A method for joining ceramics and Nb using a composite interlayer

Abstract

The present application relates to the field of vacuum brazing, and more particularly to a method for connecting ceramics and Nb using a composite interlayer. The method comprises: pouring a certain proportion of Sn and Zr powders into a clean ball mill tank, adding agate balls for milling; preparing a nano-carbon / Ni composite material; placing the nano-carbon / Ni composite material described in S4 in a ferric chloride solution for corrosion for a period of time; cutting the corroded nano-carbon / Ni composite material into a shape required for the welding site after air drying; cutting a Ti foil into a shape required for the welding site; placing the ceramic to be welded in a nickel crucible and performing thermal etching; cleaning the ceramic to be welded and the Nb to be welded after thermal etching; mixing the Sn-Zr powders into a paste using a binder and uniformly coating the polished surface of the ceramic to be welded; assembling in the order of Nb-Ti foil-nano-carbon / Ni composite material-Ti foil-ceramic to be welded to obtain an assembled part, and loading the part into a graphite mold for vacuum brazing.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vacuum brazing, in particular to a method for connecting ceramic and Nb using a composite interlayer. BACKGROUND

[0002] Ceramic materials are widely used in high-temperature structural materials due to their high strength, high hardness, and high-temperature resistance. Currently, vacuum brazing is used to connect ceramic materials and Nb. However, there are two problems: first, the conventional low-melting-point filler cannot be used for instantaneous liquid-phase connection because the parts need to be used at high temperatures; second, the expansion coefficients of ceramic and Nb differ greatly, resulting in large residual stress in the joint after welding, which causes welding cracks on the ceramic side. SUMMARY

[0003] The present application provides a method for connecting ceramic and Nb using a composite interlayer, which ensures the density of the welded joint interface and the high-temperature use performance and mechanical properties of the parts.

[0004] The technical solution of the present application is as follows:

[0005] To achieve the above-mentioned purpose, a method for connecting ceramic and Nb using a composite interlayer is provided, characterized by comprising the following steps:

[0006] Pour a certain proportion of Sn and Zr powder into a clean ball mill jar, add agate balls, and mill at a ball-to-material ratio of 10:1. After completion, dry the Sn-Zr powder;

[0007] Prepare a nano-carbon / Ni composite material;

[0008] Prepare a certain mass fraction of ferric chloride solution, and place the nano-carbon / Ni composite material in the ferric chloride solution for a period of time;

[0009] After corrosion, cut the nano-carbon / Ni composite material into the required shape for welding, and polish it to a certain thickness with sandpaper;

[0010] Cut the Ti foil into the required shape for welding, and polish it to a certain thickness with sandpaper;

[0011] Use diamond abrasive to polish the surface of the ceramic to be welded, and place the ceramic to be welded in a nickel crucible for thermal etching;

[0012] Clean the ceramic to be welded and the Nb to be welded after thermal etching;

[0013] Mix the Sn-Zr powder with a binder into a paste and evenly apply it to the polished surface of the ceramic to be welded;

[0014] Assemble in the order of Nb-Ti foil-nanocarbon / Ni composite material-Ti foil-to-be-welded ceramic, obtain the assembled part, and put the part into a graphite mold to perform vacuum brazing.

[0015] In one possible embodiment, the nanocarbon / Ni composite material is prepared, including:

[0016] A certain proportion of Ni powder and sucrose is accurately weighed by using an electronic balance, and the weighing process is ensured to be clean and pollution-free;

[0017] The weighed Ni powder and sucrose are placed into a beaker, 40 ml of deionized water and 20 ml of alcohol are added, the sucrose is completely dissolved, a magnetic stirrer is used to heat and stir at a certain temperature until the water and alcohol are completely evaporated, and the two raw materials are fully mixed to form a powder;

[0018] The powder is placed in a graphite mold, the mold is placed in a hot-pressing furnace as a whole, and heating is performed according to a specified heating mode to obtain the nanocarbon / Ni composite material.

[0019] In one possible embodiment, the mass ratio of Sn and Zr powder is 92:8;

[0020] In one possible embodiment, the used Ni powder is 5 μm, and the mass ratio of Ni powder and sucrose is 95:5;

[0021] In one possible embodiment, the temperature of heating and stirring is 60℃;

[0022] In one possible embodiment, the specified heating mode is to apply a pressure of 50 MPa, to rise to 820℃ at a temperature rising rate of 60℃ / min under the protection of Ar gas, and to keep the temperature for 30 min, and then to cool to room temperature following the furnace;

[0023] In one possible embodiment, the mass fraction of the ferric chloride solution is 10%, and the corrosion time is 8 min to 10 min;

[0024] In one possible embodiment, the thickness of the nanocarbon / Ni composite material is 500 μm;

[0025] In one possible embodiment, the thickness of the Ti foil is 50 μm;

[0026] In one possible embodiment, the specified heating mode is to rise to 450℃ at a temperature rising rate of 60℃ / min, and to keep the temperature for 30 min, and then to cool to room temperature following the furnace;

[0027] In one possible embodiment, the concentration of the NaOH aqueous solution is 5 mol / L, and the soaking time of the NaOH aqueous solution is 30 min;

[0028] In a possible embodiment, the concentration of the HF aqueous solution is 6 mol / L, and the HF aqueous solution and deionized water are used for cleaning at least twice;

[0029] In a possible embodiment, the ultrasonic cleaning solvent used is acetone, the frequency of cleaning is 20 KHZ-30 KHZ, and the time is 15 min-20 min;

[0030] In a possible embodiment, the thickness of the Sn-Zr paste solder is 50 mu m;

[0031] In a possible embodiment, the assembly sequence needs to be in the order of Nb-Ti foil-nanocarbon / Ni composite material-Ti foil-ceramic to be welded.

[0032] In a possible embodiment, the graphite block placed on the part is 1.5 kg;

[0033] In a possible embodiment, the specific process of the specified heating mode in the vacuum brazing furnace is as follows:

[0034] Heating at a rate of 15 DEG C / min to 300 DEG C, and keeping for 5 min after reaching 400 DEG C;

[0035] Heating at a rate of 12 DEG C / min to 650 DEG C, and keeping for 10 min after reaching 650 DEG C;

[0036] Heating at a rate of 5 DEG C / min to 990 DEG C, and keeping for 10 min after reaching 990 DEG C.

[0037] After the part is cooled to 300 DEG C with the vacuum brazing furnace, air cooling is performed to 80 DEG C.

[0038] In a possible embodiment, the ceramic to be welded can be Cf / SiC, TiSiC and SiC ceramic.

[0039] The advantages of the present application are:

[0040] The technical key of the present application is to modify and metallize the ceramic surface by combining the Sn-Zr solder and hot etching method, which is convenient for subsequent brazing wet spreading.

[0041] And in order to better improve the performance of the welded joint, Ni and Ti are not directly added in the Sn-Zr system, but the process method of preparing nanocarbon / Ni composite material and Ti foil is adopted. The addition of the intermediate layer not only can be used as a low expansion transition layer to reduce the problem of excessive stress caused by the large difference in expansion coefficient between Nb and ceramic during the welding process. It can also form nanoscale TiC particles to enhance the mechanical properties of the welded joint, and the ceramic surface after hot etching can better increase the strengthening effect of TiC particles. Attached Figure Description

[0042] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0043] To further illustrate the invention in detail, the following description is provided in conjunction with the accompanying drawings.

[0044] This invention provides a method for connecting ceramics and Nb using a composite interlayer, such as... Figure 1 As shown, it includes:

[0045] S1: Add Sn and Zr powders to a clean ball mill jar at a mass ratio of 92:8. Adding Zr can improve the wettability of the brazing filler metal to ceramics, but excessive Zr content will change the content of intermetallic compounds, alter the viscosity of the melt, and affect the surface tension of the melt. A mass ratio of Sn to Zr powder of 92:8 yields the best results. Add agate balls at a ball-to-powder ratio of 10:1, pour in an appropriate amount of acetone, seal the ball mill jar, and place it in a ball mill at a speed of 150 r / min for 10 hours. After the process, dry the powder.

[0046] S2: Accurately weigh Ni powder and sucrose in a 95:5 mass ratio using an electronic balance. When the sucrose mass fraction is 5%, the prepared nano-carbon can form a three-dimensional network, which can better improve the fluidity of the solder layer. Ensure a clean and uncontaminated experimental environment during the weighing process.

[0047] S3: Place the weighed Ni powder and sucrose from S2 into a beaker, add 40ml of deionized water and 20ml of alcohol to completely dissolve the sucrose, and use a magnetic stirrer to heat and stir at 60°C for about 6 hours until the water and alcohol are completely evaporated, so that the two raw materials are fully mixed to form powder.

[0048] S4: Place the powder described in S3 into a graphite mold, place the entire mold in a hot press furnace, and heat it according to the following specified heating method:

[0049] A pressure of 50 MPa was applied, and under Ar gas protection, the temperature was increased to 820 °C at a heating rate of 60 °C / min and held for 30 min, then cooled to room temperature in the furnace. This yielded a nano-carbon / Ni composite material.

[0050] S5: Prepare a ferric chloride solution with a certain mass fraction, and place the nano-carbon / Ni composite material described in S4 into a ferric chloride solution with a mass fraction of 10% for corrosion for 8 min to 10 min;

[0051] S6: Cut the nano-carbon / Ni composite material described in S5 into the required shape for the welding area, and polish it to 500μm with sandpaper;

[0052] S7: Cut the Ti foil into the required shape for the welding site and polish it to 50 μm with sandpaper. Using Ti can change the melt composition with three-dimensional reticular nanocarbon / Ni to form TiC to improve the strength of the welded joint;

[0053] S8: Polish the ceramic surface to be welded using diamond abrasive, place the ceramic to be welded in a nickel crucible, add an appropriate amount of etchant, and heat the ceramic according to the following heating method:

[0054] Rise to 450°C at a rate of 60°C / min and hold for 30 min, then cool to room temperature in the furnace. Heat corrosion can modify the ceramic surface, on the one hand to improve the wettability of the Sn-Zr system, and on the other hand to improve the effect of the nanocarbon / Ni composite-Ti low-expansion solder system. The process parameters of heat corrosion have a great influence on the corrosion depth;

[0055] S9: Soak the ceramic to be welded after heat corrosion as described in S8 in a 5 mol / L NaOH aqueous solution for 30 min, and then clean it at least twice with a 6 mol / L HF aqueous solution and deionized water;

[0056] S10: Polish the Nb to be welded using 1500# sandpaper, and clean the ceramic to be welded after cleaning as described in S9 using ultrasonic cleaning. The ultrasonic cleaning solvent used is acetone, the cleaning frequency is 20 KHZ-30 KHZ, and the time is 15 min-20 min;

[0057] S11: Mix the Sn-Zr powder described in S1 with a binder into a paste and evenly apply it to the surface of the ceramic to be welded described in S10. The thickness of the Sn-Zr paste soldering is 50 μm;

[0058] S12: Assemble the Ti foil described in S7, the nanocarbon / Ni composite material described in S5, the Nb to be welded described in S10, and the ceramic to be welded described in S11 in the order of Nb-Ti foil-nanocarbon / Ni composite material-Ti foil-ceramic to be welded, and place the assembled parts into a graphite mold. Place a 1.5 kg graphite weight on the parts to balance the weight;

[0059] S13: Vacuumize the vacuum brazing furnace until the vacuum degree reaches ≤1×10 -4 Pa;

[0060] S14: Weld the parts in the vacuum brazing furnace according to the specified heating method. The specified heating method is as follows:

[0061] The specific process is as follows:

[0062] Heated at a rate of 15°C / min to 300°C, held for 5 min at 400°C after reaching 400°C;

[0063] Heated at a rate of 12°C / min to 650°C, held for 10 min at 650°C after reaching 650°C;

[0064] Heated at a rate of 5°C / min to 990°C, held for 10 min at 990°C after reaching 990°C.

[0065] After the parts are cooled to 300°C with the vacuum brazing furnace, air cooling is performed to 80°C. This welding schedule ensures the density of the welded joint while maintaining the performance of the parts.

Claims

1. A method for joining ceramics and Nb using a composite interlayer, characterized by, The application relates to a Sn-Zr-Nb-Ti ceramic brazing method. Sn and Zr powders are poured into a clean ball mill tank according to a mass ratio of 92:8, and agate balls are added for ball milling, and the ball-to-material ratio is 10:1; after the ball milling is completed, the Sn-Zr powders are dried; The nano-carbon / Ni composite material is prepared; A certain mass fraction of iron chloride solution is prepared, and the nano-carbon / Ni composite material is placed in the iron chloride solution for corrosion for a period of time; After the corrosion, the nano-carbon / Ni composite material is cut into a shape required by a welding position and is polished to a certain thickness by using sandpaper; Ti foils are cut into a shape required by a welding position and are polished to a certain thickness by using sandpaper; The surface of the ceramic to be welded is polished by using diamond abrasive, the ceramic to be welded is placed in a nickel crucible, and hot corrosion is carried out; The ceramic to be welded after the hot corrosion and the Nb to be welded are cleaned; The Sn-Zr powders are mixed into a paste by using a binder, and the paste is uniformly coated on the polished surface of the ceramic to be welded; The Nb-Ti foil-nano-carbon / Ni composite material-Ti foil-ceramic to be welded are assembled in sequence to obtain an assembled part, and the part is loaded into a graphite mold for vacuum brazing.

2. The method of claim 1, wherein, The nano-carbon / Ni composite material is prepared by the following steps: A certain proportion of Ni powder and sucrose is accurately weighed by using an electronic balance, and the weighing process is carried out in a clean and pollution-free environment; The weighed Ni powder and sucrose are placed into a beaker, 40 ml of deionized water and 20 ml of alcohol are added, the sucrose is completely dissolved, a magnetic stirrer is used to heat and stir at a certain temperature until the water and alcohol are completely evaporated, and the two raw materials are fully mixed to form a powder; The powder is placed in a graphite mold, the whole mold is placed in a hot pressing furnace, and heating is carried out according to a specified heating mode to obtain the nano-carbon / Ni composite material.

3. The method of claim 2, wherein, The granularity of the Ni powder is 5 mu m, the mass ratio of the Ni powder to the sucrose is 95:5, and the temperature for heating and stirring is 60 DEG C. The specified heating mode for preparing the nano-carbon / Ni composite material is as follows: a pressure of 50 MPa is applied, the temperature is increased to 820 DEG C at a rate of 60 DEG C / min under the protection of Ar gas, and the temperature is kept for 30 min, and then the furnace is cooled to room temperature.

4. The method of claim 1, wherein, The mass fraction of the iron chloride solution is 10%, and the corrosion time is 8 min to 10 min; and the thickness of the nano-carbon / Ni composite material is 500 mu m.

5. The method of claim 1, wherein, The specified heating mode for the hot corrosion is as follows: the temperature is increased to 450 DEG C at a rate of 60 DEG C / min, and the temperature is kept for 30 min, and then the furnace is cooled to room temperature.

6. The method of claim 1, wherein, The thickness of the Sn-Zr paste brazing filler metal is 50 mu m.

7. The method of claim 1, wherein, The specified heating mode for the vacuum brazing is as follows: The temperature is increased to 300 DEG C at a rate of 15 DEG C / min, and the temperature is kept for 5 min after reaching 400 DEG C; The temperature is increased to 650 DEG C at a rate of 12 DEG C / min, and the temperature is kept for 10 min after reaching 650 DEG C; The temperature is increased to 990 DEG C at a rate of 5 DEG C / min, and the temperature is kept for 10 min after reaching 990 DEG C; After the part is cooled to 300 DEG C with the vacuum brazing furnace, the part is air-cooled to 80 DEG C.

Images