U.S. patent application number 11/835031 was filed with the patent office on 2009-02-12 for braze alloy composition with enhanced oxidation resistance and methods of using the same.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Gene A. Murphy, Sujith Sathian.
Application Number | 20090041611 11/835031 |
Document ID | / |
Family ID | 39941501 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090041611 |
Kind Code |
A1 |
Sathian; Sujith ; et
al. |
February 12, 2009 |
BRAZE ALLOY COMPOSITION WITH ENHANCED OXIDATION RESISTANCE AND
METHODS OF USING THE SAME
Abstract
A cobalt-based braze alloy composition comprises: 22 to 24.75%
chromium by weight; 9 to 11% nickel by weight; 6.5 to 7.6% tungsten
by weight; 3 to 4% tantalum by weight; 0.55 to 0.65% carbon by
weight; 0.3 to 0.6% zirconium by weight; 0.15 to 0.3% titanium by
weight; 1.5 to 2.6% boron by weight; 1 to 10% silicon by weight;
and cobalt. There are also provided methods of using the same.
Inventors: |
Sathian; Sujith;
(Simpsonville, SC) ; Murphy; Gene A.; (Pelzer,
SC) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
39941501 |
Appl. No.: |
11/835031 |
Filed: |
August 7, 2007 |
Current U.S.
Class: |
419/29 ; 420/439;
420/586; 420/588 |
Current CPC
Class: |
C22F 1/10 20130101; C22C
19/07 20130101; B23K 35/3046 20130101 |
Class at
Publication: |
419/29 ; 420/439;
420/588; 420/586 |
International
Class: |
B22F 1/00 20060101
B22F001/00; C22C 19/07 20060101 C22C019/07; C22C 30/00 20060101
C22C030/00 |
Claims
1. A cobalt-based braze alloy composition comprising: 22 to 24.75%
chromium by weight; 9 to 11% nickel by weight; 6.5 to 7.6% tungsten
by weight; 3 to 4% tantalum by weight; 0.55 to 0.65% carbon by
weight; 0.3 to 0.6% zirconium by weight; 0.15 to 0.3% titanium by
weight; 1.5 to 2.6% boron by weight; 1 to 10% silicon by weight;
and cobalt.
2. The cobalt-based braze alloy composition of claim 1 further
comprising: up to 1.3% iron by weight; up to 0.10% manganese by
weight; and up to 0.02% sulfur by weight.
3. The cobalt-based braze alloy composition of claim 1 further
comprising: 2 to 2.6% boron by weight; and 2.5 to 7.5% silicon by
weight.
4. The cobalt-based braze alloy composition of claim 1 further
comprising: 2.45 to 2.55% boron by weight; and 4 to 6% silicon by
weight.
5. The cobalt-based braze alloy composition of claim 1 consisting
of: 22 to 24.75% chromium by weight; 9 to 11% nickel by weight; 6.5
to 7.6% tungsten by weight; 3 to 4% tantalum by weight; 0.55 to
0.65% carbon by weight; 0.3 to 0.6% zirconium by weight; 0.15 to
0.3% titanium by weight; 1.5 to 2.6% boron by weight; 1 to 10%
silicon by weight; up to 1.3% iron by weight; up to 0.10% manganese
by weight; and up to 0.02% sulfur by weight; and cobalt.
6. A method of repairing or reconstructing a superalloy component
comprising the steps of: forming a presintered preform by mixing a
hardface alloy powder with a cobalt-based braze alloy composition
comprising 22 to 24.75% chromium by weight, 9 to 11% nickel by
weight, 6.5 to 7.6% tungsten by weight, 3 to 4% tantalum by weight,
0.55 to 0.65% carbon by weight, 0.3 to 0.6% zirconium by weight,
0.15 to 0.3% titanium by weight, 1.5 to 2.6% boron by weight, 1 to
10% silicon by weight, and cobalt; wherein the presintered preform
comprises 60-90% hardface alloy powder by weight and 10-40%
cobalt-based braze alloy composition by weight; sintering the
presintered preform to make a sintered component; shaping the
sintered component; welding the sintered component to the
superalloy component to form a combination; and subjecting the
combination to a heat treatment cycle.
7. The method of claim 6, wherein the heat treatment cycle
comprises a heating cycle sub-step and a cooling cycle
sub-step.
8. The method of claim 6, wherein the superalloy component
comprises a component of a gas turbine.
9. The method of claim 6, wherein the superalloy component is a
bucket angel wing or a bucket tip.
10. The method of claim 6, wherein the heat treatment cycle
comprises the steps of: heating a furnace to 650.degree. C. at a
rate of 14.degree. C./minute; maintaining a temperature of
650.degree. C. for 30 minutes; heating the furnace to 980.degree.
C. at a rate of 14.degree. C./minute; maintaining a temperature of
980.degree. C. for 30 minutes; heating the furnace to 1204 to
1218.degree. C. at a rate of 19.degree. C./minute; maintaining a
temperature of 1204 to 1218.degree. C. for 20 minutes; cooling the
furnace to a temperature of 1120.degree. C.; maintaining a
temperature of 1120.degree. C. for 30 minutes; and cooling the
furnace to a temperature of 815.degree. C.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to a braze alloy
composition that may have enhanced oxidation resistance at elevated
temperature.
[0002] Components in a high-temperature or extreme environment,
such as a hot-gas-path airfoil in a gas turbine, may experience
degradation or may have issues relating to durability. One method
of repairing such superalloys may involve pre-sintered performs
based upon braze alloys and/or superalloy metallic powders.
[0003] The present invention relates to a braze alloy that may be
mixed with superalloy metallic powders to form pre-sintered
preforms (PSPs). PSPs may be used in a variety of salvage and/or
repair applications, such as those involving the repair and/or
reconstruction of components incorporated into high-temperature
applications.
[0004] Braze powders are generally known in the art. One braze
powder is Mar M 509B. Mar M 509B is a cobalt-based braze alloy with
a boron additive.
[0005] The formulation of a PSP plate using Mar M 509B braze alloy
is shown in FIG. 1. As illustrated, hardface alloy powder (block
150) and Mar M 905B (block 152) are mixed (block 154), then
sintered (block 156) and shaped using a water-jet (block 158).
After shaping, the preform is tack welded (block 160), e.g., to a
bucket, and subjected to a cycle of heat treatment (block 162). A
PSP comprising Mar M 509B braze powder may contain approximately
50% Co, 10% Ni, 24% Cr, 4% Ta, 0.25% Ti, 8% W, 0.5% C, and 2.7% B
by weight. In certain embodiments, the present invention relates to
braze powders having a greater weight percentage of silicon and
boron. The silicon content in certain embodiments of the inventive
composition may provide advantageous oxidation resistance. The
elevated concentrations of silicon and boron content may facilitate
the lowering of the melting point for the composition. The boron
content in certain embodiments of the inventive composition may
facilitate bonding between a PSP and superalloy hardware during
brazing operation.
[0006] In certain embodiments of the present invention, a process
using a particular braze alloy composition may be easy to apply and
may require minimal surface preparation before brazing and minimal
machining after the hardface operation.
[0007] In certain embodiments, PSPs using this braze alloy may be
made to near-net shape and brazed on to the bucket. This may
provide robustness, repeatability and reproducibility while perhaps
reducing the extent of post-hardface machining.
BRIEF DESCRIPTION OF THE INVENTION
[0008] In an embodiment, there is a cobalt-based braze alloy
composition comprising: 22 to 24.75% chromium by weight; 9 to 11%
nickel by weight; 6.5 to 7.6% tungsten by weight; 3 to 4% tantalum
by weight; 0.55 to 0.65% carbon by weight; 0.3 to 0.6% zirconium by
weight; 0.15 to 0.3% titanium by weight; 1.5 to 2.6% boron by
weight; 1 to 10% silicon by weight; and cobalt.
[0009] In another embodiment, there is a method of repair or
reconstructing a superalloy component comprising the steps of:
forming a presintered preform by mixing a hardface alloy powder
with a cobalt-based braze alloy comprising 22 to 24.75% chromium by
weight, 9 to 11% nickel by weight, 6.5 to 7.6% tungsten by weight,
3 to 4% tantalum by weight, 0.55 to 0.65% carbon by weight, 0.3 to
0.6% zirconium by weight, 0.15 to 0.3% titanium by weight, 1.5 to
2.6% boron by weight, 1 to 10% silicon by weight, and cobalt;
sintering the presintered preform to make a sintered component;
shaping the sintered component; welding the sintered component to
the superalloy component to form a combination; and subjecting the
combination to a heat treatment cycle. The presintered preform
comprises 60-90% hardface alloy powder by weight and 10-40%
cobalt-based braze alloy composition by weight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a flowchart illustrating process steps involved in
making and using a presintered preform.
[0011] FIG. 2 shows an example of hot gas path side bucket angel
wing repaired using a PSP in accordance with an embodiment of the
present invention.
[0012] FIG. 3 illustrates a hot gas path bucket tip that was
repaired using a PSP in accordance with an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The present invention generally relates to a braze alloy
composition that may have enhanced oxidation resistance at elevated
temperature.
[0014] In certain embodiments, there is a braze alloy composition
having an enhanced resistance to oxidation at elevated temperature.
As an exemplary starting point, commercially available Mar M 509B
braze powder may be used as a baseline composition for the
development of a braze alloy in accordance with an embodiment of
this invention. If compared with Mar M 509B, there may be an
additional (e.g., 5%) silicon and additional (e.g., 2%) boron
content. The silicon content in certain embodiments of the
inventive composition may provide advantageous oxidation
resistance. The elevated concentrations of silicon and boron
content may facilitate the lowering of the melting point for the
composition. The boron content in certain embodiments of the
inventive composition may facilitate bonding between a pre-sintered
preform (PSP) and superalloy hardware during brazing operation.
[0015] In an embodiment, the braze alloy may be mixed with
superalloy metallic powders to form a PSP. A PSP may be used, for
example, in salvaging and/or repairing hot-gap-path components,
such as those found in gas turbines. A good bond between the PSP
and superalloy hardware may be obtained with a heat-treatment cycle
when using a braze alloy in accordance with an embodiment of the
present invention.
[0016] In an embodiment, a PSP may also contain Tribaloy T800 in
powdered form. T800 is a cobalt-based hardface alloy produced by
Deloro Stellite Inc., Belleville, Ontario, Canada. A suitable PSP
may be available from Morgan Advanced Ceramics (Wesgo Metals
Division), 2425 Whipple Road, Hayward, Calif. 94644. T800 has the
following constituents by their approximate weight percentage:
TABLE-US-00001 TABLE 1 Composition of T800 Component Weight
Percentage Co Balance Mo 27.00-30.00 Cr 16.50-18.50 Si 3.00-3.80 Fe
1.50 (maximum) Ni 1.50 (maximum) O 0.15 (maximum) C 0.08 (maximum)
P 0.03 (maximum) S 0.03 (maximum)
[0017] In certain embodiments, PSPs that can be used for superalloy
applications may include 60-90% (and all subranges therebetween)
T800 or CM 64 powder by weight and 40-10% (and all subranges
therebetween) of a braze alloy composition by weight (as described
herein). Coast Metal (CM) 64 powder may be available from Morgan
Advanced Ceramics (Wesgo Metals Division). CM 64 has the following
constituents by their approximate weight percentage:
TABLE-US-00002 TABLE 2 Composition of CM 64 Component Weight
Percentage Co Balance Cr 26-30 W 18-21 Ni 4-6 C 0.7-1.0 V 0.75-1.25
Fe 3 (maximum) Si 1 (maximum) Mn 1 (maximum) B 0.05 (maximum) Mo
0.5 (maximum)
[0018] Commercially available brazing material Mar M 509B in
powdered form may be used. M 509B is a cobalt-based braze alloy
with a boron additive and has the following constituents by their
approximate weight percentage:
TABLE-US-00003 TABLE 3 Composition of Mar M 509B Component Weight
Percentage Co Balance Cr 22.00-24.75 Ni 9.00-11.00 W 6.50-7.60 Ta
3.00-4.00 B 2.60-3.16 C 0.55-0.65 Zr 0.30-0.60 Ti 0.15-0.30 Fe 1.30
(maximum) Si 0.40 (maximum) Mn 0.10 (maximum) S 0.02 (maximum)
[0019] In exemplary embodiments, there is a braze alloy composition
with enhanced oxidation resistance at elevated temperature. In
exemplary embodiments, the alloy contains approximately 5% silicon
and 2.5% boron content with similar chemical composition as Mar M
509B with an approximately 5% lower cobalt content. In accordance
with other exemplary embodiments, the silicon weight percentage may
vary from 1 to 10%, and all subranges therebetwen, from 2.5 to
7.5%, and all subranges therebetween, or from 4 to 6%, and all
subranges therebetween. And in accordance with exemplary
embodiments, the boron weight percentage may vary from 1.5 to 2.6%,
and all subranges therebetween, or from 2 to 2.6%, or from 2.45 to
2.55%, and all subranges therebetween.
[0020] In certain embodiments, silicon in this super-alloy may
enhance oxidation resistance. The presence of both silicon and
boron may be effective in lowering the melting point to obtain good
bond between the PSP and superalloy hardware. In an embodiment, the
braze alloy may be a cobalt-based braze alloy with less boron
additive and higher additives of silicon by their approximate
weight percentage (all stated ranges include all subranges
therebetween):
TABLE-US-00004 TABLE 4 Composition of exemplary embodiments of the
present invention Component Weight Percentage Co Balance Cr
22.00-24.75 Ni 9.00-11.00 W 6.50-7.60 Ta 3.00-4.00 B 1.50-2.60 C
0.55-0.65 Zr 0.30-0.60 Ti 0.15-0.30 Fe 1.30 (maximum) Si 1.00-10.00
Mn 0.10 (maximum) S 0.02 (maximum)
[0021] The formulation of a PSP plate using a braze alloy includes
mixing a hardface alloy powder (such as T800) and a composition
made in accordance with an exemplary embodiment. This mixture is
then sintered and shaped, such as with a water-jet. After shaping,
the preform is tack welded to a component potentially in need of
repair and subjected to a cycle of heat treatment.
[0022] In an embodiment, the following heat-treatment cycle may be
used on hot-gas-path components using a PSP containing a braze
alloy. Heat-treatment may include a heating cycle sub-step and a
cooling cycle sub-step. The heating cycle sub-step may include
placing a superalloy part with preform into a brazing furnace that
is at room temperature, e.g., approximately 21.degree. C.
(70.degree. F.). To facilitate the bonding process, a non-oxidizing
atmosphere within the furnace and a method of inducing a pressure
on hardface preform may be provided in accordance with methods
well-known to practitioners in the art. The furnace used may be a
vacuum furnace, and a minimum vacuum requirement can be
0.5.times.10-3 Torr.
[0023] The furnace may be heated to approximately 650.degree. C.
(1200.degree. F.) at a rate of approximately 14.degree. C./minute
(25.degree. F./minute). Once approximately 650.degree. C.
(1200.degree. F.) is attained, this temperature may be maintained
for approximately 30 minutes. Then the furnace temperature may be
increased to approximately 980.degree. C. (1800.degree. F.) at a
rate of approximately 14.degree. C./minute (25.degree. F./minute).
Once approximately 980.degree. C. (1800.degree. F.) is attained,
this temperature may be maintained for approximately 30 minutes.
Then the furnace temperature is increased to approximately 1204 to
1218.degree. C. (2200 to 2225.degree. F.) at a rate of
approximately 19.degree. C./minute (35.degree. F./minute). Once
approximately 1204 to 1218.degree. C. (2200 to 2225.degree. F.) is
attained, this temperature may be maintained for approximately 20
minutes. The furnace may then be cooled to a temperature of about
1120.degree. C. (2050.degree. F.) for about sixty minutes, then
further cooled to 815.degree. C. (1500.degree. F.). The furnace may
be subsequently cooled to approximately room temperature at any
temperature.
[0024] The table below summarizes test results for an oxidation
test conducted at 2000.degree. F. for 500 hours for PSPs made with
T800 and either Mar M 509B or a braze alloy made in accordance with
an embodiment of the present invention. The oxidation test was
conducted in an air furnace. The samples were first placed in the
air furnace at 2000.degree. F. for 500 hrs (.about.21 days). After
500 hrs, the samples were taken out from the furnace and cooled in
air. Metallography analysis was conducted to check the oxidation
resistance; samples were sectioned, polished, and etched to check
for the oxidation layer thickness. These test results show enhanced
oxidation resistance.
TABLE-US-00005 TABLE 5 Comparison of oxidation resistance of T800
PSP (PSPs made with 15% Mar M 509B braze alloy vs. with 15% of
braze alloy in accordance with an exemplary embodiment) Oxidation
Braze PSP Depth Temperature (Braze Hardness @ 2000.degree. F./ (20
min), Alloy) Composition (Rc) 500 hr Range Mar M 509B 85/15 51-59
~3 mils 2175-2225.degree. F. (2.6% B) (2200.degree. F.) Embodiment
85/15 53-56 ~2.5 mils 2175-2225.degree. F. of Braze (2200.degree.
F.) Alloy (2% B; 5% Si) Weld Metal 100 55-62 ~5 mils NA
[0025] In exemplary embodiments, the use of this braze alloy in
PSPs may be made to near-net shape and brazed on to the bucket,
thus providing robustness, repeatability and reproducibility while
reducing the extent of post-hardface machining. Further, perform
brazing operation may be coupled with the typical coating heat
treatments in order to reduce the present manufacturing
schedule.
[0026] In exemplary embodiments, the present invention may be
useful in repairing and/or reconstructing components in a gas
turbine, such as, for example, those illustrated in U.S. Pat. Nos.
6,506,016 and 6,890,150, which are incorporated herein by
reference.
[0027] For example, FIG. 2 shows an example of hot gas path side
bucket angel wing repaired using a PSP in accordance with an
embodiment of the present invention. In FIG. 2, a shank 202 (at or
near the base of a bucket, not shown) with axially projecting angel
wing seals 210 and 212 is shown. The angel wing seals have been
repaired in accordance with an embodiment of the present invention.
Similarly, FIG. 3 illustrates a hot gas path bucket tip that was
repaired using a PSP in accordance with an embodiment of the
present invention. In FIG. 3, bucket tip 304 contains a cutter
tooth 330 that has been repaired. This new developed braze alloy
can be used for making PSPs or used for making and/or
repairing/servicing buckets. The application, therefore, may be
wide and across many product lines.
[0028] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
[0029] Furthermore, all numbers and numerical ranges described and
claimed herein are approximate and include some degree of
variation, regardless of whether expressly designated.
* * * * *