Control of Wear-Resistance Properties in Ti-added Hypereutectic High Chromium Cast Iron
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
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 wear resistance and 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-added hypereutectic HCCI with a main composition of Fe-17mass%Cr-4mass%C is quantitatively studied based on the type, size distribution, composition and morphology of hard carbides and martensite units. 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) and electron backscattered diffraction (EBSD). Especially for the matrix structure, EBSD is a useful tool to classify the fcc (γ) and bcc (α) phases. 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.
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 44 p.
High Chromium Cast Iron, cooling rate, Ti addition, M7C3, TiC, carbides size distributions, volume fraction, heat treatment, microstructure, mechanical properties, wear resistance
Metallurgy and Metallic Materials
IdentifiersURN: urn:nbn:se:kth:diva-105854ISBN: 978-91-7501-581-1OAI: oai:DiVA.org:kth-105854DiVA: diva2:572548
2012-12-14, N111, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Tinoco, José, Dr.
Jönsson, Pär, ProfessorNakajima, Keiji, Professor
QC 201211302012-11-302012-11-282012-11-30Bibliographically approved
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