Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITIONS CONTAINING GALLIUM AND/OR INDIUM AND METHODS
OF FORMING THE SAME
PRIORITY INFORMATION
[0001] The present application claims priority to U.S. Patent Application
Serial
No. 15/267,335 filed on September 16, 2016; US. Patent Application Serial No.
15/267,370 filed on September 16, 2016; and US. Patent Application Serial No.
15/267,400 filed on September 16, 2016.
FIELD OF THE INFORMATION
[0002] The present invention generally relates to including gallium (Ga)
and/or
indium (In) compounds within a silicone based coating. In particular, silicon-
based
coatings (e.g., silicon bond coatings) that include Ga and/or In are generally
provided
for use in environmental barrier coatings for ceramic components.
BACKGROUND OF THE INVENTION
[0003] Higher operating temperatures for gas turbine engines are
continuously
being sought in order to improve their efficiency. However, as operating
temperatures
increase, the high temperature durability of the components of the engine must
correspondingly increase. Significant advances in high temperature
capabilities have
been achieved through the formulation of iron, nickel, and cobalt-based
superalloys
Still, with many hot gas path components constructed from super alloys,
thermal
barrier coatings (TBCs) can be utilized to insulate the components and can
sustain an
appreciable temperature difference between the load-bearing alloys and the
coating
surface, thus limiting the thermal exposure of the structural component.
[0004] While superalloys have found wide use for components used throughout
gas turbine engines, and especially in the higher temperature sections,
alternative
lighter-weight substrate materials have been proposed, such as ceramic matrix
composite (CMC) materials. CMC and monolithic ceramic components can be coated
with environmental barrier coatings (EBCs) to protect them from the harsh
environment of high temperature engine sections. EBCs can provide a dense,
hermetic
seal against the corrosive gases in the hot combustion environment.
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[0005] Silicon carbide and silicon nitride ceramics undergo oxidation in
dry, high
temperature environments. This oxidation produces a passive, silicon oxide
scale on
the surface of the material. In moist, high temperature environments
containing water
vapor, such as a turbine engine, both oxidation and recession occurs due to
the
formation of a passive silicon oxide scale and subsequent conversion of the
silicon
oxide to gaseous silicon hydroxide. To prevent recession in moist, high
temperature
environments, environmental barrier coatings (EBC's) are deposited onto
silicon
carbide and silicon nitride materials.
[0006] Currently, EBC materials are made out of rare earth silicate
compounds.
These materials seal out water vapor, preventing it from reaching the silicon
oxide
scale on the silicon carbide or silicon nitride surface, thereby preventing
recession.
Such materials cannot prevent oxygen penetration, however, which results in
oxidation of the underlying substrate. Oxidation of the substrate yields a
passive
silicon oxide scale, along with the release of carbonaceous or nitrous oxide
gas. The
carbonaceous (i.e., CO, CO2) or nitrous (i.e., NO, NO2, etc.) oxide gases
cannot
escape out through the dense EBC and thus, blisters form. The use of a silicon
bond
coat has been the solution to this blistering problem to date. The silicon
bond coat
provides a layer that oxidizes (forming a passive silicon oxide layer beneath
the EBC)
without liberating a gaseous by-product.
[0007] However, the presence of a silicon bond coat limits the upper
temperature
of operation for the EBC because the melting point of silicon metal is
relatively low.
In use, a thermally grown oxide (TGO) layer of silicon oxide forms on the top
surface
of the silicon metal bond coat of a multilayer EBC system. This silicon oxide
scale
remains amorphous at temperatures of 1200 C or lower, sometimes even at
temperatures of 1315 C or lower, although this property is also dependent on
the
time the bond coat is exposed to this temperature. At higher temperatures, or
when
minor amounts of steam penetrate through the EBC to the bond coat, the silicon
oxide
scale crystallizes (e.g., into cristoblate), which undergoes phase transition
accompanied by large volume change on cooling. The volume change leads to EBC
coating spall.
[0008] As such, it is desirable to improve the properties of a silicon bond
coat in
the EBC to achieve a higher operational temperature limit for the EBC.
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BRIEF DESCRIPTION OF THE INVENTION
[0009] Aspects and advantages of the invention will be set forth in part in
the
following description, or may be obvious from the description, or may be
learned
through practice of the invention.
[0010] A composition is generally provided that includes a silicon-
containing
material (e.g., a silicon metal and/or a silicide) and about 0.001% to about
85% of a
Ga-containing compound, an In-containing compound, or a mixture thereof. For
example, the silicon-based layer can be a bond coating directly on the surface
of the
substrate. Alternatively or additionally, the silicon-based layer can be an
outer layer
defining a surface of the substrate, with an environmental barrier coating on
the
surface of the substrate.
[0011] A coated component is also generally provided that includes, in one
embodiment, a ceramic component comprising a plurality of CMC plies and
defining
a surface and a bond coating directly on the surface of the ceramic component,
with
the bond coating including such a composition.
[0012] A method is also generally provided for coating a ceramic component.
In
one embodiment, a bond coating is applied directly on a surface of the ceramic
component, with the bond coating comprises silicon metal and at least one of a
Ga-
containing compound, an In-containing compound, or a mixture thereof.
[0013] Gas turbine engines are also generally provided that include such a
ceramic component.
[0014] These and other features, aspects and advantages of the present
invention
will become better understood with reference to the following description and
appended claims. The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of the
invention and,
together with the description, serve to explain the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A full and enabling disclosure of the present invention, including
the best
mode thereof, directed to one of ordinary skill in the art, is set forth in
the
specification, which makes reference to the appended Figs., in which:
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[0016] FIG. I is a cross-sectional side view of an exemplary ceramic
component
including a silicon-based layer;
[0017] FIG. 2 is a cross-sectional side view of the exemplary ceramic
component
of FIG. I including a thermally grown oxide layer on the silicon-based layer;
[0018] FIG. 3 is a cross-sectional side view of another exemplary ceramic
component including a silicon-based layer;
[0019] FIG. 4 is a cross-sectional side view of the exemplary ceramic
component
of F1G. 3 including a thermally grown oxide layer on the silicon-based layer;
and
[0020] FIG. 5 is a schematic cross-sectional view of an exemplary gas
turbine
engine according to various embodiments of the present subject matter.
[0021] Repeat use of reference characters in the present specification and
drawings is intended to represent the same or analogous features or elements
of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Reference now will be made in detail to embodiments of the
invention,
one or more examples of which are illustrated in the drawings. Each example is
provided by way of explanation of the invention, not limitation of the
invention. In
fact, it will be apparent to those skilled in the art that various
modifications and
variations can be made in the present invention without departing from the
scope of
the invention. For instance, features illustrated or described as part of one
embodiment can be used with another embodiment to yield a still further
embodiment.
Thus, it is intended that the present invention covers such modifications and
variations
as come within the scope of the appended claims and their equivalents.
[0023] As used herein, the terms "first", "second", and "third" may be used
interchangeably to distinguish one component from another and are not intended
to
signify location or importance of the individual components.
[0024] Chemical elements are discussed in the present disclosure using
their
common chemical abbreviation, such as commonly found on a periodic table of
elements. For example, hydrogen is represented by its common chemical
abbreviation H; helium is represented by its common chemical abbreviation He;
and
so forth. As used herein, "Ln" refers to a rare earth element or a mixture of
rare earth
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elements. More specifically, the "Ln" refers to the rare earth elements of
scandium
(Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium
(Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium
(Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium
(Yb),
lutetium (Lu), or mixtures thereof.
[0025] In the present disclosure, when a layer is being described as "on"
or "over"
another layer or substrate, it is to be understood that the layers can either
be directly
contacting each other or have another layer or feature between the layers,
unless
expressly stated to the contrary. Thus, these terms are simply describing the
relative
position of the layers to each other and do not necessarily mean "on top of'
since the
relative position above or below depends upon the orientation of the device to
the
viewer.
[0026] Silicon-based coatings that include a Ga-containing compound, a In-
containing compound, or a mixture thereof are generally provided for use with
environmental barrier coatings for ceramic components, along with their
methods of
formation. In particular embodiments, silicon-based bond coatings for
environmental
barrier coatings (EBCs) are generally provided for high temperature ceramic
components, along with methods of its formation and use. In particular, the
silicon-
based bond coating includes a component containing Ga and/or In for preventing
crystallization of a thermal growth oxide ("TGO") on silicon-based bond
coating in an
EBC, which in turn prevents spall of the coating caused by such
crystallization of the
TGO. That is, the introduction of Ga and/or In within the silicon-based bond
coating
keeps the TGO (i.e., the SiO) in an amorphous phase. Accordingly, the
operating
temperature of the silicon-based bond coating (and thus the TGO and EBC
coating)
can be increased. Additionally, the inclusion of Ga and/or In can inhibit and
prevent
crystallization of the TGO without greatly accelerating the growth rate of the
TGO.
Additionally, the Ga-containing compound and/or the In-containing compound, or
a
mixture thereof have limited reaction with and/or solubility into in silicon
oxide,
which can limit the rate of oxide scale growth.
[0027] FIGS. 1-4 show exemplary embodiments of a ceramic component 100
formed from a substrate 102 and a silicon-based layer 104a (FIG. 1), 104b
(FIG. 3),
respectively. Each of the silicon-based layers 104a, 104b includes a silicon-
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containing material and about 0.001% to about 85% of a Ga-containing compound,
a
In-containing compound, or a mixture thereof, such as about 1% to about 60% by
weight of a Ga-containing compound, an In-containing compound, or a mixture
thereof (e.g., about 1% to about 50% by weight, such as about 1% to about 25%
by
weight). Generally, the Ga-containing compound, the In-containing compound, or
mixture thereof is unreactive with the composition of the silicon-based layer
104a
(e.g., silicon metal).
[0028] In one embodiment, the silicon-based layer 104a may include the Ga-
containing compound, the In-containing compound, or the mixture thereof and a
silicon-containing material (e.g., silicon metal, a silicide, etc.) in
continuous phases
that are intertwined with each other. For example, the silicon-containing
material and
the Ga-containing compound, the In-containing compound, or the mixture thereof
are
intertwined continuous phases having about 0.001% to about 85% by volume of
the
Ga-containing compound, the In-containing compound, or the mixture thereof,
such
as about 1% to about 60% by volume (e.g., about 40% to about 60% by volume of
the
Ga-containing compound, the In-containing compound, or the mixture thereof).
For
example, the silicon-based layer 104a can include the Ga-containing compound,
the
In-containing compound, or the mixture thereof in about 15% by volume to about
85% by volume, with the balance being the silicon containing compound.
[0029] In another embodiment, the Ga-containing compound, the In-containing
compound, or the mixture thereof forms a plurality of discrete phases
dispersed within
the silicon-containing material (e.g., within a continuous phase of the
silicon-
containing material), such as discrete particulate phases. In such an
embodiment, the
silicon-based layer 104a can include about 0.001% to about 40% by volume of
the
Ga-containing compound, the In-containing compound, or the mixture thereof,
such
as about 1% to about 25% by volume (e.g., about 1% to about 10% by volume of
the
Ga-containing compound, the In-containing compound, or the mixture thereof).
[0030] In one particular embodiment, the substrate 102 is formed from a CMC
material (e.g., a silicon based, non-oxide ceramic matrix composite). As used
herein,
"CMCs" refers to silicon-containing, or oxide-oxide, matrix and reinforcing
materials.
As used herein, "monolithic ceramics" refers to materials without fiber
reinforcement
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(e.g., having the matrix material only). Herein, CMCs and monolithic ceramics
are
collectively referred to as "ceramics."
[0031] Some examples of CMCs acceptable for use herein can include, but are
not
limited to, materials having a matrix and reinforcing fibers comprising non-
oxide
silicon-based materials such as silicon carbide, silicon nitride, silicon
oxycarbides,
silicon oxynitrides, and mixtures thereof. Examples include, but are not
limited to,
CMCs with silicon carbide matrix and silicon carbide fiber; silicon nitride
matrix and
silicon carbide fiber; and silicon carbide/silicon nitride matrix mixture and
silicon
carbide fiber. Furthermore, CMCs can have a matrix and reinforcing fibers
comprised
of oxide ceramics. Specifically, the oxide-oxide CMCs may be comprised of a
matrix
and reinforcing fibers comprising oxide-based materials such as aluminum oxide
(A1203), silicon dioxide (SiO2), aluminosilicates, and mixtures thereof.
Aluminosilicates can include crystalline materials such as mullite (3A1203
25i02), as
well as glassy aluminosilicates.
[0032] In the embodiment of FIG. 1, the substrate 102 defines a surface 103
having a coating 106 formed thereon. The coating 106 includes the silicon-
based
layer 104a and an environmental barrier coating 108. In one particular
embodiment,
the silicon-based layer 104a is a bond coating, where the silicon containing
material is
silicon metal, a silicide (e.g., a rare earth silicide, a molybdenum silicide,
a rhenium
silicide, or mixtures thereof) or a mixture thereof In one embodiment, a
composition
is generally provided that includes silicon metal and a Ga-containing
compound, an
In-containing compound, or a mixture thereof, such as in the relative amounts
described above (e.g., about 0.01 to about 85% by volume). In an alternative
embodiment, a composition is generally provided that includes a silicide
(e.g., a rare
earth silicide, a molybdenum silicide, a rhenium silicide, or mixtures
thereof) and a
Ga-containing compound, an In-containing compound, or a mixture thereof, such
as
in the relative amounts described above (e.g., about 0.01 to about 85% by
volume).
[0033] During use, a thermally grown oxide ("TGO") layer forms on the
surface
of the bond coating. For example, a layer of silicon oxide (sometimes referred
to as
"silicon oxide scale" or "silica scale") forms on a bond coating of silicon
metal and/or
a silicide. Referring to FIG. 2, a thermally grown oxide layer 105 (e.g.,
silicon oxide)
is shown directly on the silicon-based layer 104a (e.g., a bond coating with
the silicon
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containing material being silicon metal and/or a silicide), as forms during
exposure to
oxygen (e.g., during manufacturing and/or use) of the component 100. Due to
the
presence of the Ga-containing compound, the In-containing compound, or the
mixture
thereof within the silicon-based layer 104a, the thermally grown oxide layer
105
remains substantially amorphous at its operating temperature, with the
"operating
temperature" referring to the temperature of the thermally grown oxide layer
105 For
example, for silicon metal bond coatings, the TGO layer may remain amorphous
at
operating temperatures of about 1415 C or less (e.g., about 1200 C to about
1410
C), which is just below the melting point of the silicon-based bond coating
(Si metal
has a melting point of about 1414 C). In another example, for silicide bond
coatings,
the TGO layer may remain amorphous at operating temperatures of about 1485 C
or
less (e.g., about 1200 C to about 1415 C), which is just below the maximum
use
temperature of the CMC. Without wishing to be bound by any particular theory,
it is
believed that gallium and/or indium in the silicon-based layer 104a migrates
into the
thermally grown oxide layer 105 and inhibits crystallization of the thermally
grown
oxide layer (e.g., silicon oxide) that would otherwise occur at these
temperatures.
Without wishing to be bound by any particular theory, it is presently believed
that Ga
and/or In inhibits impurities such as Na and/or K from causing crystallization
of the
amorphous silicon-containing material.
[0034] In the embodiment shown in FIGS. 1 and 2, the silicon-based layer
104a is
directly on the surface 103 without any layer therebetween However, in other
embodiments, one or more layers can be positioned between the silicon-based
layer
104a and the surface 103.
[0035] FIG. 3 shows another embodiment of a ceramic component 100 with the
substrate 102 having an outer layer 104b that defines a surface 103 of the
substrate
102. That is, the outer layer 104b is integral with the substrate 102. In this
embodiment, the outer layer 104b is the silicon-based layer, and a coating 106
is on
the surface 105. The coating 106 may include an environmental barrier coating
108
and/or other layers (e.g., a bond coating, etc.). In one embodiment, the outer
layer
104b can be a silicon-containing monolithic ceramic layer. For example, the
outer
layer 104b may include silicon carbide. In one embodiment, the substrate 102
may
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include the outer layer 104b (e.g., including silicon carbide as a monolithic
ceramic
layer) on a plurality of CMC plies forming the remaining portion of the
substrate.
[0036] FIG. 4 shows a thermally grown oxide layer 105 (e.g., silicon oxide)
directly on the silicon-based layer 104b (e.g., a bond coating with the
silicon
containing material being silicon metal), as forms during exposure to oxygen
(e.g.,
during manufacturing and/or use) of the component 100. Due to the presence of
the
Ga-containing compound and/or the In-containing compound within the silicon-
based
layer 104b, the thermally grown oxide layer 105 remains substantially
amorphous at
the operating temperature of the thermally grown oxide layer 105. Without
wishing
to be bound by any particular theory, it is believed that gallium and/or
indium in the
silicon-based layer 104b migrates into the thermally grown oxide layer 105 and
inhibits crystallization of the thermally grown oxide layer (e.g., silicon
oxide) that
would otherwise occur at these temperatures.
[0037] As stated, a Ga-containing compound, a In-containing compound, or a
mixture thereof is included within the silicon-based layer 104a, 104b, no
matter the
particular positioning of the silicon-based layer 104 in the ceramic component
100. In
particular embodiments, the Ga-containing compound, the In-containing
compound,
or the mixture thereof is in the form of an oxide or a nitride.
[0038] For example, the Ga-containing compound can be gallium nitride
(GaN),
gallium oxide (Ga203), or a mixture thereof In the embodiment where the Ga-
containing compound includes gallium oxide, the gallium oxide can be doped
within
another oxide. For example, the Ga-containing compound can be zirconium oxide
(ZrO2), hafnium oxide (Hf02), or a combination thereof doped with up to about
10
mole % of Ga203.
[0039] In one embodiment, the Ga-containing compound can be a gallium-metal-
oxide. For example, the Ga-containing compound can have, in one embodiment, a
formula of:
Ga2.xM,03
where M is In with x being 0 to less than 2, Al with x being 0 to about 1.4, B
with x
being 0 to about 1.4, Fe with x being 0 to about 1.4, or a mixture thereof In
one
embodiment, M is In with x being greater than 0 to less than 2, Al with x
being
greater than 0 to about 1.4, B with x being greater than 0 to about 1.4, Fe
with x being
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greater than 0 to about 1.4, or a mixture thereof, such that at least one
other metal (In,
Al, B, and/or Fe) is present in the gallium-metal-oxide.
[0040] In one embodiment, the Ga-containing compound can be a rare earth-
gallium-oxide. For example, the Ga-containing compound can have, in one
embodiment, a formula of:
Ln4_xD,Ga2_yIny09
where Ln is La, Ce, Pr, Nd, Pm, Sm, or a mixture thereof; D is La, Ce, Pr, Nd,
Pm,
Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or a mixture thereof, with D being
different
than Ln (i.e., D is a different element or combination of elements than Ln);
and y is 0
to about 1 (e.g., 0 < y < 1, such as 0 < y < 0.5). In one particular
embodiment, y is
greater than 0 to about 1 (e.g., 0 < y < 1, such as 0 < y < 0.5). If D is La,
Ce, Pr, Nd,
Pm, Sm, or a mixture thereof (i.e., having an atomic radius of Sm or larger),
then x is
0 to less than 4 (e.g., 0 <x < 4, such as 0 <x < about 2). However, if D is
Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, Lu, or a mixture thereof (i.e., having an atomic radius
that is
smaller than Sm), then x is 0 to about 2 (e.g., 0 <x < 2, such as 0 <x < about
1).
[0041] In another embodiment, the Ga-containing compound can have a formula
of:
Ln3Ga5Mx017
where Ln is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,
or a
mixture thereof; and M is In with x being 0 to less than 5 (e.g., 0 < x < 5,
such as 0 <
x < 2.5), Al with x being 0 to less than 5 (e.g., 0 < x < 5, such as 0 <x <
2.5), Fe with
x being 0 to less than 5 (e.g., 0 < x < 5, such as 0 <x < 2.5), B with x being
0 to about
2.5 (e.g., 0 < x < 2.5), or a combination thereof. In one particular
embodiment, M is
B, with x being greater than 0 to about 2.5 (e.g., 0 <x < 2.5), such as about
0.1 to
about 2 (e.g., 0.1 < x < 2). In one embodiment, x is greater than 0 (e.g., 0.1
to about 2)
such that at least one of M (e.g., In, Al, Fe, and/or B) is present in the Ga-
containing
compound.
[0042] In another embodiment, the In-containing compound can be indium
nitride
(InN), indium oxide (h203), or a mixture thereof. In the embodiment where the
In-
containing compound includes indium oxide, the indium oxide can be doped
within
another oxide. For example, the In-containing compound can be zirconium oxide
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(ZrO2), hafnium oxide (Hf02), or a combination thereof doped with up to about
10
mole % of In203.
[0043] In one embodiment, the In-containing compound can be an indium-metal-
oxide. For example, the In-containing compound can have, in one embodiment, a
formula of:
In2,M,03
where M is Ga with x being 0 to less than 2, Al with x being 0 to about 1.4, B
with x
being 0 to about 1.4, Fe with x being 0 to about 1.4, or a mixture thereof. In
one
embodiment, M is Ga with x being greater than 0 to less than 2, Al with x
being
greater than 0 to about 1.4, B with x being greater than 0 to about 1.4, Fe
with x being
greater than 0 to about 1.4, or a mixture thereof, such that at least one
other metal (Ga,
Al, B, and/or Fe) is present in the indium-metal-oxide.
[0044] In one embodiment, the In-containing compound can have a formula of:
Ln3In5.,,Mx012
where Ln is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,
or a
mixture thereof; and M is Ga with x being 0 to less than 5 (e.g., 0 < x < 5,
such as 0 <
x <2.5), Al with x being 0 to less than 5 (e.g., 0 < x < 5, such as 0 <x <
2.5), Fe with
x being 0 to less than 5 (e.g., 0 < x < 5, such as 0 <x < 2.5), B with x being
0 to about
2.5 (e.g., 0 < x < 2.5), or a combination thereof In one particular
embodiment, M is
B, with x being greater than 0 to about 2.5 (e.g., 0 <x < 2.5), such as about
0.1 to
about 2 (e.g., 0.1 < x < 2). In one embodiment, x is greater than 0 (e.g., 0.1
to about
2) such that at least one of M (e.g., Ga, Al, Fe, and/or B) is present in the
In-
containing compound.
[0045] In one embodiment, the Ga-containing compound, the In-containing
compound, or the mixture thereof can have a formula of:
Ln2,_yGaxInySi202
where Ln is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,
or a
mixture thereof, xis 0 to about 1; y is 0 to about 1; and the sum of x and y
is greater
than 0 (that is, (x + y) > 0). In one embodiment, the sum of x and y is
greater than 0
up to about 1 (i.e., 0 < (x + y) < about 1), such as about greater than 0 up
to about 0.5
(i.e., 0 < (x + y) < about 0.5).
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[0046] In one embodiment, the Ga-containing compound, the In-containing
compound, or the mixture thereof can have a formula of:
Ln2.x_yGaxInySi205
[0047] where Ln is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er,
Tm,
Yb, Lu, or a mixture thereof; xis 0 to about 1; y is 0 to about 1; and the sum
of x and
y is greater than 0 (that is, (x + y) > 0). In one embodiment, the sum of x
and y is
greater than 0 up to about 1 (i.e., 0 <(x + y) < about 1), such as about
greater than 0
up to about 0.5 (i.e., 0 <(x + y) < about 0.5)
[0048] The environmental barrier coating 108 of FIGS. 1-4 can include any
combination of one or more layers formed from materials selected from typical
EBC
or TBC layer chemistries, including but not limited to rare earth silicates
(mono- and
di-silicates), mullite, barium strontium aluminosilicate (BSAS), hafnia,
zirconia,
stabilized hafnia, stabilized zirconia, rare earth hafnates, rare earth
zirconates, rare
earth gallates, etc.
[0049] The ceramic component 100 of FIGS. 1-4 is particularly suitable for
use as
a component found in high temperature environments, such as those present in
gas
turbine engines, for example, combustor components, turbine blades, shrouds,
nozzles, heat shields, and vanes. In particular, the turbine component can be
a CMC
component positioned within a hot gas flow path of the gas turbine such that
the
coating forms an environmental barrier coating on the component to protect the
component within the gas turbine when exposed to the hot gas flow path.
[0050] FIG. 5 is a schematic cross-sectional view of a gas turbine engine
in
accordance with an exemplary embodiment of the present disclosure. More
particularly, for the embodiment of FIG. 5, the gas turbine engine is a high-
bypass
turbofan jet engine 10, referred to herein as "turbofan engine 10." As shown
in FIG.
5, the turbofan engine 10 defines an axial direction A (extending parallel to
a
longitudinal centerline 12 provided for reference) and a radial direction R.
In general,
the turbofan 10 includes a fan section 14 and a core turbine engine 16
disposed
downstream from the fan section 14. Although described below with reference to
a
turbofan engine 10, the present disclosure is applicable to turbomachinery in
general,
including turbojet, turboprop and turboshaft gas turbine engines, including
industrial
and marine gas turbine engines and auxiliary power units.
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[0051] The exemplary core turbine engine 16 depicted generally includes a
substantially tubular outer casing 18 that defines an annular inlet 20. The
outer casing
18 encases, in serial flow relationship, a compressor section including a
booster or
low pressure (LP) compressor 22 and a high pressure (HP) compressor 24; a
combustion section 26; a turbine section including a high pressure (HP)
turbine 28
and a low pressure (LP) turbine 30; and a jet exhaust nozzle section 32. A
high
pressure (BP) shaft or spool 34 drivingly connects the HP turbine 28 to the BP
compressor 24. A low pressure (LP) shaft or spool 36 drivingly connects the LP
turbine 30 to the LP compressor 22.
[0052] For the embodiment depicted, the fan section 14 includes a variable
pitch
fan 38 having a plurality of fan blades 40 coupled to a disk 42 in a spaced
apart
manner. As depicted, the fan blades 40 extend outwardly from disk 42 generally
along
the radial direction R. Each fan blade 40 is rotatable relative to the disk 42
about a
pitch axis P by virtue of the fan blades 40 being operatively coupled to a
suitable
actuation member 44 configured to collectively vary the pitch of the fan
blades 40 in
unison. The fan blades 40, disk 42, and actuation member 44 are together
rotatable
about the longitudinal axis 12 by LP shaft 36 across an optional power gear
box 46.
The power gear box 46 includes a plurality of gears for stepping down the
rotational
speed of the LP shaft 36 to a more efficient rotational fan speed.
[0053] Referring still to the exemplary embodiment of FIG. 5, the disk 42
is
covered by rotatable front nacelle 48 aerodynamically contoured to promote an
airflow through the plurality of fan blades 40 Additionally, the exemplary fan
section
14 includes an annular fan casing or outer nacelle 50 that circumferentially
surrounds
the fan 38 and/or at least a portion of the core turbine engine 16. It should
be
appreciated that the nacelle 50 may be configured to be supported relative to
the core
turbine engine 16 by a plurality of circumferentially-spaced outlet guide
vanes 52.
Moreover, a downstream section 54 of the nacelle 50 may extend over an outer
portion of the core turbine engine 16 so as to define a bypass airflow passage
56
therebetween.
[0054] During operation of the turbofan engine 10, a volume of air 58
enters the
turbofan 10 through an associated inlet 60 of the nacelle 50 and/or fan
section 14. As
the volume of air 58 passes across the fan blades 40, a first portion of the
air 58 as
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indicated by arrows 62 is directed or routed into the bypass airflow passage
56 and a
second portion of the air 58 as indicated by arrow 64 is directed or routed
into the LP
compressor 22. The ratio between the first portion of air 62 and the second
portion of
air 64 is commonly known as a bypass ratio. The pressure of the second portion
of air
64 is then increased as it is routed through the high pressure (HP) compressor
24 and
into the combustion section 26, where it is mixed with fuel and burned to
provide
combustion gases 66.
[0055] The combustion gases 66 are routed through the HP turbine 28 where a
portion of thermal and/or kinetic energy from the combustion gases 66 is
extracted via
sequential stages of HP turbine stator vanes 68 that are coupled to the outer
casing 18
and HP turbine rotor blades 70 that are coupled to the HP shaft or spool 34,
thus
causing the HP shaft or spool 34 to rotate, thereby supporting operation of
the HP
compressor 24. The combustion gases 66 are then routed through the LP turbine
30
where a second portion of thermal and kinetic energy is extracted from the
combustion gases 66 via sequential stages of LP turbine stator vanes 72 that
are
coupled to the outer casing 18 and LP turbine rotor blades 74 that are coupled
to the
LP shaft or spool 36, thus causing the LP shaft or spool 36 to rotate, thereby
supporting operation of the LP compressor 22 and/or rotation of the fan 38.
[0056] The combustion gases 66 are subsequently routed through the jet
exhaust
nozzle section 32 of the core turbine engine 16 to provide propulsive thrust.
Simultaneously, the pressure of the first portion of air 62 is substantially
increased as
the first portion of air 62 is routed through the bypass airflow passage 56
before it is
exhausted from a fan nozzle exhaust section 76 of the turbofan 10, also
providing
propulsive thrust. The HP turbine 28, the LP turbine 30, and the jet exhaust
nozzle
section 32 at least partially define a hot gas path 78 for routing the
combustion gases
66 through the core turbine engine 16.
[0057] Methods are also generally provided for coating a ceramic component.
In
one embodiment, the method includes applying a bond coating directly on a
surface of
the ceramic component, where the bond coating comprises a silicon-containing
material (e.g., silicon metal and/or a silicide) and at least one of a Ga-
containing
compound, an In-containing compound, or a mixture thereof.
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[0058] This written description uses examples to disclose the invention,
including
the best mode, and also to enable any person skilled in the art to practice
the
invention, including making and using any devices or systems and performing
any
incorporated methods. The patentable scope of the invention may include other
examples that occur to those skilled in the art in view of the description.
Such other
examples are intended to be within the scope of the invention.