U.S. patent application number 14/290295 was filed with the patent office on 2015-12-03 for turbine bucket assembly and turbine system.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Stephen Joseph BALSONE, Dwight Eric DAVIDSON, Brian Denver POTTER.
Application Number | 20150345309 14/290295 |
Document ID | / |
Family ID | 54481589 |
Filed Date | 2015-12-03 |
United States Patent
Application |
20150345309 |
Kind Code |
A1 |
DAVIDSON; Dwight Eric ; et
al. |
December 3, 2015 |
TURBINE BUCKET ASSEMBLY AND TURBINE SYSTEM
Abstract
A turbine bucket assembly and turbine system are disclosed. The
assembly includes a single-lobe joint having an integral platform,
the joint having a first axial length; a segmented airfoil having a
root segment extending radially outward from the platform and a tip
segment coupled to the root segment, the tip segment having a
second axial length being less than the first axial length; and a
turbine wheel having a receptacle with a geometry corresponding to
the single-lobe joint and being coupled to the single-lobe joint.
The tip segment includes a tip segment material, the root segment
includes a root segment material, and the turbine wheel includes a
turbine wheel material having a lower heat resistance and a higher
thermal expansion than the root segment material and the tip
segment material.
Inventors: |
DAVIDSON; Dwight Eric;
(Greer, SC) ; POTTER; Brian Denver; (Greer,
SC) ; BALSONE; Stephen Joseph; (Simpsonville,
SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenetady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
54481589 |
Appl. No.: |
14/290295 |
Filed: |
May 29, 2014 |
Current U.S.
Class: |
60/805 ;
416/95 |
Current CPC
Class: |
F05D 2230/642 20130101;
F01D 5/3007 20130101; F01D 5/225 20130101; F01D 5/28 20130101; F01D
5/141 20130101; F01D 5/16 20130101 |
International
Class: |
F01D 5/28 20060101
F01D005/28; F01D 5/14 20060101 F01D005/14 |
Claims
1. A turbine bucket assembly, comprising: a single-lobe joint
having an integral platform, the joint having a first axial length;
a segmented airfoil having a root segment extending radially
outward from the integral platform and a tip segment coupled to the
root segment, the tip segment having a second axial length, the
second axial length being less than the first axial length; and a
turbine wheel having a receptacle with a geometry corresponding to
the single-lobe joint and being coupled to the single-lobe joint;
wherein the tip segment includes a tip segment material, the root
segment includes a root segment material, and the turbine wheel
includes a turbine wheel material, the turbine wheel material
having a lower heat resistance and a higher thermal expansion than
the root segment material and the tip segment material.
2. The assembly of claim 1, wherein the turbine wheel material is a
nickel-based superalloy, a cobalt-based superalloy, or a
steel-based superalloy.
3. The assembly of claim 1, wherein the root segment material is a
titanium aluminide.
4. The assembly of claim 1, wherein the tip segment material is a
titanium aluminide.
5. The assembly of claim 1, further comprising a tip shroud
integrally positioned on the tip segment of the segmented
airfoil.
6. The assembly of claim 5, wherein the tip shroud comprises a
sealing rail positioned on an outer surface of the tip shroud
distal from the single-lobe joint.
7. The assembly of claim 1, wherein the geometry of the turbine
wheel corresponding to the single-lobe joint defines a rim of the
turbine wheel.
8. The assembly of claim 1, wherein the single-lobe joint is
removably coupled to the turbine wheel by an axial joint, a
circumferential joint, a dovetail joint, a dado joint, a box joint,
a tongue-and-groove joint, or a combination thereof.
9. The assembly of claim 1, wherein the root segment is coupled to
the tip segment by an axial joint, a circumferential joint, a
curved dovetail joint, a dado joint, a box joint, a
tongue-and-groove joint, or a combination thereof.
10. The assembly of claim 1, further comprising a damper removably
coupled to the root segment.
11. The assembly of claim 1, further comprising an impact strip
positioned on a leading edge of the segmented airfoil.
12. The assembly of claim 1, further comprising an impact strip
positioned on a trailing edge of the segmented airfoil.
13. A turbine bucket assembly, comprising: a single-lobe joint
having an integral platform, the joint having a first axial length;
a segmented airfoil having a root segment extending radially
outward from the integral platform and a tip segment coupled to the
root segment, the tip segment having a second axial length, the
second axial length being less than the first axial length; and a
turbine wheel having a receptacle with a geometry corresponding to
the single-lobe joint and being coupled to the single-lobe joint;
wherein the tip segment includes a tip segment material, the root
segment includes a root segment material, and the turbine wheel
includes a turbine wheel material, the turbine wheel material being
a superalloy, the root segment material being a titanium aluminide,
and the tip segment material being a titanium aluminide.
14. A turbine system, comprising: a compressor section; a combustor
section configured to receive air from the compressor section; and
a turbine section in fluid communication with the combustor
section, the turbine section comprising a stator and a turbine
bucket assembly, the turbine bucket assembly comprising a
single-lobe joint having an integral platform, the joint having a
first axial length; a segmented airfoil having a root segment
extending radially outward from the integral platform and a tip
segment coupled to the root segment, the tip segment having a
second axial length, the second axial length being less than the
first axial length; and a turbine wheel having a receptacle with a
geometry corresponding to the single-lobe joint and being coupled
to the single-lobe joint; wherein the tip segment includes a tip
segment material, the root segment includes a root segment
material, and the turbine wheel includes a turbine wheel material,
the turbine wheel material having lower heat resistance and a
higher thermal expansion than the root segment material.
15. The turbine system of claim 14, further comprising a plurality
of axially spaced stages of turbine bucket assemblies including a
last stage of turbine bucket assemblies.
16. The turbine system of claim 15, wherein the airfoil has a
leading edge and a trailing edge, and further comprises at least
one impact strip attached to at least one of the leading edge, the
trailing edge, the tip segment, and the root segment.
17. The turbine system of claim 16, wherein impact strips are
attached to the leading edge of the tip segments of the plurality
of turbine bucket assemblies in one or more of the plurality of
turbine stages.
18. The turbine system of claim 16, wherein impact strips are
attached to the trailing edge of the tip segments of the plurality
of turbine bucket assemblies in one or more of the plurality of
turbine stages with the exception of the last stage.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to turbine components and
turbine systems. More particularly, the present invention is
directed to turbine bucket assemblies and turbine systems having
one or more turbine bucket assemblies.
BACKGROUND OF THE INVENTION
[0002] At least some known gas turbine engines include a combustor,
a compressor, and/or turbines that include a rotor disk that
includes a plurality of rotor blades, or buckets, that extend
radially outward therefrom. The plurality of rotating turbine
blades or buckets channel high-temperature fluids, such as
combustion gases or steam, through either a gas turbine engine or a
steam turbine engine. The roots of at least some known buckets are
coupled to the disk with dovetails that are inserted within
corresponding dovetail slots formed in the rotor disk to form a
bladed disk, or "blisk." Because such turbine engines operate at
relatively high temperatures and may be relatively large, the
operating capacity of such an engine may be at least partially
limited by the materials used in fabricating the buckets and/or the
length of the airfoil portions of the buckets. To facilitate
enhanced performance, at least some engine manufacturers have
increased the size of the engines, thus resulting in an increase in
the length of the airfoil portion of the buckets. Such an increase
can require the size of the dovetails and the dovetail slots to be
increased to ensure the longer buckets are retained in
position.
[0003] With or without repairable and/or replaceable airfoil tip
portions, turbine buckets assemblies are subjected to a variety of
forces. Such forces require different portions of the turbine
bucket assemblies to have different properties. It is known that
variation of density can provide benefit, depending upon the
position of the material. However, further characterization of
properties providing beneficial results, especially relating to
specific materials, would provide additional benefits.
[0004] A turbine bucket assembly and turbine system having a
turbine bucket assembly with improvements would be desirable in the
art.
BRIEF DESCRIPTION OF THE INVENTION
[0005] In an embodiment, a turbine bucket assembly includes a
single-lobe joint having an integral platform, the joint having a
first axial length; a segmented airfoil having a root segment
extending radially outward from the integral platform and a tip
segment coupled to the root segment, the tip segment having a
second axial length, the second axial length being less than the
first axial length; and a turbine wheel having a receptacle with a
geometry corresponding to the single-lobe joint and being coupled
to the single-lobe joint. The tip segment includes a tip segment
material, the root segment includes a root segment material, and
the turbine wheel includes a turbine wheel material, the turbine
wheel material having lower heat resistance and a higher thermal
expansion than the root segment material and the tip segment
material.
[0006] In another embodiment, a turbine bucket assembly includes a
single-lobe joint having an integral platform, the joint having a
first axial length; a segmented airfoil having a root segment
extending radially outward from the integral platform and a tip
segment coupled to the root segment, the tip segment having a
second axial length, the second axial length being less than the
first axial length; and a turbine wheel having a receptacle with a
geometry corresponding to the single-lobe joint and being coupled
to the single-lobe joint. The tip segment includes a tip segment
material, the root segment includes a root segment material, and
the turbine wheel includes a turbine wheel material, the turbine
wheel material being a superalloy, the root segment material being
a titanium aluminide, and the tip segment material being a titanium
aluminide.
[0007] In another embodiment, a turbine system includes a
compressor section, a combustor section configured to receive air
from the compressor section, and a turbine section in fluid
communication with the combustor section, the turbine section
comprising a stator and a turbine bucket assembly. The turbine
bucket assembly includes a single-lobe joint having an integral
platform, the joint having a first axial length; a segmented
airfoil having a root segment extending radially outward from the
integral platform and a tip segment coupled to the root segment,
the tip segment having a second axial length, the second axial
length being less than the first axial length; and a turbine wheel
having a receptacle with a geometry corresponding to the
single-lobe joint and being coupled to the single-lobe joint. The
tip segment includes a tip segment material, the root segment
includes a root segment material, and the turbine wheel includes a
turbine wheel material, the turbine wheel material having lower
heat resistance and a higher thermal expansion than the root
segment material and the tip segment material.
[0008] Other features and advantages of the present invention will
be apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view of a turbine system having a
turbine bucket assembly, according to an embodiment of the
disclosure.
[0010] FIG. 2 is a perspective view of a turbine bucket assembly
having a segmented airfoil in a turbine bucket, according to an
embodiment of the disclosure.
[0011] FIG. 3 is a right-side plan view of a latter stage turbine
bucket (for example, a bucket for use in a third or fourth stage of
a four-stage turbine), according to an embodiment of the
disclosure.
[0012] Wherever possible, the same reference numbers will be used
throughout the drawings to represent the same parts.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Provided is a turbine bucket assembly and a turbine system.
In addition, methods of assembling and/or producing such turbine
bucket assemblies and turbine systems are apparent from the
disclosure. Embodiments of the present disclosure, for example, in
comparison to similar concepts failing to include one or more of
the features disclosed herein, permit easier repair of damage (for
example, by a tip-rub event, overheating, and/or any other damaging
event) by permitting the tip segment to be repaired alone without
requiring more expensive and more time-consuming removal and
repair/replacement of the complete turbine bucket, reduce overall
operating and maintenance costs, reduce duration of out-of-service
periods for repairs, permit other suitable advantages, permit
larger or smaller sized engines and/or turbine buckets to be used,
permit portions of a turbine bucket assembly to be exposed to
higher temperatures, permit properties in a specific portion of a
turbine bucket assembly to be resistant to additional forces,
permit use of additional materials for portions of turbine bucket
assemblies, or a combination thereof
[0014] FIG. 1 is a schematic view of a turbine system 10, such as,
a gas turbine engine system, a power generation system, any other
suitable system utilizing blades/buckets, or a combination thereof.
As used herein, the term "blade" is used interchangeably with the
term "bucket." A suitable turbine bucket is shown in FIG. 3, which
illustrates a bucket fur use in a latter stage of a gas turbine
(for example, a third or fourth stage of a four-stage turbine). In
one embodiment, the system 10 includes an intake section 12, a
compressor section 14 downstream from the intake section 12, a
combustor section 16 coupled downstream from the intake section 12,
a turbine section 18 coupled downstream from the combustor section
16, and an exhaust section 20. The turbine section 18 is drivingly
coupled to the compressor section 14 via a rotor shaft 22. The
combustor section 16 includes a plurality of combustors 24 and is
coupled to the compressor section 14 such that each of the
combustors 24 is in fluid communication with the compressor section
14. A fuel nozzle assembly 26 is coupled to each of the combustors
24. The turbine section 18 is rotatably coupled to the compressor
section 14 and to a load 28, such as, but not limited to, an
electrical generator and/or a mechanical drive application. The
compressor section 14 and/or the turbine section 18 include at
least one blade or turbine bucket 30 coupled to the rotor shaft
22.
[0015] During operation, the intake section 12 channels air towards
the compressor section 14. The compressor section 14 compresses the
inlet air to higher pressures and temperatures and discharges the
compressed air towards the combustor section 16. The compressed air
is mixed with fuel and ignited to generate combustion gases that
flow to the turbine section 18, which drives the compressor section
14 and/or the load 28. Specifically, at least a portion of the
compressed air is supplied to fuel nozzle assembly 26. Fuel is
channeled to the fuel nozzle assembly 26. The fuel is mixed with
the air and ignited downstream of fuel nozzle assembly 26 in the
combustor section 16. Combustion gases are generated and channeled
to the turbine section 18. Gas stream thermal energy is converted
to mechanical rotational energy in the turbine section 18. Exhaust
gases exit the turbine section 18 and flow through the exhaust
section 20 to the ambient atmosphere.
[0016] FIG. 2 is a perspective view of a turbine bucket assembly
200 having the turbine bucket 30 capable of use with the system 10.
The turbine bucket 30 has an airfoil 110. The airfoil 110 is
segmented (for example, having a tip segment 122 and a root segment
124, which are formed separately or are separable at a segment
joint 130). The turbine bucket 30 includes a pressure side 102 and
a suction side 103 connected together at a leading edge 104 and a
trailing edge 106. The pressure side 102 includes a generally
concave geometry, and the suction side 103 includes a generally
convex geometry. The turbine bucket 30 includes a joint 108, and/or
any other suitable features, such as a platform 112 extending
between the joint 108 and the airfoil 110.
[0017] The joint 108 is a dovetail, is multi-lobed, is
single-lobed, is a portion of a blisk, is integral with the airfoil
110 (for example, such that there are no seams or inconsistencies
in the turbine bucket 30 where the platform 112 transitions to the
airfoil 110), is another suitable mechanism or device for securing
the turbine bucket 30, or is a combination thereof. The
coefficients of thermal expansion of the materials in the
components (for example, a wheel 105, the root segment 124, and the
tip segment 122) dictate the joint type between the respective
components. For instance, when the materials have a nearly
identical or identical coefficient of thermal expansion over a wide
range of temperatures, the joint 108 between the components is
capable of being either a single-lobe or a multi-lobe joint. A
multi-lobe joint may be preferred in some circumstances. In
contrast, when the materials have dissimilar coefficients of
thermal expansion, a single-lobe joint between the components may
be preferred.
[0018] In one embodiment, the turbine bucket 30 couples to the
wheel 105 via the joint 108 and extends radially outward from the
wheel 105. The joint 108 has a single-lobe geometry corresponding
to a respective receptacle in the wheel 105 and is capable of being
removably or permanently coupled to the wheel 105 by any suitable
technique. One suitable technique includes the joint 108 being
removably coupled to the wheel 105 by an axial joint or a
circumferential joint. Another suitable technique includes the
joint 108 being removably coupled to the wheel 105 by a dovetail
joint, a dado joint, a box joint, a tongue-and-groove joint, or a
combination thereof
[0019] In one embodiment, the wheel 105 is a turbine wheel having a
plurality of receptacles with geometry corresponding to the
single-lobe joints 108 of a corresponding plurality of turbine
buckets 30, and the geometry of the wheel 105 defines a rim of the
turbine wheel. In an alternate embodiment (FIG. 1), the turbine
buckets 30 couple, via the joints 108, directly to the rotor shaft
22 and extend radially outward from the rotor shaft 22.
[0020] In one embodiment, the joint 108 has an axial joint length
114 that facilitates securing. In one embodiment, the platform 112
extends radially outward from the joint 108 and has a platform
length 117 that is equal to or approximately equal to the axial
joint length 114 (as shown in FIGS. 2 and 3).
[0021] In one embodiment, the airfoil 110 extends radially outward
from the joint 108, extends radially outward from an outer platform
surface of the platform 112, has an initial airfoil length 119 that
is approximately equal to the axial joint length 114, and/or
decreases in axial length to a tip end length 118 at a tip end 116
of the turbine bucket 30, such that the tip end length 118 is
shorter than the axial joint length 114, when viewed from the
right-side profile, as shown in FIG. 3. The tip end length 118 and
a tip width are capable of being varied, depending on the
application of turbine bucket 30 and/or the system 10. The airfoil
110 has a first or radial length 120 measured from platform 112 to
tip end 116, for example, to permit increased performance of the
turbine bucket 30. The airfoil length 120 is capable of being
varied, depending on the application of the turbine bucket 30 or
the system 10. In one embodiment, the airfoil 110 has an airfoil
width sized to facilitate locking to the wheel 105.
[0022] The airfoil 110 is a segmented portion of the turbine bucket
30. In one embodiment, as shown in FIG. 2, the airfoil 110 includes
a first or the tip segment 122 coupled (removably or permanently)
to a second or the root segment 124. The root segment 124 is
proximal to the wheel 105 or the rotor shaft 22 (see FIG. 1). The
tip segment 122 is distal from the wheel 105 or the rotor shaft 22
(see FIG. 1), for example, proximal to a tip shroud 109 or a
sealing rail 111. In one embodiment, the tip segment 122 is coupled
to the root segment 124 at the segment joint 130, which is a
multi-lobe segment joint, for example, an axial segment joint, a
circumferential segment joint, a curved dovetail segment joint, a
dado segment joint, a box segment joint, a tongue-and-groove
segment joint, or a combination thereof. In another embodiment, the
tip segment 122 is coupled to the root segment 124 at the segment
joint 130, which is a single-lobe segment joint, for example, an
axial segment joint, a circumferential segment joint, a curved
dovetail segment joint, a dado segment joint, a box segment joint,
a tongue-and-groove segment joint, or a combination thereof. As
used herein, the term "axial segment joint" is used to describe a
segment joint that is formed along an axial length of a
cross-section of the airfoil 110. As used herein, the term
"circumferential joint" is used to describe a segment joint that is
formed along the circumferential width of the airfoil 110.
[0023] The tip segment 122 includes a tip segment length 126 that
is comparable to the turbine bucket length 120, for example, by
having a relative ratio to the turbine bucket length 120, such as,
about 25 percent, about 40 percent, greater than 40 percent, less
than about 50 percent, about 50 percent, greater than about 50
percent, about 60 percent, between about 40 percent and about 60
percent, about 75 percent, between about 25 percent and about 75
percent, between about 40 percent and about 75 percent, or any
suitable combination, sub-combination, range, or sub-range therein.
The tip segment length 126 extends to a mid-region of the airfoil
110 having an axial length 129, which is greater than the tip end
length 118 and less than the initial airfoil length 119, when
viewed from the right-side profile as shown in FIG. 3.
[0024] In one embodiment, the airfoil 110 includes at least one
mid-shroud damper 128 coupled to the root segment 124, for example,
to dampen vibrations in the airfoil 110 and/or to provide
structural support to the airfoil 110 during operation of the
system 10. In one embodiment, the mid-shroud damper 128 works
cooperatively with damping pins (not shown) located between the
root segment 124 and the tip segment 122, for example, to
selectively prevent the tip segment 122 from uncoupling from the
root segment 124. Additionally or alternatively, damping pins (not
shown) may be used between the joint 108 and the receptacle of the
wheel 105 to secure the bucket 30 to the wheel 105.
[0025] In one embodiment, the turbine bucket 30 includes the tip
shroud 109 integrally positioned on the tip segment 122. The tip
shroud 109 includes features for protecting the tip segment 122,
such as one or more sealing rails 111 positioned on an outer
surface 113 of the tip segment 122 distal from the joint 108. In
one embodiment, the tip shroud 109 includes a base covering the
cross-sectional area of the tip segment 122.
[0026] The tip segment 122, the root segment 124, the joint 108,
and/or the wheel 105 include any suitable combination of materials
capable of withstanding the operational demands of the system 10
and/or operating in conjunction with the features of the turbine
bucket 30. The materials are similar materials, the same materials,
or different materials, which are chosen to achieve a balance
between considerations of weight and cost and performance at higher
temperatures and/or speeds.
[0027] Suitable materials for the tip segment 122 include, but are
not limited to, ceramic matrix composite materials, titanium
aluminide, materials having a similar or lower thermal expansion
than materials in the root segment 124 and/or the wheel 105,
materials having similar or higher heat resistance than materials
in the root segment 124 and/or the wheel 105 (for example, to
accommodate the tip segment 122 being exposed to higher operating
temperatures), materials having a similar or lower density than
materials in the root segment 124 and/or the wheel 105 (for
example, resulting in a lower rotating mass in the turbine bucket
30), or a combination thereof. In one exemplary embodiment
described herein, the tip segment 122 includes a titanium aluminide
material.
[0028] The root segment 124, the platform 112, and the joint 108
are formed integrally with one another and, as such, are
manufactured from the same material. Suitable materials for the
root segment 124 include, but are not limited to, superalloys,
titanium aluminide, materials having a similar or higher thermal
expansion than materials in the tip segment 122, materials having
similar or lower heat resistance than materials in the tip segment
122, materials having a similar or lower thermal expansion than
materials in the wheel 105, materials having a similar or higher
heat resistance than materials in the wheel 105 (for example, to
accommodate the tip segment 122 being exposed to higher operating
temperatures), materials having a similar or lower density than
materials in the wheel 105 (for example, resulting in a lower
rotating mass in the turbine bucket 30), or a combination thereof.
In an exemplary embodiment described herein, the root segment 122
includes a titanium aluminide material, which is the same or
different from the titanium aluminide material used in the tip
segment 122.
[0029] Suitable materials for the wheel 105 include, but are not
limited to, cobalt-based superalloys, nickel-based superalloys,
steel-based superalloys, materials having a similar or higher
thermal expansion than materials in the root segment 124 and/or the
tip segment 122, materials having similar or lower heat resistance
than materials in the root segment 124 and/or the tip segment 122,
materials having a similar or higher density than materials in the
root segment 124 and/or the tip segment 122, or a combination
thereof. In an exemplary embodiment described herein, the wheel 105
includes a superalloy having the properties discussed above.
[0030] As used herein, the term "ceramic matrix composite"
includes, but is not limited to, carbon-fiber-reinforced carbon
(C/C), carbon-fiber-reinforced silicon carbide (C/SiC), and
silicon-carbide-fiber-reinforced silicon carbide (SiC/SiC). In one
embodiment, the ceramic matrix composite material has increased
elongation, fracture toughness, thermal shock, dynamical load
capability, and anisotropic properties as compared to a monolithic
ceramic structure.
[0031] As used herein, the term "titanium aluminide" includes, but
is not limited to, typical compositions, by weight, of about 45% Ti
and about 50% Al (TiAl) and/or a molar ratio of about 1 mole Ti to
about 1 mole Al, TiAl.sub.2 (for example, at a molar ratio of about
1 mole Ti to about 2 moles Al), TiAl.sub.3 (for example, at a molar
ratio of about 1 mole Ti to about 3 moles Al), Ti.sub.3Al (for
example, at a molar ratio of about 3 moles Ti to about 1 mole Al),
or other suitable mixtures thereof
[0032] As used herein, the term "superalloy" includes, but is not
limited to, nickel-based alloys, cobalt-based alloys, or
steel-based alloys. One typical nickel-based superalloy material,
which is sold under the tradename INCONEL.RTM. 718 by Special Metal
Corporation of New Hartford, N.Y., has a composition, by weight, of
about 50.0-55.0% Ni, about 17.0-21.0% Cr, about 4.75-5% Nb, about
2.8-3.3% Mo, about 1.0% Co, about 0.65-1.15% Al, about 0.35% Mn,
about 0.35% Si, about 0.2-0.8% Cu, about 0.3% Ti, about 0.08% C,
about 0.015% S, about 0.015% P, and about 0.006% B, and a balance
of Fe. An exemplary CrMoV (steel-based) superalloy composition has
a composition, by weight %, of about 0.90-1.50% Mo, about
0.90-1.25% Cr, about 0.55-0.90% Mn, about 0.35-0.55% Ni, about
0.25-0.33% C, 0.20-0.30% V, no more than about 0.35% Si, no more
than about 0.35% Cu, no more than 0.012% P, no more than about
0.012% S, and the balance Fe and trace impurities.
[0033] Referring again to FIG. 2, in one embodiment, the turbine
bucket 30 includes impact strips 107 on the airfoil 110, which
increase impact toughness of the component to which they are
attached. The impact strips 107 are capable of being produced from
a similar or different material from at least a portion of the
airfoil 110 and/or are capable of possessing similar or different
properties from at least a portion of the airfoil 110. The impact
strips 107 are positioned on the leading edge 104 of the turbine
bucket 30 (as shown), the trailing edge 106 of the turbine bucket
30, on the tip segment 122, the root segment 124, or a combination
thereof. In one embodiment, the impact strips 107 on the leading
edge 104 of the tip segments 122 are on any and/or all turbine
stages, whereas the impact strips 107 on the trailing edge 106 of
the tip segments 122 are on any and/or all turbine stages except
the last stage.
[0034] The impact strips 107 are attached by one or more chemical
and/or mechanical techniques, for example, based upon physics-based
methods (such as, geometry) and material science methods (such as,
alloying). In one embodiment, the impact strips 107 are chemically
attached, for example, via in-situ material processing, such as,
cast-in, in-situ extrusion, in-situ forging, other suitable
techniques, or a combination thereof. Additionally or
alternatively, in one embodiment, the impact strips 107 are
chemically attached via post-material initial processing, such as,
diffusion bonding, alloy brazing, welding, other suitable
techniques, or a combination thereof. In another embodiment, the
impact strips 107 are mechanically attached via glue, rivets, stem
pins, buttons, or retention joints (for example, a dado joint, a
box joint, and/or a tongue-and-groove joint), other suitable
techniques, or a combination thereof.
[0035] While the invention has been described with reference to one
or more embodiments, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended claims. In
addition, all numerical values identified in the detailed
description shall be interpreted as though the precise and
approximate values are both expressly identified.
* * * * *