U.S. patent application number 12/421922 was filed with the patent office on 2010-10-14 for cold spray method of applying aluminum seal strips.
This patent application is currently assigned to General Electronic Company. Invention is credited to Mark L. Hunt, Warren Martin Miglietti, Anthony W. Reynolds, Michael Howard Rucker, John E. Wladkowski.
Application Number | 20100260932 12/421922 |
Document ID | / |
Family ID | 42934603 |
Filed Date | 2010-10-14 |
United States Patent
Application |
20100260932 |
Kind Code |
A1 |
Hunt; Mark L. ; et
al. |
October 14, 2010 |
COLD SPRAY METHOD OF APPLYING ALUMINUM SEAL STRIPS
Abstract
A method for applying a seal strip to a surface of a turbine
component by accelerating solid particles to a velocity sufficient
to cause the solid particles to plastically deform and bond to the
surface and each other when impacted on the surface, and impacting
the solid particles on the surface so as to cause the solid
particles to deform and bond to the surface and each other to form
the seal strip on the surface.
Inventors: |
Hunt; Mark L.;
(Simpsonville, SC) ; Rucker; Michael Howard;
(Cincinnati, OH) ; Reynolds; Anthony W.;
(Burlington, KY) ; Miglietti; Warren Martin;
(Greenville, SC) ; Wladkowski; John E.; (Lynn,
MA) |
Correspondence
Address: |
SUTHERLAND ASBILL & BRENNAN LLP
999 PEACHTREE STREET, N.E.
ATLANTA
GA
30309
US
|
Assignee: |
General Electronic Company
Schenectady
NY
|
Family ID: |
42934603 |
Appl. No.: |
12/421922 |
Filed: |
April 10, 2009 |
Current U.S.
Class: |
427/192 ;
427/191 |
Current CPC
Class: |
C23C 24/04 20130101 |
Class at
Publication: |
427/192 ;
427/191 |
International
Class: |
C23C 24/02 20060101
C23C024/02 |
Claims
1. A method for applying a seal strip to a component comprising:
providing the component having a surface; accelerating solid
particles to a velocity sufficient to cause the solid particles to
plastically deform and bond to the surface and each other when
impacted on the surface; and impacting the solid particles on the
surface so as to cause the solid particles to deform and bond to
the surface and each other to form the seal strip on the
surface.
2. The method of claim 1, wherein the solid particles comprise
aluminum.
3. The method of claim 1, wherein the solid particles comprise a
powdered metal.
4. The method of claim 1, wherein the component comprises a turbine
bucket having a dovetail, and the surface is located on the
dovetail.
5. The method of claim 1, wherein accelerating the solid particles
uses a high-pressure gas.
6. The method of claim 5, wherein the high-pressure gas comprises
helium.
7. The method of claim 5, wherein the high-pressure gas comprises
air.
8. The method of claim 1, wherein the velocity is greater than
about 350 m/sec.
9. The method of claim 1, further comprising dispersing the solid
particles in a carrier gas before accelerating the solid
particles.
10. A method for applying a seal strip to a component comprising:
providing the component having a surface; providing a spray coating
apparatus comprising a deposition nozzle; a powder fluidizing unit;
and a pressurized gas source; wherein the powder fluidizing unit is
configured to disperse solid particles into a carrier gas and the
pressurized gas source provides sufficient pressure to accelerate
the solid particles dispersed in the carrier gas through the
deposition nozzle at a velocity sufficient to cause the solid
particles to plastically deform and bond to the surface and each
other when impacted on the surface; accelerating the solid
particles through the deposition nozzle; and impacting the solid
particles on the surface so as to cause the solid particles to
deform and bond to the surface and each other to form the seal
strip on the surface.
11. The method of claim 10, wherein the solid particles comprise
aluminum.
12. The method of claim 10, wherein the solid particles comprise a
powdered metal.
13. The method of claim 10, wherein the component comprises a
turbine bucket having a dovetail, and the surface is located on the
dovetail.
14. The method of claim 10, wherein the solid particles are
accelerated using a high-pressure gas.
15. The method of claim 14, wherein the high-pressure gas comprises
helium.
16. The method of claim 14, wherein the high-pressure gas comprises
air.
17. The method of claim 10, wherein the velocity is greater than
about 350 m/sec.
18. The method of claim 10, wherein the deposition nozzle is
attached to a robotic arm.
19. The method of claim 10, wherein the surface of the component is
unmasked.
20. The method of claim 18, wherein the robotic arm is
automatically controlled to deposit the seal strip on the surface
of the component.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] This invention is generally in the field of gas turbine
power generation systems. More particularly, the present invention
is directed to a method of efficiently producing high quality seal
strips on turbine components, such as on bucket dovetails.
[0004] Aluminum seal strips are commonly applied to turbine
components, such as bucket dovetails, to prevent fluids from
passing between joined components. FIG. 1 illustrates a typical
application of the aluminum seal strips 14 to a dovetail 12 of a
turbine bucket 10. The aluminum seal strips 14 generally prevent
cooling air from leaking past the dovetail 12 when the turbine
bucket 10 is attached to the turbine wheel. It should be noted that
the precise configurations and locations where the aluminum seal
strips 14 are applied to a component may vary from one component to
another. For example, turbine buckets attached to a turbine wheel
close to the combustors will typically have different geometries
than turbine buckets attached to the turbine wheel further
downstream from the combustors.
[0005] Aluminum seal strips 14 are typically applied to turbine
components by an arc-wire spray coating process. When performing an
arc-wire spray coating process, a pair of electrically conductive
wires are melted by an electric current in or adjacent to a spray
nozzle. Air is simultaneously fed through the spray nozzle to
atomize the molten material and deposit the material on a substrate
surface. The molten particles rapidly solidify to form a coating
when the particles strike the substrate surface.
[0006] Before the aluminum seal strips 14 are applied to the
surfaces of dovetail 12 by an arc-wire spray coating processes, the
turbine bucket 10 must first be prepared to receive the spray
coating. The preparation of the surface is typically a multi-step
process involving (1) a cleaning step, (2) a taping or "masking"
step, and (3) a grit blasting step. During the taping step, all
surfaces which are not to be coated by aluminum must be covered
with masking. Because turbine buckets often have a complex geometry
which varies from one bucket to another depending upon where along
the turbine wheel the bucket is designed to attach, masking must
often be customized for each bucket and applied carefully by hand.
After the surface is prepared, the coating is sprayed onto the
substrate surface and the masking is removed.
[0007] Such a seal strip application process often requires a
significant amount of man hours and cost to the turbine
manufacturer. Furthermore, the spray-coated seal strips are often
applied in a non-uniform manner due to the imprecise spray pattern
produced by the arc-wire spray nozzle. As such, it would be
desirable to provide a more time and cost efficient method of
applying high-quality aluminum seal strips to turbine
components.
BRIEF SUMMARY OF THE INVENTION
[0008] In one aspect, the present invention comprises a method for
applying a seal strip to a surface of a component by accelerating
solid particles to a velocity sufficient to cause the solid
particles to plastically deform and bond to the surface and each
other when impacted on the surface, and impacting the solid
particles on the surface so as to cause the solid particles to
deform and bond to the surface and each other to form the seal
strip on the surface.
[0009] In another aspect, the present invention comprises a method
for applying a seal strip to a surface of a component utilizing a
spray coating apparatus having a deposition nozzle, a powder
fluidizing unit, and a pressurized gas source. The powder
fluidizing unit is configured to disperse solid particles into a
carrier gas and the pressurized gas source provides sufficient
pressure to accelerate the solid particles dispersed in the carrier
gas through the deposition nozzle at a velocity sufficient to cause
the solid particles to plastically deform and bond to the surface
and each other when impacted on the surface. The method further
comprises accelerating the solid particles through the deposition
nozzle, and impacting the solid particles on the surface so as to
cause the solid particles to deform and bond to the surface and
each other to form the seal strip on the surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view, illustrating a turbine
component with aluminum seal strips.
[0011] FIG. 2A is a section view, illustrating a seal strip
produced by an arc-wire spray coating process.
[0012] FIG. 2B is a section view, illustrating a seal strip
produced by kinetic metallization.
[0013] FIG. 3 is a schematic, illustrating an apparatus for
performing methods of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The present invention comprises methods of efficiently
producing high-quality seal strips on turbine components. In some
embodiments, as illustrated in FIG. 1, the seal strips 14 comprise
aluminum and are applied to surfaces of the dovetail 12 of a
turbine bucket 10. The precise location and configuration of the
seal strips 14 may vary from one bucket to another, depending upon
where on the turbine wheel the bucket is to be installed.
[0015] In one aspect, the present invention comprises a method for
applying the seal strip 14 to the surface by accelerating solid
particles to a velocity sufficient to cause the solid particles to
plastically deform and bond to the surface and each other when
impacted on the surface, and impacting the solid particles on the
surface so as to cause the solid particles to deform and bond to
the surface and each other to form the seal strip 14 on the
surface. This deformation and bonding process, which is an entirely
solid-state process, may be referred to as "kinetic metallization".
When undergoing kinetic metallization, the solid particles
experience a very large strain upon collision with the surface
which causes the particles to flatten, increasing each particle's
surface area. Other particles collide and flatten against the
previously flattened and deposited particles and metallurgical
bonds are formed between the particles and the surface.
[0016] In some embodiments, the solid particles comprise a metal
powder, such as powdered aluminum. The particles may be accelerated
to speeds greater than about 350 m/sec and impacted upon the
surface to deposit the aluminum as a strip on the surface. The
solid particles may be accelerated using a high-pressure gas, such
as pressurized helium or air.
[0017] It has been discovered that seal strips produced by kinetic
metallization have superior properties to seal strips produced by
arc-wire spray processes. It has further been discovered that
kinetically-metallized seal strips may be applied more efficiently
and without surface preparation steps typically required for
applying seal strips by arc-wire spray processes.
[0018] FIGS. 2A and 2B are illustrative of seal strips produced by
an arc-wire coating process and a kinetic metallization process,
respectively. As illustrated in FIG. 2A, an arc-wire coated strip
18 possesses a non-uniform and irregular coating pattern. The depth
of the coating, measured from the exterior surface of the coating
to the surface of the substrate 16, varies unpredictably across the
width of the strip 18. Also, pockets of entrained air are prolific
throughout the coating. These qualities result from air being mixed
with the molten material while the material solidifies.
[0019] As illustrated in FIG. 2B, the kinetically-metallized strip
20 possesses a more uniform and regular coating pattern compared to
the arc-wire coated strip 18 of FIG. 2A. The coating depth is
predictable across the width of the strip 18. Also, pockets of
entrained air are only sparsely present throughout the coating. It
has been discovered that such a coating pattern produced a superior
seal between turbine components.
[0020] In another aspect, as illustrated in FIG. 3, the present
invention comprises a method for applying a seal strip utilizing a
spray coating apparatus 34 having a deposition nozzle 30, a powder
fluidizing unit 26, and a pressurized gas source 22. The powder
fluidizing unit 26 is configured to disperse solid particles into a
carrier gas 32. The pressurized gas source 22 provides sufficient
pressure to accelerate the solid particles dispersed in the carrier
gas 32 through the deposition nozzle 30 at a velocity sufficient to
cause the solid particles to plastically deform and bond to the
surface and each other when impacted on the surface. The solid
particles may be fed to the powder fluidizing unit 26 from a hopper
24. The carrier gas 32 may be supplied from the pressurized gas
source 22 or a different source. The apparatus 34 may further
include a thermal conditioning unit 28 the gas to the desired
operating temperature.
[0021] The method further comprises accelerating the solid
particles through the deposition nozzle 30, and impacting the solid
particles on the surface so as to cause the solid particles to
deform and bond to the surface and each other to form the seal
strip on the surface.
[0022] The apparatus 34 is capable of depositing solid particles on
a turbine component surface to form a coating substantially as
illustrated in FIG. 2B. Further, the deposition nozzle 30 may be
configured to deposit a coating of a predefined width with
excellent edge control (i.e., the coating produced using the
deposition nozzle 30 may have a well-defined edge). Such a feature
allows apparatus 34 to be used to apply a kinetically-metallized
seal strip 14 to a turbine component without requiring additional
preparation steps, including taping the turbine component with
protective masking. Further, the steps of surface cleaning and grit
blasting the surface of the turbine component may be omitted since
the solid particles may be bonded to an unprepped surface by
kinetic metallization.
[0023] It should be appreciated that the deposition nozzle 30 may
be integrated to a robotic arm to allow a fully-automatic coating
process to be performed. The robotic arm may be controlled by a
programmable controller which controls actuators or servomechanisms
on the robotic arm to direct specific coating configurations at
defined locations on the surface of the turbine component. For
example, the robotic arm may be controlled by any controller
adapted for use with CNC machining. It should be appreciated that
coating depth, width, and length may be controlled by actuation of
the robotic arm. For example, the robotic arm may articulate slowly
to deposit a thick coating or quickly to deposit a thin coating.
Also, the deposition nozzle 30 may be placed in close proximity to
the surface of the turbine component to deposit a strip having a
narrow width or may be placed at a greater distance from the
surface to deposit a strip having a wide width. Furthermore,
different control sequences may be used for each turbine component
to allow unique seal strip configurations to be applied to various
components. For example, different control sequences may be used
for each turbine bucket to deposit the seal strip in the preferred
locations with the preferred configuration.
[0024] The foregoing robotic system may be designed to operate with
commercially available cold-spray devices. For example, a
cold-spray device from Supersonic Spray Technologies, a division of
CenterLine Ltd. (Detroit, Mich.) may be integrated with a CNC
controlled robotic arm and equipped with an appropriate deposition
nozzle 30 to carry out the foregoing method. The preferred design
of the deposition nozzle 30 is a function of the operating pressure
of the cold-spray device as well as the desired spray pattern.
[0025] The invention is not limited to the specific embodiments
disclosed above. Modifications and variations of the methods and
devices described herein will be obvious to those skilled in the
art from the foregoing detailed description. Such modifications and
variations are intended to come within the scope of the appended
claims.
* * * * *