U.S. patent application number 14/061306 was filed with the patent office on 2014-04-24 for high temperature components with thermal barrier coatings for gas turbine.
This patent application is currently assigned to Hitachi, Ltd.. The applicant listed for this patent is Hitachi, Ltd.. Invention is credited to Hideyuki ARIKAWA, Hiroyuki ENDO, Takao ENDO, Kunihiro ICHIKAWA, Tadashi KASUYA, Yoshitaka KOJIMA, Akira MEBATA.
Application Number | 20140112758 14/061306 |
Document ID | / |
Family ID | 49474259 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140112758 |
Kind Code |
A1 |
ARIKAWA; Hideyuki ; et
al. |
April 24, 2014 |
High Temperature Components With Thermal Barrier Coatings for Gas
Turbine
Abstract
The most principal feature of the present invention is as
follows: Namely, in the gas-turbine-use high-temperature component
including the thermal barrier coating and a cooling structure,
micro passages are provided inside an alloy bond-coat layer and a
thermal-barrier ceramic top-coat layer of the thermal barrier
coating, the micro passages being in communication from the
substrate side to the surface side. Moreover, a partial amount of
coolant of a coolant for cooling the high-temperature component is
caused to flow out to the outside of the high-temperature component
via these micro passages. The employment of the structure like this
makes it possible to expect the implementation of a
high-temperature component's heat-resistant-temperature enhancement
effect based on the transpiration cooling effect.
Inventors: |
ARIKAWA; Hideyuki; (Tokyo,
JP) ; KOJIMA; Yoshitaka; (Tokyo, JP) ; KASUYA;
Tadashi; (Tokyo, JP) ; MEBATA; Akira; (Tokyo,
JP) ; ICHIKAWA; Kunihiro; (Tokyo, JP) ; ENDO;
Hiroyuki; (Tokyo, JP) ; ENDO; Takao; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi, Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Hitachi, Ltd.
Tokyo
JP
|
Family ID: |
49474259 |
Appl. No.: |
14/061306 |
Filed: |
October 23, 2013 |
Current U.S.
Class: |
415/115 |
Current CPC
Class: |
C23C 28/3455 20130101;
C23C 4/08 20130101; C23C 28/3215 20130101; F01D 5/186 20130101;
F01D 5/183 20130101; C23C 4/073 20160101; C23C 24/04 20130101; F01D
5/288 20130101 |
Class at
Publication: |
415/115 |
International
Class: |
F01D 5/28 20060101
F01D005/28; F01D 5/18 20060101 F01D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2012 |
JP |
2012-234278 |
Claims
1. A gas-turbine-use high-temperature component, comprising: a
thermal barrier coating; said thermal barrier coating being formed
by providing an alloy bond-coat layer on a substrate surface
exposed to a high-temperature combustion gas, and further, by
providing a thermal-barrier ceramic top-coat layer on the surface
of said alloy bond-coat layer, wherein micro passages are provided
inside said alloy bond-coat layer and said thermal-barrier ceramic
top-coat layer, said micro passages being in communication from
said substrate side to said surface side, a partial amount of
coolant of a coolant for cooling said high-temperature component
being caused to flow out to the outside of said high-temperature
component via these micro passages.
2. The gas-turbine-use high-temperature component according to
claim 1, wherein said substrate is composed of a heat-resistant
alloy of Ni-base, Co-base, or Fe-base.
3. The gas-turbine-use high-temperature component according to
claim 1, wherein said alloy bond-coat layer is composed of a MCrAlY
(M is at least one species selected from Fe, Ni, and Co) alloy.
4. The gas-turbine-use high-temperature component according to
claim 1, wherein said alloy bond-coat layer is equipped with an
accumulated organization of alloy powder particles, the particle
diameters' range of said alloy powder particles being a 5 .mu.m to
100 .mu.m range, the in-coating-film volume's partial ratio of said
micro passages being equal to 30% to 70%, said micro passages being
formed by clearances among said accumulated particles, and being in
communication.
5. The gas-turbine-use high-temperature component according to
claim 1, wherein said alloy bond-coat layer is formed using a
method of causing alloy powder particlesto collide with said
substrate surface at a high velocity, and without being accompanied
by the melting of said alloy powder particles, said alloy powder
particles being caused to collide with said substrate surface by
accelerating said particles with an action gas whose temperature is
lower than the melting point of said alloy.
6. The gas-turbine-use high-temperature component according to
claim 1, wherein said thermal-barrier ceramic top-coat layer is
formed of partially-stabilized zirconia.
7. The gas-turbine-use high-temperature component according to
claim 1, wherein said micro passages of said thermal-barrier
ceramic top-coat layer are formed of cracks.
8. The gas-turbine-use high-temperature component according to
claim 1, wherein said micro passages of said thermal-barrier
ceramic top-coat layer are formed of pores.
9. A gas turbine, comprising: said gas-turbine-use high-temperature
component as claimed in claim 1.
10. A gas-turbine-combined power-generation plant, comprising: said
gas turbine as claimed in claim 9.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to gas-turbine-use
high-temperature components such as rotor blade and nozzle guide
vane, combustor, and shroud of a gas turbine. Here, each of these
high-temperature components is equipped with a thermal barrier
coating that is excellent in its heat resistivity.
[0002] The operation temperature of a gas turbine has been becoming
increasingly higher year by year with the purpose of enhancing its
efficiency. In order to address this high-temperature trend of the
operation temperature, materials that are excellent in the heat
resistivity are used for each of the gas-turbine-use
high-temperature components. In addition, in each high-temperature
component, the structure is employed where the opposite plane to a
plane exposed to a high-temperature combustion gas is cooled using
a fluid coolant such as air or steam. Moreover, with the purpose of
relaxing the temperature environment, the thermal barrier coating
(which, hereinafter, will be referred to as "TBC") composed of a
low-thermal-conductivity ceramics is usually applied to the surface
of each high-temperature component. This application of the TBC
generally makes it possible to lower the substrate temperature by
the amount of 50.degree. to 100.degree. C., although it depends on
the usage conditions as well. For example, in documents such as
JP-A-62-211387, there is disclosed a TBC where a thermal barrier
layer is provided for the substrate with a MCrAlY alloy layer
positioned therebetween. Here, this thermal barrier layer is
composed of low-thermal-conductivity and excellent-heat-resistivity
partially-stabilized zirconia. Furthermore, here, M denotes at
least one species selected from a group of iron (Fe), Ni, and Co.
Also, Cr, Al, and Y denote chromium, aluminum, and yttrium,
respectively.
[0003] Each gas-turbine-use high-temperature component like this,
which is equipped with the TBC and the cooling structure, exhibits
the excellent heat resistivity. Nevertheless, with an intention of
enhancing the gas turbine's performance even further, it is desired
to employ a transpiration cooling scheme that allows implementation
of a higher cooling efficiency. The transpiration cooling is a
method for allowing the cooling to be performed with the higher
efficiency in accordance with the following manner: Namely, in this
transpiration cooling, the uniform transpiration of a slight amount
of cooling medium is caused to occur from the entire surface of
each high-temperature component via micro flow channels (i.e.,
porous material in general). For example, in JP-A-10-231704 and
JP-A-2010-65634, there are disclosed gas-turbine-use
high-temperature components where the transpiration cooling
structure based on a porous ceramic layer is employed on a porous
metal. Also, in JP-A-2005-350341, there is disclosed the following
gas-turbine-use high-temperature component: The transpiration
cooling structure is employed in the structure where a porous
ceramic and a heat-resistant alloy substrate are integrated at the
time of the casting.
SUMMARY OF THE INVENTION
[0004] In the above-described conventional technologies, the
thermal-barrier ceramic top-coat layer of the TBC is employed
partially. In whatever of the above-described patent publications,
however, the layer corresponding to an alloy bond-coat layer of the
TBC is not a coating film, but is alternatively replaced by the
porous metal. Otherwise, the very layer corresponding to the alloy
bond-coat layer is omitted. This is because it is difficult to form
the micro passages, which become the flow channels of the cooling
medium, with the use of the conventional film-forming methods for
forming the alloy bond-coat layer. In the TBC, the thermal-barrier
ceramic top-coat layer is put in charge of a role of becoming a
barrier to the heat from the high-temperature combustion gas.
Accordingly, this ceramic top-coat layer can be expected to exhibit
an effect of suppressing the apparent thermal conductivity down to
a low value, and further, an effect of relaxing the thermal stress.
For this reason, the porous ceramic layer is employed as this
ceramic top-coat layer. Meanwhile, the alloy bond-coat layer is put
in charge of a role of ensuring the close contact between the
ceramic top-coat layer and the substrate. Simultaneously, the alloy
bond-coat layer is put in charge of a role of protecting the
substrate from the oxidization and corrosion due to the combustion
gas. For these reasons, more densely-packed organizations are
employed as the alloy bond-coat layer. On account of these
circumstances, the implementation of each high-temperature
component where the TBC and the transpiration cooling are combined
with each other requires implementation of the following alloy
bond-coat layer: Namely, an alloy bond-coat layer is required which
is equipped with the cooling medium's flow channels that are
different from the ones in the conventional technologies. In view
of this situation, an object of the present invention is as
follows: Namely, an alloy bond-coat layer is implemented which is
equipped with the cooling medium's micro flow channels that are
appropriate and suitable for the transpiration cooling. Moreover,
there is provided each excellent-heat-resistivity gas-turbine-use
high-temperature component that is equipped with the
transpiration-cooling function and the thermal barrier coating
where this alloy bond-coat layer is employed.
[0005] In view of the above-described problem, the most principal
feature of the present invention is as follows: In a
gas-turbine-use high-temperature component including a thermal
barrier coating, and a cooling structure based on a fluid coolant,
the thermal barrier coating being formed by providing an alloy
bond-coat layer on a substrate's surface exposed to a
high-temperature combustion gas, and further, by providing a
thermal-barrier ceramic top-coat layer on the surface of the alloy
bond-coat layer, micro passages are provided inside the alloy
bond-coat layer and the thermal-barrier ceramic top-coat layer, the
micro passages being in communication from the substrate side to
the surface side, a partial amount of fluid coolant of the fluid
coolant for cooling the high-temperature component being caused to
flow out to the outside of the high-temperature component via these
micro passages.
[0006] In the present invention, the micro passages are provided
inside the alloy bond-coat layer and the thermal-barrier ceramic
top-coat layer of the TBC, the micro passages being in
communication from the substrate side to the surface side.
Moreover, a partial amount of fluid coolant of the fluid coolant
for cooling the high-temperature component is caused to flow out to
the outside of the high-temperature component via these micro
passages. This feature makes it possible to cool the TBC, and the
alloy bond-coat layer in particular, with a higher efficiency.
Also, the uniform transpiration of the coolant is caused to occur
from the entire surface of the high-temperature component. This
feature makes it possible to expect the implementation of a uniform
and efficient film-cooling effect. On account of these effects,
there exists an advantage of becoming capable of using the
component even under such a hash and severe condition that the
application of the conventional technologies becomes difficult due
to a rise in the component temperature in accompaniment with the
higher-temperature implementation of the combustion-gas
temperature. Also, in the gas turbine that uses the gas-turbine-use
high-temperature component including the thermal barrier coating
and the cooling structure of the present invention, there exists an
advantage of being capable of operating the gas turbine at a higher
temperature, and of becoming able to enhance the efficiency.
[0007] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross-sectional schematic diagram for
illustrating the structure of a gas-turbine-use high-temperature
component including the thermal barrier coating and the cooling
structure of the present invention; and
[0009] FIG. 2 is a cross-sectional schematic diagram for
illustrating the structure of a gas turbine.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0010] Hereinafter, referring to the drawings, the detailed
explanation will be given below concerning the present
invention.
[0011] As illustrated in FIG. 1, the configuration of the present
invention is as follows: Namely, an alloy bond-coat layer 2 is
provided on a substrate 1. Moreover, a thermal-barrier ceramic
top-coat layer 3 is provided on this alloy bond-coat layer 2. In
the substrate 1, a plurality of cooling holes 4, which penetrate
the substrate 1, are provided in the direction from cooling-medium
passages of the substrate 1 to the surface of the substrate 1 on
which the alloy bond-coat layer 2 is provided. The alloy bond-coat
layer 2 is characterized by being equipped with the following
structure: Namely, in this structure, a large number of
basically-spherical alloy powder particles 5 are accumulated.
Moreover, there exist among-particles clearances 6 that are in
communication from the side of the substrate 1 to that of the
coating surface. Furthermore, the thermal-barrier ceramic top-coat
layer 3 is provided on the surface of the alloy bond-coat layer 2.
The thermal-barrier ceramic top-coat layer 3 is equipped with a
large number of vertical-direction cracks 7. A fluid coolant 8
reaches the alloy bond-coat layer 2 from the cooling-medium
passages of the substrate 1 via the cooling holes 4. Subsequently,
the fluid coolant 8 flows upward onto the surface side of the alloy
bond-coat layer 2, and reaches the thermal-barrier ceramic top-coat
layer 3, while diffusing inside the alloy bond-coat layer 2 via the
among-particles clearances 6 inside the layer 2. Finally, the fluid
coolant 8 flows out from the surface of the thermal-barrier ceramic
top-coat layer 3 via the vertical-direction cracks 7 inside the
thermal-barrier ceramic top-coat layer 3.
[0012] The substrate 1 can be composed of a heat-resistant alloy of
Ni-base, Co-base, or Fe-base. The alloy bond-coat layer 2 can also
be composed of the Ni-base, Co-base, or Fe-base heat-resistant
alloy. Preferably, however, it is desirable to use the MCrAlY (M
denotes whatever of, or plural pieces of Fe, Ni, and Co) alloy. The
MCrAlY alloy is preferable, because it is excellent in the
oxidation-resistant property.
[0013] Also, the alloy bond-coat layer 2 is equipped with the
following structure: Namely, the large number of
basically-spherical alloy powder particles 5 are accumulated
therein. Moreover, there exist the among-particles clearances 6
that are in communication from the side of the substrate 1 to the
surface of the alloy bond-coat layer 2. In order to form the
coating film of the structure like this, it is preferable to use
the following method, for example: Namely, the basically-spherical
alloy powder produced using the gas atomization method is employed
as the raw material. Then, the alloy powder is accumulated by being
caused to collide with the substrate surface at a high velocity.
Concretely, the usable methods are ones such as, e.g., the plasma
spray method, the high-velocity oxy-fuel spray (HVOF) method, and
the cold spray method. Of these methods, the cold spray method is
used most preferably.
[0014] The feature of the present invention is the alloy bond-coat
layer 2 that is equipped with the structure where there exist the
among-particles clearances 6. Here, the among-particles clearances
6 are in communication from the side of the substrate 1 to the
coating surface. In order to form this alloy bond-coat layer 2,
consideration is given to the following case: The method such as
the electric arc spray or flame spray is used, where the alloy
powder particles are accumulated by being melted at a high
temperature, and by being caused to collide with the substrate. In
this case, however, pores (i.e., the so-called "closed pores") that
are not in communication become likely to be formed. This is
because the melted alloy powder particles are accumulated in a
manner of becoming significantly flattened when these particles
collide with the substrate. Also, in the alloy powder that is
heated up to the temperature at which the alloy powder is melted in
the atmosphere, its oxides are produced on its surface. These
oxides are mixed into the coating film, thereby lowering the
oxidation-resistant property of the coating film. Also, there
occurs a problem that the coupling among the particles is
obstructed by the oxides, and that the strength of the coating film
is lowered thereby.
[0015] Consequently, when forming the alloy bond-coat layer 2 of
the thermal barrier coating of the present invention, the following
accumulation method is desirable: Namely, the basically-spherical
alloy powder to be used as the raw material is accumulated without
melting and oxidizing the basically-spherical alloy powder, i.e.,
while maintaining its shape as it is that is close to the spherical
shape. The method preferable for this accumulation method is the
cold spray method, which allows the film formation to be performed
at a lower temperature. Even at the lower temperature, however, if
the velocities of the powder particles become too high, the
flattening of the powder particles is caused to occur when these
particles collide with the substrate. As a result, the coating film
becomes densely-packed, and thus the number of the communication
pores is decreased. This undesirable situation makes it impossible
to form the alloy bond-coat layer 2 of the present invention,
thereby making it necessary to adjust the film-forming conditions
properly. Incidentally, by adjusting the film-forming conditions
similarly depending on the requirements, it also becomes possible
to use the methods such as the plasma spray method and the
high-velocity oxy-fuel spray (HVOF) method.
[0016] It is preferable that the in-coating-film volume's partial
ratio of the communication clearances of the alloy bond-coat layer
2 of the present invention falls into a range of 30% to 70%. Here,
the alloy bond-coat layer 2 is formed using the above-described
film-forming method, and is equipped with the among-particles
clearances 6 that are in communication from the side of the
substrate 1 to the side of the coating surface. If the volume's
partial ratio of the clearances is less than 30%, the
cooling-medium amount being in communication becomes smaller.
Accordingly, the effect of the transpiration cooling cannot be
obtained sufficiently. Meanwhile, if the volume's partial ratio of
the clearances increases, the coating-film strength is lowered,
although the cooling effect is enhanced. If the volume's partial
ratio of the clearances exceeds 70%, the damage to the coating
becomes likely to occur while operating gas turbine. It is more
preferable that the volume's partial ratio of the clearances falls
into a range of 40% to 60%.
[0017] Also, it is preferable that, in association with the thermal
barrier coating of the present invention, a thermal processing is
applied to both of the alloy bond-coat layer 2 and the
thermal-barrier ceramic top-coat layer 3 after the film formation
is over. In the alloy bond-coat layer 2, the coating-film strength
can be enhanced by strengthening the coupling among the particles
through the thermal-processing-based solid-phase diffusion. Also,
in the thermal-barrier ceramic top-coat layer 3, it can be expected
to make the circulation of the cooling medium smoother by
positively permitting the vertical-direction cracks 7 to be
implemented as wider apertures. It is desirable that the heat
treatment is performed in vacuum in order to prevent the oxidation
of the alloy bond-coat layer 2. Furthermore, it is preferable that
the heat treatment conditions are maintained, approximately, at a
1000.degree. C-or-higher temperature and during a 2 hour-or-longer
time-interval. These conditions, however, depend on the coating and
the substrate material as well. Incidentally, it is preferable that
the structure of the thermal-barrier ceramic top-coat layer 3
includes the large number of vertical-direction cracks 7. It is
also possible, however, that a porous structure, to which
ventilation is imparted by a large number of pores, is employed as
the structure of the layer 3.
[0018] Hereinafter, the explanation will be given below concerning
embodiments of the present invention.
Embodiment 1
[0019] A gas-turbine first-stage rotor blade, which includes
cooling-air passages in its inside, is prepared as the base
substrate. Here, this rotor blade is formed of a Ni-base
heat-resistant alloy IN738 (: 16% Cr--8.5% Co--3.4% Ti--3.4%
Al--2.6% W--1.7% Mo--1.7% Ta--0.9% Nb--0.1% C--0.05% Zr--0.01%
B--the remaining portion: Ni, weight %). In the rotor blade,
pluralities of cooling pores, which penetrate the base substrate
from its surface to the internal cooling-air passages, are machined
using discharge machining Also, basically-spherical and about-40
.mu.m-average-diameter CoNiCrAlY alloy powder (: Co--32% Ni--21%
Cr--8% Al--0. 5% Y, weight%), which is produced using the gas
atomization method, is prepared as the raw-material powder.
Moreover, using a cold spray device, the raw-material powder is
film-formed onto the combustion-gas passage surface of the rotor
blade. This film formation is carried out until the thickness of
the alloy bond-coat layer 2 becomes equal to about 0.3 mm. The
film-forming conditions set at this time are as follows: Nitrogen
gas as the operating gas, 3 MPa gas pressure, 800.degree. C. gas
temperature, 20 g/min powder feed rate, and 15 mm spray distance.
After that, the thermal-barrier ceramic top-coat layer 3 is
provided above the substrate 1 on which the alloy bond-coat layer 2
is provided, using yttria partially-stabilized zirconia (:
ZrO.sub.2--8-wt % Y.sub.2O.sub.3) powder, and the in-atmosphere
plasma spray (whose plasma output is equal to about 100 kW) method.
Here, this thermal-barrier ceramic top-coat layer 3 is so provided
as to become about 0.6 mm thick, and as to include the
about-8%-pore-ratio vertical-direction cracks. The film-forming
conditions set at this time are as follows: About-800.degree. C.
residual-heat temperature, 30 m/min spray gun's transverse speed,
90 mm spray distance, and about-0.4 MW/m.sup.2 heat flux.
Furthermore, with respect to the rotor blade on which the film
formation of the thermal-barrier ceramic top-coat layer 3 is
completed, 1120.degree. C..times.2 h and 840.degree. C..times.24 h
heat treatments are carried out in vacuum.
[0020] The rotor blade manufactured in this way is cut off, and
then its cross-sectional organization is confirmed. This
confirmation result shows that, as illustrated in FIG. 1, the alloy
bond-coat layer 2 presents the following organization: Namely, the
large number of basically-spherical alloy powder particles 5 are
accumulated therein. Moreover, there exist the among-particles
clearances 6 that are in communication from the side of the
substrate 1 to the surface of the alloy bond-coat layer 2.
Measuring the volume's partial ratio of the pores from the relative
density results in the value of about 50%.
[0021] A different test rotor blade manufactured in accordance with
the above-described processing steps is integrated into the gas
turbine, and then a 1-year test operation thereof is performed. At
this time, an orifice is provided at a cooling-air entrance of the
blade, thereby reducing the cooling-air amount by 30% as compared
with the conventional designs. In the after-test-operation rotor
blade on which the TBC of the present invention is set up, the
damage has been seldom recognized in both the outer appearance and
the cut-off check. Meanwhile, in a comparison-dedicated rotor blade
on which the TBC of the conventional technologies is set up, and
whose operation is performed simultaneously with the cooling-air
amount reduced, exfoliation of the TBC has been partially
recognized from the outer appearance. Furthermore, in the cut-off
check, the oxidization and damage of the alloy bond-coat layer 2
has been recognized in portions other than the exfoliated portion.
From these results, it has been confirmed that each gas-turbine-use
high-temperature component on which the TBC of the present
invention is set up exhibits the excellent heat resistivity.
Embodiment 2
[0022] FIG. 2 is a cross-sectional schematic diagram for
illustrating the main part of a power-generation-use gas turbine.
This gas turbine includes, inside a turbine casing 48, a turbine
rotor 49 in its center, and a turbine unit 44. Moreover, this
turbine unit 44 is equipped with turbine rotor blades 46 which are
set up in the surroundings of the turbine rotor 49, and turbine
nozzle guide vanes 45 and turbine shrouds 47 which are supported
onto the side of the turbine casing 48. The gas turbine further
includes a compressor 50 and a combustor 40. The compressor 50 is
connected to this turbine unit 44, and absorbs the atmosphere,
thereby obtaining a combustion-use and cooling-medium-use
compressed air. The combustor 40 is equipped with a combustor
nozzle 41 for mixing with each other the compressed air supplied
from the compressor 50 and a (not-illustrated) fuel supplied, and
for injecting this mixed gas. The combustor 40 combusts this mixed
gas inside a combustor liner 42, thereby generating a
high-temperature and high-pressure combustion gas. This
high-temperature and high-pressure combustion gas is supplied to
the turbine unit 44 via a transition piece 43. This supply of the
combustion gas allows the turbine rotor 49 to be rotated at a high
speed. Furthermore, a partial portion of the compressed air outlet
from the compressor 50 is used as an inside-cooling air for cooling
the combustor liner 42, the transition piece 43, the turbine nozzle
guide vanes 45, and the turbine rotor blades 46. The
high-temperature and high-pressure combustion gas generated inside
the combustor 40 is smoothly flown by the turbine nozzle guide
vanes 45 via the transition piece 43, then being injected onto the
turbine rotor blades 46. This injection of the combustion gas
allows the implementation of the rotational driving of the turbine
unit 44. In addition, although not illustrated, the
power-generation-use gas turbine is so configured as to serve the
power generation using a power generator that is connected to the
end portion of the turbine rotor 49.
[0023] The present embodiment is configured as follows: Namely, the
TBC of the present invention, which is explained in the first
embodiment described earlier, is added to the rotor blades 46.
Moreover, the TBC is provided on the nozzle guide vanes 45 and the
combustion-gas passage surface of the first-stage shroud 47, using
a method in accordance with the method explained in the first
embodiment. Concretely, a plurality of cooling holes , which
penetrate the base substrate from its surface to the internal
cooling-air passages, are machined onto the combustion-gas passage
surface of each gas-turbine component, using the discharge
machining Also, basically-spherical and about-50
.mu.m-average-diameter NiCoCrAlY alloy powder (: Ni--23% Co--17%
Cr--12.5% Al--0.5% Y, weight %), which is produced using the gas
atomization method, is prepared as the raw-material powder.
Moreover, using the cold spray device, the raw-material powder is
film-formed onto the combustion-gas passage surface of each
gas-turbine component. This film formation is carried out until the
thickness of the alloy bond-coat layer 2 becomes equal to about 0.3
mm. The film-forming conditions set at this time are as follows:
Nitrogen gas as the operating gas, 3 MPa gas pressure, 900.degree.
C. gas temperature, 15 g/min powder feed rate, and 20 mm
film-forming distance. After that, an about-0.3 mm-thick and
ventilation-imparted porous thermal-barrier ceramic top-coat layer
is provided above the substrate 1 on which the alloy bond-coat
layer 2 is provided, using yttria partially-stabilized zirconia (:
ZrO.sub.2--8-wt % Y.sub.2O.sub.3) powder, and the in-atmosphere
plasma spray (whose plasma output is equal to about 50 kW) method.
The film-forming conditions set at this time are as follows:
About-150.degree. C. residual-heat temperature, 45 m/min spray
gun's transverse speed, and 100 mm spray distance. Furthermore, an
in-vacuum thermal processing in accordance with the
thermal-processing conditions of the alloy used as the substrate of
each gas-turbine component is carried out with respect to each
component on which the film formation of the thermal-barrier
ceramic top-coat layer is completed.
[0024] Incidentally, in the present embodiment, the configuration
where the TBC of the present invention is provided is applied only
to each first stage of the nozzle guide vanes 45, the rotor blades
46, and the shrouds 47 of the three-stage turbine unit 44. It is
also possible, however, to apply this configuration further to the
subsequent stages, i.e., the second and third stages. Furthermore,
it is also possible to apply this configuration to every stage or
selected stage of the turbine that is configured with another stage
number, e.g., the turbine configured with two or four stages. In
the above-described-configuration-based gas turbine according to
the present embodiment, the gas-turbine components where the TBC of
the present invention is provided are operated with the cooling-air
amount reduced by about 30%. After a 2 year operation thereof, each
gas-turbine component is observed. This observation shows that, in
the gas-turbine components where the TBC of the present invention
is provided, the damage has been seldom recognized in the TBC,
i.e., the TBC remains basically sound. Meanwhile, there has been an
enhancement in the efficiency of the gas turbine because of the
reduction in the cooling-air amount. Also, there has been an
enhancement in the power-generation efficiency of a
gas-turbine-combined power-generation plant where this gas turbine
is set up.
[0025] From the above-described results, it has been found that the
gas turbine according to the present embodiment is made operable at
a high temperature by the excellent heat resistivity of its
high-temperature components. As a consequence, this gas turbine is
excellent in its economy and stable operability.
[0026] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
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