue
National Category
Metallurgy and Metallic Materials Corrosion Engineering
Identifiers
URN: urn:nbn:se:kth:diva-122006ISBN: 978-91-7501-711-2 (print)OAI: oai:DiVA.org:kth-122006DiVA: diva2:620166
Presentation
2013-05-24, Marcus Wallenberghallen, Scania, Nyköpingsvägen 33, Södertälje, 13:00 (English)
Opponent
Supervisors
Funder
Vinnova, 2009-01433
Note

QC 20130508

Available from: 2013-05-08 Created: 2013-05-07 Last updated: 2013-11-15Bibliographically approved
List of papers
1. Influence of Cr and Ni on High-Temperature Corrosion Behavior of Ferritic Ductile Cast Iron in Air and Exhaust Gases
Open this publication in new window or tab >>Influence of Cr and Ni on High-Temperature Corrosion Behavior of Ferritic Ductile Cast Iron in Air and Exhaust Gases
2013 (English)In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 80, no 5-6, 455-466 p.Article in journal (Refereed) Published
Abstract [en]

Due to an expected temperature increase of the exhaust gases in heavy-duty engines in order to meet future emission regulations, there is a need to develop materials that can operate at higher temperatures. The exhaust manifold in the hot end of the exhaust system is specifically affected since the most common material today, SiMo51, is already operating close to its limits. Accordingly, the effects of Cr and Ni-additions on the high-temperature corrosion resistance of this material in air and exhaust gases were examined. It was found that the addition of 0.5 and 1 wt% Cr improved the oxidation resistance in air at 700 and 800 A degrees C by the formation of an SiO2 barrier layer as well as a Cr-oxide at the oxide/metal interface. However, no Cr-oxide was detected after exposure to exhaust gases, probably due to a water vapor-assisted evaporation of Cr from the oxide. The addition of 1 wt% Ni resulted in a deteriorated SiO2 barrier layer and reduced oxidation resistance.

Keyword
Ferritic ductile cast iron, Water-assisted evaporation, Exhaust manifold
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-122014 (URN)10.1007/s11085-013-9389-8 (DOI)000327081200002 ()2-s2.0-84890119737 (Scopus ID)
Funder
Vinnova
Note

QC 20131217

Available from: 2013-05-08 Created: 2013-05-08 Last updated: 2017-12-06Bibliographically approved
2. The influence of Cr and Ni on the high-temperature low-cycle fatigue behavior of a ferritic cast ductile iron
Open this publication in new window or tab >>The influence of Cr and Ni on the high-temperature low-cycle fatigue behavior of a ferritic cast ductile iron
2012 (English)In: Conference proceeding for 7th International Conference on Low Cycle Fatigue, 2012Conference paper, Published paper (Refereed)
Abstract [en]

 The current material in exhaust manifolds for heavy-duty diesel engines: a Si- and Mo-alloyed, ferritic ductile cast iron, named SiMo51, is operating close to its limits and improvements are needed. Thus, in the present study, the effects on mechanical properties of adding Cr and Ni to SiMo51 has been investigated with focus on low-cycle fatigue behavior in air, at temperatures up to 700°C. Both additions improve fatigue life but reduce elongation. Adding 1wt% Ni improves fatigue life up to 250°C whereas adding 0.5wt% Cr improves fatigue life at room temperature, only.

Keyword
High-temperature LCF, ductile cast iron, SiMo51, exhaust manifolds, fatigue life, Cr, Ni
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-122015 (URN)
Conference
7th International Conference on Low Cycle Fatigue, Aachen Sep 2012
Note

QC 20130508

Available from: 2013-05-08 Created: 2013-05-08 Last updated: 2013-11-15Bibliographically approved
3. An electrochemical impedance spectroscopy study on the effect of condensate on oxides formed on a 25Cr/20Ni cast stainless steel in exhaust environments
Open this publication in new window or tab >>An electrochemical impedance spectroscopy study on the effect of condensate on oxides formed on a 25Cr/20Ni cast stainless steel in exhaust environments
(English)Manuscript (preprint) (Other academic)
Abstract [en]

 Condensation of diesel exhaust gases inside an exhaust- or turbo manifold may occur during cold-start and cooling of an engine, resulting in acidic liquid covering the oxide surfaces inside the manifolds. In the present study, the interaction between a chloride-containing exhaust-gas condensate of pH 2.4 and oxide scales formed on a 25Cr/20Ni cast stainless steel in air and in two different exhaust environments, 10%H2O-5%O2-85%N2 and 10%H2O-5%CO2-85%N2, at 900°C has been examined by means of electrochemical impedance spectroscopy, EIS. Interpretation of impedance spectra was coupled to oxide scale structures, revealed by SEM, EDX, XRD and GDOES, and to metal release studies using ICP. It was observed that the acidic condensate caused oxide spallation, followed by corrosion of the underlying metal surface for all test samples. The metal release rate of the oxide scale and underlying alloy was found to decrease at longer immersion times (>1h), most likely due to precipitation of corrosion products on the surfaces. EIS combined with equivalent circuit fitting showed to be a useful technique in describing the electric properties of the oxide scales, suggesting oxidation in H2O/O2 to result in formation of oxide scales being more resistive compared to the other environments. This was coupled to higher thickness and higher defect density, which correlated well with oxide scale analysis.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-122016 (URN)
Note

QS 2013

Available from: 2013-05-08 Created: 2013-05-08 Last updated: 2013-11-15Bibliographically approved

Open Access in DiVA

Spikblad(11 kB)32 downloads
File information
File name SPIKBLAD01.pdfFile size 11 kBChecksum SHA-512
654b0535d2c1cc369000790f709774763626c749f604dc5d9d9b6f84194eb7545019350887f4dbac7948c95742a84f78e9c244c7eb276f72f4307a082b4c812a
Type spikbladMimetype application/pdf
Thesis(1495 kB)6917 downloads
File information
File name FULLTEXT02.pdfFile size 1495 kBChecksum SHA-512
fa3ae82f44f518ff0459142a9a9c1f1354168de3ce081da4add184bf65e1f3db7d0f7f4482f2fa432eda75c5664a8ae563da83a5d1dc38b9f410742a3a430c7b
Type fulltextMimetype application/pdf

Authority records BETA

Ekström, Madeleine

Search in DiVA

By author/editor
Ekström, Madeleine
By organisation
Mechanical Metallurgy
Metallurgy and Metallic MaterialsCorrosion Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 6917 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: 2903 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