U.S. patent application number 14/695792 was filed with the patent office on 2016-04-21 for chromium-aluminum binary alloy having excellent corrosion resistance and method of manufacturing thereof.
This patent application is currently assigned to Korea Atomic Energy Research Institute. The applicant listed for this patent is Korea Atomic Energy Research Institute. Invention is credited to Yang-Il JUNG, Hyun Gil KIM, Il Hyun KIM, Yang-Hyun KOO, Dong Jun PARK, Jeong-Yong PARK, Jung Hwan PARK.
Application Number | 20160108507 14/695792 |
Document ID | / |
Family ID | 55642152 |
Filed Date | 2016-04-21 |
United States Patent
Application |
20160108507 |
Kind Code |
A1 |
KIM; Hyun Gil ; et
al. |
April 21, 2016 |
Chromium-Aluminum Binary Alloy Having Excellent Corrosion
Resistance and Method of Manufacturing Thereof
Abstract
The present disclosure relates to a chromium-aluminum binary
alloy with excellent corrosion resistance and a method of producing
the same, and more particularly to a chromium-aluminum binary alloy
with excellent corrosion resistance, including: 1 to 40% by weight
of aluminum (Al), the balance of chromium (Cr), and other
unavoidable impurities with respect to a total weight of the alloy,
and a method of producing a chromium-aluminum binary alloy with
excellent corrosion resistance, the method including: (Step 1)
mixing and melting a raw material comprising: 1 to 40% by weight of
aluminum (Al), the balance of chromium (Cr), and other unavoidable
impurities with respect to a total weight of the alloy; and (Step
2) solution treating the alloy melted in Step 1. The
chromium-aluminum binary alloy may be easily produced and has
ductility, thus being highly applicable as a coating material for a
material requiring high-temperature corrosion resistance and wear
resistance.
Inventors: |
KIM; Hyun Gil; (Daejeon,
KR) ; KIM; Il Hyun; (Daejeon, KR) ; JUNG;
Yang-Il; (Daejeon, KR) ; PARK; Dong Jun;
(Daejeon, KR) ; PARK; Jung Hwan; (Daejeon, KR)
; PARK; Jeong-Yong; (Daejeon, KR) ; KOO;
Yang-Hyun; (Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Korea Atomic Energy Research Institute |
Daejeon |
|
KR |
|
|
Assignee: |
Korea Atomic Energy Research
Institute
Daejeon
KR
|
Family ID: |
55642152 |
Appl. No.: |
14/695792 |
Filed: |
April 24, 2015 |
Current U.S.
Class: |
148/538 ;
148/423 |
Current CPC
Class: |
C22C 1/02 20130101; C22C
16/00 20130101; C23C 4/08 20130101; C22C 27/06 20130101; C22C 19/03
20130101; C22F 1/11 20130101 |
International
Class: |
C22F 1/11 20060101
C22F001/11; C22C 1/02 20060101 C22C001/02; C22C 27/06 20060101
C22C027/06 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2014 |
KR |
10-2014-0141522 |
Claims
1. A chromium-aluminum binary alloy with excellent corrosion
resistance, comprising: 1 to 40% by weight of aluminum (Al), the
balance of chromium (Cr), and other unavoidable impurities with
respect to a total weight of the alloy.
2. The chromium-aluminum binary alloy of claim 1, wherein the
aluminum is contained in an amount of 1 to 18% by weight or 22 to
40% by weight with respect to the total weight of the alloy.
3. A method of producing a chromium-aluminum binary alloy with
excellent corrosion resistance, the method comprising: (Step 1)
mixing and melting a raw material comprising: 1 to 40% by weight of
aluminum (Al), the balance of chromium (Cr), and other unavoidable
impurities with respect to a total weight of the alloy; and (Step
2) solution treating the alloy melted in Step 1.
4. The method of claim 3, wherein the aluminum is contained in an
amount of 1 to 18% by weight or 22 to 40% by weight with respect to
the total weight of the alloy.
5. The method of claim 3, wherein the melting of Step 1 is
performed at a temperature of 1400.degree. C. to 1800.degree.
C.
6. The method of claim 3, wherein the solution treating of Step 2
is performed at a temperature of 950.degree. C. to 1200.degree.
C.
7. A chromium-aluminum binary alloy with excellent corrosion
resistance, produced according to the method of claim 3, the
chromium-aluminum binary alloy having a hardness of 250-450 Hv, and
high-temperature oxidation resistance 100 to 200 times higher than
that of a zircaloy-4 alloy, 5 to 10 times higher than that of pure
chromium, and 2 to 10 times higher than that of an FeCrAl
alloy.
8. A high-temperature environment structural material comprising
the chromium-aluminum binary alloy with excellent corrosion
resistance of claim 7.
9. A surface coating material for a metal material, comprising the
chromium-aluminum binary alloy with excellent corrosion resistance
of claim 7.
10. The surface coating material of claim 9, wherein the metal
material is stainless steel or inconel.
Description
CROSS-REFERENCES TO RELATED APPLICATION
[0001] This patent application claims the benefit of priority from
Korean Patent Application No. 10-2014-0141522, filed on Oct. 20,
2014, the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present disclosure relates to a chromium-aluminum binary
alloy with excellent corrosion resistance and a method of producing
the same, and more particularly, to a chromium-aluminum binary
alloy including 1 to 40% by weight of aluminum and to a method of
producing the same.
[0004] 2. Description of the Related Art
[0005] A zirconium alloy material used as a core component of a
fuel assembly in Japan's Fukushima accident generated a large
amount of hydrogen by a very high corrosion reaction rate to act as
the cause of a hydrogen explosion in a high-temperature oxidizing
atmosphere in which coolant was lost and a temperature of a nuclear
fuel was increased.
[0006] From this fact, it was confirmed that when the current
zirconium alloy material was used as a core material of a nuclear
power plant, there was no big problem in a steady-state, but safety
was not guaranteed in an accident-state.
[0007] One of ways to overcome the limitation of the zirconium
alloy at a high-temperature accident-state and to greatly enhance
safety of the fuel assembly is to replace the zirconium alloy with
a material having an excellent oxidation resistance or to coat a
zirconium alloy surface with an oxidation-resistant material to
increase oxidation resistance.
[0008] That is, when a material in which oxidation is hardly
generated is applied to the zirconium alloy or an
oxidation-resistant coating material stable at a high-temperature
environment of an accident-state is present on a zirconium alloy
surface, an oxidation reaction is significantly suppressed to
reduce hydrogen generation by the oxidation reaction, so that a
risk of hydrogen explosion may be blocked.
[0009] To solve this problem, in laboratories and academia
worldwide, research for developing a SiC/SiC.sub.f material, a
FeCrAl alloy, a Zr--Mo-coated cladding tube, a Zr-coated cladding
tube or the like with a new material has been in progress to
improve safety of a nuclear power plant in an environment such as
the Fukushima accident.
[0010] However, these material technologies are favorable in a
normal-state but unfavorable in an accident-state, and vise versa.
For example, a SiC/SiC.sub.f material is being evaluated to have
excellent high-temperature strength and superior oxidation
resistance, but to have drawbacks in that the material dissolution
very quickly in a steady-state ambient and the production cost is
very high.
[0011] The FeCrAl alloy has excellent corrosion resistance under
steady and accident-states, but, due to a material characteristic,
has a large neutron absorption cross-sectional area and a low
tritium collection property, thus having a disadvantage in that the
FeCrAl alloy is economically infeasible when being used in a steady
operation.
[0012] The Zr--Mo-coated cladding tube is excellent in high
temperature strength, but greatly increases a cost for producing
the cladding as a trilayer and still has a lot of problems to be
technically solved.
[0013] The Zr-coated cladding tube has an advantage of accelerating
a development cycle with a relatively low cost compared to other
technologies, but has a problem of a low coating effect due to a
peeling problem of a coating layer and a reaction of a coating
material with a Zr-base material at a high temperature.
[0014] That is, when the FeCrAl alloy with excellent corrosion
resistance is applied to the Zr-coated cladding tube, there are
problems in which a composition of the coating material is changed
by interdiffusion of Zr and Fe at a temperature of 950.degree. C.
or higher and a base material of the Zr cladding tube form a
Zr--Fe-based intermetallic compound to be weakened.
[0015] When a pure Cr layer is applied to the base material of the
Zr cladding layer, interdiffusion between Cr and Zr may take place
at 1400.degree. C. or higher to reduce a problem due to a
microstructure change. However, the Zr-coated cladding tube is weak
to an impact due to low ductility of the Cr layer and has a
relatively low high-temperature oxidation resistance compared to
the FeCrAl alloy.
[0016] Meanwhile, as a related art regarding high a corrosion
resistance alloy, Korea Patent Registration No. 10-0584113
discloses an FeCrAl material and a method of producing the same.
Specifically, as a method of producing an FeCrAl material by gas
atomization, the related art provides a method of producing an
FeCrAl material, the method being characterized in that the FeCrAl
material contains: iron (Fe), chromium (Cr), and aluminum (Al) and
further includes at least one of molybdenum (Mo), hafnium (Hf),
zirconium (Zr), yttrium (Y), nitrogen (N), carbon (C), and oxygen
(O); a smelt to be sprayed contains 0.05% to 0.50% by weight of
tantalum (Ta) and titanium (Ti)less than 0.10% by weight; and a
composition of the smelt is determined such that a composition of a
powder obtained after the spraying becomes Fe: balance, Cr: 15-25,
Al: 3-7, Mo: <5, Y: 0.05-0.60, Zr: 0.01-0.30, Hf: 0.05-0.50, Ta:
0.05-0.50, Ti: <0.10, C: 0.01-0.05, N: 0.01-0.06, O: 0.02-0.10,
Si: 0.10-0.70, Mn: 0.05-0.50, P: <0.8, S: <0.005 [unit of %
by weight].
[0017] However, since the FeCrAl material, due to a material
characteristic thereof, has a large neutron absorption
cross-sectional area and a low collection property of tritium
generated in a nuclear fuel, the FeCrAl material is economically
infeasible used in a steady operation, and has a problem in which a
base material of the Zr cladding tube forms a Zr--Fe-based
intermetallic compound to be weakened when the FeCrAl material is
applied to the Zr cladding tube.
[0018] Thus, it is difficult to realize both safety and economic
feasibility with a combination of materials and coating
technologies reported so far, under a steady-state or an
accident-state of nuclear power.
[0019] Therefore, while carrying out a research about a material
having high corrosion resistance, the material being able to
realize both safety and economic feasibility under a steady-state
or an accident-state of nuclear power, the present inventors
confirmed that a chromium-aluminum binary alloy including 1 to 40%
by weigh of aluminum has high hardness and good oxidation
resistance, and completed the present invention.
SUMMARY OF THE INVENTION
[0020] One object of the present invention is to provide a
chromium-aluminum binary alloy with excellent corrosion
resistance.
[0021] Another object of the present invention is to provide a
method of producing a chromium-aluminum binary alloy with excellent
corrosion resistance.
[0022] Still another object of the present invention is to provide
a high-temperature environment structural material including a
chromium-aluminum binary alloy with excellent corrosion
resistance.
[0023] Even another object of the present invention is to provide a
surface coating material of a metal material, the surface coating
material including a chromium-aluminum binary alloy with excellent
corrosion resistance.
[0024] In order to achieve the objects, the present invention
provides a chromium-aluminum binary alloy with excellent corrosion
resistance, the chromium-aluminum binary alloy including 1 to 40%
by weight of aluminum, the balance of chromium (Cr), and other
unavoidable impurities with respect to a total weight of the
alloy.
[0025] The present invention also provides a producing method of a
chromium-aluminum binary alloy with excellent corrosion resistance,
the producing method including: mixing and melting a raw material
including 1 to 40% by weight of aluminum (Al), the balance of
chromium (Cr), and other unavoidable impurities with respect to a
total weight of the alloy (Step 1); and solution treating the alloy
melted during Step 1 (Step 2).
[0026] Furthermore, the present invention provides a
chromium-aluminum binary alloy with excellent corrosion resistance,
which is produced according to the method and has hardness of 250
to 450 Hv, and high-temperature oxidation resistance is 100 to 200
times higher than that of a zircaloy-4 alloy, 5 to 10 times higher
than that of pure chromium, and 2 to 10 times higher than that of
an FeCrAl alloy.
[0027] Furthermore, the present invention provides a
high-temperature environment structural material including the
chromium-aluminum binary alloy with excellent corrosion
resistance.
[0028] Furthermore, the present invention provides a surface
coating material of a metal material, the surface coating material
including the chromium-aluminum binary alloy with excellent
corrosion resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0030] FIG. 1 is a graph showing hardness of a chromium-aluminum
binary alloy produced in Examples 1 to 5 and a metal material of
Comparative Examples 1 to 3 measured by a micro Vickers hardness
tester;
[0031] FIG. 2 shows a photograph of a high-temperature oxidation
experiment apparatus and a schematic diagram of an experimental
condition;
[0032] FIG. 3 is a graph showing an increase in weight as a
function of time of chromium-aluminum binary alloys produced in
Examples 1 to 5 and metal materials of Comparative Examples 1 to 3
due to a high-temperature oxidation experiment;
[0033] FIG. 4 is a graph showing an increase in weight of
chromium-aluminum binary alloys produced in Examples 1 to 5 and
metal materials of Comparative Examples 1 to 3 after a
high-temperature oxidation experiment for 7200 seconds;
[0034] FIG. 5 is a semi-log graph converted from the graph of FIG.
4; and
[0035] FIG. 6 shows photographs of cross-sections of
chromium-aluminum binary alloys produced in Examples 1 to 5 and
metal materials of Comparative Examples 1 to 3 as observed by a
scanning electron microscope after a high-temperature oxidation
experiment.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The present invention provides a chromium-aluminum binary
alloy with excellent corrosion resistance, the chromium-aluminum
binary alloy including 1 to 40% by weight of aluminum, the balance
of chromium, and other unavoidable impurities with respect to a
total weight of the alloy.
[0037] Hereinafter, the chromium-aluminum binary alloy with
excellent corrosion resistance according to the present invention
will be described in more detail.
[0038] Conventionally, in order to improve safety of a nuclear
power plant, a SiC/SiC.sub.f material, a FeCrAl alloy, a
Zr--Mo-coated cladding tube, a Zr-coated cladding tube and the like
have been developed as advanced materials, but have drawbacks as
described above.
[0039] Accordingly, combinations of materials and coating
technologies reported so far have a difficulty in realizing both
safety and economic feasibility in a steady-state and an
accident-state of nuclear power.
[0040] However, the present invention provides a chromium-aluminum
binary alloy in which a content of aluminum is 1 to 40% by weight
with respect to a total weight of the alloy.
[0041] Cr forms a stable oxide of Cr.sub.2O.sub.3 by an oxidation
reaction and Al forms a stable oxide Al.sub.2O.sub.3 by an
oxidation reaction, thus increasing corrosion resistance of the
Cr--Al binary alloy. When applied to nuclear power, the
chromium-aluminum binary alloy has excellent corrosion resistance
in an accident-state as well as a steady-state operation, thus
providing effects of being able to significantly increase economic
feasibility and accident safety of nuclear power.
[0042] When a binary alloy includes less than 1% by weight of
aluminum, there is a problem in that improvement in corrosion
resistance due to aluminum is slight, and when a binary alloy
includes more than 40% by weight of aluminum, the binary alloy has
low corrosion resistance due to generation of an Al.sub.8Cr.sub.5
intermetallic compound, is lack of processability because the
intermetallic compound has very high brittleness on characteristic,
and has a difficulty in controlling the composition thereof. In
addition, since a melting point decreases as an added amount of
aluminum increases, there is a problem in that it becomes
impossible to use the binary alloy at high temperatures, such as a
nuclear power plant accident environment.
[0043] The aluminum is preferable included in an amount of 1% to
18% by weight or 22% to 40% by weight.
[0044] When 1% to 18% by weight of aluminum is included, the
aluminum is present as a solute in the Al--Cr solid solution, and
when 22% to 40% by weight of aluminum is included, an aluminum-rich
phase and a chromium-rich phase are present in a separate state in
the alloy.
[0045] When more than 18% and less than 22% by weight of aluminum
is included, an AlCr.sub.2 intermetallic compound may be generated
to rather reduce corrosion resistance.
[0046] The present invention provides a method of producing a
chromium-aluminum binary alloy with excellent corrosion resistance,
the method including: mixing and melting raw materials including 1
to 40% by weight of aluminum (Al), the balance of chromium (Cr),
and other unavoidable impurities with respect to a total weight of
the alloy (Step 1); and solution treating the alloy melted during
Step 1 (Step 2).
[0047] Hereinafter, a method of producing a chromium-aluminum
binary alloy with excellent corrosion resistance according to the
present invention will be described for each step in more
detail.
[0048] In the method of producing a chromium-aluminum binary alloy
with excellent corrosion resistance according to the present
invention, Step 1 is a step of mixing and melting raw materials
including 1 to 40% by weight of aluminum (Al), the balance of
chromium (Cr), and other unavoidable impurities with respect to a
total weight of the alloy.
[0049] In Step 1, the raw materials are mixed and melted in a
molten metal bath to produce an alloy in which the raw materials
are homogeneously mixed.
[0050] Conventionally, in order to improve safety of a nuclear
power plant, a SiC/SiC.sub.f material, a FeCrAl alloy, a
Zr--Mo-coated cladding tube, a Zr-coated cladding tube and the like
have been developed as advanced materials, but have drawbacks as
described above. Accordingly, combinations of materials and coating
technologies reported so far have a difficulty in realizing both
safety and economic feasibility in a steady-state and an
accident-state of nuclear power.
[0051] However, the present invention provides a chromium-aluminum
binary alloy in which an amount of aluminum is 1% to 40% by
weight.
[0052] Compared to oxide-based (SiO.sub.2, Cr.sub.2O.sub.3,
Al.sub.2O.sub.3, ZrO.sub.2), carbide-based (Cr.sub.3C.sub.2, SiC,
ZrC), nitride-based (ZrN) intermetallic compounds, and a MAX phase
(C or N-added compound), the chromium-aluminum binary alloy is easy
to produce. Also, the ductility of the chromium-aluminum binary
alloy not only makes it easy to produce a product but also improves
applicability as a coating material. In addition, the
chromium-aluminum binary alloy has excellent corrosion resistance
to significantly reduce a hydrogen explosion phenomenon caused by
an excessive oxidation reaction when used as a component and a
coating material of a nuclear power plant.
[0053] The aluminum is preferably included in an amount of 1% to
18% by weight or 22% to 40% by weight. When 1% to 18% by weight of
aluminum is included, the aluminum is present as a solute in the
Al--Cr solid solution, and when 22% to 40% by weight of aluminum is
included, an aluminum-rich phase and a chromium-rich phase are
present in a separate state in the alloy. When more than 18% and
less than 22% by weight of aluminum is included, an AlCr.sub.2
intermetallic compound may be generated to rather reduce corrosion
resistance.
[0054] Meanwhile, the melting in Step 1 may be performed at a
temperature of 1400.degree. C. to 1800.degree. C. When the melting
of Step 1 is performed less than 1400.degree. C., there may be a
problem in which a liquid molten state is not maintained and thus
an alloy is not properly formed, and when the melting of Step 1 is
performed more than 1800.degree. C., there may be caused problems
in which reactivity of molten metal is increased to include a large
amount of impurities, and Al having a low melting point is
evaporated to have a difficulty in controlling the composition, and
costs increase.
[0055] In the method of producing a chromium-aluminum binary alloy
with excellent corrosion resistance according to the present
invention, Step 2 is a step of solution treating the alloy melted
during Step 1.
[0056] In Step 2, the alloy melted in Step 1 is heated up to a
range in which the melted alloy becomes a solid solution, and is
quenched to maintain the solid solution state, and through this
step, the alloy elements may readily form the solid solution.
[0057] The solution treating of Step 2 may be performed at a
temperature of 950.degree. C. to 1200.degree. C. When the
temperature is lower than 950.degree. C. in the solution treating
of Step 2, there is a problem in which the precipitate AlCr.sub.2
is not completely melted and thus a desired property is not
obtained, and when the temperature is higher than 1200.degree. C.,
a production cost is increased so that the solution treating of
Step 2 is economically infeasible.
[0058] The present invention provides a chromium-aluminum binary
alloy with excellent corrosion resistance, the chromium-aluminum
binary alloy which is produced according to the above-described
method, and has hardness of 250 to 450 Hv, and high-temperature
oxidation resistance 100 to 200 times higher than that of a
zircaloy-4 alloy, 5 to 10 times higher than that of pure chromium,
and 2 to 10 times higher than that of an FeCrAl alloy.
[0059] The present invention relates to a chromium-aluminum binary
alloy including 1 to 40% by weight of aluminum, the binary alloy
being able to have excellent mechanical property and corrosion
resistance at room temperature as well as at high temperatures. In
particular, the chromium-aluminum binary alloy may have hardness of
250 to 450 Hv, and high-temperature oxidation resistance 100 to 200
times higher than that of a zircaloy-4 alloy, 5 to 10 times higher
than that of pure chromium, and 2 to 10 times higher than that of a
FeCrAl alloy.
[0060] The present invention provides a high-temperature
environment structural material including the chromium-aluminum
binary alloy with excellent corrosion resistance.
[0061] Since the chromium-aluminum binary alloy according to the
present invention has excellent corrosion resistance even at high
temperature as well as at room temperatures, the chromium-aluminum
binary alloy may be not only used as a material for components of a
nuclear power plant but also be applied to a structural material
used in a high temperature environment, such as thermal power
generation and an aircraft engine, and a gas turbine.
[0062] The present invention provides a surface coating material
including the chromium-aluminum binary alloy with excellent
corrosion resistance.
[0063] According to the present invention, since the
chromium-aluminum binary alloy has superior corrosion resistance,
is easy to produce, and has ductility, the chromium-aluminum binary
alloy may be applied as a coating material.
[0064] The chromium-aluminum binary alloy may be utilized as a
zirconium coating material used in a nuclear power plant, and as a
coating material of a metal structural material used at a high
temperature in addition to the nuclear power plant.
[0065] In the case, the metal material may be stainless steel or
inconel and has advantages of reducing a cost and a term for
technology development compared to an advanced anti-oxidation
material, by coating the alloy of the present invention on such a
metal material.
[0066] Hereinafter, the present invention will be described below
in detail with reference to the following examples. However, the
following examples are provided for illustrative purposes only, and
the scope of the present invention should not be limited thereto in
any manner.
EXAMPLE 1
Production of a Cr-2Al Alloy
[0067] Step 1: a melting temperature was set to 1600.degree. C.,
and through a vacuum arc melting, an alloy having a composition
including 2% by weight of aluminum, the balance of chromium and
other unavoidable impurities was produced.
[0068] Step 2: the alloy undergone Step 1 was solution treated at
1100.degree. C. for 20 minutes to produce a chromium-aluminum
binary alloy.
EXAMPLE 2
Production of a Cr-4Al Alloy
[0069] In step 1 of Example 1, except that the amount of aluminum
was changed to 4% by weight, a chromium-aluminum binary alloy was
produced by performing the same procedure as Example 1.
EXAMPLE 3
Production of a Cr-6Al Alloy
[0070] In step 1 of Example 1, except that the amount of aluminum
was changed to 6% by weight, a chromium-aluminum binary alloy was
produced by performing the same procedure as Example 1.
EXAMPLE 4
Production of a Cr-15Al Alloy
[0071] In step 1 of Example 1, except that the amount of aluminum
was changed to 15% by weight, a chromium-aluminum binary alloy was
produced by performing the same procedure as Example 1.
EXAMPLE 5
Production of a Cr-30Al Alloy
[0072] In step 1 of Example 1, except that the amount of aluminum
was changed to 30% by weight, a chromium-aluminum binary alloy was
produced by performing the same procedure as Example 1.
COMPARATIVE EXAMPLE 1
Pure Chromium
[0073] A commercial high purity chromium for a coating raw material
(purity of 99.9% or more) was prepared as Comparative Example
1.
COMPARATIVE EXAMPLE 2
FeCrAl
[0074] A commercial FeCrAl alloy (product name: Kantal APMT) was
prepared as Comparative Example 2.
COMPARATIVE EXAMPLE 3
Zircaloy-4
[0075] A commercial zircaloy-4 (product name: zircaloy-4) was
prepared as Comparative Example 3.
EXPERIMENTAL EXAMPLE 1
Hardness Measurement
[0076] To investigate a mechanical property of the
chromium-aluminum alloys produced in Examples 1 to 5 and metal
materials of Comparative Examples 1 to 3, hardness was measured in
a condition of maintaining a load of 98 mN for 10 seconds at room
temperature by a micro Vickers hardness tester and the result is
shown in FIG. 1. At this time, the hardness value was measured 10
times for each sample and an average was taken.
[0077] As shown in FIG. 1, it can be seen that Examples 1 to 5 have
a high hardness of about 260 to 410 Hv. On the other hand, the pure
chromium in Comparative Example 1 had hardness of about 290 Hv, and
the FeCrAl-alloy in Comparative Example 2 had hardness of about 260
Hv, and the zircaloy-4 in Comparative Example 3 had hardness of
about 240 Hv, but it can be seen that hardness of these Comparative
Examples does not exceed about 300 Hv.
[0078] As a result of observing indentation after the hardness
measurement, since a hardness value was high, but a crack around
the indentation was not observed in the alloys of Examples of the
present invention, it was confirmed that there is no brittleness
appearing in an oxide material and an intermetallic compound.
[0079] From these results, it can be seen that the hardness of the
chromium-aluminum binary alloys according to the present invention
is excellent compared to that of the metal materials of Comparative
Examples. In addition, since the alloys of Examples of the present
invention have higher hardness than zircaloy-4, the alloys of
Examples of the present invention will have high wear resistance
compared to zircaloy-4 when applied to a cladding tube.
EXPERIMENTAL EXAMPLE 2
High-Temperature Oxidation Resistance Measurement
[0080] To investigate high-temperature oxidation resistance of the
chromium-aluminum alloys produced in Examples 1 to 5 and metal
materials of Comparative Examples 1 to 3, a temperature was raised
to 1200.degree. C. at a heating rate of 50.degree. C./min and was
maintained for 7200 seconds, and air-cooled to perform an
experiment on high temperature steam oxidation with a
thermogravimetric analyzer (TGA-51-SHIMADZU) shown in FIG. 2, and
the result is shown in FIGS. 3 to 5. In addition, after the
experiment on the high temperature steam oxidation, cross-sections
of Example 3 to 5 were observed by a scanning electron microscope
and the results are shown in FIG. 6.
[0081] As shown in FIGS. 3 to 5, it can be seen that an oxidation
amount of Examples 1 to 5 is at least about 20 times less than, at
most about 200 times less than that of the zirconium alloy of
Comparative Example 3. In particular, in the case of Example 1 to 3
and 5, it can be seen that an oxidation amount of Examples 1 to 5
is at least about 10 times less than pure chromium of Comparative
Example 1 and a FeCrAl alloy of Comparative Example 2.
[0082] As shown in FIG. 6, in the case of Examples 1 to 3 and 5 in
which high temperature oxidation resistance characteristics are
most excellent, it can be seen that a dense oxide film without a
crack was formed on a surface of each of the alloys.
[0083] From these results, it can be seen that high-temperature
oxidation resistance of the chromium-aluminum binary alloy
including 1 to 40% by weight of aluminum is excellent compared to
zirconium, pure chromium, an FeCrAl Alloy, and in particular, in
the cases of including 1 to 12% or 20 to 40% by weight of aluminum,
a more excellent oxidation resistance property is exhibited.
[0084] According to the present invention, a chromium-aluminum
binary alloy is easy to produce and has ductility, thus being
highly applicable to a material requiring high-temperature
corrosion resistance and wear resistance, as a coating material. In
addition, the chromium-aluminum binary alloy has excellent
corrosion resistance in an accident-state of nuclear power as well
as a steady-state operation, thus providing effects capable of
significantly increasing economic feasibility and accident safety
of nuclear power.
[0085] Although the preferred embodiments of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
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