A method for TLP bonding of high-temperature alloy with interlayer added high-entropy alloy nanoparticles

Abstract

The application discloses an intermediate layer added high-entropy alloy nanoparticle assisted high-temperature alloy TLP connecting method and relates to the technical field of welding. The method comprises the following steps: preparing high-entropy alloy nanoparticles; mixing the high-entropy alloy nanoparticles with a powder intermediate layer to obtain a composite intermediate layer; under vacuum conditions, welding high-temperature alloy to be welded based on a TLP welding method by using the composite intermediate layer to obtain a welded piece. By reasonably selecting the high-chemical-mixing-entropy filling material, the elements of the intermediate layer and the high-alloyed base material are fully interacted, the types and contents of the chemical composition of the welding area are greatly improved, the chemical mixing entropy of the corresponding area is also increased, and each area of the joint is in a high-entropy state. The addition of the nanoparticles can inhibit and delay the growth of intermetallic compounds / eutectic phases, reduce the crystal nucleus size, and effectively improve the mechanical properties of the diffusion welded joint, in particular the plasticity and toughness.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and in particular to a high-temperature alloy TLP connection method assisted by adding high-entropy alloy nanoparticles to an intermediate layer. Background Art

[0002] With the advancement of aviation technology, the service requirements for aircraft engines are constantly increasing. The next generation of engines needs to develop high thrust and a high thrust-to-weight ratio. Superalloys, with their excellent high-temperature strength, oxidation resistance, and thermal corrosion resistance, have become an indispensable key material in the manufacture of core aircraft engine components. Superalloys often contain high-melting-point elements, making them prone to thermal cracking during welding, which can lead to degraded joint performance. However, TLP diffusion welding, due to its unique characteristics, has become one of the most promising welding methods for joining superalloys.

[0003] The TLP joining technique for high-temperature alloys typically uses a nickel-based alloy containing a melting-depressant element as an intermediate layer (melting at the welding temperature). As the melting-depressant element diffuses into the base metal, the liquidus temperature of the intermediate layer rises, leading to isothermal solidification and formation of the joint. However, the characteristics of TLP joining make it highly susceptible to the formation of brittle phases such as borides and low-melting-point eutectics within the high-temperature alloy joint. These phases, under harsh service conditions such as high temperatures and dynamic loads, create weak links that facilitate crack nucleation and propagation, resulting in insufficient overall mechanical properties. Controlling the precipitation of brittle phases to achieve a uniform microstructure with a balanced strength and toughness, thereby improving the joint's overall mechanical properties, has become a key technical bottleneck that urgently needs to be overcome in TLP joining technology. Summary of the Invention

[0004] The present invention aims at the deficiencies existing in the above-mentioned background technologies, and mainly solves the problem of insufficient comprehensive mechanical properties of joints caused by brittle phases such as borides and low-melting-point eutectic structures existing in TLP connections of high-temperature alloy materials. The present invention provides a method for TLP connection of high-temperature alloys assisted by adding high-entropy alloy nanoparticles to an intermediate layer. This method introduces high chemical mixing entropy filler materials by reasonable selection, so that the elements of the intermediate layer and the high-alloyed base material fully interact with each other, thereby greatly improving the types and contents of the chemical components in the welding area. Correspondingly, the chemical mixing entropy of each region is also increased at the same time, and each region of the joint is in a high-entropy state. At the same time, the nanoparticles will inhibit and delay the precipitation and growth of intermetallic compounds / eutectic phases, thereby improving the microstructure of the joint, thereby improving the mechanical properties of the diffusion welding joint, and especially having an effective effect on improving strength and toughness.

[0005] The first object of the present invention is to provide a method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer, comprising the following steps:

[0006] Preparation of high entropy alloy nanoparticles;

[0007] Adding high entropy alloy nanoparticles to the powder middle layer and mixing thoroughly in a ball mill to obtain a composite middle layer;

[0008] Under vacuum conditions, the high-temperature alloy to be welded is welded using a composite intermediate layer based on a TLP connection method to obtain a welded part.

[0009] Preferably, the high entropy alloy nanoparticles are produced by an arc discharge method or a laser pulse method.

[0010] Preferably, the high entropy alloy nanoparticles are prepared by an arc discharge method, comprising:

[0011] Design the composition of high entropy alloys;

[0012] Weigh the raw materials according to the composition of the high entropy alloy, mix them and press them into a target material;

[0013] The target material is used as an anode and a carbon rod is used as a cathode;

[0014] The anode and cathode are placed in a vacuum reaction chamber, filled with reaction gas, arc reaction parameters are set, and arc discharge is performed to produce high entropy alloy nanoparticles.

[0015] Preferably, the laser pulse method is used to prepare high entropy alloy nanoparticles, comprising:

[0016] Design the composition of high entropy alloys;

[0017] Weighing raw materials according to the composition of the high entropy alloy to prepare a solid high entropy alloy target;

[0018] Choose liquid or gas phase environment;

[0019] Set pulse laser parameters;

[0020] Laser is used to hit the surface of the target material, triggering a high-temperature and high-pressure plasma plume. The various metal elements in the plume are condensed into high-entropy alloy nanoparticles through rapid cooling.

[0021] Preferably, in the liquid phase, the nanoparticles are dispersed in the liquid phase by an electrostatic stabilization mechanism, and the nanoparticles will adhere to the surface of the carrier.

[0022] Preferably, the composition design of the high entropy alloy is carried out according to the base material to be welded, and the composition design is based on the Ω phase formation criterion, the δ phase stability criterion, and the VEC plasticity criterion;

[0023] The criterion for the formation of Ω phase is as follows:

[0024]

[0025]

[0026]

[0027] Where, 、 They are i and j Atomic concentration of elements; is the gas constant; ∆ represents the mixing entropy of elements;

[0028] The δ phase stability criterion is as follows:

[0029]

[0030]

[0031] Where, is the atomic radius; is the average atomic radius difference;

[0032] The VEC plasticity criterion is as follows:

[0033]

[0034] Where, For the i The valence electron concentration of the element.

[0035] Preferably, the TLP connection is performed under high vacuum.

[0036] The second object of the present invention is to provide a welded part produced by the above method.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention provides a method for TLP connection of high-temperature alloys assisted by adding high-entropy alloy nanoparticles to the intermediate layer. The method increases the mixed entropy value of the weld based on the high entropy effect and changes the thermodynamic conditions for the formation of eutectic structure. The present invention has better solid solubility than traditional alloys and helps to inhibit the diffusion of melting-reducing elements into the nickel-based high-temperature alloy parent material to form high-density borides. The joint prepared by the connection method provided by the present invention has high strength and toughness characteristics, and at the same time forms a strongly bonded coherent interface with the metal, which helps to activate the synergistic effect between various strengthening and toughening mechanisms including solid solution strengthening, fine grain strengthening (toughening) and dispersion strengthening.

[0039] Under the effects of high entropy, delayed diffusion, lattice distortion, etc., high-strength and high-toughness high-temperature alloy joints can be obtained. (1) The high entropy effect increases the mixed entropy value of the weld; (2) The solid solubility is superior to that of traditional alloys, which helps to inhibit the diffusion of melting elements into the nickel-based high-temperature alloy parent material to form high-density borides; (3) It has high strength and toughness characteristics, and at the same time forms a strong coherent interface with the metal, which helps to activate the synergistic effect of various strengthening and toughening mechanisms including solid solution strengthening, fine grain strengthening (toughening) and dispersion strengthening.

[0040] High entropy alloy nanoparticles have great potential as the doping phase of the intermediate layer to achieve the goal of regulating the joint structure and improving the strength and toughness of the joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of TLP connection sample loading of high-temperature alloy / composite intermediate layer / high-temperature alloy. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0043] The purpose of the present invention is to solve the brittle phases such as boride and low melting point eutectic structure existing in TLP connection of high temperature alloy materials, thereby providing a welding method to improve the mechanical properties of the joint.

[0044] To achieve the above objectives, the present invention provides a first aspect of a method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer, comprising the following steps:

[0045] Preparation of high entropy alloy nanoparticles;

[0046] Adding high entropy alloy nanoparticles to the powder intermediate layer, mixing them thoroughly with a ball mill to obtain a composite intermediate layer, adding terpineol, and preparing the composite intermediate layer into a paste;

[0047] Under vacuum conditions, the high-temperature alloy to be welded is welded using a composite intermediate layer based on a TLP method to obtain a welded part.

[0048] During welding, TLP connection is performed under high vacuum.

[0049] Wherein, the high entropy alloy nanoparticles are prepared by arc discharge method or laser pulse method.

[0050] Specifically, the arc discharge method is used to prepare high entropy alloy nanoparticles, including:

[0051] Design the composition of high entropy alloys;

[0052] Weigh the raw materials according to the composition of the high entropy alloy, mix them and press them into a target material;

[0053] The target material is used as an anode and a carbon rod is used as a cathode;

[0054] The anode and cathode are placed in a vacuum reaction chamber, filled with reaction gas, arc reaction parameters are set, and arc discharge is performed to produce high entropy alloy nanoparticles.

[0055] In one embodiment, the arc discharge method is a preparation method for converting metal into nanoparticles using high-temperature plasma. The specific steps are as follows:

[0056] (1) The target metal powders are mixed and pressed into a cylindrical target with a diameter of about 45 μm. The target is used as the anode, and a carbon rod is used as the cathode.

[0057] (2) Place the electrode in a vacuum reaction chamber and control the vacuum degree to about 10 -3 Pa, the reaction gas (such as methane) is filled in and the pressure is adjusted to 0.2 × 10 5 Pa;

[0058] (3) The arc reaction voltage is set to 3 V and the current is 230 A. The arc discharge lasts for 5-10 minutes, generating a high plasma temperature (over 3000 K);

[0059] (4) Collect the cooled particles.

[0060] Specifically, the pulsed laser method is used to prepare high entropy alloy nanoparticles, including:

[0061] Design the composition of high entropy alloys;

[0062] Weighing raw materials according to the composition of the high entropy alloy to prepare a solid high entropy alloy target;

[0063] Choose liquid or gas phase environment;

[0064] Set pulse laser parameters;

[0065] Laser is used to hit the surface of the target material, triggering a high-temperature and high-pressure plasma plume. The various metal elements in the plume are condensed into high-entropy alloy nanoparticles through rapid cooling.

[0066] Among them, in the liquid phase, nanoparticles are dispersed in the liquid phase through an electrostatic stabilization mechanism, and the nanoparticles will adhere to the surface of the carrier.

[0067] In one embodiment, the pulsed laser method uses a high-energy laser beam to evaporate metal in a liquid or gas phase to form nanoparticles. The specific steps are as follows:

[0068] (1) Preparing multiple metals into solid targets in a certain proportion;

[0069] (2) Select a liquid phase (such as ethanol, n-hexane) or gas phase (such as air or argon) according to the experimental requirements. If it is a liquid phase, the target needs to be immersed in a liquid (such as n-hexane or deionized water);

[0070] (3) Using nanosecond pulse laser, set the wavelength, pulse width, repetition rate and high power density; for example, for Nd:YAG laser, set the wavelength to 1064 nm, pulse width to 5 ns, repetition rate to 2 Hz and high power density to 2 × 10 9 W / cm 2 .

[0071] (4) The laser strikes the target surface, triggering a high-temperature and high-pressure plasma plume. The various metal elements in the plume condense into alloy nanoparticles through rapid cooling (nanosecond level);

[0072] (5) In the liquid phase, nanoparticles are dispersed in the solution through an electrostatic stabilization mechanism; if carbon materials (such as graphene or CNFs) are used as carriers, the particles will adhere to their surface.

[0073] In one embodiment, the prepared nanoparticles are characterized primarily by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to analyze particle size, morphology, and elemental distribution to ensure high uniformity and the absence of phase separation. The melting point is estimated using JMatPro software and combined with differential scanning calorimetry (DSC) to verify the melting point. The results are used as feedback to optimize the high-entropy alloy composition design.

[0074] According to the present invention, the composition design of the high entropy alloy is carried out according to the base material to be welded, and the composition design is based on the Ω phase formation criterion, the δ phase stability criterion, and the VEC plasticity criterion;

[0075] The criterion for the formation of Ω phase is as follows:

[0076]

[0077]

[0078]

[0079] Where, 、 They are i and j Atomic concentration of elements; is the gas constant; ∆ represents the mixing entropy of elements;

[0080] The δ phase stability criterion is as follows:

[0081]

[0082]

[0083] Where, is the atomic radius; is the average atomic radius difference;

[0084] The VEC plasticity criterion is as follows:

[0085]

[0086] Where, For the i The valence electron concentration of the element.

[0087] The method provided by the invention performs TLP connection under high vacuum degree.

[0088] A second aspect of the present invention provides a welded part.

[0089] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0090] Example

[0091] A high-strength and high-toughness diffusion welding method for powder high-temperature alloy FGH99 based on adding high-entropy alloy nanoparticles to the intermediate layer comprises the following steps:

[0092] 1. Use FGH99 as the base material and cut the base material into 10×5×2 mm pieces using a wire cutting machine before welding. 3 and 5×5×5 mm 3 Before welding, the base material needs to be gradually ground to 2000# SIC sandpaper, and then polished to ensure the flatness and smoothness of the welding surface;

[0093] BNi-2 is the most widely studied and applied nickel-based alloy in standard commercial interlayers. It also contains the key elements of the FGH99 superalloy and operates within the weldability window of the parent metal (1010-1177°C). It exhibits excellent wettability to nickel-based superalloys, resulting in joints with good high-temperature strength and oxidation resistance. To avoid the lack of toughness associated with conventional welding methods, the CoCrFeNiMo system was selected. This system contains the key elements of both BNi-2 and the FGH99 superalloy parent metals, and the alloying element content is ≥5, meeting the basic requirements for forming a high-entropy alloy.

[0094] The alloy system was chosen as the filler metal based on the Ω phase formation criterion, δ phase stability criterion, and VEC plasticity criterion mentioned in the above formula. The high-entropy alloy nanoparticles were prepared using the arc discharge method. The prepared high-entropy alloy nanoparticles and the BNi-2 powder matrix to be mixed were mixed in a QM-3SP4 planetary high-energy ball mill (1.5kW, maximum speed 530rpm), and then terpineol was added to form a paste-like intermediate layer.

[0095] 3. When the vacuum degree is 3.3×10 -3 Pa and a temperature of 1100 °C, TLP bonding was performed for 30 min, 60 min, 90 min, and 120 min, and then the sample was cooled to room temperature in the furnace to complete the welding process;

[0096] After TLP bonding, the cross-section of the joint was polished and chemically etched in a solution of 10 mL HNO₃ + 10 mL C₂H₄O₂ + 15 mL HCl for 5–6 s. The microstructure and crystallographic features of the joint were characterized using a field-emission scanning electron microscope (ZEISS Gemini 500), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). Details of the reaction phase in the TLP joint were identified using a field-emission transmission electron microscope (FEI-TEM, Talos F200 X).

[0097] In this example, the TLP joining method for FGH99, which introduces CoCrFeNiMo high-entropy alloy nanoparticles into BNi-2, eliminates the eutectic phase in the joint at 1100°C for 30 minutes, demonstrating that the high-entropy alloy effectively suppresses the formation of eutectic structure in the joint. Furthermore, as the high-entropy alloy nanoparticle content increases within a certain range, the volume fraction and size of the boride in the joint region decrease. This indicates that the addition of high-entropy alloy nanoparticles effectively suppresses the formation of boride and eutectic structure in the joint.

[0098] See also Figure 1 As shown in the figure, it is a schematic diagram of high temperature alloy sample loading.

[0099] Figure 1 Schematic diagram of the sample loading for adding high-entropy alloy nanoparticles to assist in TLP connection of high-temperature alloys. Before loading, the surface to be welded needs to undergo a series of grinding and polishing work to ensure its flatness. For the composite intermediate layer, the prepared high-entropy alloy nanoparticles and the intermediate layer matrix must first be thoroughly mixed using a ball mill, and then pine oil is used to prepare a corresponding paste-like composite intermediate layer to facilitate the clamping of the welded parts.

[0100] In summary, the present invention provides a method for transient liquid phase diffusion (TLP) joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer. The method comprises preparing high-entropy alloy nanoparticles; thoroughly mixing the high-entropy alloy nanoparticles with a powder intermediate layer in a ball mill to obtain a composite intermediate layer; and welding the high-temperature alloy to be welded using the composite intermediate layer formed by introducing high-entropy alloy nanoparticles into the intermediate layer under vacuum conditions using the TLP joining method to obtain a welded joint. The present invention introduces a high chemical mixing entropy filler material through the rational selection of elements in the intermediate layer to fully interact with the elements of the high-alloyed base material, thereby greatly increasing the types and contents of the chemical components in the weld zone. Accordingly, the chemical mixing entropy of each region is also increased, and each region of the joint is in a high-entropy state. Furthermore, the addition of nanoparticles can inhibit and delay the growth of intermetallic compounds / eutectic phases. Its mechanism of action is the adsorption effect of nanoparticles: nanoparticles are adsorbed onto the intermetallic compounds or eutectic phase nuclei appearing in the metal liquid phase, acting as a barrier medium to hinder element diffusion or interfacial reaction, thereby reducing the nucleation rate and the size of the nucleus, which has an effective effect on improving the mechanical properties of diffusion welding joints, especially plasticity and toughness.

[0101] The above embodiments are merely some examples for facilitating understanding of the synthesis and application methods of the materials of the present invention and are not intended to limit the present invention. It is understood that relevant practitioners can easily make appropriate modifications to the above structures. Therefore, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer, characterized in that: The following steps are involved: Preparation of high entropy alloy nanoparticles; The high entropy alloy nanoparticles and the powder intermediate layer are fully mixed in a ball mill to obtain a composite intermediate layer, which is then prepared into a paste-like intermediate layer by adding terpineol. Under vacuum conditions, the high-temperature alloy to be welded is welded using a composite intermediate layer based on a transient liquid phase diffusion welding method (TLP) to obtain a welded connection; FGH99 is used as the base material; The powder middle layer is a BNi-2 powder matrix; The high entropy alloy nanoparticles are CoCrFeNiMo; The melting point of high-entropy alloy nanoparticles was estimated using JMatPro software and combined with differential scanning calorimetry to verify the melting point. The composition design of the high-entropy alloy was optimized based on the feedback from the results. The composition design of the high entropy alloy is carried out according to the base material to be welded, and the composition design is based on the Ω phase formation criterion, the δ phase stability criterion, and the VEC plasticity criterion; The criterion for the formation of Ω phase is as follows: Where, 、 They are i and j Atomic concentration of elements; is the gas constant; ∆ represents the mixing entropy of elements; The δ phase stability criterion is as follows: Where, is the atomic radius; is the average atomic radius difference; The VEC plasticity criterion is as follows: Where, For the i The valence electron concentration of the element.

2. The method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer according to claim 1, characterized in that: The high entropy alloy nanoparticles are prepared by adopting an arc discharge method or a laser pulse method.

3. The method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer according to claim 2, characterized in that: The arc discharge method is used to prepare high entropy alloy nanoparticles, including: Design the composition of high entropy alloys; Weigh the raw materials according to the composition of the high entropy alloy, mix them and press them into a target material; The target material is used as an anode and a carbon rod is used as a cathode; The anode and cathode are placed in a vacuum reaction chamber, filled with reaction gas, arc reaction parameters are set, and arc discharge is performed to produce high entropy alloy nanoparticles.

4. The method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer according to claim 2, characterized in that: The laser pulse method is used to prepare high entropy alloy nanoparticles, including: Design the composition of high entropy alloys; Weighing raw materials according to the composition of the high entropy alloy to prepare a solid high entropy alloy target; Choose liquid or gas phase environment; Set pulse laser parameters; Laser is used to hit the surface of the target material, triggering a high-temperature and high-pressure plasma plume. The various metal elements in the plume are condensed into high-entropy alloy nanoparticles through rapid cooling.

5. The method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer according to claim 4, characterized in that: In the liquid phase, the nanoparticles are dispersed in the liquid phase through an electrostatic stabilization mechanism, and the nanoparticles will adhere to the surface of the carrier.

6. The method for TLP joining of high-temperature alloys by adding high-entropy alloy nanoparticles to an intermediate layer according to claim 1, characterized in that: The TLP connection was performed under high vacuum.

7. A connector made by the method according to any one of claims 1 to 6.

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