Patent Description:
Some articles formed from superalloys include equiaxed, directionally solidified, or a single crystal alloys and are formed using casting. Replacement of such articles in case of damage may be expensive, but repair of such articles may be difficult, particularly when damage to the article is significant in size or extends through a thickness of a portion of a component.

In some examples, the disclosure describes a method including removing a portion of a base component adjacent to a damaged portion of the base component to define a repair portion of the base component. The base component may include a cobalt- or nickel-based superalloy, and the repair portion of the base component may include a through-hole extending from a first surface of the base component to a second surface of the base component. The method also may include forming a braze sintered preform to substantially reproduce a shape of the through-hole. The braze sintered preform may include a Ni- or Co-based alloy. The method additionally may include placing the braze sintered preform in the through-hole and heating at least the braze sintered preform to cause the braze sintered preform to join to the repair portion of the base component and change a microstructure of the braze sintered preform to a brazed and diffused microstructure.

<CIT> discloses a repairing method comprising bringing a solder insert into a hole of a substrate of a component, connecting the solder insert with the substrate using a soldering material in a gap by melting, and welding the gap between the solder insert and the substrate on height of the surface of the substrate, so that a welded joint or welding seam is formed on the height of the surface. A soldering layer from the soldering material is applied on the solder insert before the solder insert is brought into the hole. The welded joint is polished.

<CIT> discloses a method for mending damage on a turbine blade, a predefined template being provided which completely covers at least the damage, wherein in the area of the damage the material of the turbine blade is removed to form a removal area with a shape predetermined by the template and thereby at least the damage is removed in the removal area, a repair piece in the form the template is inserted into the removal area, and wherein the repair piece is connected to the turbine blade at a surface delimited by the removal area.

<CIT> discloses a process for filling openings, including blind holes, through-holes, and cavities, in high temperature components. The process entails forming a powder mixture by mixing particles of at least a base alloy and a second alloy that contains a sufficient amount of a melting point depressant to have a lower melting temperature than the base alloy. The powder mixture is combined with a binder and compacted to form a compacted preform, which is then heated to remove the binder and form a rigid sintered preform. The sintered preform is produced, or optionally is further shaped, to have a cross-sectional shape and dimensions to achieve a clearance of up to <NUM> micrometers with the opening, after which the preform is placed in the opening and diffusion bonded within the opening to form a brazement comprising the particles of the base alloy dispersed in a matrix formed by the second alloy.

<CIT>, forming the basis for the preamble of claim <NUM>, discloses a method of making pre-sintered preforms using a mixture of base superalloy particles and titanium-containing boron and silicon free braze alloy particles, such as for the repair of superalloy gas turbine engine components. Alloy particles as large as <NUM> provide reduced shrinkage when compared to prior art preforms.

<CIT> discloses techniques for joining a first component comprising a first metal or alloy and a second component comprising a second metal or alloy to each other. The techniques may include positioning the first and second component adjacent to each other to define a joint region between adjacent portions of the first component and the second component. The techniques also may include positioning a pre-sintered preform (PSP) braze material in the joint region, heating the PSP braze material to form a molten braze alloy, and cooling the molten braze alloy to join the first and second components. The PSP braze material may include a wide gap braze material.

<CIT> discloses a cobalt-base braze alloy composition and method for diffusion brazing for use in repairing superalloy articles. The cobalt-base braze alloy composition includes nickel; at least one element selected from the group of rhenium, palladium, and platinum; at least one element selected from the group of boron and silicon; and the remaining balance consists of cobalt. This composition may also include aluminum, and the composition may be combined with one or more base metal superalloy compositions to form a diffusion braze alloy mixture. In the method for repairing superalloy articles, the foregoing mixture is applied to a region of the superalloy article to be repaired, heated to melt the cobalt-base braze alloy and join the base metal superalloy particles together and the entire mixture to the region being repaired, and subjected to a diffusion braze heat treatment cycle in order to break down undesirable phases and to diffuse the melting point depressants into the mixture. After cooling, an environmental coating is applied to the final repair composite.

<CIT> discloses a method of repair capable of hooding a molten brazing material at the bonding portion when a component is bonded with a brazing material to an inclined or to a curved surface. The method of repair repairs by brazing a repair portion in which a crack has developed and which needs repair, wherein a brazing material support holding in the interior thereof a molten brazing material is brought into contact with the repair portion, and under the condition that the brazing material support is in contact with the repair portion, the molten brazing material is solidified. Under the condition that the brazing material in a powder form is brought into contact with the brazing material support, the brazing material can be melted by heating to a temperature at or above the melting point of the brazing material. Alternatively, under the condition that the brazing material support in the interior of which the brazing material has been beforehand held is brought into contact with the repair portion, the brazing material can be melted by heating to a temperature at or above the melting point of the brazing material.

<CIT> discloses a method of repairing a crack generated part of a moving blade and a stator blade for a gas turbine formed of an Ni and Co base super alloy, a part of the generated crack part is eliminated by a grinder, and then an auxiliary plate formed of the same material as the moving blade and stator blade and machined into a sheet state is set and jointed by brazing. A brazed surface part is laser-welded, and the brazed part surface is reformed so that wax material components and raw material components are mixed. In this case, B-group powder of Ni: <NUM>% and Si: <NUM>% is inserted between raw material and the auxiliary plate and jointed in vacuum. B-group powder of Ni: <NUM>%, Co: <NUM>%, Cr: <NUM>%, Mo: <NUM>% and Fe: <NUM>% is further inserted between the raw material and the auxiliary plate and jointed in vacuum.

<CIT> describes a method of repairing an aluminide coating on an article and in particular a method of locally repairing an aluminide coating on a gas turbine engine component.

This disclosure describes assemblies, systems, and techniques for repairing through-hole damage to an alloy component using a braze sintered preform (BSP) material. The BSP material includes a Ni- or Co-based alloy and may include a powder or mixture of powders that has been sintered to reduce porosity of the braze material. The BSP material may facilitate repair of larger damaged portions of an article than a braze paste or loose braze powder, damaged portions that extend through a thickness of at least a portion of the article, or both. In some examples, the BSP material may be used to repair equiaxed, directionally solidified, or single-crystal Ni-based alloys or Co-based alloys, such as those used in nozzle vane guides of gas turbine engines or the like.

The BSP material may be formed or shaped to substantially fill a repair portion of the damaged article. As used herein, "substantially fill" refers to a BSP material that fills all or nearly all the repair portion of the damaged article, aside from cracks or spaces at the interface between the BSP material and the article adjacent to the repair portion. Additional braze material, comprising an additional BSP material, is placed adjacent to the BSP material that substantially fills the repair portion to fill or cover the damage that the BSP material does not fill, such as the cracks or spaces.

In this way, the BSP material and additional braze material are used to repair damage to an article and may substantially fill the repair portion of the article. The BSP material may be used with equiaxed, directionally solidified, or single-crystal Ni-based alloy or Co-based alloy articles and may result in repaired articles in which the repaired portion may have metallurgical properties substantially similar to those of the original article. In this way, larger damaged portions of equiaxed, directionally solidified, or single-crystal Ni-based alloy or Co-based alloy articles may be repaired using the described BSP material than a braze paste or powder.

<FIG> is a conceptual and schematic diagram illustrating an example repaired article <NUM> including a base component <NUM>, a repair portion <NUM>, and a braze sintered preform <NUM> that substantially fills repair portion <NUM>. In some examples, repaired article <NUM> may be used as part of a high temperature mechanical system. For example, repaired article <NUM> may be or be part of a nozzle guide vane (NGV) that is used in a high pressure or intermediate pressure stage turbine in a gas turbine engine. In other examples, repaired article <NUM> 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, gas turbine engine vane, blade track, combustor liner, honeycomb, or the like.

Base component <NUM> includes a Ni- or Co-based superalloy. Base component <NUM> may be formed from a polycrystalline alloy, a directionally solidified alloy, or a single crystal alloy. Base component <NUM> 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, as is known in the art. Any useful superalloy may be utilized in base component <NUM>, 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, MI, under the trade designations CMSX-<NUM>, CMSX-<NUM>, CMSX-<NUM>, and CM-<NUM>; Co-based alloys available from Martin-Marietta Corp. , Bethesda, MD, under the trade designation MAR-M509; Ni-based alloys available from Special Metals Corporation, New Hartford, NY under the trade designation INCONEL™ <NUM>, INCONEL™<NUM>; and the like. The compositions of CMSX-<NUM> and CMSX-<NUM> are shown below in Table <NUM>.

Base component <NUM> may be made using at least one of casting, forging, powder metallurgy, or additive manufacturing.

Although <FIG> illustrates base component <NUM> as defining a simple, substantially rectangular geometry, in other examples, base component <NUM> may define a more complex geometry, including simple or complex curves, overhangs, undercuts, internal cavities, or the like. Examples of base component <NUM> that are part of a nozzle guide vane are shown in FIGS.

Base component <NUM> has been damaged. The damage may extend through a thickness of base component <NUM> from first surface <NUM> to second surface <NUM>. The damage may include, for example, airfoil burn-through, platform burn-through, trailing edge burn out, trailing edge burn back, leading edge burn out, a through crack, a turbine vane internal pedestal damage, blow-out failure of pressure and/or suction sides of an airfoil, foreign object damage, corrosion, or the like. As such, the damage may define a through-hole through a portion of base component <NUM> extending from first surface <NUM> to second surface <NUM>. As shown in <FIG>, a damaged portion of base component <NUM> has been worked or machined to remove at least part of the damaged portion, defining repair portion <NUM>. Repair portion <NUM> defines a through-hole through a portion of base component <NUM> and extends from first surface <NUM> to second surface <NUM>. Compared to the damaged portion, repair portion <NUM> defines smoother and/or geometrically simpler repair surfaces <NUM> and <NUM> against which BSP material <NUM> may be positioned. This may facilitate contact between surfaces of repair portion <NUM> and BSP material <NUM>. <FIG> illustrates repair surfaces <NUM> and <NUM> as substantially flat surfaces. In other examples, repair surfaces <NUM> and <NUM> may define other, more complex shapes, including, for example, simple or complex curves, overhangs, undercuts, or the like.

BSP material <NUM> is positioned in repair portion <NUM> and contacts repair surfaces <NUM> and <NUM>. BSP material <NUM> includes a Ni- or Co-based alloy and may include a powder mixture that has been sintered to form a preform. Sintering may reduce porosity compared to the powder, which may reduce porosity in the repaired portion during and after repair.

BSP material <NUM> includes a predetermined shape. The predetermined shape is selected to substantially fill repair portion <NUM> through substantially an entire depth of repair portion <NUM> (e.g., from first surface <NUM> to second surface <NUM>). The predetermined shape may be selected after machining or working base component <NUM> to remove at least part of the damaged portion of base component <NUM> to define repair portion <NUM>. For example, after removal of the at least part of the damaged portion, repair portion <NUM> may be imaged or otherwise interrogated to determine the shape of repair portion <NUM>. BSP material <NUM> may then be shaped or formed to substantially match the shape of repair portion <NUM>. Alternatively, repair portion <NUM> may be formed to substantially match a predefined shape of BSP material <NUM>.

BSP material <NUM> may be made by forming or shaping a powder or paste into the predetermined shape (e.g., in a mold), then at least partially sintering the formed or shaped powder or paste to form BSP material <NUM>. In this way, the shape of BSP material <NUM> may be tailored to the shape of repair portion <NUM>.

In some examples, as shown in <FIG>, a repaired article may include a base component that defines a more complicated shape, such as three-dimensional surface features. <FIG> is a conceptual and schematic diagram illustrating an example repaired article <NUM> including a base component <NUM> having three-dimensional features <NUM> on a surface <NUM> of the base component <NUM>, a repair portion <NUM>, and a BSP material <NUM> that substantially fills the repair portion <NUM> and has three-dimensional features <NUM> on a surface of the BSP material. Like base component <NUM> of <FIG>, base component <NUM> of <FIG> defines a repair portion <NUM> including repair surfaces <NUM> and <NUM>. Base component <NUM> also defines a first surface <NUM> and a second surface <NUM>.

Unlike base component <NUM> of <FIG>, base component <NUM> is not the only part of repaired article <NUM>. Repaired article <NUM> also includes a second component <NUM> to which base component <NUM> is attached or joined. For example, repaired article <NUM> may be a turbine nozzle guide vane component in which base component <NUM> is a pressure side airfoil wall, second component <NUM> is a suction side airfoil wall, and three-dimensional surface features <NUM> on airfoil inner surface <NUM> of base component <NUM> are pedestals, cooling features, or the like. As another example, repaired article <NUM> may be a dual wall component in which base component <NUM> is an outer wall, second component <NUM> is an inner wall or spar, and three-dimensional surface features <NUM> on inner surface <NUM> of base component <NUM> are pedestals, cooling features, or the like. The damaged portion and repair portion <NUM> define a through-hole extending through base component <NUM> from first surface <NUM> to second surface <NUM>, but may or may not extend through second component <NUM>.

Unlike base component <NUM> of <FIG>, second surface <NUM> of base component <NUM> defines three-dimensional surface features <NUM>, such as cooling features, pedestals or stand-offs, or the like. The damaged portion of base component <NUM> may have included similar three-dimensional surface features <NUM>. As such, in order to fully repair the damaged portion of base component <NUM>, BSP material <NUM> may be formed to include substantially similar three-dimensional features <NUM> on a surface of BSP material <NUM> that is placed adjacent to (e.g., parallel with) second surface <NUM> of base component <NUM>. The three-dimensional features may be formed during the sintering process or after the sintering process using a machining process such as milling, grinding, waterjet, laser, electrodischarge machining, or the like. By including three-dimensional features <NUM>, BSP material <NUM> may substantially fill repair portion <NUM> and may replace substantially all of the damaged portion of base component <NUM>.

BSP material <NUM> and BSP material <NUM> (referred to collectively as "BSP material <NUM>") comprise a Ni-based or Co-based alloy. In some examples, BSP material <NUM> 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, BSP material <NUM> 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, BSP material <NUM> may include both a braze alloy powder (e.g., a relatively low-melt powder composition) and a superalloy powder (e.g., a relatively high-melt powder composition). The low-melt alloy powder composition is an alloy, or a mixture of alloys, that substantially melts below the braze 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 BSP material <NUM> 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 <NUM> (about <NUM>° F), with the alloy or mixture of alloys being selected so that the low-melt powder composition as a whole substantially melts at a temperature between about <NUM> (about <NUM>°F) and about <NUM> (about <NUM>°F). 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 <NUM> (about <NUM>° F).

In some examples, the low-melt powder composition may include one or more alloy powders and includes between about <NUM> wt. % and about <NUM> wt. % Ni, between about <NUM> wt. % and about <NUM> wt. % Cr, between about <NUM> wt. % and about <NUM> wt. % Ta, between about <NUM> wt. % and about <NUM> wt. % Co, between about <NUM> wt. % and about <NUM> wt. % Al, up to about <NUM> wt. % B, and up to about <NUM> wt. % Si, and has a compositional melting range of between about <NUM> (about <NUM>°F) and about <NUM> (about <NUM>°F). In some examples, the low-melt powder composition also includes up to about <NUM> wt. % each of at least one of Ti, W, Mo, Re, Nb, Hf, Pd, Pt, Ir, Ru, C, Si, P, Fe, Ce, La, Y, or Zr. In some examples the low-melt alloy powder comprises a mixture of two or more low-melt alloys. For example, a low-melt alloy powder may include (a) about <NUM>% of a first low-melt powder including about <NUM> wt. % Ni, about <NUM> wt. % Cr, about <NUM> wt. % Al, about <NUM> wt. % Co, and about <NUM> wt. % B, with a liquidus temperature of about <NUM> (about <NUM>° F); (b) about <NUM>% of a second low-melt powder including about <NUM> wt. % Ni, about <NUM> wt. % Cr, about <NUM> wt. % Ta, and about <NUM> wt. % B, with a liquidus temperature of about <NUM> (about <NUM>° F); and (c) about <NUM> wt. % of a third low-melt powder including about <NUM> wt. % Ni, about <NUM> wt. % Al, about <NUM> wt. % Co, about <NUM> wt. % W, about <NUM> wt. % Ta, about <NUM> wt. % Si, about <NUM> wt. % Re, about <NUM> wt. % Nb, and about <NUM> wt. % B, with a liquidus temperature of about <NUM> (about <NUM>° 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 <NUM>, second component <NUM>, or both. For example, in some implementations, to join a first component <NUM> and a second component <NUM> that include Ni-based superalloy components such as those made of MAR-M246 or <NUM> or <NUM>, or CMSX-<NUM> or -<NUM>, the high-melt powder composition may include between about <NUM> wt. % and about <NUM> wt. % Ni, between about <NUM> wt. % and about <NUM> wt. % Cr, between about <NUM> wt. % and about <NUM> wt. % Ta, between about <NUM> wt. % and about <NUM> wt. % Co, between about <NUM> wt. % and about <NUM> wt. % Al, between about <NUM> wt. % and about <NUM> wt. % W, between about <NUM> wt. % and about <NUM> wt. % Re, up to about <NUM> wt. % Mo, and up to about <NUM> wt. In some examples, the high-melt powder composition also may include up to about <NUM> wt. % each of at least one of Ti, Nb, C, B, Si, or Zr. In some examples, the high-melt powder composition includes between about <NUM> wt. % and about <NUM> wt. % Ni, about <NUM> wt. % Cr, about <NUM> wt. % Ta, about <NUM> wt. % Co, about <NUM> wt. % Al, about <NUM> wt. % Re, about <NUM> wt. % Hf, and about <NUM> wt.

The low-melt powder composition and the high-melt powder composition may be combined in any selected ratio. In some examples, BSP material <NUM> may include a powder mixture consisting of between about <NUM> wt. % and about <NUM> wt. % low-melt powder composition and a balance high-melt powder composition (a ratio of between about <NUM>:<NUM> and about <NUM>:<NUM> low-melt:high-melt powder). In some cases, braze alloy powder may be a mixture of more than one braze alloys which are all powder. In some examples, the ratio may be between about <NUM>:<NUM> and about <NUM>:<NUM> low-melt: high-melt powder, such as a ratio between about <NUM>:<NUM> and about <NUM>:<NUM> low-melt: high-melt powder, or a ratio between about <NUM>:<NUM> and about <NUM>:<NUM> low-melt: high-melt powder. For example, BSP material <NUM> may include between about <NUM> wt. % and about <NUM> wt. % low-melt alloy powder and between about <NUM> wt. % and about <NUM> wt. % high-melt powder, such as about <NUM> wt. % low-melt alloy powder and about <NUM> wt. % high-melt powder.

Hence, in some examples, BSP material <NUM> may include between about <NUM> wt. % and about <NUM> wt. % Ni, up to about <NUM> wt. % Cr, up to about <NUM> wt. % Ta, up to about <NUM> wt. % Co, up to about <NUM> wt. % Al, up to about <NUM> wt. % W, up to about <NUM> wt. % Re, up to about <NUM> wt. % Mo, up to about <NUM> wt. % Hf, and, optionally, up to about <NUM> wt. % Nb, up to about <NUM> wt. % Si, and up to about <NUM> wt. In some examples, BSP material <NUM> may include between about <NUM> wt. % and about <NUM> wt. % Ni, between about <NUM> wt. % and about <NUM> wt. % Cr, between about <NUM> wt. % and about <NUM> wt. % Ta, between about <NUM> wt. % and about <NUM> wt. % Co, between about <NUM> wt. % and about <NUM> wt. % Al, between about <NUM> wt. % and about <NUM> wt. % W, between about <NUM> wt. % and about <NUM> wt. % Re, about <NUM> wt. % Mo, about <NUM> wt. % Hf, and, optionally, up to about <NUM>% each at least one of Ti, Nb, Pd, Pt, Ir, Ru, C, B, Si, P, Mn, Fe, Ce, La, Y, or Zr. In some examples, BSP material <NUM> may include between about <NUM> wt. % and about <NUM> wt. % Ni, between about <NUM> wt. % and about <NUM> wt. % Cr, between about <NUM> wt. % and about <NUM> wt. % Ta, between about <NUM> wt. % and about <NUM> wt. % Co, between about <NUM> wt. % and about <NUM> wt. % Al, between about <NUM> wt. % and about <NUM> wt. % W, between about <NUM> wt. % and about <NUM> wt. % Re, between about <NUM> wt. % and about <NUM> wt. % Mo, between about <NUM> wt. % and about <NUM> wt. % Hf, between about <NUM> wt. % and about <NUM> wt. % Nb, between about <NUM> wt. % and about <NUM> wt. % Si, and between about <NUM> wt. % and about <NUM> wt. In some examples, BSP material <NUM> may include between about <NUM> wt. % and about <NUM> wt. % Cr, between about <NUM> wt. % and about <NUM> wt. % Al, between about <NUM> wt. % and about <NUM> wt. % Co, between about <NUM> wt. % and about <NUM> wt. % W, between about <NUM> wt. % and about <NUM> wt. % Mo, between about <NUM> wt. % and about <NUM> wt. % Ta, between about <NUM> wt. % and about <NUM> wt. % B, about <NUM> wt. % Si, between about <NUM> wt. % and about <NUM> wt. % Re, between about <NUM> wt. % and about <NUM> wt. % Hf, between about <NUM> wt. % and about <NUM> wt. % Nb, and a balance Ni.

BSP material <NUM> may include between <NUM> and <NUM> wt. % C, between <NUM> and <NUM> wt. % Si, between <NUM> wt. % and <NUM> wt. % Cr, between <NUM> wt. % and <NUM> wt. % B, between <NUM> wt. % and <NUM> wt. % Al, between <NUM> wt. % and <NUM> wt. % W, between <NUM> wt. % and <NUM> wt. % Mo, between <NUM> wt. % and <NUM> wt. % Re, between <NUM> wt. % and <NUM> wt. % Ta, between <NUM> wt. % and <NUM> wt. % Hf, and between <NUM> wt. % and <NUM> wt. % Co, and a balance Ni. Additionally and optionally, BSP material <NUM> may include a maximum of <NUM> wt. % Mn, a maximum of <NUM> wt. % S, a maximum of <NUM> wt. % P, a maximum of <NUM> wt. % Ti, a maximum of <NUM> wt. % Y, a maximum of <NUM> wt. % Zr, a maximum of <NUM> wt. % Fe, a maximum of <NUM> wt. % V, a maximum of <NUM> wt. % Cu, a maximum of <NUM> wt. % Mg, a maximum of <NUM> wt. % O, a maximum of <NUM> wt. % N, a maximum of <NUM> wt. % P, and a maximum of <NUM> wt. % other elements.

In selecting the proportions of components used in BSP material <NUM>, 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.

In some examples, BSP material <NUM> that includes higher Al content may possess improved high-temperature oxidation resistance properties compared to BSP material <NUM> with lower Al content. Further, increasing Ta content in BSP material <NUM> may improve mechanical properties of the braze joint compared to lower Ta content. In particular, Ta may strengthen the gamma nickel and gamma prime nickel aluminide phases by increasing lattice mismatches.

BSP material <NUM> may be formed by mixing an alloy powder or multiple alloy powders in a selected composition, then sintering the powder while disposed in a mold to form a sintered preform with reduced porosity. The sintering temperature and the duration of the sintering may depend at least in part on the composition of the alloy powder or multiple alloy powders. The mold shape may be selected so that BSP material <NUM> substantially fills repair portion <NUM> or may be selected to result in a BSP material <NUM> that may be cut or machined to substantially fill repair portion <NUM>.

In some examples, the sintered powder may then be cut or machined into a predetermined shape. For example, the predetermined shape may correspond to a shape of repair portion <NUM>. As described above, repair portion <NUM> may include a relatively simple geometry as shown in <FIG>, or may include a more complex geometry, e.g., as shown in <FIG>. Accordingly, the sintered powder may be cut or machined into a relatively simple shape, or a more complex shape, e.g., including curvature, angles, apertures, three-dimensional surface features, or the like to form BSP material <NUM>. Regardless of the complexity of the shape of BSP material <NUM> and depending upon the geometry of repair portion <NUM>, BSP material <NUM> 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).

By utilizing BSP material <NUM>, alloys with desirable mechanical and chemical (e.g., high temperature oxidation resistance) may be utilized in a brazing technique to repair damage to base component <NUM>. The resulting repaired portion 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. Further, by utilizing a BSP material <NUM>, the repaired portion may include reduced porosity compared to a joint formed using a braze powder, positioning of the braze material may be easier and more precise than with a braze powder, and larger damaged portions may be repaired, including damaged portions that include through-holes extending from a first surface of a base component to a second surface of the base component.

<FIG> is a flow diagram illustrating an example technique for repairing a damaged portion including a through-hole using a BSP material. The technique of <FIG> will be described with reference to repaired article <NUM> of <FIG> for purposes of illustration only. It will be appreciated that the technique of <FIG> may be performed with a different article, or that article <NUM> may be used in a different repair technique.

The technique of <FIG> includes removing a portion of base component <NUM> adjacent to a damaged portion of base component <NUM> to define repair portion <NUM> (<NUM>). Repair portion <NUM> includes a through-hole that extends from first surface <NUM> of base component <NUM> to second surface <NUM> of base component <NUM>. Repair portion <NUM> defines repair surfaces <NUM> and <NUM>, which may be smoother and/or geometrically simpler than the surfaces of the damaged portion. In some examples, the removed portion of base component <NUM> may be sufficiently large to remove all damage from base component <NUM>. In other examples, the removed portion of base component <NUM> may not remove all damage. For example, the removed portion of base component <NUM> may include any damaged portions that significantly deviate from the original geometry of base component <NUM>, e.g., by protruding from the surface of base component <NUM>, but may leave smaller damaged areas, such as smaller cracks that may or may not extend through a thickness of base component.

Although not shown in <FIG>, in some examples, after removing the portion of base component <NUM> adjacent to the damaged portion of base component <NUM> to define repair portion <NUM> (<NUM>), repair surface <NUM>, repair surface <NUM>, first surface <NUM>, and/or second surface <NUM> may be inspected and cleaned. Cleaning may include removing chemically damaged portions of the surface, e.g., portions of surfaces <NUM>, <NUM>, <NUM>, and/or <NUM> that were burned or oxidized, removing coatings on surface <NUM> and/or surface <NUM>, or the like. The cleaning may be accomplished mechanically, chemically, electrochemically, or the like. For example, one or more of surfaces <NUM>, <NUM>, <NUM>, or <NUM> may be ground, sanded, grit-blasted, chemically mechanically polished, etched, or the like to clean the surface. The cleaned surfaces may produce a stronger joint to BSP material <NUM> than uncleaned surfaces.

The technique of <FIG> includes forming BSP material <NUM> to substantially reproduce a shape of the through-hole of repair portion <NUM> (<NUM>). BSP material <NUM> may be formed by mixing an alloy powder or multiple alloy powders in a selected composition, then sintering the powder while the powder is disposed in a mold to form a sintered preform with reduced porosity. The sintering temperature and the duration of the sintering may depend at least in part on the composition of the alloy powder or multiple alloy powders. The mold shape may be selected so that BSP material <NUM> substantially fills repair portion <NUM> or may be selected to result in a BSP material <NUM> that may be cut or machined to substantially fill repair portion <NUM>.

In some examples, the sintered powder may then be cut or machined into a predetermined shape. For example, the predetermined shape may correspond to a shape of repair portion <NUM>, such that BSP material <NUM> substantially fills a width and depth (e.g., a volume) of repair portion <NUM>. As described above, repair portion <NUM> may include a relatively simple geometry as shown in <FIG>, or may include a more complex geometry, e.g., as shown in <FIG>. Accordingly, the sintered powder may be cut or machined into a relatively simple shape, or a more complex shape, e.g., including curvature, angles, apertures, three-dimensional surface features, or the like to form BSP material <NUM>. Regardless of the complexity of the shape of BSP material <NUM> and depending upon the geometry of repair portion <NUM>, BSP material <NUM> 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 technique of <FIG> then includes placing BSP material <NUM> in repair portion <NUM> (<NUM>). For example, as shown in <FIG>, BSP material <NUM> may be placed to contact repair surfaces <NUM> and <NUM> of repair portion <NUM>. In some examples, BSP material <NUM> may be tack welded in place to maintain the position of BSP material <NUM> relative to base component <NUM> prior to heating BSP material <NUM>. For example, BSP material <NUM> may be tack welded using resistance welding.

The technique of <FIG> may includes positioning additional braze material adjacent to BSP material <NUM> (<NUM>). In some examples, additional braze material may be positioned adjacent to BSP material <NUM> (<NUM>) prior to heating at least the BSP material <NUM> (<NUM>). The additional braze material includes a Ni- or Co-based alloy, such as a Ni- or Co-based alloy with a composition that may be substantially similar to that of BSP material <NUM>. The additional braze material includes a second BSP material formed as a sheet or foil. The additional braze material is positioned adjacent to BSP material <NUM> to fill or cover parts of repair portion <NUM> or adjacent damage that BSP material <NUM> does not fill. For example, the additional braze material may be positioned in cracks or spaces not filled by BSP material <NUM>, may be placed over BSP material <NUM>, contacting first surface <NUM> or second surface <NUM> to provide a substantially continuous surface after heating, or the like. In some examples, multiple additional braze materials, such as multiple additional BSP materials, or an additional BSP material and a braze paste or powder, may be positioned adjacent to BSP material <NUM> (<NUM>).

In examples in which a braze powder or braze paste are used as the additional braze material, positioning additional braze material adjacent to BSP material <NUM> (<NUM>) may include positioning braze stop material at selected locations of base component <NUM> to retain the additional braze material at desired locations of base component <NUM> during heating. The selected locations of base component <NUM> may include external locations (e.g., on an exterior surface), internal locations (e.g., within internal cavities), or both.

The technique of <FIG> further includes heating at least BSP material <NUM> to join BSP material <NUM> to base component <NUM> and change the microstructure of BSP material <NUM> to a brazed and diffused microstructure (<NUM>). In some examples, BSP material <NUM> may be heated in a furnace or other closed retort, and base component <NUM> may be heated with BSP material <NUM>. In some examples, the furnace or closed retort may enclose a vacuum or substantially inert atmosphere (e.g., an atmosphere including constituents that substantially do not react with base component <NUM> and BSP material <NUM> at the temperatures and pressures experienced by the interior of the furnace or closed retort). In some examples, BSP material <NUM> may be heated at a braze temperature of between about <NUM> (about <NUM>° F) and about <NUM> (about <NUM>° F), such as a braze temperatures of about <NUM> (about <NUM>° F). The time for which BSP material <NUM> is heated at the braze temperature may vary from about <NUM> minutes to about <NUM> minutes, for example between about <NUM> to <NUM> minutes.

In some examples, rather than placing BSP material <NUM> (<NUM>) and second BSP material (<NUM>) before heating at least BSP material <NUM> (<NUM>), at least BSP material <NUM> may be heated to join BSP material <NUM> to base component <NUM> (<NUM>) before the second BSP material is positioned adjacent to BSP material <NUM> (<NUM>). Once the second BSP material is positioned adjacent to BSP material <NUM> (<NUM>) at least the second BSP material is heated to join the second BSP material to BSP material <NUM> and/or base component <NUM>. For example, the second BSP material may be heated using similar or substantially the same heat treatment parameters as described above with reference to BSP material <NUM>.

BSP material <NUM> then may be allowed to cool to ambient temperature to form a solid and join to base component <NUM>. In some examples, as part of heating at least BSP material <NUM> to join BSP material <NUM> to base component <NUM> and change the microstructure of BSP material <NUM> to a brazed and diffused microstructure (<NUM>), BSP material <NUM> may be subjected to a diffusion heat treatment cycle. For example, at least BSP material <NUM>, and possibly BSP material <NUM> and base component <NUM>, may be heated in a vacuum furnace back filled with argon gas maintaining at a pressure between <NUM> to <NUM> microns Hg at a temperature between about <NUM> and about <NUM> for between about <NUM> hours and about <NUM> hours. For example, between about <NUM> and about <NUM> for at least <NUM> hours at least BSP material <NUM>, and possibly BSP material <NUM> and base component <NUM>, may be heated in a vacuum furnace back filled with argon gas maintaining at a pressure between <NUM> to <NUM> microns Hg at a temperature between about <NUM> and about <NUM> for at least <NUM> hours. The diffusion heat treatment may allow smaller alloying additions from the low melt braze powder (e.g., boron and silicon) to diffuse into the adjacent high melt powder in BSP material <NUM> and into base component <NUM> to create a more homogeneous microstructure and increase the re-melting temperature of the repaired structure.

In some examples, at least BSP material <NUM> may be machined after completion of heat treatments to remove excess BSP material <NUM> and restore base component <NUM> to a nominal part geometry.

<FIG> are photographs illustrating an example nozzle guide vane during various stages of repair of a damaged vane airfoil. As shown in <FIG>, the airfoil <NUM> of nozzle guide vane <NUM> suffered burn through damage <NUM> on the pressure side <NUM> of the airfoil <NUM>. <FIG> shows nozzle guide vane <NUM> after removing a portion of airfoil <NUM> adjacent to the burn through damage <NUM> to define a <NUM>/<NUM> inch (<NUM>) diameter through-hole <NUM>. <FIG> shows the airfoil with a BSP material <NUM> placed in through-hole <NUM>. As shown in <FIG>, additional cracks <NUM> are present in the airfoil adjacent to the repair portion through-hole. <FIG> shows additional braze material in the form of braze paste <NUM> applied to the airfoil <NUM>, including within additional cracks <NUM>, with braze stop-off material on the airfoil <NUM> to maintain the braze paste <NUM> in desired locations. The braze stop-off material also may be applied inside airfoil <NUM>, which is not shown in the figures. <FIG> shows the airfoil <NUM> after a first brazing cycle has been completed to join the BSP material <NUM> and braze paste <NUM> to the vane airfoil <NUM>, to repair through-hole and additional cracks <NUM> and to change BSP material <NUM> and braze paste <NUM> into a brazed microstructure. <FIG> shows two additional BSP materials <NUM> and <NUM> placed over the repair portion. Each BSP material <NUM> and <NUM> in <FIG> was about <NUM> inch (<NUM>) thick. The additional BSP materials <NUM> and <NUM> were resistance tack welded to the surface of the vane airfoil <NUM>. <FIG> shows the vane airfoil <NUM> after a second brazing cycle to join the additional BSP materials <NUM> and <NUM> to the vane airfoil <NUM>. <FIG> shows the locations of the two sections shown in <FIG> (section <NUM>) and 3J (section <NUM>). As shown in <FIG>, the BSP filled substantially the entire depth of the repair portion through-hole <NUM> and additional cracks <NUM>.

<FIG> are photographs illustrating an example nozzle guide vane <NUM> during various stages of repair of a damaged platform <NUM>. <FIG> shows platform burn-through damage <NUM>. <FIG> shows the platform <NUM> after removing a portion of the platform <NUM> adjacent to the damage <NUM> to define a through-hole <NUM>. <FIG> shows the platform <NUM> with a BSP material <NUM> placed in the through-hole <NUM> and resistance tack welded in place. <FIG> shows additional BSP material <NUM> placed on a surface of the platform over the BSP material <NUM> in the through-hole <NUM>, after heating to join the BSP material <NUM> to the platform <NUM>.

<FIG> are photographs illustrating an example BSP material <NUM> having three-dimensional surface features <NUM> and a repaired vane airfoil including the BSP material <NUM> having the three-dimensional surface features <NUM>.

Claim 1:
A method comprising:
removing (<NUM>) a portion of a base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) adjacent to a damaged portion (<NUM>) of the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) to define a repair portion (<NUM>, <NUM>) of the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), wherein the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprises a cobalt- or nickel-based superalloy, and wherein the repair portion (<NUM>, <NUM>) of the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprises a through-hole (<NUM>, <NUM>) extending from a first surface (<NUM>, <NUM>) of the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) to a second surface (<NUM>, <NUM>) of the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
forming (<NUM>) a braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) to substantially reproduce a shape of the through-hole (<NUM>, <NUM>), wherein the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) comprises a Ni- or Co-based alloy;
placing (<NUM>) the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) in the through-hole (<NUM>, <NUM>);
characterized by:
positioning (<NUM>) additional braze material (<NUM>, <NUM>, <NUM>) comprising the Ni- or Co-based alloy adjacent to the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) to fill or cover parts of the repair portion (<NUM>, <NUM>) or adjacent damage that the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) does not fill, wherein:
the additional braze material (<NUM>, <NUM>, <NUM>) comprises a second braze sintered preform (<NUM>, <NUM>, <NUM>), wherein the second braze sintered preform (<NUM>, <NUM>, <NUM>) comprises a sheet, and wherein the sheet overlies the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) and at least part of the repair portion (<NUM>, <NUM>) of the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
heating (<NUM>) at least the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) and the additional braze material (<NUM>, <NUM>, <NUM>) to cause the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) and the additional braze material (<NUM>, <NUM>, <NUM>) to join to the repair portion (<NUM>, <NUM>) of the base component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and change a microstructure of the braze sintered preform (<NUM>, <NUM>, <NUM>, <NUM>) and the additional braze material (<NUM>, <NUM>, <NUM>) to a brazed and diffused microstructure.