CN105195846A - Multi-scale combined method for improving strength of soldered joint made of conductive ceramic base materials - Google Patents

Abstract

A multi-scale joint method for improving the strength of a conductive ceramic-based material brazing joint, the invention relates to a multi-scale joint method for improving the strength of a conductive ceramic-based material brazed joint. The present invention aims to solve the problems of low joint strength, large residual stress and low reliability caused by the difference in thermal expansion coefficient between the ceramic base material and the metal in the existing conductive ceramic base material brazing method. The method is as follows: 1. Conductive ceramic base material The surface treatment of the connecting surface of the base metal; 2. Preparation of brazing material; 3. Placement of the brazing material; 4. Vacuum brazing connection, which is completed. The present invention relieves the stress of the joint to the greatest extent and improves the strength and reliability of the joint through the joint action of the macro scale and the micro scale. The compressive shear strength of the conductive ceramic base material brazing joint obtained by the method is 155-265 MPa, which is 165%-345% higher than that of the conventional flat interface and no reinforcing phase brazing joint. The invention is applied to the field of brazing.

Description

A Multi-Scale Combined Method for Improving the Strength of Conductive Ceramic-Based Materials Brazed Joints

technical field

The invention relates to a multi-scale combined method for improving the strength of a brazing joint of a conductive ceramic base material.

Background technique

With its excellent high-temperature comprehensive performance, ceramic materials have broad application prospects in many extremely harsh environments such as aviation and aerospace, and are the preferred materials for hot-end components today. However, ceramic materials are brittle, and it is difficult to obtain large-sized and complex-shaped structural parts, which greatly limits the engineering application of ceramic materials. Therefore, realizing reliable connections between ceramic materials themselves or metal materials has become one of the key technologies for the application of ceramic materials. . Generally, the active brazing method is used to realize the connection of ceramic-ceramic and ceramic-metal. This method has simple process, good repeatability, and strong adaptability to the size and shape of the connecting parts. The traditional active brazing method forms a reliable connection by adding active metal elements (such as Ti, Zr, Hf, etc.) to the solder and using them to chemically react with the ceramic surface to form chemical bonds. However, due to the huge difference in the thermal expansion properties of ceramics and metals (metal base material or solder), thermal mismatch during joint cooling produces residual thermal stress at the joint interface, reducing joint strength and reliability.

Contents of the invention

The present invention aims to solve the problems of low joint strength, large residual stress and low reliability caused by the difference in thermal expansion coefficient between the ceramic base material and the metal in the existing conductive ceramic base material brazing method, and provides a multi-scale joint improvement of electrical conductivity. A method for brazing joint strength of ceramic-based materials.

The present invention is a multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints, which is carried out according to the following steps:

1. Surface treatment of the connection surface of the conductive ceramic base material:

a. Use precision wire cutting technology to process the connecting surface of the conductive ceramic base material and the corresponding connector into a circular arc surface. If the thermal expansion coefficient of the conductive ceramic base material is smaller than the thermal expansion coefficient of the corresponding connector, the conductive ceramic base material The surface is convex, and the surface of the corresponding connector is concave, and the radians are equal; if the thermal expansion coefficient of the conductive ceramic base material is greater than the thermal expansion coefficient of the corresponding connector, the surface of the conductive ceramic base material is concave, and the corresponding connector is convex. equal;

b. Process the connecting surface of the conductive ceramic base material treated in step a into a tooth-shaped groove structure by wire cutting, wherein the groove depth is 0.3-3mm, the groove width is 0.3-3mm, and the distance between the two grooves is 0.3-2mm , the angle between the groove depth direction and the tangent direction of the surface to be connected is 90-150°;

c. Grinding and cleaning the conductive ceramic base material after the surface treatment in step b and the corresponding connector after the surface treatment in step a, then cleaning and drying with acetone to obtain the cleaned conductive ceramic base material and corresponding connector;

2. Preparation of brazing filler metal: Composite brazing filler metal includes B source and Ti-containing eutectic alloy system, in which the molar ratio of Ti element to B element is (10~1):1; B source is B, TiB ₂ , ZrB ₂ , HfB _2. A mixture of any one or several of HfB, BN and B ₄ C in any ratio, and the Ti-containing eutectic alloy system is Ti-Ni, Ti-Cu, Ag-Cu-Ti or Ti-Si; if If the B source is contained in the conductive ceramic base material or the corresponding connector, the B source is not added or the amount of B source is reduced; the volume content of TiB whiskers in the brazed joint of the final product is not less than 5%;

3. Placement of solder

The composite solder, terpineol and ethyl cellulose prepared in step 2 are uniformly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of the composite solder, terpineol and ethyl cellulose is 10:(0.2～2 ): (0.4～3), apply the composite solder paste between the conductive ceramic base material and the connecting surface of the corresponding connector after cleaning in step 1, to obtain the assembly to be welded; or prepare the composite solder paste The component to be welded is obtained by throwing the tape or extruding it into a foil and placing it between the corresponding connectors;

4. Vacuum brazing connection

Place the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 ~ 1×10 ^-3 Pa, and then raise the temperature of the vacuum brazing furnace to T ₁ at a rate of 15°C/min. And keep it warm for 5min~10min, then raise the temperature to the brazing temperature T2 at a speed of ₁₀ ℃/min, and keep it warm for 10min~20min, then cool down to 400℃ at a speed of 5~10℃/min, and finally cool with the furnace to complete Brazing connection of conductive ceramic-based materials; wherein T ₁ =T ₂ -(100°C-200°C), and T ₂ is 10%-30% higher than the liquidus temperature of the solder.

A multi-scale joint method of the present invention for improving the strength of conductive ceramic-based material brazed joints is carried out according to the following steps:

1. Surface treatment of the connection surface of the conductive ceramic base material:

Process the connecting surface of the conductive ceramic base material into a tooth-shaped groove structure by wire cutting to obtain a surface-treated conductive ceramic base material. The groove depth is 0.3-3mm, the groove width is 0.3-3mm, and the distance between the two grooves The angle between the groove depth direction and the tangent direction of the surface to be connected is 90-150°; the corresponding connector and the surface-treated conductive ceramic base material are polished and cleaned, then cleaned with acetone and dried to obtain a clean The final conductive ceramic base material and corresponding connectors;

2. Preparation of brazing filler metal: Composite brazing filler metal includes B source and Ti-containing eutectic alloy system, in which the molar ratio of Ti element to B element is (10~1):1; B source is B, TiB ₂ , ZrB ₂ , HfB _2. A mixture of any one or several of HfB, BN and B ₄ C in any ratio, and the Ti-containing eutectic alloy system is Ti-Ni, Ti-Cu, Ag-Cu-Ti or Ti-Si; if If the B source is contained in the conductive ceramic base material or the corresponding connector, the B source is not added or the amount of B source is reduced; the volume content of TiB whiskers in the brazed joint of the final product is not less than 5%;

3. Placement of solder

The composite solder, terpineol and ethyl cellulose prepared in step 2 are uniformly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of the composite solder, terpineol and ethyl cellulose is 10:(0.2～2 ): (0.4～3), apply the composite solder paste between the conductive ceramic base material and the connecting surface of the corresponding connector after cleaning in step 1, to obtain the assembly to be welded; or prepare the composite solder paste The component to be welded is obtained by throwing the tape or extruding it into a foil and placing it between the corresponding connectors;

4. Vacuum brazing connection

Place the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 ~ 1×10 ^-3 Pa, and then raise the temperature of the vacuum brazing furnace to T ₁ at a rate of 15°C/min. And keep it warm for 5min~10min, then raise the temperature to the brazing temperature T2 at a speed of ₁₀ ℃/min, and keep it warm for 10min~20min, then cool down to 400℃ at a speed of 5~10℃/min, and finally cool with the furnace to complete Brazing connection of conductive ceramic-based materials; where T ₁ =T ₂ -(100°C-200°C), T ₂ is 10%-30% higher than the liquidus temperature of the solder; wherein the conductive ceramic-based base material and The thermal expansion coefficients of the corresponding connectors are equal.

The preparation method of the present invention has the following advantages:

(1) Make full use of the conductive properties of conductive ceramic-based materials at the macro scale and introduce precision wire cutting technology to carry out secondary design and processing of various forms of surface structures on the connection surface, which can effectively slow down the ceramic/metal connection interface near the ceramic side. Stress concentration, and the process is simple, easy to operate, and low in cost;

(2) At the microscopic scale, TiB whiskers can be generated in situ near the brazing interface and in the brazing filler metal layer at the same time, and have the following effects at the same time:

a. Perform secondary processing on the connection interface at the microscopic level. The TiB whiskers distributed near the interface can increase the interface connection area at the microscopic scale and effectively slow down the stress concentration on the ceramic/metal connection interface near the ceramic side. The direction of residual stress can be reversed;

b. The material of the solder layer is modified, and the solder layer is changed from the original pure metal material to a metal-based TiB whisker-reinforced composite material, which effectively reduces the thermal expansion coefficient of the solder layer and reduces the residual stress;

c. The TiB whiskers generated in situ can effectively reverse the direction of the residual stress of the joint and reduce the probability of cracks.

(3) Through the combined effect of macroscale and microscale, the joint stress is relieved to the greatest extent, and the strength reliability of the joint is improved. The compressive shear strength of the conductive ceramic base material brazing joint obtained by the method is 155-265 MPa, which is 165%-345% higher than that of the conventional flat interface and no reinforcing phase brazing joint.

Description of drawings

Fig. 1 is the front view of the surface-treated ZrC conductive ceramic base material in embodiment one;

Fig. 2 is the sectional view of Fig. 1;

Fig. 3 is the ZrC conductive ceramic base material/Nb metal base material joint assembly schematic diagram after the brazing connection of embodiment one conductive ceramic base material; Wherein a is the corresponding connector Nb base material, b is the composite solder, and c is the tooth shape Groove structure, d is ZrC conductive ceramic base material;

Fig. 4 is a schematic diagram of the assembly of the brazed joint with a conventional flat interface and no reinforcing phase compared with Example 1, where a is the Nb base material of the corresponding connector, b is the composite solder, and d is the ZrC conductive ceramic base material.

Detailed ways

Specific implementation mode 1: In this implementation mode, a multi-scale joint method for improving the strength of a conductive ceramic-based material brazed joint is carried out according to the following steps:

1. Surface treatment of the connection surface of the conductive ceramic base material:

a. Use precision wire cutting technology to process the connecting surface of the conductive ceramic base material and the corresponding connector into a circular arc surface. If the thermal expansion coefficient of the conductive ceramic base material is smaller than the thermal expansion coefficient of the corresponding connector, the conductive ceramic base material The surface is convex, and the surface of the corresponding connector is concave, and the radians are equal; if the thermal expansion coefficient of the conductive ceramic base material is greater than the thermal expansion coefficient of the corresponding connector, the surface of the conductive ceramic base material is concave, and the corresponding connector is convex. equal;

b. Process the connecting surface of the conductive ceramic base material treated in step a into a tooth-shaped groove structure by wire cutting, wherein the groove depth is 0.3-3mm, the groove width is 0.3-3mm, and the distance between the two grooves is 0.3-2mm , the angle between the groove depth direction and the tangent direction of the surface to be connected is 90-150°;

c. Grinding and cleaning the conductive ceramic base material after the surface treatment in step b and the corresponding connector after the surface treatment in step a, then cleaning and drying with acetone to obtain the cleaned conductive ceramic base material and corresponding connector;

2. Preparation of brazing filler metal: Composite brazing filler metal includes B source and Ti-containing eutectic alloy system, in which the molar ratio of Ti element to B element is (10~1):1; B source is B, TiB ₂ , ZrB ₂ , HfB _2. A mixture of any one or several of HfB, BN and B ₄ C in any ratio, and the Ti-containing eutectic alloy system is Ti-Ni, Ti-Cu, Ag-Cu-Ti or Ti-Si; if If the B source is contained in the conductive ceramic base material or the corresponding connector, the B source is not added or the amount of B source is reduced; the volume content of TiB whiskers in the brazed joint of the final product is not less than 5%;

3. Placement of solder

The composite solder, terpineol and ethyl cellulose prepared in step 2 are uniformly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of the composite solder, terpineol and ethyl cellulose is 10:(0.2～2 ): (0.4～3), apply the composite solder paste between the conductive ceramic base material and the connecting surface of the corresponding connector after cleaning in step 1, to obtain the assembly to be welded; or prepare the composite solder paste The component to be welded is obtained by throwing the tape or extruding it into a foil and placing it between the corresponding connectors;

4. Vacuum brazing connection

Place the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 ~ 1×10 ^-3 Pa, and then raise the temperature of the vacuum brazing furnace to T ₁ at a rate of 15°C/min. And keep it warm for 5min~10min, then raise the temperature to the brazing temperature T2 at a speed of ₁₀ ℃/min, and keep it warm for 10min~20min, then cool down to 400℃ at a speed of 5~10℃/min, and finally cool with the furnace to complete Brazing connection of conductive ceramic-based materials; wherein T ₁ =T ₂ -(100°C-200°C), and T ₂ is 10%-30% higher than the liquidus temperature of the solder.

The preparation method described in this embodiment has the following advantages:

(1) Make full use of the conductive properties of conductive ceramic-based materials at the macro scale and introduce precision wire cutting technology to carry out secondary design and processing of various forms of surface structures on the connection surface, which can effectively slow down the ceramic/metal connection interface near the ceramic side. Stress concentration, and the process is simple, easy to operate, and low in cost;

(2) At the microscopic scale, TiB whiskers can be generated in situ near the brazing interface and in the brazing filler metal layer at the same time, and have the following effects at the same time:

a. Perform secondary processing on the connection interface at the microscopic level. The TiB whiskers distributed near the interface can increase the interface connection area at the microscopic scale and effectively slow down the stress concentration on the ceramic/metal connection interface near the ceramic side. The direction of residual stress can be reversed;

b. The material of the solder layer is modified, and the solder layer is changed from the original pure metal material to a metal-based TiB whisker-reinforced composite material, which effectively reduces the thermal expansion coefficient of the solder layer and reduces the residual stress;

c. The TiB whiskers generated in situ can effectively reverse the direction of the residual stress of the joint and reduce the probability of cracks.

(3) Through the combined effect of macroscale and microscale, the joint stress is relieved to the greatest extent, and the strength reliability of the joint is improved. The compressive shear strength of the conductive ceramic base material brazing joint obtained by the method is 155-265 MPa, which is 165%-345% higher than that of the conventional flat interface and no reinforcing phase brazing joint.

Embodiment 2: The difference between this embodiment and Embodiment 1 is that the corresponding connector is metal or conductive ceramic base material. Others are the same as in the first embodiment.

Embodiment 3: This embodiment differs from Embodiment 1 or Embodiment 2 in that: the conductive ceramic-based base material refers to a ceramic-based material with conductive properties to be connected to itself or a metal-based material. Others are the same as in the first or second embodiment. In this embodiment, the conductive ceramic-based base material is boride-based ceramics, carbide-based ceramics, conductive oxide-based ceramics or conductive nitride-based ceramics.

Embodiment 4: This embodiment is different from Embodiment 1 to Embodiment 3 in that: the metal is titanium alloy, niobium alloy or molybdenum alloy. Others are the same as those in the first to third specific embodiments.

Embodiment 5: This embodiment is different from Embodiment 1 to Embodiment 4 in that any two grooves in the tooth-shaped groove structure described in step 1 are parallel to each other or interlaced with each other. Others are the same as one of the specific embodiments 1 to 4.

Embodiment 6: This embodiment is different from Embodiment 1 to Embodiment 5 in that: the shape of the composite solder is powder, foil or sheet. Others are the same as one of the specific embodiments 1 to 5.

Embodiment 7: The difference between this embodiment and one of Embodiments 1 to 6 is that the B source in the composite solder described in step 2 is introduced into the active eutectic solder in the form of powder ball milling, or It is introduced into the active eutectic solder by means of multiple smelting, or introduced on the outer surface of the active eutectic solder by electroplating, magnetron sputtering or electron evaporation. Others are the same as one of the specific embodiments 1 to 6.

Embodiment 8: In this embodiment, a multi-scale joint method for improving the strength of a conductive ceramic-based material brazed joint is carried out according to the following steps:

1. Surface treatment of the connection surface of the conductive ceramic base material:

Process the connecting surface of the conductive ceramic base material into a tooth-shaped groove structure by wire cutting to obtain a surface-treated conductive ceramic base material. The groove depth is 0.3-3mm, the groove width is 0.3-3mm, and the distance between the two grooves The angle between the groove depth direction and the tangent direction of the surface to be connected is 90-150°; the corresponding connector and the surface-treated conductive ceramic base material are polished and cleaned, then cleaned with acetone and dried to obtain a clean The final conductive ceramic base material and corresponding connectors;

2. Preparation of brazing filler metal: Composite brazing filler metal includes B source and Ti-containing eutectic alloy system, in which the molar ratio of Ti element to B element is (10~1):1; B source is B, TiB ₂ , ZrB ₂ , HfB _2. A mixture of any one or several of HfB, BN and B ₄ C in any ratio, and the Ti-containing eutectic alloy system is Ti-Ni, Ti-Cu, Ag-Cu-Ti or Ti-Si; if If the B source is contained in the conductive ceramic base material or the corresponding connector, the B source is not added or the amount of B source is reduced; the volume content of TiB whiskers in the brazed joint of the final product is not less than 5%;

3. Placement of solder

The composite solder, terpineol and ethyl cellulose prepared in step 2 are uniformly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of the composite solder, terpineol and ethyl cellulose is 10:(0.2～2 ): (0.4～3), apply the composite solder paste between the conductive ceramic base material and the connecting surface of the corresponding connector after cleaning in step 1, to obtain the assembly to be welded; or prepare the composite solder paste The component to be welded is obtained by throwing the tape or extruding it into a foil and placing it between the corresponding connectors;

4. Vacuum brazing connection

Place the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 ~ 1×10 ^-3 Pa, and then raise the temperature of the vacuum brazing furnace to T ₁ at a rate of 15°C/min. And keep it warm for 5min~10min, then raise the temperature to the brazing temperature T2 at a speed of ₁₀ ℃/min, and keep it warm for 10min~20min, then cool down to 400℃ at a speed of 5~10℃/min, and finally cool with the furnace to complete Brazing connection of conductive ceramic-based materials; where T ₁ =T ₂ -(100°C-200°C), T ₂ is 10%-30% higher than the liquidus temperature of the solder; wherein the conductive ceramic-based base material and The thermal expansion coefficients of the corresponding connectors are equal.

Embodiment 9: This embodiment is different from Embodiment 8 in that: the corresponding connector is metal or conductive ceramic base material. Others are the same as the eighth embodiment.

Embodiment 10: This embodiment differs from Embodiment 8 or Embodiment 9 in that: the conductive ceramic-based base material refers to a ceramic-based material with conductive properties to be connected to itself or a metal-based material. Others are the same as the eighth or ninth embodiment. In this embodiment, the conductive ceramic-based base material is boride-based ceramics, carbide-based ceramics, conductive oxide-based ceramics or conductive nitride-based ceramics.

Embodiment 11: This embodiment is different from Embodiments 8 to 10 in that: the metal is titanium alloy, niobium alloy or molybdenum alloy. Others are the same as those in the eighth to tenth specific embodiments.

Embodiment 12: This embodiment is different from Embodiment 8 to Embodiment 11 in that: any two grooves in the tooth-shaped groove-shaped structure described in step 1 are parallel to or interlaced with each other. Others are the same as one of the eighth to eleventh specific embodiments.

Embodiment 13: This embodiment is different from Embodiments 8 to 12 in that: the form of the composite solder is powder, foil or sheet. Others are the same as Embodiments 8 to 12.

Embodiment 14: The difference between this embodiment and Embodiments 8 to 13 is that the B source in the composite solder described in step 2 is introduced into the active eutectic solder by powder ball milling, Or it is introduced into the active eutectic solder by means of multiple smelting, or it is introduced on the outer surface of the active eutectic solder by electroplating, magnetron sputtering or electron evaporation. Others are the same as Embodiments 8 to 13.

The following examples will further illustrate the present invention, but do not limit the present invention thereby.

Embodiment 1: In this embodiment, a multi-scale joint method for improving the strength of a conductive ceramic-based material brazed joint is carried out according to the following steps:

1. Surface treatment of the connection surface of the conductive ceramic base material:

a. Using precision wire cutting technology to process the connecting surface of the ZrC conductive ceramic base material and the corresponding connector Nb base material into a circular arc surface, wherein the surface of the ZrC base material is convex, and the surface of the corresponding connector Nb base material is concave, and The arc radius is equal to 20mm;

b. Process the connecting surface of the ZrC conductive ceramic base material processed in step a into a toothed groove structure by wire cutting, wherein the groove depth is 1.5mm, the groove width is 0.4mm, and the distance between the two grooves is 0.8mm. The angle between the depth direction and the tangent direction of the surface to be connected is 90°;

c. Grinding and cleaning the ZrC conductive ceramic base material after surface treatment in step b and the corresponding connector Nb base material after surface treatment in step a, then cleaning and drying with acetone to obtain the cleaned conductive ceramic base material and corresponding Connector;

2. Preparation of brazing filler metal: the composite brazing filler metal contains TiB ₂ and Ag-Cu-Ti eutectic alloy system. The specific preparation method is: respectively weigh Ag, Cu, TiB ₂ and TiH ₂ powders, and their mass percentages are respectively: 67% , 24%, 1.5%, 7.5%, using a ball mill to fully mix various solder powders to obtain a composite solder;

3. Placement of solder

The composite solder, terpineol and ethyl cellulose prepared in step 2 are evenly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of composite solder, terpineol and ethyl cellulose is 10:0.35:1, Coating the composite solder paste between the conductive ceramic base material cleaned in step 1 and the connecting surface of the corresponding connecting piece, the coating thickness is 200 μm, and the component to be welded is obtained;

4. Vacuum brazing connection

Put the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 Pa, then raise the temperature of the vacuum brazing furnace to 750°C at a rate of 15°C/min, and keep it warm for 10min, and then Raise the temperature at a rate of 10°C/min to a brazing temperature of 900°C, keep it warm for 20 minutes, then cool down to 400°C at a rate of 5°C/min, and finally cool down with the furnace to complete the brazing connection of the conductive ceramic base material.

The front view of the surface-treated ceramic-based ZrC base material in step 1 is shown in FIG. 1 , and the cross-sectional view is shown in FIG. 2 .

The assembly schematic diagram of the ZrC conductive ceramic base material/Nb metal base material joint after the brazing connection of the conductive ceramic base material in this embodiment is shown in FIG. 3 .

As a comparison, the brazing steps of the conventional flat interface and no reinforcing phase are as follows:

1. After grinding and cleaning the straight connection surfaces of the ZrC conductive ceramic base material and the Nb base material, thoroughly clean and dry them with acetone, and obtain the cleaned ceramic base material and corresponding connectors;

Two, take Ag, Cu, TiH ₂ powders by weighing respectively, and its mass percentage is respectively: 69.3%, 26.4%, 4.3%, use ball mill to carry out thorough mixing with various solder powders, obtain composite solder; Composite solder paste Coating between the conductive ceramic base material cleaned in step 1 and the connection surface of the corresponding connector, the coating thickness is 200 μm, and the component to be welded is obtained;

3. Put the parts to be welded in step 3 in a vacuum furnace, then raise the temperature of the vacuum brazing furnace to 750°C at a rate of 15°C/min, keep it warm for 10 minutes, and then heat up to brazing at a rate of 10°C/min The temperature is 900°C, and it is kept for 20 minutes, then the temperature is lowered to 400°C at a rate of 5°C/min, and finally cooled with the furnace, that is, the brazing connection of the conductive ceramic-based material is completed; the schematic diagram of the brazing joint assembly is shown in Figure 4.

The joint obtained by using the multi-scale joint method to improve the strength of the conductive ceramic-based material brazed joint, through the normal temperature static load compression shear test (loading rate is 0.5mm/s), the measured shear strength is 221MPa, while the conventional flat as a comparison The shear strength of the brazed joint with straight interface and no reinforcing phase is only 58MPa under the same test conditions, that is, the shear strength of the brazed joint obtained by the method of the present invention is increased by 283%.

Embodiment 2. In this embodiment, a multi-scale joint method for improving the strength of a conductive ceramic-based material brazed joint is carried out according to the following steps:

1. Surface treatment of the connection surface of the conductive ceramic base material:

a. Using precision wire cutting technology to process the connecting surface of the conductive ceramic base ZrC base material and the corresponding connector Nb base material into a circular arc surface, wherein the surface of the ZrC base material is convex, and the surface of the corresponding connector Nb base material is concave, and The radians are equal, and the arc radius is 15mm;

b. Process the connecting surface of the conductive ceramic base ZrC base material processed in step a into a toothed groove structure by wire cutting, wherein the groove depth is 1.5mm, the groove width is 0.4mm, and the distance between the two grooves is 0.8mm. The angle between the depth direction and the tangent direction of the surface to be connected is 90°;

c. Grinding and cleaning the ZrC conductive ceramic base material after surface treatment in step b and the corresponding connector Nb base material after surface treatment in step a, then cleaning and drying with acetone to obtain the cleaned conductive ceramic base material and corresponding Connector;

2. Preparation of solder: The composite solder contains TiB ₂ and Ag-Cu-Ti eutectic alloy system. The specific preparation method is: respectively weigh Ag, Cu, TiB ₂ and TiH ₂ powders, and their mass percentages are: 64.5% , 20%, 7.2%, 8.3%, using a ball mill to fully mix various solder powders to obtain a composite solder;

3. Placement of solder

The composite solder, terpineol and ethyl cellulose prepared in step 2 are evenly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of composite solder, terpineol and ethyl cellulose is 10:0.35:1, Coating the composite solder paste between the conductive ceramic base material cleaned in step 1 and the connecting surface of the corresponding connecting piece, the coating thickness is 200 μm, and the component to be welded is obtained;

4. Vacuum brazing connection

Put the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 Pa, then raise the temperature of the vacuum brazing furnace to 750°C at a rate of 15°C/min, and keep it warm for 10min, and then Raise the temperature at a rate of 10°C/min to a brazing temperature of 900°C, keep it warm for 20 minutes, then cool down to 400°C at a rate of 5°C/min, and finally cool down with the furnace to complete the brazing connection of the conductive ceramic base material.

As a comparison, the brazing steps of the conventional flat interface and no reinforcing phase are as follows:

1. After grinding and cleaning the straight connecting surfaces of the ZrC conductive ceramic base material and the Nb base material, thoroughly clean and dry them with acetone, and obtain the cleaned conductive ceramic base material and corresponding connectors;

Two, take Ag, Cu, TiH ₂ powders by weighing respectively, and its mass percentage is respectively: 69.3%, 26.4%, 4.3%, use ball mill to carry out thorough mixing with various solder powders, obtain composite solder; Composite solder paste Coating between the conductive ceramic base material cleaned in step 1 and the connection surface of the corresponding connector, the coating thickness is 200 μm, and the component to be welded is obtained;

3. Put the parts to be welded in step 3 in a vacuum furnace, then raise the temperature of the vacuum brazing furnace to 750°C at a rate of 15°C/min, keep it warm for 10 minutes, and then heat up to brazing at a rate of 10°C/min The temperature is 900°C, and it is kept for 20 minutes, then the temperature is lowered to 400°C at a rate of 5°C/min, and finally cooled with the furnace, that is, the brazing connection of the conductive ceramic base material is completed;

The joint obtained by using multi-scale combined method to improve the strength of the brazed joint of conductive ceramic-based materials has a shear strength of 258 MPa through the normal temperature static load compression shear test (loading rate is 0.5mm/s), while the conventional flat joint used as a comparison The shear strength of the brazed joint with straight interface and no reinforcing phase is only 58MPa under the same test conditions, that is, the shear strength of the brazed joint obtained by the method of the present invention is increased by 345%.

Embodiment 3: In this embodiment, a multi-scale joint method for improving the strength of a conductive ceramic-based material brazed joint is carried out according to the following steps:

1. Surface treatment of the connection surface of the conductive ceramic base material:

The connecting surface of the conductive ceramic-based ZrC base material is processed into a tooth-shaped groove structure by wire cutting, and the surface-treated conductive ceramic-based base material is obtained. The groove depth is 1.5mm, the groove width is 0.4mm, and the distance between the two grooves is 0.8mm, the angle between the depth direction of the groove and the tangent direction of the surface to be connected is 90°; the corresponding connector and the surface-treated conductive ceramic base material are polished and cleaned, then cleaned with acetone and dried to obtain the cleaned conductive ceramic Base material and corresponding connectors;

2. Preparation of brazing filler metal: the composite brazing filler metal contains TiB ₂ and Ag-Cu-Ti eutectic alloy system. The specific preparation method is: respectively weigh Ag, Cu, TiB ₂ and TiH ₂ powders, and their mass percentages are respectively: 67% , 24%, 1.5%, 7.5%, using a ball mill to fully mix various solder powders to obtain a composite solder;

3. Placement of solder

The composite solder, terpineol and ethyl cellulose prepared in step 2 are evenly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of composite solder, terpineol and ethyl cellulose is 10:0.35:1, Coating the composite solder paste between the conductive ceramic base material cleaned in step 1 and the connecting surface of the corresponding connecting piece, the coating thickness is 200 μm, and the component to be welded is obtained;

4. Vacuum brazing connection

Put the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 Pa, then raise the temperature of the vacuum brazing furnace to 750°C at a rate of 15°C/min, and keep it warm for 10min, and then Raise the temperature at a rate of 10°C/min to a brazing temperature of 900°C, keep it warm for 20 minutes, then cool down to 400°C at a rate of 5°C/min, and finally cool down with the furnace to complete the brazing connection of the conductive ceramic base material.

As a comparison, the brazing steps of the conventional flat interface and no reinforcing phase are as follows:

1. After polishing and cleaning the straight connecting surfaces of two ZrC conductive ceramic base materials, thoroughly clean them with acetone and dry them to obtain the cleaned conductive ceramic base materials;

Two, take Ag, Cu, TiH ₂ powders by weighing respectively, and its mass percentage is respectively: 69.3%, 26.4%, 4.3%, use ball mill to carry out thorough mixing with various solder powders, obtain composite solder; Composite solder paste Coating between the connecting surfaces of two conductive ceramic-based base materials cleaned in step 1, the coating thickness is 200 μm, and the component to be welded is obtained;

3. Put the parts to be welded in step 3 in a vacuum furnace, then raise the temperature of the vacuum brazing furnace to 750°C at a rate of 15°C/min, keep it warm for 10 minutes, and then heat up to brazing at a rate of 10°C/min The temperature is 900°C, and it is kept for 20 minutes, then the temperature is lowered to 400°C at a rate of 5°C/min, and finally cooled with the furnace, that is, the brazing connection of the conductive ceramic base material is completed;

The joint obtained by multi-scale combined method of improving the strength of the brazed joint of conductive ceramic-based materials, through the normal temperature static load compression shear test (loading rate is 0.5mm/s), the measured shear strength is 205MPa, while the conventional flat as a comparison The shear strength of the brazed joint with straight interface and no reinforcing phase is only 76MPa under the same test conditions, that is, the shear strength of the brazed joint obtained by the method of the present invention has increased by 171%

It can be seen from the above examples that the present invention alleviates the joint stress to the greatest extent and improves the strength and reliability of the joint through the joint action of the macro scale and the micro scale. The compressive shearing strength of the conductive ceramic base material brazing joint obtained by the method is 165-265 MPa, which is 165%-345% higher than that of the conventional flat interface and no reinforcing phase brazing joint.

Claims (10)

1. A multi-scale method for jointly improving the strength of conductive ceramic-based material brazed joints is characterized in that the method is carried out in the following steps: 1. Surface treatment of the connection surface of the conductive ceramic base material: a. Use precision wire cutting technology to process the connecting surface of the conductive ceramic base material and the corresponding connector into a circular arc surface. If the thermal expansion coefficient of the conductive ceramic base material is smaller than the thermal expansion coefficient of the corresponding connector, the conductive ceramic base material The surface is convex, and the surface of the corresponding connector is concave, and the radians are equal; if the thermal expansion coefficient of the conductive ceramic base material is greater than the thermal expansion coefficient of the corresponding connector, the surface of the conductive ceramic base material is concave, and the corresponding connector is convex. equal; b. Process the connecting surface of the conductive ceramic base material treated in step a into a tooth-shaped groove structure by wire cutting, wherein the groove depth is 0.3-3mm, the groove width is 0.3-3mm, and the distance between the two grooves is 0.3-2mm , the angle between the groove depth direction and the tangent direction of the surface to be connected is 90-150°; c. Grinding and cleaning the conductive ceramic base material after the surface treatment in step b and the corresponding connector after the surface treatment in step a, then cleaning and drying with acetone to obtain the cleaned conductive ceramic base material and corresponding connector; 2. Preparation of brazing filler metal: Composite brazing filler metal includes B source and Ti-containing eutectic alloy system, in which the molar ratio of Ti element to B element is (10~1):1; B source is B, TiB ₂ , ZrB ₂ , HfB _2. A mixture of any one or several of HfB, BN and B ₄ C in any ratio, and the Ti-containing eutectic alloy system is Ti-Ni, Ti-Cu, Ag-Cu-Ti or Ti-Si; if If the B source is contained in the conductive ceramic base material or the corresponding connector, the B source is not added or the amount of B source is reduced; the volume content of TiB whiskers in the brazed joint of the final product is not less than 5%; 3. Placement of solder The composite solder, terpineol and ethyl cellulose prepared in step 2 are uniformly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of the composite solder, terpineol and ethyl cellulose is 10:(0.2～2 ): (0.4～3), apply the composite solder paste between the conductive ceramic base material and the connecting surface of the corresponding connector after cleaning in step 1, to obtain the assembly to be welded; or prepare the composite solder paste The component to be welded is obtained by throwing the tape or extruding it into a foil and placing it between the corresponding connectors; 4. Vacuum brazing connection Place the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 ~ 1×10 ^-3 Pa, and then raise the temperature of the vacuum brazing furnace to T ₁ at a rate of 15°C/min. And keep it warm for 5min~10min, then raise the temperature to the brazing temperature T2 at a speed of ₁₀ ℃/min, and keep it warm for 10min~20min, then cool down to 400℃ at a speed of 5~10℃/min, and finally cool with the furnace to complete Brazing connection of conductive ceramic-based materials; wherein T ₁ =T ₂ -(100°C-200°C), and T ₂ is 10%-30% higher than the liquidus temperature of the solder. 2. A multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints according to claim 1, characterized in that said corresponding connectors are metals or conductive ceramic-based base materials. 3. according to claim 1 or 2, a kind of multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints is characterized in that said conductive ceramic-based base material refers to a metal-based material that is connected to itself or has a Ceramic-based materials with conductive properties. 4. A multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints according to claim 2, characterized in that said metal is titanium alloy, niobium alloy or molybdenum alloy. 5. A method of multi-scale joint improvement of the strength of conductive ceramic-based material brazed joints according to claim 1, characterized in that any two grooves in the tooth-shaped groove structure described in step 1 are parallel to each other or mutually staggered. 6. A multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints according to claim 1, characterized in that the shape of the composite solder is powder, foil or flake. 7. A kind of multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints according to claim 1, characterized in that the B source in the composite solder described in step 2 is introduced in the form of powder ball milling into the active eutectic solder, or introduced into the active eutectic solder by multiple smelting, or introduced into the outer surface of the active eutectic solder by electroplating, magnetron sputtering or electronic evaporation. 8. A method for multi-scale joint improvement of the strength of conductive ceramic-based material brazed joints, characterized in that the method is carried out in the following steps: 1. Surface treatment of the connection surface of the conductive ceramic base material: Process the tooth-shaped groove structure on the connecting surface of the conductive ceramic base material by wire cutting to obtain a surface-treated conductive ceramic base material, in which the groove depth is 0.3-3mm, the groove width is 0.3-3mm, and the distance between the two grooves The angle between the groove depth direction and the tangent direction of the surface to be connected is 90-150°; the corresponding connector and the surface-treated conductive ceramic base material are polished and cleaned, then cleaned with acetone and dried to obtain a clean The final conductive ceramic base material and corresponding connectors; 2. Preparation of brazing filler metal: Composite brazing filler metal includes B source and Ti-containing eutectic alloy system, in which the molar ratio of Ti element to B element is (10~1):1; B source is B, TiB ₂ , ZrB ₂ , HfB _2. A mixture of any one or several of HfB, BN and B ₄ C in any ratio, and the Ti-containing eutectic alloy system is Ti-Ni, Ti-Cu, Ag-Cu-Ti or Ti-Si; if If the B source is contained in the conductive ceramic base material or the corresponding connector, the B source is not added or the amount of B source is reduced; the volume content of TiB whiskers in the brazed joint of the final product is not less than 5%; 3. Placement of solder The composite solder, terpineol and ethyl cellulose prepared in step 2 are uniformly stirred into a paste to obtain a composite solder paste, wherein the mass ratio of the composite solder, terpineol and ethyl cellulose is 10:(0.2～2 ): (0.4～3), apply the composite solder paste between the conductive ceramic base material and the connecting surface of the corresponding connector after cleaning in step 1, to obtain the assembly to be welded; or prepare the composite solder paste The component to be welded is obtained by throwing the tape or extruding it into a foil and placing it between the corresponding connectors; 4. Vacuum brazing connection Place the components to be welded in a vacuum furnace, evacuate the vacuum brazing furnace to 5×10 ^-4 ~ 1×10 ^-3 Pa, and then raise the temperature of the vacuum brazing furnace to T ₁ at a rate of 15°C/min. And keep it warm for 5min~10min, then raise the temperature to the brazing temperature T2 at a speed of ₁₀ ℃/min, and keep it warm for 10min~20min, then cool down to 400℃ at a speed of 5~10℃/min, and finally cool with the furnace to complete Brazing connection of conductive ceramic-based materials; where T ₁ =T ₂ -(100°C-200°C), T ₂ is 10%-30% higher than the liquidus temperature of the solder; wherein the conductive ceramic-based base material and The thermal expansion coefficients of the corresponding connectors are equal. 9. A multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints according to claim 8, wherein the corresponding connector is a metal or a conductive ceramic-based base material; wherein the conductive ceramic-based base material Refers to a ceramic-based material with conductive properties that is connected to itself or a metal-based material. 10. A multi-scale joint method for improving the strength of conductive ceramic-based material brazed joints according to claim 9, characterized in that said metal is titanium alloy, niobium alloy or molybdenum alloy.