Air-thermal oxidation of zirconium materials
The results of the temperature effect on the process of oxide films formation on the surface of the zirconium materials are given. The changes of the morphology, structure and properties of the oxide films on the zirconium and Zr1%Nb alloy due to exposure of heat treatment in air at 500…800 ºС for...
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| Cite this: | Air-thermal oxidation of zirconium materials / M.M. Pylypenko, A.A. Drobyshevskaya, Yu.S. Stadnik, I.G. Tantsyura // Вопросы атомной науки и техники. — 2014. — № 2. — С. 103-106. — Бібліогр.: 9 назв. — англ. |
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Pylypenko, M.M. Drobyshevskaya, A.A. Stadnik, Yu.S. Tantsyura, I.G. 2015-04-09T12:59:29Z 2015-04-09T12:59:29Z 2014 Air-thermal oxidation of zirconium materials / M.M. Pylypenko, A.A. Drobyshevskaya, Yu.S. Stadnik, I.G. Tantsyura // Вопросы атомной науки и техники. — 2014. — № 2. — С. 103-106. — Бібліогр.: 9 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/79969 669.296 The results of the temperature effect on the process of oxide films formation on the surface of the zirconium materials are given. The changes of the morphology, structure and properties of the oxide films on the zirconium and Zr1%Nb alloy due to exposure of heat treatment in air at 500…800 ºС for a time up to 10 h are analyzed. Приведены результаты исследований влияния температуры на процесс образования оксидных пленок на поверхности циркониевых материалов. Проанализированы изменения морфологии, структуры и свойств оксидных пленок на цирконии и сплаве Zr1%Nb в результате воздействия термической обработки в воздуш- ной среде при 500…800 ºС в течение 10 ч. Приведено результати досліджень впливу температури на процес утворення оксидних плівок на поверхні цирконієвих матеріалів. Проаналізовано зміни морфології, структури і властивостей оксидних плівок на цирконії та сплаві Zr1%Nb в результаті впливу термічної обробки в повітряному середовищі при 500…800 ºС протягом 10 год. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Материалы реакторов на тепловых нейтронах Air-thermal oxidation of zirconium materials Воздушно-термическое окисление циркониевых материалов Повітряно-термічне окислення цирконієвих матеріалів Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| title |
Air-thermal oxidation of zirconium materials |
| spellingShingle |
Air-thermal oxidation of zirconium materials Pylypenko, M.M. Drobyshevskaya, A.A. Stadnik, Yu.S. Tantsyura, I.G. Материалы реакторов на тепловых нейтронах |
| title_short |
Air-thermal oxidation of zirconium materials |
| title_full |
Air-thermal oxidation of zirconium materials |
| title_fullStr |
Air-thermal oxidation of zirconium materials |
| title_full_unstemmed |
Air-thermal oxidation of zirconium materials |
| title_sort |
air-thermal oxidation of zirconium materials |
| author |
Pylypenko, M.M. Drobyshevskaya, A.A. Stadnik, Yu.S. Tantsyura, I.G. |
| author_facet |
Pylypenko, M.M. Drobyshevskaya, A.A. Stadnik, Yu.S. Tantsyura, I.G. |
| topic |
Материалы реакторов на тепловых нейтронах |
| topic_facet |
Материалы реакторов на тепловых нейтронах |
| publishDate |
2014 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Воздушно-термическое окисление циркониевых материалов Повітряно-термічне окислення цирконієвих матеріалів |
| description |
The results of the temperature effect on the process of oxide films formation on the surface of the zirconium materials
are given. The changes of the morphology, structure and properties of the oxide films on the zirconium and
Zr1%Nb alloy due to exposure of heat treatment in air at 500…800 ºС for a time up to 10 h are analyzed.
Приведены результаты исследований влияния температуры на процесс образования оксидных пленок на
поверхности циркониевых материалов. Проанализированы изменения морфологии, структуры и свойств
оксидных пленок на цирконии и сплаве Zr1%Nb в результате воздействия термической обработки в воздуш-
ной среде при 500…800 ºС в течение 10 ч.
Приведено результати досліджень впливу температури на процес утворення оксидних плівок на поверхні
цирконієвих матеріалів. Проаналізовано зміни морфології, структури і властивостей оксидних плівок на цирконії та сплаві Zr1%Nb в результаті впливу термічної обробки в повітряному середовищі при 500…800 ºС
протягом 10 год.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/79969 |
| citation_txt |
Air-thermal oxidation of zirconium materials / M.M. Pylypenko, A.A. Drobyshevskaya, Yu.S. Stadnik, I.G. Tantsyura // Вопросы атомной науки и техники. — 2014. — № 2. — С. 103-106. — Бібліогр.: 9 назв. — англ. |
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2025-11-24T05:51:46Z |
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2025-11-24T05:51:46Z |
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1850842000996171776 |
| fulltext |
ISSN 1562-6016. ВАНТ. 2014. №2(90) 103
UDC 669.296
AIR-THERMAL OXIDATION OF ZIRCONIUM MATERIALS
M.M. Pylypenko, A.A. Drobyshevskaya, Yu.S. Stadnik, I.G. Tantsyura
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
E-mail: mpylypenko@kipt.kharkov.ua
The results of the temperature effect on the process of oxide films formation on the surface of the zirconium ma-
terials are given. The changes of the morphology, structure and properties of the oxide films on the zirconium and
Zr1%Nb alloy due to exposure of heat treatment in air at 500…800 ºС for a time up to 10 h are analyzed.
INTRODUCTION
Modern nuclear power engineering is based on reac-
tors in which the most important elements of active
zone are made from zirconium alloys. Widespread use
of alloys based on zirconium is caused by its good phys-
ical and mechanical properties (low thermal neutron
capture cross section, high melting temperature, plastic-
ity, good corrosion resistance).
The corrosion resistance of zirconium alloys is
caused by the formation on the surface of a dense oxide
film which slows further oxidation. Oxidation of zirco-
nium alloys has been studied for a long time and a good
understanding of the processes for high temperature
conditions in oxidizing environments has been achieved
[1-6]. However discussion about the role of various
physical processes that affect the growth rate of oxide
films and corrosion regimes still continues.
Currently established that features of kinetics of cor-
rosion zirconium materials explained by changes occur-
ring in the oxide films during their growth and degrada-
tion. It is important to find correlation between the char-
acteristics of the oxide films formed on the alloys dur-
ing corrosion and their protective action in order to pre-
dict the corrosion behavior of zirconium materials under
actual operating conditions.
Purpose of work is study the influence of air-thermal
oxidation on the growth kinetics, surface structure and
mechanical properties of the oxide films formed on the
samples of zirconium and Zr1%Nb alloy.
MATERIALS AND METHODS
As the samples for research the plates of zirconium
and Zr1%Nb alloy size 15 × 15 × 1 mm were used.
For obtaining a protective oxide film the prepared
samples were subjected to air-thermal oxidation in the
laboratory electric resistance furnace at temperatures of
500…800 °С with weighting at the beginning and end
of the test on the microanalytical scales VLR-200 accu-
rate to 0.5 mg after which their mechanical and corro-
sion properties were investigated. Holding time of sam-
ples in the specified temperature range is from several
minutes to 10. Evaluation parameters of corrosion prop-
erties of the samples were: characteristic of surface
(denseness, color uniformity of oxide films) and the
corrosion rate which determined by the sample weight
gain per unit surface over the test period.
The surface structure of the obtained films and their
elemental composition were investigated by the auto-
emission scanning electron microscope JSM-7001F
with energy dispersive microanalysis system INCA En-
ergy 350. The microstructure of the samples was studied
by standard metallographic method on optical micro-
scope MMP-4. The thickness of the oxide film on the
oxidized samples was determined by fractography im-
ages of the fractures using a scanning electron micro-
scope FEI Quanta 600 FEG. Microhardness measure-
ments were carried out on the device PMT-3 with load
of 100 g, the Brinell hardness (HB) was determined
with load of 1000 kg on the device TSh-2.
To measure the roughness parameters of the surface
of samples the portable profilometer-profilograph
TR200 production of the company Time Group Inc was
used by which the magnitude of Ra (average arithmetic
roughness surface according to international standard
ISO 4287) was determined.
RESULTS AND DISCUSSION
To determine the regularities of relief and structure
formation of zirconium and Zr1%Nb alloy due to ther-
mal influence the electron microscopic studies on the
oxidized samples have been made.
After oxidation in air at 500 °С for samples of
Zr1%Nb alloy a structure typical for a deformed mate-
rial is observed. As a result of oxidation at 600 °С solid
black oxide film without cracks is appeared (Fig. 1,a).
Such morphological structure of the coating indicates a
good quality of sample. At 700 °С thickness of the ox-
ide film is increased, there are small cracks and whitish
layer. At 800 °С inhomogeneous structure with some
separation on fragments is formed (see Fig. 1,b).
Samples of pure zirconium after oxidation at 500 °С
are covered with glossy film of homogeneous structure.
At increasing the annealing temperature to 600 °С sig-
nificant changes in the external and structural view is
not noted. Any defects in the oxide films or their flaking
are not observed. The films in this temperature range are
firmly engaged with the sample surface. On the plates
annealed at 800 °С white oxide film is formed, already
cracks with clear boundaries are seen (see Fig. 1,c). It is
obvious that a coating with such morphological charac-
teristics cannot provide effective protection of the sur-
face.
104 ISSN 1562-6016. ВАНТ. 2014. №2(90)
а b c
Fig. 1. Surface morphology of the Zr1%Nb alloy (а, b) and Zr (c) after oxidation for 8 h
at 600 °С (а) and 800 °С (b, c)
At complex study of functional oxide coatings on
zirconium materials it has been found temperature effect
of air-thermal oxidation on morphology and composi-
tion of the modified surfaces. At temperature up to
600 °С durable black oxide film of uniform structure is
formed on the surface of the zirconium and its alloy.
Further increase of temperature to 800 °С leads to an
increase in the oxygen content and the oxide film
growth (Table). With increasing thickness of the oxide
film the mechanical stresses at the border oxide-metal
are increased and therefore a sharp change in corrosion
resistance is observed [7]. Long-term oxidation times
and higher oxidation temperatures violate the coating
integrity. Formation of cracks and destruction of the
oxide film occurs.
Except the temperature and duration of the process
[8] also the chemical composition has a significant im-
pact on the structure of the oxide layer. Composition of
oxide films affects on their mechanical and protective
properties since a dense solid oxide film can protect the
metal from further oxidation. In the study of the oxida-
tion process it was found that for pure zirconium and
zirconium doped with niobium onset temperature of
cracking of the oxide film is different. After annealing
at 500…600 °С all samples were covered with continu-
ous glossy film. At 800 °С for Zr1%Nb alloy an inho-
mogeneous structure with some separation into frag-
ments is formed while for pure zirconium cracks are
clearly visible due to the formation of smaller amounts
of the tetragonal phase in the oxide layer (see
Fig. 1,b,c). Due to the low volume fraction of tetragonal
oxide a fracture toughness of the oxide layer becomes
much lower therefore the oxide layer is susceptible to
microcracks and loses its protective structure [9]. In the
structure of Zr1%Nb alloy after oxidation the presence
of a significant amount of a light tetragonal phase is
observed so the formation of cracks in the oxide layer
occurs not as intensively as in the case of pure zirco-
nium.
The minimum film thickness which is necessary for
the protection and stabilization of metal corrosion proc-
ess depends on many factors: temperature, chemical
composition and structure, the manufacturing process
and preparation of the sample surface, etc. Oxidation
kinetics of zirconium materials was determined by peri-
odic weighing samples. It was found that with increas-
ing holding time the weight gain of sample increases
and significantly depends on temperature. From the
results of studies follows that the oxidation rate of the
zirconium materials continuously increases with in-
creasing thickness of the film formed. The highest in-
tensity of the weight gain of samples occurs at a tem-
perature of 800 °С as shown in Table.
Corrosion behavior of zirconium materials is deter-
mined by properties of the barrier oxide film. The
growth of the oxide film under isothermal conditions in
the temperature range studied is not subject to any one
law and cannot be described by one kinetic equation. At
certain temperatures the transition from one to another
oxidation law is observed. In the oxidation of zirconium
materials there are several stages [3-4].
Growth of the oxide film in the temperature range
500…600 °С occurs according to a parabolic or cubic
law up to oxide thickness of 2…3 μm. The inner part of
the film is nonstoichiometric, the outer part is close to
the stoichiometric composition. Such oxide film is an
effective protective barrier for oxidation. According to a
parabolic law a rate of the oxidation process is inversely
proportional to the thickness of the oxide film. This law
applies when on the metal surface during its oxidation a
film which has protective properties is formed, i.e. it is
solid and nonporous.
With further growth of the oxide film thickness
more than 3 μm the growth kinetics is replaced by qua-
silinear. At temperatures above 700 °С corrosion rate
increases sharply. This oxidation stage is characterized
by rapid oxidation and a large number of oxide film
defects such as cracks and pores (Fig. 2). Transition
from the protective oxide film to the peelable film oc-
curs for relatively short time after which zirconium and
Zr1%Nb alloy are oxidized with increased rate to com-
plete destruction.
The research results of oxide films formed on the
surface of zirconium samples showed that growth proc-
ess of the oxide film thickness depends on the holding
time and heating temperature. Furthermore as seen from
Fig. 2 at the same temperature of 800 °С thickness of
oxide film formed during corrosion on an alloy almost 2
times less than the thickness of the film on pure zirco-
nium. This fact is explained by the presence in the alloy
of niobium which stabilizes the corrosion resistance of
undoped zirconium that is eliminates the adverse effect
of small amounts of impurities present in pure zirco-
nium [4]. It is known that the doping of zirconium may
significantly reduce the oxidation rate after transition
[7].
ISSN 1562-6016. ВАНТ. 2014. №2(90) 105
a b
c d
Fig. 2. Fractography images of the fractures of the samples of zirconium (a, b) and Zr1%Nb alloy (c, d)
at 700 °С (a, c) and 800 °С (b, d)
Roughness parameter Ra of the oxide film formed at
a temperature up to 600 °С is not more than 0.1 μm.
When tested of zirconium materials in more severe con-
ditions (raised temperature) a thicker oxide film is
formed, roughness is increased (see Table).
The value of Brinell hardness is increased from
2500 MPa for the initial samples Zr1%Nb alloy to
2770 MPa for all samples after oxidation. The micro-
hardness values of the samples after oxidation at differ-
ent temperatures of heating and times of annealing are
significantly different. The measurement results show
that with rising temperature microhardness is increased.
The microhardness values for zirconium plates as well
as the results of determining the amount of oxygen,
weight gain, roughness and thickness of the samples are
shown in Table.
Oxygen content, weight gain (Δm), roughness (Ra), thickness (h) and microhardness (Hμ) of oxide films
formed on zirconium samples
Samples Values Zr Zr1%Nb
T, °С 600 700 800 600 700 800
t, h 8 10 8 8 10 8
O2, wt.% 22.7 26.2 32 23.13 24.5 26.17
Δm, mg 4.1 43.9 62.9 4.4 15.95 51.7
Ra, μm 0.072 0.270 1.981 0.100 0.632 1.848
h, μm 3.3 12.12 84.18 2.2 17.75 47.75
Hμ, MPa 3720 7340 7880 5190 8240 8350
It should be noted that despite the fact that the corro-
sion is the destructive process the formation of the
dense oxide films on the surface of zirconium materials
may lead to positive effects due to creation of the pro-
tective barrier on the path of further degradation of ma-
terial. In order to have protective properties the oxide
film must fulfill the following requirements: be solid,
nonporous, chemically inert to the aggressive environ-
ment, have high hardness, wear resistance, adhesion to
metal.
Thus the choice of optimal temperature and time of
oxidation allows to create on the surface of zirconium
materials the dense oxide films. The protective oxide
film of a certain thickness and perfect structure (no
cracks, pores) on the surface of zirconium and alloy
Zr1%Nb prevents further penetration of the corrosive
106 ISSN 1562-6016. ВАНТ. 2014. №2(90)
environment in the deeper layers and therefore protects
the metal from further destruction.
CONCLUSIONS
It is shown that air-thermal oxidation of zirconium
and Zr1%Nb alloy at temperatures above 500 °С results
in the formation of the oxide films on surface. Process
of growth thickness of the oxide film on zirconium
samples depends on the holding time and oxidation
temperature.
Regimes of air-thermal oxidation of zirconium and
its alloy for the production of protective oxide films
have been determined. It has been established that at
temperature of 500…600 ºС the films characterized by
high strength and density are formed. Raising the oxida-
tion temperature leads to the formation and growth of
cracks and micropores in the structure of the oxide films
on the zirconium materials and consequently to reduce
their protective properties.
REFERENCES
1. B. Cox. Some thoughts on the mechanisms of in-
reactor corrosion of zirconium alloys // J. Nucl. Mater.
2005, v. 336, №2-3, p. 331-368.
2. A.K. Shikov, A.D. Nikulin, A.V. Nikulina, et аl.
The current state and development prospects of zirco-
nium and its alloys and products thereof // Physics and
chemistry of materials processing. 2001, № 6, p. 5-14.
3. D. Douglas. Physical metallurgy of zirconium.
М.: “Atomizdat”, 1975, 360 p.
4. A.S. Zaymovsky, A.V. Nikulina, N.G. Reshet-
nikov. Zirconium alloys in nuclear technology. M.:
“Energoatomizdat”, 1994, 453 p.
5. A. Yilmazbayhan, A. Motta, R. Comstock, et al.
Structure of zirconium alloy oxides formed in pure wa-
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croscopy: relation to corrosion rate // J. Nucl. Mater.
2004, v. 324, №1, p. 6-22.
6. B. Cox, V. Kritsky, C. Lemaignan, et al. Water-
Side Corrosion of Zirconium Alloys in Nuclear Power
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7. B.G. Parfenov, V.V. Gerasimov, G.I. Venedik-
tova. Corrosion of Zirconium and its Alloys. М.:
“Atomizdat”, 1967, 260 p.
8. M.M. Pylypenko, R.V. Azhazha, I.G. Tantsyura,
D.V. Kovteba, Yu.S. Stadnik. Effect of temperature on
the formation process of an oxide film on the surface of
Zr1%Nb alloy // Proceedings of the International Con-
ference on the Physics of Radiation Phenomena and
Radiation Material. Alushta, 2012, p. 241.
9. M.M. Pylypenko. Effect of fluoride on suscepti-
bility of the Zr-Nb alloys to high temperature oxidation
// PAST. Series “Vacuum, pure metals, superconduc-
tors”. 2011, №6(76), p. 18-23.
Статья поступила в редакцию 12.02.2014 г.
ВОЗДУШНО-ТЕРМИЧЕСКОЕ ОКИСЛЕНИЕ ЦИРКОНИЕВЫХ МАТЕРИАЛОВ
Н.Н. Пилипенко, А.А. Дробышевская, Ю.С. Стадник, И.Г. Танцюра
Приведены результаты исследований влияния температуры на процесс образования оксидных пленок на
поверхности циркониевых материалов. Проанализированы изменения морфологии, структуры и свойств
оксидных пленок на цирконии и сплаве Zr1%Nb в результате воздействия термической обработки в воздуш-
ной среде при 500…800 ºС в течение 10 ч.
ПОВІТРЯНО-ТЕРМІЧНЕ ОКИСЛЕННЯ ЦИРКОНІЄВИХ МАТЕРІАЛІВ
М.М. Пилипенко, А.О. Дробишевська, Ю.С. Стаднік, І.Г. Танцюра
Приведено результати досліджень впливу температури на процес утворення оксидних плівок на поверхні
цирконієвих матеріалів. Проаналізовано зміни морфології, структури і властивостей оксидних плівок на ци-
рконії та сплаві Zr1%Nb в результаті впливу термічної обробки в повітряному середовищі при 500…800 ºС
протягом 10 год.
|