TY - JOUR
T1 - Design of high-strength and damage-resistant carbide-free fine bainitic steels for railway crossing applications
AU - Kumar, A.
AU - Makineni, S. K.
AU - Dutta, A.
AU - Goulas, C.
AU - Steenbergen, M.
AU - Petrov, R. H.
AU - Sietsma, J.
N1 - Funding Information:
This Research was carried out under project number F91.5.12475b in the framework of the partnership program of the Materials innovation institute M2i (www.m2i.nl) and the foundation for fundamental research on matter (FOM) (www.fom.nl), which is part of the Netherlands organisation for scientific research (www.nwo.nl). Authors would like thank Dr. M.G. Mecozzi and Prof. M.J. Santofimia, Delft university of technology, for fruitful discussion about the work and also to Mr. A.M. Ravi, Delft university of technology, for useful discussions during this research. We would like to thank ProRail for its financial support.
Funding Information:
This Research was carried out under project number F91.5.12475b in the framework of the partnership program of the Materials innovation institute M2i ( www.m2i.nl ) and the foundation for fundamental research on matter (FOM) ( www.fom.nl ), which is part of the Netherlands organisation for scientific research ( www.nwo.nl ). Authors would like thank Dr. M.G. Mecozzi and Prof. M.J. Santofimia, Delft university of technology, for fruitful discussion about the work and also to Mr. A.M. Ravi, Delft university of technology, for useful discussions during this research. We would like to thank ProRail for its financial support.
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/6/24
Y1 - 2019/6/24
N2 - A novel high-strength steel design is proposed, with a fine bainitic microstructure free from inter-lath carbides, for railway crossings applications. The design is based on the phase transformation theory and avoids microstructural constituents like martensite, cementite and large blocky retained austenite islands in the microstructure which are considered to be responsible for strain partitioning and damage initiation. The designed steel consists of fine bainitic ferrite, thin film austenite and a minor fraction of blocky austenite which contribute to its high strength, appreciable toughness and damage resistance. Atom probe tomography and dilatometry results are used to study the deviation of carbon partitioning in retained austenite and bainitic ferrite fractions from the T0/T0 ʹ predictions. A high carbon concentration of 7.9 at.% (1.8 wt%) was measured in thin film austenite, which governs its mechanical stability. Various strengthening mechanisms such as effect of grain size, nano-sized cementite precipitation and Cottrell atmosphere at dislocations within bainitic ferrite are discussed. Mechanical properties of the designed steel are found to be superior to those of conventional steels used in railway crossings. The designed steel also offers controlled crack growth under the impact fatigue, which is the main cause of failure in crossings. In-situ testing using micro digital image correlation is carried out to study the micromechanical response of the designed microstructure. The results show uniform strain distribution with low standard deviation of 1.5% from the mean local strain value of 7.7% at 8% global strain.
AB - A novel high-strength steel design is proposed, with a fine bainitic microstructure free from inter-lath carbides, for railway crossings applications. The design is based on the phase transformation theory and avoids microstructural constituents like martensite, cementite and large blocky retained austenite islands in the microstructure which are considered to be responsible for strain partitioning and damage initiation. The designed steel consists of fine bainitic ferrite, thin film austenite and a minor fraction of blocky austenite which contribute to its high strength, appreciable toughness and damage resistance. Atom probe tomography and dilatometry results are used to study the deviation of carbon partitioning in retained austenite and bainitic ferrite fractions from the T0/T0 ʹ predictions. A high carbon concentration of 7.9 at.% (1.8 wt%) was measured in thin film austenite, which governs its mechanical stability. Various strengthening mechanisms such as effect of grain size, nano-sized cementite precipitation and Cottrell atmosphere at dislocations within bainitic ferrite are discussed. Mechanical properties of the designed steel are found to be superior to those of conventional steels used in railway crossings. The designed steel also offers controlled crack growth under the impact fatigue, which is the main cause of failure in crossings. In-situ testing using micro digital image correlation is carried out to study the micromechanical response of the designed microstructure. The results show uniform strain distribution with low standard deviation of 1.5% from the mean local strain value of 7.7% at 8% global strain.
KW - Atom probe tomography (APT)
KW - Carbide-free bainitic steel
KW - Mechanical properties
KW - Rail crossing
KW - Strain partitioning
KW - Transmission electron microscopy (TEM)
UR - https://www.scopus.com/pages/publications/85065626843
U2 - 10.1016/j.msea.2019.05.043
DO - 10.1016/j.msea.2019.05.043
M3 - Article
AN - SCOPUS:85065626843
SN - 0921-5093
VL - 759
SP - 210
EP - 223
JO - Materials Science & Engineering A
JF - Materials Science & Engineering A
ER -