Formation of Fine Structure of Differentially Hardened Rails

Gromov, V. Е.; Ivanov, Yu. F.; Морозов, К. В.; Алсараева, К. В.

doi:10.4028/www.scientific.net/amm.682.41

Cited by 4 publications

(7 citation statements)

References 3 publications

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“…Therefore, the morphology of bend extinction contours characterises the gradient of curvaturetorsion of material crystal lattice, the value of transverse size of contours -the amplitude of curvature-torsion of crystal lattice. The capacity of bend extinction contour (internal stress fields generated by this contour) is characterised by its transverse size -the less are the transverse sizes of contour the higher is amplitude of internal stress fields [1,22]. Using this character it can be noted that the stress fields of maximum amplitude are formed by interface particle/matrix, as shown is Figure 6(c,d).…”

Section: Resultsmentioning

confidence: 94%

“…The estimation of internal stress profile along the corresponding extinction contours requires determining the lattice curvature-torsion. For this purpose either the displacement rate of extinction contour under changes of goniometer slope angle or the width of extinction contour should be measured [1,26]. It has been established that with simultaneous use of both procedures the width of extinction contour in values of disorientations in hardened steels was around 1 degree [26].…”

Section: Resultsmentioning

confidence: 99%

“…where ∂ϕ is the change of orientation reflecting the planes of foils, and ∂ is the value of displacement of extinction contour. Testing assessments carried out on hardened steels as well as steels subjected to different degrees and types of deformation showed that reasonable assessments of value of internal stress fields could be done using the following relationship [1]…”

Section: Resultsmentioning

confidence: 99%

“…More than 50 indents were used to obtain the average hardness. The grains size was determined using the casual secant method which across over more than 50 grains for the calculation of average grain size [1]. The wear resistance was examined using a tribometer (Tribotechnic, made in France).…”

Section: Methodsmentioning

confidence: 99%

“…The increasing volume of freight, improving speed of train and simultaneous growing loading accelerate the wear of tread surface and failure of rails [1][2][3][4]. Wear is the main factor responsible for the rails traffic capacity and service life [3,4].…”

Section: Introductionmentioning

confidence: 99%

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Degradation of structure and properties of rail surface layer at long-term operation

Gromov

Ivanov

Qin

et al. 2017

Materials Science and Technology

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Abstract:The microstructure evolution and properties variation of the surface layer of rail steel after passed 500 and 1000 million tons of gross weight (MTGW) have been investigated.The wear rate increases to 3 and 3.4 times after passed 500 and 1000 MTGW, respectively.The corresponding friction coefficient decreases by 1.4 and 1.1 times. The cementite plates were destroyed and formed the cementite particles of around 10-50 nm in size after passed 500 MTGW. The early stage dynamical recrystallization was observed after passed 1000 MTGW. The mechanisms for these have been suggested. The large number of bend extinction contours is revealed in the surface layer. The internal stress field is evaluated.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Degradation of structure and properties of rail surface layer at long-term operation

Gromov

Ivanov

Qin

et al. 2017

Materials Science and Technology

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Evolution of structure of rail steel lamellar pearlite under compression deformation

Aksenova

Gromov

Ivanov

et al. 2022

Izv. vysš. učebn. zaved., Čern. metall.

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The article presents the results of analysis of evolution of the defective substructure of rail steel pearlite with lamellar morphology under deformation by uniaxial compression. The strain hardening of the studied steel under such deformation has a multistage character. Deformation of steel is accompanied by fragmentation of pearlite grains, which intensifies as the degree of deformation increases and reaches 0.4 of the studied foil volume at ε = 50 %. Fragments formed in ferrite plates are separated by low-angle boundaries. It was established that the average sizes of ferrite plate fragments decrease from 240 nm (ε = 15 %) to 200 nm (ε = 50 %) with an increase in the deformation degree. Fragmentation of cementite plates was revealed. It was found that the size of the fragments varies within 15 – 20 nm and weakly depends on the degree of steel deformation. Fracture of cementite lamellae, proceeding by their dissolution and cutting by mobile dislocations, was discovered. Carbon atoms that have passed from the crystal lattice of cementite to dislocations are carried out into the interlamellar space and form particles of tertiary cementite, the size of which is 2 – 4 nm. In the process of steel deformation, an inhomogeneous dislocation substructure is formed, which is due to the deceleration of dislocations by cementite particles. It was found that an increase in the deformation degree is accompanied by a decrease in the scalar and excess density of dislocations, which may be due to the escape of dislocations into low-angle boundaries, as well as their annihilation. It was established that the sources of internal stress fields are the interfaces between pearlite grains and colonies, cementite plates in pearlite grains, particles of the second phase located in the volume of ferrite plates.

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Physical Nature of Structure and Properties Degradation of Rail Surface after Long Term Operation

Громов

Yuriev²,

Перегудов

et al. 2018

JMNM

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By methods of optical, scanning and transmission electron diffraction microscopy and microhardness and tribology parameters measurement the changes regularities of structure-phase states, defect substructure of rails surface after the long term operation (passed tonnage of gross weight 500 and 1000 mln. tons) were established. It is shown that the wear rate increases in 3 and 3.4 times after passed tonnage of gross weight 500 and 1000 mln. tons, accordingly, and the friction coefficient decreases in 1.4 and 1.1 times. The cementite plates are destroying absolutely and cementite particles of around form with the sizes 10-50 nm are forming after passed tonnage 500 mln tons. The appearance of dynamical recrystallization initial stages is marked after the passed tonnage 1000 mln tons. It is shown that the operation of steel rails is accompanied by full fractures in surface layers with lamellar pearlite grains and the formation of ferrite–carbide mixtures with nanosized particles. The deformation of steel increases the densities of scalar and excess dislocations, the curvature–torsion values of the crystal lattice, and the amplitudes of internal stress fields. The possible mechanisms of established regularities are discussed. It is noted that two competitive processes can take place during rails long term operation: 1. Process of cutting of cementite particles followed by their carrying out into the volume of ferrite grains or plates (in the structure of pearlite). 2. Process of cutting, the subsequent dissolution of cementite particles, transition of carbon atoms to dislocations (into Cottrell atmospheres), transition of carbon atoms by dislocations into volume of ferrite grains or plates followed by repeat formation of nanosize cementite particles.

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Formation of Fine Structure of Differentially Hardened Rails

Cited by 4 publications

References 3 publications

Degradation of structure and properties of rail surface layer at long-term operation

Degradation of structure and properties of rail surface layer at long-term operation

Evolution of structure of rail steel lamellar pearlite under compression deformation

Physical Nature of Structure and Properties Degradation of Rail Surface after Long Term Operation

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