Nickel-based brazing filler metal for brazing single-crystal high-temperature alloy DD10 and preparation method and brazing method of nickel-based brazing filler metal

Abstract

The invention discloses nickel-based brazing filler metal for brazing single-crystal superalloy DD10 and a preparation method and a brazing method of the nickel-based brazing filler metal, and belongs to the field of nickel-based superalloy brazing. In the nickel-based brazing filler metal, the total atom percentage content of Al, Ti, Ta and Nb is 12 at.%-16 at.%, and the total atom percentage content of B and Si is 1.5 at.%-2.0 at.%. Compared with traditional nickel-based brazing filler metal, the high-temperature strength and toughness of the single-crystal high-temperature alloy DD10 brazed joint are synergistically improved by regulating and controlling the volume fraction and size of the gamma'phase in a brazing seam, the volume fraction of the brittle phase is reduced to 5% or below, the problem of high-temperature embrittlement is solved, and the creep fracture time of the single-crystal high-temperature alloy DD10 brazed joint at 1000 DEG C / 100 MPa reaches 350-400 h.

Description

Technical Field

[0001] This invention relates to the field of brazing nickel-based superalloys, specifically to nickel-based brazing filler metal for brazing single-crystal superalloy DD10, its preparation method, and brazing method. Background Technology

[0002] The next generation of aero-engines is iterating towards higher thrust-to-weight ratios (≥12), and high-pressure turbine blades are operating at temperatures exceeding 1100℃, requiring them to withstand complex thermal cycles and alternating loads. This places stringent demands on the high-temperature mechanical properties, creep resistance, and corrosion resistance of the connecting joints. The single-crystal high-temperature alloy DD10, with its single-crystal structure eliminating grain boundary weakening effects, achieves a creep strength exceeding 350MPa at 1000℃, making it a core material for high-pressure turbine blades.

[0003] In the joining process of single-crystal superalloy DD10, laser welding / electron beam welding is prone to recrystallization of the single-crystal matrix due to concentrated heat input, resulting in a sharp drop in high-temperature performance; diffusion welding requires holding at 1250℃ / 15MPa for 8-12 hours, which has low production efficiency and is prone to elemental segregation of the base material; friction welding is only suitable for simple components such as shafts and cannot be matched with complex structures such as blade tenons and film cooling holes. Brazing, due to its low heat input (peak temperature ≤1250℃), can avoid single-crystal recrystallization, and the molten brazing filler metal can fill complex gaps with a rate of over 99%, making it the preferred technology for joining single-crystal superalloy DD10.

[0004] Existing nickel-based brazing filler metals (such as BNi-2 and BNi-5) have three major defects: ① Insufficient interfacial bonding strength (room temperature shear strength ≤700MPa) due to poor γ' matching between the filler metal and the single-crystal superalloy DD10; ② Prone to the precipitation of bulk borides (such as Ni3B) and silicides (such as Ni2Si) at high temperatures, with the brittle phase volume fraction reaching 15%-20% at 1000℃, resulting in a creep fracture time of ≤100h for the joint; ③ Limited resistance to high-temperature oxidation (oxidation weight gain ≥8mg / cm³ after 100h of cyclic oxidation at 1000℃). 2 Therefore, developing a nickel-based brazing filler metal with precisely controlled composition adapted to DD10 has become the key to overcoming the bottleneck of high-temperature connections in aero-engines. Summary of the Invention

[0005] To address the shortcomings in the prior art, this invention improves the microstructure of the brazed joint of DD10 monocrystalline superalloy by redesigning the brazing filler metal composition, thereby enhancing the mechanical properties of the joint and providing technical support for the high-strength and high-toughness connection of DD10 monocrystalline superalloy.

[0006] To achieve the above objectives, the first aspect of the present invention provides a nickel-based brazing filler metal for brazing a single-crystal high-temperature alloy DD10. The nickel-based brazing filler metal is composed of the following elements by atomic percentage: Co 8.5at.%-9.5at.%, Cr 7.5at.%-8.5at.%, Mo 2.2at.%-2.8at.%, W 1.2at.%-1.8at.%, Al 4.5at.%-5.5at.%, Ti 2.5at.%-3.5at.%, Ta 3.5at.%-4.5at.%, Nb 1.5at.%-2.5at.%, B 0.9at.%-1.1at.%, Si 0.6at.%-0.9at.%, La 0.15at.%-0.25at.%, Nd 0.12at.%-0.18at.%, with the balance being Ni. The total atomic percentage of Al, Ti, Ta, and Nb is 12 at.%-16 at.%, and the total atomic percentage of B and Si is 1.5 at.%-2.0 at.%.

[0007] The second aspect of this invention provides a method for preparing a nickel-based brazing filler metal for brazing a single-crystal high-temperature alloy DD10, the method comprising the following steps: Step 1: Weigh out Ni, Co, Cr, Al, Ta, Ti, Mo, Nb, W, B, Si, La, and Nd powders according to the above atomic percentages of nickel-based solder. After cleaning and drying, mix them using a double planetary mixer to obtain mixed powder. Step 2: After preparing the melt from the mixed powder using induction melting, foil-shaped brazing filler metal is prepared using twin-roll casting. Step 3: The foil-shaped brazing filler metal is subjected to stress-relief annealing, followed by ultrasonic cleaning with anhydrous ethanol, deionization rinsing, and drying to obtain the nickel-based brazing filler metal.

[0008] Preferably, the cleaning process in step one involves ultrasonic cleaning with anhydrous ethanol for 20 minutes, and the drying process involves drying in a vacuum drying oven at 85°C for 40 minutes.

[0009] Preferably, in the process of preparing foil-shaped brazing filler metal by twin-roll casting and rolling in step two, the melt is introduced into a twin-roll mill using a bottom-pouring tundish. The roll gap of the twin-roll mill is 0.045 mm-0.055 mm, and the roll speed is 1900 rpm-2100 rpm, and the foil-shaped brazing filler metal is obtained by rolling.

[0010] Preferably, the thickness of the foil-shaped solder is 45μm-55μm.

[0011] Preferably, the stress-relief annealing temperature in step three is 650°C, the annealing time is 80 min, and the furnace is cooled at a rate of 25°C / h-30°C / h.

[0012] The third aspect of this invention proposes a brazing method for single-crystal high-temperature alloy DD10, wherein the above-mentioned nickel-based brazing filler metal is placed between two pretreated single-crystal high-temperature alloy DD10 base materials, and then placed together in a vacuum brazing furnace for brazing to obtain a single-crystal high-temperature alloy DD10 brazed joint.

[0013] Preferably, the brazing employs a gradient heating and pressurization method, specifically as follows: First stage: heating from room temperature to 350℃ at a heating rate of 8℃ / min, applying a pressure of 0.5MPa, and holding at 350℃ for 15min; Second stage: heating from 350℃ to 750℃ at a heating rate of 8℃ / min, applying a pressure of 0.8MPa, and holding at 750℃ for 15min; Third stage: heating from 750℃ to 1050℃ at a heating rate of 8℃ / min, applying a pressure of 1.0MPa, and holding at 1050℃ for 15min; Fourth stage: heating from 1050℃ to a welding temperature of 1220℃ at a heating rate of 5℃ / min, applying a pressure of 1.2MPa, and holding at a welding temperature of 1250℃ for 180min, followed by furnace cooling to room temperature; the vacuum degree of the vacuum brazing furnace... .

[0014] Preferably, the volume fraction of the γ' phase in the brazed joint of the single-crystal high-temperature alloy DD10 is 40%-45%, and the size of the γ' phase is 0.2μm-0.5μm.

[0015] Preferably, the single-crystal high-temperature alloy DD10 brazed joint has a creep rupture time of 350h-400h under the conditions of 1000℃ and 100MPa; and a shear strength of 480MPa-500MPa at 1000℃.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention improves the high-temperature strength and toughness of DD10 single-crystal superalloy brazed joints by controlling the volume fraction and size of the γ' phase in the brazing seam. By controlling the total content of B and Si and purifying rare earth elements, the volume fraction of brittle phases is reduced to below 5%, solving the problem of high-temperature embrittlement. The prepared DD10 single-crystal superalloy brazed joints have a room temperature shear strength of 820MPa-840MPa and a high-temperature shear strength of 480MPa-500MPa at 1000℃ (25%-30% higher than traditional brazing fillers). The creep rupture time of the DD10 single-crystal superalloy brazed joints at 1000℃ / 100MPa is 350h-400h (250%-300% higher than traditional brazing fillers). The brazing filler metal prepared by this invention has better wettability (contact angle ≤12°) and gap filling rate (≥99.5%) for single-crystal superalloy DD10 than traditional brazing filler metals, which can realize efficient and reliable connection of complex single-crystal superalloy DD10 components and meet the stringent service requirements of the new generation of aero engines. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention, wherein: Figure 1 This is a SEM image of the single-crystal high-temperature alloy DD10 brazed joint provided in Embodiment 1 of the present invention.

[0018] Figure 2 This is a SEM image of the single-crystal high-temperature alloy DD10 brazed joint provided in Comparative Example 5 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0020] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein.

[0021] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] This invention provides a nickel-based brazing filler metal for DD10 single-crystal high-temperature alloy. The nickel-based filler metal is composed of the following elements by atomic percentage: Co 8.5 at.%-9.5 at.%, Cr 7.5 at.%-8.5 at.%, Mo 2.2 at.%-2.8 at.%, W 1.2 at.%-1.8 at.%, Al 4.5 at.%-5.5 at.%, Ti 2.5 at.%-3.5 at.%, Ta 3.5 at.%-4.5 at.%, Nb 1.5 at.%-2.5 at.%, B 0.9 at.%-1.1 at.%, Si 0.6 at.%-0.9 at.%, La 0.15 at.%-0.25 at.%, Nd 0.12 at.%-0.18 at.%, balance Ni; wherein, the total atomic percentage of Al, Ti, Ta, and Nb is preferably 12 at.%-16 at.%, for example, 12 at.%, 13 at.%, 14 at.%, 15 at.%, 16 at.%, and the total atomic percentage of B and Si is preferably 1.5 at.%-2.0 at.%, for example, 1.5 at.%, 1.6 at.%, 1.7 at.%, 1.8 at.%, 1.9 at.%, 2.0 at.%.

[0023] In some embodiments of the present invention, the strategy of using the above-mentioned nickel-based brazing filler metal is as follows: Co and Ni form a continuous solid solution, which improves the high-temperature strength of the γ-phase matrix of the brazing filler metal (the matrix hardness is increased by 15%-20% at 1000℃); Cr can form a dense Cr2O3 oxide film at the interface (the film thickness is controlled at 2μm-3μm), while avoiding the precipitation of σ phase (brittle intermetallic compound) due to excessive Cr. By controlling the total atomic percentage of Al, Ti, Ta, and Nb at 12at.%-16at.%, the volume fraction of γ' phase (Ni3Al / Ni3Ti / Ni3Ta) in the brazing seam is 40%-45%, and the size of γ' phase is 0.2μm-0.5μm. Among them, Ta can improve the high-temperature stability of γ' phase, and Nb can inhibit the coarsening of γ' phase, achieving synergistic effect of fine grain strengthening and precipitation strengthening; La can purify the grain boundaries and reduce S and P. To reduce impurity content to ≤5ppm, grain boundary embrittlement is reduced; Nd can refine the γ' phase and carbides (such as TiC, TaC), improving oxide film adhesion.

[0024] The preparation process of the above-mentioned nickel-based solder is as follows: Step 1: Weigh out Ni, Co, Cr, Al, Ta, Ti, Mo, Nb, W, B, Si, La, and Nd powders in an argon-protected glove box according to the above-mentioned atomic percentages of nickel-based solder. The powder particle size should be 5μm-10μm, and the specific surface area should be ≥1.5m². 2 / g, using anhydrous ethanol-ultrasonic (300W power, 40kHz frequency) synergistic cleaning for 20min to remove oil and oxides adsorbed on the powder surface, followed by vacuuming to ≤5×10 -3 In a vacuum drying oven at 85°C for 40 minutes, the powder was kept at 85°C to prevent agglomeration. A double planetary mixer was used to mix the powder at 300 rpm for 2 hours to achieve a mixing uniformity of over 98% and an elemental deviation of ≤0.1 at.%.

[0025] Step 2: After preparing the melt from the mixed powder using induction melting, foil-shaped brazing filler metal is prepared using twin-roll casting. First, the mixed powder is added to a water-cooled copper crucible vacuum induction furnace, and the furnace is evacuated to a vacuum level of 1×10⁻⁶. -3 The pressure is increased to 800℃ and held for 30 minutes; then high-purity argon gas is introduced to 0.12MPa, the temperature is increased to 1500℃, and electromagnetic stirring is performed at a power of 5kW for 25 minutes to ensure complete dissolution of refractory elements (such as Ta and W) to obtain a melt; then, the melt is stably introduced into a twin-roll mill using a bottom-pouring tundish with a roll gap of 0.045mm-0.055mm (±0.002mm) and a roll speed of 1900rpm-2100rpm to roll it into a foil-shaped brazing filler metal with a thickness of 45μm-55μm and a thickness deviation of ≤±2μm; argon gas protection is used during the casting and rolling process to avoid oxidation of the melt.

[0026] Step 3: Place the foil-shaped solder into a vacuum. In a vacuum annealing furnace, the temperature was increased to 650℃ at a heating rate of 5℃ / min and held for 80min to eliminate casting and rolling stress. The furnace was then cooled at a rate of 25℃ / h-30℃ / h to below 100℃ to avoid secondary stress generation. The surface was ultrasonically cleaned with anhydrous ethanol for 25min at a power of 200W to remove oil stains. The surface was then rinsed three times with deionized water. Finally, the surface was held in a vacuum drying oven at 75℃ for 25min to obtain nickel-based brazing filler metal with a surface roughness Ra≤0.2μm.

[0027] The process of brazing single-crystal superalloy DD10 using the nickel-based solder prepared in this invention is as follows: First, the DD10 monocrystalline high-temperature alloy base material is pretreated by sequentially polishing with 180#, 280#, 400#, 600#, 800#, 1200#, 1600#, and 2000# silicon carbide wet sandpaper, followed by chemical mechanical polishing with 120nm silicon dioxide polishing slurry to achieve a surface roughness Ra≤0.05μm. Then, it is ultrasonically cleaned in anhydrous ethanol (250W power) for 20 minutes to remove surface debris. Next, it is soaked in dilute hydrochloric acid for 5 minutes to activate the surface oxide film. After rinsing three times with deionized water, it is dried using a high-purity nitrogen gun (purity ≥99.999%) to prevent surface moisture adsorption. The aforementioned nickel-based solder is then placed between the upper and lower pretreated single-crystal superalloy DD10 base material, with the assembly gap controlled at 50μm-60μm, and then placed together under vacuum. Brazing is performed in a vacuum brazing furnace using a gradient heating and pressurization method. The specific process is as follows: The process involves four stages: First, heating from room temperature to 350°C at a rate of 8°C / min, applying a pressure of 0.5 MPa, and holding at 350°C for 15 minutes. Second, heating from 350°C to 750°C at a rate of 8°C / min, applying a pressure of 0.8 MPa, and holding at 750°C for 15 minutes. Third, heating from 750°C to 1050°C at a rate of 8°C / min, applying a pressure of 1.0 MPa, and holding at 1050°C for 15 minutes. Fourth, heating from 1050°C to a welding temperature of 1220°C at a rate of 5°C / min, applying a pressure of 1.2 MPa, and holding at 1250°C for 180 minutes, followed by furnace cooling to room temperature to prevent cracking due to thermal stress.

[0028] The present invention will be further described below through specific embodiments.

[0029] Example 1 In this embodiment, a nickel-based brazing filler metal with atomic percentages of Co 8.5 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 1.1 at.%, Si 0.9 at.%, La 0.25 at.%, Nd 0.18 at.%, Ta 4.5 at.%, Nb 2.5 at.%, and Ni 60.07 at.% was used to braze the single-crystal superalloy DD10. The specific process is as follows: Step 1: Weigh the powders Co, Mo, W, Cr, Al, Ti, B, Si, La, Nd, Ta, Nb, and Ni in an argon-protected glove box according to the atomic percentages of the constituent elements of the nickel-based solder. Clean the powders with anhydrous ethanol and ultrasonic for 20 minutes to remove oil and oxides adsorbed on the powder surface. After cleaning, place the powders in a vacuum drying oven and keep them at 85°C for 40 minutes. Mix the powders for 2 hours using a double planetary mixer at 300 rpm, achieving a mixing uniformity of 98% and an elemental deviation of ≤0.1 at.%.

[0030] Step 2: Add the mixed powder to a water-cooled copper crucible vacuum induction furnace, and first evacuate the furnace to a vacuum level of 1×10⁻⁶. -3The pressure is increased to 800℃ and held for 30 minutes; then high-purity argon gas is introduced to 0.12MPa, the temperature is increased to 1500℃, and the mixture is electromagnetically stirred (stirring power 5kW) and held for 25 minutes to obtain a melt. The melt is then steadily introduced into a twin-roll mill using a bottom-pouring tundish, with the roll gap precisely controlled at 0.045mm and the roll speed at 1900rpm, to roll it into a foil-shaped brazing filler metal with a thickness of 45μm.

[0031] Step 3: The prepared foil-shaped brazing filler metal is subjected to stress-relief annealing at a temperature of 650℃ for 80 min. After annealing, it is cooled to below 100℃ in the furnace at a rate of 30℃ / h to avoid secondary stress. The foil-shaped brazing filler metal is then ultrasonically cleaned with anhydrous ethanol (200W) for 25 min to remove surface oil. It is then rinsed three times with deionized water. Finally, it is kept in a vacuum drying oven at 75℃ for 25 min to obtain nickel-based brazing filler metal with a surface roughness Ra≤0.2μm.

[0032] Step 4: The DD10 monocrystalline superalloy base material is sequentially polished with 180#, 280#, 400#, 600#, 800#, 1200#, 1600#, and 2000# silicon carbide wet sandpaper, then chemically and mechanically polished with 120nm silicon dioxide polishing slurry. It is then ultrasonically cleaned in anhydrous ethanol for 20 minutes, soaked in dilute hydrochloric acid for 5 minutes, rinsed three times with deionized water, and dried with a high-purity nitrogen gun to obtain the pretreated DD10 monocrystalline superalloy base material. Nickel-based brazing filler metal is placed between the upper and lower layers of the pretreated DD10 monocrystalline superalloy base material, and both are placed under a vacuum of ≤2×10⁻⁶. 3 Brazing is performed in a vacuum brazing furnace under Pa. The specific brazing process is as follows: The process involves four stages: First, heating from room temperature to 350°C at a rate of 8°C / min, applying a pressure of 0.5 MPa, and holding at 350°C for 15 minutes. Second, heating from 350°C to 750°C at a rate of 8°C / min, applying a pressure of 0.8 MPa, and holding at 750°C for 15 minutes. Third, heating from 750°C to 1050°C at a rate of 8°C / min, applying a pressure of 1.0 MPa, and holding at 1050°C for 15 minutes. Fourth, heating from 1050°C to a welding temperature of 1220°C at a rate of 5°C / min, applying a pressure of 1.2 MPa, holding at a welding temperature of 1250°C for 180 minutes, and then cooling to room temperature in the furnace.

[0033] The SEM microstructure of the joint obtained after brazing in this embodiment is as follows: Figure 1As shown, the joint achieved isothermal solidification, the weld was clean, the filler metal gap filling rate was ≥99.5%, there were no brittle phases, the volume fraction of γ' phase (Ni3Al / Ni3Ti / Ni3Ta) in the brazed joint was ~40%, and the γ' phase size was ~0.3μm. The brazed joint prepared in this embodiment was tested for mechanical properties using an INSTRON 3382 electronic universal testing machine. The results showed that the shear strength reached 840 MPa; the high-temperature shear strength at 1000℃ reached 495.23 MPa; the creep rupture time at 1000℃ / 100MPa reached 350h; and after cyclic oxidation at 1000℃ for 100h, the oxidation weight gain was ≤5mg / cm³. 2 .

[0034] Example 2 In this embodiment, a nickel-based brazing filler metal with atomic percentages of Co 8.5 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 1.1 at.%, Si 0.9 at.%, La 0.25 at.%, Nd 0.18 at.%, Ta 4.5 at.%, Nb 2.5 at.%, and Ni 60.07 at.% was used to braze the single-crystal superalloy DD10. The specific process is as follows: Step 1: Weigh the powders Co, Mo, W, Cr, Al, Ti, B, Si, La, Nd, Ta, Nb, and Ni in an argon-protected glove box according to the atomic percentages of the constituent elements of the nickel-based solder. Clean the powders with anhydrous ethanol and ultrasonic for 20 minutes to remove oil and oxides adsorbed on the powder surface. After cleaning, place the powders in a vacuum drying oven and keep them at 85°C for 40 minutes. Mix the powders for 2 hours using a double planetary mixer at 300 rpm, achieving a mixing uniformity of 98% and an elemental deviation of ≤0.1 at.%.

[0035] Step 2: Add the mixed powder to a water-cooled copper crucible vacuum induction furnace, and first evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 The pressure is increased to 800℃ and held for 30 minutes; then high-purity argon gas is introduced to 0.12MPa, the temperature is increased to 1500℃, and electromagnetic stirring (stirring power 5kW) is used to hold for 25 minutes to obtain a melt. The melt is stably introduced into a twin-roll mill using a bottom-pouring tundish, with the roll gap precisely controlled at 0.05mm and the roll speed at 2000rpm, to roll it into a foil-shaped brazing filler metal with a thickness of 50μm.

[0036] Step 3: The prepared foil-shaped brazing filler metal is subjected to stress-relief annealing at a temperature of 650℃ for 80 min. After annealing, it is cooled to below 100℃ in the furnace at a rate of 30℃ / h to avoid secondary stress. The foil-shaped brazing filler metal is then ultrasonically cleaned with anhydrous ethanol (200W) for 25 min to remove surface oil. It is then rinsed three times with deionized water. Finally, it is kept in a vacuum drying oven at 75℃ for 25 min to obtain nickel-based brazing filler metal with a surface roughness Ra≤0.2μm.

[0037] Step 4: The DD10 monocrystalline superalloy base material is sequentially polished with 180#, 280#, 400#, 600#, 800#, 1200#, 1600#, and 2000# silicon carbide wet sandpaper, then chemically and mechanically polished with 120nm silicon dioxide polishing slurry. It is then ultrasonically cleaned in anhydrous ethanol for 20 minutes, soaked in dilute hydrochloric acid for 5 minutes, rinsed three times with deionized water, and dried with a high-purity nitrogen gun to obtain the pretreated DD10 monocrystalline superalloy base material. Nickel-based brazing filler metal is placed between the upper and lower layers of the pretreated DD10 monocrystalline superalloy base material and placed under vacuum. Brazing is performed in a vacuum brazing furnace. The specific brazing process is as follows: The process involves four stages: First, heating from room temperature to 350°C at a rate of 8°C / min, applying a pressure of 0.5 MPa, and holding at 350°C for 15 minutes. Second, heating from 350°C to 750°C at a rate of 8°C / min, applying a pressure of 0.8 MPa, and holding at 750°C for 15 minutes. Third, heating from 750°C to 1050°C at a rate of 8°C / min, applying a pressure of 1.0 MPa, and holding at 1050°C for 15 minutes. Fourth, heating from 1050°C to a welding temperature of 1220°C at a rate of 5°C / min, applying a pressure of 1.2 MPa, holding at a welding temperature of 1250°C for 180 minutes, and then cooling to room temperature in the furnace.

[0038] The brazed joints prepared in this embodiment were subjected to mechanical property testing using an INSTRON 3382 electronic universal testing machine. The results showed a shear strength of 823.65 MPa, a high-temperature shear strength of 489 MPa at 1000℃, and a creep rupture time of 370 h at 1000℃ / 100 MPa. After 100 h of cyclic oxidation at 1000℃, the oxidation weight gain was ≤5 mg / cm³. 2 .

[0039] Example 3 In this embodiment, a nickel-based brazing filler metal with atomic percentages of Co 8.5 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 1.1 at.%, Si 0.9 at.%, La 0.25 at.%, Nd 0.18 at.%, Ta 4.5 at.%, Nb 2.5 at.%, and Ni 60.07 at.% was used to braze the single-crystal superalloy DD10. The specific process is as follows: Step 1: According to the atomic percentages of the constituent elements of the above nickel-based solder, weigh the powders Co, Mo, W, Cr, Al, Ti, B, Si, La, Nd, Ta, Nb, and Ni in an argon-protected glove box. Clean the powders with anhydrous ethanol and ultrasonic synergistic cleaning for 20 minutes to remove oil and oxides adsorbed on the powder surface. After cleaning, place the powders in a vacuum drying oven and keep them at 85°C for 40 minutes. Use a double planetary mixer to mix the powders at 300 rpm for 2 hours, achieving a mixing uniformity of 98% and an elemental deviation of ≤0.1 at.%.

[0040] Step 2: Add the mixed powder to a water-cooled copper crucible vacuum induction furnace, and first evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 The pressure is increased to 800℃ and held for 30 minutes; then high-purity argon gas is introduced to 0.12MPa, the temperature is increased to 1500℃, and electromagnetic stirring (stirring power 5kW) is used to hold for 25 minutes to obtain a melt. The melt is stably introduced into a twin-roll mill using a bottom-pouring tundish, with the roll gap precisely controlled at 0.055mm and the roll speed at 2100rpm, to roll it into a foil-shaped brazing filler metal with a thickness of 55μm.

[0041] Step 3: The prepared foil-shaped brazing filler metal is subjected to stress-relief annealing at a temperature of 650℃ for 80 min. After annealing, it is cooled to below 100℃ in the furnace at a rate of 30℃ / h to avoid secondary stress. The foil-shaped brazing filler metal is then ultrasonically cleaned with anhydrous ethanol (200W) for 25 min to remove surface oil. It is then rinsed three times with deionized water. Finally, it is kept in a vacuum drying oven at 75℃ for 25 min to obtain nickel-based brazing filler metal with a surface roughness Ra≤0.2μm.

[0042] Step 4: The DD10 monocrystalline superalloy base material is sequentially polished with 180#, 280#, 400#, 600#, 800#, 1200#, 1600#, and 2000# silicon carbide wet sandpaper, then chemically and mechanically polished with 120nm silicon dioxide polishing slurry. It is then ultrasonically cleaned in anhydrous ethanol for 20 minutes, soaked in dilute hydrochloric acid for 5 minutes, rinsed three times with deionized water, and dried with a high-purity nitrogen gun to obtain the pretreated DD10 monocrystalline superalloy base material. Nickel-based brazing filler metal is placed between the upper and lower layers of the pretreated DD10 monocrystalline superalloy base material and placed under vacuum. Brazing is performed in a vacuum brazing furnace. The specific brazing process is as follows: The process involves four stages: First, heating from room temperature to 350°C at a rate of 8°C / min, applying a pressure of 0.5 MPa, and holding at 350°C for 15 minutes. Second, heating from 350°C to 750°C at a rate of 8°C / min, applying a pressure of 0.8 MPa, and holding at 750°C for 15 minutes. Third, heating from 750°C to 1050°C at a rate of 8°C / min, applying a pressure of 1.0 MPa, and holding at 1050°C for 15 minutes. Fourth, heating from 1050°C to a welding temperature of 1220°C at a rate of 5°C / min, applying a pressure of 1.2 MPa, holding at a welding temperature of 1250°C for 180 minutes, and then cooling to room temperature in the furnace.

[0043] The brazed joints prepared in this embodiment were subjected to mechanical property testing using an INSTRON 3382 electronic universal testing machine. The results showed a shear strength of 820.55 MPa, a high-temperature shear strength of 483.52 MPa at 1000℃, and a creep rupture time of 400 h at 1000℃ / 100 MPa. After 100 h of cyclic oxidation at 1000℃, the oxidative weight gain was ≤5 mg / cm³. 2 .

[0044] Comparative Example 1 In this comparative example, a nickel-based brazing filler metal (traditional BNi-2 brazing filler metal) with an atomic percentage of Cr 8.0 at.%, B 3.5 at.%, Si 4.5 at.%, Fe 2.5 at.%, C 0.1 at.%, and Ni 81.4 at.% was used to braze the single-crystal superalloy DD10. The thickness of the prepared nickel-based brazing filler metal was 45 μm. The remaining steps were the same as in Example 1. The mechanical properties of the brazed joint were tested using an INSTRON 3382 electronic universal testing machine. The shear strength was found to be 691.67 MPa, and the high-temperature shear strength at 1000℃ was 291.81 MPa.

[0045] The composition of this comparative example is close to that of traditional nickel-based brazing filler metal. Compared with Example 1, it contains more B and Si, resulting in more brittle phases in the weld seam of the joint. Compared with Example 1, the mechanical properties of the joint at high temperature are significantly reduced.

[0046] Comparative Example 2 In this comparative example, a nickel-based brazing filler metal with atomic percentages of Co 8.77 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 1.1 at.%, Si 0.9 at.%, La 0.25 at.%, Nd 0.18 at.%, Ta 7.5 at.%, Nb 2.5 at.%, and Ni 56.8 at.% was used to braze a single-crystal superalloy DD10. The prepared nickel-based brazing filler metal was 45 μm thick. The remaining steps were the same as in Example 1. The joint was tested for mechanical properties using an INSTRON 3382 electronic universal testing machine. The shear strength was found to be 770.23 MPa, and the high-temperature shear strength at 1000℃ was 369.23 MPa.

[0047] Compared with Example 1, the content of Ta element in this comparative example exceeds the set range, causing the total atomic percentage of Al, Ti, Ta, and Nb to exceed the control range. As a result, the volume fraction of the γ' phase in the microstructure of the brazed joint increases, and the mechanical properties of the joint decrease significantly.

[0048] Comparative Example 3 In this comparative example, a nickel-based brazing filler metal with atomic percentages of Co 8.5 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 1.1 at.%, Si 0.9 at.%, La 0.25 at.%, Nd 0.18 at.%, Ta 4.5 at.%, Nb 0.3 at.%, and Ni 62.27 at.% was used to braze a single-crystal superalloy DD10. The prepared nickel-based brazing filler metal was 45 μm thick. The remaining steps were the same as in Example 1. The joint was tested for mechanical properties using an INSTRON 3382 electronic universal testing machine. The shear strength was found to be 789 MPa, and the high-temperature shear strength at 1000℃ was 387.59 MPa.

[0049] Compared with Example 1, the content of Nb in this comparative example exceeds the set range, causing the total atomic percentage of Al, Ti, Ta, and Nb to exceed the control range. As a result, the γ' phase in the microstructure of the brazed joint becomes coarser, and the mechanical properties of the joint decrease.

[0050] Comparative Example 4 In this comparative example, a nickel-based brazing filler metal with atomic percentages of Co 8.5 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 1.1 at.%, Si 0.9 at.%, La 0.25 at.%, Ta 4.5 at.%, Nb 2.5 at.%, and Ni 60.25 at.% was used to braze a single-crystal superalloy DD10. The prepared nickel-based brazing filler metal was 45 μm thick. The remaining steps were the same as in Example 1. The joint was tested for mechanical properties using an INSTRON 3382 electronic universal testing machine. The shear strength was found to be 775.62 MPa, and the high-temperature shear strength at 1000℃ was 388.23 MPa.

[0051] Compared with Example 1, this comparative example does not contain rare earth element Nd in the brazing filler metal. The γ' phase and carbides in the microstructure of the brazed joint are coarsened, the dispersion strengthening effect is weakened, and the mechanical properties of the joint decrease.

[0052] Comparative Example 5 In this comparative example, a nickel-based brazing filler metal with atomic percentages of Co 8.5 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 2.01 at.%, Si 0.1%, La 0.25 at.%, Nd 0.18 at.%, Ta 4.4 at.%, Nb 2.5 at.%, and Ni 60.06 at.% was used to braze a single-crystal superalloy DD10. The prepared nickel-based brazing filler metal was 45 μm thick. The remaining steps were the same as in Example 1. The joint was tested for mechanical properties using an INSTRON 3382 electronic universal testing machine. The results showed that the shear strength was only 720.16 MPa, and the high-temperature shear strength at 1000℃ was 346.31 MPa.

[0053] Compared to Example 1, this comparative example has a B content that exceeds the range, resulting in a reduced Si content, but its total atomic percentage still exceeds the set range. The SEM microstructure of the connector is as follows. Figure 2 As shown, the volume fraction of the brittle phase increases significantly, and the shear strength of the joint decreases significantly.

[0054] Comparative Example 6 In this comparative example, a nickel-based brazing filler metal with atomic percentages of Co 8.5 at.%, Mo 2.7 at.%, W 1.8 at.%, Cr 8.5 at.%, Al 5.5 at.%, Ti 3.5 at.%, B 1.1 at.%, Si 0.9 at.%, La 0.25 at.%, Nd 0.18 at.%, Ta 4.5 at.%, Nb 2.5 at.%, and Ni 60.07 at.% was used to braze a single-crystal superalloy DD10. The prepared nickel-based brazing filler metal had a thickness of 45 μm. The remaining steps were the same as in Example 1. The joint was tested for mechanical properties using an INSTRON 3382 electronic universal testing machine. The shear strength was found to be 782.71 MPa, and the high-temperature shear strength at 1000℃ was 390.62 MPa.

[0055] Compared with Example 1, this comparative example does not contain La, which increases impurities at the grain boundaries and reduces the mechanical properties of the joint.

[0056] The embodiments given above are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions or substitutions made by those skilled in the art based on the technical features of the present invention are within the protection scope of the present invention.

Claims

1. A nickel-based brazing filler metal for brazing single-crystal high-temperature alloy DD10, characterized in that, The nickel-based solder consists of the following elements by atomic percentage: Composition: Co 8.5at.%-9.5at.%, Cr 7.5at.%-8.5at.%, Mo 2.2at.%-2.8at.%, W1.2at.%-1.8at.%, Al 4.5at.%-5.5at.%, Ti 2.5at.%-3.5at.%, Ta 3.5at.%-4.5at.%, Nb1.5at.%-2.5at.%, B 0.9at.%-1.1at.%, Si 0.6at.%-0.9at.%, La 0.15at.%-0.25at.%, Nd0.12at.%-0.18at.%, the balance is Ni; The total atomic percentage of Al, Ti, Ta, and Nb is 12 at.%-16 at.%, and the total atomic percentage of B and Si is 1.5 at.%-2.0 at.%.

2. A method for preparing a nickel-based brazing filler metal for brazing a single-crystal high-temperature alloy DD10, characterized in that, The preparation method of the nickel-based solder includes the following steps: Step 1: Weigh Ni, Co, Cr, Al, Ta, Ti, Mo, Nb, W, B, Si, La, and Nd powders according to the atomic percentage of the nickel-based brazing filler metal as described in claim 1. After cleaning and drying, mix them using a double planetary mixer to obtain a mixed powder. Step 2: After preparing the melt from the mixed powder using induction melting, foil-shaped brazing filler metal is prepared using twin-roll casting. Step 3: The foil-shaped brazing filler metal is subjected to stress-relief annealing, followed by ultrasonic cleaning with anhydrous ethanol, deionization rinsing, and drying to obtain the nickel-based brazing filler metal.

3. The method for preparing a nickel-based brazing filler metal for brazing single-crystal high-temperature alloy DD10 according to claim 2, characterized in that, The cleaning process described in step one involves ultrasonic cleaning with anhydrous ethanol for 20 minutes, and the drying process involves drying in a vacuum drying oven at a temperature of 85°C for 40 minutes.

4. The method for preparing a nickel-based brazing filler metal for brazing single-crystal high-temperature alloy DD10 according to claim 2, characterized in that, In the process of preparing foil-shaped brazing filler metal by twin-roll casting and rolling in step two, the melt is introduced into a twin-roll mill using a bottom-pouring tundish. The roll gap of the twin-roll mill is 0.045 mm-0.055 mm, and the roll speed is 1900 rpm-2100 rpm, and the foil-shaped brazing filler metal is obtained by rolling.

5. The method for preparing a nickel-based brazing filler metal for brazing single-crystal high-temperature alloy DD10 according to claim 4, characterized in that, The thickness of the foil-shaped solder is 45 μm-55 μm.

6. The method for preparing a nickel-based brazing filler metal for brazing single-crystal high-temperature alloy DD10 according to claim 2, characterized in that, The stress-relief annealing in step three is performed at a temperature of 650℃ for 80 min, followed by furnace cooling at a rate of 25℃ / h-30℃ / h.

7. A brazing method for a single-crystal high-temperature alloy DD10, characterized in that, The nickel-based brazing filler metal described in claim 1 is placed between two pretreated monocrystalline high-temperature alloy DD10 base materials, and then placed together in a vacuum brazing furnace for brazing to obtain a monocrystalline high-temperature alloy DD10 brazed joint.

8. The brazing method for a single-crystal high-temperature alloy DD10 according to claim 7, characterized in that, The brazing process employs a gradient heating and pressurization method, specifically as follows: First, heating from room temperature to 350°C at a rate of 8°C / min, applying a pressure of 0.5 MPa, and holding at 350°C for 15 minutes; Second, heating from 350°C to 750°C at a rate of 8°C / min, applying a pressure of 0.8 MPa, and holding at 750°C for 15 minutes; Third, heating from 750°C to 1050°C at a rate of 8°C / min, applying a pressure of 1.0 MPa, and holding at 1050°C for 15 minutes; Fourth, heating from 1050°C to a welding temperature of 1220°C at a rate of 5°C / min, applying a pressure of 1.2 MPa, and holding at a welding temperature of 1250°C for 180 minutes, followed by furnace cooling to room temperature; the vacuum degree of the vacuum brazing furnace... .

9. The brazing method for a single-crystal high-temperature alloy DD10 according to claim 7, characterized in that, The brazed joint of the single-crystal high-temperature alloy DD10 has a γ' phase volume fraction of 40%-45% and a γ' phase size of 0.2μm-0.5μm.

10. The brazing method for a single-crystal high-temperature alloy DD10 according to claim 7, characterized in that, The single-crystal high-temperature alloy DD10 brazed joint has a creep rupture time of 350h-400h under the conditions of 1000℃ and 100MPa; and a shear strength of 480MPa-500MPa at 1000℃.

Images