Patent Publication Number: US-2023158612-A1

Title: Techniques and assemblies for joining components using solid retainer materials

Description:
This application is a divisional filing of U.S. patent application Ser. No. 16/685,265, filed 15 Nov. 2019, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to techniques and assemblies for joining components. 
     BACKGROUND 
     Casting may be used to form metal or alloy components. However, casting relatively large articles or articles having a relatively complex geometry in a single operation may result in deviation of the cast article from specifications or tolerance. Instead of casting or otherwise forming large or complex articles as a single piece or component, such articles may be cast or otherwise fabricated in the form of separate components, which may be joined to form an assembly. For example, the separate components may be arranged at specific relative positions and bonded through thermal processes, such as welding, to form the assembly. 
     SUMMARY 
     The disclosure describes example assemblies and techniques for joining a first component to a second component at a low temperature using a solid retainer material that forms a mechanical interlock. 
     In some examples, the disclosure describes an example technique including positioning a first component and a second component adjacent to each other to define a joint region between adjacent portions of the first component and the second components. The example technique further includes inserting a solid retainer material into the joint region through an opening in one of the first component or the second component to form a mechanical interlock between the first component and the second component. The solid retainer material includes at least one of a metal, a metal alloy, or a ceramic. The example technique includes sealing the opening to retain the solid retainer material within the joint region. In some examples, the solid retainer material includes a plurality of solid retainer modules. In some examples, the example technique includes inserting a binder into the joint region through the opening and solidifying the binder to form a composite mechanical interlock between the first component and the second component. 
     In some examples, the disclosure describes an example assembly including a first component, a second component, and a mechanical interlock. The first and second components are positioned adjacent to each other to define a joint region between adjacent portions of the first component and the second component. The mechanical interlock includes a solid retainer material disposed in the joint region. The solid retainer material includes at least one of a metal, a metal alloy, or a ceramic. In some examples, the solid retainer material includes a plurality of solid retainer modules. In some examples, the mechanical interlock includes a binder around the solid retainer material to form a composite mechanical interlock. 
     The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a conceptual and schematic diagram illustrating an exploded view of an example assembly for joining a first component and a second component by using a plurality of solid retainer modules to form a mechanical interlock. 
         FIG.  1 B  is a conceptual and schematic diagram illustrating a partial view of an example system including the assembly of  FIG.  1 A . 
         FIG.  1 C  is a conceptual and schematic diagram illustrating a partial sectional and exploded view of region A of the system of  FIG.  1 B . 
         FIG.  2 A  is a conceptual and schematic diagram illustrating an exploded view of an example assembly for joining a first component and a second component by using a plurality of solid retainer modules and a binder to form a composite mechanical interlock. 
         FIG.  2 B  is a conceptual and schematic diagram illustrating a partial view of an example system including the assembly of  FIG.  2 A . 
         FIG.  2 C  is a conceptual and schematic diagram illustrating a partial sectional and exploded view of region A of the system of  FIG.  2 B . 
         FIG.  3 A  is a conceptual and schematic diagram illustrating an exploded view of an example assembly for joining a first component and a second component by using a sintered solid retainer material to form a composite mechanical interlock. 
         FIG.  3 B  is a conceptual and schematic diagram illustrating a partial view of an example system including the assembly of  FIG.  3 A . 
         FIG.  3 C  is a conceptual and schematic diagram illustrating a partial sectional and exploded view of region A of the system of  FIG.  3 B . 
         FIG.  4 A  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly for joining a first component and a second component by inserting generically shaped solid retainer modules to form a mechanical interlock. 
         FIG.  4 B  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly for joining a first component and a second component by inserting specifically shaped solid retainer modules to form a mechanical interlock. 
         FIG.  4 C  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly for joining a first component and a second component by inserting solid retainer modules and a binder to form a mechanical interlock. 
         FIG.  4 D  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly for joining a first component and a second component by inserting injection mold having solid particles to form a mechanical interlock. 
         FIG.  5 A  is a flow diagram illustrating an example technique for forming a mechanical interlock using solid retainer modules to join components. 
         FIG.  5 B  is a flow diagram illustrating an example technique for forming a composite mechanical interlock using solid retainer modules and a binder to join components. 
         FIG.  5 C  is a flow diagram illustrating an example technique for forming a monolithic mechanical interlock using a sintered solid retainer material to join components. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure describes example assemblies and techniques for joining a first component to a second component at a low temperature using a solid retainer material that forms a mechanical interlock. A mechanical interlock may be an interlock that has a mechanism that is primarily mechanical (e.g., not adhesive or chemical). A solid retainer material may be a retainer material that does not undergo a bulk melting process (e.g., a thermal process in which a bulk of the retainer material is raised to or above a melting temperature) after insertion of the retainer material into the joint region. The first component and the second component define a joint region, such as adjacent channels or other inset structures. The solid retainer material is inserted and sealed into the joint region as either a preformed structure or subsequently formed structure to form a mechanical interlock in the joint region, thereby restraining the first component relative to the second component. For example, the mechanical interlock may extend at least partially into a channel of each of the first and second components, such that the first component and the second component at least partially surround the mechanical interlock. The first or second components may include components benefitting from a close fitting (relatively low leakage) structural connection in high-temperature operating conditions, such as components of a gas turbine engine, for example, a high-pressure nozzle guide vane and shroud. 
     While techniques such as bi-casting may be used to produce an integrally formed metallic joint to structurally connect components, bi-casting may require a casting foundry including, for example, separate furnace preheat and liquid metal pouring operations with elaborate tooling, as well as close monitor and control during various stages of the process. To integrally form a bi-cast joint, a molten metal or alloy may be heated to a temperature at or above the melting point of components being joined. Moreover, any significant leakage of molten metal or alloy during the bi-casting process may affect the integrity of components being joined or of surrounding furnace tooling, which may be costly and difficult to replace. As an alternative to joining bi-cast components using the metal or alloy of the components, a different metal may be melted and flowed between the components to join the components. This molten metal may have a lower melting point than the components to be joined, but may still expose the components to high temperatures that may cause microstructural changes in the components. Additionally, the molten metal may have less advantageous mechanical properties, such as sheer strength, than metals or alloys having higher melting point temperatures. Regardless of whether a same or different molten metal or alloy is used to join the components, such molten metal or alloy may be difficult to apply and may require large equipment that may be expensive or difficult to position at a particular location, requiring disassembly of the components from a corresponding machine prior to joining the components. 
     In contrast, example techniques and assemblies according to the disclosure may incorporate high strength materials using lower temperatures that are below the melting temperatures of the high strength materials. For example, the solid retainer material forming the mechanical interlock may be a material, such as a superalloy or a ceramic, that has a higher strength than a material that has been melted and solidified within a joint region to form a mechanical interlock. As another example, both a mechanical interlock formed from the solid retainer material and the components that are secured by the mechanical interlock may be exposed to lower temperatures than a mechanical interlock formed by melting and solidifying the retainer material in the joint region. As another example, the solid retainer material may form a composite mechanical interlock with other materials, such as braze materials, that may melt and solidify around the solid retainer material to seal a joint while providing better mechanical properties, such as higher sheer strength, than the solidified braze materials alone. 
     In some instances, example techniques and assemblies according to the disclosure may form a mechanical interlock that incorporates preformed structures. For example, the retainer material may be formed into solid retainer modules having microstructural properties that may remain substantially unchanged between formation of the solid retainer modules and incorporation into a joint region as a mechanical interlock. As another example, the solid retainer modules may include various macrostructural properties, such as shape and size, that may not be achieved with a monolithic mechanical interlock formed in the joint region, such as through melting a retainer material or incorporating a retainer powder in a melted carrier material. 
     In some instances, example techniques and assemblies according to the disclosure may form a mechanical interlock without the use of any molten metals or alloys. For example, the solid retainer material may form a mechanical interlock in the joint region without melting the solid retainer material, thus eliminating large and/or power intensive equipment for melting metals or alloys prior to insertion into the joint region or while contained in the joint region. As a result, components may be secured less expensively, in the field, and/or without requiring disassembly of the components prior to forming a joint between the components. 
     In some examples, a mechanical interlock securing two or more components may be formed from a solid retainer material without exposing the components to molten metals, alloys, or ceramics.  FIG.  1 A  is a conceptual and schematic diagram illustrating an exploded view of an example assembly  10  for joining a first component  12 A and a second component  12 B by inserting and securing a solid retainer material in a joint region to form a mechanical interlock  14 . In some examples, first and second components  12 A and  12 B (also referred to as “components  12 A and  12 B”) may be joined to form an article or a portion of an article that is part of a high temperature mechanical system. For example, components  12 A and  12 B may be joined to form an article or a portion of a nozzle guide vane (NGV) that is used in a high pressure or intermediate pressure stage in a gas turbine engine. In other examples, the article may include another component of a high temperature mechanical system, such as another component of a gas turbine engine. For example, the article may include a gas turbine engine blade alone or with a blade shroud, gas turbine engine vane, blade track, combustor liner, spar, or the like. 
     Each of components  12 A and  12 B may include a metal, an alloy, or a ceramic-based material, such as a ceramic matrix composite (CMC). In some examples, components  12 A and  12 B include substantially the same (e.g., the same or nearly the same) metal or alloy, while in other examples, components  12 A and  12 B include different metals or alloys. Although  FIG.  1 A  illustrates components  12 A and  12 B as each defining a simple, substantially curvilinear geometry, in other examples, one or both of first or second components  12 A or  12 B may define a more complex geometry, including simple or complex curves, overhangs, undercuts, internal cavities, or the like. For example, components  12 B may be a vane having multiple different curvatures. 
     In some examples, one or both of components  12 A and  12 B may include a Ni-, Co-, or Fe-based superalloy, or the like. The superalloy may include other additive elements to alter its mechanical and chemical properties, such as toughness, hardness, temperature stability, corrosion resistance, oxidation resistance, and the like. Any useful superalloy may be utilized in first or second components  12 A or  12 B, including, for example, Ni-based alloys available from Martin-Marietta Corp., Bethesda, Md., under the trade designation MAR-M246, MAR-M247; Ni-based alloys available from Cannon-Muskegon Corp., Muskegon, Mich., under the trade designations CMSX-3, CMSX-4, CMSX-10, and CM-186; Co-based alloys available from Martin-Marietta Corp., Bethesda, Md., under the trade designation MAR-M509; Fe-based alloys; and the like. One or both of components  12 A and  12 B may be made using at least one of casting, forging, powder metallurgy, molding, or additive manufacturing. In some examples, components  12 A and  12 B are made using the same process, while in other examples, components  12 A and  12 B are made using different processes. 
     In some examples, one or both of components  12 A or  12 B may include a ceramic or ceramic matrix composite (CMC). The ceramic or CMC may include any useful ceramic material, including, for example, silicon carbide, silicon nitride, alumina, silica, and the like. The CMC may further include any desired filler material, and the filler material may include a continuous reinforcement or a discontinuous reinforcement. For example, the filler material may include discontinuous whiskers, platelets, or particulates. The binder or filler material may include any useful binder or filler including, for example, silicon metal for silicon-based CMC materials, silicon metal with silicon carbide (SiC) reinforcing particles for silicon-based CMC materials, aluminum oxide (Al 2 O 3 ) particles in water/solvent carrier for alumina-based CMC materials, and the like. As another example, the filler material may include a continuous monofilament or multifilament weave. In some examples, the CMC may include a SiC/SiC CMC, or an oxide/oxide CMC. For example, a SiC/SiC or oxide/oxide CMC component may be joined to a metal or alloy component or another SiC/SiC or oxide/oxide CMC component. 
     First component  12 A defines at least one joining region  16 A defining a joint surface  18 A. Similarly, second component  12 B defines at least one joining region  16 B defining a joint surface  18 B. In some examples, first and second joint surfaces  18 A and  18 B (also referred to as “joint surfaces  18 A and  18 B”) may define complementary shapes.  FIG.  1 A  illustrates joint surfaces  18 A and  18 B as defining substantially simple curved surfaces. In other examples, joint surfaces  18 A and  18 B may define other, simpler shapes, such as flat shapes, or more complex shapes, such as complex curves, overhangs, undercuts, apertures, annuluses, or the like. In some instances, each of joint surfaces  18 A and  18 B may include an inset that extends beyond a respective inner plane of component  12 A or outer plane of component  12 B. 
     Components  12 A and  12 B are positionable such that joining regions  16 A and  16 B are adjacent to each other and define a joint region (not shown in  FIG.  1 A ). The joint region may include any kind of simple or complex joint, including, for example, at least one of a bridle joint, a butt joint, a miter joint, a dado joint, a groove joint, a tongue and groove joint, a mortise and tenon joint, a birdsmouth joint, a halved joint, a biscuit joint, a lap joint, a double lap joint, a dovetail joint, or a splice joint. Consequently, joining regions  16 A and  16 B may have any corresponding geometries to define the surfaces of the joint region. For example, for a mortise and tenon joint, first component  12 A may define a mortise (a cavity) and second component  12 B may define a tenon (a projection that inserts into the mortise). As another example, for a splice joint, first component  12 A may define a half lap, a bevel lap, or the like, and second component  12 B may define a complementary half lap bevel lap, or the like. 
     In some examples, although not shown in  FIG.  1 A , assembly  10  may include a clamp, press, or other mechanism for exerting pressure between joining regions  16 A and  16 B during joining. The pressure between joining regions  16 A and  16 B may facilitate formation of the joint, e.g., by helping to at least one of maintain a gap at the joint region, to promote flow or migration of a solid retainer material of mechanical interlock  14  or a binder around the solid retainer material of mechanical interlock  14 , and to evacuate any gases or porosity in the solid retainer material or the binder, which may reduce porosity in the joint. 
       FIG.  1 B  is a conceptual and schematic diagram illustrating a partial view of an example system including the assembly of  FIG.  1 A . Assembly  10  may be assembled as shown in  FIG.  1 B , with mechanical interlock  14  disposed in a joint region  22  defined by joint surfaces  18 A and  18 B of joining regions  16 A and  16 B. While a single joint region  22  is shown in the example assembly of  FIG.  1 B , in other examples, components  12 A and  12 B may define a plurality of respective joint regions, and a solid retainer material may be introduced into respective joint regions of the plurality of joint regions to form mechanical interlock  14 . In some examples, different compositions of the solid retainer material may be introduced into different joint regions, or in different portions of the same joint region. 
     Mechanical interlock  14  may include a solid retainer material. The solid retainer material may include any solid material, such as a module or powder, that may form mechanical interlock  14  as discussed herein. The solid retainer material may be selected to provide sufficient strength and rigidity to mechanical interlock  14  to secure first component  12 A to second component  12 B or restrain first component  12 A relative to second component  12 B. Mechanical interlock  14  may be formed from any suitable metal, alloy, or ceramic for the particular joint conditions. 
     In some examples, the solid retainer material is a superalloy having a high mechanical strength. For example, mechanical interlock  14  may experience high sheer forces created between component  12 A and component  12 B, such that a superalloy having a high sheer strength at elevated temperatures may be used to ensure sufficient strength to join components  12 A and  12 B. Example superalloys that may be used may include, but are not limited to, Ni-based superalloys, Co-based superalloys, Fe-based superalloys, and the like. In some examples, the solid retainer material may have a sheer strength greater than about 20,000 pounds per square inch (psi) at room temperature, such as greater than about 50,000 psi. For example, MarM Ni-based superalloy has a shear strength at room temperature of about 64,000 psi and a shear strength at 900 F of about 62,000 psi. In some examples, the solid retainer material includes a metal or alloy that melts at a temperature of greater than about 1315° C. (about 2400° F.). In some examples, the solid retainer material may include a metal or alloy substantially similar to or substantially the same as (e.g., the same or nearly the same) the alloy in first component  12 A, second component  12 B, or both. 
     In some examples, the solid retainer material is a ceramic-based material having high stability at high temperatures. For example, mechanical interlock  14  may experience high temperatures in a gas turbine engine environment, such that a ceramic-based material having high stability may be used to ensure sufficient strength at high temperatures to join component  12 A and  12 B. Example ceramic-based materials that may be used include, but are not limited to, transition metal borides, carbides, nitrides, oxides, and the like. 
     In the example of  FIGS.  1 A- 1 C , mechanical interlock  14  includes a plurality of solid retainer modules  24 . Each solid retainer module  24  may be configured to fit through opening  20  into joint region  22  and, individually as solid retainer module  24  or collectively as the plurality of solid retainer modules  24 , secure or restrain first component  12 A to second component  12 B. In some examples, each of the plurality of solid retainer modules  24  may have a predetermined shape. The predetermined shape may correspond to a portion, such as one or both of joint surfaces  18 A or  18 B, of a shape of joint region  22 . As described above, joint region  22  may include a relatively simple geometry as shown in  FIG.  1 A , or may include a more complex geometry, e.g., multiple planes or surfaces, complex curves, overhangs, undercuts, internal cavities, or the like. Accordingly, solid retainer modules  24  may be cut, machined, or formed into a relatively simple shape, or a more complex, e.g., including curvature, angles, apertures, or the like to form mechanical interlock  14 . Regardless of the complexity of the shape of mechanical interlock  14  and depending upon the geometry of joint region  22 , solid retainer modules  24  may include a substantially two-dimensional shape (e.g., a plane) or a three-dimensional shape (e.g., including curvature, planes at angles with respect to one another, and the like). 
     The plurality of solid retainer modules  24  may have a variety of sizes and shapes. In some examples, each solid retainer module  24  may be sized to permit placement of the solid retainer module  24  in joint region  22  with a small clearance to permit movement of each solid retainer module  24  through joint region  22 . For example, dimensions of a geometry (e.g., a diameter, length, width, height, etc.) of each solid retainer module  24  may be slightly smaller than dimensions of a geometry of joint region  22 , such that the plurality of solid retainer modules  24  may be inserted through opening  20  (or multiple openings) and positioned in joint region  22 . In some examples, the plurality of solid retainer modules  24  may have a diameter greater than about one millimeter and/or less than about 95% of a diameter of joint region  22 , such as about 2.5 millimeters. In some instances, a diameter of the plurality of solid retainer modules  24  may be dependent on a geometry of joint region  22 . For example, a smallest dimension of joint region  22  may restrict a size of the plurality of retainer modules, such that nonuniformities of joint region  22  or an asymmetrical shape of the plurality of solid retainer modules  24  may limit an ability of the plurality of solid retainer modules  24  to move within joint region  22 . While shown as a same size, in some instances, the plurality of solid retainer modules may include two or more different sizes. For example, a first plurality of solid retainer modules may have a first size corresponding to a dimension of joint region  22 , while a second plurality of solid retainer modules may have a second size corresponding to gaps between adjacent solid retainer modules of the first plurality of solid retainer modules, such that a volume of joint region  22  may be include large solid retainer modules while being more fully filled with solid retainer material than large solid retainer modules alone. Shapes that may be used for solid retainer modules  24  may include, but are not limited to, spheres, cylinders, barrel-shapes, ovular spheres, blocks, cones, and the like. Various shapes and sizes of solid retainer modules  24  may be discussed further in  FIGS.  3 A- 3 C  below. 
     In the example of  FIGS.  1 A- 1 C , the solid retainer material of mechanical interlock  14  is not bulk heated above a melting temperature of the solid retainer material to form mechanical interlock  14 . For example, unlike assemblies with mechanical interlocks formed from melted metals or alloys contained within a joint region, the solid retainer material of mechanical interlock  14  does not melt during formation of mechanical interlock  14 . As such, mechanical interlock  14  may include a solid retainer material that has substantially the same microstructure as the solid retainer material prior to insertion into joint region  22 . By utilizing mechanical interlock  14  having a solid retainer material, metals, alloys, and ceramics with desirable mechanical and chemical properties (e.g., high temperature oxidation resistance) may be utilized in a joining technique to join first component  12 A and second component  12 B. 
       FIG.  1 C  is a conceptual and schematic diagram illustrating a partial sectional and exploded view of region A of the system of  FIG.  1 B . A joint surface may be defined by joint region  22 , for example, a surface of one or both of first or second joining regions  16 A or  16 B. Mechanical interlock  14  secures first component  12 A to second component  12 B or restrains first component  12 A relative to second component  12 B. For example, the shape and geometry of mechanical interlock  14  (for example, substantially conforming to a portion or dimension of joint region  22 , such as joint surfaces  18 A and/or  18 B) may mechanically lock or secure a portion of first component  12 A relative to a respective portion of second component  12 B. For example, first component  12 A and second component  12 B may be limited in movement in at least one direction. In some examples, the plurality of solid retainer modules  24  may at least partially surround at least one of first component  12 A or second component  12 B. For example, mechanical interlock  14  may surround a perimeter subtending an angle greater than 180°, or greater than 210°, or greater than 240°, or greater than 270°, or greater than 300°, or substantially 360° (for example, within 1°, 5°, or 10° of 360°) about a central axis defined respectively by first component  12 A or second component  12 B. In some examples, mechanical interlock  14  may form a segmented ring, or a segmented sleeve, surrounding one or both of components  12 A or  12 B. In some examples, the mechanical interlock may be exterior to an exterior surface defined by one of components  12 A or  12 B, and interior to an interior surface defined by the other of components  12 A or  12 B. For example, in the examples shown in  FIGS.  1 A- 1 C , the solid retainer material (and mechanical interlock  14  formed from the solid retainer material) surrounds and is exterior to (radially outward of) second component  12 B, while being interior to (radially inward of) first component  12 A. However, any suitable configuration of mechanical interlock  14  relative to components  12 A and  12 B that secures components  12 A and  12 B together may be used. 
     Mechanical interlock  14  ultimately formed from the plurality of solid retainer modules  24  may possess sufficient mechanical strength and high temperature oxidation resistance to be utilized in a high temperature mechanical system, such as a nozzle guide vane in a gas turbine engine. 
     In some examples, a composite mechanical interlock securing two or more components may be formed a solid retainer material and one or more binder materials without melting the solid retainer material.  FIG.  2 A  is a conceptual and schematic diagram illustrating an exploded view of an example assembly  30  for joining a first component  32 A and a second component  32 B by inserting a solid retainer material and a binder to form a composite mechanical interlock  34 . Unless otherwise specified, first component  32 A, second component  32 B, a first joining region  36 A, a second joining region  36 B, a first joint surface  38 A, a second joint surface  38 B, and a opening  40  may correspond to first component  12 A, second component  12 B, first joining region  16 A, second joining region  16 B, first joint surface  18 A, second joint surface  18 B, and opening  20  of  FIGS.  1 A- 1 C . 
       FIG.  2 B  is a conceptual and schematic diagram illustrating a partial view of an example system including the assembly of  FIG.  2 A . Composite mechanical interlock  34  includes a plurality of solid retainer modules  44  and a binder  46 . The plurality of solid retainer modules  44  may correspond to (e.g., have similar compositions, microstructural properties, and/or macrostructural properties as) the solid retainer modules  24  of  FIGS.  1 A- 1 C . Composite mechanical interlock  34  may have a shape that at least partially conforms to joint region  42 . 
     Binder  46  may include one or more of a putty or a paste. In some examples, binder  46  includes a braze material. In some examples, the braze material may include a Ni-based or Co-based wide gap braze alloy. The braze material may include greater amounts of alloying elements that some other braze materials used in braze foils, which may contribute to improved mechanical properties, chemical properties, or both compared to some other braze materials used in braze foils. For example, the braze material may possess sufficient mechanical strength and high temperature oxidation resistance to be used in a nozzle guide vane in a gas turbine engine. 
     In some examples, the braze material may include both a braze alloy powder (a low-melt powder composition) and a superalloy powder (a high-melt powder composition). The low-melt alloy powder composition is an alloy, or a mixture of alloys, that substantially melts below a braze or joining temperature (hence the name “low-melt” or “braze powder”). In contrast, the high-melt alloy powder composition is an alloy, or a mixture of alloys, that remains substantially unmelted at the braze temperature, because the composition has a melting temperature above the braze temperature (hence the name “high-melt” or “superalloy powder”). In some implementations, the braze alloy powder and the superalloy powder may have specific powder mesh sizes, and may be produced by induction melting the braze alloy or the superalloy powder, respectively, in vacuum or an argon atmosphere, followed by argon gas atomization. Each individual powder component used in the braze material may be analyzed to confirm the particle size and chemical compositions. 
     In some examples, the low-melt powder composition includes an alloy or a mixture of alloys that melt at a temperature below about 1260° C. (about 2300° F.). In some examples the low-melt alloy powder comprises a mixture of two or more low-melt alloys. In some examples, the high-melt alloy powder composition may include a single high-melt alloy or a mixture of alloys that melts at a temperature of greater than about 1315° C. (about 2400° F.). In some examples, the high-melt powder composition may include an alloy or mixture of alloys with a chemistry that is the similar to or substantially the same (e.g., the same or nearly the same) as the alloy in first component  12 A, second component  12 B, or both. 
     The low-melt powder composition and the high-melt powder composition may be combined in any selected ratio. In some examples, the braze material may include a powder mixture consisting of between about 20 wt. % and about 80 wt. % low-melt powder composition and a balance high-melt powder composition (a ratio of between about 1:4 and about 4:1 low-melt powder:high-melt powder). In some cases, braze alloy powder may be a mixture of more than one braze alloy, which are all powder. 
     In selecting the proportions of components used in the braze material, higher weight percentages of high-melt powder may provide better mechanical properties in view of their reduced levels of boron, silicon, or both. Conversely, higher percentages of low-melt powders may provide improved braze flow. A proper balance between mechanical properties and braze flow should be selected, for example, to promote flow of the braze material to ultimately at least partially conform to joint region  42 , while yet retaining sufficient strength or rigidity to mechanically secure components  32 A and  32 B relative to each other. The at least softened material may flow, migrate, or otherwise at least partially occupy joint region  42 , and on cooling, form a mechanical interlock in joint region  42 . 
     Thus, the braze material can be introduced into joint region  42  with the plurality of solid retainer modules  44  with the ability to change shape or “morph” when heated from a pliable or ductile green state into a state that further softens and has the ability to substantially conform to the shape of joint region  42  or a cavity or channel in which the braze material is placed and the plurality of solid retainer modules  44 . Such deforming of the braze material may be accomplished at a temperature well below the melting point of components  32 A or  32 B, for example, without the braze material itself melting into a full liquid state (in contrast with bi-casting, which may require a liquid molten state). However, in other examples, while the braze material may be molten or heated to a liquid state, the plurality of solid retainer modules  44  and components  32 A or  32 B themselves may be maintained in a solid state, retaining the integrity of the plurality of solid retainer modules  44  and components  32 A and  32 B. In some examples, as described elsewhere in the disclosure, the braze material may be formed into multiple sections placed adjacent to each other in joint region  22 . In such a configuration, the multiple sections will securely bond and fuse to each other during a high temperature furnace operation. 
     In some examples, the melting characteristics of the braze material may change in response to high temperature exposure. For example, the braze material may include a relatively small percentage of a low melting component, for example, brazing powder, and a relatively higher percentage of a high melting component, for example, superalloy. The low melting component may include an alloy additive that depresses the melting point of the low melting component, causing the low melting component to liquefy at this lower temperature, causing the braze material to soften and slip (and unite if more than one strip is used) during the furnace operation. However, the alloy addition that depresses the melting point of the low melting component may diffuse during the furnace operation (or during a post-furnace diffusion heat treatment) into the larger volume of high melting component, for example, superalloy. Such diffusion may raise the re-melt temperature of the mechanical interlock ultimately formed from the braze material, such that composite mechanical interlock  34  (morphed and fused) formed from the braze material transforms into a rigid metallic structure, (for example a “ring”) after the furnace operation and when in subsequent use at high temperature operating conditions. Thus, after the completion of the thermal cycle (and after an optional diffusion heat treat cycle) the braze material may transform into an integrally shaped and consolidated mechanical interlock (in some examples, a “ring”) trapped in cavities or channels bridging between components  32 A and  32 B. The mechanical interlock formed from the braze material may thus function as a high strength, high temperature capable (closely conforming) structural member with material properties similar to a high temperature superalloy, for example, superalloy constituent(s) used in the formulation of the braze material. 
       FIG.  2 C  is a conceptual and schematic diagram illustrating a partial sectional and exploded view of region A of the system of  FIG.  2 B . In some examples, one or both first joint surface  38 A or second joint surface  38 B may include an adhesion resistant coating. The adhesion resistant coating may resist adherence or metallurgical bonding of the mechanical interlock formed from the brazing material to surfaces of joint region  42 . A joint surface defined by joint region  42 , for example, a surface of one or both of first or second joining regions  36 A or  36 B, may be coated with an adhesion resistant coating. For example, one or both of joint surfaces  38 A or  38 B of joint region  42  may be respectively coated with the adhesion resistant coating. At least a portion of the adhesion resistant coating may act as a leave-in-place “stop-off”, substantially preventing the braze material (or the at least softened material formed by heating the braze material, or the composite mechanical interlock  34  formed by cooling the at least softened material) from adhering to surfaces defined by joint region  42 , for example, joint surfaces  38 A and  38 B. In some examples, the adhesion resistant coating present before, during, and after forming mechanical interlock  34  avoids or substantially prevents introducing a gap (as contrasted with a stop-off removed after application). Thus, the adhesion resistant coating may result in a line-on-line fit or connection between components  32 A and  32 B and composite mechanical interlock  34  ultimately formed from the braze material and the plurality of solid retainer modules  44 , without allowing the braze material to form a metallurgical bond or braze joint with components  32 A and  32 B. 
     Further discussion of materials and techniques for a braze material and an adhesion resistant coating may be described in U.S. Patent Application Publication No. 2019/0275617 entitled “Techniques and Assemblies for Joining Components” and filed on Mar. 6, 2019, which is incorporated by reference herein in its entirety. 
     In some examples, a monolithic mechanical interlock securing two or more components may be formed from a sintered solid retainer material without melting the solid retainer material.  FIG.  3 A  is a conceptual and schematic diagram illustrating an exploded view of an example assembly  50  for joining a first component  52 A and a second component  52 B by inserting a solid retainer material and a binder into a joint region  62  to form a monolithic mechanical interlock  54 . Unless otherwise specified, first component  52 A, second component  52 B, a first joining region  56 A, a second joining region  56 B, a first joint surface  58 A, a second joint surface  58 B, and joint region  62  may correspond to first component  12 A, second component  12 B, first joining region  16 A, second joining region  16 B, first joint surface  18 A, second joint surface  18 B, and joint region  22  of  FIGS.  1 A- 1 C . In the example of  FIG.  3 A , first component  52 A includes an opening  60  that is smaller than opening  20  of  FIG.  1 A . For example, rather than inserting solid retainer modules, such as the plurality of solid retainer module  24  of  FIGS.  1 A- 1 C , mechanical interlock  54  may be formed from solid retainer particles using injection molding, as will be described further below. As such, opening  60  may have a smaller size than opening  20  of  FIG.  1 A , as opening  60  does not have to accommodate the relatively larger solid retainer modules of the plurality of solid retainer modules  24 . 
       FIG.  3 B  is a conceptual and schematic diagram illustrating a partial view of an example system including the assembly of  FIG.  3 A . Monolithic mechanical interlock  54  may be an injection molded mechanical interlock that includes a sintered solid retainer material  64 . Monolithic mechanical interlock  54  may have a shape that at least partially conforms to joint region  62 . The sintered solid retainer material  64  may correspond to (e.g., have similar compositions and/or microstructural properties as) the solid retainer modules  24  of  FIGS.  1 A- 1 C . The sintered solid retainer material  64  may be formed from solid retainer powder, as will be described further in  FIGS.  4 D and  5 C  below. 
       FIG.  3 C  is a conceptual and schematic diagram illustrating a partial sectional and exploded view of region A of the system of  FIG.  3 B . In some instances, a diameter of sintered solid retainer material  64  may be substantially the same as a diameter of joint region  62 , while in other examples, sintered solid retainer material  64  may be smaller than a diameter of joint region  62 , such as in examples in which sintering of a solid retainer material preform formed by debinded solid retainer powder shrinks in one or more dimensions to form a denser sintered solid retainer material  64  having a reduced size in at least one dimension. 
     In some examples, mechanical interlocks discussed herein may be formed from a plurality of solid retainer modules having relatively simple geometries. For example, a joint region for various components may have a relatively standard, consistent, and/or symmetrical size, such that a plurality of solid retainer modules having a relatively standard or uniform size or shape may be used to form the mechanical interlock.  FIG.  4 A  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly  70  for joining a first component  72 A and a second component  72 B by inserting generically shaped solid retainer modules  76  into a joint region  74  to form a mechanical interlock. As illustrated in  FIG.  4 A , each solid retainer module  76  of the plurality of solid retainer modules  76  has a spherical shape with a diameter slightly smaller than a dimension of joint region  74  between first component  72 A and second component  72 B. Such simple geometries of the plurality of solid retainer modules  76  may fit a wide variety of joint region shapes. 
     In some examples, mechanical interlocks discussed herein may be formed from relatively complex geometries. For example, a joint region may have a relative complex, unique, and/or asymmetrical shape, such that a plurality of solid retainer modules having a relatively unique shape may be used to form the mechanical interlock.  FIG.  4 B  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly  80  for joining a first component  82 A and a second component  82 B by inserting specifically shaped solid retainer modules  86  into a joint region  84  to form a mechanical interlock. As illustrated in  FIG.  4 B , each solid retainer module  86  of the plurality of solid retainer modules  86  has a domed cylindrical shape with a diameter slightly smaller than a dimension of joint region  84  between first component  82 A and second component  82 B. The cylindrical shape of each solid retainer module  86  may increase a volume of solid retainer material in joint region  84  as compared to, for example, a spherical shape, while the domed shape of each solid retainer module  86  may enable the solid retainer module  86  to advance more easily through joint region  84  as compared to, for example, a strictly cylindrical shape. Such complex geometries of the plurality of solid retainer modules  86 , alone or in combination with a shape of joint region  84 , may provide enhanced strength compared to shapes of solid retainer modules that are not as specific to a shape of the joint region. 
     In some examples, mechanical interlocks discussed herein may be composite mechanical interlocks formed from relatively large solid retainer modules and a binder. For example, a joint region for components may form an interface between two environments. A plurality of solid retainer modules, while providing sufficient strength between the components, may permit air to pass through the joint region between the two environments. By including a binder with the plurality of solid retainer modules to form the composite mechanical interlock, the composite mechanical interlock may seal the two environments and/or provide additional support or strength to the composite mechanical interlock.  FIG.  4 C  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly  90  for joining a first component  92 A and a second component  92 B by inserting a plurality of solid retainer modules  96  and a binder  98  into a joint region  94  to form a composite mechanical interlock.  FIG.  4 C  may illustrate a mechanical interlock prior to curing binder  98 . As illustrated in  FIG.  4 C , each solid retainer module  96  of the plurality of solid retainer modules  96  is at least partially surrounded by binder  98 . Binder  98  contacts the plurality of solid retainer modules  96  and, at least prior to solidifying binder  98 , one or more surfaces of components  92 A and  92 B corresponding to joint region  94 . Once cured, binder  98  and the plurality of solid retainer modules  96  may form the composite mechanical interlock, such as composite mechanical interlock  34  of  FIGS.  2 A- 2 C . Such composite mechanical interlocks may provide a seal to joint region  94 , as binder  98  may fill in voids that previously provided a path for fluids to pass between components  92 . 
     In some examples, mechanical interlocks discussed herein may be monolithic mechanical interlocks formed from relatively small (e.g., powders) solid retainer particles and a binder. For example, solid retainer powders may have advantageous properties, such as high strength, that may be integrated into a mechanical interlock without exposing the solid retainer powders to high temperatures associated with a melting point of the solid retainer powders.  FIG.  4 D  is a conceptual and schematic diagram illustrating a cross-sectional top view of an example assembly  100  for joining a first component  102 A and a second component  102 B by inserting binder  108  having solid retainer particles  106  into a joint region  104  to form a mechanical interlock.  FIG.  4 D  may illustrate joint region  104  prior to debinding binder  108  and sintering solid retainer particles  106 , such that the mechanical interlock is not yet formed. As illustrated in  FIG.  4 D , solid retainer particles  106  are surrounded by binder  108  and distributed throughout the joint region. Once binder  108  has been debinded and the solid retainer particles  106  sintered, the solid retainer particles  106  may form a monolithic mechanical interlock that includes solid retainer material distributed throughout joint region  104 . For example, the solid retainer particles  106  may form a continuous phase through joint region  104 . 
     Solid retainer particles  106  may have a variety of shapes including, but not limited to, spheres, random-shapes, blocks, and the like. Solid retainer particles  106  may have a variety of sizes including, but not limited to, about 1 micrometer to about 1 millimeter, such as about 10 micrometers to about 100 micrometers. Solid retainer particles  106  may have a variety of distributions (e.g., a ratio between solid particles  106  to binder  108 ) including, but not limited to, about 4:1 to about 20:1. For example, the distribution of solid retainer particles  106  may be related to a desired viscosity and/or stability of solid retainer particles  106  and binder  108 . In some examples, solid retainer particles  106  may have a composition similar to the plurality of solid retainer modules  24  and  44  discussed in  FIGS.  1 B and  1 C  and  FIGS.  2 B and  2 C , respectively. 
     Binder  108  may be selected to hold solid retainer particles  106  together and/or provide solid retainer particles  106  with fluidity, such that solid retainer particles  106  may be relatively evenly distributed in the joint region. Binder  108  may include a filler and a structural polymer. A variety of metal or ceramic injection binders  108  may be used including, but not limited to: polymer-based binders, such as polyacetal, polyamide, or methyl cellulose fillers and polyethylene, polybutene, poly(ethylene-co-vinyl acetate), polystyrene, poly(methyl methacrylate), poly(ethylene glycol), or poly(vinyl acetate) structural polymers; wax-based binders, such as paraffin-based wax, microcrystalline wax, synthetic hydrocarbon wax, or oxidized polyethylene wax fillers and polyethylene, polybutene, poly(ethylene-co-vinyl acetate), polystyrene, poly(methyl methacrylate), poly(ethylene glycol), or poly(vinyl acetate) structural polymers; combinations of waxes and polymers, and the like. In some examples, binder  108  may be selected to be a powder at ambient temperature and a liquid at relatively low processing temperatures, such as temperatures lower than a melting point of solid retainer particles  106 . In some examples, binder  108  may include additives, such as dispersants (e.g., to increase wettability of solid retainer particles  106 ), stabilizers (e.g., to reduce agglomeration of solid retainer particles  106 ), plasticizers (e.g., to increase flow of solid retainer particles  106  and/or binder  108 ), lubricants (e.g., to reduce interaction between solid retainer particles  106  and binder  108 ), and the like. 
       FIG.  5 A  is a flow diagram illustrating an example technique for forming a mechanical interlock using a solid retainer material to join components. The technique of  FIG.  5 A  will be described with reference to assembly  10  of  FIGS.  1 A- 1 C  for purposes of illustration only. It will be appreciated that the technique of  FIG.  5 A  may be performed with a different assembly or system, or that assembly  10  may be used in a different joining technique. 
     The technique of  FIG.  5 A  may optionally include forming opening  20  and/or joint surfaces  18 A and  18 B of first component  12 A and second component  12 B, respectively ( 110 ). As described elsewhere in the disclosure, the geometry of joint region  22  may depend on the type of joint defined by joint surfaces  18 A and  18 B and may include, for example, a bridle joint, a butt joint, a scarf joint, a miter join, a dado joint, a groove joint, a tongue and groove joint, a mortise and tenon joint, a birdsmouth joint, a halved joint, a biscuit joint, a lap joint, a double lap joint, a dovetail joint, or a splice joint. 
     Although not shown in  FIG.  5 A , in some examples, joint surfaces  18 A and  18 B of components  12 A and  12 B, respectively, may be inspected and cleaned, for example, before the positioning ( 112 ). The cleaned joint surfaces  18 A and  18 B may produce a more uniform joint than uncleaned joint surfaces. The technique of  FIG.  5 A  includes positioning components  12 A and  12 B to define joint region  22  ( 112 ). For example, as shown in  FIGS.  1 B and  1 C , components  12 A and  12 B may be positioned so that joining regions  16 A and  16 B are near each other. 
     The technique of  FIG.  5 A  also includes inserting a solid retainer material into joint region  22  through opening  20  to form mechanical interlock  14  ( 114 ). The solid retainer material may include a plurality of solid retainer modules  24 . The plurality of solid retainer modules  24  may be inserted in joint region  22  such that the plurality of solid retainer modules  24  form mechanical interlock  14  between first component  12 A and second component  12 B. The technique of  FIG.  5 A  includes sealing opening  20  to retain the plurality of solid retainer modules  24  within joint region  22  ( 116 ). For example, opening  20  may be brazed or welded to prevent the plurality of solid retainer modules  24  from passing through opening  20 . 
     Thus, the example technique of  FIG.  5 A  may be used to form mechanical interlock  14  between components  12 A and  12 B from the plurality of solid retainer modules  24  in assembly  10  of  FIGS.  1 A- 1 C , without melting the mechanical retainer material. Although  FIG.  1 A  illustrates a simplified conceptual and schematic view of an example first component  12 A, an example second component  12 B, and an example mechanical interlock  14 , in other examples, example assemblies may include components and a mechanical interlock defining a more complication geometry. 
       FIG.  5 B  is a flow diagram illustrating an example technique for forming a composite mechanical interlock using a solid retainer material to join components. The technique of  FIG.  5 B  will be described with reference to assembly  30  of  FIGS.  2 A- 2 C  for purposes of illustration only. It will be appreciated that the technique of  FIG.  5 B  may be performed with a different assembly or system, or that assembly  30  may be used in a different joining technique. As described in  FIG.  5 A  above, the technique of  FIG.  5 B  may optionally include forming opening  40  and/or joint surfaces  38 A and  38 B of first component  32 A and second component  32 B, respectively ( 120 ), and positioning components  32 A and  32 B to define joint region  42  ( 122 ). 
     In some examples, such as examples in which composite mechanical interlock  34  includes a braze material, the example technique of  FIG.  5 B  includes optionally coating a joint surface of joint region  42  defined by first and second components  32 A and  32 B with an adhesion resistant coating (not shown). The coating technique may include physical vapor deposition, chemical vapor deposition, plasma deposition, spraying, deposition of a liquid, marker, or putty, atmospheric exposure at high temperatures, or any other suitable coating technique. In some examples, the example technique may not include the coating step, and instead, pre-coated components  32 A and  32 B may be used. 
     The technique of  FIG.  5 B  includes inserting a solid retainer material, such as the plurality of solid retainer modules  44 , and binder  46  into joint region  42  through opening  40  ( 124 ). Binder  46  may be disposed in joint region  42  such that binder  46  contacts respective joint surfaces of joint region  42 , for example, joint surfaces  38 A and  38 B. In some examples, a clamp, press, or other mechanism may be used to compress the braze material between joining regions  36 A and  36 B to cause intimate contact between joint surfaces  38 A and  38 B and surfaces of binder  46  and, correspondingly, composite mechanical interlock  34 , although intimate contact between joint surfaces  38 A and  38 B and surfaces of composite mechanical interlock  34  is not required. As described in  FIG.  5 B , the technique of  FIG.  5 A  includes sealing opening  20  to retain the plurality of solid retainer modules  24  within joint region  22  ( 126 ). 
     The technique of  FIG.  5 B  includes solidifying binder  46  around the plurality of solid retainer modules  44  to form composite mechanical interlock  34  ( 128 ). For example, such as examples in which binder  46  is a braze material, the braze material may be melted and solidified around the plurality of solid retainer modules  44  to form composite mechanical interlock  34 . 
     Thus, the example technique of  FIG.  2    may be used to form a mechanical interlock between components  32 A and  32 B from the plurality of solid retainer modules  44  and binder  46  in assembly  10  of  FIGS.  2 A- 2 C , without melting the mechanical retainer material. Although  FIGS.  2 A- 2 C  illustrate a simplified conceptual and schematic view of an example first component  32 A, an example second component  32 B, and an example composite mechanical interlock  34 , in other examples, example assemblies may include components and a mechanical interlock defining a more complicated geometry. 
       FIG.  5 C  is a flow diagram illustrating an example technique for joining components including inserting a solid material. The technique of  FIG.  5 C  will be described with reference to assembly  50  of  FIGS.  3 A- 3 C  and assembly  100  of  FIG.  4 D  for purposes of illustration only. It will be appreciated that the technique of  FIG.  5 C  may be performed with a different assembly or system, or that assembly  50  or assembly  100  may be used in a different joining technique. As described in  FIG.  5 A  above, the technique of  FIG.  5 C  may optionally include forming opening  60  and/or joint surfaces  58 A and  58 B of first component  52 A and second component  52 B, respectively ( 130 ), and positioning components  52 A and  52 B to define joint region  62  ( 132 ). 
     The technique of  FIG.  5 C  includes inserting a solid retainer powder (e.g., solid retainer particles  106 ) and a binder (e.g., binder  108 ) into joint region  104  through an opening ( 134 ). For example, as illustrated in  FIG.  4 D , solid retainer particles  106  may be dispersed in binder  108 , such that the mixture of solid retainer particles  106  and binder  108  may be injected through an opening into joint region  104 . The mixture of solid retainer particles  106  and binder  108  may be injected using any suitable metal injection molding and/or ceramic injection molding techniques. For example, binder  108  may be heated prior or subsequent to injection of solid retainer particles  106  and binder  108  to flow solid retainer particles  106  and binder  108  through the joint region. 
     The technique of  FIG.  5 C  includes debinding binder  108  from solid retainer particles  106  to form a solid retainer material preform ( 136 ). For example, depending on binder  108 , debinding may involve any of thermal debinding (e.g., heating binder  108  to decompose binder  108  and remove binder  108  using gases), solvent debinding (e.g., contacting binder  108  with a solvent to dissolve binder  108  and remove the dissolved binder  108 ), and/or catalytic debinding (e.g., contacting binder  108  with a gaseous catalyst to decompose binder  108  and remove binder  108  using gases). 
     The technique of  FIG.  5 C  include sintering the solid retainer material preform to form monolithic mechanical interlock  54  ( 138 ). For example, assembly  100  may be placed into a furnace and heated to a sintering temperature configured to joint solid retainer particles  106  to form monolithic mechanical interlock  54  of  FIGS.  3 A- 3 C . The sintering temperature of solid retainer particles  106  may be lower than a melting temperature of solid retainer particles  106 . 
     As described in  FIG.  5 A , the technique of  FIG.  5 C  includes sealing opening  60  ( 140 ). While sealing the opening is illustrated as being performed after the solid retainer particles are sintered, in some instances, the opening may be sealed prior to solid retainer particles  106  being sintered, such as after binder  108  has been removed. 
     Various examples have been described. These and other examples are within the scope of the following claims.