CN119175373A

CN119175373A - Preparation method of composite intermediate layer suitable for nickel-based alloy TLP connection

Info

Publication number: CN119175373A
Application number: CN202411682001.9A
Authority: CN
Inventors: 赵万祺; 李远宾; 董佳鹏
Original assignee: AECC Shenyang Liming Aero Engine Co Ltd
Current assignee: AECC Shenyang Liming Aero Engine Co Ltd
Priority date: 2024-11-22
Filing date: 2024-11-22
Publication date: 2024-12-24
Anticipated expiration: 2044-11-22
Also published as: CN119175373B

Abstract

The invention discloses a preparation method of a composite intermediate layer suitable for nickel-based alloy TLP connection, which belongs to the field of diffusion welding and comprises an atomization powder preparation process, a ball milling process and a cold isostatic pressing process, wherein AuSi powder is prepared through the atomization powder preparation process, then the AuSi powder and NiTi powder are mixed through the ball milling process, and finally a composite intermediate layer blank is obtained through cold isostatic pressing. According to the invention, the AuSi composite interlayer is prepared by a powder metallurgy process, so that the distribution uniformity of NiTi particles in an AuSi matrix is improved, and the problems of AuSi eutectic structure residues in a welding line, solidification thermal cracks in the welding line and the like caused by uneven distribution of the NiTi particles are solved. The mass ratio of the AuSi powder and the NiTi powder can be completely reacted through the accurate calculation of a chemical reaction formula, and the addition amount of NiTi particles is accurately controlled through a mechanical ball milling process, so that the problem that excessive Ti element easily reacts with Au element to form a brittle Au ₄ Ti compound in the welding process is solved.

Description

Preparation method of composite intermediate layer suitable for nickel-based alloy TLP connection

Technical Field

The invention belongs to the field of diffusion welding, and particularly relates to a preparation method of a composite intermediate layer suitable for nickel-based alloy TLP connection.

Background

The instantaneous liquid phase diffusion connection (TLP) technology is a research hot spot which is raised at home and abroad in recent years, and the technology adopts a material with a melting point lower than that of a base material as an intermediate layer, when the intermediate layer is heated to a connection temperature, the intermediate layer is melted, an instantaneous liquid film is formed on a joint surface, and in the heat preservation process, a low-temperature connection and high-temperature use of a joint are realized along with the diffusion of a low-melting-point component to the base material or the formation of a high-melting-point compound, so that the remelting temperature of a welding seam is increased, and the damage to the performance of the base material in the welding heat process is reduced. The current transient liquid phase connection technology has different technical characteristics due to different connection temperatures.

When the melting temperature of the intermediate layer is below 450 ℃, namely the soldering temperature, the improvement of the soldering seam remelting temperature mainly depends on high-melting-point compounds formed by the reaction of the intermediate layer, and the part of the intermediate layer is mainly made of copper-tin, silver-indium and other solders, because the intermediate layer materials (such as copper-tin, silver-indium and the like) react with the welded metals to form new intermetallic compounds in the welding process. The melting point of these compounds tends to be higher than that of the original braze. The binary phase diagram shows that the eutectic point temperature of copper and tin and the eutectic point temperature of silver and indium are low, so that the welding temperature is greatly reduced, but the elements further react with each other along with the extension of the heat preservation time after welding to form more complex intermetallic compounds. The melting point of the formed copper-tin, silver-indium and other compounds can be far higher than that of the original solder, and can reach more than 650 ℃ at the highest, because the intermetallic compound has more complex structure and can be melted with higher energy. Thus, the reflow temperature of the weld is increased due to the high melting point compound formed by the intermediate layer reaction, despite the lower initial welding temperature. This eliminates the eutectic liquid phase in the weld, forming a weld structure with solid solution and intermetallic compounds as the main components. However, the intermetallic compounds formed by this method are mostly continuously distributed, and the brittle and hard nature thereof leads to a generally lower joint strength.

When the melting temperature of the used intermediate layer is above 450 ℃, namely the brazing temperature, the improvement of the remelting temperature of the welding seam mainly depends on the diffusion of the melting-reducing element to the base metal, and the part of the intermediate layer is mainly made of solder containing Si and B elements such as BNI ₂. The radii of Si and B atoms are smaller, so that the Si and B atoms are easy to diffuse into the base material to form solid solution, but the joint needs to be subjected to long-time high-temperature heat treatment after welding to homogenize element diffusion, so that the joint is ensured to have reliable high-temperature strength, the production efficiency is reduced, and the risk of performance deterioration of the base material is increased.

In view of the above, we have designed a method for preparing a composite intermediate layer by screen printing NiTi particles on the surface of an AuSi eutectic metal foil (patent No. ZL 202111282454.9) according to a low-melting-point eutectic binary phase diagram of au—si and the principle that Si element can form a high-melting-point NiSiTi ternary compound with Ni and Ti elements at low temperature. The method can convert AuSi eutectic structures in the welding line into dispersion strengthening structures mainly comprising pure Au (melting point 1064 ℃) and NiSiTi whiskers (melting point 1647 ℃) and the welding temperature is only 430 ℃. The method can not only improve the mechanical property of the joint, but also avoid the damage of the thermal process to the performance of the base material.

However, this method has many problems found in practical use. Firstly, the uniformity and the layering thickness of NiTi particles are screen-printed on an AuSi foil, the NiTi particles and terpineol are greatly influenced by the operation level of operators, secondly, the NiTi particles and the terpineol are prepared into a coating, solid-liquid separation is easy to generate after long-term placement, the NiTi particles are more easy to agglomerate due to the surface energy effect, a large amount of AuSi eutectic structures exist at certain parts of a welding line after welding due to the lack of the NiTi particles, and other parts of the welding line are early solidified and contracted due to the existence of excessive NiTi particles, so that hot cracks are generated near the NiTi particles (see figure 1), when the assembled AuSi intermediate layer is placed for a long time, the state that the NiTi particles fall off in the process of carrying and charging the AuSi intermediate layer can be caused due to the fact that the terpineol serving as a binder is easy to volatilize. These problems can result in some TLP solder joints that not only fail to achieve the intended use temperature, but also have low room temperature strength.

Disclosure of Invention

Aiming at the defects, the invention provides a preparation method of a composite interlayer suitable for nickel-based alloy TLP connection. According to the invention, the AuSi composite intermediate layer is prepared by adopting a powder metallurgy process, the addition amount of NiTi particles is precisely controlled by adopting a chemical calculation mass ratio, the uniformity of distribution of the NiTi particles in an AuSi matrix is improved, and the problems of poor process consistency and large fluctuation of the quality of welded products of the AuSi composite intermediate layer prepared by adopting a screen printing process are solved.

The invention provides a preparation method of a composite intermediate layer, which comprises the technical scheme of an atomization powder preparation process, a ball milling process and a cold isostatic pressing process, wherein AuSi powder is prepared through the atomization powder preparation process, then the AuSi powder and NiTi powder are mixed through the ball milling process, and finally a composite intermediate layer blank is obtained through cold isostatic pressing.

And (3) an atomization powder preparation process, namely proportioning pure Au and pure Si according to a mass ratio of 96.85:3.15, putting the mixture into an atomization powder preparation device, heating the mixture to 1560-1570 ℃ by using a high-frequency power supply, enabling the atomization pressure of argon to be 1-1.5 MPa, enabling the diameter of a nozzle of equipment to be 3mm, sieving the collected AuSi powder after atomization cooling, and screening the AuSi powder with the particle size less than or equal to 30 mu m for preparing the composite intermediate layer.

The ball milling process comprises the steps of enabling the particle size of AuSi powder to be less than or equal to 30 mu m, enabling the particle size of NiTi powder to be less than or equal to 15 mu m, enabling the mass ratio of AuSi powder to NiTi powder to be between 7.5:1 and 8:1, adopting a planetary ball mill, enabling ball milling atmosphere to be high-purity argon, enabling ball material to be ZrO ₂, enabling ball material ratio to be between 2:1 and 3:1, enabling ball milling time to be 3h, and enabling the rotating speed to be constant to be 200r/min.

The cold isostatic pressing forming process has the pre-forming process pressure parameter of 25MPa-35MPa, dwell time of more than or equal to 120s, and cold isostatic pressing parameter of more than or equal to 250MPa and dwell time of more than or equal to 180s.

The method comprises the steps of assembling a sample to be welded, clamping the sample by a clamp, placing the sample into a vacuum diffusion welding furnace, applying pressure and vacuum pumping, heating the sample to 430 ℃ from room temperature at the speed of 10 ℃ per minute, preserving heat for 30min, cooling the sample to 200 ℃ at the speed of 10 ℃ per minute, cooling the sample to room temperature, discharging the sample from the furnace, and carrying out shear test, wherein the average shear strength of the room temperature of a welded joint reaches 147MPa, and the average shear strength of the welded joint at the temperature of 700 ℃ reaches 47MPa.

The technical scheme of the invention has the beneficial effects that:

1. According to the technical scheme, the AuSi composite interlayer is prepared through a powder metallurgy process, so that the distribution uniformity of NiTi particles in an AuSi matrix is improved, and the problems that AuSi eutectic structure residues exist in a welding line and solidification thermal cracks appear in the welding line due to uneven distribution of the NiTi particles are solved. The process improves the consistency of the preparation process of the AuSi composite intermediate layer, and can obviously improve the quality of welded products.

2. According to the technical scheme, the mass ratio of the AuSi powder to the NiTi powder can be calculated accurately through a chemical reaction formula, the addition amount of NiTi particles is controlled accurately through a mechanical ball milling process, and the problem that excessive Ti element is easy to react with Au element to form a brittle Au ₄ Ti compound in the welding process is solved.

3. The technical scheme of the invention can realize batch production and long-term storage of the AuSi composite intermediate layer, and is convenient for realizing large-gap TLP diffusion welding and crack repair welding.

Drawings

FIG. 1 solidification hot cracking caused by excess NiTi particles;

fig. 2 shows morphology of AuSi particles after pulverization and screening;

FIG. 3 structure formed by NiTi particles having a particle size of 50 μm;

FIG. 4 structure formed by NiTi particles having a particle size of 25 μm;

FIG. 5 texture formed by NiTi particles 15 μm in size.

Detailed Description

In the embodiment, the AuSi composite intermediate layer prepared by the technical scheme of the invention is taken as an example to connect NiTi alloy.

A preparation method of a composite intermediate layer suitable for nickel-based alloy TLP connection comprises an atomization powder process, a ball milling process and a cold isostatic pressing process.

The atomization pulverizing process is based on the steps of firstly determining the proportion of Au to Si and forming gold-silicon eutectic alloy according to the mass ratio of 96.85:3.15, secondly determining the AuSi powder screening standard, and testing AuSi powder with different particle diameters to find the following defects in the preparation process of the composite intermediate layer:

1. the larger the particle size of AuSi powder is, the higher the hollow probability exists inside;

2. the larger the particle size of AuSi powder, the worse the distribution uniformity of NiTi particles after mixing and ball milling with the NiTi particles;

3. The larger the AuSi powder particle size is, the higher the porosity of the composite intermediate layer blank obtained by cold isostatic pressing is.

Therefore, auSi powder screening is based on particle size of 30 μm or less (see FIG. 2).

Then determining AuSi smelting temperature, and verifying that when the heating temperature is less than 1560 ℃, the melt fluidity is reduced, and the breaking effect of the melt flow is poor under the action of high-speed gas flow. When the heating temperature is more than 1570 ℃, the probability of hard and brittle amorphous phase occurrence is increased after melt atomization and is unfavorable for subsequent cold isostatic pressing.

And finally determining the argon atomization pressure, wherein when the argon atomization pressure is less than 1MPa, the obtained AuSi powder with the particle size less than or equal to 30 mu m occupies smaller space, and the argon atomization pressure is more than 1.5MPa, and although the obtained AuSi powder with the particle size less than or equal to 30 mu m occupies larger space, the proportion of the generated hollow powder is correspondingly increased, and the void defects are easily formed in a welding seam after welding, so that the joint durability and the fatigue strength are reduced, and therefore, the argon atomization pressure is preferably 1MPa-1.5 MPa.

The ball milling process is based on the chemical reaction formula calculation, when the mass ratio of AuSi powder to NiTi particles is 8.32:1, the Si element and the Ni and Ti elements can be ensured to completely react and form NiSiTi ternary whiskers, but the theoretical calculation result is only that. Experiments show that for NiTi particles with the particle diameter of more than 40 mu m, after compact NiSiTi whiskers are formed on the surface, ni and Ti elements in the particles can be prevented from further reacting with Si in the middle layer (see figure 3). Therefore, even when the welding temperature is 430 ℃ and the heat is preserved for a long time, niTi particles and AuSi eutectic remain in the weld joint at the same time.

Experiments show that when the particle size of the NiTi particles is less than or equal to 25 mu m, the specific surface energy is increased, so that the reaction rate of Ni and Ti and Si is accelerated, and the NiTi particles can completely react and consume under the condition of heat preservation at 430 ℃ for 30min (see figure 4). However, niSiTi whiskers formed by the particles with the size are densely distributed in a cluster shape, so that the dispersibility is poor, and the dispersion strengthening effect on the welding line is poor. When the particle size of NiTi particles is less than or equal to 15 mu m, niSiTi crystal whiskers formed under the condition of heat preservation at 430 ℃ for 30min are dispersed (see figure 5), and the dispersion strengthening effect of the weld joint is good. Experiments prove that when the particle size of the NiTi particles is less than or equal to 15 mu m, the mass ratio of the AuSi powder to the NiTi particles is between 7.5:1 and 8:1, the microstructure of the weld after brazing thermal cycling is optimal, the ratio is higher than the optimum value, the eutectic structure of the weld is remained, and the ratio is lower than the optimum value, so that the defects of the weld structure are increased.

The cold isostatic pressing forming process is based on the determination of preforming process parameters, wherein different loading pressures of 5MPa, 10 MPa, 20MPa, 30MPa, 40MPa and dwell times of 0.5min, 1min, 2min are tried through experiments, the preformed sheets obtained when the pressure is less than 20MPa are found to be loose and fragile, layering and splitting are easy to occur when the pressure reaches 40MPa and the dwell time is too short, so that the optimal preforming process pressure parameters of preforming are determined to be 25MPa-35MPa, the dwell time is more than or equal to 120s, and the prepared preformed sheets are respectively packed for waiting for subsequent operation. In order to further improve the density of the brazing sheet, the prefabricated sheet obtained after static pressure at room temperature is subjected to cold isostatic pressing operation. Because the AuSi powder has good plasticity, the NiTi particles difficult to deform have small particle size and small content, when the cold isostatic pressure is more than or equal to 250MPa and the dwell time is more than or equal to 180s, the porosity of the composite intermediate layer can be reduced to 1.25 percent, the pressure is continuously increased or the dwell time is prolonged, and the continuous reduction trend of the porosity of the composite intermediate layer is not obvious.

The method comprises the steps of assembling a sample to be welded, clamping the sample by a clamp, placing the sample into a vacuum diffusion welding furnace, applying pressure and vacuum pumping, heating the sample to 430 ℃ from room temperature at a speed of 10 ℃ per minute, preserving heat for 30 minutes, cooling the sample to 200 ℃ at a speed of 10 ℃ per minute, and discharging the sample from the furnace after the sample is assembled and clamped by the clamp. Through shear test, the average shear strength of the welded joint at room temperature can reach 147MPa, and the average shear strength at 700 ℃ can reach 47MPa.

Example 1

(1) Pure Au and pure Si are proportioned according to the mass ratio of 96.85:3.15 and are put into an atomization powder making device, a high-frequency power supply is utilized to heat to 1560 ℃, molten alloy flows out of a spray pipe in a bottom pouring mode, high-pressure argon is used for crushing at a spray nozzle, wherein the atomization pressure of the argon is 1MPa, the diameter of a device nozzle is 3mm, the collected AuSi powder is sieved after atomization cooling, and the AuSi powder with the particle size less than or equal to 30 mu m is sieved to be used for preparing a composite intermediate layer;

(2) The AuSi powder with the grain diameter less than or equal to 30 mu m and the NiTi powder with the grain diameter less than or equal to 15 mu m are put into a ball milling tank of a planetary ball mill according to the mass ratio of 7.5:1, wherein the ball material is ZrO ₂ ceramic, the ball material ratio is 2:1, the ball milling atmosphere is high-purity argon, the ball milling time is 3 hours, and the rotating speed is constant at 200r/min;

(3) Adding the ball-milled mixed powder into a die, and performing normal-temperature static pressure preforming by using a tablet press to obtain a preformed sheet, wherein the preforming process pressure parameter is 25MPa, and the dwell time is 120s. Placing the preformed sheet into a rubber sheath, and placing the rubber sheath into a cold isostatic press for oil pressure to obtain a composite intermediate layer blank, wherein the cold isostatic pressing parameters are that the pressure is 250MPa and the pressure maintaining time is 180s;

(4) Rolling the composite intermediate layer blank obtained by cold isostatic pressing into a metal foil with the thickness of 100 mu m by adopting a multistage cold rolling process;

(5) The surface of the rolled intermediate layer foil is polished by 1500# sand paper and is ultrasonically cleaned by acetone and then is used for NiTi alloy homoplasmy TLP diffusion welding connection, the welding process comprises the steps of assembling a sample to be welded, clamping by a graphite fixture, putting the sample into a vacuum diffusion welding furnace, applying 1MPa pressure, pumping the sample to the vacuum degree to 5X 10 ^-4 Pa, heating the sample to 430 ℃ from room temperature at the speed of 10 ℃ per minute, preserving heat for 30 minutes, then cooling the sample to 200 ℃ at the speed of 10 ℃ per minute, and then cooling the sample to room temperature and discharging the sample;

(6) Through shear test, the average shear strength of the welded joint at room temperature can reach 145MPa, and the average shear strength at 700 ℃ can reach 39MPa.

Example 2

(1) Pure Au and pure Si are proportioned according to the mass ratio of 96.85:3.15 and are put into an atomization powder making device, a high-frequency power supply is utilized to heat to 1570 ℃, molten alloy flows out of a spray pipe in a bottom pouring mode, high-pressure argon is used for crushing at a nozzle, wherein the atomization pressure of the argon is 1.5MPa, the diameter of a device nozzle is 3mm, the collected AuSi powder is sieved after atomization cooling, and the AuSi powder with the particle size less than or equal to 30 mu m is screened to be used for preparing a composite intermediate layer;

(2) The AuSi powder with the grain diameter less than or equal to 30 mu m and the NiTi powder with the grain diameter less than or equal to 15 mu m are put into a ball milling tank of a planetary ball mill according to the mass ratio of 8:1, wherein the ball material is ZrO ₂ ceramic, the ball material ratio is 3:1, the ball milling atmosphere is high-purity argon, the ball milling time is 3 hours, and the rotating speed is constant at 200r/min;

(3) Adding the ball-milled mixed powder into a die, and performing normal-temperature static pressure preforming by using a tablet press to obtain a preformed sheet, wherein the preforming process pressure parameter is 35MPa, and the dwell time is 130s. Placing the preformed sheet into a rubber sheath, and placing the rubber sheath into a cold isostatic press for oil pressure to obtain a composite intermediate layer blank, wherein the cold isostatic pressing parameters are that the pressure is 250MPa and the pressure maintaining time is 180s;

(6) Through shear test, the average shear strength of the welded joint at room temperature can reach 142MPa, and the average shear strength at 700 ℃ can reach 41MPa.

Example 3

(1) Pure Au and pure Si are proportioned according to the mass ratio of 96.85:3.15 and put into an atomization powder making device, the mixture is heated to 1565 ℃ by a high-frequency power supply, molten alloy flows out of a spray pipe in a bottom pouring mode, the spray pipe is broken by high-pressure argon, wherein the atomization pressure of the argon is 1.2MPa, the diameter of a device nozzle is 3mm, the collected AuSi powder is sieved after atomization cooling, and the AuSi powder with the particle size less than or equal to 30 mu m is screened to be used for preparing a composite intermediate layer;

(2) The AuSi powder with the grain diameter less than or equal to 30 mu m and the NiTi powder with the grain diameter less than or equal to 15 mu m are put into a ball milling tank of a planetary ball mill according to the mass ratio of 7.7:1, wherein the ball material is ZrO ₂ ceramic, the ball material ratio is 2:1, the ball milling atmosphere is high-purity argon, the ball milling time is 3 hours, and the rotating speed is constant at 200r/min;

(3) Adding the ball-milled mixed powder into a die, and performing normal-temperature static pressure preforming by using a tablet press to obtain a preformed sheet, wherein the preforming process pressure parameter is 30MPa, and the dwell time is 125s. Placing the preformed sheet into a rubber sheath, and placing the rubber sheath into a cold isostatic press for oil pressure to obtain a composite intermediate layer blank, wherein the cold isostatic pressing parameters are that the pressure is 255MPa and the dwell time is 190s;

(6) Through shear test, the average shear strength of the welded joint at room temperature can reach 147MPa, and the average shear strength at 700 ℃ can reach 47MPa.

Claims

1. A method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy, characterized in that it includes an atomization powder making process, a ball milling process and a cold isostatic pressing process; AuSi powder is prepared by the atomization powder making process, and then the AuSi powder is mixed with NiTi powder by the ball milling process, and finally the composite intermediate layer blank is obtained by cold isostatic pressing.

2. A method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 1, characterized in that AuSi powder is prepared, and the mass ratio of pure Au and pure Si in the raw material is 96.85:3.15.

3. The method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 1 is characterized in that the atomization powder making process is as follows: pure Au and pure Si are mixed according to a mass ratio and placed in an atomization powder making device, heated to between 1560°C and 1570°C by a high-frequency power supply, the argon atomization pressure is 1MPa-1.5MPa, and the AuSi powder is collected after atomization cooling.

4. The method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 3 is characterized in that, in the atomization powder making process, the nozzle diameter of the equipment is 3 mm, and after atomization cooling, the collected AuSi powder is sieved to screen the AuSi powder with a particle size of ≤30 μm.

5. The method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 1, characterized in that, in a ball milling process, the mass ratio of AuSi powder to NiTi powder is between 7.5:1 and 8:1, and a planetary ball mill is used for mixing.

6. The method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 5, characterized in that, in the ball milling process, the particle size of AuSi powder is ≤30 μm, and the particle size of NiTi powder is ≤15 μm.

7. A method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 5, characterized in that the ball milling process: the ball milling atmosphere is high-purity argon, the ball material is _ZrO2 , the ball material ratio is between 2:1-3:1, the ball milling time is 3 hours, and the rotation speed is constant at 200r/min.

8. The method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 1 is characterized in that the cold isostatic pressing process: the pre-forming process pressure parameters are 25MPa-35MPa, the holding time is ≥120s, and the cold isostatic pressing parameters are pressure ≥250MPa, and the holding time is ≥180s.

9. A method for preparing a composite intermediate layer suitable for TLP connection of a nickel-based alloy according to claim 8, characterized in that the composite intermediate layer blank obtained by cold isostatic pressing is rolled into a 100 μm thick metal foil by a multi-stage cold rolling process; the surface of the rolled intermediate layer foil is polished and cleaned, and then used for NiTi alloy homogeneous TLP diffusion welding connection, and the welding process comprises: assembling the sample to be welded, clamping it with a fixture, placing it in a vacuum diffusion welding furnace, applying pressure, evacuating the vacuum degree, heating from room temperature to 430°C at a rate of 10°C/min, keeping the temperature for 30 minutes, then cooling to 200°C at a rate of 10°C/min, and then cooling the furnace to room temperature and taking it out of the furnace; after shear testing, the average shear strength of the welded joint at room temperature reaches 147MPa, and the average shear strength at 700°C reaches 47MPa.