WO2019168517A1

WO2019168517A1 - Brazing of superalloy components with hydrogen addition for boron capture

Info

Publication number: WO2019168517A1
Application number: PCT/US2018/020170
Authority: WO
Inventors: Somesh J. Ghunakikar; Atul L. Navale; James A. Yarbrough; Ivan F. OLIVER VARGAS
Original assignee: Siemens Energy, Inc.
Priority date: 2018-02-28
Filing date: 2018-02-28
Publication date: 2019-09-06

Abstract

There is provided a process for repairing a turbine component (15) having a structural defect (36) therein. The process includes applying an amount of a braze material (40) over and/or within the structural defect (36) and subjecting the braze material (36) and component (15) to a brazing process. The brazing process includes alternating between a first stage wherein an amount of hydrogen is introduced into an environment about the component effective to form an amount of boranes and a second stage wherein the formed boranes are removed via negative pressure.

Description

BRAZING OF SUPERALLOY COMPONENTS WITH HYDROGEN ADDITION FOR

BORON CAPTURE

FIELD

The present invention relates to the field of metallurgy, and more specifically to processes for the repair of structural defects in a metallic substrate, wherein the processes enable the use of boron-containing braze materials while reducing the deleterious effects thereof.

BACKGROUND

Gas turbines are well-known in the art. It is an ongoing quest within the gas turbine field to increase the thermal efficiency of the gas turbine cycle. One way this has been accomplished is via the development of increasingly temperature-resistant materials, or materials that are able to maintain their structural integrity over time at high temperatures. For this reason, the hot gas path components of gas turbine engines are often formed from superalloy materials. The term“superalloy” is used herein as it is commonly used in the art to refer to a highly corrosion and oxidation resistant alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, e.g.,

> 1000° C.

Despite their strength, superalloy components in the hot gas path of a turbine engine are susceptible to damage (defects) due to their long term exposure to significant thermal and mechanical stresses. It is generally known that superalloy materials are among the most difficult materials to repair. Welding and brazing are two processes which attempt to repair the damaged superalloy material. Welding of many superalloys however is made difficult because of the propensity of these materials to develop weld solidification cracking and strain age cracking. Accordingly, brazing processes are often attempted. Numerous different braze materials have been proposed for the use in structural repairs of superalloy components - most of which have their own limitations. For example, commonly used braze materials utilize a material having a different composition, melting point, and mechanical strength less than that of the underlying substrate, thereby resulting in a structural deficiency in the component - even after repair. Other braze materials utilize a similar or same material to the underlying substrate being repaired along with a melting point suppressant, such as silicon or boron, to lower the necessary brazing temperature and reduce further thermal stress to the underlying substrate. The use of boron, however, is not without detriment as the boron will form undesired phases. These undesired phases may reduce the structural integrity of the braze, as well as portions of the underlying superalloy components by diffusion. For this reason, the boron or silicon-free braze materials have been developed but are generally structural weaker than the underlying substrate material being repaired.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of the drawings that show:

FIG. 1 illustrates an example of a typical gas turbine engine;

FIG. 2 illustrates a blade from the gas turbine of FIG. 1 in need of repair by one or more of the processes described herein.

FIG. 3 illustrates the application of a braze paste in a repair process in

accordance with an aspect of the present invention.

FIG. 4 illustrates the application of a pre-sintered preform (PSP) in a repair process in accordance with an aspect of the present invention.

SUMMARY

The present inventors have developed processes for the repair of structural defects, such as cracking, on a surface of or within turbine components. The processes allow for the use of boron in the braze material to reduce the temperature at which brazing is carried out yet remove an amount of the boron before formation of the final brazement to at least reduce the formation of undesired boron phases in the brazement and/or substrate. In the process, the braze material comprising boron may be deposited on or over the structural defect to be repaired at any location of the

component. In a particular embodiment, for example, the braze material is provided in the form of a pre-sintered preform which is applied to a portion of a platform of a turbine blade having substantial cracking therein. Once in place, the braze material is subjected to a brazing temperature protocol, wherein the component is subjected to alternating hydrogen and vacuum stages. The hydrogen stage induces the formation of hydrogen/boron-containing compounds, such as boranes, which are then removed from the material/environment during the vacuum stage. In this way, aspects of the present invention alternate the introduction of hydrogen and a vacuum to affect boron content post-brazing.

Thus, in accordance with an aspect, there is provided a process for repairing a structural defect in a turbine component comprising:

applying an amount of a braze material comprising boron over and/or within the structural defect; and

subjecting the braze material and component to a brazing process to melt the braze material and fill the structural defect, wherein the brazing process comprises alternating between a first stage wherein an amount of hydrogen is introduced into an environment about the component effective to form boranes from the boron and the hydrogen in the braze material, component, or the environment about the component and a second stage wherein an amount of the formed boranes are removed via negative pressure.

DETAILED DESCRIPTION

Now referring to the figures, FIG. 1 illustrates a known gas turbine engine 2 having a compressor section 4, a combustor section 6, and a turbine section 8. In the turbine section 8, there are alternating rows of stationary airfoils 18 (commonly referred to as "vanes") and rotating airfoils 16 (commonly referred to as "blades"). Each row of blades 16 is formed by a circular array of airfoils connected to an attachment disc 14 disposed on a rotor 10 having a rotor axis 12. The blades 16 extend radially outward from the rotor 10 and terminate in blades tips. The vanes 18 extend radially inward from an inner surface of vane carriers 22, 24 which are attached to an outer casing 26 of the engine 2. Between the rows of vanes 18 a ring seal 20 is attached to the inner surface of the vane carrier 22. The ring seal 20 is a stationary component that acts as a hot gas path guide between the rows of vanes 18 at the locations of the rotating blades 16. The ring seal 20 is commonly formed by a plurality of ring segments (not shown) that are attached either directly to the vane carriers 22, 24 or indirectly such as by attachment to metal isolation rings (not shown) attached to the vane carriers 22, 24. During engine operation, high-temperature/high-velocity gases 28 flow primarily axially with respect to the rotor axis 12 through the rows of vanes 18 and blades 16 in the turbine section 8.

As noted above, it is appreciated that during operation that the blades 16 and vanes 18, particularly in the early stages of the turbine engine may be susceptible to significant thermal and mechanical stresses. Accordingly, particularly with some superalloys, it is common to see cracking and other defects develop on the tip of the blade 16, the platform, and/or the platform fillets of the blades 16 or vanes 18. FIG. 2, for example, illustrates a turbine component 15 (component 15) for repair by the brazing processes described herein. In an embodiment, the component 15 comprises a gas turbine blade 16 formed from a superalloy material 31 and comprising a platform 30, an airfoil 32 projecting radially from the platform 30, and a platform fillet 34 extending between the airfoil 32 and the platform 30 for transitioning the airfoil 32 to the platform 30. In an embodiment, the blade 16 comprises one or more service-induced structural defects 36, e.g., cracks (discontinuities) 38, extending into a body of the blade 16 from a surface thereof.

The below-described brazing repair processes aim to repair such defects 36 by associating a braze material with the defects 36 and subjecting the component 15 (with braze material) to a heat treatment protocol to fill/repair the defects 36 with the braze material such that the component 15, for example, may be returned to operation via repair vs. discarding of the component 15, thereby alleviating the significant

replacement costs. Although a blade 16 is illustrated, it is appreciated that the repair processes described herein are not limited to blades 16, but may be applied to any other component 15 which would benefit from the repair processes described herein, including other turbine components (e.g., vanes 18) illustrated in FIG. 1.

The component 15 may comprise any suitable metal material. In certain embodiments, the component 15 comprises a titanium-based component, such as a titanium aluminide (TiAI)-based material or a titanium steel alloy. In an embodiment, the TiAI is gamma-TiAI. In another embodiment, the component 15 comprises an alloy material, such as a superalloy material. Superalloys typically refer to alloys that exhibit excellent mechanical strength and high resistance to creep at high temperatures (e.g., > 1000° C). In addition, superalloys typically have excellent surface stability, corrosion resistance, and oxidation resistance. In an embodiment, the superalloy comprises one or more of nickel, cobalt, or nickel-iron as a base alloying element of the superalloy. In certain embodiments, the superalloy material comprises a directionally solidified (DX) alloy such as a single crystal (SX) superalloy. Exemplary superalloys include but are not limited to Hastelloy, Inconel (e.g., IN100, IN600, IN713), Waspaloy, Rene alloys (e.g., Rene 41 , Rene 80, Rene 95, Rene N5), Haynes alloys, Incoloy, MP98T, TMS alloys, and CMSX (e.g., CMSX-4) single crystal alloys. In a particular embodiment, the component is formed from an Alloy 247 material (a CM247 or MAR-M247 material as is known in the art and commercially available form Praxair Surface Technologies). In an embodiment, the Alloy 247 material may have a composition within the following ranges (in wt %):

C: = 0.07-0.15%

Cr = 8.1 -8.4%

Co = 9.2-10.0%

Al = 5.5-5.6%

B = 0.015%

W = 9.5-10.0%

Mo = 0.5-0.7%

Ta = 3.0-3.2%

Ti = 0.7-10%

Hf = 1.4-15%

Zr = 0.015-0.05%

Ni = balance

Prior to brazing, optionally, an area including the structural defect 36 of the component 15 may be cleaned. In an embodiment, the cleaning step may be carried out using one or more of vacuum cleaning, hydrogen cleaning, fluoride ion cleaning (FIC), or a combination thereof depending upon on the material characteristics of the component 15. In a particular embodiment, the damaged area, including the defect 36, may be cleaned via a fluoride ion cleaning (FIC) process to ready the damaged surface for brazing. In some situations, cracks 38 may need to be physically opened up prior to FIC process. In some embodiments, the FIC process includes cleaning with hydrogen fluoride gas. Use of FIC cleaning advantageously removes unwanted oxides and residual coating remnants (e.g., diffusion coating remnants) within the defects 36, as well as on a surface of the component 15.

In particular embodiments, the FIC process includes vacuum/thermal/chemical processing steps which occur at a pressure and temperature range of 100 torr (133 mbar) to atmospheric pressure and at temperatures of 1750° F to 1900° F (955 to 1040° C) using HF (anhydrous hydrogen fluoride) gas which can be precisely metered during the FIC process. The FIC process can eliminate deeply imbedded oxides (e.g., aluminum and titanium oxides) at the surface and within the defects 36 through the following reactions:

6HF+AI₂03®2AIF3+3H₂0

4HF+Ti0₂ TiF4+2H₂0

6HF+Cr₂0₃ 2CrF₂+F₂+3H₂0

Use of vacuum or partial pressures may increase the effectiveness of oxide removal from cracks by forcing HF gas into cracks and by increasing volatilization of oxide products under vacuum conditions. Removal of some amounts of metallic Al and Ti through volatilization may also occur via the following reactions:

6HF+2AI 2AIF₃+3H₂

8HF+2Ti 2TiF₄+4H₂

It is generally appreciated that the rate of cleaning in FIC is a function of the temperature, concentration of HF, and alloy composition.

Once ready for brazing, a braze material 40 is applied within and/or over the structural defect 36 as is shown in FIGS. 3-4, for example. The braze material 40 may be in any desired form such as a powder, slurry, paste, tape, wire, foil, pre-sintered preform (PSP), or the like, and combinations thereof as are all known in the art.

Depending on the form, the braze material 40 may be provided in dry form or in an emulsion or dispersion using solvent/carriers such as deionized water, organic solvents (e.g., ethanol and propanol), inorganic solvents (e.g., HCI), and the like. In certain embodiments, the braze material 40 may further include a suitable binder/carrier, such as“s-gel,” commercially available from the Wall Comonoy Corp. It is appreciated that the form of the braze material 40 may be selected based upon the nature and size of the defect, the location of the defect on the component, the shape of the damaged area, or the like. For example, for deep cracks and/or through cracks, it may be desirable to apply an amount of paste to at least partially fill the defect to ensure travel of the repair material to the area.

Accordingly, in one embodiment, as shown in FIG. 3, the braze material 40 comprises a paste material (braze paste) 42. When utilized, the braze paste 42 is applied onto the component surface to fill the defect(s) 36, e.g., cracks 38 and other inhomogeneities, that may be present. In certain embodiments, the braze paste 42 comprises a powder mixture being bound together using a liquid binder. In some embodiments, the braze paste 42 is utilized in combination with a pre-sintered preform (PSP) (described below). For example, a braze paste 42 may be particularly beneficial in certain embodiments where the damaged area includes cracks, grooves, or other inhomogeneities which may affect contact and bonding of the PSP to the component surface. In such instances, the defect(s) may at least be partially filled with paste 42 prior to application of a PSP thereover. In an embodiment, the paste 42 may be introduced into cracks by regulating compressed air behind a piston to force the paste 42 through an application needle into the cracks.

In accordance with another aspect, the braze material 40 comprising boron may be in the form of a pre-sintered preform (PSP) 44. PSPs as a delivery form for brazing materials are known in the art and are described, for example, in US 2016/0199930, the entirety of which is incorporated by reference herein. As shown in FIG. 4, the PSP 44 is in a form configured to be directly associated (e.g., spot welded) to the component surface to at least partially cover the defect(s) 36 to be repaired. The PSP 44 is typically manufactured by mixing the desired braze material in powder form with a suitable binder, and heating the mixture for a time and at a temperature effective to sinter the particles and form a self-supporting sheet (pre-form) which can be cut to a desired dimension for the repair.

In other embodiments, the braze material 40 may be in the form of a foil, which is prepared by sintering one or more layers of braze material and simultaneously or afterwards applying pressure to the sintered layer(s) to form the desired foil product. In still other embodiments, the braze material 40 may be in the form of a tape or wire as is known in the art, or alternatively in any other suitable form. The tape may be

particularly useful when the structural damage is in locations where PSP is rendered difficult.

The braze material 40 may comprise any suitable material known in the art for brazing which contains at least an amount of boron effective to reduce a melting temperature of the braze material relative to the same braze material without boron (an amount of boron). In an embodiment, the amount of boron may be an amount of boron effective to reduce a melting temperature of the braze material to a desired degree. In a particular embodiment, the braze material 40 comprises an amount of boron plus a first powder material including the same alloy components as that in the damaged area of the component to be brazed/repaired.

In other embodiments, the braze material 40 comprises an amount of boron along with an amount of a first powder material comprising a formulation as follows. In this embodiment, the first powder material comprises one or more elements (other than boron) distinct from the component being brazed. For example, in an embodiment, the braze material 40 comprises an amount of boron plus a ternary alloy comprising (in wt. %):

Cr 15-25%;

Ti 15-25%;

balance Ni.

These particular braze alloy materials exhibit a solidus temperature of about 1 ,205 °C and a liquidus temperature of about 1 ,215 °C. As such, they may be particularly useful when brazing to Alloy 247 or Rene 80.

In another embodiment, the braze material 40 comprises an amount of boron plus a first powder material comprising (in wt %): Cr 12-16%;

Ti 13-16%;

Al 0-2.5%;

Co 2-4%;

W 3-5%;

Mo 0-2%;

Ta 0-2%;

balance Ni.

In yet another embodiment, the braze material 40 comprises an amount of boron and a first powder material comprising (in wt %):

Cr 15-18%;

Ti 10-15%;

Al 0-2.5%;

Co 2-4%;

W 3-5%;

Mo 0-2%;

Ta 0-2%;

balance Ni.

In still another embodiment, the braze material 40 comprises an amount of boron and a first powder material comprising (in wt %):

Cr 15-19%;

Ti 8-10%;

Al 0-2.5%;

Co 14-18%;

Mo 12-16%;

balance Ni.

There has been a growing trend in the art to provide braze materials comprising an alloy material that closely or precisely matches the underlying substrate, and that do not include a melting point suppressant such as silicon or boron. Silicon and boron have been and are currently widely used as melting point suppressants in order reduce the incidence of solidification cracking in the resulting brazement. However, their presence can be detrimental due to the formation of brittle phases in the resulting brazement or in the substrate being brazed due to diffusion into the underlying substrate. In accordance with an aspect, the processes described herein allow for the use of boron-containing braze materials without the drawbacks thereof. In this way, the processes described herein may be utilized to provide the benefits thereof during brazing (e.g., lowering melting temperature) yet remove an amount of the boron before complete solidification of the brazement to at least reduce the presence of detrimental boron-containing compounds (phases) in the brazement or component 15 upon cooling.

In accordance with another aspect, the braze material 40 is applied to the component surface within or over the structural defect 36 such that upon brazing (heat treatment) the braze material 40 will melt and flow within the structural defect 36 to fill the same. Upon cooling, the braze material 40 will solidify in order to complete the brazement. In some instances, it may be necessary to at least temporarily anchor or secure the braze material 40 to the component surface prior to brazing. In the case of a PSP, for example, the securement step may be performed by any suitable method known in the art, such as spot welding or the like. Once the heat treatment process is finished, the component 15 may undergo a typical blending or machining process in order to smooth the repaired area of the component 15 before returning the component to service.

In certain embodiments, the component 15 to be repaired includes a plurality of cooling holes or channels (not shown) as are known in the art formed therein. In such cases, it is appreciated that plugs of a suitable material may be inserted into the cooling holes prior to or following application of the braze material 40 (depending on the form thereof). For example, in the case of PSP 44 or foil, the plugs may be inserted through the braze material 40 (covering the component) and into the underlying cooling holes.

In an embodiment, the plugs may be formed from a ceramic material which prevents the braze material 40 from entering the holes during brazing. The plugs may then be subsequently removed by any known chemical or mechanical process. In another embodiment, the plugs may be formed from nickel or other metal or alloy that is beneficial or at least not harmful to the superalloy material of the component 15. Such metal or alloy plugs may melt during the brazing process and may then be removed by re-drilling the cooling holes as necessary.

Once the braze material 40 has been applied as desired or necessary, the component 15 along with the braze material 40 is subjected to a heat treatment

(referred to herein as“brazing” or a“brazing process”) in order to at least melt the braze material 40 and allow travel of the molten braze material into the defect 36. In some instances, the braze material 40 will also flow over a surface of the underlying substrate (component 15). The brazing is done by heating the braze material 40 to a temperature above a solidus temperature of the braze material 40, and holding the temperature above the solidus temperature for an amount of time effective to melt the braze material 40 and allow diffusion of the braze material 40 into the defect 36 to a necessary or desired degree. In an embodiment, the brazing is done in an inert atmosphere (to which hydrogen is added as described below), such as in the presence of argon gas or the like.

In accordance with an aspect, during the brazing process, the component 15 is subjected to alternating stages within a hydrogen environment (“hydrogen stage”) and within a vacuum environment (“vacuum stage”) while heating the braze material 40 and at least a portion of the component 15. In particular, the brazing comprises subjecting the braze material 40 and component 15 to a brazing process, wherein the brazing process comprises alternating between a first stage wherein an amount of hydrogen is introduced into an environment about the component 15 effective to form an amount of boranes (e.g., in the braze material 40, component 15, or the environment about the component 15) and a second stage wherein at least an amount of the formed boranes are removed from the braze material 40, component 15, or the environment about the component 15 via negative pressure.

In the hydrogen stage, an amount of hydrogen is introduced to the environment about the component 15 effective to induce the formation of boron-hydrogen containing compounds, such as boranes. Boranes generally refer to a group of 13 hydride compounds with the generic formula of B_xH_y, such as diborane B₂H₆ and two of its pyrolysis products, pentaborane B₅H₉ and decaborane BioHu. Upon heating and melting of the braze material, it is appreciated that an amount of boron may diffuse into a body of the component, as well as be maintained within the molten braze material.

The hydrogen present (including the added hydrogen) may combine with the boron to form an amount of boranes within the body of the component 15, within the braze material 40, and/or within the atmosphere about the component 15. To accomplish the borane formation, the component is typically provided in a closed environment (closed vessel) within which a suitable amount of hydrogen is introduced from a suitable hydrogen source. In a particular embodiment, the amount of hydrogen introduced is an amount of hydrogen effective to provide a desired degree of borane formation and/or a desired hydrogen partial pressure in the environment about the component 15.

In the vacuum stage, a vacuum or amount of negative pressure is created by any suitable method or structure within a vessel housing the component 15 effective to induce a degree of negative pressure about the component. The negative pressure is, in turn, effective to remove at least a portion of the boranes from the component 15 or environment thereabout. The concentrations, times, temperatures, degree of negative pressure, and any other suitable parameter may be varied so as to achieve a desired degree of borane formation and removal from the component. In addition, the vacuum stage is also effective to remove an amount of the added hydrogen from the

environment and/or the component 15. If not removed, hydrogen may diffuse into the component being repaired. In the case of a nickel-based superalloy, the hydrogen could lead to embrittlement of the component material.

In certain embodiments, the brazing process comprises multiple cycles of alternating through the hydrogen and vacuum stages in order to remove a desired degree of boron from the braze material 40. In a particular embodiment, the component is subjected to at least five alternating cycles in the hydrogen stage and the vacuum stage, wherein each cycle includes a time period in each of the hydrogen stage and the vacuum stage. In addition, the ratio of time in the first stage to the time in the second stage may be any suitable amount of time effective to melt the braze material, as well as reduce an amount of boron relative to the original braze material (e.g., the amount of boron in the braze material 40 prior to initiation of brazing). In an embodiment, a ratio of time in the first stage to time in the second stage is from 4: 1 to 6: 1 . It is appreciated that the amount of time in each stage is an amount of time necessary to achieve a desired degree of melting or a desired degree of reduction in boron. It is appreciated that steps in the brazing process are without limitation and that variations in the brazing process (times, temperatures, ramp rates, etc.) may be dependent on the braze material, the component material, the sizes, shape, and orientation of the defect(s), desired degree of boron removal, or the like.

The temperatures provided as the component 15 and braze material 40 are subjected to brazing may be any suitable temperature program as is known in the art, which may include isocratic or gradient temperature protocols. In an embodiment, the brazing comprises heating the braze material 40 to a first temperature less than a solidus temperature of the braze material 40 and holding at the first temperature for a first duration. The brazing may then further include heating the braze material 40 to a second temperature above a solidus temperature of the braze material 40 and holding at the temperature for a second duration effective to melt the braze material 40. As used herein, the term“solidus temperature” refers to a temperature (or a locus of temperatures on a phase diagram) below which a given substance is completely solid (crystallized).

In certain embodiments, it may be desirable to first bring the temperature above the solidus temperature of the braze material 40 and then back under the same before bringing the brazing temperature back above the solidus temperature (for the primary brazing step). So doing is believed to improve the flow of the braze material 40, particularly in instances of narrower and deeper cracks 36 or the like. In addition, it may be desirable to preheat the component 15 and the braze material 40 to equilibrate the temperature of the component 15 (e.g., from an interior to an exterior of the component) before heating above the solidus temperature to melt the braze material 40.

Accordingly, in a particular embodiment, the brazing may comprise in sequence: heating the braze material 40 to a first temperature less than a solidus

temperature of the braze material 40 and holding at the first temperature for a first duration; and heating the braze material to a second temperature above the solidus temperature of the braze material 40 and holding at the temperature for a second duration effective to melt the braze material 40;

cooling the braze material to a third temperature below the solidus temperature of the braze material 40 for a third duration; and

heating the braze material 40 to a fourth temperature above the solidus temperature of the braze material 40 and holding at the temperature for a fourth duration effective to entirely melt the braze material 40.

In a conventional brazing process, it is typically preferred not to melt a surface of the target component surface as doing so is typically thought to actually increase the amount and/or area of damaged material. However, in an embodiment, against conventional wisdom, a surface layer of the component 15 being repaired may be melted prior to or during brazing to increase the size of and/or strengthen the interface between the braze material and the component as set forth below. As such, the term “brazing” as used herein refers not only to techniques where the braze material 40 is melted at a temperature less than a liquidus temperature of the component 15 so that the component 15 is not melted, but also techniques under which a portion or layer of the component 15 may liquefied or melted to an extent.

The source of heat for the brazing may be any suitable heat source known in the art. In an embodiment, the brazing is done by a laser brazing technique as is known in the art. Brazing that utilizes a laser beam in general is known from U.S. Patent No. 5,902,498, the entirety of which is incorporated by reference. Advantageously, laser brazing allows for localized treatment of the substrate materials so that the complete object need not be subjected to brazing conditions. Alternatively, the brazing may be carried out utilizing any known brazing technique. Preferably, the brazing is done in an inert environment as discussed above to eliminate the need for flux powders, or the like. Alternatively, flux agents may be added to the braze material 10 as are known in the art.

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.

Claims

CLAIMS The invention claimed is:

1. A process for repairing a turbine component (15) having a structural defect (36) comprising:

applying an amount of a braze material (40) comprising boron over and/or within the structural defect (36); and

subjecting the braze material (40) and component (15) to a brazing process to melt the braze material (40) and fill the structural defect (36), wherein the brazing process comprises alternating between a first stage wherein an amount of hydrogen is introduced into an environment about the component (15) effective to form boranes from the boron and the hydrogen in the braze material (40), component (15), or the environment about the component (15) and a second stage wherein the formed boranes are removed via negative pressure.

2. The process of claim 1 , wherein the brazing comprises:

heating the braze material (40) to a first temperature less than a solidus temperature of the braze material (40) and holding at the first temperature for a first duration; and

heating the braze material (40) to a second temperature above a solidus temperature of the braze material (40) and holding at the temperature for a second duration effective to melt the braze material (40).

3. The process of claim 1 , wherein the brazing comprises:

heating the braze material (40) to a second temperature above the solidus temperature of the braze material (40) and holding at the temperature for a second duration effective to melt the braze material (40).

cooling the braze material (40) to a third temperature below the solidus temperature; and

heating the braze material (40) to fourth temperature above the solidus temperature of the braze material (40) and holding at the temperature for a second duration effective to entirely melt the braze material (40).

4. The process of claim 1 , wherein the braze material (40) is in the form of a powder, slurry, paste (42), tape, wire, foil, pre-sintered preform (PSP) (44), and combinations thereof.

5. The process of claim 4, wherein the braze material (40) comprising boron is in the form of a pre-sintered preform (44).

6. The process of claim 1 , wherein a ratio of time in the first stage to time in the second stage is from 4: 1 to 6: 1 .

7. The process of claim 1 , wherein the brazing comprises alternating between the first stage and the second stage for at least five cycles.