Layered Component for Superalloy Product Repair

Abstract

The present invention discloses a layered component for repairing superalloy articles. The present invention provides a method for repairing superalloy articles. In some embodiments, a method for repairing a nickel-based superalloy article includes providing a layered component over a damaged area of the nickel-based superalloy article, the layered component including a nickel-based superalloy preform, an infiltrant alloy preform, and a melting point inhibitor component. The layered component is heated to form a nickel-based filler alloy metallurgically bonded to the damaged area, wherein a primary carbide phase and a secondary carbide phase are present in the nickel-based filler alloy in a combined amount of 0.5 vol% to 10 vol%.

Description

Technical Field

[0001] The present invention relates to methods and compositions for repairing superalloy articles, and more particularly, to a layered assembly that uses a nickel-based superalloy preform in combination with an infiltrant alloy preform. Background Art

[0002] Components of gas turbines, including blades and vanes, are subjected to harsh operating conditions that cause component damage through one or more mechanisms. For example, gas turbine components can be damaged by thermal fatigue cracks, creep, oxidative surface degradation, hot corrosion, and foreign object damage. If left unaddressed, such damage will necessarily compromise the efficiency of the gas turbine and potentially lead to further turbine damage.

[0003] Given such harsh operating conditions, turbine components are typically made of nickel-based or cobalt-based superalloys that exhibit high strength and high temperature resistance. The use of superalloy compositions in combination with complex design and shape requirements makes gas turbines expensive to manufacture. A single-stage vane for an aircraft turbine incurs costs in the tens of thousands of dollars. Additionally, for industrial gas turbines, the cost can exceed one million dollars. Considering such a large capital investment, various methods have been developed to repair turbine components and thereby extend turbine life. Solid-state diffusion bonding, conventional brazing, transient liquid phase bonding (TLP), and wide-gap repair processes have been used in turbine component repair. However, each of these techniques has one or more drawbacks. For example, solid-state diffusion bonding requires expensive fixtures for alignment, the application of high pressure, and tight tolerances for mating surfaces. Such requirements increase costs and limit the turbine locations suitable for repair by this method. Conventional brazing results in a weld with a composition significantly different from that of the superalloy components and is prone to forming brittle eutectic phases. In contrast, TLP provides a weld with a composition and microstructure that are substantially indistinguishable from those of the superalloy components. However, TLP is limited to structural damage or defects of 50 μm or less. As the name implies, the wide-gap repair process overcomes the gap limitation of TLP and addresses defects exceeding 250 μm. Nevertheless, the scale increase provided by the wide-gap repair is offset by the use of a filler alloy composition that contains elements that form brittle intermetallic substances with the superalloy components. The wide-gap method is additionally affected by sintering shrinkage, in which the filler alloy separates from the damaged area of the superalloy article. Such separation can create cracks that are fatal to the repair. Summary of the Invention

[0004] In one aspect, methods of repairing superalloy articles and / or devices using layered components are described herein. Additionally, superalloy articles repaired with such layered components are provided. For example, in some embodiments, a nickel-based superalloy article includes a damaged region and a nickel-based filler alloy metallurgically bonded to the damaged region, the nickel-based filler alloy having a composition of 8 wt% - 15 wt% chromium, 7 wt% - 14 wt% cobalt, 0.1 wt% - 5 wt% molybdenum, 5 wt% - 11 wt% tungsten, 1 wt% - 5 wt% tantalum, 2 wt% - 7 wt% aluminum, 0.1 wt% - 1.5 wt% boron, 0.1 wt% - 5 wt% titanium, 0 wt% - 2 wt% hafnium, 0.05 wt% - 1 wt% carbon, 0 wt% - 0.5 wt% yttrium, and the balance nickel, wherein a primary carbide phase and a secondary carbide phase are present in the nickel-based filler alloy in a combined amount of 0.5 vol% to 10 vol%. In some embodiments, the filler alloy may exhibit mechanical properties comparable to those of the nickel-based superalloy of the article, including tensile strength, ductility, and / or fatigue resistance.

[0005] In some embodiments, a method for repairing a nickel-based superalloy article includes providing a layered component over a damaged region of the nickel-based superalloy article, the layered component including a nickel-based superalloy preform, an infiltrant alloy preform, and a melting point inhibitor component. The layered component is heated to form a nickel-based filler alloy metallurgically bonded to the damaged region, wherein a primary carbide phase and a secondary carbide phase are present in the nickel-based filler alloy in a combined amount of 0.5 vol% to 10 vol%.

[0006] These and other embodiments are further described in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a scanning electron microscope (SEM) image taken at a 70° tilt angle of the nickel-based filler alloy of Example 1 herein for electron backscatter diffraction (EBSD) analysis.

[0008] Figure 2 is to quantify Figure 1 the EBSD analysis of the microstructural phases of the nickel-based filler alloy.

[0009] Figure 3 is a SEM image taken at a 70° tilt angle of the nickel-based filler alloy of Example 2 herein for electron backscatter diffraction EBSD analysis.

[0010] Figure 4 is to quantify Figure 3 the EBSD analysis of the microstructural phases of the nickel-based filler alloy. DETAILED DESCRIPTION

[0011] The embodiments described herein can be more readily understood with reference to the following detailed description and examples, as well as the foregoing and following content. However, the elements, devices, and methods described herein are not limited to the specific embodiments described in the detailed description and examples. It should be recognized that these embodiments merely exemplify the principles of the present invention. Without departing from the spirit and scope of the present invention, various modifications and variations will be apparent to those skilled in the art.

[0012] I. Repaired superalloy article

[0013] In one aspect, a nickel-based superalloy article is described herein that includes one or more damaged regions repaired with a nickel-based filler alloy. The nickel-based filler alloy can become a load-bearing component of the superalloy article and exhibit mechanical properties comparable to those of the nickel-based superalloy forming the article, including tensile strength, ductility, and / or fatigue resistance. In some embodiments, the nickel-based superalloy article includes a damaged region and a nickel-based filler alloy metallurgically bonded to the damaged region, the nickel-based filler alloy having a composition of 8 wt% - 15 wt% chromium, 7 wt% - 14 wt% cobalt, 0.1 wt% - 5 wt% molybdenum, 5 wt% - 11 wt% tungsten, 1 wt% - 5 wt% tantalum, 2 wt% - 7 wt% aluminum, 0.1 wt% - 1.5 wt% boron, 0.1 wt% - 5 wt% titanium, 0 wt% - 2 wt% hafnium, 0.05 wt% - 1 wt% carbon, 0 wt% - 0.5 wt% yttrium, and the balance nickel, wherein the primary carbide phase and the secondary carbide phase are present in the nickel-based filler alloy in a combined amount of 0.5 vol% to 10 vol%. In some embodiments, the nickel-based filler alloy has a composition selected from Table I.

[0014] Table I - Nickel-based filler alloy composition

[0015]

[0016] As described herein, the nickel-based filler alloy can contain the primary carbide phase and the secondary carbide phase in a combined amount of 0.5 vol% to 10 vol%. The volume percentages of the primary carbide phase and the secondary carbide phase can be determined by electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM). Energy-dispersive X-ray analysis (EDS) can also be used to further quantify the primary carbide phase and the secondary carbide phase of the nickel-based filler alloy. In some embodiments, secondary M 23 C6 carbides are present in the filler alloy in an amount of 0.1 vol% to 5 vol%, where M is one or more transition metals selected from chromium, molybdenum, and tungsten. Secondary M 23 C6 carbides can also be present in the nickel-based filler alloy in an amount selected from Table II.

[0017] Table II - M of Ni-based filler alloy 23 C6 (volume%)

[0018] 0.5-4.5 1-5 1.5-4 2-3 0.1-3.5

[0019] M 23 The M6C carbide is typically present at the grain boundaries of the nickel matrix and can exhibit a globular morphology. In some embodiments, the M 23 6C carbide appears as a discontinuous chain of small spheres along the grain boundaries of the nickel matrix. In other embodiments, the M 23 6C carbide can display other morphologies, such as flakes, lamellae, sheets, and / or microporous structures. When located at the grain boundaries, the M 23 6C carbide can increase the hot creep strength by resisting or preventing grain sliding.

[0020] Primary carbides can also be present in the nickel-based filler alloy. In some embodiments, the primary MeC carbide is present in an amount of 0.5 vol% to 5 vol%, where Me is selected from titanium, tantalum, and hafnium. The primary MeC carbide can also be present in the nickel-based filler alloy in an amount selected from Table III.

[0021] Table III - MC (volume %) of Ni-based filler alloy

[0022] 1-4 3-5 0.8-1.5 1-2

[0023] The primary MeC carbide can be non-uniformly distributed throughout the nickel matrix, present at the grain boundaries and / or within the grains of the nickel matrix. Compared to the metal (M) of the M 23 6C carbide, the metal (Me) of the primary carbide can be selected to have a higher affinity for carbon. In such embodiments, the metal of the primary carbide can inhibit or exclude the excessive grain boundary precipitation of M 23 6C carbide. By controlling the grain boundary precipitation of M 23 6C carbide, favorable tensile strength and ductility properties can be achieved. Depending on the infiltration conditions used to form the nickel-based filler alloy, the primary MeC carbide can be present in an amount greater than the secondary M 23 6C carbide in the nickel-based filler alloy. As an alternative, the secondary M 23The C6 carbide is present in an amount greater than that of the primary MeC carbide. In some embodiments, the nickel-based filler alloy also contains the C2Cr3 phase. The C2Cr3 phase can be present at grain boundaries and / or within the grains of the nickel matrix. The C2Cr3 phase is typically present in the nickel-based filler alloy in an amount of 1 vol% - 6 vol%. In some embodiments, the C2Cr3 phase is present in an amount of 3 vol% - 5 vol% or 2 vol% - 4 vol%. The microstructure of the nickel-based filler alloy may also be free or substantially free of brittle metal boride precipitates, including various chromium borides [CrB, (Cr,W)B, Cr(B,C), Cr5B3] and / or nickel borides, such as Ni3B. Additionally, the nickel-based filler alloy can be fully dense or substantially fully dense. When substantially fully dense, the filler alloy can have a porosity of less than 5 vol%.

[0024] In some embodiments, the ultimate tensile strength (σ TS ) of the nickel-based filler alloy at high temperature is at least 30% of the σ TS of the nickel-based superalloy forming the article. In some embodiments, the σ TS of the nickel-based filler alloy is at least 50% or at least 60% of the σ TS of the superalloy article. For example, the σ TS of the nickel-based filler alloy can be 50% - 70% of the σ TS of the superalloy article. Additionally, in some embodiments, the nickel-based filler alloy can exhibit an elongation of at least 2% at high temperature. In some embodiments, the nickel-based filler alloy exhibits an elongation selected from Table IV.

[0025] Table IV - % Elongation of Ni-based filler alloy

[0026] 2-10 2.5-10 3-10 5-10 3-9 3-8

[0027] The σ TS and elongation of the nickel-based filler alloy described herein can be determined according to ASTM E21 - Standard Test Method for High-Temperature Tension Testing of Metallic Materials.

[0028] As described herein, a nickel-based filler alloy is metallurgically bonded to a damaged area of a nickel-based superalloy article. In some embodiments, the damaged area includes one or more dimensions that exceed 1 mm, 5 mm, or 10 mm. For example, the damaged area can be a deep pit or gap in the surface of the nickel-based superalloy article. In other embodiments, the damaged area can be a hole that extends through the surface or wall of the nickel-based superalloy article. In some embodiments, an interfacial transition region can be established between the nickel-based filler alloy and the nickel-based superalloy article. The interfacial transition region can exhibit a microstructure that is different from that of the filler alloy and the nickel-based superalloy article. In some embodiments, the interfacial transition region is free or substantially free of brittle metal boride precipitates, including the chromium boride and nickel boride materials described above. For example, less than 0.5 wt% of metal boride precipitates is demonstrated to be substantially free of such precipitates in the interfacial transition region. In some embodiments, the thickness of the interfacial transition region is 20 μm - 150 μm.

[0029] After the metallurgical bonding of the nickel-based filler alloy over the damaged area, the repaired nickel-based superalloy article can be subjected to additional treatments, including solutionizing and thermal aging. In some embodiments, a protective refractory coating can be applied to the repaired nickel-based superalloy portion. For example, the protective refractory coating can include one or more metal elements selected from aluminum and the metal elements of Groups IVB, VB, and VIB of the periodic table, and one or more non-metal elements selected from Groups IIIA, IVA, VA, and VIA of the periodic table. The protective refractory layer can include carbides, nitrides, carbonitrides, oxycarbonitrides, oxides, or borides of one or more metal elements selected from aluminum and the metal elements of Groups IVB, VB, and VIB of the periodic table. For example, one or more protective layers can be selected from titanium nitride, titanium carbonitride, titanium oxycarbonitride, titanium carbide, zirconium nitride, zirconium carbonitride, hafnium nitride, hafnium carbonitride, and aluminum oxide, and mixtures thereof.

[0030] II. Method for repairing superalloy article

[0031] In another aspect, a method for repairing a superalloy article is provided. A method for repairing a nickel-based superalloy article includes providing a layered assembly over a damaged area of the nickel-based superalloy article, the layered assembly including a nickel-based superalloy preform, an infiltrant alloy preform, and a melting point inhibitor component. The layered assembly is heated to form a nickel-based filler alloy that is metallurgically bonded to the damaged area, wherein a primary carbide phase and a secondary carbide phase are present in the nickel-based filler alloy in a combined amount of 0.5 vol% to 10 vol%. The nickel-based filler alloy can have any composition, microstructure, and / or properties described in Section I herein.

[0032] Turning now to the specific components, the nickel-based superalloy preform may comprise one or more nickel-based superalloy powders. For example, suitable nickel-based superalloy powders may be similar or identical in composition to one or more nickel-based superalloys used to fabricate gas turbine components such as blades and vanes. In some embodiments, the compositional parameters of the nickel-based superalloy powder fall within the nickel-based superalloy classifications of conventional cast alloys, directionally solidified alloys, first-generation single-crystal alloys, second-generation single-crystal alloys, third-generation single-crystal alloys, wrought superalloys, and / or powder-processed superalloys. In some embodiments, the composition of the nickel-based superalloy powder is 0.05 wt% - 0.2 wt% carbon, 7 wt% - 9 wt% chromium, 8 wt% - 11 wt% cobalt, 0.1 wt% - 1 wt% molybdenum, 9 wt% - 11 wt% tungsten, 3 wt% - 4 wt% tantalum, 5 wt% - 6 wt% aluminum, 0.5 wt% - 1.5 wt% titanium, less than 0.02 wt% boron, less than 0.02 wt% zirconium, less than 2 wt% hafnium, and the balance nickel. In certain specific embodiments, the nickel-based superalloy powder components may include alloy powders selected from Table V.

[0033] Table V - Nickel-based superalloy powder composition (wt%)

[0034]

[0035]

[0036] *Nb replaces Ta

[0037] In some embodiments, suitable nickel-based superalloy powders for the preform may be commercially available from various gas turbine manufacturers. Additional commercially available nickel-based superalloy powders for use in the preforms described herein may include MarM247, Rene 108, or CM247LC. In some embodiments, the nickel-based superalloy powder of the preform has a composition listed in Table 1 of Bouse et al., Optimizing Rene N4 Alloy for DS AFT-Stage Bucket Applications in Industrial Gas Turbines, Superalloys 2008, TMS (The Minerals, Metals and Materials Society) 2008, pp. 99 - 108.

[0038] The nickel-based superalloy powder of the preform may have any desired particle size. The particle size can be selected according to various criteria, including but not limited to dispersibility in the fiber polymer matrix, filling characteristics, and / or surface area of interaction and / or reaction with the nickel-based brazing alloy component. In some embodiments, for example, the average particle size of the nickel-based superalloy powder is 10 μm to 100 μm or 30 μm to 70 μm. In some embodiments, the nickel-based superalloy powder is present in the layered assembly in an amount of 45 wt% to 95 wt% of the layered assembly. In some embodiments, the nickel-based superalloy powder is present in the layered assembly in an amount selected from Table VI.

[0039] Table VI - Nickel-based superalloy powder in layered component (wt%)

[0040]

[0041]

[0042] In addition to the nickel-based superalloy preform, the layered assembly further includes an infiltrant alloy preform. In some embodiments, the infiltrant alloy preform comprises a nickel-based brazing alloy powder. Any nickel-based brazing alloy powder that does not violate the purpose of the present invention can be used. For example, the melting point of a suitable nickel-based brazing alloy powder can be lower than that of the nickel-based superalloy powder of the layered assembly. In some embodiments, the melting point of the nickel-based brazing alloy powder is at least 100 °C lower than that of the nickel-based superalloy powder. In a specific embodiment, the nickel-based brazing alloy powder may include an alloy powder having the composition listed in Table VII.

[0043] Table VII - Nickel-based braze alloy powder composition (wt%)

[0044]

[0045] The nickel-based brazing alloy powder having a composition falling within the parameters of Table VII is commercially available under the trade name Amdry D15. Other suitable nickel-based brazing alloy powders can be selected from the Amdry class and other commercially available powders. In other embodiments, the nickel-based brazing alloy powder has the composition of Table VIII.

[0046] Table VIII - Nickel braze alloy components

[0047] Alloy powder Ni wt% Co wt% Cr wt% B wt% Ta wt% Al wt% Y wt% 1 Balance 5-15 10-20 1-4 0-5 0-5 0-0.1 2 Balance 7-12 10-15 2-3 2-3 2.5-5 0-0.1

[0048] Nickel-based brazing alloy powders having a composition falling within the parameters of Table VIII are commercially available under the trade name DF4B. The nickel-based brazing alloy powder of the composite preform can have any desired particle size. The particle size can be selected according to various criteria, including but not limited to dispersibility in the fibrous polymer matrix, packing characteristics, and / or surface area for interaction and / or reaction with the nickel-based superalloy powder. In some embodiments, for example, the average particle size of the nickel-based brazing alloy powder is from 10 μm to 150 μm or from 40 μm to 125 μm. Additionally, the nickel-based brazing alloy powder is typically present in an amount of from 10 wt% to 45 wt% of the layered assembly. In some embodiments, the nickel-based brazing alloy powder is present in the layered assembly in an amount selected from Table IX.

[0049] Table IX - Nickel-based braze powder of layered component (wt%)

[0050] 15-40 25-35 20-30

[0051] The layered assembly can include any number of nickel-based superalloy preforms and infiltration alloy preforms. For example, the layered assembly can include two or more nickel-based superalloy preforms and / or two or more infiltration alloy preforms arranged in any manner. The number of superalloy and / or infiltration alloy preforms can be selected according to various considerations, including the size and nature of the damaged area and the desired compositional properties of the nickel-based filler alloy formed by heating the layered assembly.

[0052] As described herein, in addition to the nickel-based superalloy preform and the nickel-based brazing alloy preform, the layered assembly further includes a melting point inhibitor component. Any melting point inhibitor that does not contravene the purpose of the present invention can be used. For example, suitable melting point inhibitors can include boron, magnesium, hafnium, zirconium, MgNi2, silicon, or combinations thereof. Generally, the melting point inhibitor component is present in an amount of from 0.2 wt% to 5 wt% of the layered assembly. In some embodiments, the melting point inhibitor component contains boron in an amount of from 0.2 wt% to 2 wt% of the layered assembly. In some embodiments, boron is the only substance of the melting point inhibitor component. Alternatively, boron can be combined with one or more additional melting point inhibitor substances. For example, boron can be combined with silicon, hafnium, or MgNi2 to provide the melting point inhibitor component.

[0053] In some embodiments, the melt point inhibitor component is part of a nickel-based brazing alloy powder and / or a nickel-based superalloy powder. The nickel-based brazing alloy and / or nickel-based superalloy may include a melt point inhibitor as part of the alloy composition. For example, the nickel-based brazing alloy powder may be selected to include boron, silicon, and / or hafnium to serve as the melt point inhibitor component. In such embodiments, the nickel-based brazing alloy powder and the nickel-based superalloy powder are present in the layered assembly in a proportion to provide the desired amount of the melt point inhibitor. For example, the nickel-based brazing alloy powder and the nickel-based superalloy powder may be present in the layered assembly in a ratio of 1:1.5 to 1:2. Alternatively, the melt point inhibitor component may be provided to the layered assembly independently of the nickel-based superalloy powder and / or the nickel-based brazing alloy powder. For example, a melt point inhibitor powder may be added to a nickel-based brazing alloy preform and / or a nickel-based superalloy preform.

[0054] In addition, in some embodiments, the nickel-based superalloy preform may also include a certain amount of nickel-based brazing alloy powder. For example, the nickel-based superalloy preform may include the nickel-based brazing alloy powder in an amount of 0.1 wt% to 10 wt% of the layered assembly. Similarly, the nickel-based brazing alloy preform may include a certain amount of nickel-based superalloy powder. In some embodiments, the nickel-based brazing alloy preform may include the nickel-based superalloy powder in an amount of 0.1 wt% to 10 wt% of the layered assembly.

[0055] In some embodiments, the nickel-based superalloy preform and the infiltrant alloy preform can be fabricated as follows. A desired powder alloy composition (e.g., Ni-based superalloy powder and / or Ni-based braze alloy powder) can be combined with an organic carrier for application to one or more damaged surfaces of a superalloy article. Any organic carrier that does not contravene the purpose of the present invention can be used, including solid carriers and liquid carriers. In some embodiments, a suitable organic carrier for the powder alloy composition comprises a fibrous polymer matrix. As described in further detail in the following examples, the fibrous polymer matrix can form a flexible cloth in which the powder alloy composition is dispersed. The flexible polymer cloth can have any thickness that does not contravene the purpose of the present invention. For example, the flexible polymer cloth can typically have a thickness of 0.2 mm - 4 mm or 1 mm - 2 mm. Any polymer type capable of taking the form of fibers or filaments can be used in the matrix construction. Suitable polymer types can include fluoropolymers, polyamides, polyesters, polyolefins, or mixtures thereof. In some embodiments, for example, the fibrous polymer matrix is formed from fibrillated polytetrafluoroethylene (PTFE). In such embodiments, the PTFE fibers or filaments can provide an interconnected network matrix in which the powder alloy composition is dispersed and trapped. Additionally, fibrillated PTFE can be combined with other polymer fibers (such as polyamides and polyesters) to modify or customize the properties of the fiber matrix. The fibrous polymer matrix typically comprises less than 1.5 wt% of the preform. In some embodiments, for example, the fibrous polymer matrix comprises 1.0 wt% - 1.5 wt% or 0.5 wt% - 1.0 wt% of the nickel-based superalloy preform or the infiltrant alloy preform.

[0056] Preforms can be manufactured by various techniques to disperse a powder alloy composition in a fibrous polymer matrix. In some embodiments, a preform is manufactured by combining a polymer powder with a nickel-based superalloy powder and / or a nickel-based braze alloy powder, and machining the mixture to fibrillate the polymer powder and entrap the alloy powder in the resulting fibrous polymer matrix. In a specific embodiment, for example, a powder alloy composition is mixed with 3 vol% - 15 vol% of PTFE powder and machined to fibrillate the PTFE and entrap the powder alloy composition in the fibrous PTFE matrix. As described herein, the nickel-based superalloy powder can have a composition selected from Table IV herein for producing nickel superalloy preforms. Similarly, the nickel-based braze alloy can have a composition selected from Tables VI and VII herein for producing infiltrant alloy preforms. Machining of the powder mixture can include ball milling, rolling, drawing, elongating, extruding, spreading, or a combination thereof. In some embodiments, the resulting PTFE flexible composite preform cloth is subjected to cold isostatic pressing. The preforms described herein can be manufactured according to the disclosure of one or more of U.S. Pat. Nos. 3,743,556, 3,864,124, 3,916,506, 4,194,040, and 5,352,526, each of which is incorporated herein by reference in its entirety.

[0057] In some embodiments, the green density of the nickel-based superalloy preforms described herein is at least 50% of the density of the superalloy article being repaired. In some embodiments, the green density of the nickel-based superalloy preforms is 50% - 75% or 60% - 70% of the superalloy article density.

[0058] A layered assembly is formed by disposing nickel-based superalloy and infiltrant alloy preforms over a damaged area of a nickel-based superalloy article. In some embodiments, the infiltrant alloy preform is disposed over the nickel-based superalloy preform such that the nickel-based braze alloy infiltrates into the nickel-based superalloy particles during heating. In other embodiments, the nickel-based superalloy preform is disposed over the infiltrant alloy preform. The surface of the nickel-based superalloy article can be cleaned by chemical and / or mechanical means (such as by fluoride ion cleaning and / or grinding) and then the layered assembly is applied. Additionally, one or more adhesives can be used to secure the preforms over the damaged area of the nickel-based superalloy article.

[0059] After being applied to a damaged area of a nickel-based superalloy article, the laminated assembly is heated to form a filler alloy that metallurgically bonds to the damaged area. Heating the assembly decomposes the polymer fiber matrix, and the filler alloy is formed from the nickel-based superalloy powder and nickel-based braze alloy of the preform. The assembly is typically heated to a temperature that is above the melting point of the nickel-based braze alloy powder and below the melting point of the nickel-based superalloy powder. Accordingly, the nickel-based braze alloy powder and the nickel-based superalloy powder are melted to form the filler alloy, where the filler alloy is metallurgically bonded to the nickel-based superalloy part. The molten flow characteristics of the nickel-based braze alloy may allow for the formation of a void-free interface between the filler alloy and the nickel-based superalloy part. The heating temperature and heating time period depend on the specific compositional parameters of the nickel-based superalloy part and the laminated assembly. In some embodiments, for example, the assembly is heated in a vacuum to a temperature of 1180 °C - 1250 °C for a time period of 1 hour to 4 hours. In some embodiments, after heating to the peak temperature, the assembly may be held at 800 °C - 1000 °C for a time period of 0.5 hour - 5 hours. The resulting filler alloy may have any of the compositions, microstructures, and / or mechanical properties described in Section I above. After the metallurgical bonding of the filler alloy above the damaged area, the repaired nickel-based superalloy part may be subjected to additional processing, including solutionizing and thermal aging.

[0060] These and other embodiments are further illustrated in the following non-limiting examples.

[0061] Example 1 - Nickel-based filler alloy

[0062] A nickel-based filler alloy sheet is formed from the laminated assembly described herein. A powder composition is provided that includes a nickel-based superalloy powder having the parameters of alloy powder 1 (Rene' 108) of Table V and a nickel-based braze alloy powder having the parameters of alloy powder 2 of Table VIII. 99 weight % of the powder composition is formed from the nickel-based superalloy, and the remaining 1 weight % is formed from the nickel-based braze alloy.

[0063] The powder composition is mixed with 5 volume % - 15 volume % of powdered PTFE. The resulting mixture is machined to fibrillate the PTFE and entrap the nickel-based superalloy powder and the nickel-based braze alloy powder, and then rolled to form a cloth-like flexible sheet having a thickness of 1 mm - 2 mm of the nickel-based superalloy preform. The process is repeated to form the infiltrant alloy preform, except that the powder composition mixed with the PTFE includes 99 weight % of the nickel-based braze alloy powder and 1 weight % of the nickel-based superalloy powder.

[0064] Place a nickel-based superalloy preform above a graphite-based substrate. Arrange an infiltrant alloy preform above the nickel-based superalloy preform to complete the layered assembly. The nickel-based superalloy powder is present in the layered assembly in an amount of 66 wt% - 68 wt%, while the nickel-based brazing alloy powder is present in the layered assembly in an amount of 32 wt% - 34 wt%.

[0065] Heat the layered assembly in a vacuum furnace to 1190 °C - 1200 °C for a period of 2 hours, then heat at 1080 °C - 1090 °C for two hours. Subsequently, maintain the heating at 870 °C - 880 °C for a period of 4 hours, and then cool. Cut the resulting nickel-based filler alloy plate by laser into 4 × 4 inches and disk grind it to 0.040 inches. Figure 1 is a SEM image of the plate taken at an inclination angle of 70° for EBSD analysis. The arrows in the SEM image correspond to Figure 2 the arrows in the EBSD image that detail the various microstructural phases. As Figure 2 provided, the primary carbides of TiC and the secondary carbides of Cr 23 C6 are present along the grain boundaries of the nickel matrix. TiC is also found in the grains of the nickel matrix. The C2Cr3 phase is also present within the nickel matrix grains and along the matrix grain boundaries. The volume percentages of the respective phases are provided in Table X.

[0066] Table X - Phases of nickel-based filler alloy

[0067] Phase Volume % TiC 3.38 <![CDATA[Cr 26 C3]]> 2.39 <![CDATA[C2Cr3]]> 3.15 Ni matrix 86.5

[0068] Test the high-temperature (1800 °F) tensile strength and % elongation of the nickel-based filler alloy plate according to ASTM E21. The results are provided in Table XI.

[0069] Table XI - Tensile and % elongation

[0070] <![CDATA[UTS(σ TS ),ksi]]> <![CDATA[Rene'108σ TS Percentage]]> % Elongation 30.4 37.2 3

[0071] As provided in Table X, the σ TS of the nickel-based filler alloy is 37.2% of the σ TS of Rene'108.

[0072] Example 2 - Nickel-based filler alloy

[0073] The nickel-based filler alloy plate is formed from the layered assembly described hereinbelow. A powder composition is provided, which comprises a nickel-based superalloy powder having the parameters of alloy powder 2 (Mar M247) of Table V and a nickel-based brazing alloy powder having the parameters of alloy powder 2 of Table VIII. 99 wt% of the powder composition is formed from the nickel-based superalloy, and the remaining 1 wt% is formed from the nickel-based brazing alloy.

[0074] The powder composition is mixed with 5 vol% - 15 vol% of powdered PTFE. The resulting mixture is machined to fibrillate the PTFE and entrap the nickel-based superalloy powder and nickel-based brazing alloy powder, and then rolled to form a nickel-based superalloy preform into a cloth-like flexible sheet having a thickness of 1 mm - 2 mm. The process is repeated to form an infiltrated alloy preform, except that the powder composition mixed with the PTFE contains 99 wt% of nickel-based brazing alloy powder and 1 wt% of nickel-based superalloy powder.

[0075] The nickel-based superalloy preform is placed above a graphite-based substrate. The infiltrated alloy preform is arranged above the nickel-based superalloy preform to complete the layered assembly. The nickel-based superalloy powder is present in the layered assembly in an amount of 66 wt% - 68 wt%, while the nickel-based brazing alloy powder is present in the layered assembly in an amount of 32 wt% - 34 wt%.

[0076] The layered assembly is heated in a vacuum furnace to 1190 °C - 1200 °C for a period of 2 hours, and then heated at 1080 °C - 1090 °C for two hours. Subsequently, the heating is maintained at 870 °C - 880 °C for a period of 4 hours and then cooled. The resulting nickel-based filled alloy plate is laser cut into 4 × 4 inches and disk ground to 0.040 inches. Figure 3 is an SEM image of the plate taken at an inclination angle of 70° for EBSD analysis. The arrows in the SEM image correspond to Figure 4 the arrows in the EBSD image that detail the various microstructural phases. As Figure 4 provided, the primary carbides of TiC and the secondary carbides of Cr 23 C6 are present along the grain boundaries of the nickel matrix. TiC is also found in the grains of the nickel matrix. The C2Cr3 phase is also present within the nickel matrix grains and along the matrix grain boundaries. The volume percentages of the individual phases are provided in Table XII.

[0077] Table XII - Phases of nickel-based filler alloy

[0078] Phase Volume % TiC 1.09 <![CDATA[Cr 26 C3]]> 2.88 <![CDATA[C2Cr3]]> 4.32 Ni matrix 86.8

[0079] The high-temperature (1800 °F) tensile strength and % elongation of the nickel-based filled alloy plate are tested according to ASTM E21. The results are provided in Table XIII.

[0080] Table XIII - Tensile and % elongation

[0081] <![CDATA[UTS(σ TS ),ksi]]> <![CDATA[Mar M247σ TS percentage]]> % Elongation 32 35.3 8-10

[0082] As provided in Table IX, the σ of the nickel-based filled alloy TS is the σ of Mar M247 TS35.3% of

[0083] For achieving multiple objects of the present invention, multiple embodiments of the present invention have been described. It should be recognized that these embodiments merely exemplarily illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, various modifications and variations thereof will be obvious to those skilled in the art.

Claims

1. A nickel-based superalloy article, comprising: A damaged area; And A nickel-based filler alloy metallurgically bonded to the damaged area, wherein during the metallurgical bonding process, the nickel-based brazing alloy in the nickel-based filler alloy melts, while the nickel-based superalloy in the nickel-based filler alloy does not melt, and the composition of the nickel-based filler alloy is 8 wt% - 15 wt% chromium, 7 wt% - 14 wt% cobalt, 0.1 wt% - 5 wt% molybdenum, 5 wt% - 11 wt% tungsten, 1 wt% - 5 wt% tantalum, 2 wt% - 7 wt% aluminum, 0.1 wt% - 1.5 wt% boron, 0.1 wt% - 5 wt% titanium, 0 wt% - 2 wt% hafnium, 0.05 wt% - 1 wt% carbon, 0 wt% - 0.5 wt% yttrium, and the balance nickel, wherein the primary carbide phase and the secondary carbide phase are present in the nickel-based filler alloy in a combined amount of 0.5 vol% to 10 vol%.

2. The nickel-based superalloy article according to claim 1, wherein the composition of the nickel-based filler alloy is 10 wt% - 12 wt% chromium, 9 wt% - 11 wt% cobalt, 0.3 wt% - 0.5 wt% molybdenum, 5 wt% - 7 wt% tungsten, 2 wt% - 3 wt% tantalum, 4 wt% - 5 wt% aluminum, 0.7 wt% - 1 wt% boron, 0.5 wt% - 0.8 wt% titanium, 0.6 wt% - 1 wt% hafnium, 0.05 wt% - 0.2 wt% carbon, 0 wt% - 0.5 wt% yttrium, and the balance nickel.

3. The nickel-based superalloy article according to claim 1, wherein the secondary M 23 C6 carbide is present in an amount of 1 vol% to 4 vol% of the nickel-based filler alloy.

4. The nickel-based superalloy article according to claim 1, wherein the secondary M 23 C6 carbide is present in an amount of 2 vol% to 3 vol% of the nickel-based filler alloy.

5. The nickel-based superalloy article according to claim 3, wherein M is one or more transition metals selected from chromium, molybdenum, and tungsten.

6. The nickel-based superalloy article according to claim 3, wherein the primary MeC carbide is present in the nickel-based filler alloy in an amount of 0.5 vol% to 5 vol% of the nickel-based filler alloy.

7. The nickel-based superalloy article according to claim 6, wherein Me is selected from titanium, tantalum, and hafnium.

8. The nickel-based superalloy article according to claim 6, wherein the nickel-based filler alloy further comprises a C2Cr3 phase.

9. The nickel-based superalloy article according to claim 1, wherein according to ASTM E21 - Standard Test Method for High-Temperature Tension Testing of Metallic Materials, the tensile strength of the nickel-based filler alloy is 50% - 70% of the tensile strength of the nickel-based superalloy article.

10. The nickel-based superalloy article according to claim 9, wherein according to ASTM E21 - Standard Test Method for High-Temperature Tension Testing of Metallic Materials, the nickel-based filler alloy has an elongation of at least 2%.

11. The nickel-based superalloy article according to claim 10, wherein according to ASTM E21 - Standard Test Method for High-Temperature Tension Testing of Metallic Materials, the nickel-based filler alloy has an elongation of at most 10%.

12. The nickel-based superalloy article according to claim 1, wherein the damaged area includes holes in the surface of the nickel-based superalloy article.

13. A method for repairing a nickel-based superalloy article, comprising: A layered component is provided above the damaged area of the nickel-based superalloy article, the layered component comprising a nickel-based superalloy preform, an infiltrant alloy preform, and a melting point inhibitor component, the nickel-based superalloy preform comprising nickel-based superalloy powder; and The layered component is heated to form a nickel-based filler alloy metallurgically bonded to the damaged area, wherein primary carbide phase and secondary carbide phase are present in the nickel-based filler alloy in a combined amount of 0.5 vol% to 10 vol%, and during heating, the nickel-based superalloy powder does not melt.

14. The method according to claim 13, wherein the secondary M 23 C6 carbide is present in an amount of 1 vol% to 4 vol% of the nickel-based filler alloy.

15. The method according to claim 14, wherein M is one or more transition metals selected from chromium, molybdenum, and tungsten.

16. The method according to claim 15, wherein the primary MeC carbide is present in the nickel-based filler alloy in an amount of 0.5 vol% to 5 vol%.

17. The method according to claim 16, wherein Me is selected from titanium, tantalum, and hafnium.

18. The method according to claim 13, wherein the composition of the nickel-based filler alloy is 8 wt%-15 wt% chromium, 7 wt%-14 wt% cobalt, 0.1 wt%-5 wt% molybdenum, 5 wt%-11 wt% tungsten, 1 wt%-5 wt% tantalum, 2 wt%-7 wt% aluminum, 0.1 wt%-1.5 wt% boron, 0.1 wt%-5 wt% titanium, 0 wt%-2 wt% hafnium, 0.05 wt%-1 wt% carbon, 0 wt%-0.5 wt% yttrium, and the balance nickel.

19. The method according to claim 13, wherein the composition of the nickel-based filler alloy is 10 wt%-12 wt% chromium, 9 wt%-11 wt% cobalt, 0.3 wt%-0.5 wt% molybdenum, 5 wt%-7 wt% tungsten, 2 wt%-3 wt% tantalum, 4 wt%-5 wt% aluminum, 0.7 wt%-1 wt% boron, 0.5 wt%-0.8 wt% titanium, 0.6 wt%-1 wt% hafnium, 0.05 wt%-0.2 wt% carbon, 0 wt%-0.5 wt% yttrium, and the balance nickel.

20. The method according to claim 13, wherein according to ASTM E21 - Standard Test Method for High-Temperature Tension Testing of Metallic Materials, the tensile strength of the nickel-based filler alloy is 50%-70% of the tensile strength of the nickel-based superalloy article.

21. The method according to claim 20, wherein according to ASTM E21 - Standard Test Method for High-Temperature Tension Testing of Metallic Materials, the nickel-based filler alloy has an elongation of at least 2% and at most 10%.

22. The method according to claim 13, wherein the composition of the nickel-based superalloy powder is 0.05 wt% - 0.2 wt% of carbon, 7 wt% - 9 wt% of chromium, 8 wt% - 11 wt% of cobalt, 0.1 wt% - 1 wt% of molybdenum, 9 wt% - 11 wt% of tungsten, 2 wt% - 4 wt% of tantalum, 5 wt% - 6 wt% of aluminum, 0.5 wt% - 1.5 wt% of titanium, less than 0.02 wt% of boron, less than 0.02 wt% of zirconium, 0 wt% - 3 wt% of hafnium, and the balance of nickel.

23. The method according to claim 22, wherein the melting point inhibitor component comprises at least one of boron, silicon, magnesium, hafnium, zirconium, and MgNi2.

24. The method according to claim 23, wherein the infiltration alloy preform comprises the melting point inhibitor component.

25. The method according to claim 24, wherein the nickel-based superalloy powder is present in the layered assembly in an amount of 50 wt% - 80 wt%.

26. The method according to claim 13, wherein the green density of the nickel-based superalloy preform is 60% to 70% of the density of the nickel-based superalloy article.

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