Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma
Processes of blisters and associated subsurface cracks nucleation during exposure of 12Cr2MoNbVB ferritic-martensitic steel and α-Fe under glow discharge hydrogen (deuterium) plasma with ion energies of ~ 1 keV and ion fluencies up to 2·10²⁴ D/м² at various temperatures have been examined. The metho...
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| Cite this: | Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma / A.V. Nikitin, G.D. Tolstolutskaya, V.V. Ruzhytskiy, I.E. Kopanets, S.A. Karpov, R.L. Vasilenko, G.Y. Rostova, N.D. Rybalchenko, B.S. Sungurov // Вопросы атомной науки и техники. — 2017. — № 2. — С. 22-28. — Бібліогр.: 22 назв. — англ. |
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Nikitin, A.V. Tolstolutskaya, G.D. Ruzhytskiy, V.V. Kopanets, I.E. Karpov, S.A. Vasilenko, R.L. Rostova, G.Y. Rybalchenko, N.D. Sungurov, B.S. 2018-06-11T17:43:52Z 2018-06-11T17:43:52Z 2017 Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma / A.V. Nikitin, G.D. Tolstolutskaya, V.V. Ruzhytskiy, I.E. Kopanets, S.A. Karpov, R.L. Vasilenko, G.Y. Rostova, N.D. Rybalchenko, B.S. Sungurov // Вопросы атомной науки и техники. — 2017. — № 2. — С. 22-28. — Бібліогр.: 22 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/134045 669.017:539.16 Processes of blisters and associated subsurface cracks nucleation during exposure of 12Cr2MoNbVB ferritic-martensitic steel and α-Fe under glow discharge hydrogen (deuterium) plasma with ion energies of ~ 1 keV and ion fluencies up to 2·10²⁴ D/м² at various temperatures have been examined. The methods used were scanning electron microscopy, thermal desorption spectroscopy and the D(³He, p)⁴He nuclear reaction. Temperature dependence of average blister diameter, the deuterium depth distribution and retention were studied. Application of hydrogen induced cracking models was considered to assess the effects of hydrogen from the plasma on the development of blisters and subsurface cracks. Based on this analysis, it is shown that significant crack growth rates can occur during reactor shut-down periods when the temperature of the structure decreases to less than about 373 K. Досліджено процеси розвитку блістерів і пов'язаних з ними підповерхневих тріщин, що виникають при впливі при різних температурах на 12Cr2MoNbVB феритно-мартенситну сталь і α-Fe водневої плазми тліючого розряду з енергією іонів ~ 1 кеВ і дозою ~ 2·10²⁴ D/м². Використано методи скануючої електронної мікроскопії, термодесорбції і ядерна реакція D(³He, p)⁴He. Отримано температурні залежності середнього діаметра блістерів, просторовий розподіл дейтерію в обсязі матеріалу і температурні інтервали його утримання. Вплив водню на розвиток блістерінга розглянуто із залученням моделей, розроблених для водневого охрихчення матеріалів. На основі цього аналізу зроблено висновок, що значні темпи зростання тріщин і блістерів можуть виникати під час періодів відключення реактора, коли температура конструкцій знижується до 373 K. Исследованы процессы развития блистеров и связанных с ними подповерхностных трещин, возникающих при воздействии при различных температурах на 12Cr2MoNbVB ферритно-мартенситную сталь и α-Fe водородной плазмы тлеющего разряда с энергией ионов ~ 1 кэВ и дозой ~ 2·10²⁴ D/м². Использованы методы сканирующей электронной микроскопии, термодесорбции и ядерная реакция (³He, p)⁴He. Получены температурные зависимости среднего диаметра блистеров, пространственное распределение дейтерия в объеме материала и температурные интервалы его удержания. Влияние водорода на развитие блистеринга рассмотрено с привлечением моделей, разработанных для водородного охрупчивания материалов. На основе этого анализа сделан вывод, что значительные темпы роста трещин и блистеров могут возникать во время периодов отключения реактора, когда температура конструкций снижается до 373 K. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Физика радиационных повреждений и явлений в твердых телах Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma Застосування моделей водневого окрихчення при аналізі закономірності росту блістерів у сталі 12Cr2MoNbVB і α-Fe, опромінених низькоенергетичною дейтерієвою плазмою Применение моделей водородного охрупчивания при анализе закономерности роста блистеров в стали 12Cr2MoNbVB и α-Fe, облученных низкоэнергетической дейтериевой плазмой Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma |
| spellingShingle |
Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma Nikitin, A.V. Tolstolutskaya, G.D. Ruzhytskiy, V.V. Kopanets, I.E. Karpov, S.A. Vasilenko, R.L. Rostova, G.Y. Rybalchenko, N.D. Sungurov, B.S. Физика радиационных повреждений и явлений в твердых телах |
| title_short |
Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma |
| title_full |
Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma |
| title_fullStr |
Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma |
| title_full_unstemmed |
Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma |
| title_sort |
application of hydrogen embritlement models to the blister growth behavior in 12cr2monbvb steel and α -fe exposed to low-energy d plasma |
| author |
Nikitin, A.V. Tolstolutskaya, G.D. Ruzhytskiy, V.V. Kopanets, I.E. Karpov, S.A. Vasilenko, R.L. Rostova, G.Y. Rybalchenko, N.D. Sungurov, B.S. |
| author_facet |
Nikitin, A.V. Tolstolutskaya, G.D. Ruzhytskiy, V.V. Kopanets, I.E. Karpov, S.A. Vasilenko, R.L. Rostova, G.Y. Rybalchenko, N.D. Sungurov, B.S. |
| topic |
Физика радиационных повреждений и явлений в твердых телах |
| topic_facet |
Физика радиационных повреждений и явлений в твердых телах |
| publishDate |
2017 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Застосування моделей водневого окрихчення при аналізі закономірності росту блістерів у сталі 12Cr2MoNbVB і α-Fe, опромінених низькоенергетичною дейтерієвою плазмою Применение моделей водородного охрупчивания при анализе закономерности роста блистеров в стали 12Cr2MoNbVB и α-Fe, облученных низкоэнергетической дейтериевой плазмой |
| description |
Processes of blisters and associated subsurface cracks nucleation during exposure of 12Cr2MoNbVB ferritic-martensitic steel and α-Fe under glow discharge hydrogen (deuterium) plasma with ion energies of ~ 1 keV and ion fluencies up to 2·10²⁴ D/м² at various temperatures have been examined. The methods used were scanning electron microscopy, thermal desorption spectroscopy and the D(³He, p)⁴He nuclear reaction. Temperature dependence of average blister diameter, the deuterium depth distribution and retention were studied. Application of hydrogen induced cracking models was considered to assess the effects of hydrogen from the plasma on the development of blisters and subsurface cracks. Based on this analysis, it is shown that significant crack growth rates can occur during reactor shut-down periods when the temperature of the structure decreases to less than about 373 K.
Досліджено процеси розвитку блістерів і пов'язаних з ними підповерхневих тріщин, що виникають при впливі при різних температурах на 12Cr2MoNbVB феритно-мартенситну сталь і α-Fe водневої плазми тліючого розряду з енергією іонів ~ 1 кеВ і дозою ~ 2·10²⁴ D/м². Використано методи скануючої електронної мікроскопії, термодесорбції і ядерна реакція D(³He, p)⁴He. Отримано температурні залежності середнього діаметра блістерів, просторовий розподіл дейтерію в обсязі матеріалу і температурні інтервали його утримання. Вплив водню на розвиток блістерінга розглянуто із залученням моделей, розроблених для водневого охрихчення матеріалів. На основі цього аналізу зроблено висновок, що значні темпи зростання тріщин і блістерів можуть виникати під час періодів відключення реактора, коли температура конструкцій знижується до 373 K.
Исследованы процессы развития блистеров и связанных с ними подповерхностных трещин, возникающих при воздействии при различных температурах на 12Cr2MoNbVB ферритно-мартенситную сталь и α-Fe водородной плазмы тлеющего разряда с энергией ионов ~ 1 кэВ и дозой ~ 2·10²⁴ D/м². Использованы методы сканирующей электронной микроскопии, термодесорбции и ядерная реакция (³He, p)⁴He. Получены температурные зависимости среднего диаметра блистеров, пространственное распределение дейтерия в объеме материала и температурные интервалы его удержания. Влияние водорода на развитие блистеринга рассмотрено с привлечением моделей, разработанных для водородного охрупчивания материалов. На основе этого анализа сделан вывод, что значительные темпы роста трещин и блистеров могут возникать во время периодов отключения реактора, когда температура конструкций снижается до 373 K.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/134045 |
| citation_txt |
Application of hydrogen embritlement models to the blister growth behavior in 12Cr2MoNbVB steel and α -Fe exposed to low-energy D plasma / A.V. Nikitin, G.D. Tolstolutskaya, V.V. Ruzhytskiy, I.E. Kopanets, S.A. Karpov, R.L. Vasilenko, G.Y. Rostova, N.D. Rybalchenko, B.S. Sungurov // Вопросы атомной науки и техники. — 2017. — № 2. — С. 22-28. — Бібліогр.: 22 назв. — англ. |
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2025-11-25T22:43:42Z |
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2025-11-25T22:43:42Z |
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1850570268490072064 |
| fulltext |
ISSN 1562-6016. PASТ. 2017. №2(108), p. 22-28.
UDC 669.017:539.16
APPLICATION OF HYDROGEN EMBRITLEMENT MODELS TO THE
BLISTER GROWTH BEHAVIOR IN 12Cr2MoNbVB STEEL
AND -Fe EXPOSED TO LOW-ENERGY D PLASMA
A.V. Nikitin, G.D. Tolstolutskaya, V.V. Ruzhytskiy, I.E. Kopanets, S.A. Karpov,
R.L. Vasilenko, G.Y. Rostova, N.D. Rybalchenko, B.S. Sungurov
Institute of Solid State Physics, Material Science and Technology NSC KIPT,
Kharkov, Ukraine
Processes of blisters and associated subsurface cracks nucleation during exposure of 12Cr2MoNbVB ferritic-
martensitic steel and -Fe under glow discharge hydrogen (deuterium) plasma with ion energies of ~ 1 keV and ion
fluencies up to 2·10
24
D/м
2
at various temperatures have been examined. The methods used were scanning electron
microscopy, thermal desorption spectroscopy and the D(
3
He, p)
4
He nuclear reaction. Temperature dependence of
average blister diameter, the deuterium depth distribution and retention were studied. Application of hydrogen
induced cracking models was considered to assess the effects of hydrogen from the plasma on the development of
blisters and subsurface cracks. Based on this analysis, it is shown that significant crack growth rates can occur
during reactor shut-down periods when the temperature of the structure decreases to less than about 373 K.
INTRODUCTION
The problem of materials selection for the vacuum
chamber and protection of the chamber from the fusion
plasma exposure is one of the most important in the
creation and design of fusion devices [1, 2]. One of the
most promising structural materials for nuclear fusion
reactors is ferritic-martensitic steel with a low activation
in a fusion neutron spectrum [3]. Despite the fact that
steel is rarely considered as the plasma facing material
due to the high sputtering coefficient, low thermal
conductivity and high atomic number of constituting
elements, adversely affecting the plasma, in recent years,
some authors discussed the use of plasma facing
elements made of steel without additional protection
[4, 5]. For example, steel is used in some places of
tokomak ASDEX-U central column as the plasma
facing material [6]. In addition, the impact of
thermonuclear plasma on the steel is possible in some
areas that are not protected with additional elements,
such as nozzles in a vacuum fusion reactor chamber, as
well as for technological discharges.
Ferritic-martensitic steels are known to be
particularly susceptible to nucleation of both blisters
and associated subsurface cracks arising during
exposure to glow discharge hydrogen plasma with ion
energies of ~ 1 keV [710]. Such low ion energies are
known to be characteristic of near-wall plasma fluxes in
fusion reactors [11].
The Fe-H system has been the subject of many
thermodynamic and kinetic researches on interstitial
solute because of the high hydrogen diffusivity in iron.
To understand hydrogen embrittlement of steel, many
studies on the role hydrogen on properties of steel have
been carried out [12]. Hydrogen induced crack growth
in materials can result from both external gaseous or
cathodic hydrogen and from internal dissolved hydrogen.
In a fusion reactor there are several potential sources of
hydrogen or hydrogen isotopes including direct
injection from the plasma, tritium gas in the breeding
blanket, nuclear (n, p) reactions within the material etc
[12].
Hydrogen has been shown to induce cracking in a
wide variety of materials, including ferritic steels,
austenitic stainless steels, nickel-based alloys and
aluminum alloys. The mechanism by which hydrogen
causes cracking is generally thought to be the collection
of hydrogen atoms at particle-matrix interfaces, grain
boundaries and ahead of the crack tip or other defects.
Temperature and hydrogen activity are two
parameters on which the crack growth rate is strongly
dependent. Material parameters such as yield strength,
hydrogen diffusivity, hydrogen trap densities and
strength, and grain boundary chemistry are also
important.
The purpose of this paper is to use existing models
of hydrogen induced crack (HIC) growth to
development of blisters and subsurface cracks in
12Cr2MoNbVB ferritic-martensitic steel and -Fe
exposed to glow discharge deuterium plasma with
energy of ~ 1 keV at ion fluencies up to ~ 2·10
24
D/m
2
.
1. MATERIAL AND METHODS
The materials used were 12Cr2MoNbVB (EP-450)
ferritic-martensitic steel and -Fe. The chemical
composition of the steel was 0.118C-12Cr-0.28Ni-
0.26Mn-1.41Mo-0.46Nb-0.21V-0.21Si-0.034P-0.004S
with balance iron, all in weight %. The heat treatment of
EP-450 consisted of quenching from 1323 K (1050 °C),
followed by tempering at 1013 K (740 °C) for 1 h. The
microstructure of the EP-450 alloy at this point
consisted of a duplex structure of ferrite and tempered
martensite at a volume ratio of approximately 1:1. Large
globular M23C6 carbides were observed along both
ferrite-ferrite and ferrite-tempered martensite grain
boundaries. Disks with diameter of 18 mm were cut
from a sheet with thickness of 2.4 mm.
The samples of -Fe (bcc) with a purity of
99.9 wt.% were annealing at 1600 K after rolling and
cutting. It contains impurities of more than a dozen
elements. The carbon and copper concentration are of
about 0.02 and 0.1%, respectively. The remaining
elements are in thousandths of a percent. The specimens
with dimensions of 107 mm were cut from a sheet with
thickness of 1 mm.
The surface of each sample was polished
mechanically and then electropolished in a standard
electrolyte to remove any mechanically damaged near-
surface layer.
Several experiments were performed on the samples
that were deformed at deformation levels in the range of
80…95%. Deformation was carried out by cold working
via rolling at room temperature.
The specimens were irradiated at various
temperatures with deuterium ions using glow gas-
discharge plasma electrodes at 1000 V, producing an
ion flux of 10
19
H(D)/(m
2
∙s). In this study we chose D
instead H in order to easily measure the depth
dependence of the implanted and diffused hydrogen.
The maximum irradiation fluence was 2·10
24
D/m
2
.
The temperature during plasma exposure was varied
between 240 and 400 K. The specimen was placed in a
resistively-heated holder. The target temperature was
continuously monitored using a thermocouple in the
base of the specimen holder and was attached to the
lower surface of specimen. Temperature maintenance
on the steel samples in this device was achieved either
by resistive heating or liquid nitrogen cooling. The
temperature was maintained to within ±2.5 K. A
detailed schematic diagram of the experimental setup is
presented in Ref. [13].
The D concentration in the plasma-exposed samples
was measured by means of the D(
3
He, α)H reaction,
where protons were analyzed. To determine the D
concentration at larger depths, an analyzing beam of
3
He ions with energies varied from 0.3 to 1.4 MeV was
used. The proton yields measured at different
3
He ion
energies allow measuring the D depth profile at depths
of up to 2 μm.
Total deuterium retention in the samples was
monitored ex-situ using thermal desorption
spectrometry (TDS). A resistive heater was used to heat
the samples at a ramp rate of 6 K/s and the sample
temperature was raised to 1300 K. D2 molecules
released during TDS run were monitored by monopole
mass spectrometer.
A JEOL JSM-7001F 00 scanning electron
microscope was used to study the surface morphology.
Investigations of surface microstructure were performed
using a ММО-1600-АТ metallographic microscope.
2. RESULTS AND DISCUSSION
The influence of irradiation fluence on the kinetics
of blister growth at 273 K on surface of 12Cr2MoNbVB
steel is shown in Fig. 1. This temperature was chosen
based on the temperature dependence data of the
blistering processes on this steel [10, 13]. It is seen that
for fluencies (1…5)·10
23
m
-2
the mean diameter and
density of blisters increases monotonically with
increasing fluence and then the growth of blisters stops.
Based on these results, the investigations of all
blisters characteristics were performed in the dose
saturation area.
0 2 4 6 8 10
500
1000
1500
0
10
20
30
40
B
lis
te
r
d
e
n
s
it
y
,
c
m
-2
Fluence 10
23
, D
2
m
-2
)
A
v
e
ra
g
e
b
lis
te
r
s
iz
e
,
m
Fig. 1. Fluence dependence at temperature 273 K
of kinetics of blister growth during hydrogen plasma
exposure of 12Cr2MoNbVB steel
Fig. 2 shows the temperature dependence of average
diameters and density of blisters (ρ) formed under
deuterium plasma on the surface of 12Cr2MoNbVB
steel and -Fe.
The temperature dependence of mean blister
diameter has a clearly expressed maximum at 283 and
250 K for steel and -Fe, respectively. The density of
blisters at temperatures 220…260 K does not change
substantially, and then decreases. The specific
temperature bounds for -Fe shifted to lower
temperatures compared to steel.
Fig. 2. Temperature dependence of average diameter
and density of blisters formed under deuterium plasma
irradiation to 1·10
24
D/m
2
for 12Cr2MoNbVB steel
and -Fe
It was mentioned in the introduction that the
emergence of blisters associated with underground
fissures. Various aspects of hydrogen induce cracking in
a wide variety of materials were considered by several
authors [14]. The observations of crack growth of high-
strength steel in gaseous embrittling hydrogen have
been done [1416]. Modeled the crack growth rate-
temperature dependence of HT-9 steel were found. The
examples of the two types of curves of crack growth
rate versus temperature are given in Fig. 3. The specific
features of the crack growth due to different yield
strength effects (ys1 < ys2) are presented also. As can
be seen from Fig. 3 the temperature of rapid decline of
the crack growth rate is decreased with decreasing of
yield strength.
Fig. 3. Calculated dependence of crack growth vs
reciprocal temperature for steels in low pressure
hydrogen: curves #1 [17], #2 [12], and #3 [18]
The dependence of the crack growth rate da/dt could
be described by the following hydrogen adsorption
isotherm for the low-temperature regime (curve #1), eq.
(1), and the high-temperature regime (curve #1), eq. (2),
in Fig. 3:
(1)
(2)
where P is the hydrogen partial pressure; Em the
energy of migration of an atom from an initial
physisorption site to a final chemisorption site; R is the
gas constant and T is the temperature. C3 and C4 are
constants, and H is the heat of adsorption of hydrogen
[12, 19].
Eqs. (1) and (2) are appropriate for assessing the
crack growth rates of a fusion reactor first wall exposed
to a hydrogen gas. To adopt them for evaluating the
effect of hydrogen plasma on the crack growth rate it is
necessary to relate the hydrogen flux impinging on a
first wall to an equivalent hydrogen gas pressure which
would give the same collision rate with the surface.
Such a comparison has been made by Ashby [20] where
hydrogen flux of 10
17
H/(cm
2
∙s) was equal to a pressure
of 10
-2
Pa. This pressure was used to represent the effect
of hydrogen plasma on the crack growth rate of HT-9 as
a first estimate. It is clear from this calculation that the
hydrogen activity of the plasma is sufficiently low as to
have no effect on the crack growth rate of HT-9 based
on this analysis. The maximum crack growth calculated
with eqs. (1) and (2) for a pressure of 10
-2
Pa is
1.6∙10
-9
cm/s, and it occurs at a temperature of 148 K.
At 298 K the crack growth rate is 10
-13
, and at 573 K it
is 10
-15
cm/s. However if it taken into account the
hydrogen concentration in a fusion first wall structure
made of HT-9 for various surface reactions and for
conditions of hydrogen generation by (n, p) reaction and
direct injection from the plasma a crack growth rate of
10
-1
cm/s was estimated for this condition at a
temperature of 348 K [12]. In this way, significant crack
growth rates will be feasible in atomic hydrogen at
temperatures up to 370 K (see curve #2, Fig. 3).
Comparison of the curves shown in Figs. 2 and 3
demonstrates correlation between temperature ranges of
embrittlement and blistering. Taking into account that
blister diameter defines the linear dimension of
associated subsurface crack, and the latter is accepted as
a characteristic of crack growth rate, the dependence of
average blisters size on the temperature seems in good
agreement with theoretical predictions. Some scatter of
points at temperatures 290…300 K for steel EP-450
assumes the existence of the second maximum. The
reliability of this two-peak phenomenon requires
additional investigation.
The kinetics of hydrogen assisted crack growth in
high-strength steels are governed by the combined
effects of chemical and mechanical driving forces, and
relate to the individual processes involved in the
transport of hydrogen from the gas phase to the point of
fracture and to the embrittlement process at the fracture
process zone (FPZ). The embrittlement process is
expected to depend on both hydrogen concentration and
tensile stress level in the FPZ. Models based on the
critical role of stress in gaseous hydrogen embrittlement
suggested that the FPZ can be either at the crack tip
(surface) or at some distance away from the crack tip
(bulk). On the other hand, it may be more reasonable to
assume that the location of the FPZ is determined by
hydrogen segregation at specific microstructural
features in the near surface region. Theoretical and
experimental results indicate that hydrogen segregation
(several orders of magnitude higher than the lattice
solubility) can occur at trap sites; such as, grain
boundaries, voids, second phase boundaries and
dislocations.
The physical model of hydrogen blister nucleation in
metals is predicted that dissolved hydrogen atoms can
aggregate into a vacancy-hydrogen cluster. The
hydrogen atoms in this cluster become hydrogen
molecules that can stabilize the cluster (small cavity)
[21]. The cluster will grow preferentially in the sites of
stress concentration because of high hydrogen
concentration. When the blister nucleus grows to a
critical size Ccr and the stress concentration equates to
the atomic binding force, which may be decreased by
hydrogen, cracks will initiate from the wall of the cavity
due to the internal hydrogen pressure. In a recently
published paper [22], it was shown that most of the
hydrogen blisters initiate from grain boundaries or
matrix interface and inclusion or second phase particles.
The cohesive strength of interface is much lower than
that of the matrix. Cracks are easy to initiate on
interface and propagate. Therefore, the probability of
initiation of hydrogen blisters on grain boundary and
interface of second phase and matrix is higher than that
in matrix.
Thus, since hydrogen activity is one of the key
parameters that determine the crack growth rate, it is
necessary to clarify the hydrogen retention and transport
behavior in investigated steel and -Fe.
The trapping of deuterium by defects represent the
data obtained by TDS. Fig. 4 shows desorption profiles
of deuterium from -Fe exposed to deuterium plasma at
283 K and ion implanted at 90 K.
200 400 600 800 1000 1200
0
30
60
90
120
D
e
s
o
rp
ti
o
n
r
a
te
,
a
rb
it
ra
ry
u
n
it
s
Temperature, K
1
2
Fig. 4. Thermal desorption spectra of D from -Fe ion
implanted at 90 K to a dose of 1·10
21
D/m
2
(1)
and exposed to deuterium plasma at 283 K
to 1·10
24
D/m
2
(2)
In the case of plasma exposure, the release of
deuterium from iron sample starts at ~ 330 K. The
maximum of desorption peak is observed at 470 K. The
decreasing of temperature of the exposure during ion
implantation led to complication of the TD spectra. In
addition, the increasing of deuterium retention (in
comparison with the 283 K case) was found. Thus, the
temperature interval of blister nucleation and growth
correlates with the temperatures corresponding to strong
hydrogen trapping in -Fe (see Figs. 2, 4).
To understand the hydrogen transport behavior in
steel and -Fe the depth profiling is critically important.
Fig. 5 presents the depth distribution profiles of
deuterium in 12Cr2MoNbVB steel exposed to 1 keV
deuterium plasma to 1·10
24
D/m
2
at room temperature.
Fig. 5. Distribution profiles of deuterium
in 13Cr2MoNbVB steel exposed to deuterium plasma
at 300 K to a dose of 2·10
24
D/m
2
at a depth
of 0…1.8 () and ~ 200 μm () from irradiated surface
Initially, measurements were carried out on the
plasma-exposed surface of the specimen, and then after
removing of material by electropolishing, measurements
were continued at the depths starting at 200 μm from the
front surface. An essentially uniform distribution of
deuterium within the range 0…200 µm with an average
concentration of ~ 0.5 at.% has been observed.
The calculated normal-incident range of 0.5 keV D
+
in iron is about 7 nm. Detection of deuterium at a depth
of 200 μm confirms that the implanted D migrates into
the bulk far beyond the ion range and thereby can
promote nucleation of cavities and cracks at this depth.
Structural alloys are beginning to serve in various
initial metallurgical states depending on the mechanical
treatment (forging, rolling or drawing), and thermal
history (intermediate annealing and final hardening
stories) that were used during their production. It is
anticipated that the structural-phase state of the near-
surface region of a specific alloy can affect the various
processes of erosion.
Figs. 6, 7 show surface morphologies and
microstructures of recrystallized and 80% deformed
specimens of -Fe after irradiation to a fluence of
2∙10
24
D/m
2
at 273 K.
a
b
Fig. 6. Surface morphology (a) and microstructure
of cross-section of recrystallized -Fe samples after
irradiation with deuterium plasma to 2·10
24
D/m
2
at 273 K (b)
For recrystallized (RE) -Fe the large blisters were
observed with sizes of a few tens of micrometers and a
shape of high dome. These blisters showed a multi-
layered structure like steps (see Fig. 6,a). The
microstructures of cross-section of recrystallized -Fe
samples had low elongation grains with a grain size of
50…100 m.
In the case of pre-exposure deformation (PD) most
of blisters had spherical-like shapes (see Fig. 7). The
blister height and the blister size have a virtually
constant relation: the height is more than one order of
magnitude smaller than the blister size (see Fig. 7,a).
This could be attributed to the microstructure of PD
-Fe, which layered with high elongation grains
arranged parallel to the surface. Besides the layered
structures were somewhat disordered. Some cracks were
observed in grain boundaries (see Fig. 7,b). These
results indicate that structural state has a significant
impact on the development of blistering and its
parameters.
a
b
Fig. 7. Surface morphology (a) and microstructure
of cross-section of 80% deformed -Fe samples after
irradiation with deuterium plasma to 2·10
24
D/m
2
at 273 K (b)
The blistering development is influenced not only by
irradiation conditions, such ion energy, flux and fluence
of incident H, subsurface microstructure and
temperature of material but also the material yield
strength. It is well known that the tensile strength is
proportional to the hardness of material. The following
Table shows Vickers hardness (load 50 g) for specimens
having different structure.
Hardness of specimens
No. Regime of treatment
Hardness,
Hv
50
, kG/mm
2
1 Recrystallized -Fe 140…160
2 80 % deformed -Fe 260…300
3 Cold working 95% EP-450 385…425
4 Stress relieved EP-450 270…300
Fig. 8 represents the dependence of blisters density
on reciprocal temperature for 95% cold working and
stress relieved 12Cr2MoNbVB steel and 80% deformed
and recrystallized -Fe under deuterium plasma
irradiation to 2·10
24
D/m
2
at 273…350 K.
0.0027 0.0030 0.0033 0.0036 0.0039 0.0042 0.0045
10
0
10
1
10
2
10
3
10
4
lg
1/T (K)
2
1
3
4
0.0027 0.0030 0.0033 0.0036 0.0039 0.0042 0.0045
10
0
10
1
10
2
10
3
10
4
lg
1/T (K)
2
1
3
4
Fig. 8. Density of blisters – 1/T relationship for
12Cr2MoNbVB steel (1, 3) and -Fe (2, 4) under
deuterium plasma irradiation to 2·10
24
D/m
2
for cold
working (1, 2) and stress-relieved (3, 4) states
Comparison of the data shown in Fig. 8 and Table
reveals that an increase of hardness shifts the curves of
blisters density to higher temperatures that in qualitative
agreement with the model of crack growth of high-
strength steel in gaseous embrittling hydrogen (see
Fig. 3). It should be noted that the features of defect
substructure caused by pre-exposure deformation are
associated with a significant increase of the density of
crack nucleation sites that may lead to a change of the
mechanisms of hydrogen-related blistering.
Gerberich, Chen and St. John [15] have calculated
the hydrogen-stress field interactions to develop a
kinetic model of crack growth for internal hydrogen.
They assumed that the crack growth kinetics which are
nearly stress-intensity independent are controlled
primarily by the plastic stress field. To account for
strong hydrogen trapping, which is expected in HT-9, it
is shown that the strong temperature dependence of this
trapping could cause the crack velocity to decrease at
higher temperatures.
Analysis of the temperature dependence of crack
growth for internal hydrogen suggests that at
temperatures exceeding about 323 К the crack growth
rate decreases very rapidly to values that would be
insignificant [15].
Alternate application of hydrogen induced cracking
models to assess the possible effects of hydrogen from
the plasma, nuclear reactions and cathodic corrosion has
indicated that only internal hydrogen generated by
nuclear reactions may potentially cause cracking at
reactor operating temperatures. A crack growth rate of
60 cm/yr was calculated for a steady-state hydrogen
concentration of 0.0005…0.5 appm at a temperature
exceeding 473 К.
Experimental data obtained in this study indicate
that development of blisters and associated subsurface
cracks during exposure of 12Cr2MoNbVB ferritic-
martensitic steel and -Fe under glow discharge
hydrogen (deuterium) plasma is observed up to
temperature 350 K.
CONCLUSSIONS
Processes of blisters nucleation and associated
subsurface cracks arising during exposure of
12Cr2MoNbVB ferritic-martensitic steel and -Fe in
glow discharge hydrogen (deuterium) plasma with ion
energies of ~ 1 keV and ion fluencies of ~ 2·10
24
D/m
2
at various temperatures have been defined
experimentally.
A close correlation of temperature ranges of
hydrogen-induced blistering and theoretical predictions
of HIC growth (hydrogen embrittlement) has been
found.
The temperature interval of blister formation at a
flux of 10
19
H(D)/(m
2
∙s) depends on the retention and
accumulation of large amounts of hydrogen.
Post-irradiation measurements of deuterium content
showed that deuterium concentrations were relatively
constant within investigated depth and extended far
beyond the implantation range. Penetration of hydrogen
to a greater depth confirms the development of cracks
embryos of blisters at depths on the orders of magnitude
exceeding the range of hydrogen ions with energy
1 keV.
It is established that the initial state of EP-450
ferritic-martensitic steel and -Fe has a strong influence
on the development of blisters and crack formation
under hydrogen plasma exposhure.
Significant crack growth rates could occur during
reactor shut-down periods when the temperature of the
structure decreases to less than about 373 К.
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Article received 22.02.2017
ПРИМЕНЕНИЕ МОДЕЛЕЙ ВОДОРОДНОГО ОХРУПЧИВАНИЯ ПРИ АНАЛИЗЕ
ЗАКОНОМЕРНОСТИ РОСТА БЛИСТЕРОВ В СТАЛИ 12Cr2MoNbVB И -Fe,
ОБЛУЧЕННЫХ НИЗКОЭНЕРГЕТИЧЕСКОЙ ДЕЙТЕРИЕВОЙ ПЛАЗМОЙ
А.В. Никитин, Г.Д. Толстолуцкая, В.В. Ружицкий, И.Е. Копанец, С.А. Карпов,
Р.Л. Василенко, Г.Ю. Ростова, Н.Д. Рыбальченко, Б.С. Сунгуров
Исследованы процессы развития блистеров и связанных с ними подповерхностных трещин,
возникающих при воздействии при различных температурах на 12Cr2MoNbVB ферритно-мартенситную
сталь и -Fe водородной плазмы тлеющего разряда с энергией ионов ~ 1 кэВ и дозой ~ 2·10
24
D/м
2
.
Использованы методы сканирующей электронной микроскопии, термодесорбции и ядерная реакция
D(
3
Не, р)
4
Не. Получены температурные зависимости среднего диаметра блистеров, пространственное
распределение дейтерия в объеме материала и температурные интервалы его удержания. Влияние водорода
на развитие блистеринга рассмотрено с привлечением моделей, разработанных для водородного
охрупчивания материалов. На основе этого анализа сделан вывод, что значительные темпы роста трещин и
блистеров могут возникать во время периодов отключения реактора, когда температура конструкций
снижается до 373 K.
ЗАСТОСУВАННЯ МОДЕЛЕЙ ВОДНЕВОГО ОКРИХЧЕННЯ ПРИ АНАЛІЗІ
ЗАКОНОМІРНОСТІ РОСТУ БЛІСТЕРІВ У СТАЛІ 12Cr2MoNbVB І -Fe, ОПРОМІНЕНИХ
НИЗЬКОЕНЕРГЕТИЧНОЮ ДЕЙТЕРІЄВОЮ ПЛАЗМОЮ
А.В. Нікітін, Г.Д. Толстолуцька, В.В. Ружицький, І.Є. Копанець, С.О. Карпов,
Р.Л. Василенко, Г.Ю. Ростова, Н.Д. Рибальченко, Б.С. Сунгуров
Досліджено процеси розвитку блістерів і пов'язаних з ними підповерхневих тріщин, що виникають при
впливі при різних температурах на 12Cr2MoNbVB феритно-мартенситну сталь і -Fe водневої плазми
тліючого розряду з енергією іонів ~ 1 кеВ і дозою ~ 2·10
24
D/м
2
. Використано методи скануючої електронної
мікроскопії, термодесорбції і ядерна реакція D(
3
Не, р)
4
Не. Отримано температурні залежності середнього
діаметра блістерів, просторовий розподіл дейтерію в обсязі матеріалу і температурні інтервали його
утримання. Вплив водню на розвиток блістерінга розглянуто із залученням моделей, розроблених для
водневого охрихчення матеріалів. На основі цього аналізу зроблено висновок, що значні темпи зростання
тріщин і блістерів можуть виникати під час періодів відключення реактора, коли температура конструкцій
знижується до 373 K.
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