U.S. patent application number 13/678763 was filed with the patent office on 2014-05-22 for methods of fabricating and coating turbine components.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Ronald Scott Bunker, John Wesley Harris, JR..
Application Number | 20140137408 13/678763 |
Document ID | / |
Family ID | 50726589 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140137408 |
Kind Code |
A1 |
Bunker; Ronald Scott ; et
al. |
May 22, 2014 |
METHODS OF FABRICATING AND COATING TURBINE COMPONENTS
Abstract
In one aspect, a method of forming a hot gas path component is
provided. The method includes forming at least one groove in an
outer surface of a substrate, wherein the at least one groove has a
base and a top. The method further includes filling the at least
one groove with a filler. The method also includes applying at
least one cover layer over at least a portion of the outer surface
of the substrate such that the at least one groove and the at least
one cover layer define at least one micro-channel for cooling the
component. The filler is automatically removed from the at least
one micro-channel during application of the at least one cover
layer. Methods for coating a hot gas component and for assembling a
turbine engine assembly are also provided.
Inventors: |
Bunker; Ronald Scott;
(Waterford, NY) ; Harris, JR.; John Wesley;
(Taylors, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY; |
|
|
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
50726589 |
Appl. No.: |
13/678763 |
Filed: |
November 16, 2012 |
Current U.S.
Class: |
29/889.2 ;
427/264; 427/448; 427/569 |
Current CPC
Class: |
F05D 2230/14 20130101;
Y02T 50/676 20130101; F05D 2230/313 20130101; Y10T 29/4932
20150115; Y02T 50/672 20130101; F01D 5/288 20130101; F05D 2230/312
20130101; Y02T 50/60 20130101; F01D 5/186 20130101 |
Class at
Publication: |
29/889.2 ;
427/264; 427/569; 427/448 |
International
Class: |
F01D 25/12 20060101
F01D025/12 |
Claims
1. A method of forming a hot gas path component, the method
comprising: forming at least one groove in an outer surface of a
substrate, wherein the at least one groove has a base and a top;
filling the at least one groove with a filler; and applying at
least one cover layer over at least a portion of the outer surface
of the substrate such that the at least one groove and the at least
one cover layer define at least one micro-channel for cooling the
component, wherein the filler is automatically removed from the at
least one micro-channel during application of the at least one
cover layer.
2. The method in accordance with claim 1, wherein forming at least
one groove in an outer surface of a substrate comprises forming the
base within a range between approximately 0.5 millimeters (mm) and
approximately 1.27 mm below the outer surface of the substrate.
3. The method in accordance with claim 1, wherein forming at least
one groove in an outer surface of a substrate comprises forming the
width of the top within a range between approximately 0.127 mm to
approximately 0.4 mm wide.
4. The method in accordance with claim 1, wherein forming at least
one groove in an outer surface of a substrate comprises forming the
base wider than the top such that the at least one groove forms at
least one trapezoidal-shaped shaped groove.
5. The method in accordance with claim 4, wherein the base of the
at least one trapezoidal-shaped shaped groove is at least 2 times
wider than the top of the at least one trapezoidal-shaped shaped
groove.
6. The method in accordance with claim 1, wherein applying at least
one cover layer comprises applying the at least one cover layer
wherein the at least one cover layer completely bridges the at
least one groove such that the at least one cover layer seals the
at least one micro-channel.
7. The method in accordance with claim 1, wherein applying at least
one cover layer comprises performing at least one of an ion plasma
deposition process, a high velocity oxygen fuel (HVOF) spray
process, a high velocity air fuel (HVAF) spray process, and a low
pressure plasma spray (LPPS) process.
8. A method of coating a hot gas path component including a
substrate, wherein at least one groove is formed in an outer
surface of the substrate, the method comprising: filling the at
least one groove with a filler; and applying at least one cover
layer over at least a portion of the outer surface of the
substrate, such that the at least one groove and the at least one
cover layer define at least one micro-channel for cooling the
component, wherein the filler is automatically removed from the at
least one micro-channel during application of the at least one
cover layer.
9. The method in accordance with claim 8, wherein applying at least
one cover layer comprises applying the at least one cover layer
wherein the at least one cover layer completely bridges the at
least one groove such that the at least one cover layer seals the
at least one micro-channel.
10. The method in accordance with claim 8, wherein applying at
least one cover layer comprises performing an ion plasma deposition
process.
11. The method in accordance with claim 8, wherein applying at
least one cover layer comprises performing a thermal spray
process.
12. The method in accordance with claim 11, wherein the thermal
spray process is at least one of high velocity oxygen fuel (HVOF)
spraying and high velocity air fuel (HVAF) spraying.
13. The method in accordance with claim 8, wherein applying at
least one cover layer comprises performing a low pressure plasma
spray (LPPS) process.
14. A method of assembling a turbine engine assembly, said method
comprising: providing a turbine engine including a compressor, a
combustor, and a turbine; and coupling at least one hot gas path
component to the turbine engine, comprising: forming at least one
groove in an outer surface of the hot gas path component; filling
the at least one groove with a filler; and depositing at least one
structural coating over at least a portion of the outer surface of
the hot gas path component, such that the at least one groove and
the at least one structural coating define at least one
micro-channel for cooling the hot gas path component, wherein the
filler is automatically removed from the at least one micro-channel
during deposition of the at least one structural coating.
15. The method in accordance with claim 14, wherein depositing at
least one structural coating comprises depositing at least one of a
nickel-based alloy and a cobalt-based alloy.
16. The method in accordance with claim 14, further comprising heat
treating the hot gas path component.
17. The method in accordance with claim 14, further comprising
applying an oxidation-resistant coating to at least one of the at
least one micro-channel and the outer surface of the hot gas path
component.
18. The method in accordance with claim 14, wherein forming at
least one groove in an outer surface of the hot gas path component
comprises forming the at least one groove using at least one of
abrasive liquid jet machining, plunge electrochemical machining
(ECM), and milling electrical discharge machining (milling
EDM).
19. The method in accordance with claim 14, wherein depositing at
least one structural coating comprises performing at least of an
ion plasma deposition process, a high velocity oxygen fuel (HVOF)
spray process, a high velocity air fuel (HVAF) spray process, and a
low pressure plasma spray (LPPS) process.
20. The method in accordance with claim 14, wherein depositing at
least one structural coating comprises depositing at least one
structural coating wherein the at least one structural coating
completely bridges the at least one groove such that the at least
one structural coating seals the at least one micro-channel.
Description
BACKGROUND
[0001] The embodiments described herein relate generally to turbine
engines, and, more specifically, to fabricating components with
micro-channel cooling therein.
[0002] In a turbine engine, air is pressurized in a compressor and
mixed with fuel in a combustor for generating hot combustion gases.
Energy is extracted from the gases in a high pressure turbine
(HPT), which powers the compressor, and in a low pressure turbine
(LPT), which powers a fan in a turbofan aircraft engine
application, or powers an external shaft for marine and industrial
applications.
[0003] Engine efficiency increases with temperature of combustion
gases. However, the combustion gases heat the various components
along their flow path, which in turn requires cooling thereof to
achieve a long engine lifetime. Typically, the hot gas path
components are cooled by bleeding air from the compressor. This
cooling process reduces engine efficiency, as the bled air is not
used in the combustion process.
[0004] In exemplary turbine engine components, thin metal walls of
high strength superalloy metals are typically used for enhanced
durability while minimizing the need for cooling thereof. Various
cooling circuits and features are tailored for these individual
components in their corresponding environments in the engine. For
example, a series of internal cooling passages, or serpentines, may
be formed in a hot gas path component. A cooling fluid may be
provided to the serpentines from a plenum, and the cooling fluid
may flow through the passages, cooling the hot gas path component
substrate and coatings. However, this cooling strategy typically
results in comparatively low heat transfer rates and non-uniform
component temperature profiles.
BRIEF DESCRIPTION
[0005] In one aspect, a method of forming a hot gas path component
is provided. The method includes forming at least one groove in an
outer surface of a substrate, wherein the at least one groove has a
base and a top. The method further includes filling the at least
one groove with a filler. The method also includes applying at
least one cover layer over at least a portion of the outer surface
of the substrate such that the at least one groove and the at least
one cover layer define at least one micro-channel for cooling the
component. The filler is automatically removed from the at least
one micro-channel during application of the at least one cover
layer.
[0006] In another aspect, a method of coating a hot gas path
component including a substrate with at least one groove formed in
an outer surface of the substrate is provided. The method includes
filling the at least one groove with a filler. The method also
includes applying at least one cover layer over at least a portion
of the outer surface of the substrate such that the at least one
groove and the at least one cover layer define at least one
micro-channel for cooling the component. The filler is
automatically removed from the at least one micro-channel during
application of the at least one cover layer.
[0007] In yet another aspect, a method of assembling a turbine
engine assembly is provided. The method includes providing a
turbine engine including a compressor, a combustor, and a turbine.
The method also includes coupling at least one hot gas path
component to the turbine engine including forming at least one
groove in an outer surface of the hot gas path component. The
method includes filling the at least one groove with a filler.
Additionally, the method includes depositing at least one
structural coating over at least a portion of the outer surface of
the hot gas path component such that the at least one groove and
the at least one structural coating define at least one
micro-channel for cooling the hot gas path component. The filler is
automatically removed from the at least one micro-channel during
deposition of the at least one structural coating.
DRAWINGS
[0008] FIG. 1 is a block diagram of an exemplary rotary
machine.
[0009] FIG. 2 is a schematic cross-section of an exemplary hot gas
path component configuration with trapezoidal-shaped cooling
channels.
[0010] FIG. 3 is a schematic cross-section of a portion of a
cooling circuit of the hot gas path component of FIG. 2 with
re-entrant cooling channels.
[0011] FIG. 4 is a schematic cross-section of a portion of the hot
gas path component of FIG. 2 with the micro-channels filled with a
filler material.
[0012] FIG. 5 is a schematic perspective view of the hot gas path
component of FIG. 2 showing three micro-channels that extend
partially along the surface of the substrate and channel cooling
fluid to respective film cooling holes.
[0013] FIG. 6 is a schematic cross-section of one of the
micro-channels of FIG. 5 showing the micro-channel conveying
cooling fluid from an access hole to a film cooling hole.
[0014] Although specific features of various embodiments may be
shown in some drawings and not in others, this is for convenience
only. Any feature of any drawing may be referenced and/or claimed
in combination with any feature of any other drawing.
DETAILED DESCRIPTION
[0015] The present disclosure is directed generally to rotary
machine components, particularly hot gas path components, formed
with cooling features, such as micro-channels, to facilitate
cooling of the respective components. In particular, aspects of the
present disclosure are directed to methods of forming
micro-channels in a hot gas path component for use in a turbine
engine where a filler material used during formation of the
micro-channels is automatically removed during the formation
process.
[0016] FIG. 1 is a block diagram of an exemplary rotary machine 10,
i.e., a turbomachine, and more specifically, a turbine engine. In
the exemplary embodiment, rotary machine 10 is a gas turbine
engine. Alternatively, rotary machine 10 is any other turbine
engine and/or rotary machine, including, without limitation, a
steam turbine engine. In the exemplary embodiment, turbine engine
10 includes at least one compressor 12, combustor 14, turbine 16,
and fuel nozzle 20. Fuel nozzle 20 is configured to inject and mix
fuel with compressed air in combustor 14. Combustor 14 ignites and
combusts the fuel-air mixture and then passes hot gas flow 22 into
turbine 16. Turbine 16 includes one or more stators having fixed
vanes or blades, and one or more rotors having blades that rotate
relative to the stators. Hot gas flow 22 passes over the turbine
rotor blades, thereby driving the turbine rotor to rotate. Turbine
16 is coupled to rotatable shaft 18 where it rotates the shaft as
hot gas flow 22 passes over the turbine blades. Rotatable shaft 18
may be coupled to compressor 12, as illustrated. Compressor 12
includes blades rigidly mounted to a rotor that is driven to rotate
by rotatable shaft 18. As air passes over the rotating blades, air
pressure increases, thereby providing combustor 14 with sufficient
air for proper combustion.
[0017] Turbine engine 10 may include a plurality of hot gas path
components 100 (shown in FIG. 2). Hot gas path component 100 is any
component of turbine engine 10 that is at least partially exposed
to a high temperature flow of gas through turbine engine 10. For
example, bucket assemblies (also known as blades or blade
assemblies), nozzle assemblies (also known as vanes or vane
assemblies), shroud assemblies, transition pieces, retaining rings,
and compressor exhaust components are all hot gas path components.
It is understood, however, that hot gas path component 100 is not
limited to the above examples, but may be any component that is at
least partially exposed to a high temperature flow of gas. Further,
it is understood that hot gas path component 100 is not limited to
components in turbine engine 10, but may be any piece of machinery
or component that may be exposed to high temperature gas flows.
[0018] When hot gas path component 100 is exposed to hot gas flow
22, hot gas path component 100 is heated by hot gas flow 22 and may
reach a temperature at which hot gas path component 100 fails. A
cooling system for hot gas path component 100 is provided to allow
turbine engine 10 to operate with hot gas flow 22 at a high
temperature, and to increase the efficiency and performance of
turbine engine 10.
[0019] A method of coating hot gas path component 100 is described
with reference to FIGS. 2-6. As indicated for example in FIGS. 3
and 4, the method includes forming one or more grooves 132 in a
substrate 110. In one embodiment, multiple grooves 132 are formed
in substrate 110. As indicated, for example in FIGS. 5 and 6,
grooves 132 extend at least partially along an outer surface 112 of
substrate 110. As indicated for example in FIG. 4, the method
further includes filling grooves 132 with a filler material 120.
Furthermore, as shown for example in FIG. 3, the method further
includes depositing a coating 150 over at least a portion of outer
surface 112 of substrate 110. More particularly, coating 150 is
deposited over at least a portion of outer surface 112 of substrate
110 directly over grooves 132, whereby filler material 120 is
automatically removed during the deposition process.
[0020] FIG. 2 is a schematic cross-section of an exemplary hot gas
path component configuration with trapezoidal-shaped cooling
channels (also referred to as re-entrant shaped cooling channels).
Hot gas path component 100 includes substrate 110 with an outer
surface 112 and an inner surface 116. Inner surface 116 defines at
least one hollow, interior space 114. Outer surface 112 defines one
or more grooves 132. Hot gas path component 100 includes a coating
150 that may include one or more layers 50. Grooves 132 and coating
150 together define a number of micro-channels 130 for cooling the
hot gas path component 100. A cooling fluid may be provided to
micro-channels 130 from the interior space 114, and the cooling
fluid may flow through the micro-channels to cool coating 150.
[0021] Substrate 110 is typically cast prior to forming grooves 132
in outer surface 112 of the substrate. Substrate 110 may be formed
from any suitable material, described herein as a "first material."
Depending on the intended application for hot gas path component
100, the first material may include Ni-base, Co-base, and Fe-base
superalloys, and the like. The Ni-base superalloys may be those
containing both .gamma. and .gamma.' phases, particularly those
Ni-base superalloys containing both .gamma. and .gamma.' phases
wherein the .gamma.' phase occupies at least 40% by volume of the
superalloy. Such alloys are known to be advantageous because of a
combination of desirable properties including high temperature
strength and high temperature creep resistance. The first material
may also include a NiAl intermetallic alloy, as these alloys are
also known to possess a combination of superior properties
including high temperature strength and high temperature creep
resistance that are advantageous for use in turbine engine
applications used for aircraft. In the case of Nb-base alloys,
coated Nb-base alloys having superior oxidation resistance will be
preferred, such as Nb/Ti alloys, and particularly those alloys
comprising Nb-(27-40)Ti-(4.5-10.5)Al-(4.5-7.9)Cr-(1.5-5.5)Hf-(0-6)V
in an atom percentage. The first material may also include an
Nb-base alloy that contains at least one secondary phase, such as
an Nb-containing intermetallic compound, an Nb-containing carbide,
or an Nb-containing boride. Such alloys are analogous to a
composite material in that they contain a ductile phase (i.e. the
Nb-base alloy) and a strengthening phase (i.e., an Nb-containing
intermetallic compound, an Nb-containing carbide, or an
Nb-containing boride).
[0022] Coating 150 extends along outer surface 112 of substrate
110. Coating 150 conforms to outer surface 112 and covers grooves
132 forming channels 130. Coating 150 includes one or more layers
50. In the illustrated embodiment, coating 150 is just the first
layer 50, or structural coating, that covers grooves 132. In
another embodiment, a single layer may be all that is used. In
alternative embodiments, however, hot gas path component 100 may
include additional layers 50, such as a bondcoat and a thermal
barrier coating (TBC). In one embodiment, coating 150 includes a
second material, which may be any suitable material, bonded to
outer surface 112 of substrate 110. For particular configurations,
coating 150 has a thickness in the range of 0.1 to 2.0 millimeters,
and more particularly, in the range of 0.1 to 1 millimeter, and
still more particularly 0.1 to 0.5 millimeters for industrial
components. For aviation components, coating 150 has a thickness in
the range of 0.1 to 0.25 millimeters. However, other thicknesses
may be utilized depending on the requirements for a particular hot
gas path component 100.
[0023] Coating 150 may be deposited using a variety of techniques.
In one embodiment, coating 150 is disposed over at least a portion
of outer surface 112 of substrate 110 by performing an ion plasma
deposition. Briefly, ion plasma deposition includes placing a
cathode formed of a coating material into a vacuum environment
within a vacuum chamber, providing substrate 110 within the vacuum
environment, supplying a current to the cathode to form a cathodic
arc upon a cathode surface resulting in erosion or evaporation of
coating material from the cathode surface, and depositing the
coating material from the cathode upon the substrate outer surface
112.
[0024] In one embodiment, the ion plasma deposition process
includes a plasma vapor deposition process. Non-limiting examples
of coating 150 include structural coatings, bond coatings,
oxidation-resistant coatings, and thermal barrier coatings. In some
embodiments, coating 150 includes nickel-based or cobalt-based
alloys, and more particularly includes a superalloy, or a NiCoCrAlY
alloy. For example, where the first material of substrate 110 is a
Ni-base superalloy containing both .gamma. and .gamma.' phases,
coating 150 may include these same materials.
[0025] In other embodiments, coating 150 is disposed over at least
a portion of outer surface 112 of substrate 110 by performing a
thermal spray process. For example, the thermal spray process may
include combustion spraying or plasma spraying, the combustion
spraying may include high velocity oxygen fuel spraying (HVOF) or
high velocity air fuel spraying (HVAF), and the plasma spraying may
include atmospheric (such as air or inert gas) plasma spray, or low
pressure plasma spray (LPPS), which is also known as vacuum plasma
spray or VPS). In one embodiment, a NiCrAlY coating is deposited by
HVOF or HVAF. In alternative embodiments, techniques for depositing
one or more layers of coating 150 include, without limitation,
sputtering, electron beam physical vapor deposition, electroless
plating, and electroplating.
[0026] In one embodiment, it is desirable to employ multiple
deposition techniques for forming coating 150. For example, with
reference to FIG. 3, first layer 54 may be deposited using an ion
plasma deposition, and second layer 56 and optional additional
layers (not shown) may be deposited using other techniques, such as
a combustion spray process (for example HVOF or HVAF) or using a
plasma spray process, such as LPPS. Depending on the materials
used, the use of different deposition techniques for the coating
layers 50 may provide benefits in strain tolerance and/or in
ductility.
[0027] More generally, the second material used to form coating 150
includes any suitable material that permits hot gas path component
100 to function as described herein. In one embodiment of hot gas
path component 100, the second material is capable of withstanding
temperatures of approximately 1150.degree. C., while the TBC can
withstand temperatures of approximately 1320.degree. C. Coating 150
is compatible with and adapted to be bonded to outer surface 112 of
substrate 110. This bond may be formed when coating 150 is
deposited onto substrate 110. Bonding may be influenced during the
deposition by many parameters, including the method of deposition,
the temperature of substrate 110 during the deposition, whether the
deposition surface is biased relative to the deposition source, and
other parameters. Bonding may also be affected by subsequent heat
treatment or other processing. In addition, the surface morphology,
chemistry, and cleanliness of substrate 110 prior to the deposition
can influence the degree to which metallurgical bonding occurs. In
addition to forming a strong metallurgical bond between coating 150
and substrate 110, it is desirable that this bond remain stable
over time and at high temperatures with respect to phase changes
and interdiffusion, as described herein. By compatible, it is
preferred that the bond between these elements be thermodynamically
stable such that the strength and ductility of the bond do not
deteriorate significantly over time (e.g., up to 3 years) by
interdiffusion or other processes, even for exposures at high
temperatures of approximately 1,150.degree. C. for a Ni-base alloy
substrate 110 and Ni-base coating 150, or higher temperatures of
approximately 1,300.degree. C. where higher temperature materials
are utilized, such as Nb-base alloys.
[0028] In one embodiment where the first material of substrate 110
is an Ni-base superalloy containing both .gamma. and .gamma.'
phases or a NiAl intermetallic alloy, second materials for coating
150 may include these same materials. Such a combination of coating
150 and substrate 110 materials is preferred for applications where
the maximum temperatures of the operating environment are below
1650.degree. C. In an embodiment where the first material of
substrate 110 is an Nb-base alloy, second materials for coating 150
may also include an Nb-base alloy, including the same Nb-base
alloy.
[0029] In some embodiments, such as applications that impose
temperature, environmental, or other constraints that make the use
of a metal alloy coating 150 undesirable, it is preferred that
coating 150 include materials that have properties that are
superior to those of metal alloys alone, such as composites in the
general form of intermetallic compound (I.sub.S)/metal alloy (M)
phase composites and intermetallic compound (I.sub.S)/intermetallic
compound (I.sub.M) phase composites. Metal alloy M may be the same
alloy as used for substrate 110, or a different material, depending
on the requirements of hot gas path component 100. These composites
are, in general, similar in that they combine a relatively more
ductile phase M or I.sub.M with a relatively less ductile phase
I.sub.s, in order to create coating 150 with the advantages of both
materials. Further, in order to have a successful composite, the
two materials must be compatible. As used herein in regard to
composites, the term "compatible" means that the materials must be
capable of forming the desired initial distribution of their phases
and maintaining that distribution for extended periods of time, as
described above, at temperatures of 1,150.degree. C. or greater
without undergoing metallurgical reactions that substantially
impair the strength, ductility, toughness, and other important
properties of the composite. Such compatibility can also be
expressed in terms of phase stability. That is, the separate phases
of the composite should be stable during operation at operating
temperature over extended periods so that the phases remain
separate and distinct, retaining their separate identities and
properties, and do not become a single phase or a plurality of
different phases due to interdiffusion. Compatibility can also be
expressed in terms of morphological stability of the interphase
boundary interface between the I.sub.S/M or I.sub.S/I.sub.M
composite layers. Such instability may be manifested by
convolutions that disrupt the continuity of either layer. It is
also noted that within a given coating 150, a plurality of
I.sub.S/M or I.sub.S/I.sub.M composites may also be used, and such
composites are not limited to two material or two phase
combinations. The use of such combinations is merely illustrative,
and not exhaustive or limiting of the potential combinations. Thus
M/I.sub.M/I.sub.S, M/I.sub.S1/I.sub.S2 (where I.sub.S1 and I.sub.S2
are different materials), and many other combinations are
possible.
[0030] In an embodiment where substrate 110 includes an Ni-base
superalloy comprising a mixture of both .gamma. and .gamma.'
phases, I.sub.S may include Ni.sub.3 [Ti, Ta, Nb, V], NiAl,
Cr.sub.3Si, [Cr, Mo].sub.xSi, [Ta, Ti, Nb, Hf, Zr, V]C,
Cr.sub.3C.sub.2, and Cr.sub.7C.sub.3 intermetallic compounds and
intermediate phases, and M may include an Ni-base superalloy
comprising a mixture of both .gamma. and .gamma.' phases. In
Ni-base superalloys comprising a mixture of both .gamma. and
.gamma.' phases, the elements Co, Cr, Al, C, and B are nearly
always present as alloying constituents, as well as varying
combinations of Ti, Ta, Nb, V, W, Mo, Re, Hf, and Zr. Thus, the
constituents of the exemplary I.sub.S materials described
correspond to one or more materials typically found in Ni-base
superalloys as may be used as the first material (to form substrate
110), and thus may be adapted to achieve the phase and
interdiffusional stability described herein. As an additional
example in the case where the first material (substrate 110)
includes NiAl intermetallic alloy, I.sub.s may include Ni.sub.3
[Ti, Ta, Nb, V], NiAl, Cr.sub.3Si, [Cr, Mo].sub.xSi, [Ta, Ti, Nb,
Hf, Zr, V]C, Cr.sub.3C.sub.2, and Cr.sub.7C.sub.3 intermetallic
compounds and intermediate phases and I.sub.M may include a
Ni.sub.3Al intermetallic alloy. Again, in NiAl intermetallic
alloys, one or more of the elements Co, Cr, C, and B are nearly
always present as alloying constituents, as well as varying
combinations of Ti, Ta, Nb, V, W, Mo, Re, Hf, and Zr. Thus, the
constituents of the exemplary I.sub.S materials described
correspond to one or more materials typically found in NiAl alloys
as may be used as the first material, and thus may be adapted to
achieve the phase and interdiffusional stability described
herein.
[0031] In an embodiment where substrate 110 includes an Nb-base
alloy, including an Nb-base alloy containing at least one secondary
phase, I.sub.S may include an Nb-containing intermetallic compound,
an Nb-containing carbide, or an Nb-containing boride, and M may
include an Nb-base alloy. It is preferred that such I.sub.S/M
composite includes an M phase of an Nb-base alloy containing Ti
such that the atomic ratio of the Ti to Nb (Ti/Nb) of the alloy is
in the range of 0.2-1, and an I.sub.S phase comprising a group
consisting of Nb-base silicides, Cr.sub.2 [Nb, Ti, Hf], and Nb-base
aluminides, and wherein Nb, among Nb, Ti and Hf, is the primary
constituent of Cr.sub.2 [Nb, Ti, Hf] on an atomic basis. These
compounds all have Nb as a common constituent, and thus may be
adapted to achieve the phase and interdiffusional stability.
[0032] In addition to coating system 150, the interior surface of
groove 132 (or of the micro-channel 130, if the first layer of
coating 150 is not particularly oxidation resistant) can be further
modified to improve its oxidation and/or hot corrosion resistance.
Suitable techniques for applying an oxidation-resistant coating
(not shown) to the interior surface of grooves 132 (or of
micro-channels 130) include vapor-phase or slurry chromiding,
vapor-phase or slurry aluminizing, or overlay deposition via
evaporation, sputtering, ion plasma deposition, thermal spray,
and/or cold spray. Example oxidation-resistant overlay coatings
include materials in the MCrAlY family (M={Ni, Co, Fe} and
Y={yttrium or another rare earth element}) as well as materials
selected from the NiAlX family (X={Cr, Hf, Zr, Y, La, Si, Pt,
Pd}).
[0033] FIG. 3 is a schematic cross-section of a portion of a
cooling circuit of the hot gas path component of FIG. 2 with
re-entrant cooling channels. As illustrated, base 134 of each
groove 132 is wider than top 136 forming a trapezoidal-shaped (or
re-entrant shaped) groove. To facilitate the deposition of coating
150 over groove 132 and the automatic removal of the filler during
the deposition process, it is desirable to have base 134 of groove
132 to be larger than top 136 of groove 132. This also permits the
formation of a sufficiently large micro-channel 130 to meet the
cooling requirements for hot gas path component 100. In some
embodiments, base 134 of a respective one of the re-entrant shaped
grooves 132 is at least 2 times wider than top 136 of the
respective groove 132. For example, if base 134 of groove 132 were
0.6 millimeters, top 136 would be less than 0.3 millimeters in
width. In alternative embodiments, base 134 of the respective
re-entrant shaped groove 132 is at least 3 times wider than top 136
of the respective groove 132, and more particularly, base 134 of
the respective re-entrant shaped groove 132 is in a range of
approximately 3-4 times wider than top 136 of the respective groove
132. Beneficially, a large base to top ratio increases the overall
cooling volume for micro-channel 130, while facilitating the
deposition of coating 150 over groove 132 and the automatic removal
of the filler during the deposition process.
[0034] Additionally, it is desirable to limit the depth of groove
132 in order to facilitate the automatic removal of the filler
during the deposition process, wherein the depth is defined as the
distance between the base of the groove and outer surface 112 of
substrate 110. By forming the re-entrant shaped grooves 132 with a
depth in the range of approximately 0.5 mm to approximately 1.27 mm
(0.020 inches to 0.050 inches), the filler can be automatically
removed during the coating application process, thereby eliminating
the difficult filler removal processing step for conventional
micro-channel forming techniques.
[0035] In addition, by forming re-entrant shaped grooves 132 with
narrow openings 136 (tops) in the range of approximately 0.127 mm
to approximately 0.4 mm (0.005 inches to 0.016 inches), openings
136 can be bridged by coating 150 and the filler can be
automatically removed during the coating application process,
thereby eliminating the difficult filler removal processing step
for conventional micro-channel forming techniques. In the
embodiment illustrated, coating 150 completely bridges grooves 132,
such that coating 150 seals micro-channels 130.
[0036] As discussed above, although micro-channels 130 are shown as
re-entrant shaped micro-channels, micro-channels 130 may have any
configuration, for example, they may be straight, curved, or have
multiple curves, etc. For the example, in one embodiment, the
grooves are rectangular shaped. Specifically, base 134 of each of
grooves 132 is substantially the same width as top 136 of groove
132. In some embodiments, openings 136 (tops) are in the range of
approximately 0.127 mm to approximately 0.4 mm (0.005 inches to
0.016 inches), whereby openings 136 can be bridged by coating 150.
In addition, the depth of grooves 132 may be in the range of
approximately 0.5 mm to approximately 1.27 mm (0.020 inches to
0.050 inches), whereby filler material 120 can be automatically
removed during the coating application process, thus eliminating
the difficult filler removal processing step for conventional
micro-channel forming techniques.
[0037] FIG. 4 is a schematic cross-section of a portion of hot gas
path component 100 of FIG. 2 with micro-channels 130 filled with a
filler material. In an exemplary embodiment, each groove 132 may be
filled with a filler material 120 that is automatically removed
during the application process of coating 150 to substrate 110. The
filler can be one of several materials that can withstand initial
exposure to the velocity and temperature conditions of coating 150
application processes described above. Filler material 120 is then
automatically removed as vapor during the complete coating process.
In an exemplary embodiment, filler material 120 is a silicone-based
polymer elastomer comprising methyl vinyl/di-methyl vinyl/vinyl
terminated siloxane (20%-30%), vinyl silicone fluid (20%-30%),
ground silica (15%-30%), silicon dioxide (15%-25%), and silanol
terminated polydimethylsiloxane (PDMS) (3%-9%), where the
percentages are in weight. An example of such a material is
MACHBLOC.TM., commercially available from Tapeworks of Bethlehem,
Pa. In another embodiment, the silicone-based polymer filler
material 120 may be HVMC.TM., commercially available from Green
Belting Industries, of Mississauga, Ontario, Canada. Filler
material 120 may be applied as putty-like filler that deforms
easily into any channel or hole, or can be formulated into a slurry
type consistency to be brushed into grooves 132.
[0038] The primary benefit of using filler material 120 described
above to fill grooves 132 is that filler material 120 is
automatically removed as vapor during the complete coating process.
A benefit beyond automatic removal is that the filler can withstand
the initial impact velocity and the temperature of coating 150,
whereby enough filler remains in grooves 132 to assure that no
coating 150 collects in grooves 132.
[0039] After application of filler material 120 to grooves 132,
outer surface 112 of substrate 110 may be cleaned and prepared for
coating, such as by machining, grit blasting, washing, and/or
polishing outer surface 112, including the portions of filler
material 120 that form or extend past outer surface 112. Once outer
surface 112 of substrate 110 is suitably cleaned and prepared, one
or more surface coatings may be applied to outer surface 112 over
filler material 120, as depicted in FIG. 3. As described above,
coating 150 may be any suitable material and is bonded to outer
surface 112 of substrate 110.
[0040] FIG. 5 is a schematic perspective view of the hot gas path
component of FIG. 2 showing three micro-channels that extend
partially along the surface of the substrate and channel cooling
fluid to respective film cooling holes. Substrate 110 and coating
150 may further define a plurality of exit film cooling holes 142.
Micro-channels 130 channel the cooling fluid from the respective
access hole 140 to the exiting film cooling hole 142. In one
embodiment, micro-channels 130 convey the cooling fluid to exiting
film cooling holes 142. Other embodiments, however, may not include
a film cooling hole 142, with micro-channels 130 extending along
outer surface 112 of substrate 110 and exiting off an edge of hot
gas path component 100, such as the trailing edge or the bucket
tip, or an endwall edge. In addition, it should be noted that
although film cooling holes 142 are shown in FIG. 5 as being round,
this is simply a non-limiting example. The film holes may be any
shaped hole that allows film cooling hole 142 to function as
described herein.
[0041] FIG. 6 is a schematic cross-section of one of the
micro-channels of FIG. 5 showing the micro-channel conveying
cooling fluid from an access hole to a film cooling hole. As
illustrated, micro-channel 130 conveys coolant from an access hole
140 to film cooling hole 142. Typically, micro-channel 130 length
is in the range of 10 to 1000 times film cooling hole 142 diameter,
and more particularly, in the range of 20 to 100 times film cooling
hole 142 diameter. Beneficially, micro-channels 130 can be used
anywhere on outer surface 112 of hot gas path component 100. In
addition, although micro-channels 130 are shown as having straight
walls, micro-channels 130 can have any configuration, for example,
they may be straight, curved, or have multiple curves, etc.
[0042] A method of manufacturing hot gas path component 100 is
described with reference to FIGS. 2-6. As discussed above with
reference to FIGS. 3 and 4, the method includes forming one or more
grooves 132 in outer surface 112 of substrate 110. For the
illustrated embodiments, multiple grooves 132 are formed in the
substrate outer surface 112. As indicated, for example, in FIG. 2,
substrate 110 has at least one hollow interior space 114. Substrate
110 is typically cast prior to forming grooves 132 in outer surface
112 of substrate 110, and example substrate materials are provided
above. As discussed above with reference to FIGS. 5 and 6, each of
grooves 132 extends at least partially along outer surface 112 of
substrate 110 and has a base 134.
[0043] As indicated in FIG. 4, for example, the fabrication method
further includes filling each of grooves 132 with filler material
120. Filler material 120 is a material that may withstand the
initial velocity and temperature of coating 150, yet is
automatically removed during the coating process.
[0044] As indicated in FIG. 3, for example, the fabrication method
further includes depositing coating 150 over at least a portion of
outer surface 112 of substrate 110 directly over grooves 132,
whereby filler material 120 is automatically removed during the
deposition process. Example coatings are provided above. In some
embodiments, coating 150 includes at least one of a structural
coating, a bond coating, an oxidation-resistant coating, and a
thermal barrier coating. Coating 150 completely bridges the
respective grooves 132, such that coating 150 seals the respective
micro-channels 130, as indicated in FIGS. 3 and 4, for example.
[0045] In the exemplary embodiment, as shown in FIGS. 3-5, groove
base 134 is wider than top 136 of the groove, such that each of
grooves 132 form trapezoidal-shaped, or re-entrant shaped groove
132. Re-entrant shaped grooves 132 may be formed using one or more
of abrasive liquid jet machining, plunge electrochemical machining
(ECM), electrical discharge machining (EDM) with a spinning
electrode (milling EDM), and laser machining (laser drilling).
Re-entrant shaped grooves 132 may be formed by directing an
abrasive liquid jet (not shown) at a lateral angle relative to
outer surface 112 of substrate 110 in a first pass of the abrasive
liquid jet, then making a subsequent pass at an angle substantially
opposite to that of the lateral angle and optionally performing an
additional pass where the abrasive liquid jet is directed toward
base 134 of groove 132 at one or more angles between the lateral
angle and the substantially opposite angle, such that material is
removed from base 134 of groove 132. In this manner, a relatively
narrow groove opening 136 (top of the groove) may be formed. Other
tool path configurations for the jet may also be used and include
any suitable tool path that permits grooves 132 to be formed as
described herein. In some embodiments, a multi-axis numerically
controlled (NC) tool path function may be employed to control the
pivot point for the jet, to ensure a narrow opening 136. The depth
of groove 132 in the exemplary embodiment ranges between
approximately 0.5 mm to approximately 1.27 mm (0.020 inches to
0.050 inches) and is determined by the sweeping speed, as well as
the jet travel speed along the groove when the jet pressure is
set.
[0046] Exemplary embodiments of the methods for forming cooling
channels are described above in detail. The methods are not limited
to the specific embodiments described herein, but rather, steps of
the methods may be utilized independently and separately from steps
described herein. For example, the methods described herein may
have other industrial or consumer applications and are not limited
to practice with turbine components as described herein. Rather,
one or more embodiments may be implemented and utilized in
connection with other industries.
[0047] Although specific features of various embodiments of the
invention may be shown in some drawings and not in others, this is
for convenience only. In accordance with the principles of the
invention, any feature of a drawing may be referenced and/or
claimed in combination with any feature of any other drawing.
[0048] As used herein, an element or step recited in the singular
and preceded with the word "a" or "an" should be understood as not
excluding plural said elements or steps, unless such exclusion is
explicitly stated. The terms "first," "second," and the like,
herein do not denote any order, quantity, or importance, but rather
are used to distinguish one element from another. The modifier
"approximately" used in connection with a quantity is inclusive of
the stated value, and has the meaning dictated by context, (e.g.,
includes the degree of error associated with measurement of the
particular quantity). In addition, the term "combination" is
inclusive of blends, mixtures, alloys, reaction products, and the
like. Furthermore, references to "one embodiment" are not intended
to be interpreted as excluding the existence of additional
embodiments that also incorporate the recited features. Moreover,
unless explicitly stated to the contrary, embodiments "comprising,"
"including," or "having" an element or a plurality of elements
having a particular property may include additional such elements
not having that property.
[0049] This written description uses examples to disclose the
invention, including the best mode, and to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
* * * * *