CN116532740A - Method for step-by-step brazing of magnesium fluoride ceramic and titanium alloy by using metal and glass solder - Google Patents

Abstract

The invention discloses a step-by-step brazing method of magnesium fluoride ceramics and titanium alloys by using metal and glass solder, and relates to a method for brazing magnesium fluoride ceramics and titanium alloys. The invention aims to solve the technical problem that the magnesium fluoride ceramics are difficult to wet with active solder due to the large bond energy of F-Mg, resulting in low room temperature shear strength of the joint. The invention adopts the step-by-step connection technology of metal brazing and glass brazing, selects Ni-based high-temperature alloy as the intermediate transition layer, and selects glass solder between the base material magnesium fluoride ceramics and the intermediate layer of Ni-based high-temperature alloy. Metal solder is selected between the alloy intermediate layer and the titanium alloy, and the melting temperature difference of the solder used in the above two interfaces exceeds 100° C. Therefore, the present invention adopts a two-step welding process. The invention provides technical support for the application of magnesium fluoride ceramics in optical windows.

Description

A method for brazing magnesium fluoride ceramics and titanium alloys step by step with metal and glass solder

technical field

The invention relates to a method for brazing magnesium fluoride ceramics and titanium alloys.

Background technique

Magnesium fluoride (MgF ₂ ) ceramics is an optical functional ceramic material with many special physical and chemical properties, including good light transmittance, high mechanical strength, thermal shock resistance, chemical stability, high hardness, corrosion etc. Due to their excellent optical properties in the mid-infrared region, their applications in optical devices such as infrared windows and domes have attracted extensive attention in recent years. When used as a transparent ceramic window, it often needs to be combined with a metal frame to form an optical component. In the past, the connection between the transparent window and the metal support has been achieved by means of adhesive bonding or mechanical connection. With the demand for high temperature resistance, mechanical stability and light weight of the infrared window, the above connection methods have highlighted some problems, such as glue. The joints have poor high-temperature aging resistance and weak mechanical stability, and are prone to cracking and failure during service, making it difficult to meet the requirements of high temperature and long-life service; the components obtained by mechanical connection are complex in structure, prone to stress concentration, and difficult to meet the requirements of lightweight. The density of titanium alloy is usually about 4.51g/cm ³ , which is lower than that of steel, copper and nickel, and only 60% of the density of steel. Lightweight parts. The connection between magnesium fluoride ceramics and titanium alloys is essentially a connection between ceramics and metal dissimilar materials. Due to the difference in chemical bonding between the two, the connection is extremely difficult. In addition, due to the difference in thermal expansion coefficient between magnesium fluoride ceramics and titanium alloys, the problem of residual stress after welding need to be resolved. Brazing connection has the advantages of reliable joints and good repeatability, and has become the most commonly used method for connecting ceramics and metals. Using Ag, Cu, Ti and other active solders to directly braze metals and ceramics has the advantages of simple technology, high connection strength, low production cost, and good repeatability. Due to the large F-Mg bond energy of magnesium fluoride ceramics, it is difficult to wet with active solder, and new connection technologies still need to be developed. Solving the problem of connecting magnesium fluoride ceramics and titanium alloys has important practical engineering application value to meet the application requirements of high-strength, heat-resistant, and long-life ceramic-metal new connecting components.

Contents of the invention

The present invention aims to solve the technical problem that magnesium fluoride ceramics are difficult to wet with active solder due to the large F-Mg bond energy, resulting in low room temperature shear strength of the joint, and provides a step-by-step soldering method using metal and glass solder A method for welding magnesium fluoride ceramics and titanium alloys.

The method of step-by-step brazing magnesium fluoride ceramics and titanium alloy with metal and glass solder of the present invention is carried out according to the following steps:

1. Assembly: Assemble the base metal titanium alloy, Ag-based brazing filler metal and Ni-based superalloy into a sandwich structure, with the Ag-based brazing filler metal in the middle;

2. Vacuum brazing: put the sandwich structure assembled in step 1 into the fixed fixture, place it in a vacuum brazing furnace, heat it to 780℃～850℃, the vacuum degree is not lower than 2×10 ^-2 Pa, and keep it warm for 5min ~20min, then cool at a rate of 10°C/min~15°C/min to 300°C~320°C, then cool to room temperature with the furnace to obtain a pre-sample;

3. Reassembly: Assemble according to the sandwich structure of the pre-sample/glass solder/base material magnesium fluoride ceramics, and the side of the Ni-based superalloy in the pre-sample is close to the glass solder;

Described glass solder is bismuth borate;

4. Air brazing: put the weldment in the third step together with the fixture into a resistance heating furnace and heat it to 660 ° C ~ 720 ° C, keep it warm for 10 min ~ 30 min, air atmosphere, and then use 5 ° C / min ~ 10 ° C / min Cool to 300°C to 320°C, and then cool to room temperature with the furnace to complete the brazing connection of magnesium fluoride ceramics and titanium alloys.

The invention adopts the step-by-step connection technology of metal brazing and glass brazing, selects Ni-based high-temperature alloy as the intermediate transition layer, and selects glass solder between the base material magnesium fluoride ceramics and the intermediate layer of Ni-based high-temperature alloy. Metal solder is selected between the alloy intermediate layer and the titanium alloy, and the melting temperature difference of the solder used in the above two interfaces exceeds 100° C. Therefore, the present invention adopts a two-step welding process.

The present invention has the following beneficial effects:

The method of step-by-step brazing magnesium fluoride ceramics and titanium alloys with metal and glass solder not only solves the problem that magnesium fluoride ceramics are difficult to use active metal brazing technology to realize connection, but also solves the thermal matching of ceramic/metal dissimilar materials The specific reasons for the problem of poor performance are as follows: On the one hand, the Ni-based superalloy intermediate layer and the base material titanium alloy can be connected through the Ag-based solder, and the connection mechanism is that the molten Ag-based solder dissolves the surface of the titanium alloy and dissolves into the liquid The Ti element in the phase brazing material (from the base metal titanium alloy) can react with Cu (from the Ag-based solder) and Ni (from the Ni-based superalloy), and form Cu- Ti and Cu-Ti-Ni intermetallic compounds realize the metallurgical bonding between the solder and the base metal; on the other hand, because the chemical stability of magnesium fluoride ceramics is extremely high, the commonly used active metal elements Ti, Zr, Hf, etc. cannot be combined with fluorine Magnesium chloride reaction realizes connection, and molten glass solder can react with magnesium fluoride ceramics, bismuth borate glass solder (Bi ₂ O ₃ -B ₂ O ₃ -ZnO) used in the present invention and fluoride Magnesium reaction can generate magnesium oxide (MgO) and fluoborite phase Mg ₃ (BO ₃ ) F ₃ , so as to achieve interfacial reaction combination with magnesium fluoride ceramics. In addition, the molten bismuth borate glass solder can be heated in the air. It forms a good interface bond with Ni-based superalloys, because the surface of Ni-based superalloys is oxidized under air conditions to form a dense oxide layer composed of (Cr, Fe, Ni)O, which is in contact with the Ni-based superalloy matrix The combination is good and it is not easy to fall off, and the molten glass solder and the oxide layer are composed of oxides, and the bonding between the two is similar, and the glass can wet the oxide layer. Connect in the middle. The present invention realizes titanium alloy and magnesium fluoride ceramics through two kinds of brazing techniques, and at the same time solves the problem of large residual stress caused by the difference in thermal expansion coefficient of the two base materials. The present invention selects Ni-based superalloy as the intermediate transition layer, one is The material itself has good oxidation resistance, and the formed oxide film can be well combined with Ni-based superalloy, and can be combined with glass solder; second, its thermal expansion coefficient is 13.5×10 ^-6 K ^-1 The thermal expansion coefficient of magnesium ceramics is very close to 13.1×10 ^-6 K ^-1 , and the elastic modulus is high (200GPa), which can prevent the transfer of residual thermal stress to the magnesium fluoride ceramic side after welding, and the Ag-based solder has excellent plasticity and toughness , can effectively relieve the residual thermal stress of titanium alloy and Ni-based superalloy after brazing, and has good metallurgical compatibility with both sides of the metal (base metal titanium alloy and Ni-based superalloy), and finally can ensure the metallurgical quality Good and reliable connection between magnesium fluoride ceramics and titanium alloy dissimilar materials.

The invention provides technical support for the application of magnesium fluoride ceramics in optical windows.

Description of drawings

Fig. 1 is the microscopic appearance diagram of glass solder powder (85Bi ₂ O ₃ -5B ₂ O ₃ -10ZnO) in embodiment 1;

Fig. 2 is the tissue photo of a typical joint of TA15/Ag-28Cu/GH4169/85Bi ₂ O ₃ -5B ₂ O ₃ -10ZnO/MgF ₂ finally obtained in Example 3;

Fig. 3 is the XRD curve of the reaction layer of magnesium fluoride ceramics and glass solder in Example 3.

Detailed ways

Embodiment 1: This embodiment is a method for step-by-step brazing magnesium fluoride ceramics and titanium alloys with metal and glass solder, specifically according to the following steps:

1. Assembly: Assemble the base metal titanium alloy, Ag-based brazing filler metal and Ni-based superalloy into a sandwich structure, with the Ag-based brazing filler metal in the middle;

2. Vacuum brazing: put the sandwich structure assembled in step 1 into the fixed fixture, place it in a vacuum brazing furnace, heat it to 780℃～850℃, the vacuum degree is not lower than 2×10 ^-2 Pa, and keep it warm for 5min ~20min, then cool at a rate of 10°C/min~15°C/min to 300°C~320°C, then cool to room temperature with the furnace to obtain a pre-sample;

3. Reassembly: Assemble according to the sandwich structure of the pre-sample/glass solder/base material magnesium fluoride ceramics, and the side of the Ni-based superalloy in the pre-sample is close to the glass solder;

Described glass solder is bismuth borate;

4. Air brazing: put the weldment in the third step together with the fixture into a resistance heating furnace and heat it to 660 ° C ~ 720 ° C, keep it warm for 10 min ~ 30 min, air atmosphere, and then use 5 ° C / min ~ 10 ° C / min Cool to 300°C to 320°C, and then cool to room temperature with the furnace to complete the brazing connection of magnesium fluoride ceramics and titanium alloys.

Embodiment 2: This embodiment differs from Embodiment 1 in that: the Ag-based solder described in step 1 is AgCu solder or AgCuInTi solder. Others are the same as the first embodiment.

Embodiment 3: This embodiment differs from Embodiment 1 or Embodiment 2 in that: the base material titanium alloy described in step 1 is TA15 alloy. Others are the same as those in Embodiment 1 or 2.

Embodiment 4: This embodiment differs from Embodiment 1 to Embodiment 3 in that the Ni-based superalloy described in step 1 is GH4169. Others are the same as one of the specific embodiments 1 to 3.

Embodiment 5: This embodiment is different from Embodiment 4 in that: the Ag-based solder described in step 1 is in the form of alloy powder or thin strip. Others are the same as in Embodiment 4.

Embodiment 6: This embodiment differs from Embodiment 5 in that: the glass solder described in step 3 is glass powder or glass sheet, and the glass powder should be made into a paste. Others are the same as the fifth embodiment.

Embodiment 7: This embodiment differs from Embodiment 6 in that the bismuth borate described in step 3 is 85Bi ₂ O ₃ -5B ₂ O ₃ -10ZnO, and the coefficient is mass percent. Others are the same as the sixth embodiment.

Embodiment 8: This embodiment is different from Embodiment 7 in that: in step 4, heat to 660° C. and keep warm for 30 minutes. Others are the same as the seventh embodiment.

Embodiment 9: This embodiment differs from Embodiment 8 in that: in step 4, heat to 700° C. and keep warm for 30 minutes. Others are the same as the eighth embodiment.

Embodiment 10: This embodiment is different from Embodiment 9 in that: in step 4, heat to 720° C. and keep warm for 30 minutes. Others are the same as the ninth embodiment.

The present invention is verified with following test:

Choose AgCu eutectic solder or AgCuInTi solder to braze titanium alloy and Ni-based superalloy. The titanium alloy is TA15 alloy, and the intermediate layer of Ni-based superalloy is GH4169. The intermediate layer of titanium alloy and Ni-based superalloy is vacuum brazed. After the brazing, Bi ₂ O ₃ -B ₂ O ₃ -ZnO glass is used as the glass solder to carry out the glass brazing of GH4169 and magnesium fluoride ceramics. A total of 8 examples are carried out, specifically as follows: :

1. Assembly: Assemble the base metal titanium alloy TA15, Ag-based solder and Ni-based superalloy GH4169 into a sandwich structure, with the Ag-based solder in the middle;

2. Vacuum brazing: put the sandwich structure assembled in step 1 into the fixed fixture, place it in a vacuum brazing furnace, heat it to 780℃～850℃, the vacuum degree is not lower than 2×10 ^-2 Pa, and keep it warm for 5min ~20min, then cooled to 300°C at a rate of 10°C/min, and then cooled to room temperature with the furnace to obtain a pre-sample;

3. Reassembly: Assemble according to the sandwich structure of the pre-sample/glass solder/base material magnesium fluoride ceramics, and the side of the Ni-based superalloy in the pre-sample is close to the glass solder;

Described glass solder is bismuth borate;

4. Air brazing: Put the weldment in the third step together with the fixture into a resistance heating furnace and heat it to 660°C~720°C, keep it warm for 10min~30min, air atmosphere, and then cool it to 300°C at 5°C/min. Then it was cooled to room temperature with the furnace to complete the brazing connection of magnesium fluoride ceramics and titanium alloy; the specific parameters of some processes and the room temperature shear strength of the final joint are shown in Table 1.

Table 1

Fig. 1 is a microscopic view of the glass solder powder (85Bi ₂ O ₃ -5B ₂ O ₃ -10ZnO) in Example 1. It can be seen that the particle size of the glass solder powder is within 5 μm.

Figure 2 is the microstructure photo of a typical joint of TA15/Ag-28Cu/GH4169/85Bi ₂ O ₃ -5B ₂ O ₃ -10ZnO/MgF ₂ finally obtained in Example 3, in which 1 is titanium alloy TA15, and 2 is Ag-28Cu , 3 is the GH4169 intermediate layer, 4 is the 85Bi ₂ O ₃ -5B ₂ O ₃ -10ZnO glass weld, 5 is the magnesium fluoride ceramic base material.

Fig. 3 is the XRD curve of the reaction layer of magnesium fluoride ceramics and glass solder in Example 3, it can be seen that MgO and fluoborite phase Mg ₃ (BO ₃ ) F ₃ are formed.

Claims (10)

1. A method for step-by-step brazing magnesium fluoride ceramics and titanium alloys with metal and glass solder, characterized in that the method for step-by-step brazing magnesium fluoride ceramics and titanium alloys with metal and glass solder is as follows ongoing: 1. Assembly: Assemble the base metal titanium alloy, Ag-based brazing filler metal and Ni-based superalloy into a sandwich structure, with the Ag-based brazing filler metal in the middle; 2. Vacuum brazing: put the sandwich structure assembled in step 1 into the fixed fixture, place it in a vacuum brazing furnace, heat it to 780℃～850℃, the vacuum degree is not lower than 2×10 ^-2 Pa, and keep it warm for 5min ~20min, then cool at a rate of 10°C/min~15°C/min to 300°C~320°C, then cool to room temperature with the furnace to obtain a pre-sample; 3. Reassembly: Assemble according to the sandwich structure of the pre-sample/glass solder/base material magnesium fluoride ceramics, and the side of the Ni-based superalloy in the pre-sample is close to the glass solder; Described glass solder is bismuth borate; 4. Air brazing: put the weldment in the third step together with the fixture into a resistance heating furnace and heat it to 660 ° C ~ 720 ° C, keep it warm for 10 min ~ 30 min, air atmosphere, and then use 5 ° C / min ~ 10 ° C / min Cool to 300°C to 320°C, and then cool to room temperature with the furnace to complete the brazing connection of magnesium fluoride ceramics and titanium alloys. 2. a kind of step-by-step brazing method of magnesium fluoride ceramics and titanium alloy with metal and glass solder according to claim 1, is characterized in that the Ag-based solder described in step 1 is AgCu solder or AgCuInTi solder material. 3. A method for brazing magnesium fluoride ceramics and titanium alloys step by step with metal and glass solder according to claim 1, characterized in that the base material titanium alloy described in step 1 is TA15 alloy. 4. A method for brazing magnesium fluoride ceramics and titanium alloys step by step with metal and glass solder according to claim 1, characterized in that the Ni-based superalloy described in step 1 is GH4169. 5. A method for step-by-step brazing magnesium fluoride ceramics and titanium alloys with metal and glass solder according to claim 1, characterized in that the Ag-based solder described in step 1 is alloy powder or thin strip form. 6. A method for step-by-step brazing of magnesium fluoride ceramics and titanium alloys with metal and glass solder according to claim 1, wherein the glass solder described in step 3 is glass powder or glass sheet, And the glass powder should be adjusted into a paste. 7. A method for brazing magnesium fluoride ceramics and titanium alloys step by step with metal and glass solder according to claim 1, characterized in that the bismuth borate described in step 3 is 85Bi ₂ O ₃ - 5B ₂ O ₃ -10ZnO, wherein the mass fraction of Bi ₂ O ₃ is 85%, the mass fraction of Bi ₂ O ₃ is 5%, and the mass fraction of ZnO is 10%. 8. A method for step-by-step brazing of magnesium fluoride ceramics and titanium alloys with metal and glass solder according to claim 1, characterized in that in step 4, heating to 660°C and holding for 30 minutes. 9. A method for step-by-step brazing of magnesium fluoride ceramics and titanium alloys with metal and glass solder according to claim 1, characterized in that in step 4, heating to 700°C and keeping the temperature for 30 minutes. 10. A method for brazing magnesium fluoride ceramics and titanium alloys step by step with metal and glass solder according to claim 1, characterized in that in step 4, heat to 720°C and keep warm for 30 minutes.