U.S. patent application number 13/548376 was filed with the patent office on 2014-01-16 for coating/repairing process using electrospark with psp rod.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is David Vincent Bucci, Yan Cui, Srikanth Chandrudu Kottilingam, Dechao Lin, David Edward Schick, Brian Iee Tollison. Invention is credited to David Vincent Bucci, Yan Cui, Srikanth Chandrudu Kottilingam, Dechao Lin, David Edward Schick, Brian Iee Tollison.
Application Number | 20140017415 13/548376 |
Document ID | / |
Family ID | 48782995 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140017415 |
Kind Code |
A1 |
Lin; Dechao ; et
al. |
January 16, 2014 |
COATING/REPAIRING PROCESS USING ELECTROSPARK WITH PSP ROD
Abstract
An electrospark deposition electrode and an associated method
for depositing coatings using the electrode are provided. The
electrode includes a powder of a first metal and a powder of a
second metal. The second metal is a braze alloy including nickel,
the second metal having a lower melting point than the first metal.
The powder of the first metal and the powder of the second metal
are sintered together to form the electrode so that the powders are
comingled but not combined within the electrode. The method
includes depositing a layer of the first metal onto the substrate
using an electrospark deposition process.
Inventors: |
Lin; Dechao; (Greer, SC)
; Bucci; David Vincent; (Simpsonville, SC) ;
Kottilingam; Srikanth Chandrudu; (Simpsonville, SC) ;
Cui; Yan; (Greer, SC) ; Tollison; Brian Iee;
(Honea Path, SC) ; Schick; David Edward;
(Greenville, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lin; Dechao
Bucci; David Vincent
Kottilingam; Srikanth Chandrudu
Cui; Yan
Tollison; Brian Iee
Schick; David Edward |
Greer
Simpsonville
Simpsonville
Greer
Honea Path
Greenville |
SC
SC
SC
SC
SC
SC |
US
US
US
US
US
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
48782995 |
Appl. No.: |
13/548376 |
Filed: |
July 13, 2012 |
Current U.S.
Class: |
427/580 ;
75/228 |
Current CPC
Class: |
B23P 6/045 20130101;
B23P 6/007 20130101; F01D 5/005 20130101; F05D 2230/31 20130101;
B23P 6/002 20130101; F01D 9/02 20130101; C23C 26/02 20130101; F01D
5/288 20130101; F05D 2300/177 20130101; F05D 2220/32 20130101; C23C
26/00 20130101; F05D 2300/516 20130101 |
Class at
Publication: |
427/580 ;
75/228 |
International
Class: |
C23C 4/06 20060101
C23C004/06; B22F 1/00 20060101 B22F001/00 |
Claims
1. An electrospark deposition electrode including: a powder of a
first metal; and a powder of a second metal, wherein the second
metal is a braze alloy including nickel, the powder of the second
metal having a lower melting point than the first metal, wherein
the powder of the first metal and the powder of the second metal
are sintered together to form the electrospark deposition electrode
so that the powder of the first metal and the powder of the second
metal are comingled but not combined within the electrospark
deposition electrode.
2. The electrospark deposition electrode according to claim 1,
wherein the first metal is a superalloy.
3. The electrospark deposition electrode according to claim 2,
wherein the superalloy includes a base alloying element of
nickel.
4. The electrospark deposition electrode according to claim 2,
wherein the superalloy includes a base alloying element of
cobalt.
5. The electrospark deposition electrode according to claim 2,
wherein the electrospark deposition electrode contains about 60%
superalloy and about 40% of the second metal.
6. The electrospark deposition electrode according to claim 2,
wherein the electrospark deposition electrode contains a maximum of
90% of the second metal.
7. The electrospark deposition electrode according to claim 2,
wherein the particle sizes of the superalloy and the second metal
are in the range between about 325 mesh (44 microns) and about 120
mesh (125 microns).
8. A method for the deposition of a coating on a substrate
including: providing a substrate; providing an electrospark
deposition electrode, wherein the electrospark deposition electrode
includes a powder of a first metal, a powder of a second metal,
wherein the second metal is a braze alloy including nickel, the
powder of the second metal having a lower melting point than the
first metal, wherein the powder of the first metal and the powder
of the second metal are sintered together to form the electrospark
deposition electrode so that the powder of the first metal and the
powder of the second metal are comingled but not combined within
the electrospark deposition electrode; and depositing a layer of
the first metal onto the substrate using an electrospark deposition
process.
9. The method according to claim 8, further including the step of
depositing an amount of the second metal onto the substrate.
10. The method according to claim 9, wherein the step of depositing
an amount of the second metal onto the substrate further includes
depositing a lower ratio of the second metal to the first metal
onto the substrate than the ratio of the second metal to the first
metal present within the electrospark deposition electrode.
11. The method according to claim 8, wherein the step of depositing
a layer of the first metal onto the substrate using an electrospark
deposition process includes creating a deposited layer with
relatively low surface roughness.
12. The method according to claim 11, wherein the deposited layer
has a surface roughness less than about 2.01 .mu.m.
13. The method according to claim 8, wherein the step of depositing
a layer of the first metal onto the substrate using an electrospark
deposition process includes conducting the electrospark deposition
process in an atmosphere of an inert gas.
14. The method according to claim 13, wherein the inert gas is
argon.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to electrospark deposition, and
specifically relates to electrospark deposition using a sintered
electrode containing powders of a superalloy and a braze alloy.
[0003] 2. Discussion of Prior Art
[0004] Electrospark deposition (ESD) is a technique that can be
used to deposit a metal-containing alloy from an electrode onto a
substrate. ESD is used in a number of operations such as repairing,
coating, welding, and micro-welding metal-containing substrates.
Example uses of ESD include, but are not limited to, coating or
repair operations in die manufacturing and turbine component
repair.
[0005] Relatively rough coating or weld materials on the surfaces
of substrates can negatively affect certain desired characteristics
of the substrate-containing component. In one example, rough welds
in dies can create surface imperfections on die cast parts. In
another example, rough coatings on turbine components can decrease
the efficiency of a jet turbine. Each of these examples often
requires a separate subsequent operation, or re-work, to decrease
the surface roughness of the coating or weld material. Therefore,
there is a need for an improved coating and/or repairing process
using ESD to deposit metal-containing alloys onto a substrate.
BRIEF DESCRIPTION OF THE INVENTION
[0006] The following summary presents a simplified summary in order
to provide a basic understanding of some aspects of the systems
and/or methods discussed herein. This summary is not an extensive
overview of the systems and/or methods discussed herein. It is not
intended to identify key/critical elements or to delineate the
scope of such systems and/or methods. Its sole purpose is to
present some concepts in a simplified form as a prelude to the more
detailed description that is presented later.
[0007] One aspect of the invention provides an electrospark
deposition electrode including a powder of a first metal and a
powder of a second metal. The second metal is a braze alloy
including nickel, the second metal having a lower melting point
than the first metal. The powder of the first metal and the powder
of the second metal are sintered together to form the electrospark
deposition electrode so that the powder of the first metal and the
powder of the second metal are comingled but not combined within
the electrospark deposition electrode.
[0008] Another aspect of the invention provides a method for the
deposition of a coating on a substrate. The method includes
providing a substrate and providing an electrospark deposition
electrode. The electrospark deposition electrode includes a powder
of a first metal and a powder of a second metal. The second metal
is a braze alloy including nickel, the second metal having a lower
melting point than the first metal. The powder of the first metal
and the powder of the second metal are sintered together to form
the electrospark deposition electrode so that the powder of the
first metal and the powder of the second metal are comingled but
not combined within the electrospark deposition electrode. The
method further includes depositing a layer of the first metal onto
the substrate using an electrospark deposition process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing and other aspects of the invention will become
apparent to those skilled in the art to which the invention relates
upon reading the following description with reference to the
accompanying drawings, in which:
[0010] FIG. 1 is a schematized representation of an electrospark
deposition coating or repairing process in accordance with an
aspect of the present invention;
[0011] FIG. 2 is a cross-sectional schematic view of the
electrospark deposition electrode taken along lines 2-2 of FIG.
1;
[0012] FIG. 3 is an enlarged view of a portion of the turbine
component and the coating of FIG. 1; and
[0013] FIG. 4 is a top level flow diagram of an example method of
deposition of a coating on a substrate in accordance with an aspect
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Example embodiments that incorporate one or more aspects of
the invention are described and illustrated in the drawings. These
illustrated examples are not intended to be a limitation on the
invention. For example, one or more aspects of the invention can be
utilized in other embodiments and even other types of devices.
Moreover, certain terminology is used herein for convenience only
and is not to be taken as a limitation on the invention. Still
further, in the drawings, the same reference numerals are employed
for designating the same elements.
[0015] Coating and repairing operations utilizing ESD can be
beneficial when compared to other metal deposition processes used
in die manufacturing or turbine component repair. The ESD process
tends to minimize the heat affected zone (HAZ) of the substrate.
The HAZ can be defined as a volume of the substrate where the
microstructure and properties of the substrate have been altered by
the ESD process. Minimizing the HAZ can be beneficial for turbine
components in order to retain the designed performance
characteristics of the turbine component. The ESD process also
tends to minimize dilution in the metal deposition process.
Dilution can be defined as the weight percentage of the substrate
in the diffusion layer and deposited material to the total weight
of material in the diffusion layer and the deposited material. For
example, in a given volume of the diffusion layer and the deposited
material, 30 parts of substrate material per 100 parts of ESD
deposit yields 30% dilution.
[0016] Turbine components, such as those in natural gas turbines or
jet turbines can be subjected to relatively high levels of fatigue
from such factors as high operating temperature, thermal cycling,
and cyclic mechanical loading during normal operation. Material
fatigue from these factors and others can cause cracks or fissures
to develop in turbine components such as bucket, nozzle, and shroud
components. These cracks and/or fissures may lead to degradation of
turbine performance or even part failure. Creep is another factor
leading to degradation of turbine performance and can be defined as
a slow plastic deformation that occurs in a component under stress
at high temperature. Creep gradually exhausts the plastic
deformation capability of the component, which can lead to
component failure.
[0017] ESD can be used in several ways to increase the lifespan of
turbine components. In one example, ESD is used to restore or at
least partially restore the turbine component to its original
state. In a more specific example, ESD can be used to repair cracks
caused by the fatigue modes described above. In another example,
material is milled from turbine components exhibiting a significant
amount of creep after which ESD can be used to apply a coating on
the surface of the turbine component to restore the original
dimensions of the turbine component. In another example, a coating
can be applied to the surface of the turbine component using an ESD
process to increase resistance to the effects of high working
temperatures and corrosive atmospheres.
[0018] Many turbine components such as buckets, nozzles, and
shrouds are constructed of materials known as superalloys, which
exhibit material properties that are often beneficial for use in
turbine components. For example, superalloys can have relatively
high mechanical strength and creep resistance at high temperatures,
good surface stability, and corrosion and oxidation resistance.
When applying coatings or conducting repairs to turbine components,
it can be beneficial to include these same properties in the
coating or repair material so that the coating or repair material
have the same or similar properties to withstand a typical
operating environment of turbine components. In one example, the
ESD process can deposit an amount of a superalloy onto the surface
of a turbine component constructed of the same or a different
superalloy. There are a number of commercially available
superalloys, one example being the metallic alloy sold under the
trademark INCONEL alloy 718 (INCONEL is a registered trademark of
Huntington Alloys Corporation). Table A shows a representative
elemental chemical composition found in superalloy INCONEL 718.
TABLE-US-00001 TABLE A Element Weight Percent Nickel 50.0-55.0%
Chromium 17.0-21.0% Niobium and Tantalum 4.75-5.50% Molybdenum
2.80-3.30% Aluminum 0.2-0.8% Titanium 0.65-1.15% Carbon 0.08%
maximum Silicon 0.350% maximum Manganese 0.350% maximum Sulfur
0.015% maximum Copper 0.300% maximum Phosphorus 0.015% maximum
Cobalt 1.00% maximum Iron Balance
Other examples of superalloys include, but are not limited to, some
stainless steel-based alloys, solid solution materials using nickel
as a base alloying element such as INCONEL alloy 625, the metallic
alloy sold under the trademark HAYNES 230 (HAYNES and 230 are
registered trademarks of Haynes International, Inc.), precipitation
hardenable superalloys such as Rene 41, the metallic alloy sold
under the trademark HAYNES 282 (282 is a registered trademark of
Haynes International, Inc.), Waspaloy, INCONEL alloy 718, the
metallic alloy sold under the trademark GTD-111 (GTD-111 is a
registered trademark of General Electric Company), the metallic
alloy sold under the trademark GTD-222 (GTD-222 is a registered
trademark of General Electric Company), the metallic alloy sold
under the trademark GTD-444 (GTD-444 is a registered trademark of
General Electric Company), Rene 108, Rene N4, Rene N5, and
materials using cobalt as a base alloying element such as HAYNES 25
and FSX414.
[0019] Turning to FIG. 1, ESD can be used to deposit a superalloy
onto a surface 12 of a turbine component 14, which is one example
of a substrate. An applicator 16 can be moved in the direction of
arrow 18 relative to the turbine component 14. The applicator 16
can hold an ESD electrode 20 in close proximity to the surface 12
of the turbine component 14. Pulses of electrical energy create
high temperatures at the tip 24 of the ESD electrode 20 and ionize
the constituent components of the ESD electrode 20. The ionized
components are drawn to the negatively charged turbine component 14
where the ionized components produce an alloy with the turbine
component 14 in a diffusion layer 26 and deposit a layer, or
coating 30, on the diffusion layer 26. The ESD electrode 20 can be
rotated in the direction of arrow 28 during the ESD process to
foster even erosion of the consumable ESD electrode 20. An
atmosphere 34 of inert gas can be provided around the ESD process
location to help prevent oxidation of the ionized components. In
one example, the inert gas is argon, although any suitable inert
gas can be used.
[0020] FIG. 2 shows a cross-sectional view of an example ESD
electrode 20. The ESD electrode can include a powder of a first
metal 36 and a powder of a second metal 38. The two powders are
sintered together so that the powder of the first metal 36 and the
powder of the second metal 38 do not combine to form one alloy, but
instead are comingled within the ESD electrode 20. It is to be
appreciated that FIG. 2 is only a schematic representation of the
cross-sectional view to demonstrate that the first metal 36 and the
second metal 38 are comingled and not combined. The representation
of FIG. 2 is not meant to be representative of grain shape, size,
structure, etc.
[0021] The first metal 36 can be a superalloy that is to be
deposited onto a substrate such as a die or a turbine component 14
(best seen in FIG. 1). The second metal 38 is a nickel-containing
braze alloy that has a lower melting point than the superalloy.
Several suitable examples of braze alloys are contemplated, such as
BNi-2, BNi-5, BNi-9, the metallic alloy sold under the trademark
AMDRY 915 (AMDRY is a registered trademark of Sulzer Metco
Management AG), AMDRY DF-4B, AMDRY D-15, Mar-M-509B, AMDRY BRB, and
others. Additionally, the superalloy and the braze alloy could be
presintered preforms such as combinations of Mar-M-247/AMDRY DF-4B,
Rene R142/AMDRY BRB, Rene 80/AMDRY D-15. Any suitable ratio of
superalloy to braze alloy can be selected for use in the ESD
electrode 20. In one example, the ESD electrode 20 includes 90%
superalloy and 10% braze alloy, while in another example, the ESD
electrode 20 includes 10% superalloy and 90% braze alloy. Any
number of suitable combinations of superalloys and braze alloys in
a complete range of mixtures may be used. For example, any one or a
combination of the following superalloys: Rene 108, Rene 142, Rene
195, Rene N5, GTD-111, GTD-444, and Mar-M-247 can be used with any
one or a combination of the following braze alloys: AMDRY DF-4B,
Mar-M-509B, AMDRY BRB, AMDRY D-15, and AMDRY D-15 M2, or similar
braze alloys.
[0022] Additionally, various particle sizes of the superalloy and
braze alloy are contemplated for use in the ESD electrode 20. In
one example, the particle sizes of the superalloy and the braze
alloy are within the range between about 325 mesh (44 microns) and
about 120 mesh (125 microns). The described ESD electrode 20
including a suitable combination of superalloy and braze alloy with
suitable particle sizes can be termed a PSP rod, or pre-sintered
pre-formed rod.
[0023] It has been found that the presence of the lower melting
point nickel-containing braze alloy within the ESD electrode 20
benefits the ESD process. The nickel-containing braze alloy
promotes spark production between the ESD electrode and the
substrate. This increased spark production can permit greater speed
in the ESD process to cover more substrate area in a given amount
of time. The nickel-containing braze alloy can also increase the
deposition rate or mass transfer of the superalloy, which can
result in a thicker coating 30 on the substrate. Multiple layers
can be applied in cases where a thicker coating 30 is required.
Additionally, the presence of the lower melting point
nickel-containing braze alloy can increase metallurgical bonding
between the superalloy and the substrate due to wetting and
spreading effects of the braze alloy.
[0024] ESD weld repair and coatings 30 can be present in high
temperature applications such as dies for casting or extrusion and
turbine components 14. These high temperature environments can
negatively affect lower melting point braze alloys. The described
ESD electrode 20 permits the deposition of more heat resistant
superalloy onto the substrate while depositing lesser amounts of
the braze alloy onto the substrate. In one example, the superalloy
is deposited onto the substrate while no braze alloy is deposited
onto the substrate so that the finished product does not contain
all of the constituent parts of the ESD electrode. In another
example, braze alloy is deposited onto the substrate with the
superalloy in a lower ratio than is present within the ESD
electrode.
[0025] The braze alloy is a vehicle for aiding the deposition of
the superalloy powder onto the substrate. It is contemplated that a
percentage of the braze alloy can be deposited onto the substrate
from 0% to a percentage that is less than the percentage of the
braze alloy contained within the ESD electrode. The percentage of
braze alloy deposited onto the substrate can be limited so that the
amount of braze alloy deposited on the substrate does not affect
downstream performance of the substrate containing component. Any
number of principles can be at work to limit the amount of braze
alloy deposited onto the substrate including, but not limited to,
the ionized braze alloy not bonding to the substrate and the braze
alloy forming a powder on the surface of the substrate and/or the
coating 30 which is easily removed.
[0026] Turning to FIG. 3, one variable of a coating 30 or repair
weld deposited by the ESD electrode 20 (best seen in FIG. 1) is the
surface roughness. Increased surface roughness of the turbine
component 14 can lead to increased friction loss through the
turbine resulting in pressure loss, efficiency losses, and
disruption of the heat transfer capabilities of the turbine
component 14. As a result, it is often desirable to minimize the
roughness of any repair material and/or coating 30 on the surface
of the turbine component 14. R.sub.a is one common roughness
parameter used to evaluate the roughness of a surface representing
the arithmetic average of the absolute values of distances 44
measured from a mean line 46 to the individual peaks and valleys of
the coating 30.
[0027] The presence of the lower melting point nickel-containing
braze alloy within the ESD electrode 20 has been shown to reduce
the R.sub.a value of the coating 30 which can be beneficial when
depositing material on dies or turbine components 14. Furthermore,
the ratio of the superalloy powder to the braze alloy powder within
the ESD electrode 20 affects the R.sub.a value of the coating 30.
In one specific example, a ratio of 60 parts superalloy powder to
40 parts braze alloy powder within the ESD electrode 20 produces a
coating 30 with an R.sub.a value of 2.01 .mu.m. The ratio of the
superalloy powder to the braze alloy powder can be adjusted to
produce a coating 30 with an R.sub.a value that is suitable for the
substrate containing component to eliminate the need for re-work
required to reduce the R.sub.a value of the coating 30 to a
suitable value. Different suitable ratios of superalloy powder to
braze alloy powder can be selected for different turbine components
14 such as buckets, nozzles, and shrouds when using the described
repair or coating technique for turbine components 14. The
different ratios can be dependent upon the designed operating
requirements. It is to be appreciated that selection of suitable
superalloys and braze alloys can also affect the R.sub.a roughness
value of the coating 30.
[0028] An example method of deposition of a coating 30 on a
substrate is generally described in FIG. 4. The method can be
performed in connection with the example ESD electrode 20 shown in
FIGS. 1 and 3. The method includes the step 110 of providing a
substrate. The substrate can be a metal or a superalloy designed
for specific performance characteristics such as superior high
mechanical strength and creep resistance at high temperatures, good
surface stability, and corrosion and oxidation resistance.
[0029] The method further includes the step 120 of providing an ESD
electrode 20. The ESD electrode 20 includes a powder of a first
metal 36, which can be a superalloy. The ESD electrode 20 also
includes a powder of a second metal 38 which is a braze alloy
including nickel. The braze alloy has a lower melting point than
the first metal. The powder of the first metal 36 and the powder of
the braze alloy are sintered together to form the ESD electrode 20
so that the powder of the first metal 36 and the powder of the
braze alloy are comingled but not combined within the ESD
electrode.
[0030] The method also includes the step 130 of depositing a layer,
or coating 30, of the first metal onto the substrate using an ESD
process. Pulses of electrical energy create high temperatures at
the tip of the ESD electrode 20 and ionize the constituent
components of the ESD electrode 20. The ionized components are
drawn to the negatively charged substrate where the ionized
components produce an alloy with the turbine component in a
diffusion layer and create a coating 30 on the diffusion layer.
[0031] The method can further include the step of depositing an
amount of the braze alloy onto the substrate. A lower ratio of the
braze alloy to the first metal 36 is deposited onto the substrate
than the ratio of the second metal 38 to the first metal 36 present
within the ESD electrode 20. The deposited coating 30 can have a
relatively low surface roughness. In one example, the R.sub.a value
of the surface roughness is less than about 2.01 .mu.m.
[0032] Specific Example 1: A combination of 60% superalloy powder
and 40% nickel-based braze alloy powder were sintered together to
form an ESD electrode of 0.64 cm (1/4-in) diameter and 2.54 cm
(1-in) length. The ESD electrode was used to deposit a 0.013 cm
(0.005-in) coating of the superalloy onto a substrate with an
R.sub.a value of 2.01 .mu.m. Additional layers of the coating were
applied as needed.
[0033] In the above-described examples, the method and apparatus
provide means for depositing a layer, or coating, of a metal such
as a superalloy onto a substrate. Application of the superalloy for
welding, micro-repair, or coating operations is conducted with an
electrospark deposition technique. The resultant substrate coating
contains a ratio of braze alloy to superalloy that is lower than
the ratio of braze alloy to superalloy contained within the ESD
electrode. The ratio of the two alloys can be modified to produce
coatings with relatively low R.sub.a roughness values. The low
R.sub.a values can be considered to be an acceptable for downstream
applications of the substrate containing component such that the
component does not require further re-work operations such as laser
treatments, grinding, ultrasonic treatments, or the like to achieve
the desired R.sub.a values. Additionally, the method and apparatus
provide an alternative to coating operations that required multiple
steps to achieve a desired R.sub.a value. The ESD operations are
relatively low-cost and of relatively simple operation. It is to be
appreciated that the described method and apparatus can be used
with shielding devices so that deposition can take place only on
particular sections of substrate.
[0034] The invention has been described with reference to the
example embodiments described above. Modifications and alterations
will occur to others upon a reading and understanding of this
specification. Example embodiments incorporating one or more
aspects of the invention are intended to include all such
modifications and alterations insofar as they come within the scope
of the appended claims.
* * * * *