U.S. patent application number 13/880177 was filed with the patent office on 2013-08-08 for ni-based superalloy component having heat-resistant bond coat layer formed therein.
The applicant listed for this patent is Hiroshi Harada, Kyoko Kawagishi, Kazuhide Matsumoto. Invention is credited to Hiroshi Harada, Kyoko Kawagishi, Kazuhide Matsumoto.
Application Number | 20130202913 13/880177 |
Document ID | / |
Family ID | 45975228 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130202913 |
Kind Code |
A1 |
Kawagishi; Kyoko ; et
al. |
August 8, 2013 |
Ni-BASED SUPERALLOY COMPONENT HAVING HEAT-RESISTANT BOND COAT LAYER
FORMED THEREIN
Abstract
Provided is an Ni-based superalloy component having a
three-layer configuration of an Ni-based superalloy substrate, a
bond coat layer and a top coat layer, wherein the alloy material of
the bond coat layer has a composition including Co of at most 15.0%
by mass, Cr of from 0.1% by mass to 7.5% by mass, Mo of at most
3.0% by mass, W of from 4.1% by mass to 10.0% by mass, Al of from
6.0% by mass to 10.0% by mass, Ti of at most 2.0% by mass, Ta of
from 5.0% by mass to 15.0% by mass, Hf of at most 1.5% by mass, Y
of at most 1.0% by mass, Nb of at most 2.0% by mass and Si of at
most 2.0% by mass with a balance of Ni and inevitable impurities,
and the Ni-based superalloy substrate has a composition including
Al of from 1.0% by mass to 10.0% by mass, Ta of from 0% by mass to
14.0% by mass, Mo of from 0% by mass to 10.0% by mass, W of from 0%
by mass to 15.0% by mass, Re of from 0% by mass to 10.0% by mass,
Hf of from 0% by mass to 3.0% by mass, Cr of from 0% by mass to
20.0% by mass, Co of from 0% by mass to 20% by mass, Ru of from 0%
by mass to 14.0% by mass, Nb of from 0% by mass to 4.0% by mass, Ti
of from 0% by mass to 4.0% by mass and Si of from 0% by mass to
2.0% by mass with a balance of Ni and inevitable impurities. The
Ni-based superalloy component has the heat-resistant bond coat
layer formed therein and is extremely excellent in environmental
characteristics such as oxidation resistance and high-temperature
corrosion resistance, especially having a long heat cycle life, and
is favorable for turbine blades and vanes.
Inventors: |
Kawagishi; Kyoko; (Ibaraki,
JP) ; Matsumoto; Kazuhide; (Ibaraki, JP) ;
Harada; Hiroshi; (Ibaraki, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kawagishi; Kyoko
Matsumoto; Kazuhide
Harada; Hiroshi |
Ibaraki
Ibaraki
Ibaraki |
|
JP
JP
JP |
|
|
Family ID: |
45975228 |
Appl. No.: |
13/880177 |
Filed: |
October 18, 2011 |
PCT Filed: |
October 18, 2011 |
PCT NO: |
PCT/JP2011/073949 |
371 Date: |
April 18, 2013 |
Current U.S.
Class: |
428/633 |
Current CPC
Class: |
C22C 19/05 20130101;
Y02T 50/60 20130101; C23C 28/321 20130101; C23C 4/073 20160101;
C23C 4/134 20160101; C23C 4/137 20160101; C23C 28/345 20130101;
F01D 5/288 20130101; Y02T 50/67 20130101; Y10T 428/12618 20150115;
C22C 19/00 20130101; F01D 25/005 20130101; C23C 28/30 20130101 |
Class at
Publication: |
428/633 |
International
Class: |
F01D 25/00 20060101
F01D025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2010 |
JP |
2010-234139 |
Claims
1. An Ni-based superalloy component having a three-layer
configuration of an Ni-based superalloy substrate, a bond coat
layer and a heat-resistant ceramic top coat layer having a thermal
barrier function, wherein the alloy material of the bond coat layer
has a composition including Co of at most 15.0% by mass, Cr of from
0.1% by mass to 7.5% by mass, Mo of at most 3.0% by mass, W of from
4.1% by mass to 10.0% by mass, Al of from 6.0% by mass to 10.0% by
mass, Ti of at most 2.0% by mass, Ta of from 5.0% by mass to 15.0%
by mass, Hf of at most 1.5% by mass, Y of at most 1.0% by mass, Nb
of at most 2.0% by mass and Si of at most 2.0% by mass with a
balance of Ni and inevitable impurities, and the Ni-based
superalloy substrate has a composition including Al of from 1.0% by
mass to 10.0% by mass, Ta of from 0% by mass to 14.0% by mass, Mo
of from 0% by mass to 10.0% by mass, W of from 0% by mass to 15.0%
by mass, Re of from 0% by mass to 10.0% by mass, Hf of from 0% by
mass to 3.0% by mass, Cr of from 0% by mass to 20.0% by mass, Co of
from 0% by mass to 20% by mass, Ru of from 0% by mass to 14.0% by
mass, Nb of from 0% by mass to 4.0% by mass, Ti of from 0% by mass
to 4.0% by mass and Si of from 0% by mass to 2.0% by mass with a
balance of Ni and inevitable impurities.
2. An Ni-based superalloy component having a three-layer
configuration of an Ni-based superalloy substrate, a bond coat
layer and a heat-resistant ceramic top coat layer having a thermal
barrier function, wherein the alloy material of the bond coat layer
has a composition including Co of at most 12.0% by mass, Cr of from
0.1% by mass to 6.0% by mass, Mo of at most 3.0% by mass, W of from
4.1% by mass to 9.0% by mass, Al of from 6.5% by mass to 9.5% by
mass, Ti of at most 2.0% by mass, Ta of from 5.0% by mass to 15.0%
by mass, Hf of at most 1.5% by mass, Y of from 0.01% by mass to
1.0% by mass, Nb of at most 2.0% by mass and Si of at most 2.0% by
mass with a balance of Ni and inevitable impurities, and the
Ni-based superalloy substrate has a composition including Al of
from 3.5% by mass to 7.0% by mass, Ta of 2.0% by mass to 12.0% by
mass, Mo of from 0% by mass to 4.5% by mass, W of from 0% by mass
to 10.0% by mass, Re of from 0% by mass to 10.0% by mass, Hf of
from 0% by mass to 0.50% by mass, Cr of from 1.0% by mass to 15.0%
by mass, Co of from 0% by mass to 16% by mass, Ru of from 0% by
mass to 14.0% by mass, Nb of from 0% by mass to 2.0% by mass, Ti of
from 0% by mass to 3.0% by mass and Si of from 0% by mass to 2.0%
by mass with a balance of Ni and inevitable impurities.
3. The Ni-based superalloy component according to claim 1, wherein
the bond coat layer is formed according to a low-pressure plasma
spraying method or a high-velocity oxygen fuel spraying method.
4. The Ni-based superalloy component according to claim 2, wherein
the bond coat layer is formed according to a low-pressure plasma
spraying method or a high-velocity oxygen fuel spraying method.
5. The Ni-based superalloy component according to claim 1, wherein
the top layer includes a Zr oxide or a Hf oxide to which an oxide
of a rare earth metal such as Y, La, Ga, Sm or the like or an Mg
oxide is added.
6. The Ni-based superalloy component according to claim 2, wherein
the top layer includes a Zr oxide or a Hf oxide to which an oxide
of a rare earth metal such as Y, La, Ga, Sm or the like or an Mg
oxide is added.
7. The Ni-based superalloy component according to claim 1, wherein
the pore area of the bond coat layer is at most 5 .mu.m.sup.2 per
1000 .mu.m.sup.2.
8. The Ni-based superalloy component according to claim 2, wherein
the bond coat layer is formed according to a low-pressure plasma
spraying method, and the pore area of the bond coat layer is at
most 3 .mu.m.sup.2 per 1000 .mu.m.sup.2.
9. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 1.
10. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 2.
11. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 3.
12. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 4.
13. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 5.
14. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 6.
15. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 7.
16. A heat-resistant gas turbine component that includes the
Ni-based superalloy component of claim 8.
Description
TECHNICAL FIELD
[0001] The present invention relates to an Ni-based superalloy
component having a heat-resistant bond coat layer formed therein.
Concretely, the invention provides an Ni-based superalloy component
having a heat-resistant bond coat layer formed therein, which is
for use for turbine rotor vanes or turbine stator vanes for jet
engines, industrial gas turbines and others under high-temperature
and high-stress conditions, and which improves the environmental
characteristics such as oxidation resistance, high-temperature
corrosion resistance and the like of components and dramatically
prolongs the thermal cycle life thereof, which, however, has
theretofore been especially difficult to prolong in conventional
arts.
BACKGROUND ART
[0002] Heretofore, as substrates for turbine rotor blades or
turbine stator vanes for jet engines, industrial gas turbines and
others, Ni-based superalloys have been developed, of which the
serviceable temperature has been improved. For further enhancing
the durability of those heat-resistant components such as turbine
rotor blades, turbine stator vanes and others, ceramic thermal
barrier coating has been heretofore employed widely. For enhancing
the adhesiveness of a thermal barrier coat material to Ni-based
superalloy-made jet engine parts and for prolonging the life of
those parts, various types of bond coat materials having high
oxidation resistance have been taken into consideration, which are
applied between the Ni-based superalloy substrate and the ceramic
thermal barrier coat material. As those bond coat materials, mainly
Al (aluminium)--containing alloys are used widely. For example,
there are mentioned Ni or Co aluminide, MCrAlY (M: at least one of
Ni, Co and Fe), and further platina aluminide and others (see the
following Patent References 1 to 3).
[0003] However, when these bond coat materials are applied to
Ni-based superalloy turbine vanes and when the turbine vanes are
used at a high temperature for a long period of time, then mutual
diffusion of elements may go on via the near-interface between the
Ni-based superalloy substrate and the bond coat material and/or via
the near-interface between the ceramic thermal barrier coat
material and the bond coat material, and owing to the mutual
diffusion of elements, the Ni-based superalloy material may be
deteriorated, thereby providing some problems of material
technology in point of durability reduction of turbine vanes
themselves including strength reduction as well as environment
resistance reduction of the bond coat material. In particular,
recently, the gas temperature in jet engines and gas turbines
becomes higher, and naturally the temperature of turbine blades and
vanes rises whereby the diffusion phenomenon may be much more
accelerated. High-pressure turbine blades have a hollow structure
for cooling, but their wall thickness is being reduced in the art,
and therefore, the influence of the diffusion region brings about
much more serious technical problems.
[0004] For retarding the mutual diffusion of elements through the
near-interface of Ni-based superalloy substrate/bond coat material,
a diffusion barrier coating with a special alloy layer formed
therein has been investigated; however, cases that could not always
sufficiently attain the object of diffusion barrier coating are not
negligible (see the following Patent Reference 4).
[0005] Ralph J. Hecht et al. and Edward Harvey Goldman et al.
proposed bond coat materials having alloy compositions differing
from those of Ni or Co aluminide, MCrAlY and others heretofore
widely used in the art, and asserted the improvements thereof;
however, it could not be said that their bond coat materials could
fully fulfill the severe heat-resistant serviceable conditions
required at present (see the following Patent References 5 and
6).
[0006] FIG. 1 shows a cross-sectional view of a configuration
example of a heat-resistant gas turbine component using an Ni-based
superalloy as the substrate thereof. For increasing the heat
resistance of the Ni-based superalloy substrate (1), in general,
the surface of the substrate is coated with a ceramic thermal
barrier coat layer (3), however, the long-term adhesive property of
the interface between the Ni-based superalloy substrate and the
ceramic thermal barrier coat layer is insufficient, and therefore
various coat materials are sued as the bond coat material (2). In
general, at the near-interface between the Ni-based superalloy
substrate and the bond coat layer, element diffusion occurs to form
SRZ (secondary reaction zone) under high-temperature service
conditions, and therefore at the near-interface of the bond coat
layer adjacent to the ceramic thermal barrier coat layer, the
ceramic coat layer peels owing to the formation of oxide film under
high-temperature oxidation conditions. Consequently, the current
state is that the life of Ni-based superalloy components in use at
high temperatures could not always be said to be satisfactory.
CITATION LIST
Patent References
[0007] [Patent Reference 1] Japanese Patent 4111555
[0008] [Patent Reference 2] JP-A2008-156744
[0009] [Patent Reference 3] JP-A2002-155380
[0010] [Patent Reference 4] Japanese Patent 3862774
[0011] [Patent Reference 5] JP-A62-30037
[0012] [Patent Reference 6] JP-A5-132751
SUMMARY OF THE INVENTION
[0013] Problems that the Invention is to Solve
[0014] An object of the present invention is to provide a long-life
Ni-based superalloy component by preventing the formation of SRZ
(secondary reaction zone) to occur in the near-interface between an
Ni-based superalloy substrate and a bond coat layer and by
improving the adhesiveness at the interface between a ceramic
thermal barrier coat layer and a bond coat layer.
Means for Solving the Problems
[0015] The present inventors have assiduously studied bond coat
materials that enable diffusion barrier coating for wide-range
Ni-based superalloy substrates, and have succeeded in developing a
bond coat material having an extremely excellent property as
compared with Ni or Co aluminide, MCrAlY or the like heretofore
widely used in the art, by optimizing the alloy composition of the
bond coat material, and in developing an Ni-based superalloy
component with a layer of the heat-resistant bond coat material
formed therein.
[0016] The first improvement attained by application of the bond
coat material that the present invention proposes here is that the
material has enabled retention of long-term heat-resistant
characteristics by effectively preventing the formation of SRZ in
the near-interface between an Ni-based heat-resistant alloy
substrate and a bond coat layer which has heretofore been
considered to be uncontrollable. The second improvement is that the
invention has made it possible to form a homogeneous and dense
oxide layer in the near-interface of the bond coat layer adjacent
to the ceramic thermal barrier layer to thereby significantly
enhance the stability and the adhesiveness of the oxide layer.
Accordingly, the invention has made it possible to dramatically
prolong the heat cycle life (the time to be taken before occurrence
of spallation of ceramic thermal barrier coat) as compared with
conventional coating methods. In a high-temperature oxidation
atmosphere, the bond coat material of the invention forms a
homogeneous, dense and stable oxide layer on the surface thereof,
and therefore under not so much severe temperature conditions, even
an Ni-based superalloy component not having the ceramic thermal
barrier coat layer (3 in FIG. 1) can be used as a coat material
having a relatively long life.
[0017] Specifically, as a means for solving the above-mentioned
problems, the present invention provides, as the first aspect
thereof, an Ni-based superalloy component having a three-layer
configuration of an Ni-based superalloy substrate, a bond coat
layer and a heat-resistant ceramic top coat layer having a thermal
barrier function, wherein the alloy material of the bond coat layer
has a composition including Co of at most 15.0% by mass, Cr of from
0.1% by mass to 7.5% by mass, Mo of at most 3.0% by mass, W of from
4.1% by mass to 10.0% by mass, Al of from 6.0% by mass to 10.0% by
mass, Ti of at most 2.0% by mass, Ta of from 5.0% by mass to 15.0%
by mass, Hf of at most 1.5% by mass, Y of at most 1.0% by mass, Nb
of at most 2.0% by mass and Si of at most 2.0% by mass with a
balance of Ni and inevitable impurities, and the Ni-based
superalloy substrate has a composition including Al of from 1.0% by
mass to 10.0% by mass, Ta of from 0% by mass to 14.0% by mass, Mo
of from 0% by mass to 10.0% by mass, W of from 0% by mass to 15.0%
by mass, Re of from 0% by mass to 10.0% by mass, Hf of from 0% by
mass to 3.0% by mass, Cr of from 0% by mass to 20.0% by mass, Co of
from 0% by mass to 20% by mass, Ru of from 0% by mass to 14.0% by
mass, Nb of from 0% by mass to 4.0% by mass, Ti of from 0% by mass
to 4.0% by mass and Si of from 0% by mass to 2.0% by mass with a
balance of Ni and inevitable impurities.
[0018] As the second aspect, the invention provides the
above-mentioned Ni-based superalloy component, wherein the alloy
material of the bond coat layer has a composition including Co of
at most 12.0% by mass, Cr of from 0.1% by mass to 6.0% by mass, Mo
of at most 3.0% by mass, W of from 4.1% by mass to 9.0% by mass, Al
of from 6.5% by mass to 9.5% by mass, Ti of at most 2.0% by mass,
Ta of from 5.0% by mass to 15.0% by mass, Hf of at most 1.5% by
mass, Y of from 0.01% by mass to 1.0% by mass, Nb of at most 2.0%
by mass and Si of at most 2.0% by mass with a balance of Ni and
inevitable impurities, and the Ni-based superalloy substrate has a
composition including Al of from 3.5% by mass to 7.0% by mass, Ta
of 2.0% by mass to 12.0% by mass, Mo of from 0% by mass to 4.5% by
mass, W of from 0% by mass to 10.0% by mass, Re of from 0% by mass
to 10.0% by mass, Hf of from 0% by mass to 0.50% by mass, Cr of
from 1.0% by mass to 15.0% by mass, Co of from 0% by mass to 16% by
mass, Ru of from 0% by mass to 14.0% by mass, Nb of from 0% by mass
to 2.0% by mass, Ti of from 0% by mass to 3.0% by mass and Si of
from 0% by mass to 2.0% by mass with a balance of Ni and inevitable
impurities.
[0019] As the third aspect, the invention provides the Ni-based
superalloy substrate of the above-mentioned first aspect having a
three-layer configuration of an Ni-based superalloy substrate, a
bond coat layer and a heat-resistant ceramic top coat layer having
a thermal barrier function, wherein the bond coat layer is formed
according to a low-pressure plasma spraying method or a
high-velocity oxygen fuel spraying method.
[0020] As the fourth aspect, the invention provides the Ni-based
superalloy substrate of the above-mentioned second aspect having a
three-layer configuration of an Ni-based superalloy substrate, a
bond coat layer and a heat-resistant ceramic top coat layer having
a thermal barrier function, wherein the bond coat layer is formed
according to a low-pressure plasma spraying method or a
high-velocity oxygen fuel spraying method.
[0021] As the fifth aspect, the invention provides the Ni-based
superalloy substrate of the above-mentioned first aspect having a
three-layer configuration of an Ni-based superalloy substrate, a
bond coat layer and a heat-resistant ceramic top coat layer having
a thermal barrier function, wherein the top layer includes a Zr
oxide or a Hf oxide to which an oxide of a rare earth metal such as
Y, La, Ga, Sm or the like or an Mg oxide is added.
[0022] As the sixth aspect, the invention provides the Ni-based
superalloy substrate of the above-mentioned second aspect having a
three-layer configuration of an Ni-based superalloy substrate, a
bond coat layer and a heat-resistant ceramic top coat layer having
a thermal barrier function, wherein the top layer includes a Zr
oxide or an Hf oxide to which an oxide of a rare earth metal such
as Y, La, Ga, Sm or the like or an Mg oxide is added.
[0023] As the seventh aspect, the invention provides the Ni-based
superalloy substrate of the above-mentioned first aspect having a
three-layer configuration of an Ni-based superalloy substrate, a
bond coat layer and a heat-resistant ceramic top coat layer having
a thermal barrier function, wherein the pore area of the bond coat
layer is at most 5 .mu.m.sup.2 per 1000 .mu.m.sup.2.
[0024] As the eighth aspect, the invention provides the Ni-based
superalloy substrate of the above-mentioned second aspect having a
three-layer configuration of an Ni-based superalloy substrate, a
bond coat layer and a heat-resistant ceramic top coat layer having
a thermal barrier function, wherein the bond coat layer is formed
according to a low-pressure plasma spraying method, and the pore
area of the bond coat layer is at most 3 .mu.m.sup.2 per 1000
.mu.m.sup.2.
[0025] As the ninth aspect, the invention provides a heat-resistant
gas turbine component that includes the Ni-based superalloy
substrate of the above-mentioned eighth aspect having a three-layer
configuration of an Ni-based superalloy substrate, a bond coat
layer and a heat-resistant ceramic top coat layer having a thermal
barrier function.
Advantage of the Invention
[0026] The invention has made it possible to effectively prevent
the formation of a secondary reaction layer SRZ (secondary reaction
zone) to be caused by mutual diffusion of elements to occur between
the bond coat material and the alloy substrate at the
near-interface between an Ni-based heat-resistant alloy substrate
and a bond coat layer even under a severe condition of a
temperature of 1,100.degree. C. or higher in the air, which has
heretofore been considered to be uncontrollable.
[0027] In the invention, in addition, a homogeneous and dense oxide
layer is formed at the near-interface of the bond coat layer
adjacent to the ceramic thermal barrier coat layer, and therefore
the stability and the adhesiveness of the oxide layer can be
greatly enhanced. Owing to the synergistic effect, the invention
has made is possible to dramatically prolong the heat cycle life
(the time to be taken before occurrence of spallation of ceramic
thermal barrier coat) as compared with conventional coating
methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a cross-sectional view of a configuration model of
a heat-resistant gas turbine component that uses an Ni-based
superalloy component having a three-layer configuration of an
Ni-based superalloy substrate (1), a bond coat layer (2) and a
heat-resistant ceramic top coat layer (3) having a thermal barrier
function.
[0029] FIG. 2 is a graph for comparing the cycle life before
coating film spallation of the top coat layer (3) occurs in a heat
cycle test of the above-mentioned, three-layer configuration-having
Ni-based superalloy component (test of heating the sample at
1135.degree. C. for 1 hour and then keeping it at room temperature
for 1 hour as one cycle, and the cycle is repeated). Six cases are
compared, which differ in the type of the bond coat material and in
the coating method. The fourth bar graph having a height of 1300
from the left shows that <Example 1L>, in which the "BC-1"
bond coat material in [Table 1] was formed into a bond coat layer
according to a low-pressure plasma spraying method, did not undergo
coating film spallation in the first-try experiment of up to 1300
cycles. (The results of the subsequent experiment are shown in FIG.
6.)
[0030] FIG. 3 is a micrograph of the cross section of an Ni-based
superalloy component having a three-layer configuration of an
Ni-based superalloy substrate coated with a bond coat layer and
further coated with a ceramic top coat layer. (<Example 1L>)
(The black part at the top of the photograph is the background in
taking the picture. "8YSZ" means that the ceramic top coat layer is
formed of a Zr oxide stabilized by incorporation of 8 wt. % Y oxide
thereinto.)
[0031] FIG. 4 shows micrographs of cross sections for comparing the
degree of pore distribution in the bond coat layer formed by
coating with the bond coat material of the invention according to
different coating methods: (A) a low-pressure plasma spraying
(LPPS) method or (B) a high-velocity oxygen fuel (HVOF) spraying
method.
[0032] FIG. 5 is a graph for comparing the pore area ratio of the
bond coat layer formed on an Ni-based superalloy substrate using
different bond coat materials according to different coating
methods.
[0033] FIG. 6 is a graph for comparing the cycle life before
coating film spallation of the top coat layer (3) occurs in a heat
cycle test of the three-layer configuration-having Ni-based
superalloy component shown in FIG. 1 (test of heating the sample at
1135.degree. C. for 1 hour and then keeping it at room temperature
for 1 hour as one cycle, and the cycle is repeated). This shows the
results of the subsequent experiment after the test in FIG. 2. The
fifth bar graph having a height of 2444 from the left shows that
one sample of <Example 1L>, in which the "BC-1" bond coat
material in [Table 1] was formed into a bond coat layer according
to a low-pressure plasma spraying method, underwent coating film
spallation after the life of 2444 cycles. The fourth bar graph
having a height of 2098 from the left shows that another sample of
<Example 1L>, in which the "BC-1" bond coat material in
[Table 1] was formed into a bond coat layer according to a
low-pressure plasma spraying method, underwent coating film
spallation after the life of 2098 cycles.
[0034] FIG. 7 shows enlarged SEM photographs of the region of
substrate (1)/SRZ/bond coat layer (2) of cross sections of
three-layer configuration-having Ni-based alloy component samples
after 300 cycles of the heat cycle test. <Example 1L> is
compared with Comparative Examples in point of the thickness of the
secondary reaction layer (SRZ) (layer sandwiched between two lines
at the center of each drawing) formed in the interfacial boundary
between the Ni-based superalloy substrate (1) (bottom layer in each
drawing) and the bond coat layer (2) (top layer in each
drawing).
[0035] FIG. 8 shows enlarged SEM photographs of the region of bond
coat layer (2)/TGO (thermally-grown oxide)/top coat layer (3) of
cross sections of three-layer configuration-having Ni-based alloy
component samples after 300 cycles of the heat cycle test. As
compared with <Example 1L> [Photograph 8A], Comparative
Examples [Photograph 8B] and [Photograph 8C] have a space formed
between the dark TGO (thermally-grown oxide) and the bond coat
layer (2). [Photograph 8D] is an enlarged SEM photograph of the
same region as in <Example 1L> but after 1000 cycles of the
heat cycle test. In this, it is confirmed that TGO (thermally-grown
oxide) further grew to have wedge-shaped oxides stepping in the
bond coat layer (2).
MODE FOR CARRYING OUT THE INVENTION
[0036] The bond coat material and the Ni-based superalloy component
having, as formed therein, a heat-resistant bond coat layer using
the bond coat material, which the invention proposes here,
effectively inhibit the formation of SRZ (secondary reaction zone)
at the near-interface between the Ni-based heat-resistant alloy
substrate and the bond coat layer, which has heretofore been
considered to be uncontrollable, and in addition, they form a
homogeneous and dense oxide layer (TGO, thermally-grown oxide) in
the near-interface of the bond coat layer adjacent to the ceramic
thermal barrier coat layer to thereby greatly enhance the stability
and the adhesiveness of the oxide layer, and accordingly, as
compared with conventional coating methods, the invention enables a
great improvement of the heat cycle life of the heat-resistant bond
coat layer-having, Ni-based superalloy component.
[0037] The bond coat material that the invention proposes here is
widely applicable to first to third generation Ni-based
single-crystal superalloys generally used in the art, and also to
fourth and fifth generation Ni-based single-crystal superalloys
which contain Re (rhenium) and Ru (ruthenium) and which have become
actively developed these days. Preferred Ni-based single-crystal
superalloys include, for example, alloys including Al of from 1.0%
by mass to 10.0% by mass, Ta of from 0% by mass to 14.0% by mass,
Mo of from 0% by mass to 10.0% by mass, W of from 0% by mass to
15.0% by mass, Re of from 0% by mass to 10.0% by mass, Hf of from
0% by mass to 3.0% by mass, Cr of from 0% by mass to 20.0% by mass,
Co of from 0% by mass to 20% by mass, Ru of from 0% by mass to
14.0% by mass, Nb of from 0% by mass to 4.0% by mass, Ti of from 0%
by mass to 4.0% by mass and Si of from 0% by mass to from 2.0% by
mass with a balance of Ni and inevitable impurities; and more
preferred are alloys including Al of from 3.5% by mass to 7.0% by
mass, Ta of from 2.0% by mass to 12.0% by mass, Mo of from 0% by
mass to 4.5% by mass, W of from 0% by mass to 10.0% by mass, Re of
from 0% by mass to 10.0% by mass, Hf of from 0% by mass to 0.50% by
mass, Cr of from 1.0% by mass to 15.0% by mass, Co of from 0% by
mass to 16% by mass, Ru of from 0% by mass to 14.0% by mass, Nb of
from 0% by mass to 2.0% by mass, Ti of from 0% by mass to 3.0% by
mass and Si of from 0% by mass to from 2.0% by mass with a balance
of Ni and inevitable impurities
[0038] The invention provides an Ni-based superalloy component
having a three-layer configuration of an Ni-based superalloy
substrate, a bond coat layer and a top coat layer, wherein the
alloy material of the bond coat layer has a composition including
Co of at most 15.0% by mass, Cr of from 0.1% by mass to 7.5% by
mass, Mo of at most 3.0% by mass, W of from 4.1% by mass to 10.0%
by mass, Al of from 6.0% by mass to 10.0% by mass, Ti of at most
2.0% by mass, Ta of from 5.0% by mass to 15.0% by mass, Hf of at
most 1.5% by mass, Y of at most 1.0% by mass, Nb of at most 2.0% by
mass and Si of at most 2.0% by mass with a balance of Ni and
inevitable impurities, more preferably including Co of at most
12.0% by mass, Cr of from 0.1% by mass to 6.0% by mass, Mo of at
most 3.0% by mass, W of from 4.1% by mass to 9.0% by mass, Al of
from 6.5% by mass to 9.5% by mass, Ti of at most 2.0% by mass, Ta
of from 5.0% by mass to 15.0% by mass, Hf of at most 1.5% by mass,
Y of from 0.01% by mass to 1.0% by mass, Nb of at most 2.0% by mass
and Si of at most 2.0% by mass with a balance of Ni and inevitable
impurities.
[0039] Examples of a typical alloy of MCrAIY that is a bond coat
material most popularly used at present include a composition
including, as % by mass, Co of about 21.5%, Cr of about 17%, Al of
about 12.4%, Y of about 0.7% and a balance of Ni and inevitable
impurities, and a composition including Co of about 38.5%, Cr of
about 21%, Al of about 8%, Y of about 0.5% and a balance of Ni and
inevitable impurities.
[0040] The alloy composition of the bond coat material of the
invention significantly differs from the composition of those
already-existing materials, and using the bond coat material that
has the alloy composition optimized as indicated in the invention
can attain the excellent life prolongation even under any severe
high-temperature service conditions.
[0041] The coating method with a bond coat material is not limited
to any specific technique, but any of a plasma spraying method, a
high-velocity oxygen fuel spraying method, an ion plating method,
an EB-PVD method, a CVD method and others generally used in the art
are usable here.
[0042] Above all, preferred is a coating process using a
low-pressure plasma spraying method (LPPS) or a high-velocity
oxygen fuel spraying method (HVOF).
[0043] The bond coat material of the invention can form a dense
coating layer with few pores according to any coating method
mentioned above, by optimizing the coating condition therein. In
particular, the low-pressure plasma spraying method (LPPS) is a
preferred coating method, in which the bond coat layer formed has
few pores and the degree of oxidation of the bond coat layer is
low.
[0044] The pore density of the bond coat layer is an important
parameter that influences the long-term coating film spallation
life under high-temperature conditions, and varies depending on the
bond coat material and the bond coating condition, etc. For
prolonging the coating film spallation life at high temperatures,
the pore area is preferably at most 5 .mu.m.sup.2, more preferably
at most 3 .mu.m.sup.2 per 1000 .mu.m.sup.2, as a scale of pore
density in the bond coat layer. The thickness of the bond coat
layer may be from 10 to 500 .mu.m, preferably from 20 to 400
.mu.m.
[0045] The material of the ceramic thermal barrier coat layer is
not limited to specific ceramics but any ceramic materials
recognized to have a thermal barrier effect can be used here. One
typical example is partially-stabilized zirconia (zirconium oxide),
and for preventing cracking owing to expansion/contraction through
phase transformation, at least one of a rare earth oxide such as
yttrium oxide, cerium oxide or the like, or magnesium oxide may be
added thereto for partial or complete stabilization thereof, and
the thus-stabilized one is preferred for use herein. In particular,
partially-stabilized zirconia containing from 7 to 8% by mass of
yttrium oxide is widely used as an excellent heat-resistant ceramic
material, and can be used for coating according to an EB-PVD
method, a spraying method or the like coating method.
[0046] The Ni-based superalloy substrate with a heat-resistant bond
coat layer formed thereon of the invention is described with
reference to Examples given below.
EXAMPLES
[0047] Next, the advantages of the invention are described with
reference to Examples given below.
TABLE-US-00001 TABLE 1 Alloying Element (% by mass) Bond Coat
Material Co Cr Mo W Al Ta Ti Hf Y Ni BC-1 6.1 3.7 1.0 4.8 8.1 9.2
-- 0.3 0.1 balance BC-2 4.7 1.4 0.9 7.2 7.9 9.5 0.7 0.16 0.5
balance BC-3 9.6 1.4 1.0 6.1 8.9 6.3 -- 0.1 0.1 balance BC-4 4.5
1.6 1.6 5.6 8.3 8.5 -- 0.15 0.1 balance BC-5 -- 3.6 -- 5.6 7.7 13.8
-- -- 0.2 balance BC-6 3.2 5.3 0.3 6.3 8.1 8.5 1.3 -- 0.2 balance
BC-7 7.2 2.8 0.3 5.5 7.9 9.5 1.4 0.15 0.2 balance CoNiCrAlY 38.5
21.0 -- -- 8.0 -- -- -- 0.5 balance (already-existing alloy A)
NiCoCrAlY 21.5 17.0 -- -- 12.4 -- -- -- 0.7 balance
(already-existing alloy B)
Example 1H
[0048] Using an ingot of BC-1 alloy as the bond coat material of
the invention shown in [Table 1], a metal powder for coating was
prepared, and then a bond coat layer (2) (thickness: about 150
.mu.m) was formed on the Ni-based single-crystal alloy substrate
(1). The composition of the Ni-based single-crystal alloy substrate
(1) used here includes Al of 5.9% by mass, Ta of 5.9% by mass, Mo
of 2.9% by mass, W of 5.9% by mass, Re of 5.8% by mass, Hf of 0.1%
by mass, Cr of 2.9% by mass, Co of 5.8% by mass and Ru of 3.5% by
mass with a balance of Ni and inevitable impurities.
[0049] As the method of applying the above-mentioned bond coat
material onto the Ni-based single-crystal alloy substrate (1)
having a diameter of 10 mm and a thickness of 5 mm, used was a
high-velocity oxygen fuel method (HVOF method). The spraying
conditions for the HVOF method were: substrate temperature of
130.degree. C., kerosene as fuel of 20.8 L/hr, oxygen of 898 L/min,
nitrogen as carrier gas of 2 L/min.
[0050] Before forming the thermal barrier ceramic layer (3) to be
the top coat layer, the surface of the bond coat layer (2) formed
by bond coating on the Ni-based single-crystal alloy substrate was
polished with alumina, and further pre-oxidized in an EB-PVD
apparatus. Subsequently, using yttrium oxide-partially stabilized
zirconia as the material thereof, the top coat layer was formed.
The film formation was under the control of oxygen flow rate at a
substrate temperature of 930.degree. C. and under a pressure of 0.2
Pa. The thickness of the top coat layer was about 200 .mu.m. FIG. 3
shows a microstructure photograph of the cross section of the
three-layered sample produced here, having, as formed on the
Ni-based single-crystal alloy substrate (1), the bond coat layer
(BC-1) (2) and further the top coat layer (3) thereon.
Example 1L
[0051] Using the BC-1 alloy as the bond coat material of the
invention shown in [Table 1], a bond coat layer (2) (thickness:
about 150 .mu.m) was formed on the Ni-based single-crystal alloy
substrate (1). The composition of the Ni-based single-crystal alloy
substrate (1) used, the composition of the top coat layer and the
three-layer configuration ratio were the same as in
Example 1H
[0052] As the method of applying the bond coat material onto the
Ni-based single-crystal alloy substrate (1) having a diameter of 10
mm and a thickness of 5 mm, used was a low-pressure plasma spraying
method (LPPS method). The spraying conditions for the LPPS method
were: substrate preheating temperature of 600.degree. C., argon of
45 L/min with hydrogen of 8 L/min as plasma gas, and argon of 2
L/min as carrier gas.
Comparative Example 1H
[0053] Using a bond coat material of an already-existing alloy,
CoNiCrAlY alloy as a typical case of Comparative Examples shown in
[Table 1], a bond coat layer (2) (thickness: about 150 .mu.m) was
formed on the Ni-based single-crystal alloy substrate (1). The
composition of the Ni-based single-crystal alloy substrate (1)
used, the composition of the top coat layer, the three-layer
configuration ratio, and the coating condition in the high-velocity
oxygen fuel method (HVOF method) with the bond coat material were
the same as in <Example 1H>.
Comparative Example 1L
[0054] Using a bond coat material of an already-existing alloy,
CoNiCrAlY alloy as a typical case of Comparative Examples shown in
[Table 1], a bond coat layer (2) (thickness: about 150 .mu.m) was
formed on the Ni-based single-crystal alloy substrate (1). The
composition of the Ni-based single-crystal alloy substrate (1)
used, the composition of the top coat layer, the three-layer
configuration ratio, and the coating condition in the low-pressure
plasma spraying method (LPPS method) with the bond coat material
were the same as in <Example 1L>. <Comparative Example
2H>
[0055] Using a bond coat material of an already-existing alloy,
NiCoCrAlY alloy as a typical case of Comparative Examples shown in
[Table 1], a bond coat layer (2) (thickness: about 150 .mu.m) was
formed on the Ni-based single-crystal alloy substrate (1). The
composition of the Ni-based single-crystal alloy substrate (1)
used, the composition of the top coat layer, the three-layer
configuration ratio, and the coating condition in the high-velocity
oxygen fuel method (HVOF method) with the bond coat material were
the same as in <Example 1H>.
Comparative Example 2L
[0056] Using a bond coat material of an already-existing alloy,
NiCoCrAlY alloy as a typical case of Comparative Examples shown in
[Table 1], a bond coat layer (2) (thickness: about 150 .mu.m) was
formed on the Ni-based single-crystal alloy substrate (1). The
composition of the Ni-based single-crystal alloy substrate (1)
used, the composition of the top coat layer, the three-layer
configuration ratio, and the coating condition in the low-pressure
plasma spraying method (LPPS method) with the bond coat material
were the same as in <Example 1L>.
[0057] Each of the six samples produced by the combination the
three types of bond coating materials and the two types of the bond
coating methods (each sample obtained in each of <Example 1H>
to <Comparative Example 2L>) was tested in the heat cycle
test, and the results are shown in [FIG. 2]. In the heat cycle
test, an electric furnace was used. In one cycle, the sample was
held in air at a holding temperature of 1135.degree. C. for 1 hour,
then cooled, and held at room temperature for 1 hour. The
spallation life indicates the number of cycles in which at least
50% of the top coat layer (3) exfoliated.
[0058] In any coating method, it is known that the samples having
the bond coat layer formed of the bond coat material of the
invention (BC-1) have a longer coating film spallation life than
those using already-existing alloys (CoNiCrAlY, NiCoCrAlY) (FIG.
2). The coating methods were compared. It is known that, in
general, the samples produced according to the low-pressure plasma
spraying method (LPPS method) have a longer coating film spallation
life than those produced according to the high-velocity oxygen fuel
method (HVOF method). However, the three-layered component sample
using the already-existing alloy CoNiCrAlY for the bond coat layer
produced according to the HVOF method was better (see FIG. 2, FIG.
6).
[0059] In the case where the bond coat material of the invention
was applied to the substrate according to the low-pressure plasma
spraying method (LPPS method), the coating film spallation life was
dramatically prolonged (1300 cycles or more); and as compared with
the case where already-existing alloy (CoNiCrAlY, NiCoCrAlY) was
used, the case of the invention attained at least 5 times life
prolongation.
[0060] In the graph of [FIG. 2], the fourth bar graph having a
height of 1300 from the left shows that <Example 1L>, in
which the "BC-1" bond coat material in [Table 1] was formed into
the bond coat layer according to the low-pressure plasma spraying
method, did not undergo coating film spallation in the first-try
experiment of up to 1300 cycles. (The results of the subsequent
experiment are shown in FIG. 6.)
<Examples 2 to 6
[0061] For the Ni-based single-crystal alloy substrate, prepared
was an alloy with a composition including Al of 5.7% by mass, Ti of
0.9% by mass, Ta of 6.6% by mass, Mo of 0.7% by mass, W of 5.9% by
mass, Re of 3.1% by mass, Cr of 6.4% by mass, Co of 8.9% by mass,
and a balance of Ni and inevitable impurities. A bond coat material
of any of the five types of alloys of the invention (BC-2, 3, 4, 6,
7) shown in Table 1 was applied onto the Ni-based single-crystal
alloy substrate according to a low-pressure plasma spraying method
(LPPS method) to form a bond coat layer thereon, and then a top
coat layer was formed thereon according to the same method as in
the above. These are sequentially referred to as Example 2, Example
3, Example 4, Example 5 and Example 6.
[0062] These five types of three-layered samples were evaluated for
the coating film spallation life according to the above-mentioned
method. It was known that all the samples had a stable life of 500
cycles or more.
Example 7
[0063] For the Ni-based single-crystal alloy substrate, prepared
was an alloy with a composition including Al of 5.5% by mass, Ta of
10.0% by mass, Mo of 0.1% by mass, W of 7.9% by mass, Re of 0.4% by
mass, Cr of 8.9% by mass, and a balance of Ni and inevitable
impurities. A bond coat material of the alloy BC-5 of the invention
shown in Table [1]] was applied onto the Ni-based single-crystal
alloy substrate according to a low-pressure plasma spraying method
(LPPS method) to form a bond coat layer thereon, and then a top
coat layer was formed thereon according to the same method as in
the above. The three-layered sample thus produced was evaluated for
the coating film spallation life according to the above-mentioned
method. It was known that the sample had a stable life of 500
cycles or more.
[0064] As given below, the above-mentioned Examples are enumerated
in [Table 2] and the Comparative Examples are in [Table 3].
TABLE-US-00002 TABLE 2 Example ex. 1H ex. 1L ex. 2 ex. 3 ex. 4 ex.
5 ex. 6 ex. 7 Spallation Life 350 1300- 500- 500- 500- 500- 500-
500- Top Layer YSZ YSZ YSZ YSZ YSZ YSZ YSZ YSZ Ni Bond Layer
Deposition Method HVOF LPPS LPPS LPPS LPPS LPPS LPPS LPPS Pore Area
Ratio 0.002 0.001 -- -- -- -- -- -- (BC-1) (BC-1) (BC-2) (BC-3)
(BC-4) (BC-6) (BC-7) (BC-5) Co 6.1 6.1 4.7 9.6 4.5 3.2 7.2 Cr 3.7
3.7 1.4 1.4 1.6 5.3 2.8 3.6 Mo 1.0 1.0 0.9 1.0 1.6 0.3 0.3 W 4.8
4.8 7.2 6.1 5.6 6.3 5.5 5.6 Al 8.1 8.1 7.9 8.9 8.3 8.1 7.9 7.7 Ti
0.7 1.3 1.4 Ta 9.2 9.2 9.5 6.3 8.5 8.5 9.5 13.8 Hf 0.3 0.3 0.16 0.1
0.15 0.15 Y 0.1 0.1 0.5 0.1 0.1 0.2 0.2 0.2 Nb Si Ni balance
balance balance balance balance balance balance balance Ni
Substrate Al 5.9 5.9 5.7 5.7 5.7 5.7 5.7 5.5 Ta 5.9 5.9 6.6 6.6 6.6
6.6 6.6 10 Mo 2.9 2.9 0.7 0.7 0.7 0.7 0.7 0.1 W 5.9 5.9 5.9 5.9 5.9
5.9 5.9 7.9 Re 5.8 5.8 3.1 3.1 3.1 3.1 3.1 0.4 Hf 0.1 0.1 Cr 2.9
2.9 6.4 6.4 6.4 6.4 6.4 8.9 Co 5.8 5.8 8.9 8.9 8.9 8.9 8.9 Ru 3.5
3.5 Nb Ti 0.9 0.9 0.9 0.9 0.9 Si Ni balance balance balance balance
balance balance balance balance
TABLE-US-00003 TABLE 3 Comparative Example com. 1H com. 1L com. 2H
com. 2L Spallation Life 210 100 200 210 Top Layer YSZ YSZ YSZ YSZ
Ni Bond Layer Deposition Method HVOF LPPS LPPS LPPS Pore Area Ratio
-- 0.013 0.012 0.008 Alloy B Alloy B Alloy A Alloy A Co 21.5 21.5
38.5 38.5 Cr 17 17 21 21 Mo W Al 12 12 8 8 Ti Ta Hf Y 07 0.7 0.5
0.5 Nb Si Ni balance balance balance balance Ni Substrate Al 5.9
5.9 5.9 5.9 Ta 5.9 5.9 5.9 5.9 Mo 2.9 2.9 2.9 2.9 W 5.9 5.9 5.9 5.9
Re 5.8 5.8 5.8 5.8 Hf 0.1 0.1 0.1 0.1 Cr 2.9 2.9 2.9 2.9 Co 5.8 5.8
5.8 5.8 Ru 3.5 3.5 3.5 3.5 Nb Ti Si Ni balance balance balance
balance
[0065] FIG. 4 shows micrographs of cross sections for comparing the
degree of pore distribution in the microstructure of the cross
section of the bond coat layer formed by coating with the bond coat
material (BC-1) of the invention according to different coating
methods.
[0066] The parts seen black correspond to the pores existing inside
the bond coat layer. It is seen that the pores are small in the
case of the low-pressure plasma spraying method (LPPS method)
[Photograph A on the left side] as compared with those in the case
of the high-velocity oxygen fuel spraying method (HVOF method)
[Photograph B on the right side].
[0067] Based on the photographs of the cross sections of the bond
coat layers, FIG. 5 shows the difference in the pore area per unit
area depending on the combination of various types of bond coat
materials and bond coating methods. As a result, it is known that,
in the case of using the alloy of the invention, BC-1, the pore
area per unit area is extremely small according to any coating
methods. The microscopic characteristic of the alloy of the
invention is considered to provide one reason for the extremely
excellent heat cycle characteristics of the alloy of the invention
as a bond coat material.
[0068] In the heat cycle test of the above-mentioned, three-layered
Ni-based superalloy components, <Example 1L> in which the
bond coat material "BC-1" in Table 1 was formed into the bond coat
layer according to the low-pressure plasma spraying method did not
undergo coating film spallation in the first-try experiment up to
1300 cycles (see FIG. 2); and therefore, as the subsequent
experiment, the heat cycle test of the sample was continued. The
graph of [FIG. 6] shows the results.
[0069] In the graph of [FIG. 6], the fifth bar graph having a
height of 2444 from the left shows that one sample of <Example
1L>, in which the "BC-1" bond coat material in [Table 1] was
formed into the bond coat layer according to the low-pressure
plasma spraying method, underwent coating film spallation after the
life of 2444 cycles. The fourth bar graph having a height of 2098
from the left shows that another sample of <Example 1L>, in
which the "BC-1" bond coat material in [Table 1] was formed into
the bond coat layer according to the low-pressure plasma spraying
method, underwent coating film spallation after the life of 2098
cycles.
[0070] From the results of the two samples, it is obvious that the
heat cycle life of the Ni-based superalloy component having the
heat-resistant bond layer of the invention is sufficiently long and
the reproducibility thereof is good.
[0071] For verifying the reason why the heat cycle life of the
Ni-based superalloy component having the heat-resistant bond layer
of the invention is sufficiently long, the present inventors
compared the three-layered Ni-based superalloy component of the
invention with comparative samples, after 300 cycles in the heat
cycle test in point of the cross section of each sample, based on
the enlarged SEM photographs of the boundary region between the
substrate (1) and the bond coat layer (2).
[0072] As shown in [FIG. 7], it is recognized that, in all the
samples of <Example 1L> of the invention and <Comparative
Example 1L> and <Comparative Example 2L>, the secondary
reaction zone (SRZ) (layer sandwiched between two lines in the
center in each drawing) was formed at the boundary between the
Ni-based superalloy substrate (1) (bottom layer in each drawing)
and the bond coat layer (2) (top layer in each drawing).
[0073] The thickness of the SRZ layer in <Example 1L> (bond
coat material: BC-1) of the invention is from 20 to 30 .mu.m or so,
while the thickness of the SRZ layer in <Comparative Example
1L> (bond coat material: CoNiCrAlY) and <Comparative Example
2L> (bond coat material: NiCoCrAlY) is from 130 to 160 .mu.m or
so and the layer is thick. It is known that, when the conventional
bond coat materials (CoNiCrAlY, NiCoCrAlY) were used, various
elements underwent mutual and active thermal diffusion between the
substrate and the bond coat material, whereby the thick secondary
reaction zone (SRZ) was formed.
[0074] On the other hand, when the Ni-based bond coat material of
the invention was used, mutual diffusion of elements between the
bond coat material and the Ni-based superalloy substrate (1) was
retarded in the heat cycle test and therefore the composition, the
morphology and the function of the bond coat layer could be
sustained as such for a long period of time.
[0075] Subsequently, the present inventors gave in-depth
consideration to the boundary region between the bond coat layer
(2) and the top coat layer (3).
[0076] [FIG. 8] shows enlarged SEM photographs of the region of
bond coat layer (2)/TGO (thermally-grown oxide)/top coat layer (3)
of the cross section of each sample of three-layered Ni-based
superalloy components after 300 cycles of the heat cycle test.
<Example 1L> [Photograph 8A], <Comparative Example 2L>
[Photograph 8B] and <Comparative Example 1L> [Photograph 8C]
did not differ in that the dark TGO (thermally-grown oxide) formed
in the boundary region between the bond coat layer (2) and the top
coat layer (3) in all of these.
[0077] However, in <Example 1 L> [Photograph 8A], the bond
coat layer (2)/TGO (thermally-grown oxide)/top coat layer (3)
mutually adhered to each other with no indication of
spallation.
[0078] When the bond coat material (BC-1) of the invention was
used, the dense TGO (thermally-grown oxide) having good
adhesiveness to other layers was seen after 300 cycles of the heat
cycle test, and the layer having a thickness of 5 .mu.m tended to
be stable.
[0079] On the other hand, it is seen that, in <Comparative
Example 1L> (bond coat material: CoNiCrAlY) [Photograph 8C] and
<Comparative Example 2L> (bond coat material: NiCoCrAlY)
[Photograph 8B], TGO (thermally-grown oxide) was already thicker by
from 1 to 2 .mu.m or so than that in the present invention, after
300 cycles of the heat cycle test, and that in these Comparative
Examples, TGO (thermally-grown oxide) itself was not dense and was
poorly adhesive to the other layers, and there occurred some space
between the TGO (thermally-grown oxide) and the bond coat layer
(2), or that is, in these Comparative Examples, there was
recognized an indication of spallation.
[0080] It is considered that the difference in the microstructure
of TGO (thermally-grown oxide) formed in the interface between the
bond coat layer and the top coat layer would be one contributory
factor for the excellent characteristics of the bond coat material
and the Ni-based superalloy component having the heat-resistant
bond coat layer of the bond coat material of the invention.
[0081] In FIG. 8, the last [Photograph 8D] is an enlarged SEM
photograph of the same region of <Example 1L> after 1000
cycles of the heat cycle test. In this, it is confirmed that TGO
(thermally-grown oxide) further grew to have wedge-shaped oxides
stepping in the bond coat layer (2). The white arrows additionally
given to the photograph are noted. It is considered that these
would be a cause for increasing the adhesiveness between TGO and
the bond coat layer.
[0082] These series of observation results relating to the TGO
microstructure formed in the interface between the bond coat
material and the top coat material obviously show the effectiveness
of the invention.
* * * * *