A method for brazing zinc sulfide ceramics and titanium alloy using a silver-based medium-temperature brazing filler metal

Abstract

A method for brazing zinc sulfide ceramics and titanium alloy using a silver-based medium-temperature brazing filler metal, which relates to a method for brazing zinc sulfide ceramics and titanium alloy. The present invention aims to solve the technical problems that the joints between zinc sulfide ceramics and metals obtained by the current mechanical method and bonding method have low strength, poor airtightness and poor heat resistance, resulting in the mismatch between the joints and the application temperature of the zinc sulfide infrared window. The present invention uses a new type of AgGe eutectic brazing filler metal to achieve medium-temperature vacuum sealing of zinc sulfide ceramics and titanium alloy at 680 °C to 740 °C. This brazing filler metal has excellent wettability to both zinc sulfide ceramics and titanium alloy, can achieve defect-free connection of zinc sulfide ceramics and titanium alloy, improve the reliability of the joints between zinc sulfide ceramics and titanium alloy when used at higher temperatures of 500 °C to 600 °C, and greatly expand the application of zinc sulfide ceramics in the field of infrared windows.

Description

Technical Field

[0001] The present invention relates to a method for brazing zinc sulfide ceramics and titanium alloys. Background Art

[0002] As an optical functional material, zinc sulfide ceramics have excellent infrared transmission performance, certain mechanical strength, and good chemical stability, making them widely used in components such as lenses, prisms, nose cones, fairings, especially infrared windows, etc. of the infrared detection systems of high-speed aircraft. Titanium alloys, due to their high specific strength, easy machining, and high temperature resistance, can be used as metal frames connected to infrared window sheets. However, currently, in the process of assembling infrared windows, mechanical methods and adhesive bonding methods are often used to obtain joints between zinc sulfide ceramics and metals, which often have problems such as low strength, poor airtightness, and poor heat resistance, and cannot meet the extreme service requirements of infrared windows of high-speed aircraft. The vacuum brazing technology not only has reliable joint connections, but also the filler metal has strong designability, which is beneficial to obtaining heat-resistant and high-strength zinc sulfide ceramic / titanium alloy joints. Considering the characteristics of zinc sulfide ceramics with high temperature resistance and a maximum service temperature of up to 600 °C, a medium-temperature filler metal with a melting point of 600 °C to 800 °C should be designed. Since there is no precedent for brazing zinc sulfide ceramics and metals at present, it is necessary to develop a metal filler metal and brazing method suitable for connecting zinc sulfide ceramics and titanium alloys to solve the above requirements. Summary of the Invention

[0003] The present invention aims to solve the technical problem that the joints between zinc sulfide ceramics and metals obtained by current mechanical methods and adhesive bonding methods have low strength, poor airtightness, and poor heat resistance, resulting in a mismatch between the joints and the application temperature of zinc sulfide infrared windows, and provides a method for brazing zinc sulfide ceramics and titanium alloys using a silver-based medium-temperature filler metal.

[0004] The method for brazing zinc sulfide ceramics and titanium alloys using a silver-based medium-temperature filler metal of the present invention is carried out according to the following steps:

[0005] I. Preparation of zinc sulfide ceramic base material and titanium alloy base material: The used zinc sulfide ceramic base material is a dense ceramic material obtained by chemical vapor deposition followed by hot isostatic pressing, and the titanium alloy base material is a dense material obtained by hot pressing sintering; Use a diamond wire cutting machine to cut the zinc sulfide ceramic base material and the titanium alloy base material to obtain samples to be welded, and then use 800#, 1000#, 2000#, and 5000# metallographic sandpapers to polish the surfaces of the zinc sulfide ceramic surface to be welded and the titanium alloy base material surface to be welded until they are shiny, and place them in alcohol for ultrasonic cleaning for 10 min to 16 min each, and dry them with a hair dryer for later use;

[0006] II. Preparation of the filler metal:

[0007] Ag powder and Ge powder were ball-milled and mixed according to the atomic ratio of Ag:Ge=3:1 to obtain AgGe solder powder, and the powder was pressed into a sheet with a thickness of 100 μm to 200 μm by using a tablet press at a pressure of 8 MPa to 12 MPa for 5 min to 6 min;

[0008] 3. Assembly of welding samples: The solder sheet obtained in step 2 is sandwiched between the two base materials obtained in step 1 in a sandwich assembly manner, and is fixed with an organic adhesive to obtain a sample to be welded;

[0009] 4. Welding process: Place the sample assembled in step 3 into a vacuum furnace, and keep the vacuum degree in the furnace at 1×10 -3 Pa, place a pressing block on the upper surface of the sample to be welded to provide a pressure of 0.1MPa~0.3MPa, first heat up from room temperature to 300℃~320℃ at a heating rate of 10℃ / min~15℃ / min and keep warm for 10min~15min, then heat up to 600℃~620℃ at a heating rate of 10℃ / min~15℃ / min, then heat up to 680℃~740℃ at a rate of 5℃ / min~10℃ / min and keep warm for 5min~20min, then cool down to 300℃~320℃ at a cooling rate of 5℃ / min~10℃ / min, and finally cool to room temperature with the furnace, thus completing the connection of zinc sulfide ceramic and titanium alloy brazing using AgGe brazing filler metal.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] 1. The present invention uses a brazing method, which is easy to operate. By designing an AgGe brazing material with a eutectic point of 651°C, the medium-temperature connection of zinc sulfide ceramics and titanium alloy is successfully achieved under vacuum conditions of 680°C to 740°C;

[0012] 2. The AgGe solder in the present invention has excellent wettability to both sides of the parent materials, and the solder and the parent materials on both sides have good interface bonding during the brazing process: the solder diffuses to the zinc sulfide ceramic parent material side to a certain extent, and the Ti element diffuses from the titanium alloy side to the zinc sulfide ceramic side to participate in the reaction to form a sulfide layer, and the reaction layer is mainly Ti-S compounds; the solder reacts with the titanium alloy parent material to form a continuous Ti-Ge interface reaction layer; the weld structure is mainly Ag-Ge eutectic, which has a higher melting point, and greatly improves the heat resistance of the joint;

[0013] 3. The present invention obtains a zinc sulfide ceramic / titanium alloy joint with excellent heat resistance and excellent mechanical properties. Under the process conditions of keeping warm at 720°C for 10 minutes, the shear strength at room temperature can reach 31.6MPa, and the shear strength at 500°C can reach 36.6MPa, which can realize high-temperature application of infrared windows of high-speed aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a backscattered electron scanning image of a joint obtained by connecting zinc sulfide ceramic and titanium alloy using AgGe solder in Example 3;

[0015] Figure 2 for Figure 1 A partial enlarged view of the middle area A;

[0016] Figure 3 for Figure 2 Energy spectrum point analysis diagram of midpoint 1 phase;

[0017] Figure 4 for Figure 2 Energy spectrum point analysis diagram of midpoint 2 phase;

[0018] Figure 5 for Figure 1 A partial enlarged view of the middle area B;

[0019] Figure 6 for Figure 5 Energy spectrum point analysis diagram of midpoint 3 phase. DETAILED DESCRIPTION

[0020] Specific implementation method 1: This implementation method is a method for brazing zinc sulfide ceramics and titanium alloy using silver-based medium-temperature brazing filler metal, which is specifically carried out in the following steps:

[0021] 1. Preparation of zinc sulfide ceramic matrix and titanium alloy matrix: the zinc sulfide ceramic matrix used is a dense ceramic material obtained by hot isostatic pressing after chemical vapor deposition, and the titanium alloy matrix is ​​a dense material obtained by hot pressing and sintering; the zinc sulfide ceramic matrix and the titanium alloy matrix are cut by a diamond wire cutting machine to obtain samples to be welded, and then the surfaces to be welded of the zinc sulfide ceramic and the titanium alloy matrix are polished and polished with 800#, 1000#, 2000# and 5000# metallographic sandpapers in turn until the surfaces are glossy, and then ultrasonically cleaned in alcohol for 10min to 16min, and dried with a hair dryer for standby use;

[0022] 2. Preparation of solder:

[0023] Ag powder and Ge powder were ball-milled and mixed according to the atomic ratio of Ag:Ge=3:1 to obtain AgGe solder powder, and the powder was pressed into a sheet with a thickness of 100 μm to 200 μm by using a tablet press at a pressure of 8 MPa to 12 MPa for 5 min to 6 min;

[0024] 3. Assembly of welding samples: The solder sheet obtained in step 2 is sandwiched between the two base materials obtained in step 1 in a sandwich assembly manner, and is fixed with an organic adhesive to obtain a sample to be welded;

[0025] IV. Welding process: Place the sample to be welded assembled in Step 3 into a vacuum furnace, and keep the vacuum degree in the furnace below 1×10 -3 Pa. Place a pressing block on the upper surface of the sample to be welded to provide a pressure of 0.1 MPa - 0.3 MPa. First, heat from room temperature to 300°C - 320°C at a heating rate of 10°C / min - 15°C / min and hold for 10 min - 15 min, then heat to 600°C - 620°C at a heating rate of 10°C / min - 15°C / min, and then heat to 680°C - 740°C at a rate of 5°C / min - 10°C / min and hold for 5 min - 20 min. Then, cool to 300°C - 320°C at a cooling rate of 5°C / min - 10°C / min, and finally cool in the furnace to room temperature, thus completing the connection of zinc sulfide ceramic and titanium alloy by brazing with AgGe filler metal.

[0026] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the zinc sulfide ceramic base material used in Step 1 is multi-spectral zinc sulfide obtained by chemical vapor deposition followed by hot isostatic pressing. Others are the same as Specific Embodiment 1.

[0027] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that the titanium alloy base material used in Step 1 is TA15 titanium alloy or TC4 titanium alloy obtained by hot pressing and sintering. Others are the same as Specific Embodiment 1 or 2.

[0028] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that in Step 1, the base material is cut into block samples with a size of 5 mm×5 mm or 5 mm×10 mm for the welding surface. Others are the same as any one of Specific Embodiments 1 to 3.

[0029] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that in Step 1, each is ultrasonically cleaned in alcohol for 15 min. Others are the same as any one of Specific Embodiments 1 to 4.

[0030] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that in Step 2, a tablet press is used to keep the pressure at 10 MPa for 5 min and pressed into a thin sheet with a thickness of 150 μm. Others are the same as any one of Specific Embodiments 1 to 5.

[0031] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that the organic binder described in Step 3 is 502 glue. Others are the same as any one of Specific Embodiments 1 to 6.

[0032] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is that: the pressing block described in Step 4 is a tungsten block, providing a pressure of 0.2 MPa. Others are the same as any one of Embodiments 1 to 7.

[0033] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is that: the vacuum degree in the furnace in Step 4 is 6×10 -4 Pa. Others are the same as any one of Embodiments 1 to 8.

[0034] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is that: in Step 4, the temperature is raised from 300 °C to 600 °C at a heating rate of 10 °C / min. Others are the same as any one of Embodiments 1 to 9.

[0035] The present invention is verified by the following examples:

[0036] Example 1: This test is a method for brazing zinc sulfide ceramics and titanium alloy using a silver-based medium-temperature brazing filler metal, and specifically is carried out according to the following steps:

[0037] I. Preparation of zinc sulfide ceramic base material and titanium alloy base material: The used zinc sulfide ceramic base material is a dense ceramic material obtained by chemical vapor deposition followed by hot isostatic pressing, and the titanium alloy base material is a dense material TA15 titanium alloy obtained by hot press sintering; the zinc sulfide ceramic base material and the titanium alloy base material are cut into 5 mm×5 mm using a diamond wire cutting machine to obtain samples to be welded, and then the surfaces to be welded of the zinc sulfide ceramic and the titanium alloy base material are polished with 800#, 1000#, 2000# and 5000# metallographic sandpapers in sequence until the surfaces are shiny, and then ultrasonically cleaned in alcohol for 15 min each, and dried with a hair dryer for standby;

[0038] II. Preparation of the brazing filler metal:

[0039] The Ag powder and Ge powder are ball-milled and mixed according to an atomic ratio of Ag:Ge = 3:1 to obtain AgGe brazing filler metal powder, and a tablet press is used to press it into a thin sheet with a thickness of 150 μm under a pressure of 10 MPa for 5 min;

[0040] III. Assembly of the welding specimen: The brazing filler metal thin sheet obtained in Step II is clamped between the two base materials obtained in Step I and assembled in a sandwich assembly manner, and fixed with organic binder 502 glue to obtain a sample to be welded;

[0041] IV. Welding process: The sample to be welded assembled in Step III is placed in a vacuum furnace, and the vacuum degree in the furnace is 6×10 -4Pa, place a tungsten block on the upper surface of the sample to be welded to provide a pressure of 0.2 MPa. First, heat from room temperature to 300 °C at a heating rate of 10 °C / min and hold for 10 min, then heat to 600 °C at a heating rate of 10 °C / min, and then increase the temperature to the connection temperature of 680 °C at a rate of 5 °C / min and hold for 10 min. Then, cool down to 300 °C at a cooling rate of 5 °C / min, and finally cool to room temperature in the furnace, thus completing the connection of zinc sulfide ceramics and titanium alloy by brazing with AgGe filler metal.

[0042] Example 2

[0043] The difference between this example and Example 1 is that: the connection temperature in Step 4 is 700 °C. Other steps and parameters are the same as those in Experiment 1.

[0044] Example 3

[0045] The difference between this example and Example 1 is that: the connection temperature in Step 4 is 720 °C. Other steps and parameters are the same as those in Experiment 1.

[0046] Example 4

[0047] The difference between this example and Example 1 is that: the connection temperature in Step 4 is 740 °C. Other steps and parameters are the same as those in Experiment 1.

[0048] Example 5

[0049] The difference between this example and Example 1 is that: the connection temperature in Step 4 is 720 °C and hold for 5 min. Other steps and parameters are the same as those in Experiment 1.

[0050] Example 6

[0051] The difference between this example and Example 1 is that: the connection temperature in Step 4 is 720 °C and hold for 20 min. Other steps and parameters are the same as those in Experiment 1.

[0052] Table 1

[0053]

[0054] Table 1 shows the shear strength test data of the joints of dissimilar materials of zinc sulfide ceramics / titanium alloy completed in Examples 1 to 6. It can be seen from the table that by using the welding method of the present invention to connect zinc sulfide ceramics and titanium alloy, the maximum room temperature shear strength of the obtained joint can reach 31.6 MPa (Example 3), and the shear strength of the joint at a test temperature of 500 °C can reach 36.6 MPa.

[0055] Figure 1Backscattered electron scanning image of the joint obtained by connecting zinc sulfide ceramics and titanium alloy using AgGe filler metal in Example 3. Region Ⅰ is the zinc sulfide ceramic base material, Region Ⅱ is the weld seam, and Region Ⅲ is the TA15 titanium alloy base material. It can be seen that the joint is overall dense, and the interfaces on both sides are well bonded without obvious defects.

[0056] Figure 2 is Figure 1 a partial enlarged view of Region A in Figure 3 and Figure 4 are respectively Figure 2 EDS point analysis diagrams of the phases at Point 1 and Point 2. It can be seen the black Ti-S reaction layer on the zinc sulfide ceramic side and the Ge-based solid solution at the interface.

[0057] Figure 5 is Figure 1 a partial enlarged view of Region B in Figure 6 is Figure 5 the EDS point analysis diagram of the phase at Point 3. It can be seen the Ti-Ge compound interfacial reaction layer between TA15 titanium alloy and the filler metal.

Claims

1. A method for brazing zinc sulfide ceramics and titanium alloys using silver-based medium-temperature solder, characterized in that The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder is carried out in the following steps:

1. Preparation of zinc sulfide ceramic matrix and titanium alloy matrix: the zinc sulfide ceramic matrix used is a dense ceramic material obtained by hot isostatic pressing after chemical vapor deposition, and the titanium alloy matrix is ​​a dense material obtained by hot pressing and sintering; the zinc sulfide ceramic matrix and the titanium alloy matrix are cut by a diamond wire cutting machine to obtain samples to be welded, and then the surfaces to be welded of the zinc sulfide ceramic and the titanium alloy matrix are polished and polished with 800#, 1000#, 2000# and 5000# metallographic sandpapers in turn until the surfaces are glossy, and then ultrasonically cleaned in alcohol for 10min to 16min, and dried with a hair dryer for standby use; 2. Preparation of solder: Ag powder and Ge powder were ball-milled and mixed according to the atomic ratio of Ag:Ge=3:1 to obtain AgGe solder powder, and the powder was pressed into a sheet with a thickness of 100 μm to 200 μm by using a tablet press at a pressure of 8 MPa to 12 MPa for 5 min to 6 min; The AgGe solder powder is an AgGe solder powder with a eutectic point of 651°C; 3. Assembly of welding samples: The solder sheet obtained in step 2 is sandwiched between the two base materials obtained in step 1 in a sandwich assembly manner, and is fixed with an organic adhesive to obtain a sample to be welded; 4. Welding process: Place the sample assembled in step 3 into a vacuum furnace, and keep the vacuum degree in the furnace at 1×10 -3 Pa, place a pressing block on the upper surface of the sample to be welded to provide a pressure of 0.1MPa~0.3MPa, first heat up from room temperature to 300℃~320℃ at a heating rate of 10℃ / min~15℃ / min and keep warm for 10min~15min, then heat up to 600℃~620℃ at a heating rate of 10℃ / min~15℃ / min, then heat up to 680℃~740℃ at a rate of 5℃ / min~10℃ / min and keep warm for 5min~20min, then cool down to 300℃~320℃ at a cooling rate of 5℃ / min~10℃ / min, and finally cool to room temperature with the furnace, thus completing the connection of zinc sulfide ceramic and titanium alloy brazing using AgGe brazing filler metal.

2. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that The zinc sulfide ceramic matrix material used in step 1 is multi-spectrum zinc sulfide obtained by hot isostatic pressing after chemical vapor deposition.

3. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that The titanium alloy base material used in step 1 is TA15 titanium alloy or TC4 titanium alloy obtained by hot pressing and sintering.

4. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that In step 1, the base material is cut into block samples with a size of 5 mm×5 mm or 5 mm×10 mm for the surface to be welded.

5. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that In step 1, ultrasonic cleaning was performed in alcohol for 15 minutes.

6. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that In step 2, a tablet press is used to press the film into a sheet with a thickness of 150 μm at a pressure of 10 MPa for 5 minutes.

7. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that The organic binder described in step three is 502 glue.

8. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that The pressing block described in step 4 is a tungsten block, which provides a pressure of 0.2 MPa.

9. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that The vacuum degree in the furnace in step 4 is 6×10 -4 Pa.

10. The method for brazing zinc sulfide ceramic and titanium alloy using silver-based medium-temperature solder according to claim 1, characterized in that In step 4, the temperature is increased from 300°C to 600°C at a heating rate of 10°C / min.

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