U.S. patent application number 12/978931 was filed with the patent office on 2012-06-28 for high-temperature jointed assemblies and wear-resistant coating systems therefor.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Robert William Bruce, Danny Lee Fenwick, Karen Marie Marvich.
Application Number | 20120160348 12/978931 |
Document ID | / |
Family ID | 45464248 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120160348 |
Kind Code |
A1 |
Bruce; Robert William ; et
al. |
June 28, 2012 |
HIGH-TEMPERATURE JOINTED ASSEMBLIES AND WEAR-RESISTANT COATING
SYSTEMS THEREFOR
Abstract
Wear-resistant coating systems suitable for protecting surfaces
subjected to contact wear at high temperatures, such as surfaces of
an assembly comprising high-temperature components of gas turbine
engines. The components have surfaces in wear contact with each
other. One of the surfaces has a wear-resistant coating system
thereon so as to be in wear contact with the surface of the other
component. The wear-resistant coating system contains alternating
layers of TiAlN and CrN.
Inventors: |
Bruce; Robert William;
(Loveland, OH) ; Marvich; Karen Marie; (West
Chester, OH) ; Fenwick; Danny Lee; (Lebanon,
OH) |
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
45464248 |
Appl. No.: |
12/978931 |
Filed: |
December 27, 2010 |
Current U.S.
Class: |
137/527 ;
427/255.7; 428/101; 428/336; 428/457; 428/66.7; 428/697 |
Current CPC
Class: |
C23C 28/044 20130101;
C23C 14/0641 20130101; Y10T 137/7903 20150401; Y10T 428/219
20150115; Y10T 428/265 20150115; Y10T 137/7036 20150401; Y10T
137/7898 20150401; Y10T 428/31678 20150401; Y10T 428/24025
20150115; Y10T 428/12493 20150115; C23C 28/42 20130101; Y10T
428/12847 20150115 |
Class at
Publication: |
137/527 ;
428/697; 428/336; 428/101; 428/457; 428/66.7; 427/255.7 |
International
Class: |
F16K 15/00 20060101
F16K015/00; C23C 16/00 20060101 C23C016/00; B32B 3/02 20060101
B32B003/02; B32B 15/04 20060101 B32B015/04; B32B 9/04 20060101
B32B009/04 |
Claims
1. An assembly comprising first and second components having
surfaces in wear contact with each other, one of the surfaces
having a wear-resistant coating system thereon so as to be in wear
contact with the surface of the other component, the wear-resistant
coating system consisting of alternating layers of TiAlN and
CrN.
2. The assembly according to claim 1, wherein individual layers of
TiAlN have a thickness of at least 0.2 micrometers and up to about
0.8 micrometer.
3. The assembly according to claim 1, wherein individual layers of
TiAlN have a thickness of about 0.3 to about 0.5 micrometer.
4. The assembly according to claim 1, wherein individual layers of
CrN have a thickness of at least 0.2 micrometers and up to about
0.8 micrometer.
5. The assembly according to claim 1, wherein individual layers of
CrN have a thickness of about 0.3 to about 0.5 micrometer.
6. The assembly according to claim 1, wherein the wear-resistant
coating system has a thickness of at least 6 micrometers.
7. The assembly according to claim 1, wherein the wear-resistant
coating system has a thickness of up to about 80 micrometers.
8. The assembly according to claim 1, wherein the wear-resistant
coating system has a thickness of about 30 to about 50
micrometers.
9. The assembly according to claim 1, wherein the first and second
components define a pivot joint, the first component defines a
pivot axis, and the second component is pivotably coupled to the
first component so as to pivot about the pivot axis of the first
component.
10. The assembly according to claim 1, wherein the first component
is formed of a cobalt-base alloy, and the second component is
formed of either a solid solution-strengthened nickel-based alloy
or a chromium-containing martensitic stainless steel.
11. The assembly according to claim 10, wherein the cobalt-base
alloy has a nominal composition of, by weight, about 20.0%
chromium, about 10.0% nickel, about 15.0% tungsten, about and 0.5%
carbon, with the balance cobalt and incidental impurities.
12. The assembly according to claim 10, wherein the second
component is formed of the solid solution-strengthened nickel-based
alloy and has a nominal composition of, by weight, about 21.5%
chromium, about 9.0% molybdenum, about 3.6% niobium, about 2.5%
iron, about 0.2% aluminum, about 0.2% titanium, about 0.2%
manganese, about 0.2% silicon, about 0.05% carbon, with the balance
nickel and incidental impurities.
13. The assembly according to claim 10, wherein the second
component is formed of the chromium-containing martensitic
stainless steel and has a nominal composition of, by weight, about
2.5% nickel, about 12% chromium, about 1.7% molybdenum, about 0.3%
vanadium, about 0.12% carbon, with the balance iron and incidental
impurities.
14. The assembly according to claim 1, wherein the wear-resistant
coating system is present on the surface of the first component and
the surface thereof is cylindrical in shape.
15. The assembly according to claim 1, wherein the assembly is a
flapper valve assembly, the first component is a hinge pin, and the
second component is a flapper valve.
16. The assembly according to claim 15, wherein the flapper valve
assembly is installed in a gas turbine engine.
17. The assembly according to claim 16, wherein the flapper valve
assembly is installed to control cooling air flow to air-cooled
components of the gas turbine engine.
18. A method of forming the assembly of claim 1, the method
comprising depositing the layers of TiAlN and CrN by a physical
vapor deposition process.
19. A flapper valve assembly installed in a gas turbine engine to
control cooling air flow to air-cooled components of the gas
turbine engine, the flapper valve assembly comprising a pivot joint
defined by a hinge pin that defines a pivot axis and a flapper
valve pivotably coupled to the hinge pin so as to pivot about the
pivot axis of the hinge pin, the hinge pin and the flapper valve
having surfaces in wear contact with each other, the hinge pin
being formed of a cobalt-based alloy, the flapper valve being
formed of either a solid solution-strengthened nickel-based alloy
or a chromium-containing martensitic stainless steel, the surface
of the hinge pin having a wear-resistant coating system thereon so
as to be in wear contact with the surface of the flapper valve, the
wear-resistant coating system consisting of alternating layers of
TiAlN and CrN, individual layers of TiAlN having a thickness of
about 0.3 to about 0.5 micrometers, individual layers of CrN having
a thickness of about 0.3 to about 0.5 micrometers, and the
wear-resistant coating system having a thickness of about 30 to
about 50 micrometers.
20. A method of forming the assembly of claim 19, the method
comprising depositing the layers of TiAlN and CrN by a physical
vapor deposition process.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to components and
materials suitable for use in high temperature applications, such
as gas turbine engines. More particularly, this invention is
directed to assemblies with joints subjected to high temperatures
and wear-resistant coating systems for such joints.
[0002] Higher operating temperatures for gas turbine engines are
continuously sought in order to increase their efficiency.
Significant advances in high temperature capabilities have been
achieved through the formulation of iron, nickel and cobalt-base
superalloys, whose high temperature properties enable components to
withstand long exposures to operating temperatures within the
compressor, turbine, combustor and augmentor sections of
high-performance gas turbine engines. Certain components that
require attachment with articulating joints create design
challenges in view of the high temperatures, vibration and
corrosive environment within a gas turbine engine. For example,
pins, trunnions and other components employed to pivotably secure
other components must have physical properties that are compatible
with adjacent components and exhibit resistance to contact wear and
corrosion over long durations at high temperatures.
[0003] FIG. 1 schematically represents an assembly 10 comprising an
articulating joint defined by a pin 12 that pivotably supports a
component 14 (represented in cross-section) to allow the component
14 to pivot about the axis of the pin 12. As an example, the pin 12
may be a hinge pin for a flapper valve, such as of the type used in
gas turbine engines to regulate the cooling air flow to air-cooled
turbine components. The diametric clearance between the pin 12 and
component 14 is exaggerated for purposes of illustration. As
schematically represented in FIG. 1, the shank 16 of the pin 12 has
been severely worn as a result of the pivoting motion and vibration
of the component 14 relative to the pin 12. Wear has primarily
occurred on the shank 16 of the pin 12, though it is foreseeable
that the inverse situation could exist. Localized damage to the
wear surfaces of the pin 12 and component 14 can be accelerated by
the effects of corrosion within the hostile environment of the
turbine engine.
[0004] In one particular application, flapper valves formed of the
nickel-base alloy Inconel (IN) 625 (nominal composition of, by
weight, about 21.5% chromium, about 9.0% molybdenum, about 3.6%
niobium 2.5% iron, about 0.2% aluminum, about 0.2% titanium, about
0.2% manganese, about 0.2% silicon, about 0.05% carbon, the balance
nickel and incidental impurities) have been observed to rapidly
wear when secured with a hinge formed of the cobalt-base alloy
L-605 (HA25) (nominal composition of, by weight, about 20.0%
chromium, about 10.0% nickel, about 15.0% tungsten, and about 0.5%
carbon, the balance cobalt and incidental impurities). Though this
combination of materials has been very reliable in gas turbine
engine applications, more severe operating conditions have lead to
more rapid wear rates, while simultaneously a longer wear life has
been sought for the assembly.
[0005] A wide variety of coating materials are known and widely
used to protect components of gas turbine engines, including hard
impact and erosion-resistant coating materials such as nitrides and
carbides. For example, see U.S. Pat. No. 4,904,528 to Gupta et al.
(titanium nitride (TiN) coatings), U.S. Pat. No. 4,839,245 to Sue
et al. (zirconium nitride (ZrN) coatings), U.S. Pat. No. 4,741,975
to Naik et al. (tungsten carbide (WC) and tungsten carbide/tungsten
(WC/W) coatings), U.S. Pat. No. 7,186,092 to Bruce et al.
(combinations of tantalum carbide (TaC), niobium carbide (NbC),
titanium carbide (TiC), titanium aluminum chromium carbide
(TiAlCrC), titanium aluminum chromium nitride (TiAlCrN), titanium
aluminum nitride (TiAlN), titanium aluminum carbide (TiAlC), and
boron carbide (B.sub.4C)) and U.S. Published Patent Application
Nos. 2009/0011195 and 2010/0078308 to Bruce et al. (combinations of
TiAlN, chromium nitride (CrN) and titanium silicon carbonitride
(TiSiCN)). However, these coating materials are primarily intended
to promote the impact and erosion resistance of blades, as opposed
to surfaces continuously subjected to contact wear.
[0006] Wear-resistant coatings intended for surfaces subject to
contact wear have also been proposed for use in the
high-temperature environment of gas turbine engines. Examples
include thermal sprayed coatings of chromium carbide and
Co--Mo--Cr--Si alloys, such as the commercially-available
TRIBALOY.RTM. T400 and T800 alloys. These wear-resistant materials
have also been applied as foils, as taught in U.S. Pat. No.
6,398,103 to Hasz et al. Nonetheless, there is an ongoing need for
improved material combinations that would enable pivot joint
assemblies to exhibit longer service lives in the hostile
environment of a gas turbine engine.
BRIEF DESCRIPTION OF THE INVENTION
[0007] The present invention provides wear-resistant coatings
suitable for protecting surfaces subjected to contact wear at high
temperatures, such as surfaces of articulating joints formed by
high-temperature components of gas turbine engines.
[0008] According to one aspect of the invention, an assembly is
provided comprising first and second components having surfaces in
wear contact with each other. One of the surfaces has a
wear-resistant coating system thereon so as to be in wear contact
with the surface of the other component. The wear-resistant coating
system consists of alternating layers of TiAlN and CrN.
[0009] Another aspect of the invention is a method of forming the
assembly described above by depositing the alternating layers of
TiAlN and CrN using a physical vapor deposition process.
[0010] Another aspect of the invention is that the assembly
comprises a pivot joint defined by the first and second components,
in which the first component defines a pivot axis and the second
component is pivotably coupled to the first component so as to
pivot about the pivot axis of the first component.
[0011] A technical effect of the invention is the ability to
significantly improve the wear resistance of surfaces in wear
contact at high temperatures. The invention is capable of reducing
wear by a factor of nearly 50.times. based on the use of the same
base materials for the first and second components. Further
improvements can be achieved through the use of different
combinations of base materials.
[0012] Other aspects and advantages of this invention will be
better appreciated from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 represents a fragmentary cross-sectional view of an
assembly comprising two components that form a pivot joint, wherein
the joint has become worn as a result of pivot motion and
vibration.
[0014] FIG. 2 represents a fragmentary cross-sectional view of an
assembly similar to FIG. 1, wherein one of the components has been
provided with a wear-resistant coating system in accordance with an
embodiment of the invention.
[0015] FIG. 3 is a scanned image of a wear-resistant coating system
in accordance with an embodiment of the present invention.
[0016] FIGS. 4 through 7 are bar graphs representing data from
comparative wear tests performed on coating compositions, including
wear-resistant coating systems of this invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] FIG. 2 represents an assembly 20 that is similar to what is
represented in FIG. 1, in that two components 22 and 24 are
represented as being pivotably coupled together to define a pivot
joint. In a particular embodiment, and for purposes of discussing
the invention, the first and second components 22 and 24 are,
respectively, a hinge pin 22 and flapper valve 24, such as a
flapper valve used to regulate the cooling air flow to air-cooled
components of a turbine engine, though other applications are
foreseeable and also within the scope of the invention. In such an
application, the pin 22 pivotably supports the flapper valve 24 to
allow the valve 24 to pivot about the axis of the pin 22. In
contrast to the severely worn shank 16 of FIG. 1, the
cylindrical-shaped shank 26 of the pin 22 is schematically
represented in cross-section as provided with a coating system 30
that overlies the base material 28 of the pin 22. According to a
preferred aspect of the invention, the coating system 30 is
resistant to wear resulting from contact between the pin 22 and
valve 24, including severe wear conditions that can result from
high temperatures and vibration within the operating environment of
a gas turbine engine. The coating system 30 is shown as being
applied to only the shank 26 of the pin 22, though it should be
understood that the coating system 30 could be deposited on the
opposing surface 32 of the valve 24. It should be noted that the
diametric clearance between the pin 22 and valve 24 is exaggerated
in FIG. 2 for purposes of illustration. Diametric clearances for
flapper valve applications within gas turbine engines will
typically range from about 75 to about 300 micrometers, and the
contact between the shank 26 and the opposing surface 32 of the
valve 24 will typically range from about 10 to about 300
millimeters along the axial length of the shank 26, though lesser
and greater clearances and contact lengths are also within the
scope of the invention.
[0018] As previously discussed in reference to FIG. 1, in one
particular application for assemblies of the type represented in
FIG. 2, the flapper valve 24 is formed of the nickel-base alloy
Inconel (IN) 625, and the hinge pin 22 is formed of the cobalt-base
alloy L-605. Because this combination of materials has exhibited
high wear rates at increasingly severe engine operating conditions,
the coating system 30 of this invention serves to reduce wear and
promote a longer life for the assembly 20.
[0019] In preferred embodiments of the invention, the coating
system 30 contains multiple layers of ceramic materials, and more
particularly multiple layers of titanium aluminum nitride (TiAlN)
and chromium nitride (CrN) in combination (for example, alternating
layers) without any intervening ceramic or metallic layers
therebetween. An example of a TiAlN--CrN coating system 30 is shown
in FIG. 3, with individual alternating layers of TiAlN and CrN
being visible as alternating light and dark layers, respectively.
Each individual layer of the coating system 30 has a thickness of
at least 0.20 micrometers and a maximum thickness of about 0.80
micrometers, with a suitable range being about 0.30 to about 0.50
micrometers. The thicknesses of the TiAlN and CrN layers are
preferably the same, though it is foreseeable that the TiAlN or CrN
layers could be deposited to be intentionally thicker than the
other. The individual layers are deposited in appropriate numbers
and thicknesses to obtain the desired thickness for the coating
system 30. The entire coating system 30 preferably has a thickness
of at least 6 micrometers, for example, about 30 to about 50
micrometers. Coating thicknesses exceeding 80 micrometers are
believed to be unnecessary in terms of wear resistance. A bond coat
(not shown) may be used to promote the adhesion of the coating
system 30 to the base material 28 of the pin 22. The bond coat may
be made up of one or more metal layers, for example, one or more
layers of titanium.
[0020] Coatings of this invention are preferably deposited by a
physical vapor deposition (PVD) technique, and therefore will
generally have a columnar and/or dense microstructure, as opposed
to the noncolumnar, irregular, and porous microstructure that would
result if the coating were deposited by a thermal spray process.
Particularly suitable PVD processes include EB-PVD, cathodic arc
PVD, and sputtering, with cathodic arc believed to be preferred.
Suitable sputtering techniques include but are not limited to
direct current diode sputtering, radio frequency sputtering, ion
beam sputtering, reactive sputtering, magnetron sputtering,
plasma-enhanced magnetron sputtering, and steered arc sputtering.
Cathodic arc PVD and plasma-enhanced magnetron sputtering are
particularly preferred for producing coatings due to their high
coating rates. Deposition can be carried out in an atmosphere
containing a source of nitrogen (for example, nitrogen gas) to form
the nitride constituents of the deposited coating system 30. Any
metallic bond coat employed with the coating system 30 is
preferably deposited in an inert atmosphere, for example,
argon.
[0021] The coating system 30 preferably has a surface roughness of
about 50 microinches (about 1.2 micrometers) Ra or less. The base
material 28 of the pin 22 and/or the coating system 30 may undergo
polishing to achieve this surface finish. Polishing of the base
material 28 can be performed before coating deposition to promote
the deposition of a smooth coating system 30, with additional
polishing performed after coating deposition to ensure that the
desired coating surface roughness is obtained. Polishing can also
be performed as an intermediate step of the coating process.
[0022] In a preliminary investigation leading to the present
invention, wear tests were conducted on specimens at test
temperatures of about 75.degree. F., 400.degree. F. and 750.degree.
F. (about 75.degree. C., 200.degree. C. and 400.degree. C.). The
wear tests were reciprocating sliding wear tests utilizing a
contact zone of about 25.times.3.75 mm, with the sliding motion
occurring over a distance of about 1.5 mm in a direction parallel
to the smaller dimension of the contact zone. The test specimens
were formed of titanium, steel, nickel and aluminum alloys,
including M-152, Alloy 17-4PH, A-286, IN-718, Nitronic 60.RTM., and
Aluminum 2219. The evaluated coatings included five nitride
coatings: TiN, TiAlN, TiSiCN, alternating layers of TiAlN and CrN,
and alternating layers of TiSiAlN and CrN. For comparison,
additional test specimens were coated with WC/Co cermet and
TRIBALOY T400, the latter being a cobalt-based hardface alloy
available from Deloro Stellite Inc. Though well known as being
excellent wear-resistant coating materials, the WC/Co and TRIBALOY
T400 coatings were not deemed to be acceptable candidates for the
flapper valve and similar applications since they would be
deposited by HVOF, rendering these coatings difficult to deposit on
a small diameter pin, and would require expensive surface
treatments to achieve the surface finish desired for the flapper
valve. Of the experimental coating compositions, the coatings
formed of alternating layers of TiAlN and CrN performed the best,
and exhibited wear resistance approaching that of WC/Co.
[0023] Based on the results of the preliminary investigation, a
second investigation was conducted with coatings formed of
alternating layers of TiAlN and CrN. FIGS. 4 through 7 contain
graphs summarizing data obtained with the second investigation.
Evaluated test specimens were configured to comprise an anvil and
striker. The wear tests utilized a contact surface of about
4.times.12 mm on the anvil, with initial motion of the striker and
impact occurring in a direction perpendicular to the contact
surface of the anvil, followed by a sliding motion of the striker
in the length direction of the contact surface. The test was
performed with a load of about 2.5 ksi (about 17 MPa), a stroke of
about 17 mils (about 0.43 mm) and a frequency of about 35 Hz. All
test specimens were evaluated in a rig supplied with air heated to
about 800.degree. F. (about 425.degree. C.) to obtain a specimen
temperature of about 650.degree. F. (about 345.degree. C.).
[0024] Along with baseline specimens, two sets of uncoated
specimens were evaluated along with four sets of coated specimens.
The baseline specimens employed an anvil formed of IN-625 and a
striker formed of L-605 which, as noted above, are valve and pin
materials for a flapper valve assembly currently used in an
existing gas turbine engine application. For one of the sets of
uncoated specimens, both the anvil and striker were formed of
L-605. For the second set of uncoated specimens, both the anvil and
striker were formed of Stellite 6B (Haynes 6B), a cobalt-based
alloy available from Deloro Stellite Inc., and having a nominal
composition of, by weight, 3.0% nickel, 30.0% chromium, 1.0% iron,
1.0% carbon, 1.4% manganese, 1.5% molybdenum, 4.0% tungsten, the
balance cobalt and incidental impurities. Four coating systems
containing alternating layers of TiAlN and CrN were evaluated with
four different anvil-striker combinations: an M-152 anvil and L-605
striker, an IN-625 anvil and L-605 striker, an L-605 anvil and
L-605 striker, and a Stellite 6B anvil and L-605 striker. The
coating system was deposited by PVD on the strikers to thicknesses
of about 50 micrometers, and contained layers of TiAlN having
thicknesses of about 0.5 micrometer and layers of CrN having
thicknesses of about 0.5 micrometer.
[0025] FIGS. 4 and 5 plot the deepest pit and average wear results
for the baseline and uncoated specimens as well as the TiAlN--CrN
coated specimens. FIGS. 6 and 7 plot the pit and average wear
results for only the nitride test specimens. All results are
normalized to 100,000 cycles. From these results, it can be seen
that the specimens combining an M-152 anvil and coated L-605
striker performed the best, and the specimens combining an IN-625
anvil and coated L-605 striker also performed extremely well. The
specimens with the M-152 anvil and coated L-605 striker exhibited
an average wear of nearly 100.times. less than the baseline IN-625
anvil and uncoated L-605 striker, and the specimens combining the
IN-625 anvil and coated L-605 striker exhibited an average wear of
nearly 50.times. less than the baseline IN-625 anvil and uncoated
L-605 striker.
[0026] From these results, it was concluded that the TiAlN--CrN
coating system performed very well when applied to a base material
of the cobalt-based L-605 alloy and subjected to wear from a member
formed of IN-625 or M-152. As such, the invention encompasses
assemblies (including flapper valve assemblies) in which components
formed of L-605 and either IN-625 or M-152 are in wear contact with
each other at elevated temperatures, and particularly operating
temperatures of about 425.degree. C. and higher. L-605 is a
cobalt-base alloy L-605 having a nominal composition of, by weight,
about 20.0% chromium, about 10.0% nickel, about 15.0% tungsten,
about and 0.5% carbon, with the balance cobalt and incidental
impurities. It is believed that similar results could be expected
if the pin 22 were to be formed of a similar cobalt-base alloy.
IN-625 is a solid solution-strengthened nickel-based alloy having a
nominal composition of, by weight, about 21.5% chromium, about 9.0%
molybdenum, about 3.6% niobium, about 2.5% iron, about 0.2%
aluminum, about 0.2% titanium, about 0.2% manganese, about 0.2%
silicon, about 0.05% carbon, with the balance nickel and incidental
impurities. M-152 is a chromium-containing martensitic stainless
steel alloy having a nominal composition of, by weight, about 2.5%
nickel, about 12% chromium, about 1.7% molybdenum, about 0.3%
vanadium, about 0.12% carbon, with the balance iron and incidental
impurities. It is believed that similar results could be expected
if the flapper valve 24 were to be formed of a solid
solution-strengthened nickel-based alloy similar to IN-625 or a
chromium-containing martensitic stainless steel similar to M-152.
Because M-152 is typically available as forging or castings
produced by centrifugal casting techniques, IN-625 is believed to
be a more practical material for applications such as the flapper
valve assembly of FIG. 2.
[0027] While the invention has been described in terms of specific
embodiments, it is apparent that other forms could be adopted by
one skilled in the art. Therefore, the scope of the invention is to
be limited only by the following claims.
* * * * *