Patent Application
20210146459
The present disclosure relates generally to applying braze powders to surfaces, and more particularly to a printing method to selectively deposit braze powders at one or more predetermined locations on a surface.
Gas turbine engines include a compressor, combustor and turbine in flow series along a common shaft. Compressed air from the compressor is mixed with fuel in the combustor to generate hot combustion gases that rotate the turbine blades and drive the compressor. In a conventional turbine compressor, turbine blades may be fabricated separately from the rotor disk and then mechanically assembled such the turbine blades extend from machined slots on the disk; however, this configuration has the disadvantage of discontinuities between the blades and the disk. To eliminate such discontinuities, diffusion bonding techniques have been developed to bond the turbine blades to the disk to form a mechanically robust, monolithic component (a “turbine blisk”). Diffusion bonding is a solid-state bonding method, where elevated temperatures and typically high pressures are employed to obtain diffusion of atoms between mating components, allowing for formation of a thermally-stable metallurgical bond. Various gas turbine engine components may benefit from diffusion bonding.
Diffusion bonding may be facilitated or improved by utilizing diffusion agents or braze materials, such as braze foils or powders, between the components to be joined. However, the bonding of components having complex surface geometries can present challenges with the use of such diffusion agents. For example, the use of braze foils may not be effective for irregular or discontinuous surfaces, and it may be difficult if not impossible to deposit consistent levels of braze powder on such surfaces using methods known in the art. In addition, conventional methods of braze powder application, which typically provide blanket surface coverage of costly braze alloys, may lead to waste and/or bonding problems when applied to complex or discontinuous surfaces.
The embodiments may be better understood with reference to the following drawing(s) and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views.
A printing method to selectively deposit braze powders at one or more predetermined locations on a surface has been developed.
Referring to
As illustrated, the surface 106 may be a discontinuous surface 114 comprising surface regions 106a separated by gaps or holes 116. In this example, the filament 102, and concomitantly the braze powders 110, are selectively deposited on the surface regions 106a. In other words, the filament 102 and the braze powders 110 may be deposited only on the surface regions 106a. The surface regions 106a may be coplanar, as shown. As explained below, the filament 102 is able to substantially hold its shape while deposited on the surface 106. Accordingly, due to the properties of the filament 102 and the selective deposition, neither the flowable carrier 108 nor the braze powders 110 are deposited into the gaps 114.
It should be understood that references to the nozzle 104 moving relative to the surface 106 may encompass any of the following situations: (1) the nozzle 104 moving while the surface 106 remains stationary; (2) the nozzle 104 remaining stationary while the surface 106 moves; and/or (3) the nozzle 104 moving while the surface 106 also moves. The relative motion of the nozzle 104 and the surface 106 may be electronically controlled in three-dimensions (along x- y- and/or z-axes), and thus a single layer and/or multiple layers of the filament 102 may be continuously or semi-continuously deposited (e.g., with starts and stops to accommodate a discontinuous pattern) onto the surface 106. This approach, which is sometimes referred to as 3D printing, fused deposition modeling (FDM), and/or additive manufacturing, can be carried out using a commercially available printer. Due to the relative motion of the nozzle and the surface, extrusion and/or deposition of the filament may occur at a rate from about 1 mm/s to about 1 m/s, or even faster. Typically, the nozzle 104 has an inner diameter in a range from about 50 microns to 1 mm. The inner diameter of the nozzle 104 may determine or at least influence the diameter of the extruded filament 102 and consequently the thickness of a deposited layer. Typically, the filament 102 and consequently the braze powders 110 deposited on the surface 106 span a height in a range from 50 microns to 600 microns (0.05-0.6 mm). In some cases, the height may range from 100 microns to 300 microns (0.1-0.3 mm).
The filament 102 may be highly loaded with braze powder 110. For example, the filament 102 may include the braze powder 110 in an amount of about 50 wt. % or greater, or about 70 wt. % or greater, with a balance or remainder being the flowable carrier 108 and optionally minor amounts of other additive(s). The amount of braze powder may lie in the range from about 50 wt. % to about 90 wt. %, or from 70 wt. % to about 90 wt. %. Accordingly, the filament 102 may include just enough of the flowable carrier 108 to allow for extrusion and printing, such as about 50 wt. % or less, or about 30 wt. % or less, or about 10 wt. % or less.
In some cases, it may be preferred that the filament 102 includes a lesser amount of braze powder 110. For example, the filament 102 may include braze powder 110 in an amount of about 50 wt. % or less, or about 30 wt. % or less. The amount of braze powder may lie in the range from about 10 wt. % to about 50 wt. % or from about 10 wt. % to about 30 wt. %, with a balance or remainder being the flowable carrier 108 and optionally minor amounts of other additive(s). In this case, the filament 102 may include a more substantial amount of the flowable carrier 108, which may promote ease of extrusion and printing, such as at least about 50 wt. %, at least about 70 wt. %, or at least about 90 wt. %.
As indicated above, the surface 106 is part of a first component 120 that may comprise a metal alloy, such as a nickel-base alloy, a titanium-base alloy, or an iron-base alloy. The metal alloy may be suitable for high temperature applications. For example, the first component 120 may be part of an airfoil, a combustion liner, or a heat shield of a gas turbine engine.
Accordingly, the braze powder 110 may comprise a braze alloy suitable for elevated temperature usage. For example, nickel-based braze alloys may be employed for high temperature service applications and may be used for bonding nickel-base alloys, such as nickel-base superalloys utilized in gas turbine engines. Suitable nickel-based braze alloys may include nickel alloyed with boron, chromium, manganese, and/or silicon. Titanium-based braze alloys may also be employed for high temperature service applications and may be suitable for bonding titanium-base alloys, such as titanium aluminides. Suitable titanium-based braze alloys may include titanium alloyed with copper, nickel and/or zirconium. Commercially available braze powder 110 may be employed. Iron-based braze alloys may be suitable for bonding iron-base alloys. The braze powder may include particles of a spheroidal, spherical, polygonal, elongated, irregular, or other morphology. Typically, the particles have a nominal size (e.g., width or diameter) in the range of tens or hundreds of microns.
The printing process may be carried out in a controlled environment (e.g., vacuum or an inert gas atmosphere) or in air. The printing process may entail heating. For example, for a flowable carrier 108 comprising a thermoplastic polymer, the nozzle 104 may be heated during extrusion to promote softening and/or melting (and thus flow) of the flowable carrier 108 during extrusion. The extrusion may thus be carried out at a temperature (“extrusion temperature”) at or above a softening and/or melting temperature of the flowable carrier 108 to ensure flowability during extrusion. In contrast, the braze powder 110 remains solid and is transported by the flowable carrier 108 during extrusion. Generally speaking, the extrusion temperature may lie in a range from about 150° C. to about 320° C., and more typically may be from about 160° C. to 220° C.
Depending on the properties of the flowable carrier 108, such as glass transition temperature, the surface 106 on which the filament 102 is deposited may also be heated. Heating of the deposition surface 106 may allow for control over cooling and solidification of the filament 102 once deposited. Typically, the surface 106 is at room temperature (e.g., from 18° C. to 25° C.) or is heated to a temperature in a range from 26° C. to 100° C.
After the extrusion, the filament 102 cools and the flowable carrier 108 solidifies, adhering the braze powder 110 to the surface 106 (e.g., surface regions 106a), thereby forming a prewet surface 128 for diffusion bonding, as illustrated in
The feedstock for extrusion may be solid pellets or a solid filament comprising a composite of the flowable carrier 108 and the braze powders 110. Suitable thermoplastic polymers for the flowable carrier 108 may include polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyethylene terephthalate (PET), thermoplastic polyurethane (TPU), high-impact polystyrene (HIPS), polyvinyl alcohol (PVA), nylon, or mixtures of these.
In another example, the extrusion may be carried out at room temperature (e.g., from 18° C. to 25° C.) with a flowable carrier 108 that is flowable at room temperature and does not require heating to induce flow, as described above. A filament 102 comprising such a flowable carrier 108 and the braze powder 110 may be forced through the nozzle 104 under an applied pressure at room temperature. The filament 102 preferably has a viscosity sufficient to maintain its shape while deposited on the surface 106, and may be viscoelastic to permit easy flow through the nozzle. The filament 102 comprising the flowable carrier 108 and the braze powder 110 may have a viscosity in a range from about 2,000 cP to about 5,000 cP at room temperature, in one example. The flowable carrier 108 may comprise a water-based or organic binder gel, such as Vitta-Braz Binder Gel (Vitta Corporation, Bethel, Conn.), which may comprise polymer(s) and water.
After depositing the filament 102 on the surface 106 in this example, where extrusion occurs at room temperature, the filament 102 may be heated to remove the flowable carrier 108 (e.g., by pyrolysis or vaporization) and/or the surface 106 may be heated to raise the temperature of the filament 102 to the desired pyrolysis or vaporization (evaporation) temperature. Suitable temperatures may lie in a range from about 100° C. to about 125° C. for water-based carriers 108, and may be higher depending on the composition of the flowable carrier 108. Generally speaking, the temperature may be no higher than the solidus of the braze powder 110, where the solidus is the highest temperature at which the braze powder is completely solid. During the heating, the flowable carrier 108 is removed and the braze powder 110 is adhered to the surface 106 (e.g., surface regions 106a), forming a prewet surface 128 for diffusion bonding, as illustrated in
Referring to
Returning to
Once metallurgically bonded together, the first component 120 and the second component 122 form a monolithic third component 132 comprising a homogeneous bonded interface 130 that may be substantially free of unwanted phases, defects, and/or porosity. In one example, the monolithic third component 128 comprises an airfoil, as described below. The first and second components 120,122 may have a single-crystalline or polycrystalline (e.g., equiaxed) microstructure. In other words, the first component 120 may be single-crystalline or polycrystalline, and the second component 122 may be single-crystalline or polycrystalline. When both the first and second components 120,122 have a single-crystalline structure, a directionally solidified microstructure may be obtained across the bonded interface 130. The method is applicable to nickel-base alloys, iron-base alloys, and titanium-base alloys, such as titanium aluminides.
Referring now to
To clarify the use of and to hereby provide notice to the public, the phrases “at least one of <A>, <B>, . . . and <N>” or “at least one of <A>, <B>, . . . <N>, or combinations thereof” or “<A>, <B>, . . . and/or <N>” are defined by the Applicant in the broadest sense, superseding any other implied definitions hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, . . . and N. In other words, the phrases mean any combination of one or more of the elements A, B, . . . or N including any one element alone or the one element in combination with one or more of the other elements which may also include, in combination, additional elements not listed. Unless otherwise indicated or the context suggests otherwise, as used herein, “a” or “an” means “at least one” or “one or more.”
While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible. Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations.
The subject-matter of the disclosure may also relate, among others, to the following aspects:
A first aspect relates to a printing method for selectively depositing braze powders on a surface, the method comprising: extruding a filament from a nozzle moving relative to a surface, the filament comprising a flowable carrier mixed with a braze powder; and as the nozzle moves, depositing the filament on the surface in a predetermined pattern defined by the motion of the nozzle relative to the surface, the braze powders thereby being deposited at one or more predetermined locations on the surface.
A second aspect relates to the method of the first aspect, wherein the predetermined pattern is a continuous pattern.
A third aspect relates to the method of the first or second aspect, wherein the predetermined pattern is a discontinuous pattern.
A fourth aspect relates to the method of any preceding aspect, wherein the surface is a discontinuous surface comprising surface regions separated by gaps, and wherein the filament and thus the braze powders are selectively deposited on the surface regions.
A fifth aspect relates to the method of any preceding aspect, wherein the surface is part of a first component comprising a metal alloy.
A sixth aspect relates to the method of any preceding aspect, wherein the first component comprises part of an airfoil, a combustion liner, or a heat shield of a gas turbine engine.
A seventh aspect relates to the method of any preceding aspect, wherein the braze powder comprises a nickel-based braze alloy, a titanium based-braze alloy, or an iron-based braze alloy.
An eighth aspect relates to the method of any preceding aspect, wherein the filament includes braze powder in an amount from about 50 wt. % to about 90 wt. %.
A ninth aspect relates to the method of any preceding aspect, wherein the flowable carrier comprises a thermoplastic polymer.
A tenth aspect relates to the method of the ninth aspect, wherein the thermoplastic polymer comprises polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyvinyl alcohol (PVA), and/or nylon.
An eleventh aspect relates to the method of any preceding aspect, wherein the extrusion is carried out at a temperature at or above a softening temperature and/or melting temperature of the flowable carrier.
A twelfth aspect relates to the method of the eleventh aspect, wherein, after the extrusion, the filament cools and solidifies, adhering the braze powder to the surface, thereby forming a prewet surface for diffusion bonding.
A thirteenth aspect relates to a method of diffusion bonding comprising: assembling a first component comprising the prewet surface of the twelfth aspect with a second component comprising a mating surface to form an assembly, the prewet surface contacting the mating surface; and exposing the assembly to a bonding temperature, thereby diffusion bonding the first component to the second component to form a monolithic third component comprising a bonded interface.
A fourteenth aspect relates to the method of any preceding aspect, wherein the extrusion is carried out at room temperature.
A fifteenth aspect relates to the method of any preceding aspect, wherein the flowable carrier has a viscosity sufficient to maintain a shape of the filament while deposited on the surface.
A sixteenth aspect relates to the method of any preceding aspect, wherein the flowable carrier comprises an aqueous or organic binder gel.
A seventeenth aspect relates to the method of any preceding aspect, wherein, after depositing the filament on the surface, heating the filament to remove the flowable carrier and adhere the braze powder to the surface, forming a prewet surface for diffusion bonding.
An eighteenth aspect relates to the method of the seventeenth aspect, wherein heating the filament to remove the flowable carrier comprises pyrolyzing or evaporating the flowable carrier.
A nineteenth aspect relates assembly of the seventeenth or eighteenth aspects, wherein the heating is carried out in a vacuum or an inert gas atmosphere.
A twentieth aspect relates to a method of diffusion bonding comprising: assembling a first component comprising the prewet surface of the seventeenth aspect with a second component comprising a mating surface to form an assembly, the prewet surface contacting the mating surface; and heating the assembly to a bonding temperature, thereby diffusion bonding the first component to the second component to form a monolithic third component comprising a bonded interface.
In addition to the features mentioned in each of the independent aspects enumerated above, some examples may show, alone or in combination, the optional features mentioned in the dependent aspects and/or as disclosed in the description above and shown in the figures.
