U.S. patent application number 15/996929 was filed with the patent office on 2018-10-04 for hybrid thermal barrier coating and process of making same.
This patent application is currently assigned to United Technologies Corporation. The applicant listed for this patent is United Technologies Corporation. Invention is credited to Brian T. Hazel, David A. Litton, Michael J. Maloney.
Application Number | 20180282853 15/996929 |
Document ID | / |
Family ID | 51537485 |
Filed Date | 2018-10-04 |
United States Patent
Application |
20180282853 |
Kind Code |
A1 |
Hazel; Brian T. ; et
al. |
October 4, 2018 |
Hybrid Thermal Barrier Coating and Process of Making Same
Abstract
A thermal barrier coating is applied to a turbine engine
component having a substrate. The thermal barrier coating has a
first layer which has a strain tolerant columnar microstructure at
an interface with the substrate for spallation resistance and a
second layer which is porous conduction and radiation thermally
resistant at an outer surface of the thermal barrier coating.
Inventors: |
Hazel; Brian T.; (Avon,
CT) ; Litton; David A.; (West Hartford, CT) ;
Maloney; Michael J.; (Marlborough, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Farmington |
CT |
US |
|
|
Assignee: |
United Technologies
Corporation
Farmington
CT
|
Family ID: |
51537485 |
Appl. No.: |
15/996929 |
Filed: |
June 4, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14775031 |
Sep 11, 2015 |
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PCT/US2013/078186 |
Dec 30, 2013 |
|
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15996929 |
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61781656 |
Mar 14, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 28/042 20130101;
C23C 4/134 20160101; C23C 4/11 20160101 |
International
Class: |
C23C 4/134 20060101
C23C004/134; C23C 28/04 20060101 C23C028/04; C23C 4/11 20060101
C23C004/11 |
Claims
1-7. (canceled)
8. A process for applying a thermal barrier coating to a turbine
engine component comprising: forming a first layer which has a
strain tolerant columnar microstructure at an interface of the
first layer and a substrate using a suspension plasma spray
technique; and forming a second layer which is porous and radiation
thermally resistant at an outer surface of the thermal barrier
coating using one of said suspension plasma spray technique.
9. The process of claim 8, further comprising: forming a
continuously graded microstructure from said interface to said
outer surface.
10. The process of claim 8, wherein said first layer forming step
comprises suspending a powder feedstock in a liquid suspension and
injecting said powder feedstock and said suspension into a plasma
jet under conditions where said first layer is formed with said
strain-tolerant columnar microstructure.
11. The process of claim 10, wherein said second layer forming step
comprises changing spray parameters so as to form said porous and
radiation thermally resistant second layer.
12. The process of claim 8, wherein said first and second layer
forming steps comprises forming said layers from the same
material.
13. The process of claim 8, wherein said first layer is formed from
a first material having a first composition and said second layer
is formed from a second material having a second composition which
is different from said first composition.
14. (canceled)
15. The process of claim 8, wherein said second layer forming step
comprises forming said second layer so as to have a porosity of
from 10 to 40%.
16. The process of claim 8, wherein said second layer forming step
comprises forming said second layer so as to have a thermal
conductivity which is at least 10% lower than a thermal
conductivity of said first layer.
17. The process of claim 8, wherein said first and second layer
forming steps comprise using a powdered feedstock having a particle
size in the range of from 10 nm to 10 microns.
18. The process of claim 8, wherein said first and second layer
forming steps comprises using a powdered feedstock having a
particle size in the range of from 10 nm to 2.0 microns.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 14/775,031, filed Sep. 11, 2015, which is a
371 of International PCT/US2013/078186, filed Dec. 30, 2013, which
claims benefit of provisional application Ser. No. 61/781,656,
filed Mar. 14, 2013, entitled "Hybrid Thermal Barrier Coating and
Process of Making Same".
BACKGROUND
[0002] The present disclosure relates to a thermal barrier coating
for use on a turbine engine component and to a process of making
the thermal barrier coating.
[0003] A thermal barrier coating (TBC) is created to meet one or
more performance requirements including, but not limited to,
spallation life, calcia-magnesia-alumina-silicate (CMAS)
resistance, foreign object damage (FOD) resistance, erosion, and
low conductivity. A turbine barrier coating is applied to a turbine
engine component, such as a turbine blade/vane, to help the
component withstand the relatively high temperatures of its
operational environment.
[0004] TBCs are often formed using a singular coating process such
as an electron beam physical vapor deposition (EB-PVD) process. For
example, a TBC may be formed from two separate EB-PVD layers formed
from two different materials, such as 7 wt % yttria stabilized
zirconia and gadolinia stabilized zirconia in order to improve the
thermal conductivity properties of the coating. The strain-tolerant
columnar structure of an EB-PVD coating helps to increase the TBC
spallation life. A more porous TBC however may minimize the TBC
thermal conductivity and possibly the thermal radiation through the
coating.
[0005] In one TBC, there is a porous outer layer over a more dense
inner layer made by an EB-PVD process. In some TBCs, the two layers
have different porosity levels. Such a structure can be formed by
changing the coating temperature. More power equals more density
but also more temperature. It is also known to form a dense
vertically cracked microstructure for the TBC where the deposition
is conducted at a two inch stand-off for the dense layer and a six
inch stand-off for the porous layer.
SUMMARY
[0006] In accordance with the present disclosure, there is provided
a thermal barrier coating which is applied to a turbine engine
component having a substrate, which thermal barrier coating broadly
comprises a first layer which has a strain tolerant columnar
microstructure at an interface with the substrate for spallation
resistance and a second layer which is porous conduction and
radiation thermally resistant at an outer surface of the thermal
barrier coating.
[0007] In another and alternative embodiment, the first and second
layers are formed from the same material.
[0008] In another and alternative embodiment, the first and second
layers are formed from different compositions.
[0009] In another and alternative embodiment, the second layer has
a porosity in the range of from 10 to 40%.
[0010] In another and alternative embodiment, each of the first and
second layers is formed from 7 wt % yttria stabilized zirconia.
[0011] In another and alternative embodiment, the first layer is
formed from 7 wt % yttria stabilized zirconia and the second layer
is formed from gadolinia stabilized zirconia.
[0012] In another and alternative embodiment, the first layer has a
first thermal conductivity and the second layer has a second
thermal conductivity which is at least 10% lower than the first
thermal conductivity.
[0013] Further in accordance with the present disclosure, there is
provided a process for applying a thermal barrier coating to a
turbine engine component which broadly comprises the steps of:
forming a first layer which has a strain tolerant columnar
microstructure at an interface of the first layer and a substrate
using a suspension plasma spray technique; and forming a second
layer which is porous and radiation thermally resistant at an outer
surface of the thermal barrier coating using one of the suspension
plasma spray technique and an air spray plasma technique.
[0014] In another and alternative embodiment, the process further
comprises forming a continuously graded microstructure from the
interface to the outer surface.
[0015] In another and alternative embodiment, the first layer
forming step comprises suspending a powder feedstock in a liquid
suspension and injecting the powder feedstock and the suspension
into a plasma jet under conditions where the first layer is formed
with the strain-tolerant columnar microstructure.
[0016] In another and alternative embodiment, the second layer
forming step comprises changing spray parameters so as to form the
porous and radiation thermally resistant second layer.
[0017] In another and alternative embodiment, the first and second
layer forming steps comprises forming the first and second layers
from the same material.
[0018] In another and alternative embodiment, the first layer is
formed from a first material having a first composition and the
second layer is formed from a second material having a second
composition which is different from the first composition.
[0019] In another and alternative embodiment, the second layer is
formed using the air spray plasma technique.
[0020] In another and alternative embodiment, the second layer
forming step comprises forming the second layer so as to have a
porosity of from 10 to 40%.
[0021] In another and alternative embodiment, the second layer
forming step comprises forming the second layer so as to have a
thermal conductivity which is at least 10% lower than a thermal
conductivity of the first layer.
[0022] In another and alternative embodiment, the first and second
layer forming steps comprise using a powdered feedstock having a
particle size in the range of from 10 nm to 10 microns.
[0023] In another and alternative embodiment, the first and second
layer forming steps comprises using a powdered feedstock having a
particle size in the range of from 10 nm to 2.0 microns.
[0024] Other details of the hybrid thermal barrier coating and the
process of making same are set forth in the following detailed
description and the accompanying drawings wherein like reference
numerals depict like elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 illustrates a turbine engine component having a
thermal barrier coating in accordance with the present disclosure
deposited thereon; and
[0026] FIG. 2 illustrates a system for forming the coating on the
turbine engine component.
DETAILED DESCRIPTION
[0027] Referring now to FIG. 1, there is shown a turbine engine
component 10. The turbine engine component may be any component
which requires a thermal barrier coating such as a blade/vane. The
turbine engine component 10 may have a substrate 12 formed from any
suitable material known in the art including, but not limited to, a
nickel based alloy, a cobalt based alloy, a titanium based alloy, a
ceramic material, and an organo-matrix composite material.
[0028] A thermal barrier coating 14 may be deposited on the
substrate 12. The thermal barrier coating 14 may have a first layer
16 which interfaces with the surface 18 of the substrate 12 and an
outer second layer 20. The first layer 16 may be formed so as to
have a strain-tolerant columnar microstructure at the interface
with the surface 18 of the substrate. The second layer 20 may be
formed to have a porous thermal conduction and radiant heat
transfer resistant microstructure at an outer surface 22 of the
thermal barrier coating.
[0029] The first layer 16 and the second layer 20 may formed from a
material having the same composition. For example, each of the
layers 16 and 20 may be formed from a 7 wt % yttria stabilized
zirconia (7YSZ). In another embodiment, the first layer 16 may be
formed from a first material having a first composition and the
second layer 20 may be formed from a second material having a
second composition which is different from the first composition.
For example, the first layer 16 may be formed from 7YSZ, while the
second layer 20 is formed from gadolinia stabilized zirconia.
[0030] Each of the layers 16 and 20 may be formed using suspension
plasma spray (SPS) technique such as that shown in FIG. 2. In this
technique, a powdered feedstock is suspended in a liquid suspension
30. For example, the powdered feedstock may be 7YSZ which may be
suspended in ethanol, water, or other alcohols such as methanol.
The powdered feedstock may have a particle size in the range of
from 10 nm to 10 microns mean size diameter. In another
non-limiting embodiment, the particles size may be in the range of
from 10 nm to 2.0 microns. The powdered feedstock in the suspension
is injected into a plasma jet 32 created by a plasma torch 34 and
thus deposited onto the substrate 12. The spray conditions are such
that the first layer 16 is formed to have the desired strain
tolerant columnar microstructure. The deposition technique may have
a short stand off (similar to that used in dense vertically cracked
coatings) and high power/enthalpy plasma conditions. After the
first layer 16 has been formed, the spray conditions may be changed
so as to form the second layer 20 with the porous thermal
conduction and radiant heat transfer resistant microstructure. To
add porosity, (1) the angle of the spray nozzle could be changed
from normal relative to the surface on which the layer 20 is being
deposited; (2) the stand off may be increased; and/or (3) the
plasma power/enthalpy may be reduced. More porosity in the second
layer 20 than in the first layer 16 creates a reduction in thermal
conductivity. The second layer 20 may have a reduction of at least
10% in thermal conductivity. This may come purely from a porosity
increase or a change in the structure from columnar to more splat
like. An increase in porosity increases the erosion rate. A useful
limit may be 10 to 40% porosity in the second layer 20.
[0031] The columnar structure SPS gives a thermal cyclic spallation
resistance similar to EB-PVD (much higher than APS and higher than
dense vertically cracked). Erosion is a function of porosity
content and can be greater or less than EB-PVD (generally higher
than APS and more like dense vertically cracked). Thermal
conductivity, as discussed above, follows the porosity content.
[0032] If desired, the spray conditions may be discreetly or
incrementally changed throughout the spray run. For example, the
spray conditions may be changed so that a continuously graded
microstructure is formed where there is the strain-tolerant
columnar microstructure at the interface with the substrate 12 for
thermal barrier coating spallation resistance and a porous thermal
conduction and radiation thermally resistant layer at the outer
surface 22.
[0033] If desired, the first layer 16 may be formed using the above
discussed SPS technique and the second layer 20 may be formed using
a porous air plasma spray (APS) technique.
[0034] One of the advantages of the process described herein is
that the thermal barrier coating can be formed using a single piece
of equipment and in a single coating run.
[0035] Another advantage is that one can easily change the
composition of the second layer 20 so that it is different than the
composition of the first layer 16. This can easily be done by
changing the composition of the feedstock being injected into the
plasma jet.
[0036] There has been described herein a hybrid thermal barrier
coating and a process for making same. While the coating and
process have been described in the context of specific embodiments
thereof, other unforeseen alternatives, modifications, and
variations may become apparent to those skilled in the art having
read the foregoing description. Accordingly, it is intended to
embrace those alternatives, modifications, and variations as fall
within the broad scope of the appended claims.
* * * * *