U.S. patent application number 13/962477 was filed with the patent office on 2013-11-28 for method of applying a wear resistant coating.
This patent application is currently assigned to United Technologies Corporation. The applicant listed for this patent is United Technologies Corporation. Invention is credited to Eli N. Ross, Paul H. Zajchowski.
Application Number | 20130316086 13/962477 |
Document ID | / |
Family ID | 39671649 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130316086 |
Kind Code |
A1 |
Ross; Eli N. ; et
al. |
November 28, 2013 |
METHOD OF APPLYING A WEAR RESISTANT COATING
Abstract
A method of applying a wear-resistant coating comprises mixing
about 75% to about 85% by weight chromium carbide and about 15% to
about 25% by weight nickel chromium to form a chromium
carbide-nickel chromium mixture, and simultaneously heating the
chromium carbide-nickel chromium mixture to about 1371 degrees
Celsius to about 2204 degrees Celsius and applying the chromium
carbide-nickel chromium mixture at a velocity in a range of about
305 meters feet per second to about 915 meters per second by high
velocity oxygen fuel (HVOF) spraying.
Inventors: |
Ross; Eli N.; (Vernon,
CT) ; Zajchowski; Paul H.; (Enfield, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Hartford |
CT |
US |
|
|
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
39671649 |
Appl. No.: |
13/962477 |
Filed: |
August 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11805160 |
May 22, 2007 |
8530050 |
|
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13962477 |
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Current U.S.
Class: |
427/451 |
Current CPC
Class: |
Y10T 428/30 20150115;
Y10T 428/12014 20150115; Y10T 428/12028 20150115; B05D 3/08
20130101; C23C 4/06 20130101 |
Class at
Publication: |
427/451 |
International
Class: |
B05D 3/08 20060101
B05D003/08 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] This invention was made with government support under
Contract Number F33657-99-D-2051 awarded by the United States Air
Force. The government may have certain rights in the invention.
Claims
1. A method of applying a wear-resistant coating comprising: mixing
about 75% to about 85% by weight chromium carbide and about 15% to
about 25% by weight nickel chromium to form a chromium
carbide-nickel chromium mixture; and simultaneously heating the
chromium carbide-nickel chromium mixture to a temperature in a
range from about 1371 degrees Celsius to about 2204 degrees Celsius
and applying the chromium carbide-nickel chromium mixture at a
velocity in a range from about 305 meters feet per second to about
915 meters per second by high velocity oxygen fuel (HVOF)
spraying.
2. The method of claim 1, wherein spraying the chromium
carbide-nickel chromium mixture comprises spraying the chromium
carbide-nickel chromium mixture to a thickness in a range from
about 203 microns to about 762 microns as sprayed.
3. The method of claim 1, wherein spraying the chromium
carbide-nickel chromium mixture comprises using a fuel gas selected
from the group consisting of: hydrogen, kerosene, and
propylene.
4. The method of claim 3, wherein spraying the chromium
carbide-nickel chromium mixture comprises spraying a hydrogen fuel
gas at a flow rate in a range from about 661 liters per minute to
about 755 liters per minute and spraying oxygen fuel gas at a flow
rate in a range from about 189 liters per minute to about 283
liters per minute.
5. The method of claim 1, wherein mixing about 75% to about 85% by
weight chromium carbide and about 15% to about 25% by weight nickel
chromium comprises mixing about 80% by weight chromium carbide and
about 20% by weight nickel chromium.
6. The method of claim 1, wherein mixing about 75% to about 85% by
weight chromium carbide and about 15% to about 25% by weight nickel
chromium comprises mixing chromium carbide having a particle size
in a range from about 16 microns to about 45 microns and nickel
chromium having a particle size in a range from about 16 microns to
about 45 microns.
7. The method of claim 6, wherein the chromium carbide-nickel
chromium mixture is applied in the form of a blended powder or an
alloyed powder.
8. The method of claim 1, wherein a chromium carbide-nickel
chromium mixture is fed into an HVOF spray gun at a rate in a range
from about 45 grams per minute to about 90 grams per minute.
9. The method of claim 1, wherein the wear-resistant coating has a
substantially and predominantly lamellar splat structure with a
plurality of isolated regions of cuboidal carbide phases.
10. The method of claim 9, wherein the cuboidal carbide phases
consist essentially of a discrete mixture of cuboidal Cr3C2
carbides, substantially lamellar precipitated matrix carbides of
the form CrxCy where x=7 to 23 and y=3 to 6, fine lamellar nickel
oxides, and a fine lamellar Ni--Cr binder.
11. The method of claim 1, wherein the wear-resistant coating has:
a microhardness in a range from about 850 Vickers Hardness to about
1150 Vickers Hardness; a porosity of up to about 3%; and a nominal
oxide level in a range from about 10% to about 20%.
12. The method of claim 1, wherein the wear-resistant coating is
applied to a seal plate of a carbon seal.
13. A method of applying a wear-resistant coating, the method
comprising: mixing about 75% to about 85% by weight chromium
carbide and about 15% to about 25% by weight nickel chromium to
form a chromium carbide-nickel chromium mixture; using an HVOF
spray gun to spray a fuel gas at a flow rate in a range from about
661 liters per minute to about 755 liters per minute, and an oxygen
gas at a flow rate in a range from about 189 liters per minute to
about 283 liters per minute to generate a HVOF jet; feeding the
chromium carbide-nickel chromium mixture into the HVOF jet at a
rate in a range from about 45 grams per minute to about 90 grams
per minute, and at a velocity in a range from about 315 meters per
second to about 915 meters per second; heating the chromium
carbide-nickel chromium mixture in the HVOF jet to a temperature in
a range from about 1371 degrees Celsius to about 2204 degrees
Celsius; and depositing the chromium carbide-nickel chromium
mixture on a surface to form a wear-resistant coating.
14. The method of claim 13, and further comprising: spraying in the
HVOF jet a nitrogen carrier gas with the HVOF spray gun at a flow
rate in a range from about 11.8 liters per minute to about 16.5
liters per minute.
15. The method of claim 13, and further comprising: spraying in the
HVOF jet a cooling gas with the HVOF spray gun at a flow rate in a
range from about 283 liters per minute to about 425 liters per
minute.
16. The method of claim 13, wherein the surface is rotated at
speeds in a range from about 61 meters per minute to about 122
meters per minute.
17. The method of claim 13, wherein the HVOF spray gun is:
positioned a distance from the surface in a range from about 23
centimeters to about 30.5 centimeters; positioned at an angle in a
range from about 45 degrees to about 90 degrees relative to a
horizontal plane across the surface; and traversed at a speed in a
range from about 20.3 centimeters per minute to about 101.6
centimeters per minute.
18. The method of claim 13, wherein the wear-resistant coating is
deposited on the surface to form a substantially and predominantly
lamellar splat structure with a plurality of isolated regions of
cuboidal carbide phase, wherein the cuboidal carbide phases consist
essentially of a discrete mixture of cuboidal Cr3C2 carbides,
substantially lamellar precipitated matrix carbides of the form
CrxCy where x=7 to 23 and y=3 to 6, fine lamellar nickel oxides,
and a fine lamellar Ni--Cr binder.
19. The method of claim 13, wherein the wear-resistant coating is
applied to a thickness in a range from about 203 microns to about
762 microns.
20. A method of applying a wear-resistant coating comprising:
mixing about 75% to about 85% by weight chromium carbide and about
15% to about 25% by weight nickel chromium to form a chromium
carbide-nickel chromium mixture; and heating the chromium
carbide-nickel chromium mixture to a temperature in a range from
about 1371 degrees Celsius to about 2204 degrees Celsius; applying
the chromium carbide-nickel chromium mixture at a velocity in a
range from about 305 meters feet per second to about 915 meters per
second by high velocity oxygen fuel (HVOF) spraying; and impacting
the chromium carbide-nickel chromium mixture on a surface to form a
substantially and predominantly lamellar splat structure with a
plurality of isolated regions of cuboidal carbide phase.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims priority as a divisional application
under 35 U.S.C. .sctn.121 of earlier filed application Ser. No.
11/805,160 entitled "WEAR RESISTANT COATING" by Eli N. Ross and
Paul H. Zajchowski and filed May 22, 2007.
BACKGROUND
[0003] The present invention generally relates to the field of wear
resistant coatings. In particular, the present invention relates to
wear resistant coatings for carbon seals.
[0004] Successful operation and performance of gas turbine engine
bearing compartment carbon seals is strongly dependent on having a
hard, chemically stable, and thermal-shock resistant counterface
material system. The most common arrangement involves a static
carbon seal, spring and air loaded axially against a shaft
co-rotating ring, known as a seal plate or seal seat. The
counterface is defined as the region of the seal seat contacting
the axial and/or radial face of the carbon seal.
[0005] Historically, the counterface material system has consisted
of a low alloy steel protected with hard chromium plating (HCP) or
by a chromium carbide-nickel chromium coating applied by a
Detonation Gun (D-Gun), available from Praxair Surface
Technologies, Inc. Seal applications using HCP are typically
limited to lower speed applications, and the plating process
generates a heavily regulated hexavalent-chromium waste stream.
While a superior counterface to hard chromium plating, the chromium
carbide-nickel chromium coating applied by the D-Gun can exhibit
localized surface distress in the form of radial or craze-type
cracks due to thermal-mechanical stresses during operation. The
cracks occasionally propagate to the extent that the coating
material is liberated from the coated surface, either as discrete
pull-out or gross spallation.
[0006] Attempts have been made to either complement or improve upon
the D-Gun technology by depositing coatings using the continuous
combustion high velocity oxygen fuel (HVOF) method. These attempts
have been generally unsuccessful for application to a seal seat
coating running against gas turbine engine carbon seals. Potential
reasons include: the coatings were developed for other types of
wear applications involving different mating materials and
operating environments; carbide type and chemistry not
thermo-chemically stable for operation against carbon seals at high
power; and microstructures, primarily phase morphology and size,
were not optimized to resist the propagation of surface thermal
cracks into the thickness of the coating, often resulting in a
rapid and catastrophic breakdown of the coating and unacceptable
levels of carbon seal wear. It would be beneficial to develop a
coating applied by HVOF for use with carbon seals.
SUMMARY
[0007] The present disclosure is directed to a method of applying a
wear-resistant coating. The method comprises mixing about 75% to
about 85% by weight chromium carbide and about 15% to about 25% by
weight nickel chromium to form a chromium carbide-nickel chromium
mixture, and simultaneously heating the chromium carbide-nickel
chromium mixture to about 1371 degrees Celsius to about 2204
degrees Celsius and applying the chromium carbide-nickel chromium
mixture at a velocity in a range of about 305 meters feet per
second to about 915 meters per second by high velocity oxygen fuel
(HVOF) spraying.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of a wear-resistant coating of a
carbon seal interface.
[0009] FIG. 2 is a diagram of a method of applying the
wear-resistant coating onto a surface of a carbon seal
counterface.
DETAILED DESCRIPTION
[0010] FIG. 1 shows an exemplary embodiment of counterface 10
having wear-resistant coating 12 applied onto surface 14 of
counterface 10. Counterface 10 is used in conjunction with mating
surface 16 in a seal system, such as a carbon seal system. Coating
12 functions to protect surface 14 of counterface 10 against the
harsh environments of a gas turbine engine and against wear when
counterface 10 contacts mating surface 16. Coating 12 exhibits
desirable phase distribution, morphology, oxide level, porosity,
micro-hardness, and other characteristics for enhanced resistance
to the propagation of surface thermal cracks in coating 12 during
seal operation. In addition, use of coating 12 on counterface 10
reduces thermally-induced cracking or spallation, reduces wear in
mating surface 16, improves limits in build-up of coating 12, and
increases repair applicability. Although coating 12 is discussed as
being used in carbon seal applications, coating 12 may be used in
any application where wear-resistance is desirable.
[0011] Coating 12 is applied onto surface 14 of rotating
counterface 10. Surface 14 faces stationary mating surface 16.
Coating 12 may be applied onto surface 14 as a dense single phase
layer or as a composite. Coating 12 is formed of a chromium
carbide-nickel chromium composition and may be either a blended
powder or an alloyed powder. In an exemplary embodiment, coating 12
constitutes between approximately 75% and approximately 85% by
weight chromium carbide and between approximately 15% and
approximately 25% by weight nickel chromium. The composition
preferably constitutes approximately 80% by weight chromium carbide
and approximately 20% by weight nickel chromium. In an exemplary
embodiment, the particle size of the chromium carbide and the
nickel chromium is between approximately 16 microns and
approximately 45 microns. The particle size of the chromium carbide
and the nickel chromium is preferably approximately 30 microns.
[0012] Mating surface 16 is typically formed of a carbon source,
such as amorphous carbon or crystalline graphite. In an exemplary
embodiment, mating surface 16 is a stationary, solid graphite
ring.
[0013] Prior to applying coating 12 onto counterface 10,
counterface 10 is cleaned and the areas of counterface 10 that are
not to be coated are masked. Surface 14 of counterface 10 is then
grit-blasted to provide a roughened surface for improved coating
adhesion. Coating 12 is applied onto surface 14 of counterface 10
as a clad or alloyed powder by high velocity oxy-fuel (HVOF)
thermal spray process. In the HVOF thermal spray process, a high
velocity gas stream is formed by continuously combusting oxygen and
a gaseous or liquid fuel. A powdered form of the coating to be
deposited is injected into the high velocity gas stream and the
coating is heated proximate its melting point, accelerated, and
directed at the substrate to be coated. The HVOF process imparts
substantially more kinetic energy to the powder being deposited
than many existing thermal spray coating processes. As a result, an
HVOF applied coating exhibits considerably less residual tensile
stresses than other types of thermally sprayed coatings.
Oftentimes, the residual stresses in the coating are compressive
rather than tensile. These compressive stresses also contribute to
the increased coating density and higher coating thickness
capability of this process compared to other coating application
methods.
[0014] The particular HVOF thermal spray parameters will vary
depending on numerous factors, including, but not limited to: the
type of spray gun or system used, the type and size of powder
employed, the fuel gas type, and the configuration of counterface
10. In an exemplary embodiment, coating 12 is sprayed onto surface
14 using a Sulzer Metco Diamond Jet Hybrid HVOF spray system with
hydrogen as the fuel gas and a standard nozzle designed for
hydrogen-oxygen combustion. Although hydrogen is described as the
fuel gas used, kerosene or propylene may also be used as the fuel
gas in other HVOF systems. In other alternate embodiments, the
parameters may be modified for use with other HVOF systems and
techniques using other fuels. A cooling gas, or shroud gas, may
also used to in the HVOF process to help maintain the temperature
of the process. In an exemplary embodiment, the flow rate of
hydrogen fuel gas is between approximately 661 liters per minute
(1400 cubic feet per hour at standard conditions (scfh)) and
approximately 755 liters per minute (1600 scfh) and the flow rate
of oxygen fuel gas is between approximately 189 liters per minute
(400 scfh) and approximately 283 liters per minute (600 scfh). In
an exemplary embodiment, the cooling/shroud gas is air and has a
flow rate of between approximately 283 liters per minute (600 scfh)
and approximately 425 liters per minute (900 scfh). Standard
conditions are defined as approximately 25 degrees Celsius and
approximately 1 atmosphere of pressure.
[0015] The composition of coating 12 in powder form is fed into the
spray gun at a rate of between approximately 45 grams per minute
and approximately 90 grams per minute. A nitrogen carrier gas in
the spray gun has a flow rate of between approximately 11.8 liters
per minute (25 scfh) and approximately 16.5 liters per minute (35
scfh) to provide adequate particle injection of the powder or
powder alloy into the plume centerline of the HVOF system. The
powder composition of coating 12 that is fed into the spray gun is
heated to a temperature of between approximately 1371 degrees
Celsius (2500 degrees Fahrenheit) and approximately 2204 degrees
Celsius (4000 degrees Fahrenheit) and at a velocity of between
approximately 305 meters per second (1000 feet per second) and
approximately 915 meters per second (3000 feet per second) in the
HVOF jet.
[0016] During spray deposition of coating 12, counterface 10 is
rotated to produce surface speeds of between approximately 61
meters per minute (200 surface feet per minute (sfpm)) and
approximately 122 meters per minute (400 sfpm). The spray gun is
typically located at an outer diameter of counterface 10 and
traverses in a horizontal plane across surface 14 of counterface 10
at a speed of between approximately 20.3 centimeters per minute (8
inches per minute) and approximately 101.6 centimeters per minute
(40 inches per minute) and at an angle of between approximately 45
degrees and approximately 90 degrees from surface 14. In an
exemplary embodiment, the spray gun is oriented at approximately 90
degrees from surface 14. While spraying coating 12 onto surface 14,
the spray gun is positioned between approximately 23 centimeters (9
inches) and approximately 30.5 centimeters (12 inches) from surface
14 of counterface 10. Generally, the temperature of counterface 10
when coating 12 is being sprayed onto surface 14 is affected by
factors including, but not limited to: the rotation speed of
counterface 10, the surface speed, the gun traverse rate, and the
size of counterface 10. To help control the temperature of
counterface 10, external gas may be utilized to cool counterface
10.
[0017] Upon impact with surface 10, the composition solidifies,
shrinks, and flattens against surface 10 to form coating 12.
Depositing the composition in this manner allows a repeatable
coating 12 with an optimized lamellar microstructure. In an
exemplary embodiment, coating 12 has a predominantly lamellar splat
structure with isolated regions of cuboidal carbide phases such
that coating 12 is a discrete mixture of (1) cuboidal Cr3C2
carbides; (2) precipitated matrix carbides, predominately lamellar,
of the form CrxCy, where x=7 to 23 and y=3 to 6; (3) fine lamellar
nickel oxides; and (4) a fine lamellar Ni--Cr binder. Coating 12
has a maximum porosity of approximately 3%, a nominal oxide level
of between approximately 10% and approximately 20%, and a
microhardness of between approximately 850 Vickers Hardness (HV)
and approximately 1150 HV. In an exemplary embodiment, coating 12
is applied onto surface 10 to a thickness of between approximately
203 microns (0.008 inches) and approximately 762 microns (0.03
inches). Preferably, coating 12 is applied onto surface 10 to a
thickness of between approximately 254 microns (0.01 inches) and
approximately 508 microns (0.02 inches). Coating 12 is then
finished to a thickness of between approximately 76 microns (0.003
inches) and approximately 380 microns (0.015 inches).
[0018] FIG. 2 is a diagram of a method of applying the
wear-resistant coating onto a surface of a carbon seal counterface
100. In an exemplary embodiment, the powder may be a mechanical
blend of between approximately 75% and approximately 85% by weight
chromium carbide and approximately 15% and approximately 25% by
weight nickel chromium to form a chromium carbide-nickel chromium
mixture, Box 102. In an exemplary embodiment, the chromium carbide
particles and the nickel chromium particles have an average
particle size of approximately 30 microns. The chromium
carbide-nickel chromium blended mixture is then injected into the
HVOF gun and heated to between approximately 1371 degrees Celsius
and approximately 2204 degrees Celsius. As shown in Box 104, while
the chromium carbide-nickel chromium blended mixture is being
heated, it is simultaneously accelerated at a velocity of between
305 meters per second and approximately 915 meters per second in
the HVOF jet. Upon impact with surface 10, the chromium
carbide-nickel chromium mixture solidifies, shrinks, and flattens
to form coating 12. In an exemplary embodiment, the chromium
carbide-nickel chromium mixture is fed into the spray gun at a rate
of between 45 grams per minute and approximately 90 grams per
minute. A nitrogen carrier gas in the spray gun has a flow rate of
between approximately 11.8 liters per minute (25 scfh) and
approximately 16.5 liters per minute (35 scfh). Oxygen has a flow
rate of between approximately 189 liters per minute (400 scfh) and
approximately 283 liters per minute (600 scfh), and hydrogen has a
flow rate of between approximately 661 liters per minute (1400
scfh) and approximately 755 liters per minute (1600) scfh. The
cooling gas is air and has a flow rate of between approximately 283
liters per minute (600 scfh) and approximately 425 liters per
minute (900 scfh).
[0019] The wear-resistant coating of the present invention has many
uses, such as being used in conjunction with carbon seals, rotating
shaft journal surfaces, brush seal land surfaces, and other such
similar surfaces as are typically found in gas turbine engines and
other rotating turbo-machinery. In other embodiments, the present
invention is, however, applicable to other surfaces subject to
sliding, abrasive, erosive or fretting wear, particularly for
surfaces operating continuously in environments above 900.degree.
F. (.about.482.2.degree. C.). The coating is typically sprayed by
high velocity oxygen fuel onto a counterface that is positioned
adjacent a mating surface formed of a carbon source. The coating
has a composition consisting essentially of chromium carbide and
nickel chromium. Proper manipulation of the spray parameters
results in the coating exhibiting particular phase distribution,
morphology, oxide level, porosity, and micro-hardness. These
properties enhance carbon seal or other wear system, performance by
reducing thermally-induced cracking or spallation, reducing wear in
mating surface, improving limits in coating build-up, and
increasing repair applicability.
[0020] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *