The corrosion resistance of heatproof nickel alloy in molten fluoride salts
Studies have been made into corrosion and mechanical properties of high-nickel alloys prepared at NSC KIPT on the basis of high-purity metal components. Corrosion tests of the Hastelloy-type alloy in fluoride melts at 650°C revealed formation of no films in the process of corrosion during 700 hours....
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Azhazha, V.M. Bakai, A.S. Bobrov, Yu.P. Virich, V.D. Yemlyaninova, T.G. Kapustin, V.L. Kovtun, K.V. Lavrinenko, S.D. Malykhin, D.G. Petel’guzov, I.A. Pylypenko, M.M. Savchenko, V.I. Semyonov, N.A. Solopikhin, A.D. Shirokov, B.M. 2015-04-19T13:34:36Z 2015-04-19T13:34:36Z 2005 The corrosion resistance of heatproof nickel alloy in molten fluoride salts / V.M. Azhazha, A.S. Bakai, Yu.P. Bobrov, V.D. Virich, T.G. Yemlyaninova, V.L. Kapustin, K.V. Kovtun, S.D. Lavrinenko, D.G. Malykhin, I.A. Petel’guzov, M.M. Pylypenko, V.I. Savchenko, N.A. Semyonov, A.D. Solopikhin, B.M. Shirokov // Вопросы атомной науки и техники. — 2005. — № 4. — С. 74-81. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS 81.40-WX; 61.66-DK https://nasplib.isofts.kiev.ua/handle/123456789/80559 Studies have been made into corrosion and mechanical properties of high-nickel alloys prepared at NSC KIPT on the basis of high-purity metal components. Corrosion tests of the Hastelloy-type alloy in fluoride melts at 650°C revealed formation of no films in the process of corrosion during 700 hours. The corrosion of the alloy under study in molten fluorides is characterized by a weak interaction of melt components with the alloy, by penetration of Zr and Na atoms into the alloy at a depth of 3 to 5 μm over 700 hours, by the absence of oxide films on the surface. The chromium content in the near-surface layer of the alloy decreases to a depth of 10 μm. Corrosion tests cause no essential changes in the mechanical properties of the alloy. Досліджувалися корозійні і механічні властивості зразків високонікелевих сплавів, які були виготовлені в ННЦ ХФТІ на основі високочистих металевих компонентів. В результаті корозійних випробувань сплаву типу Хастелой в розплаві фторидів при температурі 650°С не знайдено утворення яких-небудь плівок в процесі корозії протягом 700 г. Процес корозії цього сплаву в розплавах фторидів характеризується слабкою взаємодією компонентів суміші із сплавом, проникненням атомів Zr і Na в сплав на глибину до 3...5 мкм за час 700 г, відсутністю оксидних плівок на поверхні. Відбувається зменшення концентрації хрому в при поверхневому шарі сплаву на глибину до 10 мкм. Корозійні випробування не призводять до значної зміни механічних властивостей сплаву. Исследовались коррозионные и механические свойства образцов высоконикелевых сплавов, которые были изготовлены в ННЦ ХФТИ на основе высокочистых металлических компонентов. В результате коррозионных испытаний сплава типа Хастеллой в расплаве фторидов при температуре 650°С не обнаружено образования каких-либо плёнок в процессе коррозии в течение 700 ч. Процесс коррозии этого сплава в расплавах фторидов характеризуется слабым взаимодействием компонентов смеси со сплавом, проникновением атомов Zr и Na в сплав на глубину до 3…5 мкм за время 700 ч, отсутствием оксидных плёнок на поверхности. Происходит уменьшение концентрации хрома в приповерхностном слое сплава на глубину до 10 мкм. Коррозионные испытания не приводят к значительному изменению механических свойств сплава. This work was partially supported by the STCU, Project #294. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники The corrosion resistance of heatproof nickel alloy in molten fluoride salts Корозійна стійкість жароміцного нікелевого сплаву в розплавах фторидних солей Коррозионная стойкость жаропрочного никелевого сплава в расплавах фторидных солей Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
The corrosion resistance of heatproof nickel alloy in molten fluoride salts |
| spellingShingle |
The corrosion resistance of heatproof nickel alloy in molten fluoride salts Azhazha, V.M. Bakai, A.S. Bobrov, Yu.P. Virich, V.D. Yemlyaninova, T.G. Kapustin, V.L. Kovtun, K.V. Lavrinenko, S.D. Malykhin, D.G. Petel’guzov, I.A. Pylypenko, M.M. Savchenko, V.I. Semyonov, N.A. Solopikhin, A.D. Shirokov, B.M. |
| title_short |
The corrosion resistance of heatproof nickel alloy in molten fluoride salts |
| title_full |
The corrosion resistance of heatproof nickel alloy in molten fluoride salts |
| title_fullStr |
The corrosion resistance of heatproof nickel alloy in molten fluoride salts |
| title_full_unstemmed |
The corrosion resistance of heatproof nickel alloy in molten fluoride salts |
| title_sort |
corrosion resistance of heatproof nickel alloy in molten fluoride salts |
| author |
Azhazha, V.M. Bakai, A.S. Bobrov, Yu.P. Virich, V.D. Yemlyaninova, T.G. Kapustin, V.L. Kovtun, K.V. Lavrinenko, S.D. Malykhin, D.G. Petel’guzov, I.A. Pylypenko, M.M. Savchenko, V.I. Semyonov, N.A. Solopikhin, A.D. Shirokov, B.M. |
| author_facet |
Azhazha, V.M. Bakai, A.S. Bobrov, Yu.P. Virich, V.D. Yemlyaninova, T.G. Kapustin, V.L. Kovtun, K.V. Lavrinenko, S.D. Malykhin, D.G. Petel’guzov, I.A. Pylypenko, M.M. Savchenko, V.I. Semyonov, N.A. Solopikhin, A.D. Shirokov, B.M. |
| publishDate |
2005 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Корозійна стійкість жароміцного нікелевого сплаву в розплавах фторидних солей Коррозионная стойкость жаропрочного никелевого сплава в расплавах фторидных солей |
| description |
Studies have been made into corrosion and mechanical properties of high-nickel alloys prepared at NSC KIPT on the basis of high-purity metal components. Corrosion tests of the Hastelloy-type alloy in fluoride melts at 650°C revealed formation of no films in the process of corrosion during 700 hours. The corrosion of the alloy under study in molten fluorides is characterized by a weak interaction of melt components with the alloy, by penetration of Zr and Na atoms into the alloy at a depth of 3 to 5 μm over 700 hours, by the absence of oxide films on the surface. The chromium content in the near-surface layer of the alloy decreases to a depth of 10 μm. Corrosion tests cause no essential changes in the mechanical properties of the alloy.
Досліджувалися корозійні і механічні властивості зразків високонікелевих сплавів, які були виготовлені в ННЦ ХФТІ на основі високочистих металевих компонентів. В результаті корозійних випробувань сплаву типу Хастелой в розплаві фторидів при температурі 650°С не знайдено утворення яких-небудь плівок в процесі корозії протягом 700 г. Процес корозії цього сплаву в розплавах фторидів характеризується слабкою взаємодією компонентів суміші із сплавом, проникненням атомів Zr і Na в сплав на глибину до 3...5 мкм за час 700 г, відсутністю оксидних плівок на поверхні. Відбувається зменшення концентрації хрому в при поверхневому шарі сплаву на глибину до 10 мкм. Корозійні випробування не призводять до значної зміни механічних властивостей сплаву.
Исследовались коррозионные и механические свойства образцов высоконикелевых сплавов, которые были изготовлены в ННЦ ХФТИ на основе высокочистых металлических компонентов. В результате коррозионных испытаний сплава типа Хастеллой в расплаве фторидов при температуре 650°С не обнаружено образования каких-либо плёнок в процессе коррозии в течение 700 ч. Процесс коррозии этого сплава в расплавах фторидов характеризуется слабым взаимодействием компонентов смеси со сплавом, проникновением атомов Zr и Na в сплав на глубину до 3…5 мкм за время 700 ч, отсутствием оксидных плёнок на поверхности. Происходит уменьшение концентрации хрома в приповерхностном слое сплава на глубину до 10 мкм. Коррозионные испытания не приводят к значительному изменению механических свойств сплава.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/80559 |
| citation_txt |
The corrosion resistance of heatproof nickel alloy in molten fluoride salts / V.M. Azhazha, A.S. Bakai, Yu.P. Bobrov, V.D. Virich, T.G. Yemlyaninova, V.L. Kapustin, K.V. Kovtun, S.D. Lavrinenko, D.G. Malykhin, I.A. Petel’guzov, M.M. Pylypenko, V.I. Savchenko, N.A. Semyonov, A.D. Solopikhin, B.M. Shirokov // Вопросы атомной науки и техники. — 2005. — № 4. — С. 74-81. — Бібліогр.: 7 назв. — англ. |
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PACS 81.40-WX; 61.66-DK
THE CORROSION RESISTANCE OF HEATPROOF NICKEL ALLOY
IN MOLTEN FLUORIDE SALTS
V.M. Azhazha, A.S. Bakai, Yu.P. Bobrov, V.D. Virich, T.G. Yemlyaninova, V.L. Kapustin,
K.V. Kovtun, S.D. Lavrinenko, D.G. Malykhin, I.A. Petel’guzov, M.M. Pylypenko,
V.I. Savchenko, N.A. Semyonov, A.D. Solopikhin, B.M. Shirokov
National Science Center “Kharkov Institute of Physics and Technology”,
1 Akademicheskaya St., 61108 Kharkov, Ukraine
E-mail: azhazha@kipt.kharkov.ua
Studies have been made into corrosion and mechanical properties of high-nickel alloys prepared at NSC KIPT
on the basis of high-purity metal components. Corrosion tests of the Hastelloy-type alloy in fluoride melts at 650°C
revealed formation of no films in the process of corrosion during 700 hours. The corrosion of the alloy under study
in molten fluorides is characterized by a weak interaction of melt components with the alloy, by penetration of Zr
and Na atoms into the alloy at a depth of 3 to 5 μm over 700 hours, by the absence of oxide films on the surface. The
chromium content in the near-surface layer of the alloy decreases to a depth of 10 μm. Corrosion tests cause no es
sential changes in the mechanical properties of the alloy.
1. INTRODUCTION
The high-temperature homogeneous molten salt cold
graphite reactor (MSGR) that was under development in
the USA and the USSR [1-3] is one of the safe types of
nuclear reactors. Aside from power generation, the
reactor of this type is capable of realizing afterburning
and transmutation of spent nuclear fuel.
In the MSGR, the part of a coolant is played by
molten fluoride salts of lithium, sodium, zirconium with
addition of a fissile material, e.g., uranium or plutonium
fluoride. Heat-resistant and corrosion-resistant high-
nickel alloys are used as structural materials for the re
actor of this type. Among these alloys are the Hastelloy
N-type alloy and its Russian analog KhN80MT.
Using high-purity components as the base, Hastelloy
N-type alloys were smelted at the NSC KIPT; samples
from these alloys were prepared for performing corro
sion tests.
The aim of the present work has been to conduct
corrosion tests of the samples in molten fluoride salts of
zirconium and sodium.
2. MATERIALS AND INVESTIGATION
TECHNIQUES
The studies were performed on the samples of a
high-nickel alloy produced at NSC KIPT with the use of
high-purity metal components as the base. The alloy had
the following composition: Ni – base, Mo – 11.7,
Cr –6.7, Ti – 0.47, Al – 0.83, Fe – 1.5, Mn – 0.5,
Si – 0.15 wt.%. The high-purity initial components with
a low content of interstitial impurities, which were used
for preparing the alloy, were subjected to prerefining by
physical methods. The metal purification was performed
by different methods. For refining of nickel, molybde
num, niobium, titanium and iron, we have used the
method of vacuum electron-beam melting (EBM) at the
facility described in [4]. High-vacuum annealing was
used for refining of chromium and aluminum. Man
ganese was refined by the vacuum distillation technique.
For alloy smelting, we have used the method of in
duction melting of prepared stock in the argon atmo
sphere of the “Kristall-603” facility. At the end of the
process, a low-velocity casting into a water-cooled cop
per mold was performed. The resulting ingots were cut
with an electrospark discharge machine to have a pris
matic shape; then they were heated up to 900°C and
were rolled to a thickness of 1 and 0.3 mm with inter
mediate annealings. The rolled strips underwent the fol
lowing heat treatment: 1 – homogenizing annealing at
1100°C, a 1-hour exposure interval in air followed by
water quenching (after quenching the plate surface was
subjected to etching); 2 – after annealing the plates were
subjected to aging at 675°C during 5 hours in the argon
atmosphere [5, 6]. The samples for corrosion tests pre
sented the 27x23x1 mm plates cut out of the rolled strip
by means of the electrospark discharge machine. Before
the tests the sample surface was ground using the sand
paper with a grain size of 20 μm, the edges were blunt
ed.
Corrosion tests in air. Comparative corrosion tests
of both the given alloy and the reactor stainless steel
EhI-847 were conducted in air environment at tempera
tures of 650 and 750 C in the muffle furnace. The sam
ples were placed in alundum boats and were periodical
ly taken out for weighing on the microbalance VLR-20.
Tests in molten salts. The molten-salt
(50ZrF4+50NaF(mol.%)) test technique consisted in de
termining the degree of interaction between hastelloy
samples and molten salts with a long-term isothermal
holding in pyrocarbon ampoules. The tests were per
formed in the inert gas + high-purity argon environ
ment. The rate of interaction between the material and
the molten salts was estimated from mass variations de
termined by the analytical microbalance to an accuracy
of 0.05 mg [7]. Metallographic methods and secondary-
ion mass-spectrometry technique were used to investi
_______________________________________________________________________________
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2005. №.4.
Серия: Физика радиационных повреждений и радиационное материаловедение (87), с. 74-81.
74
mailto:azhazha@kipt.kharkov.ua
gate the sample surfaces. Mechanical properties of the
samples were also investigated. The device for tests in
the salt composition includes the pressurized chamber
equipped with a system pumping to a vacuum of 1ּ10-2
mm Hg, the device for filling the chamber volume with
argon from a vessel and the manometers for pressure
measurements (see Fig. 1).
Fig. 1. Schematic of the setup for corrosion tests of Hastelloy-type alloy samples in molten fluoride salts in graphite
ampoules: 1 – pyrocarbon ampoules with molten salts; 2 – sample mount, 3 – safety valve; 4 - vacuum chamber
body; 5 – heating furnace, 6 – thermocouple, 7 – manometer, 8 – vacuum pumping and gas inlet system, 9 – frame
The container with pyrocarbon ampoules and sam
ples was placed into the furnace TG-1 with a heater.
The furnace was equipped with the instrumentation to
maintain the assigned temperature, to measure and reg
ister its values. Before the experiment, the sample sur
face was degreased in gasohol, and after drying, the
samples were weighed on the analytical balance. Then
the samples were put into pyrocarbon ampoules, which
were filled in a special chamber with a molten salt mix
ture at a temperature of ~550°C in the argon medium.
The cross section of the ampoule filled with a solidified
melt of fluorides is given in Fig. 2.
Fig. 2. The ampoule filled with solidified molten fluo
rides is section:1 – solidified molten salts; 2 – pyrocar
bon ampoule; 3 – alloy sample
The filled ampoules were closed by threaded covers.
As the ampoules were put into the working chamber, the
latter was twice pumped out to vacuum and was
“washed” by argon. Then, in the argon atmosphere
(1.2 MPa), the samples were heated and held at a tem
perature of 650°C in the molten salts during 100, 200,
500 and 700 hours. On opening the ampoules, the alloy
samples were taken out, the salt remains were removed
from their surface, the samples were weighed, their mi
crostructure and mechanical properties were investigat
ed; the X-ray diffraction analysis was also performed
and variations in the chemical composition in the sam
ple depth were studied.
The microstructure of samples was examined with
the metallography microscope MMR-4. The chemical
composition variations in the depth of the sample were
investigated by the secondary-ion mass-spectrometry
method using the MS-7201 device.
The X-ray diffraction studies of alloys were made at
the DRON4-07 facility with the scintillation counter in
the radiation of CuKα and CopKα.. The reflections were
obtained using the Bragg-Brentano optical scheme. The
morphology of sample surface after corrosion was
examined in the electron-scan microscope
REMMA-200.
The chemical composition of the salt that underwent
corrosion tests was analyzed by the mass-spectrometer
EhMAL-2. The tensile testing machine of type 1246R-
2/2600 was used to investigate the mechanical
properties of alloys in the temperature range from 20 to
650˚C.
3. RESULTS AND DISCUSSION
The kinetic curves showing the increase in weight of
high-nickel alloy and stainless steel samples versus time
at oxidation in air during 660 h are shown in Fig. 3. It
can be seen that the process of corrosion of the Hastel
loy-type alloy at 650˚C has a damped character, and this
gives evidence for the protective mechanisms of the oxi
dation process. The rate of alloy oxidation is rather low.
If it is assumed that the protective oxide film consists of
NiO and Cr2O3 in the 50:50% ratio, then its thickness
estimated from the sample increase in weight during
660 h will make only 1.74 μm. No delamination or flak
ing off of oxide films was observed. The rise in the oxi
dation temperature up to 750˚C for the Hastelloy-type
alloy also gives moderate oxidation rates; the curves of
the oxidation process show the damped character. The
thickness of oxide films formed during 700 h at 750˚C
is calculated to be approximately 6 μm.
The oxidation rate of stainless steel EI-847 is appre
ciably higher than that of the Hastelloy-type alloy at the
two test temperatures. The calculations of the thickness
of oxide films on steel at 650˚C show it to be 7.7 μm af
ter 660 hours of tests, while at 750˚C the 7 to 8 μm film
thickness is attained as early as in 100 h. So, our Hastel
loy-type alloy [5] is a highly corrosion-resistant material
that may be used in different fields of engineering.
The variation in the sample mass with time of hold
in the molten salts is shown in Fig. 4. It is seen that this
variation has an irregular character: at first, we observe
an enhanced increase in weight for up to 250 hours of
tests, and then it gradually falls off at subsequent tests
during 700 hours. Evidently, this behavior reflects the
complicated kinetics of interaction between fluoride
salts and the Hastelloy-type alloy. Figure 5 shows the
appearance of the samples (upper row, 1.3 x magnifica
tion) and morphological peculiarities of the sample sur
face after corrosion tests in the salt mixture during
100…700 hours (500 x magnification). The optical mi
croscopy examination of the surface has revealed the is
lands of loose formations that may be the result of inter
action between the molten salts and the alloy. These for
mations could not be removed by vacuum annealing at
650°C. Their presence is probably one of the reasons
that accounts for the increase in weight.
Fig. 3. Comparison between increases in weight for Hastelloy-type alloy and stainless steel EI 847
at oxidation in air
0
0,02
0,04
0,06
0,08
0 200 400 600 800
Test duration, h
In
cr
ea
se
in
w
ei
gh
t,
m
g/
cm
2
Fig. 4. Time dependence of the increase in weight for the Hastelloy-type alloy samples held in the salt melt at 650°C
а
b
100 h 200 h 500 h 700 h
Fig. 5. The appearance of samples and morphological peculiarities of the surface after corrosion tests
in the salt melt during 100 to 700 hours: a – appearance of samples (1.3 x magnification); b - morphological pecu
liarities of sample surfaces (500 x magnification)
Figure 6 shows the microstructure of sample edges
after corrosion tests during 100 and 700 hours in the
plane perpendicular to rolling. No noticeable signs of
intercrystalline corrosion were observed on the samples.
The average grain size in the alloy samples is dependent
on the time of staying in the salt melt and is found to be
11, 12.6, 14 and 21 μ after 100, 200, 500 and 700 hours
of corrosion tests, respectively. Figure 7 shows the mi
crostructure of samples after corrosion tests in molten
salts at 650°C during 100, 200, 500 and 700 hours. The
metallographic section surface lies in the plane of
rolling.
The mechanical properties of samples after the cor
rosion tests are presented in Table 1. It is obvious that
they remain practically unchanged with increasing time
of holding in the molten salts.
Fig. 6. Microstructure of Hastelloy-type alloy samples after corrosion tests at 650°C during 100 and 700 hours.
(380 x magnification)
100 hours 700 hours
100 hours 200 hours
500 hours 700 hours
Fig. 7. Microstructure of samples after corrosion tests in molten salts at 650˚C during 100, 200, 500 and 700 hours.
The scale interval is 10 μm
Table 1
Data from mechanical tests (T = 25, 450 and 650°C) of Hastelloy-type alloy samples
subjected to corrosion at 650°C during 100, 200, 500 and 700 hours
Test duration, h Тtest, °С σВ, МPа σ0,2, МPа δ, %
Initials
100
200
500
700
25
930 430 60
1100 840 41
1080 810 45
1080 890 43
1070 875 43
Initials
100
200
500
700
450
710 314 62
800 400 50
800 450 50
820 450 50
800 460 50
Initials
100
200
500
700
650
397 288 14
502 420 8,0
510 435 8,7
490 420 10,0
510 440 9,0
The secondary-ion mass-spectrometry method was
used to investigate the surface composition of the initial
alloy sample and the element distribution in the depth of
the sample after corrosion tests. A typical spectrum of
secondary ions is shown in Fig. 8, where it is seen that
the spectrum has all the elements (including isotopes)
entering into the alloy composition. To perform quanti
tative analysis, we have normalized the peak amplitudes
of individual elements in conformity with the chemical
analysis data. This method enables one to perform the
layer-by-layer analysis of the chemical composition of
the alloy, to determine variations in the element concen
tration versus the thickness of the layer taken off the al
loy surface.
Figure 9 shows the spectrum of secondary ions from
the sample that underwent corrosion tests in the salt
melt at 650°C during 100 hours. The main difference
between the two spectra (see Figs. 8 and 9) is that the
second spectrum exhibits a large peak of sodium of
mass 23, and also peaks of concomitant masses 39 and
40 (NaO, NaOH), which are proportional to the peak
value of sodium; and the peaks of masses 90, 91, 92, 94
and 96 associated with zirconium isotopes and of con
comitant masses, e.g., 106 (corresponds to 90Zr16O).
Fig. 8. Typical spectrum of secondary ions from the ini
tial Hastelloy-type alloy sample
Fig. 9. Typical spectrum of secondary ions from the ini
tial Hastelloy-type alloy sample after staying in the melt
of sodium and zirconium fluorides at 650°C
during 100 hours
Since they partially overlap with the peaks of
molybdenum isotopes, the 90Zr isotope was taken as the
basis of measurements (the percentage of this isotope
makes 51.46%). Note also the presence of an insignifi
cant peak of fluorine (mass 19) in the second spectrum.
The peaks corresponding to the fluorides NaF, ZrF4
were not observed. The samples that underwent corro
sion tests were studied to determine the distribution of
the main constituents of the Hastelloy-type alloy: nickel
(masses 60 and 58), molybdenum (main isotope of mass
98), chromium (main isotope of mass 52), titanium
(main isotope of mass 48), aluminum of mass 27.
It is obvious that after corrosion tests the salt be
comes enriched with practically all metals entering into
the alloy composition. Figures 10 and 11 show the dis
tributions of titanium and chromium concentrations in
the depth of the sample, determined by the secondary-
ion emission technique. It can be seen from Fig. 10 that
titanium is not practically “washed out” of the sample
surface; on the contrary, its concentration increases in
the near-surface layer (3 to 10 μm). It is the chromium
concentration that is most strongly affected. As it is ob
vious form Fig. 11, after corrosion tests chromium is
washed out from the sample surface to a depth of
~ 10 μm).
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
0 2 4 6 8 10
depth, mcm
co
nc
en
tr
at
io
n,
m
as
.%
Fig. 10. Titanium concentration variation in the depth
of the Hastelloy-type alloy sample after corrosion tests
in the molten salts at 650°C during 500 hours. The
dashed line shows the initial titanium concentration in
the alloy. Separate measurements (shown by squares)
are connected by lines for better visualization
Fig. 11. Chromium concentration variation in the depth
of the Hastelloy-type alloy sample after corrosion tests
in molten salts at 650°C over different periods of time.
The dashed line shows the initial chromium concentra
tion in the alloy
The distributions of sodium and zirconium in the
depth of the sample held in the salt melt over different
periods of time are given in Fig. 12.
It can be seen that as a result of corrosion in the melt
of sodium and zirconium fluorides, the penetration of Cr
and Zr inside the alloy occurs to a depth of 5 μm.
Chemical analysis of both the initial salt melt and
the melt subjected to corrosion tests was performed by
the method of laser mass-spectrometry. Table 2 gives
the concentrations of titanium, chromium, manganese,
iron, nickel and molybdenum in the initial melt of sodi
um and zirconium fluorides and in the same melt after
holding there Hastelloy-type alloy samples at 650°C
during 500 hours. These data confirm the results pre
sented in Figs. 10 and 11.
We performed the phase analysis of the Hastelloy-
type alloy after corrosion tests in the NaF-ZrF4 environ
ment at 650°C during 100, 200, 500 and 700 hours. The
coolant is based on 7NaF∙6ZrF4. The results of the anal
ysis are presented in Tables 3 and 4.
According to the data of Table 4, the samples that
underwent corrosion tests exhibit the phase Ni3Al(Ti)
with a cubic lattice. It is accompanied by the presence
of other-stoichiometry compounds NiAl and Ni2Al3. The
Ni3Mo compounds were also observed.
The 100-hour exposure gave rise to weak lines at the
bottom of the nickel base line (111), which correspond
to nickel-aluminum and nickel-molybdenum com
pounds: NiAl (2θ = 44.6, d = 2.032 Ǻ) and
Ni3Mo (2θ = 42.8, d = 2.113 Ǻ). Beginning with the
200-hour exposure, traces of NiCr appear. Aside from
nickel-containing intermetallides, the sample surfaces
also show the traces of the coolant with a crystal struc
ture corresponding to 7NaF∙6ZrF4.
The second phases manifest themselves most clearly
on the sample subjected to the 500-hour exposure. In
this case, the sample shows only the Ni3(Al, Ti) phase.
0
200
400
600
800
1000
1200
0 5 10
depth, mcm
c
on
ce
nt
ra
tio
n,
a
rb
.u
n.
90-Zr(500)
90-Zr(700)
90Zr200)
90Zr(100)
0
500
1000
1500
2000
0 5 10
depth, mcm
co
nc
en
tr
at
io
n,
a
rb
.u
n.
23-
Na(700)
23 -
Na(500)
23Na(20
0)
a b
Fig. 12. Element distribution in the depth of the sample after different time periods of staying in the salt melt:
a – zirconium; b – sodium
Table 2
Variations in the content of metal impurities in molten salts after corrosion tests at 650°C for 500 hours
Melt
Impurity content, wt. %
Ti Cr Mn Fe Ni Mo
Initial <0,0005 0,0039 <0,0005 0,021 0,0031 <0,004
After corrosion 0,007 0,15 0,01 0,21 0,05 0,015
Table 3
Conditional numeration of phases given in Table 4
Phase No Phase
1
2
3
4
5
6
Ni3Al(Ti)
NiAl
Ni2Al3
Ni3Mo
NiCr
7NaF⋅6ZrF4
Table 4
Phase analysis data for alloy A after corrosion tests at 650°C during 100…700 hours
d(Е) Phase No
(see Table 3)
Line intensity (%)1
100 h 200 h 500 h 700 h
3.66
3.175
3.10
2.856
2.549
2.33…2.36
2.222
≤ 2.112
≥ 2.032
1.953
1.914
1.888
≤ 1.842
≥ 1.822
1.616
1(3)
6
6
2,3,(6)
1
5
4
4
2,3,5
4
6
5
1
1
1
1.5
1.5
–
1.0
1.0
–
0.5
≥ 3.0
≥ 4.0
0.5
–
–
–
≥ 1.5
1.0
–
2.5
–
1.5
1.0
1.0
5.0
≥ 5.0
≥ 5.0
–
–
–
–
≥ 4.0
–
–
1.0
3.0
–
2.5
0.5
–
≥ 5.0
?
0.5
0.5
2.5
–
≥ 2.0
1.5
–
2.0
–
1.0
1.0
6.0
–
≥ 4.0
≥ 3.5
1.0
–
–
≥ 1.0
–
–
Presence of phases No 1–4, 6 1–6 1, 4–6 1–5, (6)
1The nickel-base line (111) intensity is taken for 100%.
2 Lines at the bottom of lines (111) and (200) of the nickel base.
4. CONCLUSIONS
1. Kinetics of Hastelloy-type alloy oxidation in air
at temperatures of 650 and 750°C has been in
vestigated. It is found that at oxidation in air the
alloy under study is distinguished for its high
corrosion resistance superior to the corrosion re
sistance of steel EI-847. A protective oxide
film, up to 1.5 μ in thickness, is formed on the
alloy at a temperature of 650°C for 660 hours.
2. The corrosion tests of the Hastelloy-type alloy
in the melt of fluorides at 650°C have not re
vealed any formation of films during a 700-hour
corrosion.
3. The process of corrosion of the Hastelloy-type
alloy in molten zirconium and sodium fluorides
is characterized by weak interaction of melt
components with the alloy, by penetration of Zr
and Na atoms into the alloy to a depth of 3 … 5
μm over a period of 700 hours, by the absence
of oxide films on the surface. A decrease of
chromium concentration in the near-surface lay
er of the alloy to a depth of ~ 10 μm occurs.
4. The present corrosion tests have caused no es
sential changes in the mechanical properties of
the alloy.
5. The samples that underwent corrosion tests have
exhibited the Ni3Al(Ti) phase with a cubic lat
tice. Along with this phase, other-stoichiometry
compounds NiAl and Ni2Al3 were present. The
Ni3Mo compounds and the traces of the NiCr
phase were also observed.
This work was partially supported by the STCU,
Project #294.
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2.V.M. Novikov, V.V. Ignatyev, V.I. Fedulov,
V.N. Cherednikov. Molten-salt NEF: prospects and
problems (in Russian). Moscow: “Ehnergoizdat”, 1990,
192 p.
3.U.R. Grims. Problems of materials choice for
molten-salt reactors (Russian translation). Moscow:
“Atomizdat publ.” 1966, p. 69–98.
4.V.M. Azhazha, Yu.P. Bobrov, V.D. Virich, et al. Re
finement of nickel by electron-beam melting (in Rus
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particles, fields”. 2003, N601, is. 2(22), p. 118–122.
5.V.M. Azhazha, Yu.P. Bobrov, P.N. V’yugov, et al.,
Development of the alloy for the fuel loop of molten-
salt reactors (in Ukrainian) //Kharkov University Bul
letin. Ser. phys.: “Nuclei, particles, fields”. 2004, is.
1(23), p. 87–94.
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al., Alloys for molten-salt reactors (in Ukrainian) //Pro
ceedings of the XVI International conference on physics
of radiation phenomena and radiation materials sci
ence. 6 – 11 September, 2004, Alushta, Crimea, NSC
KIPT, p. 271–272.
7.V. Azhazha, A. Bakai, Yu. Bobrov, S. Lavrinenko,
I. Petel’guzov, V. Savchenko. Investigation of corrosion
resistance and mechanical properties of high-tempera
ture heat-resistant nickel alloy (in Russian) //Fracture
mechanics of materials and structural strength. Ed. by
V.V. Panasyuk. L’viv, G.V. Karpenko Institute for
Physics and Mechanics, National Academy of Sciences
in Ukraine, 2004, p. 659–664.
КОРРОЗИОННАЯ СТОЙКОСТЬ ЖАРОПРОЧНОГО НИКЕЛЕВОГО СПЛАВА
В РАСПЛАВАХ ФТОРИДНЫХ СОЛЕЙ
В.М. Ажажа, А.С. Бакай, Ю.П.Бобров, В.Д. Вирич, Т.Г. Емлянинова, В.Л. Капустин,
К.В. Ковтун, С.Д. Лавриненко, Д.Г. Малыхин, И.А. Петельгузов, Н.Н. Пилипенко,
В.И. Савченко, Н.А. Семенов, А.Д. Солопихин, Б.М. Широков
Исследовались коррозионные и механические свойства образцов высоконикелевых сплавов, которые были изготов
лены в ННЦ ХФТИ на основе высокочистых металлических компонентов. В результате коррозионных испытаний спла
ва типа Хастеллой в расплаве фторидов при температуре 650°С не обнаружено образования каких-либо плёнок в процес
се коррозии в течение 700 ч. Процесс коррозии этого сплава в расплавах фторидов характеризуется слабым взаимодей
ствием компонентов смеси со сплавом, проникновением атомов Zr и Na в сплав на глубину до 3…5 мкм за время 700 ч,
отсутствием оксидных плёнок на поверхности. Происходит уменьшение концентрации хрома в приповерхностном слое
сплава на глубину до 10 мкм. Коррозионные испытания не приводят к значительному изменению механических свойств
сплава.
КОРОЗІЙНА СТІЙКІСТЬ ЖАРОМІЦНОГО НІКЕЛЕВОГО СПЛАВУ
В РОЗПЛАВАХ ФТОРИДНИХ СОЛЕЙ
В.М. Ажажа, О.С. Бакай, Ю.П. Бобров, В.Д. Віріч, Т.Г. Емлянінова, В.Л. Капустін,
К.В.Ковтун, С.Д. Лавриненко, Д.Г. Малихін, І.А. Петельгузов, М.М. Пилипенко,
В.І. Савченко, М.О. Семенов, А.Д. Солопихін, Б.М. Широков
Досліджувалися корозійні і механічні властивості зразків високонікелевих сплавів, які були виготовлені в ННЦ
ХФТІ на основі високочистих металевих компонентів. В результаті корозійних випробувань сплаву типу Хастелой в
розплаві фторидів при температурі 650°С не знайдено утворення яких-небудь плівок в процесі корозії протягом 700 г.
Процес корозії цього сплаву в розплавах фторидів характеризується слабкою взаємодією компонентів суміші із сплавом,
проникненням атомів Zr і Na в сплав на глибину до 3...5 мкм за час 700 г, відсутністю оксидних плівок на поверхні. Від
бувається зменшення концентрації хрому в при поверхневому шарі сплаву на глибину до 10 мкм. Корозійні випробуван
ня не призводять до значної зміни механічних властивостей сплаву.
|