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
Microstructure Evaluation and Wear-Resistant Properties of Ti-alloyed Hypereutectic High Chromium Cast Iron
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

High chromium cast iron (HCCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in industry. The mechanical properties of HCCI mainly depend on type, size, number, morphology of hard carbides and the matrix structure (γ or α). The hypereutectic HCCI with large volume fractions of hard carbides is preferred to apply in wear applications. However, the coarser and larger primary M7C3 carbides will be precipitated during the solidification of the hypereutectic alloy and these will have a negative influence on the wear resistance.

In this thesis, the Ti-alloyed hypereutectic HCCI with a main composition of Fe-17mass%Cr-4mass%C is studied based on the experimental results and calculation results. The type, size distribution, composition and morphology of hard carbides and martensite units are discussed quantitatively. For a as-cast condition, a 11.2μm border size is suggested to classify the primary M7C3 carbides and eutectic M7C3 carbides. Thereafter, the change of the solidification structure and especially the refinement of carbides (M7C3 and TiC) size by changing the cooling rates and Ti addition is determined and discussed. Furthermore, the mechanical properties of hypereutectic HCCI related to the solidification structure are discussed.

Mechanical properties of HCCI can normally be improved by a heat treatment process. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM), in-situ observation by using Confocal Laser Scanning Microscope (CLSM), Transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). Especially for the matrix structure and secondary M7C3 carbides, EBSD and CLSM are useful tools to classify the fcc (γ) and bcc (α) phases and to study the dynamic behavior of secondary M7C3 carbides. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI.

Finally, the maximum carbides size is estimated by using statistics of extreme values (SEV) method in order to complete the size distribution results. Meanwhile, the characteristic of different carbides types will be summarized and classified based on the shape factor. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 76 p.
Keyword [en]
High Chromium Cast Iron, cooling rate, Ti addition, M7C3, TiC, carbides size distributions, volume fraction, heat treatment, microstructure, mechanical properties, wear resistance, statistics of extreme values (SEV), maximum carbides size.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-128532ISBN: 978-91-7501-842-3 (print)OAI: oai:DiVA.org:kth-128532DiVA: diva2:647897
Public defence
2013-09-27, B1, Brinellvägen 23, Kungliga Tekniska Högskolan, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130913

Available from: 2013-09-13 Created: 2013-09-12 Last updated: 2013-09-13Bibliographically approved
List of papers
1. Effect of cooling rate and Ti addition on the microstructure and mechanical properties in as-cast condition of hypereutectic high chromium cast irons
Open this publication in new window or tab >>Effect of cooling rate and Ti addition on the microstructure and mechanical properties in as-cast condition of hypereutectic high chromium cast irons
Show others...
2012 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 12, 2210-2219 p.Article in journal (Refereed) Published
Abstract [en]

The effect of cooling rate and Ti additions on the mechanical properties and carbides characteristics such as morphology, size distribution and composition was studied in high-chromium cast irons containing Fe-17 mass%Cr-4 mass%C. Based on the size distribution, composition and morphology, M 7C3 type carbides were roughly classified into "primary M7C3 carbides" and "eutectic M7C3 carbides" with a 11.2μ m border size. Thereafter, the change of the solidification structure and especially the refinement of carbides size were determined. It was found that both the size and number values should be summarized systematically for primary M 7C3 carbides and eutectic M7C3 carbides, respectively. Also, TiC carbides with a high formation temperature can not only act as a nuclei of M7C3 carbides, but they also contain a Ti(C, N) core. In the as-cast condition, the bulk hardness of the cast irons increases with an increased Ti content. In addition, the wear loss increases with an increased Ti content. Neither the bulk hardness nor the wear loss did change too much with an increased cooling rate.

Keyword
Carbides size distributions, Cooling rate, High chromium cast irons, M7C3, Ti addition, TiC
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-106214 (URN)10.2355/isijinternational.52.2210 (DOI)000312968000014 ()2-s2.0-84871814381 (Scopus ID)
Note

QC 20130118. Updated from accepted to published.

Available from: 2012-11-30 Created: 2012-11-30 Last updated: 2017-12-07Bibliographically approved
2. Solidification and phase transformations of Ti-added hypereutectic high chromium cast irons
Open this publication in new window or tab >>Solidification and phase transformations of Ti-added hypereutectic high chromium cast irons
Show others...
2012 (English)In: 1st International Conference on Ingot Casting, Rolling and Forging, 2012Conference paper, Published paper (Refereed)
Keyword
High chromium cast irons, solidification path, carbide precipitation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-128550 (URN)
Conference
1st International Conference on Ingot Casting, Rolling and Forging, 2012 Aachen, Germany
Note

QC 20130913

Available from: 2013-09-13 Created: 2013-09-13 Last updated: 2013-09-13Bibliographically approved
3. Effect of heat treatment on microstructure and mechanical properties of Ti-alloyed hypereutectic high chromium cast iron
Open this publication in new window or tab >>Effect of heat treatment on microstructure and mechanical properties of Ti-alloyed hypereutectic high chromium cast iron
Show others...
2012 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 12, 2288-2294 p.Article in journal (Refereed) Published
Abstract [en]

The effect of heat treatment on the microstructure and mechanical properties of Ti-alloyed hypereutectic High Chromium Cast Iron (HCCI) containing Fe-17 mass%Cr-4 mass%C-1.5 mass%Ti was investigated. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It was found that the number of fine secondary M7C3 carbides with a size below 1 μm increases with lower holding temperatures and shorter holding times during heat treatment. The number of coarse primary M7C 3 carbides with a size above 11.2 μm increases with increasing holding temperatures and longer holding times. In addition, the number of TiC carbides increases with increasing holding times, and martensite units are more refined at longer holding times and lower holding temperatures, respectively. Moreover, the volume fraction of martensite increases with increased holding times. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI.

Keyword
Heat treatment, High Chromium Cast Iron, Mechanical properties, Microstructure, Particle size distribution, Wear resistance
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-106215 (URN)10.2355/isijinternational.52.2288 (DOI)000312968000025 ()2-s2.0-84871766093 (Scopus ID)
Note

QC 20130116. Updated from accepted to published.

Available from: 2012-11-30 Created: 2012-11-30 Last updated: 2017-12-07Bibliographically approved
4. Dynamic Precipitation Behavior of Secondary M7C3 Carbides in Ti-alloyed High Chromium Cast Iron
Open this publication in new window or tab >>Dynamic Precipitation Behavior of Secondary M7C3 Carbides in Ti-alloyed High Chromium Cast Iron
Show others...
2013 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 7, 1237-1244 p.Article in journal (Refereed) Published
Abstract [en]

In-situ observations on the dynamic precipitation behavior of secondary carbides in Ti-alloyed High Chromium Cast Iron (HCCI) were performed by using a Confocal Laser Scanning Microscope (CLSM). Moreover, the detailed characterization of the microstructure before and after heat treatment was performed by using scanning electron microscopy (SEM). The secondary carbides, which precipitate from the matrix during heat treatment, were identified as M7C3 type carbides by using transmission electron microscopy (TEM). The number, size and volume of secondary carbides during heating, holding and cooling process were quantitatively evaluated based on the in-situ observation and SEM results. It was found that ferrite (alpha) and secondary carbides start to precipitate from the matrix at around 575 degrees C and 840 degrees C, respectively, during the heating process. In addition, the in-situ results showed that the number of secondary carbides increase with an increased heating temperature and time. Moreover, it was found that the size of these secondary carbides increase at higher temperatures and longer holding times. However, the number of secondary carbides increased with a decreased temperature. Finally, it was found that the volume fraction (similar to 5%) of secondary carbides was not changed to a large extent for the different heat treatment conditions being investigated.

Keyword
in-situ observation, CLSM, high chromium cast iron, secondary carbides, precipitation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-126904 (URN)10.2355/isijinternational.53.1237 (DOI)000322208600019 ()2-s2.0-84883239697 (Scopus ID)
Note

QC 20130826

Available from: 2013-08-26 Created: 2013-08-22 Last updated: 2017-12-06Bibliographically approved
5. Estimation of the Maximum Carbide Size in a Hypereutectic High Chromium Cast Iron Alloyed with Titanium
Open this publication in new window or tab >>Estimation of the Maximum Carbide Size in a Hypereutectic High Chromium Cast Iron Alloyed with Titanium
2013 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 12, 2176-2183 p.Article in journal (Refereed) Published
Abstract [en]

In this study, in order to obtain complete size distribution results, the maximum carbide size in a Fe-17 mass% Cr-4 mass% C hypereutectic High Chromium Cast Iron (HCCI) produced with different cooling conditions, titanium additions and heat treatment conditions was determined by using the statistics of extreme values (SEV) method. In addition, the shape factor, circularity, was estimated in order to classify the type of carbides (primary M7C3 carbides, TiC carbides and secondary M7C3 carbides). Compared to the smaller size carbides, such as TiC carbides and secondary M7C3 carbides, it was found that the slope of the extreme value distribution (EVD) regression lines is lower for the large sized carbides such as primary M7C3 carbides than for the smaller carbides. Moreover, it was found that the circularity value for the larger size carbides is higher than for the smaller carbides. Furthermore, the estimated and observed maximum carbide sizes were compared with each other for all carbide types. The characteristic of the different carbide types are summarized and classified based on the shape factor. Finally, the relationship between the carbide size distribution including the maximum carbides size and mechanical properties is discussed based on the combination of a size distribution analysis and a maximum size analysis.

Keyword
maximum size, carbides, statistics of extreme values (SEV), extreme value distribution (EVD), HCCI
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-128551 (URN)10.2355/isijinternational.53.2176 (DOI)000328928000020 ()2-s2.0-84893239521 (Scopus ID)
Note

QC 20140124. Updated from accepted to published.

Available from: 2013-09-13 Created: 2013-09-13 Last updated: 2017-12-06Bibliographically approved

Open Access in DiVA

Microstructure Evaluation and Wear-Resistant Properties of Ti-alloyed Hypereutectic High Chromium Cast Iron(5224 kB)727 downloads
File information
File name FULLTEXT01.pdfFile size 5224 kBChecksum SHA-512
f0e07b1d73b4ee50f94cc142b24fcb87f1627739319658689a72edf31d71c61f28ebbf641942e92c6087656aa69bacb0c3952d8832d94b8e9be0128ac39b2690
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Liu, Qiang
By organisation
Applied Process Metallurgy
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 727 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: 400 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