Electron – beam treatment with 20 J/cm2 energy density of Fe-0.20C-23Cr-18Ni stainless steel increases
fatigue life up to 2.1 times. Fracture surface investigations have been carried out by the methods of
scanning and transmission diffraction electron microscopy and layer-by-layer analysis of structural phase
states and defect substructure of steel subjected to the multicyclic fatigue tests, has been made as well.
Nanosize (Cr,Fe)23C6 carbides formation and physical reasons of steel fatigue life increase by electron –
beam treatment have been found out.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3480

Gromov, V.E.

Konovalov, S.V.

Sizov, V.V.

Vorobyov, S.V.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 2, 02NFC02(2pp) (2012) 
 
 
2304-1862/2012/1(2)02NFC02(2) 02NFC02-1  2012 Sumy State University 
Nanosize Carbides Formation and Fatigue Life Increase of Stainless Steel  
by Electron Beam Treatment 
 
V.E. Gromov1, V.V. Sizov1, S.V. Vorobyov1, Yu.F. Ivanov2, S.V.  Konovalov1, V.I. Myasnikova1  
 
1 Siberian State Industrial University, 42, Kirov str., 654007 Novokuznetsk, Russia 
2 Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, 2/3, Akademicheskii Ave, 
634055 Tomsk, Russia 
 
(Received 15 February 2012; published online15 August 2012) 
 
Electron – beam treatment with 20 J/cm2 energy density of Fe-0.20C-23Cr-18Ni stainless steel increas-
es fatigue life up to 2.1 times. Fracture surface investigations have been carried out by the methods of 
scanning and transmission diffraction electron microscopy and layer-by-layer analysis of structural phase 
states and defect substructure of steel subjected to the multicyclic fatigue tests, has been made as well. 
Nanosize (Cr,Fe)23C6 carbides formation and physical reasons of steel fatigue life increase by electron – 
beam treatment have been found out. 
 
Keywords: Fatigue, Electron – beam treatment, Defect substructure 
 
 PACS numbers: 81.65.-b, 81.70.Bt 
 
 
1. INTRODUCTION 
 
Much material, obtained by the modern structural 
methods of investigations, demonstrates complex na-
ture of fatigue, dependence on various factors. Fatigue 
life increase of stainless steels is connected with con-
centrated energy flux application, modifying materials 
surface. 
The aim of our work is the comparative, layer–by–
layer analysis of a structure, phase composition and 
defect substructure of Fe-0.20C-23Cr-18Ni austenite 
steel, subjected to multicycle fatigue up to fracture, and 
the mechanism detection of fatigue life increase after 
high – intensive electron – beam treatment. 
 
2. MATERIALS AND METHODS 
 
Fe-0.20C-23Cr-18Ni steel is an investigation mate-
rial. Electron – beam treatment conditions: eU electron 
energy = 18 keV; duration of pulse electron – beam ac-
tion τ=50 µs; quantity of pulses N=3; frequency of puls-
es f = 0.3 s-1; electron beam energy density Es=20J/cm2.  
The fatigue tests were carried out with special in-
stallation usage according to the scheme of cycle 
asymmetrical cantilever bend. Cycle loading stress– 
20MPa, frequency loading – 20 cycles/s, testing tem-
perature – 296 K, the number of cycles before steel 
fracture ~3.3•105. Electron beam non – treated steel 
samples (initial state) were fractured after ~ 1.5•105 
cycles loading. 
The investigations of steel structure – phase state 
were carried out by the methods of scanning and 
transmission diffraction electron microscopy. 
 
3. RESULTS AND DISCUSSION 
 
In the initial polycrystal state of the investigated 
steel there’s a dislocation substructure like networks 
(Fig. 1, a) with ~ 4•1010 cm-2 scalar density in the grain 
volume. The other element of a grain structure is mi-
crotwins (Fig. 1, b) of the one twinning system, rarely-of 
two systems. 
The second phase particles carbide (Cr, Fe)23C6 in 
the form of longitudinal interlayers with the  longitudi-
nal sizes of 0.2 – 1.0 μm and transversal sizes 40- 
100 nm are revealed along the grain boundaries 
(Fig. 1,c). They have the round form 0.5 μm (Fig. 1, d) in 
the grains volume. 
 
 
 
Fig. 1 – Electron microscope image of Fe-0.20C-23Cr-18Ni 
steel structure in the initial state; a-c – light  fields; d – dark 
field obtained in the (111) –Fe reflection. Second phase parti-
cles, located along the boundary (c) and in the grain volume 
(d), are shown by the arrows in (c) and (d) 
 
High level of inner stress field, being formed near the 
interface boundary of particle/matrix, points out some 
potentially dangerous places in the initial state material 
structure, that can cause fatigue cracks formation with 
its following fracture.  
The images of steel surface fracture, after ~ 1.5•105 
cycles loading, obtained by the methods of scanning elec-
tron microscopy, show that the maximum effect of a 
structure transformation develops in the pre-surface 
layer of a 10…12 µm thickness. The forming layer has 
got small sizes (0.5…1.0 µm) of fracture crystallites and 
is separated from the basic sample volume by the clear 
boundary, along which there are a lot of micropores. 
There were many changes in a structure phase state 
of the given layer while experimenting. First, the junc-
 
V.E. GROMOV, V.V. SIZOV PROC. NAP 1, 02NFC02 (2012) 
 
 
02NFC02-2 
tion of two microtwins systems leads to steel volume 
formation with nanoscale structure (Fig. 2). Crystallite 
sizes vary from 25 to 80 nm. 
 
 
 
Fig. 2 – Nanocrystal structure, forming in the surface layer 
the fractured steel; a – light field; b – microelectron diffraction 
pattern, reflections, where dark zone 1 –(c), 2 – (d) is obtained, 
are shown by the arrows; c, d – dark fields, obtained in (111) –
Fe, (111) –Fe+(002) –Fe diffraction rings reflections 
 
4. PROCEEDING PAPER STRUCTURE AND 
CORRESPONDING STYLES  
 
Second, there’re some longitudinal microcracks along 
the grains boundaries containing the second – phase 
interlayers.  
Third, fatigue tests form a band substructure in the 
grains volume, that don’t contain microtwins. The bands 
were fragmented; the sizes of fragments vary from 50 
nm to 80 nm.  
Fourth, fatigue fracture is accompanied by →  mar-
tensite transformation in the steel surface layer. -
martensite crystals were found along the grains bounda-
ries.  – martensite formation is connected with cracks 
formation. There are some microcracks along the grains 
boundaries where  – martensite plates were detected. 
This allows to suppose that the martensite transfor-
mation has been initiated by the elastic stresses, being 
formed the grains interface boundaries under fatigue.  
Fifth, steel fatigue failure leads to multimicrotwin-
ning and consequently to the complex curvature-torsion 
of a steel crystal lattice and a big number of bending 
extinction contours of a different form and size indicates 
about it.  
In a result of a steel fatigue loading there are some 
material zones with the critical structure, unable to the 
following evolution in the sample surface layer of 
a ~ 10 µm thickness. This should lead to microcracks 
appearance and growth and, consequently, to the sample 
fracture as a whole. The second factor, that can lead to 
the fatigue life decrease of the investigated steel, is the 
presence of (Fe, Cr)23C6 carbide particles in it. Incompat-
ibility of particles and matrix deformation is accompa-
nied by the internal stress fields formation leading to the 
cracks appearance under critical substructure genera-
tion.  
It has been established that steel electron-beam 
treatment of 20 J/cm2 energy density increases its fa-
tigue life up to 2.1 times owing to the processes suppres-
sion, allowing critical structure zones formation, being 
the potential location of micro cracks generation. 
Samples fatigue loading, subjected to the preliminary 
electron-beam treatment, is followed by the formation of 
the second phase precipitates (Fig. 3, a). The particles 
have got round form; the particle sizes vary from 20 to 
40 nm. Micro-electron diffraction pattern indexing, ob-
tained from the material volume, containing the second 
phase precipitates (Fig. 3, b) allows to say that given 
particles are carbides on the basis of (Cr, Fe)23C6 chro-
mium composition. 
 
 
 
Fig. 3 – Electron-microscope image of carbide-phase particles, 
detected in the grain volume of steel surface layer, treated by 
electron beam and followed fracture; a – dark field, obtained 
in (002) – Fe + (006)Cr23C6 coincidence reflections; b – microe-
lectron diffraction pattern, the reflection is shown by the ar-
row where the dark field has been obtained; carbide-phase 
particles are shown by the arrows in (a) 
 
The investigations of an irradiation and fracture sur-
faces are showed, that one of the possible reasons of steel 
samples fracture was microcraters generation on the 
irradiation surface. Microcraters, being stress concentra-
tors, tended to micro – and macrocracks formation, and 
their development led to the sample fracture. One of the 
ways of the following steel fatigue life increase is the 
suppression of craters generation on the surface. 
 
AKNOWLEDGEMENTS 
 
This work has been performed by the partial finan-
cial support of FSP «Scientific and scientific pedagogi-
cal staff of innovative Russia in 2009-2013» (contract 
№02.740.11.0538).  
 


Nanosize Carbides Formation and Fatigue Life Increase of Stainless Steel by Electron Beam Treatment

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 2, 02NFC02(2pp) (2012)   2304-1862/2012/1(2)02NFC02(2) 02NFC02-1  2012 Sumy State University Nanosize Carbides Formation and Fatigue Life Increase of Stainless Steel  by Electron Beam Treatment  V.E. Gromov1, V.V. Sizov1, S.V. Vorobyov1, Yu.F. Ivanov2, S.V.  Konovalov1, V.I. Myasnikova1   1 Siberian State Industrial University, 42, Kirov str., 654007 Novokuznetsk, Russia 2 Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, 2/3, Akademicheskii Ave, 634055 Tomsk, Russia  (Received 15 February 2012; published online15 August 2012)  Electron – beam treatment with 20 J/cm2 energy density of Fe-0.20C-23Cr-18Ni stainless steel increas-es fatigue life up to 2.1 times. Fracture surface investigations have been carried out by the methods of scanning and transmission diffraction electron microscopy and layer-by-layer analysis of structural phase states and defect substructure of steel subjected to the multicyclic fatigue tests, has been made as well. Nanosize (Cr,Fe)23C6 carbides formation and physical reasons of steel fatigue life increase by electron – beam treatment have been found out.  Keywords: Fatigue, Electron – beam treatment, Defect substructure   PACS numbers: 81.65.-b, 81.70.Bt   1. INTRODUCTION  Much material, obtained by the modern structural methods of investigations, demonstrates complex na-ture of fatigue, dependence on various factors. Fatigue life increase of stainless steels is connected with con-centrated energy flux application, modifying materials surface. The aim of our work is the comparative, layer–by–layer analysis of a structure, phase composition and defect substructure of Fe-0.20C-23Cr-18Ni austenite steel, subjected to multicycle fatigue up to fracture, and the mechanism detection of fatigue life increase after high – intensive electron – beam treatment.  2. MATERIALS AND METHODS  Fe-0.20C-23Cr-18Ni steel is an investigation mate-rial. Electron – beam treatment conditions: eU electron energy = 18 keV; duration of pulse electron – beam ac-tion τ=50 µs; quantity of pulses N=3; frequency of puls-es f = 0.3 s-1; electron beam energy density Es=20J/cm2.  The fatigue tests were carried out with special in-stallation usage according to the scheme of cycle asymmetrical cantilever bend. Cycle loading stress– 20MPa, frequency loading – 20 cycles/s, testing tem-perature – 296 K, the number of cycles before steel fracture ~3.3•105. Electron beam non – treated steel samples (initial state) were fractured after ~ 1.5•105 cycles loading. The investigations of steel structure – phase state were carried out by the methods of scanning and transmission diffraction electron microscopy.  3. RESULTS AND DISCUSSION  In the initial polycrystal state of the investigated steel there’s a dislocation substructure like networks (Fig. 1, a) with ~ 4•1010 cm-2 scalar density in the grain volume. The other element of a grain structure is mi-crotwins (Fig. 1, b) of the one twinning system, rarely-of two systems. The second phase particles carbide (Cr, Fe)23C6 in the form of longitudinal interlayers with the  longitudi-nal sizes of 0.2 – 1.0 μm and transversal sizes 40- 100 nm are revealed along the grain boundaries (Fig. 1,c). They have the round form 0.5 μm (Fig. 1, d) in the grains volume.    Fig. 1 – Electron microscope image of Fe-0.20C-23Cr-18Ni steel structure in the initial state; a-c – light  fields; d – dark field obtained in the (111) –Fe reflection. Second phase parti-cles, located along the boundary (c) and in the grain volume (d), are shown by the arrows in (c) and (d)  High level of inner stress field, being formed near the interface boundary of particle/matrix, points out some potentially dangerous places in the initial state material structure, that can cause fatigue cracks formation with its following fracture.  The images of steel surface fracture, after ~ 1.5•105 cycles loading, obtained by the methods of scanning elec-tron microscopy, show that the maximum effect of a structure transformation develops in the pre-surface layer of a 10…12 µm thickness. The forming layer has got small sizes (0.5…1.0 µm) of fracture crystallites and is separated from the basic sample volume by the clear boundary, along which there are a lot of micropores. There were many changes in a structure phase state of the given layer while experimenting. First, the junc- V.E. GROMOV, V.V. SIZOV PROC. NAP 1, 02NFC02 (2012)   02NFC02-2 tion of two microtwins systems leads to steel volume formation with nanoscale structure (Fig. 2). Crystallite sizes vary from 25 to 80 nm.    Fig. 2 – Nanocrystal structure, forming in the surface layer the fractured steel; a – light field; b – microelectron diffraction pattern, reflections, where dark zone 1 –(c), 2 – (d) is obtained, are shown by the arrows; c, d – dark fields, obtained in (111) –Fe, (111) –Fe+(002) –Fe diffraction rings reflections  4. PROCEEDING PAPER STRUCTURE AND CORRESPONDING STYLES   Second, there’re some longitudinal microcracks along the grains boundaries containing the second – phase interlayers.  Third, fatigue tests form a band substructure in the grains volume, that don’t contain microtwins. The bands were fragmented; the sizes of fragments vary from 50 nm to 80 nm.  Fourth, fatigue fracture is accompanied by →  mar-tensite transformation in the steel surface layer. -martensite crystals were found along the grains bounda-ries.  – martensite formation is connected with cracks formation. There are some microcracks along the grains boundaries where  – martensite plates were detected. This allows to suppose that the martensite transfor-mation has been initiated by the elastic stresses, being formed the grains interface boundaries under fatigue.  Fifth, steel fatigue failure leads to multimicrotwin-ning and consequently to the complex curvature-torsion of a steel crystal lattice and a big number of bending extinction contours of a different form and size indicates about it.  In a result of a steel fatigue loading there are some material zones with the critical structure, unable to the following evolution in the sample surface layer of a ~ 10 µm thickness. This should lead to microcracks appearance and growth and, consequently, to the sample fracture as a whole. The second factor, that can lead to the fatigue life decrease of the investigated steel, is the presence of (Fe, Cr)23C6 carbide particles in it. Incompat-ibility of particles and matrix deformation is accompa-nied by the internal stress fields formation leading to the cracks appearance under critical substructure genera-tion.  It has been established that steel electron-beam treatment of 20 J/cm2 energy density increases its fa-tigue life up to 2.1 times owing to the processes suppres-sion, allowing critical structure zones formation, being the potential location of micro cracks generation. Samples fatigue loading, subjected to the preliminary electron-beam treatment, is followed by the formation of the second phase precipitates (Fig. 3, a). The particles have got round form; the particle sizes vary from 20 to 40 nm. Micro-electron diffraction pattern indexing, ob-tained from the material volume, containing the second phase precipitates (Fig. 3, b) allows to say that given particles are carbides on the basis of (Cr, Fe)23C6 chro-mium composition.    Fig. 3 – Electron-microscope image of carbide-phase particles, detected in the grain volume of steel surface layer, treated by electron beam and followed fracture; a – dark field, obtained in (002) – Fe + (006)Cr23C6 coincidence reflections; b – microe-lectron diffraction pattern, the reflection is shown by the ar-row where the dark field has been obtained; carbide-phase particles are shown by the arrows in (a)  The investigations of an irradiation and fracture sur-faces are showed, that one of the possible reasons of steel samples fracture was microcraters generation on the irradiation surface. Microcraters, being stress concentra-tors, tended to micro – and macrocracks formation, and their development led to the sample fracture. One of the ways of the following steel fatigue life increase is the suppression of craters generation on the surface.  AKNOWLEDGEMENTS  This work has been performed by the partial finan-cial support of FSP «Scientific and scientific pedagogi-cal staff of innovative Russia in 2009-2013» (contract №02.740.11.0538).   

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Nanosize Carbides Formation and Fatigue Life Increase of Stainless Steel by Electron Beam Treatment

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