High-entropy alloy interlayer for transient liquid phase diffusion bonding of GH5188 and its bonding method

Abstract

The high-entropy alloy interlayer for transient liquid-phase diffusion bonding of GH5188 and its bonding method provided by the present invention relate to the technical field of metal welding. The constituent elements of the high-entropy alloy interlayer provided by the present invention are composed of elements with the following atomic ratios: Co:Ni:Cr:Al:Ta:Ge:Zr:Y = 25:20:20:15:10:5:3:2, and the element purity is greater than 99.99 wt.%. The present invention also provides a bonding method for transient liquid-phase diffusion bonding of GH5188. The high-entropy alloy interlayer is placed in the middle of the base material GH5188 and welded in a vacuum diffusion welding furnace. Compared with conventional transient liquid-phase diffusion bonding, it can inhibit the formation of brittle compounds and is beneficial to the improvement of the comprehensive interface performance.

Description

Technical Field

[0001] The present invention relates to the technical field of metal welding, and particularly relates to a high-entropy alloy interlayer for transient liquid-phase diffusion bonding of GH5188 and a bonding method thereof. Background Art

[0002] With the evolution of aero-engine power systems towards high thrust and high thrust-to-weight ratio, material properties have become the core factor restricting the breakthrough of engine technology. GH5188 (Co-Ni-Cr-based solid-solution strengthened wrought superalloy) occupies an irreplaceable core position in the manufacturing of hot-end components of aero-engines due to its excellent high-temperature creep resistance, creep rupture strength, and oxidation and corrosion resistance.

[0003] However, hot cracks are prone to occur during the fusion welding process of superalloys, and problems such as lack of fusion and pores are prone to occur in direct diffusion welding. Conventional interlayers for transient liquid-phase diffusion bonding often introduce traditional melting-point-depressing elements, resulting in brittle phases in the joints, which causes a decrease in the strength and hardness of the joints. Therefore, designing a new type of interlayer to assist in the transient liquid-phase diffusion bonding of GH5188 has become a key issue. Summary of the Invention

[0004] Aiming at the deficiencies in the background art, the present invention mainly solves the problem of insufficient mechanical properties of the joint caused by the brittle phase in the joint during the conventional transient liquid-phase diffusion bonding process of GH5188.

[0005] In the first aspect of the present invention, a high-entropy alloy interlayer for transient liquid-phase diffusion bonding of GH5188 is provided. The constituent elements of the high-entropy alloy interlayer are composed of elements with the following atomic ratios: Co:Ni:Cr:Al:Ta:Ge:Zr:Y = 25:20:20:15:10:5:3:2, and the element purity is greater than 99.99 wt.%.

[0006] In the second aspect of the present invention, a preparation method of a high-entropy alloy interlayer for transient liquid-phase diffusion bonding of GH5188 is provided. The preparation method of the high-entropy alloy interlayer includes the following steps:

[0007] Step 1: Weigh pure metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, and Y according to the atomic ratios of the constituent elements of the high-entropy alloy interlayer described above, and clean them;

[0008] Step 2: Prepare an alloy ingot from the pure metal element particles weighed in Step 1 by arc melting;

[0009] Step 3: Perform multi-pass cold rolling on the alloy ingot prepared in Step 2 to obtain cold-rolled thin sheets. Segmentally cut the cold-rolled thin sheets and grind the upper and lower surfaces to obtain the target interlayer. Then, after polishing, etching, cleaning, and drying, the high-entropy alloy interlayer is obtained.

[0010] Preferably, in the cleaning process in Step 1, the weighed pure metal element particles are cleaned on the surface with absolute ethanol and then placed in a drying oven and dried for 1 h.

[0011] Preferably, in the process of preparing the alloy ingot by the arc melting method in Step 2, according to the melting points of the pure metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, and Y in Step 1, they are placed in a copper crucible in ascending order from low to high; the arc melting method is adopted, and the forward and reverse melting is carried out more than 5 times, and electromagnetic stirring is applied to obtain the alloy ingot.

[0012] Preferably, before the multi-pass cold rolling in Step 3, cutting and flattening treatment is carried out. The process is to cut the alloy ingot into regular cuboids, and a grinding machine is used to flatten the cutting surface so that the flatness error of the reference plane of the cutting surface ≤ 0.05 mm.

[0013] Preferably, the multi-pass cold rolling in Step 3 adopts multi-pass reciprocating rolling, the reduction per pass is 0.2 mm - 0.4 mm, the thickness of the cold-rolled sheet is 0.1 mm - 0.2 mm, the grinding is carried out by a double-sided nanoscale grinding machine for mirror grinding, the thickness of the target intermediate layer is 50 μm - 80 μm, and the thickness error is ±5 μm.

[0014] Preferably, the polishing in Step 3 is carried out by mechanical polishing with a diamond suspension with a particle size of 0.25 μm; the corrosion is carried out by using Keller reagent to remove the surface oxide layer, the cleaning is carried out by ultrasonic cleaning with absolute ethanol, and the drying is carried out by purging and drying with high-purity nitrogen.

[0015] The third aspect of the present invention provides a connection method for transient liquid phase diffusion connection of GH5188. The connection method is to place the above-mentioned high-entropy alloy intermediate layer or the high-entropy alloy intermediate layer prepared by the above-mentioned preparation method between the upper and lower base materials GH5188, and then the whole is placed in a vacuum diffusion welding furnace for welding.

[0016] Preferably, the welding adopts a segmented heating and pressurizing method. The specific welding process is as follows: in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 300 °C at a rate of 10 °C / min and kept warm for 10 min; in the second stage, it is heated from 300 °C to 700 °C at a rate of 10 °C / min and kept warm for 10 min; in the third stage, it is heated from 700 °C to 900 °C at a rate of 10 °C / min and kept warm for 10 min; in the fourth stage, it is heated from 900 °C to the welding temperature of 1150 °C at a rate of 10 °C / min; in the fifth stage, it is kept warm at the welding temperature of 1150 °C for 1 h, and a pressure of 5 MPa is applied, and then it is cooled to room temperature with the furnace; the vacuum degree of the vacuum diffusion welding furnace ≤ 4×10 -3 Pa.

[0017] Preferably, before welding in a vacuum diffusion welding furnace, the base material GH5188 is ground and polished using sandpaper and polishing fluid; after the grinding and polishing treatment, the base material GH5188 is ultrasonically cleaned in absolute ethanol.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] For the high-entropy alloy interlayer used for the transient liquid-phase diffusion bonding of GH5188 proposed by the present invention, Ta element in its constituent elements replaces the W element existing in the traditional high-entropy alloy. While optimizing the interfacial concentration gradient during welding, it inhibits grain coarsening at high temperatures and improves the mechanical properties of the joint; Ge replaces the traditional melting-point-lowering elements B and Si to avoid the formation of brittle phases such as borides and silicides; Zr element is used to refine grains and improve the mechanical properties of the joint; Y and Al act synergistically to improve the antioxidant ability.

[0020] The connection method of the high-entropy alloy interlayer proposed by the present invention for the transient liquid-phase diffusion bonding of GH5188, compared with the traditional transient liquid-phase diffusion bonding of GH5188, under the combined action of mechanisms such as high-entropy effect, kinetic retardation diffusion, and solid-solution strengthening, improves the antioxidant ability of the joint, inhibits the precipitation of brittle phases, and improves the mechanical properties of the joint. Description of the Drawings

[0021] Figure 1 is the interfacial microstructure diagram of the transient liquid-phase diffusion bonding of GH5188 using the high-entropy alloy interlayer provided by the present invention.

[0022] Figure 2 is the interfacial microstructure diagram of the transient liquid-phase diffusion bonding of GH5188 using the traditional interlayer.

[0023] Figure 3 is the SEM diagram of the fracture morphology of the transient liquid-phase diffusion bonding of GH5188 using the high-entropy alloy interlayer provided by the present invention.

[0024] Figure 4 is the SEM diagram of the fracture morphology of the transient liquid-phase diffusion bonding of GH5188 using the traditional interlayer. Detailed Embodiments

[0025] In order to make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of the present disclosure without creative efforts shall also fall within the scope of protection of the present disclosure.

[0026] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Further will be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal form unless expressly defined otherwise herein.

[0027] Reference herein to "embodiments" means that a particular feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of the present application. The phrase "embodiments" appearing in various places in the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0028] A high-entropy alloy interlayer for transient liquid-phase diffusion bonding of GH5188 provided by the present invention, the constituent elements of the high-entropy alloy interlayer are composed of elements with the following atomic ratios: Co:Ni:Cr:Al:Ta:Ge:Zr:Y = 25:20:20:15:10:5:3:2, wherein the element purity requirement is greater than 99.99 wt.%, and the pure metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, Y are stored in vacuum.

[0029] The preparation method of the above-mentioned high-entropy alloy interlayer is as follows:

[0030] Step 1: Weigh pure metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, Y according to the atomic ratios of the constituent elements of the above-mentioned high-entropy alloy interlayer, clean the surface with anhydrous ethanol, and place them in a drying oven for drying for 1 h;

[0031] Step 2: Prepare alloy ingots from the pure metal element particles weighed in Step 1 by arc melting method; according to the melting points of the pure metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, Y in Step 1, place them in a copper crucible in ascending order from low to high; place the low-melting-point substances at the bottom of the crucible and the high-melting-point substances at the top, and use the arc melting method to melt forward and backward more than 5 times, and apply electromagnetic stirring to obtain the alloy ingots;

[0032] During the melting process by arc melting method, the conventional weight for single melting is 50 g - 120 g. If the weight is too large, it needs to be melted in batches multiple times, and the multiple alloy ingots after melting are fused to ensure sufficient fusion of the metal particles;

[0033] Step 3: Prepare the high-entropy alloy intermediate layer; Cut the alloy ingot into regular cuboid specimens (25 mm × 25 mm × 5 mm), use a grinding machine to level the cutting surface, eliminate the surface texture generated by wire cutting, and ensure that the reference flatness error ≤ 0.05 mm; Pretreat the rolling mill, and evenly coat the surface of the work roll with a special lubricant for high-viscosity cold rolling; During the multi-pass cold rolling process, the reduction per pass is controlled at 0.2 mm - 0.4 mm; After each pass of rolling, use a laser thickness gauge to detect the thickness deviation, and gradually reduce the material to the target thickness (0.1 mm - 0.2 mm) through multi-pass reciprocating rolling; Use a precision shearing machine to cut the cold-rolled sheet to the target size, and perform mirror grinding with a double-sided nanometer-level grinding machine, and finally control the thickness error within ±5 μm (target thickness 50 μm - 80 μm); Use diamond suspension (particle size 0.25 μm) for mechanical polishing to reduce the surface roughness; First, use Keller reagent (2% HF + 3% HNO3 + 95% H2O) to corrode and remove the surface oxide layer, then place it in absolute ethanol and ultrasonically clean for 10 minutes, and finally blow-dry with high-purity nitrogen to obtain the high-entropy alloy intermediate layer;

[0034] If the prepared high-entropy alloy intermediate layer needs to be stored, after grinding and polishing, seal the surface film and store it in a drying dish, and repeat the above corrosion and cleaning steps before subsequent use.

[0035] In some embodiments of the present invention, the method for preparing the high-entropy alloy intermediate layer is not limited to the above preparation method, and other existing preparation methods can also be used to obtain the high-entropy alloy intermediate layer.

[0036] The present invention also provides a connection method for GH5188 transient liquid-phase diffusion bonding. Place the above high-entropy alloy intermediate layer in the middle of the base material GH5188, and complete the joint welding using a vacuum diffusion welding furnace.

[0037] Before welding in the vacuum diffusion welding furnace, perform grinding and polishing on the base material GH5188 successively with sandpapers of 240#, 400#, 800#, 1000#, 1500#, 2000# and polishing liquid (SiO2:H2O2 = 8:2); After the grinding and polishing work is completed, place the base material GH5188 in absolute ethanol and ultrasonically clean it;

[0038] The welding process is carried out in a vacuum diffusion welding furnace, and the segmented heating and pressurization method is adopted for welding. The specific process is as follows: In the first stage, the vacuum diffusion welding furnace is heated from room temperature to 300 °C at a rate of 10 °C / min and kept warm for 10 min. In the second stage, it is heated to 700 °C at a rate of 10 °C / min and kept warm for 10 min. In the third stage, it is heated to 900 °C at a rate of 10 °C / min and kept warm for 10 min. In the fourth stage, it is heated to the welding temperature of 1150 °C at a rate of 10 °C / min. In the fifth stage, it is kept warm at the welding temperature of 1150 °C for 1 h, and a pressure of 5 MPa is applied. Subsequently, the sample is cooled to room temperature with the furnace, and the welding is completed; during the whole welding process, the vacuum degree of the vacuum diffusion welding furnace is always ≤ 4×10 -3 Pa.

[0039] The present invention will be further described below through specific embodiments.

[0040] Example 1

[0041] In this example, Co 25 Ni 20 Cr 20 Al 15 Ta 10 Ge5Zr3Y2 is used as the intermediate layer for the transient liquid phase diffusion bonding of GH5188. The specific steps are as follows:

[0042] Step 1, prepare the alloy ingot: Weigh the metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, Y using a precision electronic balance. The atomic ratio of the elements Co:Ni:Cr:Al:Ta:Ge:Zr:Y = 25:20:20:15:10:5:3:2, and the element purity is greater than 99.9 wt.%. Wash the surface of the weighed metal element particles with absolute ethanol and place them in a drying oven for drying for 1 h. Place the metal element particles in a copper crucible according to the melting points of Co, Ni, Cr, W, Fe, B, Si. The low melting point substances are placed at the bottom of the crucible, and the high melting point substances are placed on the top; melt at least 5 times in both positive and negative directions and apply electromagnetic stirring to ensure full fusion of the metal particles;

[0043] Step 2: Prepare the high-entropy alloy intermediate layer. Cut the alloy ingot into regular cuboid specimens (25 mm × 25 mm × 5 mm), use a grinding machine to level the cutting surface, eliminate the surface texture generated by wire cutting, and ensure that the reference flatness error ≤ 0.05 mm; pre-treat the rolling mill, and evenly coat the working roll surface with a special lubricant for high-viscosity cold rolling; during multi-pass cold rolling, the reduction per pass is controlled at 0.3 mm; after each pass of rolling, use a laser thickness gauge to detect the thickness deviation, and gradually reduce the material to the target thickness (0.15 mm) through multi-pass reciprocating rolling; use a precision shearing machine to cut the cold-rolled sheet into the target size, and perform mirror grinding through a double-sided nanometer-level grinding machine, and finally control the thickness error within ±5 μm (target thickness 65 μm); use a diamond suspension (particle size 0.25 μm) for mechanical polishing to reduce the surface roughness; first use Keller reagent (2% HF + 3% HNO3 + 95% H2O) to corrode and remove the surface oxide layer, then place it in absolute ethanol for ultrasonic cleaning for 10 minutes, and finally blow-dry with high-purity nitrogen to obtain the high-entropy alloy intermediate layer.

[0044] Step 3: Transient liquid phase diffusion bonding of GH5188

[0045] (1) Grind and polish the base material GH5188 successively with sandpapers of 240#, 400#, 800#, 1000#, 1500#, 2000# and polishing liquid (SiO2:H2O2 = 8:2); after the grinding and polishing work is completed, place the base material GH5188 in absolute ethanol for ultrasonic cleaning;

[0046] (2) Place the prepared high-entropy alloy intermediate layer in the middle of the cleaned base material GH5188 and perform welding in a vacuum diffusion welding furnace;

[0047] (3) During the welding process in the vacuum diffusion welding furnace, in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 300 °C at a rate of 10 °C / min and held for 10 min. In the second stage, it is heated to 700 °C at a rate of 10 °C / min and held for 10 min. In the third stage, it is heated to 900 °C at a rate of 10 °C / min and held for 10 min. In the fourth stage, it is heated to the welding temperature of 1150 °C at a rate of 10 °C / min. In the fifth stage, it is held at the welding temperature of 1150 °C for 1 h, and a pressure of 5 MPa is applied, and then the sample is cooled to room temperature with the furnace, and the welding is completed; during the whole welding process, the vacuum degree of the vacuum diffusion welding furnace is always ≤ 4×10 -3 Pa.

[0048] Figure 1 、 Figure 3Figure 1 is the microstructure diagram and fracture surface morphology diagram of the welded joint obtained by transient liquid phase diffusion bonding using a high-entropy alloy interlayer in this embodiment, observed by scanning electron microscope (SEM). No white brittle phase appears in the microstructure. The mechanical properties of the welded joint in this embodiment were tested using an INSTRON 3382 electronic universal material testing machine. The shear strength of the joint can reach 932 MPa, and the fracture mode of the joint is ductile fracture.

[0049] Example 2

[0050] In this example, Co 25 Ni 20 Cr 20 Al 15 Ta 10 Ge5Zr3Y2 was used as the interlayer to perform transient liquid phase diffusion bonding on GH5188. The specific steps are as follows:

[0051] Step 1: Prepare the alloy ingot. Weigh the metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, and Y using a precision electronic balance. The atomic ratio of the elements Co:Ni:Cr:Al:Ta:Ge:Zr:Y = 25:20:20:15:10:5:3:2, and the element purity is greater than 99.9 wt.%. Wash the surface of the weighed metal element particles with absolute ethanol and place them in a drying oven for 1 hour. Place the metal element particles in a copper crucible according to the melting points of Co, Ni, Cr, W, Fe, B, and Si. The low-melting-point substances are placed at the bottom of the crucible, and the high-melting-point substances are placed on the top. Melt at least 5 times in both directions and apply electromagnetic stirring to ensure full fusion of the metal particles.

[0052] Step 2: Prepare the high-entropy alloy interlayer. Cut the alloy ingot into regular cuboid specimens (25 mm × 25 mm × 5 mm). Use a grinding machine to flatten the cutting surface to eliminate the surface texture generated by wire cutting and ensure that the reference flatness error ≤ 0.05 mm. Pretreat the rolling rolls, and evenly coat the working roll surface with a high-viscosity cold rolling special lubricant. During multi-pass cold rolling, the single-pass reduction is controlled at 0.4 mm. After each pass of rolling, use a laser thickness gauge to detect the thickness deviation, and gradually reduce the material to the target thickness (0.1 mm) through multi-pass reciprocating rolling. Use a precision shearing machine to cut the cold-rolled sheet into the target size, and perform mirror grinding through a double-sided nanometer-level grinding machine. Finally, control the thickness error within ±5 μm (target thickness 50 μm). Use a diamond suspension (particle size 0.25 μm) for mechanical polishing to reduce the surface roughness. First, remove the surface oxide layer by etching with Keller reagent (2% HF + 3% HNO3 + 95% H2O), then place it in absolute ethanol for ultrasonic cleaning for 10 minutes, and finally blow-dry with high-purity nitrogen to obtain the high-entropy alloy interlayer.

[0053] Step 3, Transient liquid phase diffusion bonding of GH5188

[0054] (1) Grind and polish the base material GH5188 successively with sandpapers of 240#, 400#, 800#, 1000#, 1500#, 2000# and polishing liquid (SiO2:H2O2 = 8:2); after the grinding and polishing work is completed, place the base material GH5188 in absolute ethanol for ultrasonic cleaning;

[0055] (2) Place the prepared high-entropy alloy interlayer in the middle of the cleaned base material GH5188 and carry out welding in a vacuum diffusion welding furnace;

[0056] (3) In the process of welding in the vacuum diffusion welding furnace, in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 300°C at a rate of 10°C / min and held for 10 min. In the second stage, it is heated to 700°C at a rate of 10°C / min and held for 10 min. In the third stage, it is heated to 900°C at a rate of 10°C / min and held for 10 min. In the fourth stage, it is heated to the welding temperature of 1150°C at a rate of 10°C / min. In the fifth stage, it is held at the welding temperature of 1150°C for 1 h, and a pressure of 5 MPa is applied. Subsequently, the sample is cooled to room temperature with the furnace, and the welding is completed; during the whole welding process, the vacuum degree of the vacuum diffusion welding furnace is always ≤4×10 -3 Pa.

[0057] Example 3

[0058] This example uses Co 25 Ni 20 Cr 20 Al 15 Ta 10 Ge5Zr3Y2 as the interlayer to carry out transient liquid phase diffusion bonding on GH5188. The specific steps are as follows:

[0059] Step 1, Prepare the alloy ingot: Weigh the metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, Y using a precision electronic balance. The atomic ratio of the elements Co:Ni:Cr:Al:Ta:Ge:Zr:Y = 25:20:20:15:10:5:3:2, and the element purity is greater than 99.9 wt.%. Clean the surface of the weighed metal element particles with absolute ethanol and place them in a drying oven for drying for 1 h. Place the metal element particles in a copper crucible according to the melting points of Co, Ni, Cr, W, Fe, B, Si. The low-melting-point substances are placed at the bottom of the crucible, and the high-melting-point substances are placed at the top; melt at least 5 times in both directions and apply electromagnetic stirring to ensure that the metal particles are fully fused;

[0060] Step 2: Prepare the high-entropy alloy intermediate layer. Cut the alloy ingot into regular cuboid specimens (25 mm × 25 mm × 5 mm), and use a grinding machine to flatten the cutting surface to eliminate the surface texture generated by wire cutting, ensuring that the reference flatness error ≤ 0.05 mm. Pretreat the rolling mill, and evenly coat the working roll surface with a special lubricant for high-viscosity cold rolling. During multi-pass cold rolling, the reduction per pass is controlled at 0.2 mm. After each pass of rolling, use a laser thickness gauge to detect the thickness deviation, and gradually reduce the material to the target thickness (0.2 mm) through multi-pass reciprocating rolling. Use a precision shearing machine to cut the cold-rolled sheet into the target size, and perform mirror grinding with a double-sided nanometer-level grinding machine. Finally, control the thickness error within ±5 μm (target thickness 80 μm). Use diamond suspension (grain size 0.25 μm) for mechanical polishing to reduce the surface roughness. First, use Keller's reagent (2% HF + 3% HNO3 + 95% H2O) to corrode and remove the surface oxide layer, then place it in absolute ethanol for ultrasonic cleaning for 10 minutes, and finally blow-dry with high-purity nitrogen to obtain the high-entropy alloy intermediate layer.

[0061] Step 3: Transient liquid-phase diffusion bonding of GH5188

[0062] (1) Grind and polish the base material GH5188 successively with sandpapers of 240#, 400#, 800#, 1000#, 1500#, 2000# and polishing liquid (SiO2:H2O2 = 8:2); after the grinding and polishing work is completed, place the base material GH5188 in absolute ethanol for ultrasonic cleaning;

[0063] (2) Place the prepared high-entropy alloy intermediate layer in the middle of the cleaned base material GH5188 and perform welding in a vacuum diffusion welding furnace;

[0064] (3) During the welding process in the vacuum diffusion welding furnace, in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 300 °C at a rate of 10 °C / min and held for 10 min. In the second stage, it is heated to 700 °C at a rate of 10 °C / min and held for 10 min. In the third stage, it is heated to 900 °C at a rate of 10 °C / min and held for 10 min. In the fourth stage, it is heated to the welding temperature of 1150 °C at a rate of 10 °C / min. In the fifth stage, it is held at the welding temperature of 1150 °C for 1 h, and a pressure of 5 MPa is applied, and then the sample is cooled to room temperature with the furnace, and the welding is completed; during the whole welding process, the vacuum degree of the vacuum diffusion welding furnace is always ≤ 4×10 -3 Pa.

[0065] Comparative Example 1

[0066] This comparative example uses the traditional intermediate layer Co 32 Cr 28 Ni 28B5Si2 is used for the transient liquid-phase diffusion bonding of GH5188, and the specific steps are as follows:

[0067] Step 1: Prepare the alloy ingot. Use a precision electronic balance to weigh the metal element particles Co, Ni, Cr, B, and Si. The atomic ratio of the elements Co:Ni:Cr:B:Si = 32:28:28:5:2, and the element purity is greater than 99.9 wt.%. Wash the surface of the weighed metal element particles with anhydrous ethanol and place them in a drying oven for 1 hour. Place the element particles Co, Ni, Cr, B, and Si in a copper crucible according to their melting points, with the low-melting-point substances at the bottom of the crucible and the high-melting-point substances at the top. Smelt at least 5 times in both directions and apply electromagnetic stirring to ensure full fusion of the metal particles;

[0068] Step 2: Prepare the intermediate layer. Cut the alloy ingot into regular rectangular parallelepiped specimens (25 mm × 25 mm × 5 mm). Use a grinding machine to level the cutting surface to eliminate the surface texture generated by wire cutting and ensure that the reference flatness error ≤ 0.05 mm. Pre-treat the rolling mill rolls, and evenly coat the working roll surface with a special high-viscosity cold rolling lubricant. During multi-pass cold rolling, the single-pass reduction is controlled at 0.3 mm. After each pass of rolling, use a laser thickness gauge to detect the thickness deviation, and gradually reduce the material to the target thickness (0.15 mm) through multi-pass reciprocating rolling. Use a precision shearing machine to cut the cold-rolled sheet to the target size, and perform mirror grinding through a double-sided nanogrinder. Finally, control the thickness error within ±5 μm (target thickness 65 μm). Use a diamond suspension (particle size 0.25 μm) for mechanical polishing to reduce the surface roughness. First, corrode and remove the surface oxide layer with Keller's reagent (2% HF + 3% HNO3 + 95% H2O), then place it in anhydrous ethanol for ultrasonic cleaning for 10 minutes, and finally blow-dry with high-purity nitrogen to obtain the high-entropy alloy intermediate layer.

[0069] Step 3: Transient liquid-phase diffusion bonding of GH5188;

[0070] (1) Grind and polish the base material GH5188 successively with sandpapers of 240#, 400#, 800#, 1000#, 1500#, 2000# and polishing liquid (SiO2:H2O2 = 8:2); After the grinding and polishing work is completed, place the base material GH5188 in anhydrous ethanol for ultrasonic cleaning;

[0071] (2) Place the prepared intermediate layer in the middle of the cleaned base material GH5188 and perform welding in a vacuum diffusion welding furnace;

[0072] (3) The welding process in the vacuum diffusion welding furnace. In the first stage, the vacuum diffusion welding furnace is heated from room temperature to 300 °C at a rate of 10 °C / min and held for 10 min. In the second stage, it is heated to 700 °C at a rate of 10 °C / min and held for 10 min. In the third stage, it is heated to 900 °C at a rate of 10 °C / min and held for 10 min. In the fourth stage, it is heated to the welding temperature of 1150 °C at a rate of 10 °C / min. In the fifth stage, it is held at the welding temperature of 1150 °C for 1 h with a pressure of 5 MPa applied, and then the sample is cooled to room temperature with the furnace, and the welding is completed; throughout the welding process, the vacuum degree of the vacuum diffusion welding furnace is always ≤ 4×10 -3 Pa.

[0073] Figure 2 , Figure 4 are the microstructural diagram and fracture surface morphology diagram observed by scanning electron microscope (SEM) of the welded joint obtained by transient liquid phase diffusion bonding using the traditional interlayer in this comparative example; compared with Example 1, in the traditional interlayer of this comparative example, since Ge element is not added and it contains melting-point-lowering elements B and Si, brittle phases of white boride and silicide appear in its microstructure. In addition, due to the lack of the role of Zr in refining grains and the role of Ta in suppressing grain coarsening at high temperatures in the traditional interlayer, the mechanical properties of the welded joint in this comparative example are detected by using an INSTRON 3382 type electronic universal material testing machine, and the shear strength of its joint only reaches 776 MPa. Observing the fracture surface, it is found that the fracture mode of the joint is a mixed fracture.

[0074] Combined with the attached Figures 1 to 4 , by comparing the interfacial microstructures of different interlayers, it can be found that when using the high-entropy alloy interlayer provided by the present invention for transient liquid phase diffusion bonding, white brittle phases cannot be observed in the welded joint. On the contrary, when using the traditional interlayer for transient liquid phase diffusion bonding, not only white brittle phases will appear at the interface, but also some pores will appear. Due to the appearance of brittle phases and pores, the comprehensive mechanical properties of the joint are restricted, and the strength and plasticity of the joint are reduced. Through subsequent mechanical property tests combined with fracture surface morphology analysis, it can be obtained that when using the traditional interlayer for transient liquid phase diffusion bonding of GH5188, the shear strength of the joint is 776 MPa, and observing the fracture surface, the fracture mode of the joint is a mixed fracture; when using the high-entropy alloy interlayer provided by the present invention for transient liquid phase diffusion bonding, the shear strength of the joint can reach 932 MPa. At the same time, the fracture mode of the joint is transformed into a ductile fracture; thus, it can be seen that the high-entropy alloy interlayer provided by the present invention effectively improves the mechanical properties of the joint.

[0075] 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 addition or replacement made by those skilled in the art based on the technical features of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high entropy alloy intermediate layer for GH5188 transient liquid phase diffusion bonding, characterized in that: The constituent elements of the high entropy alloy intermediate layer are composed of the following atomic ratios: Co:Ni:Cr:Al:Ta:Ge:Zr:Y=25:20:20:15:10:5:3:2, and the element purity is greater than 99.99wt.%.

2. A method for preparing a high entropy alloy intermediate layer for GH5188 transient liquid phase diffusion bonding, characterized in that: The method for preparing the high entropy alloy intermediate layer comprises the following steps: Step 1: weigh pure metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, and Y according to the atomic ratio of the constituent elements of the high entropy alloy intermediate layer according to claim 1, and wash them; Step 2: preparing alloy ingots by arc melting the pure metal element particles weighed in step 1; Step three, the alloy ingot prepared in step two is subjected to multiple cold rolling to obtain a cold-rolled sheet, the cold-rolled sheet is cut into sections and the upper and lower surfaces are ground to obtain a target intermediate layer, and then polished, corroded, cleaned and dried to obtain the high entropy alloy intermediate layer.

3. The method for preparing a high entropy alloy intermediate layer for GH5188 transient liquid phase diffusion bonding according to claim 2, characterized in that: The cleaning process in step 1 is to clean the surface of the weighed pure metal element particles with anhydrous ethanol and place them in a drying oven for 1 hour.

4. The method for preparing a high entropy alloy intermediate layer for GH5188 transient liquid phase diffusion bonding according to claim 2, characterized in that: In the process of preparing the alloy ingot by the arc melting method in step 2, the pure metal element particles Co, Ni, Cr, Al, Ta, Ge, Zr, and Y are placed in a copper crucible in order from low to high according to their melting points in step 1; the arc melting method is adopted, forward and reverse melting is performed more than 5 times, and electromagnetic stirring is performed to obtain the alloy ingot.

5. The method for preparing a high entropy alloy intermediate layer for GH5188 transient liquid phase diffusion bonding according to claim 2, characterized in that: In step 3, the cutting and flattening treatment is performed before the multiple cold rolling. The process is to cut the alloy ingot into regular rectangular parallelepipeds and use a grinder to flatten the cut surface so that the reference flatness error of the cut surface is ≤0.05mm.

6. The method for preparing a high entropy alloy intermediate layer for GH5188 transient liquid phase diffusion bonding according to claim 2, characterized in that: The multiple cold rolling in step three adopts multiple reciprocating rolling, the single-pass reduction is 0.2mm-0.4mm, the thickness of the cold-rolled sheet is 0.1mm-0.2mm, the grinding adopts a double-sided nano-grinding machine for mirror grinding, the thickness of the target intermediate layer is 50μm-80μm, and the thickness error is ±5μm.

7. The method for preparing a high entropy alloy intermediate layer for GH5188 transient liquid phase diffusion bonding according to claim 2, characterized in that: The polishing in step three is performed mechanically using a diamond suspension with a particle size of 0.25 μm; the corrosion is performed using Keller reagent corrosion to remove the surface oxide layer, the cleaning is performed using anhydrous ethanol ultrasonic cleaning, and the drying is performed by blowing and drying with high-purity nitrogen.

8. A GH5188 transient liquid phase diffusion bonding method, characterized in that: The connection method is: placing the high entropy alloy intermediate layer described in claim 1 or the high entropy alloy intermediate layer prepared by the preparation method described in claim 2 between the upper and lower layers of the base material GH5188, and then placing the whole in a vacuum diffusion welding furnace for welding.

9. A GH5188 transient liquid phase diffusion bonding method according to claim 8, characterized in that: The welding adopts a staged heating and pressurizing method. The specific welding process is as follows: in the first stage, the vacuum diffusion welding furnace is heated from room temperature to 300°C at a rate of 10°C / min and kept warm for 10 minutes; in the second stage, the temperature is increased from 300°C to 700°C at a rate of 10°C / min and kept warm for 10 minutes; in the third stage, the temperature is increased from 700°C to 900°C at a rate of 10°C / min and kept warm for 10 minutes; in the fourth stage, the temperature is increased from 900°C to the welding temperature of 1150°C at a rate of 10°C / min; in the fifth stage, the temperature is kept at the welding temperature of 1150°C for 1 hour, a pressure of 5MPa is applied, and then the furnace is cooled to room temperature; the vacuum degree of the vacuum diffusion welding furnace is ≤4×10 -3 Pa.

10. A GH5188 transient liquid phase diffusion bonding method according to claim 8, characterized in that: Before welding in the vacuum diffusion welding furnace, the base material GH5188 was ground and polished with sandpaper and polishing liquid; after the grinding and polishing, the base material GH5188 was ultrasonically cleaned in anhydrous ethanol.

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