U.S. patent application number 16/804437 was filed with the patent office on 2020-09-03 for thermal spray deposited environmental barrier coating.
The applicant listed for this patent is Rolls-Royce Corporation, Rolls-Royce High Temperature Composites, Inc., Rolls-Royce North American Technologies, Inc.. Invention is credited to Ann Bolcavage, Matthew R. Gold, Bradley Wing.
Application Number | 20200277694 16/804437 |
Document ID | / |
Family ID | 1000004732089 |
Filed Date | 2020-09-03 |
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United States Patent
Application |
20200277694 |
Kind Code |
A1 |
Bolcavage; Ann ; et
al. |
September 3, 2020 |
THERMAL SPRAY DEPOSITED ENVIRONMENTAL BARRIER COATING
Abstract
In one example, a method for forming an environmental barrier
coating (EBC) on a substrate. The method may include depositing an
environmental barrier coating (EBC) on a substrate via a thermal
spray apparatus to form an as-deposited EBC; heat treating the
as-deposited EBC at or above a first temperature for first period
of time following the deposition of the as-deposited EBC on the
substrate; and cooling the as-deposited EBC to a second temperature
following the heat treatment at a controlled rate over a second
period of time to form a heat-treated EBC on the substrate. The
first temperature, the first period of time, the controlled rate,
and the second period of time may be selected to increase a weight
percent of crystalline phase in the heat-treated EBC compared to
the as-deposited EBC.
Inventors: |
Bolcavage; Ann;
(Indianapolis, IN) ; Wing; Bradley; (Westminster,
CA) ; Gold; Matthew R.; (Carmel, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rolls-Royce Corporation
Rolls-Royce North American Technologies, Inc.
Rolls-Royce High Temperature Composites, Inc. |
Indianapolis
Indianapolis
Cypress |
IN
IN
CA |
US
US
US |
|
|
Family ID: |
1000004732089 |
Appl. No.: |
16/804437 |
Filed: |
February 28, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62812524 |
Mar 1, 2019 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 4/134 20160101;
C23C 4/18 20130101; C23C 4/02 20130101 |
International
Class: |
C23C 4/18 20060101
C23C004/18; C23C 4/02 20060101 C23C004/02; C23C 4/134 20060101
C23C004/134 |
Claims
1. A method comprising: depositing an environmental barrier coating
(EBC) on a substrate via a thermal spray apparatus to form an
as-deposited EBC; heat treating the as-deposited EBC at or above a
first temperature for first period of time following the deposition
of the as-deposited EBC on the substrate; and cooling the
as-deposited EBC to a second temperature following the heat
treatment at a controlled rate over a second period of time to form
a heat-treated EBC on the substrate, wherein the first temperature,
the first period of time, the controlled rate, and the second
period of time are selected to increase a weight percent of
crystalline phase in the heat-treated EBC compared to the
as-deposited EBC.
2. The method of claim 1, wherein the first temperature is about
850 degrees Celsius.
3. The method of claim 1, wherein the first temperature is about
1000 degrees Celsius to about 1200 degree Celsius.
4. The method of claim 1, wherein the controlled rate is no greater
than about 5 degrees Celsius per minute.
5. The method of claim 1, wherein the second temperature is about
500 degrees Celsius or less.
6. The method of claim 1, wherein the second period of time is
greater than about one hour.
7. The method of claim 1, wherein the heat-treated EBC includes at
least 50 weight percent crystalline phase.
8. The method of claim 1, wherein the as-deposited EBC includes
less than 50 weight percent crystalline phase.
9. The method of claim 1, further comprising, prior to depositing
the EBC on the substrate, heating the substrate to a third
temperature, wherein depositing the EBC on the substrate via the
thermal spray device comprises depositing the EBC on the substrate
via the thermal spray apparatus while the substrate is at the third
temperature.
10. The method of claim 9, wherein the third temperature is at
least about 800 degrees Celsius.
11. A system comprising: a thermal spray device configured to
deposit an environmental barrier coating (EBC) on a substrate to
form an as-deposited EBC; a furnace configured to heat the
as-deposited EBC following deposition of the as-deposited EBC by
the thermal spray device; and a computing device configured to
control the thermal spray device to deposit the EBC on the
substrate to form the as-deposited EBC, control the heat treatment
of the as-deposited EBC at or above a first temperature for a first
period of time following the deposition of the as-deposited EBC on
the substrate, and control the cooling of the as-deposited EBC to a
second temperature following the heat treatment at a controlled
rate over a second period of time, wherein the first temperature,
the first period of time, the controlled rate, and the second
period of time are selected to increase a weight percent of
crystalline phase in the heat-treated EBC compared to the
as-deposited EBC.
12. The system of claim 11, wherein the first temperature is about
850 degrees Celsius.
13. The system of claim 11, wherein the first temperature is about
1000 degrees Celsius to about 1200 degree Celsius.
14. The system of claim 11, wherein the controlled rate is no
greater than about 5 degrees Celsius per minute.
15. The system of claim 11, wherein the second temperature is about
500 degrees Celsius or less.
16. The system of claim 11, wherein the second period of time is
greater than about one hour.
17. The system of claim 11, wherein the heat-treated EBC includes
at least 50 weight percent crystalline phase.
18. The system of claim 11, wherein the as-deposited EBC includes
less than 50 weight percent crystalline phase.
19. The system of claim 11, wherein the computing device is
configured to, prior to depositing the EBC on the substrate,
control heating of the substrate to a third temperature, wherein
the EBC is deposited on the substrate via the thermal spray
apparatus while the substrate is at the third temperature.
20. The system of claim 19, wherein the third temperature is at
least about 800 degrees Celsius.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/812,524, filed Mar. 1, 2019, the entire
content of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The disclosure relates to techniques for forming
environmental barrier coatings using thermal spray deposition.
BACKGROUND
[0003] Ceramic or ceramic matrix composite (CMC) materials may be
useful in a variety of contexts where mechanical and thermal
properties are important. For example, components of high
temperature mechanical systems, such as gas turbine engines, may be
made from ceramic or CMC materials. Ceramic or CMC materials may be
resistant to high temperatures, but some ceramic or CMC materials
may react with some elements and compounds present in the operating
environment of high temperature mechanical systems, such as water
vapor. Reaction with water vapor may result in the recession of the
ceramic or CMC material. These reactions may damage the ceramic or
CMC material and reduce mechanical properties of the ceramic or CMC
material, which may reduce the useful lifetime of the component.
Thus, in some examples, a ceramic or CMC material may be coated
with an environmental barrier coating, which may reduce exposure of
the substrate to elements and compounds present in the operating
environment of high temperature mechanical systems.
SUMMARY
[0004] In some examples, the disclosure describes a method that
comprises depositing an environmental barrier coating (EBC) on a
substrate via a thermal spray apparatus to form an as-deposited
EBC; heat treating the as-deposited EBC at or above a first
temperature for first period of time following the deposition of
the as-deposited EBC on the substrate; and cooling the as-deposited
EBC to a second temperature following the heat treatment at a
controlled rate over a second period of time to form a heat-treated
EBC on the substrate, wherein the first temperature, the first
period of time, the controlled rate, and the second period of time
are selected to increase a weight percent of crystalline phase in
the heat-treated EBC compared to the as-deposited EBC
[0005] In some examples, the disclosure describes a system
comprising a thermal spray device configured to deposit an
environmental barrier coating (EBC) on a substrate to form an
as-deposited EBC; a furnace configured to heat the as-deposited EBC
following deposition of the as-deposited EBC by the thermal spray
device; and a computing device configured to control the thermal
spray device to deposit the EBC on the substrate to form the
as-deposited EBC, control the heat treatment of the as-deposited
EBC at or above a first temperature for a first period of time
following the deposition of the as-deposited EBC on the substrate,
and control the cooling of the as-deposited EBC to a second
temperature following the heat treatment at a controlled rate over
a second period of time, wherein the first temperature, the first
period of time, the controlled rate, and the second period of time
are selected to increase a weight percent of crystalline phase in
the heat-treated EBC compared to the as-deposited EBC.
[0006] The details of one or more examples are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages will be apparent from the description and
drawings, and from the claims.
BRIEF DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a conceptual and schematic diagram illustrating an
example system for forming an EBC on a substrate in accordance with
an example of the disclosure.
[0008] FIG. 2 is a conceptual block diagram illustrating an example
thermal spray device.
[0009] FIG. 3 is a flow diagram illustrating an example technique
for forming EBC on a substrate.
[0010] FIG. 4 is a flow diagram illustrating another example
technique for forming EBC on a substrate.
[0011] FIG. 5 is a conceptual and schematic diagram illustrating an
example article including an EBC on a substrate.
DETAILED DESCRIPTION
[0012] The disclosure describes systems and techniques for forming
an environmental barrier coating (EBC) system using thermal spray
deposition, such as air plasma spraying. The EBC coating system may
be deposited on a substrate, such as, CMC substrates, that serves
as components of jet engines or other high temperature systems.
Thermal spray systems may be used in a wide variety of industrial
applications to coat such substrates with EBC systems to modify or
improve the properties of underlying substrate or component as a
whole. Thermal spray systems may use heat generated electrically,
by plasma, or by combustion to heat material injected in a plume,
so that molten or softened material propelled by the plume contact
the surface of the target. Upon impact, the molten or softened
material adheres to the target surface, resulting in a coating.
[0013] EBC systems may be an important contributor to the success
of CMCs in a high temperature system. For example, the coatings may
be configured to protect against oxidation, water vapor recession,
and other deleterious reactions from damaging the structural CMC,
e.g., during operation of the high temperature system. In some
examples, an EBC system may contain a multilayered structure
including a silicon bond layer and a rare-earth disilicate layer.
The layers of the EBC system may be deposited using a thermal
spraying process, such as, air plasma spraying, which may produce
an amorphous structure within the coating, e.g., due to the high
cooling rates/quenching of the particles upon impact with a
substrate. The resulting amorphous structure may change to a
crystalline structure over time when subjected to higher
temperatures, e.g., during operation of a high temperature system.
An uncontrolled transition from amorphous to crystalline structure
over time may also result in volumetric changes and, thus, internal
stresses in the layer(s) (e.g., a rare-earth disilicate layer). In
particular, in some examples, as the EBC structure changes from
amorphous to crystalline, there may be shrinkage in the overall
area. This may cause a build-up in stress on the EBC as well as the
silicon bond coat. Eventually, the build-up in stress reaches a
threshold and causes a crack to pop to relieve the stress
state.
[0014] In accordance with examples of the disclosure, systems and
techniques are described that include controlling the substrate
and/or coating temperatures before, during and/or after deposition
of an EBC system, e.g., to increase or otherwise control the amount
of crystalline phase in the EBC system. The crystalline phase of an
EBC system may be controlled to reduce internal stresses during
operation of a coated component due to the amorphous phase to
crystalline phase transition. In some examples, following
deposition of one or more layers of an EBC system, the coated
substrate (EBC system and underlying substrate) may be heat treated
at a relatively high temperature for a selected duration of time.
Following the heat treatment, the coated substrate may be cooled at
a controlled rate, e.g., such that the coated substrate (e.g., the
EBC system on the underlying substrate) cools at a desired rate
and/or for a desired duration of time to a prescribed temperature.
Some examples systems and techniques of the disclosure include
controlling the post-deposition heating and cooling rate of a
coated substrate through a selected temperature range during which
an amorphous phase would otherwise form if cooled at too high a
rate, e.g., between 800 degrees Celsius (C) and 1100 degrees C.
[0015] Controlling the post-deposition temperature, cooling rate,
and/or time may allow for a transition from amorphous to
crystalline phase in one or more layers of the deposited coating
system, e.g., in a manner that minimizes or otherwise reduces the
internal stresses in the layer(s) of the EBC system, e.g., that
would otherwise be present during heating of the EBC system during
operation of a jet engine including the coated component. For
example, thermal sprayed rare earth silicates may effectively
quench in an amorphous phase during rapid solidification on a cold
substrate that is below the amorphous-crystalline transition
temperature. Upon heating the coating past amorphous-crystalline
transition temperature, two events may occur: 1) transformation
from amorphous to crystalline atom structure, and 2) viscous flow
of the amorphous coating prior to the phase transformation (may not
occur if heating rate is too rapid). The combination of these
events may act to resolve the residual stress. In some example, the
goal may be to have fully crystalline coatings (e.g., the one or
more layers of the EBC system being substantially all crystalline
phase with minimum, relatively low, or trace amounts of amorphous
phase. In some examples, the one or more layers of an EBC system
may have about 95 wt % crystallinity post-heat treatment (e.g.,
including a controlled cooling phase).
[0016] In some examples, when the one or more layers of an EBC
system is sprayed onto a cold substrate, the coating locks in an
amorphous microstructure. When the amorphous structure is heated,
the coating transitions to a crystalline (lower energy state)
microstructure. During this phase change, the overall volume
decreases, causing a build-up of residual stress. If this stress is
significant, it will crack the EBC and/or substrate. By controlling
the post-deposition heat treatment, cooling rate, and/or
temperature of deposition, the rate at which the stresses form may
be controlled and/or the residual stress may be relaxed out. In
some examples, the heat treatment temperature and/or cooling rate
of a deposited coating may be controlled to obtain a relaxed EBC
system, e.g., prior to employing a coated substrate in operation as
part of a high temperature gas turbine engine.
[0017] In some examples, systems and techniques of the disclosure
include movement of a substrate from a spraying position within the
air plasma spray system or other thermal spray system to a furnace
with temperature control following deposition of one or more layers
of an EBC coating system on the substrate. Such a transfer may
employ the use of robotic systems and fixtures for substrate
holding and manipulation, thus allowing for fast transition of a
substrate from spray position to the furnace upon completion of the
spray process. In some examples, this transition may take place
relatively quickly following the coating of the substrate and prior
to the component cooling below a threshold temperature, e.g., below
800 degrees C. or some other pre-heated temperature in examples in
which substrate pre-heating has taken place. The coated substrate
temperature may then be maintained in the furnace for a duration
that allows for the transition of the coating to a more highly
crystalline state, e.g., depending on furnace configuration,
fixturing size, overall thermal load, and/or the like.
[0018] In some examples, systems and techniques of the disclosure
include pre-heating of a substrate to a prescribed temperature
prior to coating in a furnace (or other suitable heating system).
In such instances, a robotic system may withdraw the substrate from
the furnace after being heated to the prescribed temperature to the
thermal spray system fixturing apparatus, upon which the coating is
applied and maintained at elevated temperature. The coated
substrate may be then re-introduced to the furnace (or moved to
another furnace or other suitable heating system) for further
controlled heat treatment, e.g., to enhance microstructure,
crystallinity, and/or residual stress. In other examples, systems
and techniques of this disclosure may include a post-coating heat
treatment that is effective in controlling the crystalline
structure of deposited layers even in the absence of pre-heating of
a substrate and/or in-situ heating of the substrate during the
deposition process.
[0019] FIG. 1 is a conceptual and schematic diagram illustrating an
example system 10 for depositing an EBC system on a substrate using
a thermal spray process that includes controlled heating before
and/or after the deposition of the EBC system. As shown, system 10
includes thermal spray device 12, pre-heat/post-heat furnace 14
(referred to also as "furnace 14"), and robotic transfer device 16.
Although furnace 14 is shown as a single furnace in FIG. 1, in some
examples, system 10 may include more than one furnace, e.g., one
furnace for the pre-deposition heat treatment and another furnace
for post-deposition heat treatment.
[0020] Thermal spray device 12 may be configured to deposit one or
more layers of a coating system on a substrate to form a coated
article, such as article 66 in FIG. 5 which includes EBC system 68
on substrate 24, using a thermal spray process. Example thermal
spray processes may include suspension plasma spray, low pressure
plasma spraying, plasma spray physical vapor deposition, and air
plasma spraying. As will be described below, in one example,
thermal spray device 12 may be configured to deposit the one or
more layers of a coating system using a plasma spray process, such
as an air plasma spray process. In an air plasma spray process, the
plasma is sprayed in an air environment, e.g., as compared to a
spraying in a vacuum or an inert gas (e.g., argon) environment. Air
plasma spraying may be amenable to automation for the application
of coatings onto complex surfaces. The deposition rates may be very
economical compared to other processes such as HVOF. For ease of
description, the operation of system 10 will primarily be described
herein with regard to article 66 of FIG. 5 although other articles
formed using system 10 are contemplated.
[0021] Furnace 14 may be configured to heat and/or maintain article
66 at a relatively high temperature following the deposition of
layer(s) of a coating system using thermal spray device 12, e.g.,
to perform a post-deposition heat treatment on the coated
substrate. Furnace 14 may also be configured to cool down article
66 following the post-deposition heat treatment at a controlled
rate over a duration of time to a reduced temperature. Furnace 14
may also be configured to heat and/or maintain substrate 24 at a
relatively high temperature following the deposition of layer(s) of
a coating system using thermal spray device 12, e.g., to perform a
pre-deposition heat treatment of substrate 24. Furnace 14 may
include an internal cavity sized and otherwise configured to
contain substrate 14, either before or after being coated with EBC
system 68. Any suitable type of furnace 14 may be used that is
capable of functioning as described in this disclosure. Furnace 14
may be an air furnace or a box furnace. In one example, a box
furnace may be used with a controllable heat source. In some
examples, furnace 14 may include one or more suitable heat sources
such as moly-disilicide and/or carbide heating elements, although
other types of heat sources are contemplated. In one example, a
conveyor-belt furnace may be employed.
[0022] Robotic transfer device 16 may be configured to robotically
transfer substrate 24 between furnace 14 and thermal spray device
12, as desired before and/or after the deposition of EBC system 68
vie thermal spray device 12.
[0023] Computing device 18 may be configured as a control device
that controls thermal spray device 12, furnace 14, and/or robotic
transfer device 16 to operate in the manner described herein. For
example, computing device 18 may be configured to control the
temperature, including heating and cooling rates, of furnace 14,
e.g., during pre-deposition and/or post-deposition heat treatment
of substrate 24 and article 66, respectively. Computing device 18
may be configured to control robotic transfer device 16 to control
the transfer of substrate 24 and article 66 between thermal spray
device 12 and furnace 14. Computing device 18 may be
communicatively coupled to at least one of thermal spray device 12,
furnace 14, and/or robotic transfer device 16 using respective
communication connections. Such connections may be wireless and/or
wired connections. While computing device 18 is shown as a single
device, in other examples, computing device 18 may be more than one
computing device, such as, e.g., where each of furnace 14, thermal
spray device 12 and robotic transfer device 16 are controlled by
different computing devices.
[0024] Computing device 18 may include, for example, a desktop
computer, a laptop computer, a workstation, a server, a mainframe,
a cloud computing system, or the like. Computing device 18 may
include or may be one or more processors or processing circuitry,
such as one or more digital signal processors (DSPs), general
purpose microprocessors, application specific integrated circuits
(ASICs), field programmable logic arrays (FPGAs), or other
equivalent integrated or discrete logic circuitry. Accordingly, the
term "processor" and "processing circuitry" as used herein may
refer to any of the foregoing structure or any other structure
suitable for implementation of the techniques described herein. In
addition, in some examples, the functionality of computing device
18 may be provided within dedicated hardware and/or software
modules.
[0025] In one example, system 10 may be configured to form an
article such as article 66 shown in FIG. 5, which includes EBC
system 68 deposited on substrate 24. For example, system 10 may be
configured to deposit one or more layers of EBC system 66 on
substrate 24 using thermal spray device 12, e.g., by air plasma
spraying or other thermal spray deposition process. Following the
deposition of EBC system 66 on substrate 24 by thermal spray device
12, article 66 may be moved to furnace 14 (e.g., via robotic
transfer device 16) for a post deposition heat treatment. As will
be described further below, the post-deposition heat treatment in
furnace 14 may be controlled by computing device 18 so that article
66 is at an elevated temperature (e.g., a temperature at or above
the crystallization temperature of EBC system 68) for a desired
duration of time. Computing device 18 may also control the cooling
of article 66 such that article 66 is cooled, e.g., at a specific
rate to a lower temperature over a duration of time, as compared to
only removing article 66 from furnace 14 so that it cool based on
the ambient temperature of the surrounding environment. In some
examples, the post-deposition heat treatment and/or controlled cool
down in furnace 14 may provide for an increase in the amount of
crystalline phase to amorphous phase in EBC system 68, e.g., as
compared to an article in which the EBC system is deposited by
thermal spray device 12 without such heat treatment and/or control
cool down. In some examples, system 10 may form article 66 using
such a technique with an optional pre-heating of substrate 24
within furnace 14, where substrate 24 is heated to an elevated
temperature of a desired duration of time before being transferred
to thermal spray device 12 for the deposition of EBC system 68.
[0026] FIG. 2 is a block diagram illustrating the example thermal
spray system 12 of FIG. 1. In the example of FIG. 2, thermal spray
system 12 includes components such as enclosure 20 and a thermal
spray gun 22. Enclosure 20 encloses some components of thermal
spray system 12, including, for example, thermal spray gun 22. In
some examples, enclosure 20 substantially completely surrounds
thermal spray gun 22 and encloses an atmosphere. The atmosphere may
include, for example, air, an inert atmosphere, a vacuum, or the
like. In some examples, the atmosphere may be selected based on the
type (e.g., composition) of coating being applied using thermal
spray system 12. Enclosure 20 also encloses a spray target 24.
[0027] Spray target 24 include a substrate to be coated using
thermal spray system 12. In some examples, spray target 24 may
include, for example, a substrate on which a bond coat, a primer
coat, a hard coat, a wear-resistant coating, a thermal barrier
coating, an EBC system, or the like is to be deposited. Spray
target 24 may include a substrate or body of any regular or
irregular shape, geometry or configuration. In some examples, spray
target 24 may include metal, plastic, glass, or the like. Spray
target 24 may be a component used in any one or more mechanical
systems, including, for example, a high temperature mechanical
system such as a gas turbine engine.
[0028] Thermal spray gun 22 is coupled to a gas feed line 26 via
gas inlet port 134, is coupled to a spray material feed line 30 via
material inlet port 32, and includes or is coupled to an energy
source 124. Gas feed line 26 provides a gas flow to gas inlet port
134 of thermal spray gun 22. Depending upon the type of thermal
spray process being performed, the gas flow may be a carrier gas
for the coating material, may be a fuel that is ignited to at least
partially melt the coating material, or both. Gas feed line 26 may
be coupled to a gas source (not shown) that is external to
enclosure 20.
[0029] Thermal spray gun 22 also includes a material inlet port 32,
which is coupled to spray material feed line 30. Material feed line
30 may be coupled to a material source (not shown) that is located
external to enclosure 20. Coating material may be fed through
material feed line 30 in powder form, and may mix with gas from gas
feed line 26 within thermal spray gun 22. The composition of the
coating material may be based upon the composition of the coating
to be deposited on spray target 24, and may include, for example, a
metal, an alloy, a ceramic, or the like.
[0030] Thermal spray gun 22 also includes energy source 34. Energy
source 34 provides energy to at least partially melt the coating
material from coating material provided through material inlet port
32. In some examples, energy source 34 includes a plasma electrode,
which may energize gas provided through gas feed line 26 to form a
plasma. In other examples, energy source 34 includes an electrode
that ignites gas provided through gas feed line 26.
[0031] As shown in FIG. 2, an exit flow stream 38 exits outlet 36
of thermal spray gun 22. In some examples, outlet 36 includes a
spray gun nozzle. Exit flow stream 38 may include at least
partially melted coating material carried by a carrier gas. Outlet
36 may be configured and positioned to direct the at least
partially melted coating material at spray target 24.
[0032] Computing device 18 may be configured to control operation
of one or more components of thermal spray system 12 automatically
or under control of a user. For example, computing device 18 may be
configured to control operation of thermal spray gun 22, gas feed
line 26 (and the source of gas to gas feed line 26), material feed
line 30 (and the source of material to material feed line 30), and
the like. For example, computing device 18 may be configured to
control at least one of a temperature, a pressure, a mass flow
rate, a volumetric flow rate, a molecular flow rate, a molar flow
rate, a composition or a concentration, of a flow stream flowing
through thermal spray system 12, for instance, of gas flowing
through gas feed line 26, or of exit flow stream 38, or of material
flowing through material feed line 30.
[0033] In some examples, thermal spray device may include a stage
or other component configured to selectively position and restrain
substrate 24 in place during formation of coating 66. In some
examples, the stage or other component is movable relative to
thermal spray gun 22. For example, in this manner, substrate 24 may
be translatable and/or rotatable along at least one axis to
position substrate 24 relative to plasma spray gun 22. Similarly,
in some examples, plasma spray gun 22 may be movable relative to
substrate 24 to position plasma spray device 20 relative to
substrate 24.
[0034] In some examples, the temperature within enclosure 20 may be
controlled by computing device 18. For example, computing device 18
may elevate the temperature in enclosure 20 above room temperature
during the thermal deposition of EBC system 68. In other examples,
enclosure 20 is not heated but substrate 24 may be pre-heated in
furnace 14 and/or the backside of substrate 24 (surface of
substrate opposite the deposition surface) may be heated only
(e.g., via a furnace or other heating device) during the deposition
process.
[0035] In some examples, computing device 18 may employ one or more
temperature sensors to monitor the temperature of enclosure 20 to
use as feedback to control the temperature of enclosure 20,
substrate 24, and/or EBC system 68. In some examples, a temperature
sensor may directly monitor the temperature of the deposition
surface of substrate 24 and/or EBC system 68 to use as a feedback
to control the temperature of enclosure 20, substrate 24, and/or
EBC system 68. Computing device 18 may control the temperature to
maintain a surface temperature of substrate 24 conducive to the
production of crystalline coatings. In some examples, computing
device 18 may control the temperature of substrate 24 to be about
800 degrees Celsius to about 1100 degrees Celsius, such as, about
850 degree Celsius or greater. In some examples, the method of
control may be a line of site, non-contact surface measurement,
e.g., given that the part may be in motion while coating.
[0036] FIG. 5 is a conceptual schematic diagram illustrating
article 66 that may be formed using system 10 of FIG. 1. In some
examples, article 66 may include a component of a gas turbine
engine. For example, article 66 may include a part that forms a
portion of a flow path structure, a seal segment, a blade track, an
airfoil, a blade, a vane, a combustion chamber liner, or another
portion of a gas turbine engine.
[0037] As described above, article 66 includes EBC system 68 formed
on substrate 24. EBC system 68 may be a single layer or multi-layer
coating, where each layer has substantially the same or different
compositions. As used herein, "formed on" and "on" mean a layer or
coating that is formed on top of another layer or coating, and
encompasses both a first layer or coating formed immediately
adjacent a second layer or coating and a first layer or coating
formed on top of a second layer or coating with one or more
intermediate layers or coatings present between the first and
second layers or coatings. In contrast, "formed directly on" and
"directly on" denote a layer or coating that is formed immediately
adjacent another layer or coating, e.g., there are no intermediate
layers or coatings.
[0038] Substrate 24 may include a material suitable for use in a
high-temperature environment. In some examples, substrate 24 may
include a ceramic or a ceramic matrix composite (CMC). Suitable
ceramic materials, may include, for example, a silicon-containing
ceramic, such as silica (SiO.sub.2) and/or silicon carbide (SiC);
silicon nitride (Si.sub.3N.sub.4); alumina (Al.sub.2O.sub.3); an
aluminosilicate; a transition metal carbide (e.g., WC, Mo.sub.2C,
TiC); a silicide (e.g., MoSi.sub.2, NbSi.sub.2, TiSi.sub.2);
combinations thereof; or the like. In some examples in which
substrate 24 includes a ceramic, the ceramic may be substantially
homogeneous.
[0039] In examples in which substrate 24 includes a CMC, substrate
24 may include a matrix material and a reinforcement material. The
matrix material may include, for example, silicon metal or a
ceramic material, such as silicon carbide (SiC), silicon nitride
(Si.sub.3N.sub.4), an aluminosilicate, silica (SiO.sub.2), a
transition metal carbide or silicide (e.g., WC, Mo.sub.2C, TiC,
MoSi.sub.2, NbSi.sub.2, TiSi.sub.2), or another ceramic material.
The CMC may further include a continuous or discontinuous
reinforcement material. For example, the reinforcement material may
include discontinuous whiskers, platelets, fibers, or particulates.
Additionally, or alternatively, the reinforcement material may
include a continuous monofilament or multifilament two-dimensional
or three-dimensional weave, braid, fabric, or the like. In some
examples, the reinforcement material may include carbon (C),
silicon carbide (SiC), silicon nitride (Si.sub.3N.sub.4), an
aluminosilicate, silica (SiO.sub.2), a transition metal carbide or
silicide (e.g. WC, Mo.sub.2C, TiC, MoSi.sub.2, NbSi.sub.2,
TiSi.sub.2), or the like.
[0040] Substrate 12 may be manufactured using one or more
techniques including, for example, chemical vapor deposition (CVD),
chemical vapor infiltration (CVI), polymer impregnation and
pyrolysis (PIP), slurry infiltration, melt infiltration (MI),
combinations thereof, or other techniques.
[0041] EBC system 68 may help protect underlying substrate 24 from
chemical species present in the environment in which article 66 is
used, such as, e.g., water vapor, calcia-magnesia-alumina-silicate
(CMAS; a contaminant that may be present in intake gases of gas
turbine engines), or the like. Similarly, the EBC system may also
be CMAS resistant, e.g., the EBC system itself may be resistant to
damage caused by CMAS. Similarly, EBC system 66 may also be CMAS
resistant, e.g., the EBC system itself may be resistant to damage
caused by CMAS. Additionally, in some examples, EBC system 68 may
also protect substrate 24 and provide for other functions besides
that of an EBC, e.g., by functioning as a thermal barrier coating
(TBC), abradable coating, erosion resistant coating, and/or the
like.
[0042] Although not directly shown in FIG. 5, in some examples,
article 66 may include a bond coat between EBC system 68 and
substrate 24, e.g., where the bond layer is directly on substrate
24 and EBC system 68 is directly on the bond layer. The bond layer
may increase the adhesion between substrate 24 and EBC system 68.
In some examples, the bond coat has a thickness of approximately 25
microns to approximately 250 microns, although other thicknesses
are contemplated. In examples in which substrate 24 includes a
ceramic or CMC, the bond coat may include a ceramic or another
material that is compatible with the material from which substrate
12 is formed. For example, the bond coat may include mullite
(aluminum silicate, Al.sub.6Si.sub.2O.sub.13), silicon metal or
alloy, silica, a silicide, or the like. The bond coat may further
include other elements, such as a rare earth silicate including a
silicate of lutetium (Lu), ytterbium (Yb), thulium (Tm), erbium
(Er), holmium (Ho), dysprosium (Dy), gadolinium (Gd), terbium (Tb),
europium (Eu), samarium (Sm), promethium (Pm), neodymium (Nd),
praseodymium (Pr), cerium (Ce), lanthanum (La), yttrium (Y), and/or
scandium (Sc).
[0043] EBC system 68 may include one or more EBC layers, which may
be configured to help protect substrate 24 against deleterious
environmental species, such as CMAS and/or water vapor. The
layer(s) of EBC system 68 may include at least one of a rare-earth
oxide, a rare-earth silicate, an aluminosilicate, or an alkaline
earth aluminosilicate. For example, the layer(s) of EBC system 68
may include mullite, barium strontium aluminosilicate (BSAS),
barium aluminosilicate (BAS), strontium aluminosilicate (SAS), at
least one rare-earth oxide, at least one rare-earth monosilicate
(RE.sub.2SiO.sub.5, where RE is a rare-earth element), at least one
rare-earth disilicate (RE.sub.2Si.sub.2O.sub.7, where RE is a
rare-earth element), or combinations thereof. The rare-earth
element in the at least one rare-earth oxide, the at least one
rare-earth monosilicate, or the at least one rare-earth disilicate
may include at least one of lutetium (Lu), ytterbium (Yb), thulium
(Tm), erbium (Er), holmium (Ho), dysprosium (Dy), gadolinium (Gd),
terbium (Tb), europium (Eu), samarium (Sm), promethium (Pm),
neodymium (Nd), praseodymium (Pr), cerium (Ce), lanthanum (La),
yttrium (Y), or scandium (Sc). EBC system 68 may be any suitable
thickness. For example, EBC system 68 may be about 0.005 inches
(about 127 micrometers) to about 0.100 inches (about 2540
micrometers). Other thicknesses are contemplated.
[0044] In some examples, the layer(s) of EBC system 68 additionally
and optionally may include at least one additive, such as at least
one of silica, a rare earth oxide, alumina, an aluminosilicate, an
alkali metal oxide, an alkaline earth metal oxide, an alkali metal
aluminosilicate, an alkaline earth aluminosilicate, TiO.sub.2,
Ta.sub.2O.sub.5, HfSiO.sub.4, or the like. The additive may be
added to the EBC to modify one or more desired properties of the
EBC. For example, the additive components may increase or decrease
the reaction rate of the EBC with calcia-magnesia-alumina-silicate
(CMAS; a contaminant that may be present in intake gases of gas
turbine engines), may modify the viscosity of the reaction product
from the reaction of CMAS and constituent(s) of the EBC, may
increase adhesion of the EBC to the bond coat, may increase the
chemical stability of the EBC, or the like.
[0045] FIG. 3 is a flow diagram illustrating an example technique
for forming a coating that includes an environmental barrier
coating on a substrate using a thermal spray process. The technique
of FIG. 3 will be described with respect to system 10 of FIG. 1 and
article 66 of FIG. 5 for ease of description only. A person having
ordinary skill in the art will recognize and appreciate that the
technique of FIG. 3 may be implemented using systems other than
system 10 of FIG. 1, may be used to form articles other than
article 68 of FIG. 5, or both.
[0046] As shown in FIG. 3, system 10 may optionally perform a
pre-deposition heat treatment on substrate 24 within furnace 14
prior to EBC system 68 being deposited on substrate 24 (40). For
example, substrate 24 may be placed within furnace 14, e.g., by
robotic transfer device 16 under the control of computing device
18. Furnace 14 may be heated to a desired pre-heat temperature
under control of computing device 18 before or after substrate 24
is inserted in furnace 14. The pre-heat temperature of furnace 14
may be selected such that the temperate of substrate 24 is elevated
above the ambient temperature of the external environment and/or
the ambient temperature within thermal spray device 12. In some
examples, the pre-heat temperature of furnace 14 is at least about
800 degrees Celsius (C), such as, about 850 degrees C. to about
1100 degrees C., about 900 degrees C. to about 1100 degrees C., or
about 850 degrees C. to about 1400 degrees C. Substrate 24 may be
held within furnace 24 for a sufficient amount of time to elevate
the temperature of substrate 24 to the pre-heat temperature of
furnace 14 and/or to a temperature of at least about 800 degrees
Celsius (C), such as, about 850 degrees C. to about 1100 degrees
C., about 900 degrees C. to about 1100 degrees C., or about 850
degrees C. to about 1400 degrees C. Other values than those listed
above are contemplated.
[0047] Once substrate 24 is optionally pre-heated to the desired
pre-deposition temperature, robotic transfer device, under the
control of computing device 18, may transfer substrate 24 to the
desired spray position within thermal spray device 12 (42). Once in
the desired spray position, the one or more layers of EBC system 68
may be deposited on substrate 24 by thermal spraying (e.g., air
plasma spraying) using thermal spray device 12 (44). As described
above, thermal spray device 12 may deposit the one or more layers
of EBC system 68 under the control of computing device 18. In some
examples, the temperature within thermal spray device 12 is
elevated.
[0048] In some examples, substrate 24 may have a temperature of
about 800 to about 1100 degrees C., such as, about 850 degrees C.
or greater or about 850 degrees C. to about 1400 degrees C. when
the material of EBC system 68 is first deposited by thermal spray
device 12. In cases in which substrate 24 is pre-heated in furnace
14, the transfer time of substrate 24 between furnace 14 and
initial thermal spraying may be relatively short to prevent
substantially cooling of substrate 24 from that of the pre-heating
temperature.
[0049] When EBC system 68 is deposited, the layer(s) of system 68
may have a relatively high amorphous phase concentration, e.g., due
to the high cooling rates/quenching of the particles upon impact
with substrate 24. For example, the layer(s) of EBC system 68 may
have an amorphous phase of at least about 85 wt %. Conversely, the
layer(s) of EBC system 68 may have a crystalline phase of less than
about 15 wt %. As noted above, without a post-deposition heat
treatment, the amorphous phase may change to a crystalline
structure over time when subjected to higher temperatures, e.g.,
during operation of a jet engine. An uncontrolled transition from
amorphous to crystalline structure with time may also result in
volumetric changes and, thus, internal stresses in the
layer(s).
[0050] In accordance with examples of the disclosure, following
deposition of EBC system 68 on substrate 24, article 66 may be
transferred to furnace 14 by robotic transfer device for a
post-deposition heat treatment (46). In some examples, the
post-deposition heat treatment may take place before or after
article 66 cools to room temperature following deposition. The
post-deposition heat treatment temperature and duration within
furnace 14 may be controlled by computing device 18 and may be
selected to increase the crystalline phase concentration of EBC
system 68 on substrate 24. For example, furnace 14 may be at a
treatment temperature of at or above the crystalline temperature of
the layer(s) of EBC system 68. In some examples, furnace 14 may be
at a treatment temperature of at least about 850 degrees C., such
as, e.g., about 850 degrees C. to about 1400 degrees C., about 900
degrees C. to about 1400 degrees C., about 850 degrees C. to about
1100 degrees C., about 1000 degrees C. to about 1200 degrees C., or
about 900 degrees C. to about 1100 degrees C., and less than about
1400 degrees C. Computing device 18 may control furnace 18 to hold
a substantially constant heat treatment temperature within furnace
or a heat treatment temperature that varies within a prescribed
range over a selected period of time.
[0051] Article 66 may be held within furnace 14 at the heat
treatment temperature such that EBC system 68 reaches a temperature
at or above the crystalline phase temperature of the one or more
layers of EBC system 68. Article 66 may be held within furnace 14
at the heat treatment temperature such that EBC system 68 reaches a
temperature at or above the temperature of the one or more layers
of EBC system 68 at which the amorphous phase transitions to a
crystalline phase. In some examples, depending on the composition
of the layer(s), the layer(s) of EBC system 68 may have a
temperature of at least about 850 degrees C., such as, e.g., about
850 degrees C. to about 1400 degrees C., about 900 degrees C. to
about 1400 degrees C., about 850 degrees C. to about 1100 degrees
C., about 1000 degrees C. to about 1200 degrees C., or about 900
degrees C. to about 1100 degrees C., and less than about 1400
degrees C. during the post-deposition heat treatment. Article 66
may be held within furnace 14 for heat treatment for a suitable
amount of time to provide for a desired amount of crystalline phase
in EBC system 68. Values other than that described above are
contemplated.
[0052] Following the post-deposition cooling, article 66 may
undergo a controlled cooling within furnace 14 (48) from that of
the heat treatment temperature. For example, computing device 18
may control the rate of cooling of furnace 18 over a particle
period of time such that article 66 cools at a controlled rate over
the period of time, as compared to simply removing article 66 from
furnace 14 and or simply turning off furnace 18 while article 66 is
inside. By controlling the cooling of article 66 for a period of
time following the heat treatment, the amount of crystalline phase
may be further tailored, e.g., by not cooling EBC system 68 too
fast at room temperature.
[0053] In some examples, computing device 18 may control the
cooling of article 68 such that the temperature of EBC layer 68
cools at a rate of about 5 degrees C./minute or less. In some
examples, the cooling of article 66 is controlled until the
temperature of EBC system 68 is at or below about 500 degrees
C.
[0054] In some examples, the heat treatment and/or controlled
cooling of article 66 within furnace 14 may be selected to increase
the crystalline phase concentration and/or decrease the amorphous
phase concentration within EBC system 68 compared to that of the
amorphous and crystalline phase content of EBC system 68 following
deposition by thermal spray device 14 but before the heat treatment
and/or controlled cooling In some examples, the heat treatment
and/or cooling of article 66 within furnace 14 may be selected to
increase the crystalline phase concentration and/or decrease the
amorphous phase concentration within EBC system 68 compared to that
of the amorphous and crystalline phase content of EBC system 68
following deposition by thermal spray device 14 but without any
post-deposition heat treatment and/or controlled cooling. In some
examples, increasing the crystalline phase content of the layer(s)
of EBC system 68 may reduce or eliminate the undesired issues that
may arise from amorphous phase being present in EBC system 68,
e.g., as described above.
[0055] In some examples, EBC system 68 may have an amorphous phase
of less than about 50 wt % following the heat treatment describe
above. In some examples, EBC system 68 may have a crystalline phase
of greater than about 50 wt %, such as, e.g., greater than about 60
wt %, greater than about 70 wt %, greater than about 80 wt %,
greater than about 90 wt %, greater than about 95 wt %, greater
than about 96 wt %, less than about 96 wt %, less than 100 wt %,
about 50 wt % and less than 100 wt %, or substantially all
crystalline phase following the heat treatment describe above. In
some examples, the remainder of EBC system 68 may be amorphous
phase. In some examples, the amorphous phase content of the
layer(s) of EBC system 68 may be decreased compared to an article
such as article 66 that does not undergo the described
post-deposition heat treatment. In some examples, the crystalline
phase content of the layer(s) of EBC system 68 may be increased by
compared to an article such as article 66 that does not undergo the
described post-deposition heat treatment. Other values are
contemplated.
[0056] In some examples, EBC system 68 may have an amorphous phase
of less than the as deposited coating following the heat treatment
and controlled cooling describe above. In some examples, EBC system
68 may have a crystalline phase of greater than about 50 wt %, such
as, e.g., greater than about 60 wt %, greater than about 70 wt %,
greater than about 80 wt %, greater than about 90 wt %, greater
than about 95 wt %, greater than about 96 wt %, less than about 96
wt %, less than 100 wt %, about 50 wt % and less than 100 wt %, or
substantially all crystalline phase following the heat treatment
and controlled cooling describe above. In some examples, the
amorphous phase content of the layer(s) of EBC system 68 may be
decreased compared to an article such as article 66 that does not
undergo the described post-deposition heat treatment. In some
examples, the crystalline phase content of the layer(s) of EBC
system 68 may be increased compared to an article such as article
66 that does not undergo the described post-deposition heat
treatment. Other values are contemplated.
[0057] In some examples, in order to achieve and control desired
temperature(s), system 10 may be configured to monitor the
temperature of EBC system 68, substrate 24, and/or furnace 14 using
one or more suitable temperature sensors (e.g., thermocouples)
located to accurately measure temperature (e.g., in substantially
real-time) during the described techniques. In some examples, such
components may be thermocoupled during process development trials
to confirm that the desired heating/cooling rates are as expected,
with the measured temperatures in that particular furnace zone used
for control afterwards.
[0058] FIG. 4 is a flow diagram illustrating another example
technique for forming a coating that includes an environmental
barrier coating on a substrate using a thermal spray process. The
technique of FIG. 4 will be described with respect to system 10 of
FIG. 1 and article 66 of FIG. 5 for ease of description only. A
person having ordinary skill in the art will recognize and
appreciate that the technique of FIG. 4 may be implemented using
systems other than system 10 of FIG. 1, may be used to form
articles other than article 68 of FIG. 5, or both.
[0059] As shown in FIG. 4, substrate 24 may be pre-heated in
furnace 14 to a temperature of at least about 850 degrees C. (50).
Computing device 18 may start thermal spray gun 22 and a stabilizer
feeder of thermal spray device 12 (52), e.g., while or after
substrate 24 is being heated (50). The pre-heated substrate 24 may
then be transferred from furnace 14 to the spray position within
thermal spray device 12 by robotic transfer device 16 under the
control of computing device 18 (54). Computing device 18 may then
control plasma spray device 12 to deposit the one or more layers of
EBC system 68 of article 66 on substrate via plasma spray coating
while maintaining a substrate temperature of at least about 850
degrees C. (56). Once EBC system 68 is deposited on substrate 24,
article 66 is transferred from the spray position within thermal
spray device 12 back to furnace 14 by robotic transfer device 16
under the control of computing device 18 for post-deposition heat
treatment (58). Article 60 may be maintained at a temperature of at
least about 850 degrees C. during the heat treatment for a desired
period of time (60). Following the heat treatment, article 66 may
be cooled in furnace 14 at a controlled rate (e.g., about 5 degrees
C./minute or less) to a cooled temperature at or below about 500
degrees C. (62), at which time article 66 may be cooled in an
uncontrolled fashion (e.g., outside furnace 14) to room temperature
(e.g., about 23 degrees C.) (64). The technique of FIG. 4 may be
configured to form one or more layers of EBC system 68 (e.g., a
rare-earth disilicate EBC).
[0060] The techniques described in this disclosure may be
implemented, at least in part, in hardware, software, firmware, or
any combination thereof. For example, various aspects of the
described techniques may be implemented within one or more
processors, including one or more microprocessors, digital signal
processors (DSPs), application specific integrated circuits
(ASICs), field programmable gate arrays (FPGAs), or any other
equivalent integrated or discrete logic circuitry, as well as any
combinations of such components. The term "processor" or
"processing circuitry" may generally refer to any of the foregoing
logic circuitry, alone or in combination with other logic
circuitry, or any other equivalent circuitry. A control unit
including hardware may also perform one or more of the techniques
of this disclosure.
[0061] Such hardware, software, and firmware may be implemented
within the same device or within separate devices to support the
various techniques described in this disclosure. In addition, any
of the described units, modules or components may be implemented
together or separately as discrete but interoperable logic devices.
Depiction of different features as modules or units is intended to
highlight different functional aspects and does not necessarily
imply that such modules or units must be realized by separate
hardware, firmware, or software components. Rather, functionality
associated with one or more modules or units may be performed by
separate hardware, firmware, or software components, or integrated
within common or separate hardware, firmware, or software
components.
[0062] The techniques described in this disclosure may also be
embodied or encoded in a computer system-readable medium, such as a
computer system-readable storage medium, containing instructions.
Instructions embedded or encoded in a computer system-readable
medium, including a computer system-readable storage medium, may
cause one or more programmable processors, or other processors, to
implement one or more of the techniques described herein, such as
when instructions included or encoded in the computer
system-readable medium are executed by the one or more processors.
Computer system readable storage media may include random access
memory (RAM), read only memory (ROM), programmable read only memory
(PROM), erasable programmable read only memory (EPROM),
electronically erasable programmable read only memory (EEPROM),
flash memory, a hard disk, a compact disc ROM (CD-ROM), a floppy
disk, a cassette, magnetic media, optical media, or other computer
system readable media. In some examples, an article of manufacture
may comprise one or more computer system-readable storage
media.
[0063] Various examples have been described. These and other
examples are within the scope of the following claims.
* * * * *