Systems and methods for limiting pore formation in ceramic matrix composite components

Abstract

A method for limiting pore formation in a melt impregnated ceramic matrix composite (MI-CMC) component includes configuring one or more penetrant feedstocks in fluid communication with a target region of the MI-CMC component. The nominal melting point of the one or more penetrant feedstocks is equal to or lower than the nominal melting point of the alloy within the MI-CMC component. The method includes heating one or more penetrant feedstocks to a first temperature equal to or higher than a nominal melting point of the one or more penetrant feedstocks to form a molten phase. The method further includes infiltrating a target region of the MI-CMC component with a molten phase. As such, the molten phase reacts with the solid phase in the target region of the MI-CMC component. Further, the method includes cooling the MI-CMC component to a second temperature lower than the first temperature, allowing the molten phase to solidify.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to ceramic matrix composite (CMC) components, and more particularly to systems and methods for limiting porosity formation in a CMC component during forming and / or repair. BACKGROUND

[0002] Ceramic matrix composites (CMC), including CMCs utilizing fiber reinforcement, were developed to alleviate damage tolerance issues of monolithic ceramics (e.g., silicon carbide (SiC) ceramics) and have become attractive for high temperature structural applications, such as high temperature structural applications in gas turbine engines. One class of fiber reinforced CMCs that has been particularly attractive for high temperature structural applications is reaction melt infiltration fiber reinforced CMCs (hereinafter "MI-CMC").

[0003] In MI-CMCs, a preform of fibers and matrix components is infiltrated with a molten material that, upon reaction with the matrix components, produces a ceramic matrix. SiC-based MI-CMCs, in which the infiltrating molten material is silicon or a silicon alloy and the matrix components are such that the resulting matrix is substantially SiC (e.g., SiC and / or C particles), have been particularly attractive for high temperature structural applications due to their high thermal conductivity, excellent thermal shock resistance, creep resistance, and oxidation resistance compared to other CMCs. SUMMARY

[0004] In one aspect, the present disclosure provides a method of limiting porosity formation in a melt infiltrated ceramic matrix composite (MI-CMC) component, the method comprising:

[0005] configuring one or more infiltration sources in fluid communication with a target region of the MI-CMC component, the one or more infiltration sources having a nominal melting point equal to or lower than a nominal melting point of an alloy within the MI-CMC component;

[0006] heating the one or more infiltration sources to a first temperature equal to or greater than the nominal melting point of the one or more infiltration sources, forming a molten phase;

[0007] infiltrating the target region of the MI-CMC component with the molten phase, wherein the molten phase reacts with a solid phase in the target region of the MI-CMC component; and,

[0008] cooling the MI-CMC component to a second temperature lower than the first temperature, solidifying the molten phase.

[0009] In certain embodiments, the one or more infiltration sources comprise one or more infiltration agent feedstocks, the infiltration agent feedstocks containing a silicon-based material and an infiltration agent pre-alloyed material.

[0010] In certain embodiments, the method further comprises:

[0011] saturating the core material with a molten phase of one or more infiltrant sources to form a saturated core material;

[0012] cooling the core material to below a melting point of the alloy to transform the molten phase alloy to a solid phase alloy; and,

[0013] configuring the saturated core material to be in fluid communication with a target region of the MI-CMC component.

[0014] In certain embodiments, the method further comprises:

[0015] delivering the molten phase to the target region of the MI-CMC component before the core material can draw molten alloy from the MI-CMC component to create additional porosity.

[0016] In certain embodiments, the silicon-based material is an infiltrant powder mixture comprising at least one of silicon or a silicon alloy and an additive material.

[0017] In certain embodiments, the additive material comprises a boron-containing additive material.

[0018] In certain embodiments, the one or more infiltrant sources have a nominal melting point below about 1400 degrees Celsius (°C).

[0019] In certain embodiments, the MI-CMC component is part of a gas turbine engine.

[0020] In another aspect, the present disclosure also provides a system for limiting porosity formation in a melt-infiltrated ceramic matrix composite (MI-CMC) component having a target region in need of infiltration, the system comprising:

[0021] one or more infiltrant sources having a nominal melting point equal to or below a nominal melting point of an alloy within the MI-CMC component; and,

[0022] a heat source for heating the one or more infiltrant sources to a first temperature to form a molten phase;

[0023] wherein, when the one or more infiltrant sources are placed in fluid communication with the target region, the molten phase infiltrates and reacts with a solid phase within the MI-CMC component at the target region,

[0024] wherein, the MI-CMC component is cooled to a second temperature below the first temperature to solidify the molten phase.

[0025] In certain embodiments, the one or more infiltration sources include at least one of a wick saturated with a molten phase or one or more infiltration feedstocks including a silicon-based material and an infiltration pre-alloyed material, wherein the silicon-based material is an infiltration powder mixture including at least one of silicon or a silicon alloy and an additive material.

[0026] In certain embodiments, the additive material includes a boron-containing additive material.

[0027] In another aspect, the present disclosure also provides a method of limiting porosity formation in a melt-infiltrated ceramic matrix composite (MI-CMC) component, the method comprising:

[0028] saturating a wick with a molten phase material;

[0029] cooling the saturated wick to a temperature below a melting point of the material, causing a molten phase of the material to transition to a solid phase;

[0030] configuring the saturated wick in fluid communication with a target region of the MI-CMC component;

[0031] heating the saturated wick to a first temperature equal to or greater than the melting point of the material, causing the solid phase of the material to revert to the molten phase;

[0032] infiltrating the target region of the MI-CMC component with the molten phase, wherein the molten phase of the material reacts with a solid phase of another material in the target region of the MI-CMC component; and,

[0033] cooling the MI-CMC component to a second temperature below the first temperature, causing the molten phase to solidify.

[0034] In certain embodiments, the method further comprises:

[0035] providing a first infiltration feedstock; and,

[0036] configuring the saturated wick between the first infiltration feedstock and the target region.

[0037] In certain embodiments, the first infiltration feedstock includes a first silicon-based material having a first nominal melting point, the saturated wick includes a second silicon-based material having a second nominal melting point, and the first nominal melting point is greater than or equal to the second nominal melting point.

[0038] In certain embodiments, the first infiltration feedstock has a first nominal melting point, and the method further comprises:

[0039] forming a second infiltration feedstock having a second nominal melting point.

[0040] In certain embodiments, the method further comprises:

[0041] configuring a second infiltrant feedstock in fluid communication with the first infiltrant feedstock, wherein a second nominal melting point of the second infiltrant feedstock is lower than the first nominal melting point of the first infiltrant feedstock to induce melting of the first infiltrant feedstock prior to the first infiltrant feedstock being heated to the first nominal melting point.

[0042] In certain embodiments, the method further comprises:

[0043] forming a first infiltrant feedstock comprised of an infiltrant powder mixture and an infiltrant pre-alloyed material.

[0044] In certain embodiments, the infiltrant powder mixture comprises a silicon-based powder and a boron-containing additive material.

[0045] In certain embodiments, the method further comprises:

[0046] configuring a non-saturated infiltrated core material adjacent to a saturated infiltrated core material.

[0047] In certain embodiments, the MI-CMC component is part of a gas turbine engine. BRIEF DESCRIPTION OF DRAWINGS

[0048] Reference will now be made to the drawings in which the various embodiments, including the best modes, of the present embodiments are illustrated by way of example. It is to be expressly understood that the drawings are for illustrative purposes and are not a limitation on the scope of the present embodiments.

[0049] Figure 1 is a cross-sectional view of an exemplary gas turbine engine in accordance with an embodiment of the present disclosure.

[0050] Figure 2 is a flow chart of a method of limiting porosity formation in a MI-CMC component during forming and / or repair in accordance with an embodiment of the present disclosure.

[0051] Figure 3 A is a schematic of a system for repairing or forming a MI-CMC component to limit porosity formation during forming and / or repair in accordance with an embodiment of the present disclosure.

[0052] Figure 3 B is a schematic of a system for repairing or forming a MI-CMC component to limit porosity formation during forming and / or repair in accordance with an embodiment of the present disclosure.

[0053] Figure 4 is a flow chart of a method of limiting porosity formation in a MI-CMC component during forming and / or repair in accordance with an embodiment of the present disclosure.

[0054] Figure 5 is a schematic illustration of a system for repairing or forming an MI-CMC component to limit pore formation according to one embodiment of the disclosure.

[0055] Figure 6 is a schematic illustration of a system for repairing or forming an MI-CMC component to limit pore formation according to one embodiment of the disclosure.

[0056] Figure 7 is a schematic illustration of a system for repairing or forming an MI-CMC component to limit pore formation according to one embodiment of the disclosure.

[0057] Figure 8 is a schematic illustration of a system for repairing or forming an MI-CMC component to limit pore formation according to one embodiment of the disclosure.

[0058] Figure 9 is a schematic illustration of a system for repairing or forming an MI-CMC component to limit pore formation according to one embodiment of the disclosure.

[0059] Figure 10 is a schematic illustration of a system for repairing or forming an MI-CMC component to limit pore formation according to one embodiment of the disclosure.

[0060] Reference numbers repeatedly used throughout the specification and drawings are intended to denote the same or similar features or elements of the present disclosure. DETAILED DESCRIPTION

[0061] Reference will now be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. The examples are provided by way of explanation of the embodiments disclosed herein, but are not meant as a limitation of the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the scope or spirit of the described embodiments. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield still a further embodiment. Thus, it is intended that the present disclosure covers all such modifications and variations of the described embodiments as come within the scope of the appended claims and their equivalents.

[0062] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, unless otherwise indicated, all embodiments described herein are to be considered exemplary in nature.

[0063] The singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0064] In the context of, for example, “at least one of A, B, or C,” the term “at least one of’ means A or B or C or any combination of A, B, and C.

[0065] The terms “turbomachine” or “turbomachinery” refer to a machine comprising one or more compressors, a heat-producing section (e.g., a combustion section), and one or more turbines that collectively produce a torque output.

[0066] The term “gas turbine engine” refers to an engine having a turbomachine as its sole source of power or as part of its power source. Exemplary gas turbine engines include turbofan engines, turboprop engines, turbojet engines, turboshaft engines, and the like, as well as hybrid-electric versions of one or more of these engines.

[0067] As used herein, the terms “axial” and “axially” refer to a direction and an orientation that extend substantially parallel to a centerline of the gas turbine engine. Further, the terms “radial” and “radially” refer to a direction and an orientation that extend substantially perpendicular to the centerline of the gas turbine engine. Further, as used herein, the terms “circumferential” and “circumferentially” refer to a direction and an orientation that extend arcuately around the centerline of the gas turbine engine.

[0068] Unless otherwise provided herein, the terms “coupled,” “fixed,” “attached,” and the like, refer to both direct coupling, fixation, or attachment and indirect coupling, fixation, or attachment via one or more intermediate components or features.

[0069] As used herein, the terms “first,” “second,” and “third” can be used interchangeably to distinguish one component from another and are not intended to signify location or importance of individual components.

[0070] The term “adjacent” as used herein with respect to two walls and / or surfaces means that the two walls and / or surfaces are in contact with each other or that the two walls and / or surfaces are separated by one or more non-structural layers and the two walls and / or surfaces are in a series contact relationship with the one or more non-structural layers (i.e., a first wall / surface contacts one or more non-structural layers, which one or more non-structural layers contacts a second wall / surface).

[0071] As used herein, the term “nominal melting point” generally refers to the theoretical temperature at which a solid and a liquid reach an equilibrium state. Further, for a mechanical powder mixture, the nominal melting point of the overall mixture corresponds to the nominal melting point of the component powder having the lowest nominal melting point in the mixture. For example, in a silicon powder and boron powder mixture, the nominal melting point of the mixture is the nominal melting point of the silicon since the nominal melting point of the silicon powder is lower than the boron powder. In the case of an alloy, the nominal melting point corresponds to the solidus temperature of the alloy.

[0072] As used herein, "eutectic composition" generally refers to a mixture of two or more phases under a particular material composition that has the lowest melting point (at which temperature the phases will crystallize simultaneously).

[0073] As used herein, ceramic matrix composite or "CMC" refers to a class of materials that include a reinforcing material (e.g., reinforcing fibers) surrounded by a ceramic matrix phase. Generally, the reinforcing fibers provide structural integrity to the ceramic matrix. Some examples of matrix materials for CMCs can include, but are not limited to, non-oxide silicon-based materials (e.g., silicon carbide, silicon nitride, or mixtures thereof), oxide ceramics (e.g., silicon oxycarbide, silicon oxynitride, aluminum oxide (AI2O3), silicon dioxide (SiO2), aluminosilicates, or mixtures thereof), or mixtures thereof. Optionally, ceramic particles (e.g., oxides of Si, Al, Zr, Y, and combinations thereof) and inorganic fillers (e.g., pyrophyllite, wollastonite, mica, talc, kyanite, and montmorillonite) can also be included within the CMC matrix.

[0074] Some examples of reinforcing fibers for CMCs can include, but are not limited to, non-oxide silicon-based materials (e.g., silicon carbide, silicon nitride, or mixtures thereof), non-oxide carbon-based materials (e.g., carbon, silicon carbide, zirconium carbide), oxide ceramics (e.g., silicon oxycarbide, silicon oxynitride, aluminum oxide (AI2O3), silicon dioxide (SiO2), aluminosilicates (e.g., mullite), or mixtures thereof), or mixtures thereof.

[0075] Generally, a particular CMC can be denoted by its fiber type / matrix type combination. For example, C / SiC denotes carbon fiber reinforced silicon carbide; SiC / SiC denotes silicon carbide fiber reinforced silicon carbide; SiC / SiN denotes silicon carbide fiber reinforced silicon nitride; SiC / SiC-SiN denotes silicon carbide fiber reinforced silicon carbide / nitride matrix mixture, and the like. In other examples, CMCs can include a matrix and reinforcing fibers that include oxide-based materials, such as aluminum oxide (AI2O3), silicon dioxide (SiO2), aluminosilicates, and mixtures thereof. Aluminosilicates can include crystalline materials (e.g., mullite (3AI2O32SiO2)) as well as glassy aluminosilicates.

[0076] In certain embodiments, the reinforcing fibers can be bundled or coated prior to being included in the matrix. For example, the fiber bundles can be formed into reinforcing tapes, such as unidirectional reinforcing tapes. Multiple tapes can be laid up together to form a preform. The fiber bundles can be impregnated with a sizing composition prior to forming the preform or after forming the preform. The preform can then be heat treated (e.g., cured or burned out) to produce a high carbon residue in the preform, and subsequent chemical treatment (e.g., impregnation with a silicon melt) to yield a part formed from a CMC material having a desired chemical composition.

[0077] Such materials are particularly suitable for use in higher temperature applications along with certain monolithic ceramics (i.e., ceramic materials that do not have a reinforcing material). In addition, these ceramic materials are lighter in weight compared to high temperature alloys, but can still provide strength and durability to parts made therefrom. As such, there is currently consideration for using such materials for many gas turbine, spacecraft structures and propulsion parts (e.g., airfoils (e.g., turbine and vane), combustors, shrouds and other similar parts, nozzles, transition ducts, thermal protection systems, TPS, aerodynamic control surfaces and leading edges) that are used in higher temperature segments that would benefit from the lighter weight and higher high temperature resistance that these materials can provide.

[0078] It should also be appreciated that the CMC parts and materials described herein are generally materials that have low ductility and low coefficients of thermal expansion. In addition, typically, CMC materials include ceramic fibers (e.g., silicon carbide (SiC)) that are coated with a compliant material (e.g., boron nitride (BN)). The fiber material can be coated in a ceramic matrix, one form of which is silicon carbide (SiC). When formed into a continuous fiber layer, the CMC material has properties such that the tensile strength of the layer in a direction parallel to the fiber length ("fiber direction") is greater than the tensile strength in a direction perpendicular to the fiber direction. The perpendicular direction can include matrix, interlaminar, secondary or tertiary fiber directions. Between the fiber direction and the matrix direction, various physical properties can also differ.

[0079] Reference will now be made in detail to implementations of the present disclosure, one or more examples of which are illustrated in the drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the present disclosure.

[0080] Traditional reactive melt infiltration manufacturing processes utilize a wick, which is a carbon fiber felt, carbon fabric, or carbon fiber tow, to transport molten metal or alloy from an infiltrant feedstock to a fibrous preform via capillary wetting. For example, the infiltrant feedstock is placed at one end of the carbon fiber felt / fabric, which is proximate to the fibrous preform. The other end of the carbon felt / fabric is in contact with the preform. The infiltrant feedstock is melted at its nominal melting point (pure silicon is about 1407°C to about 1414°C), forming a molten alloy with any alloying agents in the feedstock, which wets and infiltrates the carbon felt / fabric. Some examples of alloying agents include: Ge, Ti, Al, B, Cr, Co, Y, Zr. Since the fibrous preform is also in contact with the carbon felt / fabric, the fibrous preform is wetted by the molten alloy, thereby absorbing the molten alloy via capillary action. As the preform absorbs the molten silicon alloy from the carbon felt / fabric, additional molten alloy is supplied from the molten infiltrant feedstock until the fibrous preform is fully saturated and infiltrated. When the fibrous preform is saturated and infiltrated and becomes dense, the molten alloy is allowed to cool and solidify, densifying the MI-CMC component.

[0081] The infiltrant feedstock can be made from powders (e.g., pure metal powders or non-alloyed powder mixtures (referred to herein as “infiltrant powder mixtures” (e.g., comprising pure silicon powder and boron, among other alloying agent powders))), which can be formed into a shape using various techniques (e.g., pressing, casting, extrusion, etc.) and can be held together with organic binders. In other examples, the infiltrant feedstock can be a bulk material (e.g., ingot) or other form suitable for melt infiltration. During the silicon melt infiltration process, the temperature of the infiltrant feedstock must first reach the nominal melting point of silicon (about 1410 degrees Celsius (°C)) so that a molten alloy forms within a reasonable time. The nominal melting point of the resulting alloy material is lower (e.g., about 1385°C when the silicon alloying element is boron at the eutectic composition) than the nominal melting point of silicon in the infiltrant powder mixture from which the alloy material is formed.

[0082] In certain cases, the MI-CMC component can require a secondary melt infiltration process in which an additional source of molten alloy is provided. For example, a secondary melt infiltration process can be required for a partially infiltrated MI-CMC component (i.e., having some fully saturated and infiltrated regions with free silicon and other infiltrated regions with little or no silicon and residual porosity). In such cases, the partially infiltrated MI-CMC component can be re-infiltrated with an additional source of molten alloy in a secondary melt infiltration (MI) step, in which the additional source of molten alloy from the infiltrant feedstock completes the densification.

[0083] In another example, a damaged MI-CMC component can be repaired with new, un- infiltrated material. As an example, new material (e.g., a fiber reinforcement layer, a matrix layer, a ceramic putty, or other material) can be applied and bonded to the existing MI-CMC component to repair the damaged area. In this case, the un-infiltrated material in the repaired area needs to be infiltrated with molten metal or metal alloy in a secondary MI step to densify the repaired area.

[0084] In another example, an MI-CMC component can be joined to another CMC component or monolithic ceramic via a melt infiltration technique. The components to be joined can be placed in contact with each other, or the joining area can be filled with a joining compound or paste. In some embodiments, the joining compound includes ceramic powders (e.g., silicon carbide and carbon powders), resins that can be converted to carbon via pyrolysis processing, polymeric ceramic precursor resins, or fibers. In either case, the joining area typically needs to be infiltrated with molten metal or metal alloy in a secondary MI step to densify and form a metallurgical bond between the components.

[0085] However, when a secondary MI step is employed using a conventional manufacturing process to rework, repair, or join an MI-CMC component, voids can form in the previously densified area. Without being bound by a particular theory, such voids form because the existing alloy in the MI-CMC component is drawn out by capillary action through the un-infiltrated carbon wick to which it is attached. This can occur when the alloy in the MI-CMC component melts at a faster rate or at a lower temperature than the infiltrant.

[0086] Accordingly, in view of the foregoing, the present disclosure is directed to systems and methods that limit void formation in an MI-CMC component during a secondary MI step used to rework, repair, or join an already infiltrated MI-CMC component. In one embodiment, the systems and methods of the present disclosure can utilize one or more wicks (which are affixed to the fiber preform) that are pre-saturated with an alloy (e.g., silicon alloy) to prevent back-drawing of the silicon alloy from the fiber preform, if necessary. In one particular embodiment, the additional alloy can be supplied using a wick that is pre-saturated with the same alloy contained in the MI-CMC component, without causing increased porosity in the MI-CMC component, because the wick is already saturated with the molten alloy and there is no capillary driving force.

[0087] In some embodiments, during the secondary MI step, additional infiltrant feedstock is provided to the already saturated wicking core so that the core does not become depleted as the secondary MI step progresses and so that the alloy contained in the saturated wicking core during the secondary MI process moves from the core to the portions of the CMC component that need to be filled with alloy. In these embodiments, the additional infiltrant feedstock is designed so that it provides a continuous flow of molten alloy to the core as the secondary MI step progresses. Specifically, if the core becomes depleted of alloy during the secondary MI step, there is a risk that the alloy contained in the infiltrated MI-CMC component can be expelled from the CMC component by capillary action through the now depleted core, resulting in defects, such as porosity, in the infiltrated MI-CMC component.

[0088] In cases where the amount of alloy contained in the saturated wicking core in contact with the MI-CMC component is less than the amount of alloy required by the MI-CMC component, various techniques can be used to supply additional alloy to the saturated wicking core. For example, such techniques can include disposing an additional infiltrant feedstock having a first nominal melting point (e.g., about 1407 °C to about 1414 °C) on the saturated wicking core. In such embodiments, the nominal melting point of the alloy in the MI-CMC component and the molten alloy in the saturated wicking core (e.g., 1385 °C) is lower than the first nominal melting point of the additional infiltrant feedstock (e.g., about 1407 °C to about 1414 °C). Thus, there is no driving force for the silicon alloy in the MI-CMC component to migrate to the saturated wicking core because the core has been saturated with the same silicon alloy.

[0089] Another technique includes disposing an additional infiltrant feedstock having a first nominal melting point (e.g., about 1407 °C to about 1414 °C) on a non-saturated wicking core, wherein a pre-alloyed saturated wicking core is disposed on the non-saturated wicking core and in contact with the fiber preform. Further, the saturated wicking core is in fluid communication with the additional infiltrant feedstock. In such embodiments, the nominal melting point of the alloy in the MI-CMC component and the molten alloy in the saturated wicking core (e.g., 1385 °C) is lower than the first nominal melting point of the additional infiltrant feedstock (e.g., about 1407 °C to about 1414 °C). Thus, there is no driving force for the silicon alloy in the MI-CMC component to migrate to the saturated wicking core because the core has been saturated with the same silicon alloy. Further, in one embodiment, the amount of silicon alloy present in the saturated wicking core should be sufficient so as not to become depleted by absorption from the non-saturated wicking core.

[0090] Another technique includes disposing an additional infiltrant feedstock on the non-saturating infiltrated core material, where the saturating infiltrated core material is disposed on the non-saturating infiltrated core material and in fluid communication with the additional infiltrant feedstock. In such embodiments, the nominal melting point of the additional infiltrant feedstock (e.g., 1385 °C) is substantially equal to (e.g., + / - 10°) the melting point of the alloy in the MI-CMC component and the molten alloy in the saturating infiltrated core material. In this example, the silicon alloy replenishment source melts (e.g., at 1385 °C) to saturate infiltrate the non-saturating infiltrated core material before porosity can form in the component, allowing for a small size saturating infiltrated core material.

[0091] Another technique includes disposing a first infiltrant feedstock having a first composition (having a first nominal melting point (e.g., about 1407 °C to about 1414 °C)) and a second infiltrant feedstock having a second composition (having a second nominal melting point (e.g., 1385 °C)) on a non-saturating infiltrated core material (the first and second infiltrant feedstocks are in contact with each other). Further, a saturating infiltrated core material is disposed on the non-saturating infiltrated core material and in contact with the fiber preform. Further, the saturating infiltrated core material is in fluid communication with the first and second infiltrant feedstocks. In this example, the second composition of the second infiltrant feedstock can be a pre-alloyed eutectic composition that will begin to melt at the second nominal melting point (e.g., 1385 °C) to induce the first infiltrant feedstock to melt before reaching the first nominal melting point (e.g., about 1407 °C to about 1414 °C), thereby preventing porosity formation in the MI-CMC component.

[0092] Another technique includes disposing an additional infiltrant feedstock containing infiltrant pre-alloyed powder on a non-saturating infiltrated core material, where a saturating infiltrated core material is disposed on the non-saturating infiltrated core material and in contact with the fiber preform. In such embodiments, the infiltrant pre-alloyed powder induces a lower infiltrant feedstock melting temperature. Further, in this example, the infiltrant pre-alloyed powder included in the infiltrant feedstock begins to melt at a first nominal melting point (e.g., 1385 °C) and induces the infiltrant feedstock to melt before reaching its nominal melting point (e.g., about 1407 °C to about 1414 °C). Thus, in one embodiment, such an infiltrant feedstock can also be used in the initial component infiltration process to limit the required final infiltration temperature and shorten the component processing time. The infiltrant pre-alloyed powder is a metallurgical alloy having a nominal melting point that is lower than the nominal melting point of the primary metal (e.g., silicon) in the infiltrant powder mixture. The infiltrant pre-alloyed powder can be in the form of a granular material (e.g., fine powder, grain, lump, etc.), a bulk material form (e.g., ingot), or any other form of material that can be used as a feedstock for a melt infiltration process.

[0093] Another technique includes using large (e.g., thicker) saturating-impregnated felts to provide the required silicon to the MI-CMC components. In this example, carbon felts saturated-impregnated with pre-alloyed material can be used to provide the entire (or a substantial portion of) the molten alloy required by the component without the need for any additional infiltrant feedstock or non-saturating-impregnated core material. In certain embodiments, the thickness of the woven fabric core material is typically less than 3 millimeters (mm), while the thickness of the carbon felt (core material) can be up to 25 mm. In certain embodiments, saturating-impregnated fabrics or felts can be used as a source of silicon depending on the alloy requirements of the CMC preform. For example, in one embodiment, since the felt has a thicker cross-section and porosity, it can hold more alloy per unit area than the fabric, and the felt is preferred in cases where a greater weight of alloy is required to infiltrate the preform.

[0094] Referring now to the drawings, Figure 1 A schematic cross-sectional view of a gas turbine engine is shown in accordance with one embodiment of the present disclosure. While further description will be generally made below with reference to a turbofan engine 100, the present disclosure is also applicable to general turbine engines, including turbojet, turboprop, and turboshaft gas turbine engines, including industrial and marine gas turbine engines and auxiliary power units.

[0095] As Figure 1 shown, the turbofan engine 100 has a longitudinal or axial centerline axis 102 extending therethrough for reference purposes. Generally, the turbofan engine 100 can include a core engine 104 disposed downstream of a fan section 106.

[0096] The core engine 104 can generally include a substantially tubular outer casing 108 defining an annular inlet 120. The outer casing 108 can be formed from multiple casings. The outer casing 108 surrounds a compressor section having a supercharger or low-pressure (LP) compressor 122, a high-pressure (HP) compressor 124, a combustion section 126, a turbine section including a high-pressure (HP) turbine 128 and a low-pressure (LP) turbine 130, and an exhaust nozzle section 132 in a series flow relationship. A high-pressure (HP) shaft or spool 134 drivingly connects the HP turbine 128 to the HP compressor 124. A low-pressure (LP) shaft or spool 136 drivingly connects the LP turbine 130 to the LP compressor 122. The LP spool 136 can also be connected to a fan spool or shaft 138 of the fan section 106. In certain embodiments, the LP spool 136 can be directly connected to the fan spool 138, such as in a direct-drive configuration. In an alternative configuration, LP spool 136 may be connected to fan spool 138 via a reduction gear 137 (e.g., a reduction gearbox in an indirect drive or geared configuration). Such a reduction gear may be provided between any suitable shafts / spools within turbofan engine 100 as desired or required.

[0097] like Figure 1 As shown, the fan section 106 includes a plurality of fan blades 140 that are coupled to and extend radially outward from a fan spool 138. An annular fan casing or nacelle 142 circumferentially surrounds the fan section 106 and / or at least a portion of the core engine 104. As will be appreciated by those skilled in the art, the nacelle 142 can be configured to be supported relative to the core engine 104 by a plurality of circumferentially spaced outlet guide vanes 144. Furthermore, a downstream section 146 of the nacelle 142 (downstream of the guide vanes 144) can extend over an exterior portion of the core engine 104 to define a bypass airflow passage 148 therebetween.

[0098] HP turbine 128 includes, in series flow relationship, first stage stator blades 154 (only one shown) axially spaced from turbine rotor blades 158 (only one shown), and second stage stator blades 164 (only one shown) axially spaced from turbine rotor blades 168 (only one shown).

[0099] Now refer to Figure 2A flowchart of an embodiment of a method 200 of limiting porosity formation in an MI-CMC component (e.g., an MI-CMC component that can be used in the turbofan engine 100 described herein) is provided. In particular, the method 200 can be used to repair and / or shape any of the components described herein with respect to the turbofan engine 100 or any other CMC component configuration (e.g., CMC liner, CMC shroud, CMC nozzle, CMC blade, etc.). However, it should be understood that the exemplary method 200 discussed herein is for purposes of describing exemplary aspects of the present disclosure and is not intended to limit the present disclosure. Moreover, although specific steps of the method 200 are described in a particular order, it will be understood by those of ordinary skill in the art using the disclosure provided herein that the steps of any of the methods discussed herein can be adjusted, rearranged, expanded, omitted, or modified in various ways without departing from the scope of the present disclosure. Figure 2 Methods having steps performed in a particular order are depicted for purposes of illustration and discussion. However, a person of ordinary skill in the art using the disclosure provided herein will understand that the steps of any of the methods discussed herein can be adjusted, rearranged, expanded, omitted, or modified in various ways without departing from the scope of the present disclosure.

[0100] As shown at (202), the method 200 includes configuring one or more infiltration sources in fluid communication with a target region of the MI-CMC component, the one or more infiltration sources having a nominal melting point equal to or lower than a nominal melting point of an alloy within the MI-CMC component. In such embodiments, for example, the infiltration sources can include one or more infiltration feedstocks including a silicon-based material and an infiltration pre-alloyed material. Thus, in one embodiment, the method 200 can include forming an infiltration feedstock of an infiltration powder mixture. More specifically, the infiltration powder mixture can include a silicon-based material (e.g., silicon), an additive material (e.g., a boron-containing additive material), and an infiltration pre-alloyed material. In one embodiment, for example, the infiltration pre-alloyed material can be an infiltration pre-alloyed powder (e.g., a eutectic Si-B alloy). Thus, in one embodiment, the infiltration feedstock can be formed from a silicon-based powder and an additive powder, wherein at least a portion of the infiltration feedstock includes an amount of the infiltration pre-alloyed powder. In specific embodiments, examples of the feedstock composition can include 0-95 weight percent (wt%) silicon powder, 2-70 wt% of the following additive materials: B, SiB6, SiB3, B4C, Ti, TiSi2, Hf, HfSi2, Cr, CrSi2, Zr, ZrSi2, Co, CoSi2, Y, Si3Y5, and 5-100 wt% of an infiltration pre-alloyed material including a eutectic Si-B, Si-Ti, Si-Hf, Si-Cr, Si-Zr, Si-Co, Si-Y. As one specific example, the feedstock composition can include 4 wt% B4C powder + 46 wt% silicon boron (Si-B) eutectic in a particulate form (e.g., a powder form) + 50 wt% silicon powder. The resulting infiltration feedstock has a nominal melting point of 1385 °C.

[0101] As shown at (204), method 200 includes heating one or more infiltrating sources to a first temperature equal to or greater than the nominal melting point of the one or more infiltrating sources to form a molten phase. For example, in one embodiment, the nominal melting point of the infiltrant feedstock is less than about 1400 degrees Celsius (°C), preferably between 1340°C and 1385°C. In addition, the nominal melting point of the infiltrant feedstock is less than or equal to the nominal melting point of the alloy within the MI-CMC component. As shown at (206), method 200 includes infiltrating a target region of the MI-CMC component with the molten phase, wherein the molten phase reacts with a solid phase of the alloy within the target region of the MI-CMC component. The solid phase typically includes a carbon material (e.g., in the form of carbon black or pyrolytic carbon) formed by pyrolysis of a material such as a phenolic resin or a furfuryl alcohol resin. As shown at (208), method 200 includes cooling the MI-CMC component to a second temperature lower than the first temperature to allow the molten phase to solidify, repair, or form the MI-CMC component.

[0102] Combine Figure 3 A and Figure 3 B, can better understand Figure 2 Specifically, as shown in FIG, a schematic diagram of an embodiment of a system 250 for repairing or forming a MI-CMC component according to the present disclosure is shown. More specifically, as shown Figure 3 A and Figure 3 As shown in FIG. 2B , system 250 includes an infiltrant feedstock 252 formed from an infiltrant powder mixture 253 and an infiltrant pre-alloyed powder 251. Furthermore, as shown, at least in the repair scenario, system 250 includes a fiber preform 254 for an MI-CMC component. For example, fiber preform 254 may be a partially infiltrated preform, a preform undergoing infiltration repair, and / or a CMC component undergoing repair including a patch. Furthermore, as shown, system 250 includes a heat source 256 for heating the infiltrant feedstock to a first temperature to form a molten phase. The infiltrant pre-alloyed powder has a melting point lower than that of the infiltrant powder mixture, thereby lowering the nominal melting point of infiltrant feedstock 252. The molten phase thus infiltrates the fiber preform 254 of the MI-CMC component using capillary forces and reacts with the solid phase of the fiber preform 254, consolidating the fiber preform. The MI-CMC component may then be cooled to a second temperature lower than the first temperature, allowing the molten phase to solidify and heal or shape to form the MI-CMC component.

[0103] In certain embodiments, as Figure 3 As shown in A, the infiltrant material 252 can be used without an additional core material. In another embodiment, as shown in Figure 3As shown in FIG. 2B, the infiltrant feedstock 252 can be used in combination with a non-saturated infiltrated core material 255 and a saturated infiltrated core material 258 (i.e., a core material saturated infiltrated with a molten phase of a silicon-based alloy). Further, as shown, the saturated infiltrated core material 258 can be disposed between the infiltrant feedstock 252 and the fiber preform 254 of the MI-CMC component.

[0104] Accordingly, in one embodiment, the method 200 can include delivering a molten phase of the infiltrant feedstock 252 before the non-saturated infiltrated core material 255 is able to draw the molten alloy from the fiber preform 254 and create additional porosity. Further, in one embodiment, the lower nominal melting point of the infiltrant feedstock 252 enables the molten phase of the infiltrant feedstock 252 to be delivered to the fiber preform 254 faster than a molten phase of an infiltrant feedstock without pre-alloyed powder of the infiltrant. Figure 3 B), the lower nominal melting point of the infiltrant feedstock 252 enables the molten phase of the infiltrant feedstock 252 to be delivered to the fiber preform 254 faster than a molten phase of an infiltrant feedstock without pre-alloyed powder of the infiltrant.

[0105] Referring now to the drawings Figure 4 A flow diagram of an embodiment of a method 300 of limiting porosity formation of a MI-CMC component (e.g., a MI-CMC component that can be used in the turbofan engine 100 described herein) is provided. Specifically, the method 300 can be used in relation to any of the components described herein in relation to the turbofan engine 100 or any other CMC component configuration. However, it should be understood that the exemplary method 300 discussed herein is for purposes of describing exemplary aspects of the present disclosure and is not intended to limit the present disclosure. Further, although specific steps described herein can be performed in a different order from the order described herein, unless otherwise indicated. Figure 4 For purposes of illustration and discussion, the methods are depicted with steps performed in a particular order. However, a person of ordinary skill in the art will understand that the steps of any of the methods discussed herein can be adjusted, rearranged, expanded, omitted, or modified in various ways without departing from the scope of the present disclosure using the disclosure provided herein.

[0106] As shown at (302), method 300 includes: saturating the core material with the molten phase alloy. For example, in one embodiment, saturating the core material can be accomplished by placing an infiltrant feedstock (e.g., an infiltrant powder mixture, an infiltrant pre-alloyed powder, or both) in fluid communication with the core material to be infiltrated, and then raising the temperature to the melting point of the infiltrant feedstock and maintaining the temperature at the melting point so that the molten alloy flows to the core material and infiltrates it. As shown at (304), method 300 includes: cooling the core material to below the melting point of the alloy to transform the molten phase alloy into a solid phase alloy. As shown at (306), method 300 includes: configuring the saturated infiltrated core material to be in fluid communication with a target area of ​​the MI-CMC component. As shown at (308), method 300 includes: heating the core material to a temperature equal to or above the melting point to return the solid phase to the molten phase. As shown at (310), method 300 includes infiltrating a target region of the MI-CMC component with a molten phase (e.g., utilizing capillary forces to infiltrate the target region of the MI-CMC component with the molten phase), wherein the molten phase reacts with a solid phase (e.g., carbon) in the target region of the MI-CMC component. As shown at (312), method 300 includes cooling the MI-CMC component to a second temperature lower than the first temperature to solidify the molten phase.

[0107] Combine Figures 5-10 , you can better understand Figure 4 In particular, as shown in the figure, a schematic diagram of various embodiments of a system for limiting porosity formation in a MI-CMC component according to the present disclosure is shown. Specifically, when the amount of alloy contained in the saturated core material in contact with the MI-CMC component is lower than the amount of alloy required for the MI-CMC component, various techniques (e.g., Figures 5-10 ) to provide additional alloy to the saturated core material.

[0108] Specifically, if Figures 5-10 , a schematic diagram of various embodiments of a system 350 for repairing or forming a MI-CMC component 352 to limit porosity formation according to the present disclosure is shown. More specifically, as Figure 5As shown, the MI-CMC component 352 is generally formed from a fiber preform 354 infiltrated with a silicon alloy 356 melt. The fiber preform 354 can be, for example, a partially infiltrated preform, or a preform undergoing an infiltration repair, or two ceramic components joined together by a melt infiltration, where at least one component is a melt-infiltrated component, and the other component can be a monolithic ceramic or CMC component. For example, in one embodiment, if the MI-CMC component 352 is damaged, a CMC patch 358 can be used to repair the MI-CMC component 352. In particular embodiments, the patch can need to be melt-infiltrated, which in most cases requires re-heating the patch and the original component to a temperature equal to or above the melting point of the infiltrating metal or metal alloy. Further, in one embodiment, the patch can include a fiber layer or a powder mixture (e.g., silicon carbide and carbon powder), or a carbon resin precursor that forms carbon after a pyrolysis process, or a preceramic polymer (e.g., polycarbosilane, polycarbosiloxane, or a mixture thereof).

[0109] Further, as shown, a saturated wick 360 can be disposed proximate to the fiber preform 354. Thus, when the amount of molten alloy contained within the saturated wick 360 in contact with the MI-CMC component 352 is less than the amount of molten alloy required by the MI-CMC component 352, various techniques can be used to supply additional alloy to the saturated wick 360. For example, as shown, one exemplary technique can include disposing a first infiltrant feedstock 364 having a first nominal melting point (e.g., about 1407 °C to about 1414 °C) on the saturated wick 360. For example, in one embodiment, the first infiltrant feedstock 364 can be composed of Si powder and B4C powder. As such, the saturated wick 360 is configured to transport the molten silicon alloy 362 from the first infiltrant feedstock 364 by capillary wetting. In such embodiments, the nominal melting point of the alloy in the MI-CMC component 352 and the molten alloy in the saturated wick 360 (e.g., 1385 °C) is lower than the first nominal melting point of the first infiltrant feedstock 364 (e.g., about 1407 °C to 1414 °C). Thus, there is no driving force for the silicon alloy in the MI-CMC component 352 to migrate to the saturated wick 360 because the wick 360 is already saturated with the same molten alloy. Figure 5

[0110] Reference is now made to Figure 6 wherein like reference numerals refer to like parts throughout Figure 5 ​The same features described above, another technique for supplying additional alloy to the saturated infiltrated core 360 when the amount of molten alloy contained within the saturated infiltrated core 360 is less than the amount of molten alloy required by the MI-CMC component 352 includes configuring a first infiltrant feedstock 364 having a first nominal melting point (e.g., about 1407 °C to about 1414 °C) on the non-saturated infiltrated core 366. Further, as shown, the saturated infiltrated core 360 can be configured on the non-saturated infiltrated core 366 adjacent to the first infiltrant feedstock 364. Further, as shown, the saturated infiltrated core 360 can be in contact with the fiber preform 354 and in fluid communication with the first infiltrant feedstock 364 (e.g., through the non-saturated infiltrated core 366 being in fluid communication with the first infiltrant feedstock 364). In such an embodiment, the nominal melting point of the alloy in the MI-CMC component 352 and the molten alloy in the saturated infiltrated core 360 (e.g., 1385 °C) is lower than the first nominal melting point of the first infiltrant feedstock 364 (e.g., about 1407 °C to about 1414 °C). Thus, there is no driving force for the silicon alloy in the MI-CMC component 352 to migrate to the saturated infiltrated core 360 because the core 360 is already saturated with the same silicon alloy 362. Further, in one embodiment, the amount of silicon alloy 362 present in the saturated infiltrated core 360 is sufficient so as not to be depleted by absorption from the non-saturated infiltrated core 366.

[0111] Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: Figure 7 wherein like reference numbers represent like elements in the following drawings: Figure 5 The same features described above, another technique for supplying additional alloy to the saturated infiltrated core 360 when the amount of molten alloy contained within the saturated infiltrated core 360 is less than the amount of molten alloy required by the MI-CMC component 352 includes configuring a first infiltrant feedstock 364 having a first nominal melting point (e.g., about 1407 °C to about 1414 °C) on the non-saturated infiltrated core 366. Further, as shown, the saturated infiltrated core 360 can be configured on the non-saturated infiltrated core 366 adjacent to the first infiltrant feedstock 364. Further, as shown, the saturated infiltrated core 360 can be in contact with the fiber preform 354 and in fluid communication with the first infiltrant feedstock 364 (e.g., through the non-saturated infiltrated core 366 being in fluid communication with the first infiltrant feedstock 364). In such an embodiment, the nominal melting point of the alloy in the MI-CMC component 352 and the molten alloy in the saturated infiltrated core 360 (e.g., 1385 °C) is lower than the first nominal melting point of the first infiltrant feedstock 364 (e.g., about 1407 °C to about 1414 °C). Thus, there is no driving force for the silicon alloy in the MI-CMC component 352 to migrate to the saturated infiltrated core 360 because the core 360 is already saturated with the same silicon alloy 362. Further, in one embodiment, the amount of silicon alloy 362 present in the saturated infiltrated core 360 is sufficient so as not to be depleted by absorption from the non-saturated infiltrated core 366. Figure 5 and Figure 6The melting point of the first infiltrant feedstock 364 shown in FIG. 4. In one embodiment, the infiltrant feedstock 368 is prepared by heating the infiltrant powder mixture to its melting temperature and then allowing it to cool, thereby forming an infiltrant alloy. After cooling, the infiltrant alloy can be used directly or further comminuted into particulate form, such as an infiltrant pre-alloyed powder. Further, as shown, the saturated infiltrated core material 360 can be disposed on the non-saturated infiltrated core material 366 between the fiber preform 354 and the non-saturated infiltrated core material 366. Further, as shown, the saturated infiltrated core material 360 is in fluid communication with the infiltrant feedstock 368 (e.g., through the non-saturated infiltrated core material 366 with the infiltrant feedstock 368). Specifically, in such embodiments, the nominal melting point of the infiltrant feedstock 368 (e.g., 1385 °C) is substantially equal to the nominal melting point of the alloy in the MI-CMC component 352 and the molten alloy in the saturated infiltrated core material 360. In this example, the silicon alloy replenishment source is melted (e.g., at 1385 °C) and saturates the non-saturated infiltrated core material 360 before porosity can form in the MI-CMC component 352, thereby allowing the saturated infiltrated core material 360 to have a smaller size, as shown.

[0112] Reference is now made to Figure 8 wherein like reference numerals refer to like features throughout. Figure 7 When the amount of molten alloy contained within the saturated infiltrated core material 360 is less than the amount of molten alloy required for the MI-CMC component 352, another technique for supplying additional alloy to the saturated infiltrated core material 360 includes disposing a first infiltrant feedstock 364 having a first composition (e.g., Si powder and B4C powder) with a first nominal melting point (e.g., about 1407 °C to about 1414 °C) and a second infiltrant feedstock 370 having a second composition (e.g., a eutectic alloy comprising Si and B) with a second nominal melting point (e.g., 1385 °C) on the non-saturated infiltrated core material 366, the first and second infiltrant feedstocks in contact with each other. For example, as shown, the first and second infiltrant feedstocks 364, 370 can be stacked together on the non-saturated infiltrated core material 366. Further, as shown, the saturated infiltrated core material 360 is disposed on the non-saturated infiltrated core material 366 between the fiber preform 354 and the non-saturated infiltrated core material 366. Further, as shown, the saturated infiltrated core material 360 is in fluid communication with the infiltrant feedstocks 364, 370 through the non-saturated infiltrated core material 366. In this example, the composition of the second infiltrant feedstock 370 can include a eutectic alloy that begins to melt at the second nominal melting point (e.g., 1385 °C) to induce melting of the first infiltrant feedstock 364 before reaching the first nominal melting point (e.g., about 1407 °C to about 1414 °C), thereby preventing porosity formation in the MI-CMC component 352.

[0113] Reference is now made to Figure 9 wherein like reference numerals refer to like features described Figure 5 above. Another technique for supplying additional alloy to the MI-CMC part 352 includes configuring an infiltrant feedstock 372 containing infiltrant pre-alloyed powder 374 on the non-saturated infiltrated core 366 when the amount of molten alloy contained within the saturated infiltrated core 360 is lower than the amount of molten alloy required by the MI-CMC part 352. Further, as shown, the saturated infiltrated core 360 is configured on the non-saturated infiltrated core 366 between the fiber preform 354 and the non-saturated infiltrated core 366. Further, the saturated infiltrated core 360 is in fluid communication with the infiltrant feedstock 372 (e.g., through the non-saturated infiltrated core 366 being in fluid communication with the infiltrant feedstock 372). In such embodiments, the infiltrant pre-alloyed powder 374 induces a lower nominal melting point of the infiltrant feedstock 372. Further, in this example, the infiltrant pre-alloyed powder 374 contained within the infiltrant feedstock 372 begins to melt at a first nominal melting point (e.g., 1385 °C) and induces the infiltrant feedstock 372 to melt prior to reaching its nominal melting point (e.g., about 1407 °C to about 1414 °C). Thus, in one embodiment, such infiltrant feedstock 372 can also be used in the initial part infiltration process to limit the required final infiltration temperature and shorten the part processing time.

[0114] Reference is now made to Figure 10 wherein like reference numerals refer to like features described Figure 5 above. Another technique for supplying additional alloy to the MI-CMC part 352 includes using a large (e.g., thicker, wider) saturated infiltrated core 376 to supply the required silicon to the MI-CMC part 352. In this example, the large saturated infiltrated core 376 can be used to supply the molten alloy without any additional infiltrant feedstock or non-saturated infiltrated core. In another embodiment, the thickness of the core 376 (e.g., carbon felt core) can be 5 mm to 25 mm.

[0115] The following provides additional non-limiting examples to further illustrate various embodiments of the present disclosure.

[0116] Example 1

[0117] A CMC part was densified by MI of pure silicon. The nominal melting point of the silicon metal within the CMC part was 1410 °C. An infiltrant feedstock containing 100% pre-alloyed silicon boron (eutectic composition, about 13 at% boron) was used to infiltrate the target region of the MI-CMC part. The nominal melting point of the infiltrant feedstock corresponds to the melting point of the Si-B eutectic (about 13 at% boron): 1385 °C.

[0118] Example 2

[0119] The CMC component was densified by MI of pure silicon. The nominal melting point of the silicon metal within the CMC component was 1410 °C. The target region of the MI-CMC component was infiltrated using an infiltrant feedstock containing 70 wt% silicon powder and 30 wt% pre-alloyed silicon-boron (eutectic composition, approximately 13 at% boron). The nominal melting point of the infiltrant feedstock corresponds to the melting point of the Si-B eutectic (approximately 13 at% boron): 1385 °C.

[0120] Example 3

[0121] The CMC component was densified by MI of a mixture of silicon and boron powders. As a result, the nominal melting point of the alloy within the CMC component was the solidus point of the silicon-boron eutectic (1385 °C). The target region of the MI-CMC component was infiltrated using an infiltrant feedstock containing 60 wt% silicon powder and 40 wt% pre-alloyed silicon-boron (eutectic composition). The nominal melting point of the infiltrant feedstock was approximately 1385 °C.

[0122] Example 4

[0123] The CMC component was densified by MI of a mixture of silicon and boron powders. As a result, the nominal melting point of the alloy within the CMC component was the solidus point of the silicon-boron eutectic (1385 °C). The target region of the MI-CMC component was infiltrated using an infiltrant feedstock comprising 50 wt% silicon powder + 46 wt% silicon-boron (Si-B) eutectic alloy in particulate form (e.g., powder form) + 4 wt% B4C additive powder. The nominal melting point of the infiltrant feedstock was approximately 1385 °C.

[0124] Example 5

[0125] The CMC component was densified by MI of a mixture of silicon and boron powders. As a result, the nominal melting point of the alloy within the CMC component was the solidus point of the silicon-boron eutectic (1385 °C). The target region of the MI-CMC component was infiltrated using an infiltrant feedstock containing 70 wt% silicon powder and 30 wt% pre-alloyed silicon-yttrium (eutectic composition, containing approximately 37 wt% yttrium). The nominal melting point of the infiltrant feedstock corresponds to the melting point of the Si-Y eutectic (37 wt% yttrium): 1242 °C.

[0126] Example 6

[0127] Another example includes saturating the core material with a molten phase silicon boride alloy, where the alloy contains 80 wt% silicon boride (Si-B eutectic composition). Further, the saturated core material is cooled to below 1385 °C, such that the silicon boride alloy is converted to a solid phase. The saturated core material is then configured to be in fluid communication with a target region of the MI-CMC component. Further, the saturated core material is heated to 1390 °C or above 1390 °C, such that the target region of the MI-CMC component is infiltrated with a molten phase of the silicon boride alloy, where the molten phase reacts with the partial carbon in the target region of the MI-CMC component to form silicon carbide. Additionally, the MI-CMC component is cooled to a temperature below 1385 °C.

[0128] Example 7

[0129] Another example includes saturating the core material with a molten phase silicon boride alloy, where the alloy contains 80 wt% silicon boride (Si-B eutectic composition). Further, the saturated core material is cooled to below 1385 °C, such that the silicon boride alloy is converted to a solid phase. The saturated core material is then configured to be in fluid communication with a target region of the MI-CMC component. Further, an infiltrant feedstock is formed by pressing together silicon powder and boron carbide powder (composition of about 93 wt% silicon + 7 wt% boron carbide). The infiltrant feedstock is then configured between the saturated core material and the target region. Additionally, the target region, the saturated core material, and the infiltrant feedstock are heated to a temperature of 1390 °C or above 1390 °C. As such, the target region of the MI-CMC component is infiltrated with a molten phase of the silicon boride alloy, where the molten silicon alloy reacts with the partial carbon in the target region of the MI-CMC component to form silicon carbide. Further, the MI-CMC component is cooled to a temperature below 1385 °C.

[0130] Example 8

[0131] Another example includes saturating a wick material with a molten phase silicon boride alloy, where the alloy contains 80 wt% silicon boride (Si-B eutectic composition). Further, the saturated wick material is cooled below 1385 °C, causing the silicon boride alloy to transition to a solid phase. Additionally, the saturated wick material is disposed in fluid communication with a target region of a MI-CMC component. Further, a first infiltrant feedstock is formed by pressing together silicon powder and boron carbide powder (composition of about 93 wt% silicon + 7 wt% boron carbide). The first infiltrant feedstock is then disposed between the saturated wick material and the target region. Additionally, a second infiltrant feedstock is formed by melting a mixture of silicon and boron carbide powder (composition of about 93 wt% silicon + 7 wt% boron carbide) and then cooling below 1385 °C. The second infiltrant feedstock is then placed in fluid communication with the first infiltrant feedstock. Further, the target region, the saturated wick material, and the first and second infiltrant feedstocks are heated to a temperature of 1390 °C or greater. Further, the target region of the MI-CMC component is infiltrated with a molten phase of the silicon boride alloy, where the molten silicon alloy reacts with some of the carbon in the target region of the MI-CMC component to form silicon carbide. Further, the MI-CMC component is cooled to a temperature below 1385 °C.

[0132] Other aspects of the present disclosure are provided by the subject matter of the following clauses:

[0133] A method of limiting pore formation in a melt infiltrated ceramic matrix composite (MI-CMC) component, the method comprising: disposing one or more infiltrant sources in fluid communication with a target region of a MI-CMC component, the one or more infiltrant sources having a nominal melting point equal to or lower than a nominal melting point of an alloy within the MI-CMC component; heating the one or more infiltrant sources to a first temperature equal to or greater than the nominal melting point of the one or more infiltrant sources, forming a molten phase; infiltrating the target region of the MI-CMC component with the molten phase, where the molten phase reacts with a solid phase in the target region of the MI-CMC component; and cooling the MI-CMC component to a second temperature lower than the first temperature, solidifying the molten phase.

[0134] The method of any of the preceding clauses, wherein the one or more infiltrant sources comprise one or more infiltrant feedstocks containing a silicon-based material and an infiltrant pre-alloyed material.

[0135] The method of any of the preceding clauses, further comprising: saturating a wick material with a molten phase of the one or more infiltrant feedstocks, forming a saturated wick material; cooling the wick material to below the melting point of the alloy, causing the molten phase alloy to transition to a solid phase alloy; and disposing the saturated wick material in fluid communication with the target region of the MI-CMC component.

[0136] The method of any of the preceding clauses, further comprising: delivering a molten phase to a target region of the MI-CMC component prior to the core material being able to draw the molten alloy from the MI-CMC component to create additional porosity.

[0137] The method of any of the preceding clauses, wherein the silicon-based material is an infiltrant powder mixture comprising at least one of silicon or a silicon alloy and an additive material.

[0138] The method of any of the preceding clauses, wherein the additive material comprises a boron-containing additive material.

[0139] The method of any of the preceding clauses, wherein the one or more infiltration sources have a nominal melting point less than about 1400 degrees Celsius (°C).

[0140] The method of any of the preceding clauses, wherein the MI-CMC component is part of a gas turbine engine.

[0141] A system for limiting porosity formation in a melt-infiltrated ceramic matrix composite (MI-CMC) component having a target region in need of infiltration, the system comprising:

[0142] one or more infiltration sources having a nominal melting point equal to or lower than a nominal melting point of an alloy within the MI-CMC component; and,

[0143] a heat source for heating the one or more infiltration sources to a first temperature, forming a molten phase;

[0144] wherein, when the one or more infiltration sources are placed in fluid communication with the target region, the molten phase infiltrates and reacts with a solid phase within the MI-CMC component at the target region, wherein the MI-CMC component is cooled to a second temperature lower than the first temperature to solidify the molten phase.

[0145] The system of any of the preceding clauses, wherein the one or more infiltration sources comprise at least one of a core material saturated with the molten phase or one or more infiltrant feedstocks comprising a silicon-based material and an infiltrant pre-alloyed material, wherein the silicon-based material is an infiltrant powder mixture comprising at least one of silicon or a silicon alloy and an additive material.

[0146] The system of any of the preceding clauses, wherein the additive material comprises a boron-containing additive material.

[0147] A method of limiting void formation in a melt infiltration ceramic matrix composite (MI-CMC) component, the method comprising: saturating infiltrating a core material with a molten phase material; cooling the saturating infiltrated core material to a temperature below a melting point of the material to transition the molten phase of the material to a solid phase; positioning the saturating infiltrated core material in fluid communication with a target region of the MI-CMC component; heating the saturating infiltrated core material to a first temperature equal to or greater than the melting point of the material to restore the solid phase of the material to the molten phase; infiltrating the target region of the MI-CMC component with the molten phase, wherein the molten phase of the material reacts with a solid phase of another material in the target region of the MI-CMC component; and cooling the MI-CMC component to a second temperature below the first temperature to solidify the molten phase.

[0148] The method of any of the preceding clauses, further comprising: providing a first infiltrant feedstock; and positioning the saturating infiltrated core material between the first infiltrant feedstock and the target region.

[0149] The method of any of the preceding clauses, wherein the first infiltrant feedstock comprises a first silicon-based material having a first nominal melting point, the saturating infiltrated core material comprises a second silicon-based material having a second nominal melting point, and the first nominal melting point is greater than or equal to the second nominal melting point.

[0150] The method of any of the preceding clauses, wherein the first infiltrant feedstock has a first nominal melting point, the method further comprising: forming a second infiltrant feedstock having a second nominal melting point.

[0151] The method of any of the preceding clauses, further comprising: positioning the second infiltrant feedstock in fluid communication with the first infiltrant feedstock, wherein the second nominal melting point of the second infiltrant feedstock is lower than the first nominal melting point of the first infiltrant feedstock to induce melting of the first infiltrant feedstock before the first infiltrant feedstock is heated to the first nominal melting point.

[0152] The method of any of the preceding clauses, further comprising: forming the first infiltrant feedstock from an infiltrant powder mixture and an infiltrant pre-alloyed material.

[0153] The method of any of the preceding clauses, wherein the infiltrant powder mixture comprises a silicon-based powder and a boron-containing additive material.

[0154] The method of any of the preceding clauses, further comprising: positioning the non-saturating infiltrated core material adjacent to the saturating infiltrated core material.

[0155] The method of any of the preceding clauses, wherein the MI-CMC component is part of a gas turbine engine.

[0156] This specification discloses the disclosure (including the best mode) using examples, and also enables any person skilled in the art to practice the disclosure (including manufacturing and using any device or system and performing any combined method). The patentable scope of the disclosure is defined by the claims, and can include other examples that a person skilled in the art thinks. If such other examples include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims, such other examples are intended to belong to the scope of the claims.

Claims

1. A method of limiting porosity formation in a melt-infiltrated ceramic matrix composite (MI-CMC) component, the method comprising: positioning one or more infiltration sources in fluid communication with a target region of the MI-CMC component, the one or more infiltration sources having a nominal melting point equal to or lower than a nominal melting point of an alloy within the MI-CMC component; heating the one or more infiltration sources to a first temperature equal to or greater than the nominal melting point of the one or more infiltration sources to form a molten phase; infiltrating the target region of the MI-CMC component with the molten phase, wherein the molten phase reacts with a solid phase in the target region of the MI-CMC component; and, cooling the MI-CMC component to a second temperature lower than the first temperature to solidify the molten phase.

2. The method of claim 1, wherein, the one or more infiltration sources comprise one or more infiltration feedstocks comprising a silicon-based material and an infiltration pre-alloyed material.

3. The method of claim 2, wherein, the method further comprises: saturating a wick material with the molten phase of the one or more infiltration feedstocks to form a saturated wick material; cooling the wick material to a temperature lower than the melting point of the alloy to transform the molten phase alloy to a solid phase alloy; and, positioning the saturated wick material in fluid communication with the target region of the MI-CMC component.

4. The method of claim 3, wherein, the method further comprises: delivering the molten phase to the target region of the MI-CMC component before the wick material can draw molten alloy from the MI-CMC component to create additional porosity.

5. The method of claim 2, wherein, the silicon-based material is an infiltration powder mixture comprising at least one of silicon or a silicon alloy and an additive material.

6. The method of claim 5, wherein, the additive material includes a boron-containing additive material.

7. The method of claim 1, wherein, the nominal melting point of the one or more infiltration sources is lower than about 1400 degrees Celsius (°C).

8. The method of claim 1, wherein, the MI-CMC component is part of a gas turbine engine.

9. A system for limiting porosity formation in a melt-infiltrated ceramic matrix composite (MI-CMC) component having a target region in need of infiltration, the system comprising: one or more infiltration sources having a nominal melting point equal to or lower than a nominal melting point of an alloy within the MI-CMC component; and, a heat source for heating the one or more infiltration sources to a first temperature to form a molten phase; wherein, when the one or more infiltration sources are placed in fluid communication with the target region, the molten phase infiltrates and reacts with a solid phase within the MI-CMC component at the target region, wherein, the MI-CMC component is cooled to a second temperature lower than the first temperature to solidify the molten phase.

10. The system of claim 9, wherein, the one or more infiltration sources include at least one of a wick material saturated with the molten phase or one or more infiltration feedstocks comprising a silicon-based material and an infiltration pre-alloyed material, wherein the silicon-based material is an infiltration powder mixture comprising at least one of silicon or a silicon alloy and an additive material.

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