CN113020735B - Preparation method of silicon nitride ceramic/stainless steel braze welding joint with corrosion resistance and stress relief - Google Patents

Abstract

A preparation method of a silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief relates to a preparation method of a silicon nitride ceramic/stainless steel brazing joint. The invention is to solve the problem that the existing silicon nitride ceramics and active metals of metals are brazed due to the excessive expansion coefficient of the brazing filler metal and the metal base material itself, which causes the silicon nitride ceramics to be cracked due to the large residual stress, and the brazing The technical problem that the material itself is not resistant to corrosion. The invention intends to develop a composite brazing filler metal layer suitable for connecting silicon nitride ceramics and 316L stainless steel on the basis of the brazing filler metals AgCuTi and AgCu. The formation of Ag-based solid solution can reduce the residual stress of the joint and improve the overall corrosion resistance of the joint. After corrosion, there are no large holes in the entire weld area, and the overall joint shows better corrosion resistance.

Description

A preparation method of silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief

technical field

The invention relates to a preparation method of a silicon nitride ceramic/stainless steel brazing joint.

Background technique

Silicon nitride ceramics (Si ₃ N ₄ ) are high-temperature ceramics with high strength, high hardness, wear resistance, oxidation resistance and self-lubricating properties. Si ₃ N ₄ has excellent corrosion resistance, such as acid resistance, molten salt corrosion, etc., so it can be used in harsh corrosive environments. However, due to the brittleness of Si ₃ N ₄ ceramic itself, its development is limited, while metal materials have excellent room temperature strength and ductility. If the two materials can be combined to manufacture complex components that meet the requirements, it will make Si A major breakthrough has been made in the application of ₃ N ₄ ceramics, and scholars at home and abroad have conducted extensive research and discussion on this. 316L stainless steel (022Cr17Ni12Mo2) is a derivative of 18-8 type austenitic stainless steel. It is added with 2% to 3% Mo element. Because of its excellent corrosion resistance, it is widely used in the chemical industry. This steel has excellent resistance to pitting corrosion and can be safely used in environments containing ^Cl- and other halogen ions, and is a commonly used material in marine environments. Since 316L stainless steel has good machinability, if the connection between Si ₃ N ₄ ceramics and 316L stainless steel is realized, the advantages of the two can be fully utilized, and a reliable composite component can be made, which can greatly expand the application of the two, especially is for use in marine environmental conditions. Therefore, the Si ₃ N ₄ /316L composite component is expected to replace the pure 316L stainless steel component, improve the service life of the component and reduce the production cost.

The connection between silicon nitride ceramics and metal includes active metal brazing, transient liquid phase connection, diffusion welding, oxide glass connection and oxynitride glass connection. The current research results show that active metal brazing is the most commonly used method. The brazing filler metals Ag69Cu28Ti3 (wt.%) and Ag28Cu (wt.%) are two common commercial brazing filler metals. And the expansion coefficient of the metal base metal itself is too large, which causes the silicon nitride ceramic to crack due to the large residual stress, and the brazing material itself is not corrosion-resistant. For this reason, it is necessary to develop a composite solder layer suitable for ceramic and metal connections.

SUMMARY OF THE INVENTION

The invention is to solve the problem that the existing silicon nitride ceramics and active metals of metals are brazed due to the excessive expansion coefficient of the brazing filler metal and the metal base material itself, which causes the silicon nitride ceramics to be cracked due to the large residual stress, and the brazing In order to solve the technical problem that the material itself is not corrosion-resistant, a preparation method of a silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief is provided.

The preparation method of the silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief of the present invention is as follows:

1. Grind the surface to be welded of the base metal Si ₃ N ₄ ceramic with 300# metallographic sandpaper, 600# metallographic sandpaper and 1000# metallographic sandpaper in turn to smoothness, ultrasonically vibrate in acetone for 3min-5min, and then put it in an oven medium drying;

2. Grind the base material 316L stainless steel with 600#SiC sandpaper and #1000SiC sandpaper in turn to remove the surface oxide layer, then use 800# metallographic sandpaper and 1000# metallographic sandpaper in turn to polish until bright, and then clean with ultrasonic vibration in acetone for 3min ~5min, and finally put the material into the oven to dry;

Repeat the above operations in step 2 for X metal foil, Ag foil, solder AgCuTi and solder AgCu respectively; X in the X metal foil is Mo, W, Cr or Nb;

3. Assemble the dried materials in steps 1 and 2 according to the structure of the base material 316L stainless steel/AgCu/Ag/X/Ag/AgCuTi/base material Si ₃ N ₄ ceramics. When assembling, every two layers of Use organic glue for bonding, and leave it naturally until the organic glue solidifies;

4. Put the joint prepared in step 3 into a graphite grinding tool, the base material Si ₃ N ₄ ceramic is located above, and a graphite block is placed on the upper surface of the base material Si ₃ N ₄ ceramic for physical pressure;

5. Put the graphite mold in step 4 into the vacuum brazing furnace, evacuate until the vacuum degree is kept above 6×10 ^-6 Pa, and then raise the temperature to 300℃～350℃ within 45min～50min and keep it stable for 20min～25min , then heat up to the brazing temperature at 7.5℃/min～8℃/min and keep it for 10min～15min, and finally reduce it to 280℃～300℃ at 5℃/min～6℃/min, and cool with the furnace to complete the connection;

The brazing temperature is 900°C to 950°C.

The invention intends to develop a composite brazing filler metal layer suitable for connecting silicon nitride ceramics and 316L stainless steel on the basis of the brazing filler metals AgCuTi and AgCu. The formation of Ag-based solid solution can reduce the residual stress of the joint and improve the overall corrosion resistance of the joint.

X metal foil takes Mo foil as an example. The thickness of Mo foil should be adjusted according to the size of different weldments. The residual stress on the ceramic side decreases with the increase of the thickness of the Mo foil (the relationship between the residual stress on the ceramic side and the thickness of other metals as the intermediate layer should be simulated by finite element, and the thickness is selected).

Description of drawings

Figure 1 is a schematic diagram of the assembly of the joint prepared in step 3 of test 1, 1 is Si ₃ N ₄ ceramics, 2 is the solder AgCuTi, 3 is the Ag foil, 4 is the Mo foil, 5 is the solder AgCu, 6 is the 316L Stainless steel;

Fig. 2 is the SEM image of the joint prepared in step 5 of test one;

Fig. 3 is the SEM image after corrosion of the joint prepared in step 5 of test 1;

Figure 4 shows the residual stress simulation cloud diagram of the traditional AgCuTi as the brazing material, brazing Si ₃ N ₄ and 316L stainless steel joints;

Fig. 5 is a simulation cloud diagram of residual stress of the joint prepared in step 5 of test 1.

Detailed ways

Embodiment 1: This embodiment is a preparation method of a silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief, and the specific process is as follows:

1. Grind the surface to be welded of the base metal Si ₃ N ₄ ceramic with 300# metallographic sandpaper, 600# metallographic sandpaper and 1000# metallographic sandpaper in turn to smoothness, ultrasonically vibrate in acetone for 3min-5min, and then put it in an oven medium drying;

2. Grind the base material 316L stainless steel with 600#SiC sandpaper and #1000SiC sandpaper in turn to remove the surface oxide layer, then use 800# metallographic sandpaper and 1000# metallographic sandpaper in turn to polish until bright, and then clean with ultrasonic vibration in acetone for 3min ~5min, and finally put the material into the oven to dry;

Repeat the above operations in step 2 for X metal foil, Ag foil, solder AgCuTi and solder AgCu respectively; X in the X metal foil is Mo, W, Cr or Nb;

3. Assemble the dried materials in steps 1 and 2 according to the structure of the base material 316L stainless steel/AgCu/Ag/X/Ag/AgCuTi/base material Si ₃ N ₄ ceramics. When assembling, every two layers of Use organic glue for bonding, and leave it naturally until the organic glue solidifies;

4. Put the joint prepared in step 3 into the graphite grinding tool, the base material Si ₃ N ₄ ceramic is located above, and place a graphite block on the upper surface of the base material Si ₃ N ₄ ceramic for physical pressure;

5. Put the graphite mold in step 4 into the vacuum brazing furnace, evacuate until the vacuum degree is kept above 6×10 ^-6 Pa, and then raise the temperature to 300℃～350℃ within 45min～50min and keep it stable for 20min～25min , then heat up to the brazing temperature at 7.5℃/min～8℃/min and keep it for 10min～15min, and finally reduce it to 280℃～300℃ at 5℃/min～6℃/min, and cool with the furnace to complete the connection;

The brazing temperature is 900°C to 950°C.

Embodiment 2: The difference between this embodiment and Embodiment 1 is that the ultrasonic oscillation described in step 1 is performed in an ultrasonic oscillator. Others are the same as the first embodiment.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the frequency of the ultrasonic oscillation described in step 1 is 40KHz. Others are the same as in the first or second embodiment.

Embodiment 4: The difference between this embodiment and one of Embodiments 1 to 3 is that the drying described in step 1 is drying at 80° C. for 2 hours. Others are the same as one of Embodiments 1 to 3.

Embodiment 5: This embodiment is different from Embodiment 4 in that the ultrasonic oscillation described in step 2 is performed in an ultrasonic oscillator. Others are the same as the fourth embodiment.

Embodiment 6: This embodiment is different from Embodiment 4 in that the frequency of the ultrasonic oscillation described in step 2 is 40KHz. Others are the same as the fourth embodiment.

Embodiment 7: This embodiment is different from Embodiment 4 in that the drying described in step 2 is drying at 80° C. for 2 hours. Others are the same as the fourth embodiment.

Embodiment 8: This embodiment is different from Embodiment 4 in that the brazing filler metal AgCuTi described in step 2 is Ag69Cu28Ti3 (wt.%). Others are the same as the fourth embodiment.

Embodiment 9: The difference between this embodiment and Embodiment 4 is that the brazing filler metal AgCu described in step 2 is Ag28Cu (wt.%). Others are the same as the fourth embodiment.

Embodiment 10: The difference between this embodiment and the fourth embodiment is that the organic glue described in step 3 is 502 glue. Others are the same as the fourth embodiment.

Embodiment 11: The difference between this embodiment and Embodiment 4 is that: in Step 5, the graphite mold of Step 4 is placed in a vacuum brazing furnace, and the vacuum is evacuated until the degree of vacuum is kept above 6×10 ^-6 Pa, Then it was heated up to 300°C within 45min and kept stable for 20min, then heated up to the brazing temperature at 7.5°C/min and kept for 10min, finally lowered to 300°C at 5°C/min, and cooled with the furnace to complete the connection. Others are the same as in the fourth embodiment.

Embodiment 12: The difference between this embodiment and Embodiment 4 is that when the brazing temperature in Step 5 is 950°C, the thickness of the solder AgCuTi and AgCu described in Step 2 are both 100 μm, and the thickness of the Ag foil is 100 μm. The thickness of the sheet was 2031.11 μm, and the thickness of the X metal foil was 100 μm to 500 μm. Others are the same as the fourth embodiment.

Embodiment 13: The difference between this embodiment and Embodiment 4 is that when the brazing temperature in step 5 is 900°C, the thickness of the solder AgCuTi and AgCu described in step 2 are both 100 μm, and the thickness of the Ag foil is 100 μm. The thickness of the sheet is 305.47 μm, and the thickness of the X metal foil is 100 μm to 500 μm. Others are the same as the fourth embodiment.

The present invention was verified with the following experiments:

Test 1: This test is a preparation method of a silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief. The specific process is as follows:

1. The surface to be welded of the base metal Si ₃ N ₄ ceramic is polished to smooth with 300# metallographic sandpaper, 600# metallographic sandpaper and 1000# metallographic sandpaper in turn, ultrasonically oscillated in acetone for 3 minutes, and then placed in an oven to dry Drying; the ultrasonic vibration described in the step 1 is carried out in an ultrasonic oscillator; the frequency of the ultrasonic vibration described in the step 1 is 40KHz; the drying described in the step 1 is drying at 80 ℃ for 2h;

2. Grind the base material 316L stainless steel with 600#SiC sandpaper and #1000SiC sandpaper in turn to remove the surface oxide layer, then use 800# metallographic sandpaper and 1000# metallographic sandpaper in turn to polish until bright, and then clean with ultrasonic vibration in acetone for 3min , and finally put the material into an oven for drying; the ultrasonic oscillation described in the step 2 is carried out in an ultrasonic oscillator; the frequency of the ultrasonic oscillation described in the step 2 is 40KHz; the drying described in the step 2 is performed at Dry at 80°C for 2 hours; the brazing filler metal AgCuTi described in the second step is Ag69Cu28Ti3 (wt.%); the brazing filler metal AgCu described in the second step is Ag28Cu (wt.%); the brazing filler metal AgCuTi and the brazing filler metal described in the second step The thickness of AgCu is 100 μm, the thickness of Ag foil is 305.47 μm, and the thickness of Mo foil is 500 μm;

Repeat the above operations in step 2 for Mo foil, Ag foil, solder AgCuTi and solder AgCu respectively;

3. Assemble the dried materials in steps 1 and 2 according to the structure of base material 316L stainless steel/AgCu/Ag/Mo/Ag/AgCuTi/base material Si ₃ N ₄ ceramics. When assembling, for the purpose of solder layer The assembly is stable, each two layers are bonded with 502 glue, and they are naturally placed until the 502 glue solidifies;

4. Put the joint prepared in step 3 into the graphite grinding tool, the base material Si ₃ N ₄ ceramic is located above, and place a graphite block on the upper surface of the base material Si ₃ N ₄ ceramic for physical pressure to avoid the metal The solder melts and the base metal is removed from its original position, which greatly reduces the welding effect;

5. Put the graphite mold in step 4 into the vacuum brazing furnace, vacuumize until the vacuum degree is kept above 6×10 ^-6 Pa, and then raise the temperature to 300°C within 45min and keep it stable for 20min, so as to remove the organic matter in the joint. The glue volatilizes cleanly, then it is heated up to the brazing temperature at 7.5°C/min and kept for 10 minutes, and finally lowered to 300°C at 5°C/min, and the connection is completed by cooling with the furnace;

The brazing temperature is 900°C.

The shear strength of the joint prepared in Step 5 of Test 1 was evaluated, and the room temperature strength of the obtained joint was 80.31 MPa.

Figure 2 is the SEM image of the joint prepared in step 5 of test 1. It can be observed that AgCuTi solder and Ag foil, AgCu solder and Ag foil are mutually dissolved, and Ag-based solid solution is formed on both sides of Mo.

In order to observe the morphology of the joint after corrosion, the joint prepared in step 5 of test 1 was corroded: the joint was acceleratedly corroded by the method of potentiodynamic polarization. The instrument used was an electrochemical workstation, in which the platinum electrode was used as the counter electrode. The joint is the working electrode, the saturated calomel electrode is the standard electrode, the 3.5wt.% NaCl aqueous solution is the electrolytic solution, the cross-sectional area of the tested joint is 4×8mm ² , the test voltage range is -0.3V～0.3V, and the scanning rate is is 5mV/s. The SEM morphology after corrosion is shown in Figure 3. There are no large holes in the entire weld area, and the overall joint shows good corrosion resistance.

Figure 4 shows the residual stress simulation cloud diagram of the traditional AgCuTi as the brazing material, brazing Si ₃ N ₄ and 316L stainless steel joints;

Fig. 5 is a simulation cloud diagram of residual stress of the joint prepared in step 5 of test 1. It can be seen that the maximum residual stress (165.4MPa) of the Si ₃ N ₄ and 316L stainless steel joints welded with the AgCu/Ag/Mo/Ag/AgCuTi composite solder in test 1 is significantly smaller than the maximum residual stress of the joint with traditional AgCuTi as the solder ( 303.4MPa).

Test 2: The difference between this test and test 1 is that the brazing temperature in step 5 is 950° C., and the thickness of the Ag foil described in step 2 is 2031.11 μm. Others are the same as test 1.

The shear strength of the joint prepared in step 5 of test 2 was evaluated, and the room temperature strength of the obtained joint was 63.36 MPa.

Claims (1)

1. a preparation method of the silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief is characterized in that the preparation method of the silicon nitride ceramic/stainless steel brazing joint with corrosion resistance and stress relief is as follows: 1. The surface to be welded of the base metal Si ₃ N ₄ ceramic is polished to smooth with 300# metallographic sandpaper, 600# metallographic sandpaper and 1000# metallographic sandpaper in turn, ultrasonically oscillated in acetone for 3 minutes, and then placed in an oven to dry Dry; The ultrasonic vibration described in the step 1 is carried out in an ultrasonic oscillator; The frequency of the ultrasonic vibration described in the step 1 is 40KHz; The drying described in step 1 is drying at 80°C for 2 hours; 2. Grind the base material 316L stainless steel with 600#SiC sandpaper and #1000SiC sandpaper in turn to remove the surface oxide layer, then use 800# metallographic sandpaper and 1000# metallographic sandpaper in turn to polish until bright, and then clean with ultrasonic vibration in acetone for 3min , and finally put the material into the oven to dry; The ultrasonic vibration described in the step 2 is carried out in an ultrasonic oscillator; the frequency of the ultrasonic vibration described in the step 2 is 40KHz; The drying described in step 2 is drying at 80° C. for 2 hours; in step 2, the solder AgCuTi is Ag69Cu28Ti3 (wt.%); in step 2, the solder AgCu is Ag28Cu (wt.%); Step 2: The thickness of the solder AgCuTi and the solder AgCu are both 100 μm, the thickness of the Ag foil is 305.47 μm, and the thickness of the Mo foil is 500 μm; Repeat the above operations in step 2 for Mo foil, Ag foil, solder AgCuTi and solder AgCu respectively; 3. Assemble the dried materials in steps 1 and 2 according to the structure of base material 316L stainless steel/AgCu/Ag/Mo/Ag/AgCuTi/base material Si ₃ N ₄ ceramics. When assembling, for the purpose of solder layer The assembly is stable, each two layers are bonded with 502 glue, and they are naturally placed until the 502 glue solidifies; 4. Put the joint prepared in step 3 into the graphite mold, the base material Si ₃ N ₄ ceramic is located above, and place a graphite block on the upper surface of the base material Si ₃ N ₄ ceramic for physical pressure to avoid the metal brazing during the heating process. The material melts and the base metal is removed from its original position, which greatly reduces the welding effect; 5. Put the graphite mold in step 4 into the vacuum brazing furnace, vacuumize until the vacuum degree is kept above 6×10 ^-6 Pa, and then raise the temperature to 300°C within 45min and keep it stable for 20min, so as to remove the organic matter in the joint. The glue volatilizes cleanly, then it is heated up to the brazing temperature at 7.5°C/min and kept for 10 minutes, and finally lowered to 300°C at 5°C/min, and the connection is completed by cooling with the furnace; The brazing temperature is 900°C.

Images