Brazing connection method for porous SiC ceramic and 2507 duplex stainless steel

Abstract

The invention provides a brazing connection method for porous SiC ceramic and 2507 duplex stainless steel, and belongs to the technical field of porous ceramic and metal welding, and the brazing connection method comprises the following steps: plating a layer of TiSn alloy brazing filler metal on the surface of the porous SiC ceramic as a plating layer by adopting ultrasonic-assisted brazing, and then carrying out polishing and ultrasonic cleaning to obtain a SiC / TiSn composite material; the surface of the 2507 duplex stainless steel is ground and then subjected to ultrasonic cleaning, and pretreated 2507 duplex stainless steel is obtained; and the pretreated 2507 duplex stainless steel, the high-entropy alloy brazing filler metal and the SiC / TiSn composite material are stacked from top to bottom and then subjected to vacuum brazing, and after the reaction is finished, natural cooling is conducted at the room temperature. According to the method, the TiSn alloy brazing filler metal is ultrasonically plated on the surface of the porous SiC ceramic with poor welding performance, the wettability of the TiSn alloy to the ceramic surface is high, the high-entropy alloy brazing filler metal is good in fluidity and can be well combined with a TiSn alloy plating layer, and the residual stress of the porous SiC ceramic and a metal reaction layer is reduced.

Description

Technical Field

[0001] This invention relates to the field of porous ceramics and metal welding technology, specifically to a brazing method for connecting porous SiC ceramics and 2507 duplex stainless steel. Background Technology

[0002] With the increasing maturity of solvent extraction and purification technology for wet-process phosphoric acid production in my country, the industrial application of wet-process phosphoric acid is gradually replacing that of thermal-process phosphoric acid. In the wet-process phosphoric acid production process, the system is characterized by high corrosivity, high temperature, and high solids content. Traditional membrane separation materials and their structural components are easily affected by corrosion and clogging in strong acid environments, leading to shortened service life and reduced separation efficiency. In harsh environments, membrane separation equipment needs higher structural strength and better corrosion resistance to ensure stable separation performance.

[0003] While porous SiC ceramics possess excellent corrosion resistance and impact resistance, existing porous ceramics used for membrane separation have a strength of approximately 50 MPa. However, some specialized chemical processes require membrane separation equipment with even higher structural strength, and their use alone presents certain limitations in terms of structure and function. In current applications, 2507 duplex stainless steel, with its comprehensive properties of high corrosion resistance, high strength, and stability, has become an ideal material for wet-process phosphoric acid storage, transportation, and reaction equipment. Both SiC ceramics and 2507 duplex stainless steel are high-performance materials, but the difficulty in directly bonding them limits their synergistic application in the field of wet-process phosphoric acid membrane separation. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a brazing connection method for porous SiC ceramics and 2507 duplex stainless steel, aiming to solve the technical problem that porous SiC ceramics and 2507 duplex stainless steel are difficult to directly connect.

[0005] In a first aspect, embodiments of this application provide a brazing method for connecting porous SiC ceramics to 2507 duplex stainless steel, comprising the following steps: S1. A layer of TiSn alloy brazing filler metal is deposited on the surface of porous SiC ceramic by ultrasonic-assisted brazing, followed by grinding and ultrasonic cleaning to obtain SiC / TiSn composite material. The surface of 2507 duplex stainless steel is polished and then ultrasonically cleaned to obtain pretreated 2507 duplex stainless steel. S2. Pretreated 2507 duplex stainless steel, high-entropy alloy brazing filler metal, and SiC / TiSn composite material are stacked from top to bottom and then vacuum brazed. After the reaction is complete, the mixture is allowed to cool naturally at room temperature.

[0006] The advantages of this application, which differ from existing technical solutions, include: 1. Compared with existing technologies, the brazing connection method for porous SiC ceramics and 2507 duplex stainless steel provided by this invention has the following significant advantages: TiSn alloy brazing filler metal is ultrasonically coated onto the surface of porous SiC ceramics, which have poor welding performance. TiSn alloy has high wettability on the ceramic surface, and the high-entropy alloy brazing filler metal has good fluidity, enabling it to form a good bond with the TiSn alloy coating, reducing residual stress in the reaction layer between the porous SiC ceramic and the metal. Testing the bond strength of the brazed joint shows a shear strength of up to 19.11 MPa, proving that porous ceramics and metal can form a structurally stable and dense reaction layer under the combined action of TiSn alloy brazing filler metal and high-entropy alloy brazing filler metal.

[0007] 2. The TiSn solder acts as a wetting agent. The TiZrCuNi high-entropy solder penetrates the porous ceramic matrix from one side through ultrasonic cavitation and capillary filling, while the other side undergoes an alloying reaction with stainless steel. The penetration layer has a uniform width, and the ceramic side contains an intermetallic compound such as a ZrC / TiC reaction layer, Fe2Si, and Ni2Si. The (Zr / Ti)C and Si-based reaction products tightly bond the liquid solder to the silicon carbide matrix, solving the problem of poor compatibility between ceramic and metal solders. This results in a stable connection structure with silicon carbide that combines mechanical interlocking and metallurgical bonding.

[0008] 3. This invention replaces the mechanical connection of core components in traditional skid-mounted equipment by brazing porous SiC ceramics to 2507 stainless steel. It fully leverages the corrosion resistance of SiC ceramics and the high strength and good processing performance of metals. By utilizing the high strength, good corrosion resistance, and excellent flowability of high-entropy alloy brazing filler metal, the mechanical integrity and functionality of the SiC porous structure can be guaranteed during the vacuum brazing process. This results in the fabrication of membrane separation equipment that can operate stably in harsh chemical environments, improving the reliability and efficiency of the separation process, meeting industry requirements for the structural strength of membrane separation equipment, and ensuring long-term stable operation of the membrane separation equipment under complex working conditions.

[0009] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0011] Figure 1 This is a schematic diagram of the brazing structure of this application.

[0012] Figure 2 This is a SEM scan of the brazed joint of the sample prepared in Example 1 of this application.

[0013] Figure 3 The image shows the XRD pattern of the 2507 stainless steel substrate at the brazed joint of the sample prepared in Example 1 of this application.

[0014] Figure 4 This is an XRD diagram of the ceramic substrate at the brazed joint of the sample prepared in Example 1 of this application.

[0015] Figure 5 The image shows the XRD pattern of the brazed joint of the sample prepared in Comparative Example 2 of this application. Detailed Implementation

[0016] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0018] While porous SiC ceramics possess excellent corrosion resistance and impact resistance, existing porous ceramics used for membrane separation have a strength of approximately 50 MPa. However, some specialized chemical processes require membrane separation equipment with even higher structural strength, and their use alone presents certain limitations in terms of structure and function. In current applications, 2507 duplex stainless steel, with its comprehensive properties of high corrosion resistance, high strength, and stability, has become an ideal material for wet-process phosphoric acid storage, transportation, and reaction equipment. Both SiC ceramics and 2507 duplex stainless steel are high-performance materials, but the difficulty in directly bonding them limits their synergistic application in the field of wet-process phosphoric acid membrane separation.

[0019] To address the technical challenge of directly connecting porous SiC ceramics and 2507 duplex stainless steel, this application provides a brazing method for connecting porous SiC ceramics and 2507 duplex stainless steel. By brazing the porous SiC ceramics and 2507 stainless steel, the mechanical connection of core components in traditional skid-mounted equipment is replaced. This fully leverages the corrosion resistance of SiC ceramics and the high strength and good machinability of metals. Utilizing the high strength, good corrosion resistance, and excellent flowability of high-entropy alloy brazing filler metal, the mechanical integrity and functionality of the SiC porous structure can be guaranteed during vacuum brazing. This results in membrane separation equipment capable of stable operation in harsh chemical environments, improving the reliability and efficiency of the separation process, meeting industry requirements for the structural strength of membrane separation equipment, and ensuring long-term stable operation of the membrane separation equipment under complex working conditions.

[0020] like Figure 1 As shown, in a first aspect, embodiments of this application provide a brazing method for connecting porous SiC ceramics to 2507 duplex stainless steel, comprising the following steps: S1. A layer of TiSn alloy brazing filler metal is deposited on the surface of porous SiC ceramic by ultrasonic-assisted brazing, followed by grinding and ultrasonic cleaning to obtain SiC / TiSn composite material. The surface of 2507 duplex stainless steel is polished and then ultrasonically cleaned to obtain pretreated 2507 duplex stainless steel. S2. Pretreated 2507 duplex stainless steel, high-entropy alloy brazing filler metal, and SiC / TiSn composite material are stacked from top to bottom and then vacuum brazed. After the reaction is complete, the mixture is allowed to cool naturally at room temperature.

[0021] In the technical solution of this application embodiment, the present invention first coats a layer of TiSn alloy brazing filler metal onto the surface of porous SiC ceramic. TiSn alloy has good wettability to porous SiC ceramic, which is conducive to the subsequent penetration of high-entropy alloy brazing filler metal into the pores of SiC ceramic and reacting with SiC to generate intermetallic compounds such as ZrC / TiC reaction layer, Fe2Si and Ni2Si, thereby effectively bonding with porous SiC ceramic. On the side of the high-entropy alloy brazing filler metal that is in contact with 2507 duplex stainless steel, an alloy reaction occurs with the stainless steel during vacuum brazing, thereby connecting the porous SiC ceramic and 2507 stainless steel through brazing.

[0022] Furthermore, in some embodiments, the mass fraction of Ti in the TiSn alloy solder is 3-5%.

[0023] In the technical solution of this application embodiment, the main purpose of the TiSn alloy is to embed it into the interior of porous ceramics using ultrasonic action. Sn, as a common solder, has good wettability to ceramics, while Ti, as an active element, can react better with SiC. The mass fraction of Ti is more suitable within the above-mentioned range. If the Ti content is too high, it will reduce the fluidity of the solder, and the molten solder will be unable to be poured out of the crucible for molding during the experiment.

[0024] Furthermore, in some embodiments, the conditions for ultrasonic-assisted brazing in step S1 are: ultrasonic amplitude of 6 μm, ultrasonic frequency of 30~40 kHz, and welding temperature of 300~350℃.

[0025] In the technical solution of this application embodiment, ultrasonic-assisted brazing can improve the wettability of brazing filler metal to difficult-to-wet materials by means of acoustic cavitation effect, and realize the connection of the same and different materials in a lower temperature and atmospheric environment.

[0026] Furthermore, in some embodiments, a pressure of 0.1~0.2 MPa is applied during the ultrasonic-assisted brazing process described in step S1.

[0027] In the technical solution of this application embodiment, during the ultrasonic-assisted brazing process, extrusion penetration is prone to occur, resulting in incomplete wetting of the TiSn alloy brazing filler metal on the surface. To address this, auxiliary pressure is applied to ensure complete wetting of the brazing filler metal.

[0028] Furthermore, in some embodiments, the thickness of the coating after polishing in step S1 is 50~100μm.

[0029] Furthermore, in some embodiments, the surface of 2507 duplex stainless steel is ultrasonically cleaned for 15-20 minutes in step S1.

[0030] In the technical solution of this application embodiment, the surface of 2507 duplex stainless steel is ultrasonically cleaned to remove impurities, oil stains and oxide film on the surface, so as to prevent the formation of brittle oxide phase during the vacuum brazing process, which would affect the welding performance.

[0031] Furthermore, in some embodiments, the TiSn alloy solder is prepared by high-temperature melting of Ti and Sn.

[0032] Furthermore, in some embodiments, the high-entropy alloy solder is selected from TiZrCuNi high-entropy alloy, the composition of which, by mass fraction, includes Ti 35%~39%, Zr 35%~49%, Cu 13%~17%, and Ni 9%~13%.

[0033] In the technical solution of this application embodiment, TiZrCuNi is used as an amorphous filler solder, which has high strength, good corrosion resistance and excellent fluidity. Titanium zirconium is mainly used as an active element and can react with porous ceramics to generate high-toughness metal interlayer compounds. Copper and nickel can play a good role in ceramic surface wettability.

[0034] Furthermore, in some embodiments, the vacuum degree of vacuum brazing in step S2 is 2 × 10⁻⁶. -3 ~5×10 -3 Pa.

[0035] Furthermore, in some embodiments, the heating rate of vacuum brazing in step S2 is: Heat to 350℃ at a rate of 8-10℃ / min and hold for 25 minutes; Then raise the temperature to 800℃ at a rate of 8-10℃ / min and hold for 20 minutes; Continue heating at a rate of 4-5℃ / min to the brazing temperature of 1000-1050℃, hold for 10-20 minutes, and finally cool to room temperature with the furnace.

[0036] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0037] I. Preparation Method Example 1 Step 1: Prepare TiSn alloy brazing filler metal with 3% Ti by high-temperature melting, clean the surface of porous SiC ceramic (6.5mm×5mm×3mm), and plate the surface of porous SiC ceramic with TiSn alloy brazing filler metal using ultrasonic-assisted brazing equipment, applying a pressure of 0.2MPa during the process; Step 2: Use polishing equipment to grind the surface flat and thin it at the same time, with a coating thickness of 80μm. At the same time, grind the surface of 2057 duplex stainless steel (10mm×10mm×3mm). After the substrate is treated, ultrasonically clean it with acetone for 15 minutes. Step 3: Cut 10mm × 10mm high-entropy alloy brazing filler metal (composition: Ti 37.68%, Zr 36.79%, Cu 14.78%, Ni 10.75%). Place the prepared substrate and brazing filler metal in a crucible and put it into a vacuum brazing furnace with a vacuum degree of 2 × 10⁻⁶. - 3The sample was first heated to 350℃ at 8℃ / min and held for 25 min, then heated to 800℃ at 8℃ / min and held for 20 min, and finally heated to 1000℃ at 4℃ / min and held for 15 min. After vacuum brazing, the sample was naturally cooled to room temperature to obtain the sample.

[0038] SEM scanning was performed on the brazed joint of the sample welded in Example 1 to obtain... Figure 2 .from Figure 2 As can be seen, the brazed joint of the sample is well formed, the joint is completely welded, the brazing filler metal penetrates into a uniform width, and there is a light gray discontinuous interface reaction layer. The shear strength measured by the universal testing machine is 19.11 MPa, indicating good welding performance.

[0039] XRD analysis of the brazed joint in Example 1 yielded... Figures 3-4 , Figure 3 The image in the middle shows the XRD patterns of two detection sites on one side of a vacuum-brazed 2057 stainless steel substrate. Figure 4 The middle image shows the XRD patterns of two sites on one side of the vacuum-brazed ceramic substrate. Figures 3-4 It can be seen that the microstructure of the solder layer contains a Ti-rich phase and has overlapping Zr / Sn / Ni elements, forming (Zr,Ti)(Ni,Cu) and (Sn,Ti)(Cu,Ni). The compounds are mainly products of the reaction between SiC and the active elements Zr and Ti.

[0040] Example 2 The difference between Example 2 and Example 1 is that the Ti mass fraction in the TiSn alloy solder is 5%, while the other conditions are the same as in Example 1.

[0041] The brazed joint in Example 2 was well formed, the joint was completely welded, and there was a discontinuous interface reaction layer. The measured shear strength was 16.09 MPa, indicating good welding performance.

[0042] Example 3 The difference between Example 2 and Example 1 lies in the third step: cutting 10mm × 10mm high-entropy alloy brazing filler metal (composition content: Ti 37.68%, Zr 36.79%, Cu 14.78%, Ni 10.75%), placing the treated substrate and brazing filler metal in a crucible and then placing it in a vacuum brazing furnace with a vacuum degree of 2 × 10⁻⁶. -3 MPa, first heat up to 350℃ at 8℃ / min and hold for 25min, then heat up to 800℃ at 8℃ / min and hold for 20min, finally heat up to 1050℃ at 4℃ / min and hold for 25min, then begin vacuum brazing and allow to cool naturally to room temperature to obtain the sample.

[0043] In Example 3, the surface of the joint was completely welded. XRD analysis showed that the silicon carbide substrate contained brittle phases such as (Zr,Ti) / (C,Fe) and the measured strength was 15.12 MPa.

[0044] Comparative Example 1 Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the high-entropy alloy solder (component content: Ti 63.5%, Zr 12.5%, Cu 15%, Ni 9%) was used, while all other conditions were the same as in Example 1.

[0045] In Comparative Example 1, the brazed joint showed complete surface welding, with excess Ti forming Ti5Si3 and TiSi2, both of which are brittle phases. XRD analysis revealed... Figure 5 Excess Ti forms Ti5Si3 and TiSi2 on the substrate surface. Both are brittle phases. The measured shear strength is 8.86 MPa, which is significantly lower than that of Example 1. This indicates that a Ti mass fraction of 35% to 39% in the high-entropy alloy brazing filler metal is more suitable.

[0046] Comparative Example 2 Step 1: Grind the surface of 2057 duplex stainless steel (10mm×10mm×3mm), and then ultrasonically clean it with acetone for 15 minutes after substrate treatment. Step 2: Cut 10mm × 10mm high-entropy alloy brazing filler metal (composition: Ti 37.68%, Zr 36.79%, Cu 14.78%, Ni 10.75%). Place the prepared substrate and brazing filler metal in a crucible and put it into a vacuum brazing furnace with a vacuum degree of 2 × 10⁻⁶. - 3 The sample was first heated to 350℃ at 8℃ / min and held for 25 min, then heated to 800℃ at 8℃ / min and held for 20 min, and finally heated to 1000℃ at 4℃ / min and held for 15 min. After vacuum brazing, the sample was naturally cooled to room temperature to obtain the sample.

[0047] In Comparative Example 2, no stable compounds formed by Zr, Ti, and Si were detected between the solder and the ceramic surface. However, brittle phases (such as TiC / ZrC) formed between the solder and the stainless steel were present, with a measured strength less than 5 MPa. This indicates that brazing with a high-entropy alloy solder without prior wetting treatment with TiSn alloy solder cannot achieve good brazing performance.

[0048] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the TiSn alloy solder was replaced with ZnTi alloy solder (Ti content 3%), while the other conditions were the same as in Example 1.

[0049] In Comparative Example 3, Zn exhibits poor wettability on the porous SiC ceramic surface and does not effectively bond with the porous SiC ceramic. After vacuum brazing, the measured strength is less than 5 MPa.

[0050] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for brazed joining of porous SiC ceramic to 2507 duplex stainless steel, characterized by, The method comprises the following steps: S1, a layer of TiSn alloy filler metal is plated on the surface of porous SiC ceramic as a plating layer by ultrasonic-assisted brazing, and then polishing and ultrasonic cleaning are performed to obtain SiC / TiSn composite material; The surface of 2507 duplex stainless steel is polished and then ultrasonic cleaned to obtain pretreated 2507 duplex stainless steel; S2, the pretreated 2507 duplex stainless steel, high-entropy alloy filler metal and SiC / TiSn composite material are stacked from top to bottom and then vacuum brazing is performed, and the reaction is naturally cooled at room temperature after completion.

2. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The mass fraction of Ti in the TiSn alloy filler metal is 3-5%.

3. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The ultrasonic-assisted brazing in step S1 is performed under the following conditions: ultrasonic amplitude of 6 μm, ultrasonic frequency of 30-40 kHz, and brazing temperature of 300-350℃.

4. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, A pressure of 0.1-0.2 MPa is applied during the ultrasonic-assisted brazing in step S1.

5. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The thickness of the plating layer after polishing in step S1 is 50-100 μm.

6. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The surface of 2507 duplex stainless steel is ultrasonic cleaned for 15-20 min in step S1.

7. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The TiSn alloy filler metal is prepared by high-temperature smelting of Ti and Sn, and the high-temperature smelting is performed by arc smelting under the following conditions: argon environment and temperature of 300-350℃.

8. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The high-entropy alloy filler metal is selected from TiZrCuNi high-entropy alloy, and the components of the TiZrCuNi high-entropy alloy include Ti 35%-39%, Zr 35%-49%, Cu 13%-17%, and Ni 9%-13% by mass fraction.

9. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The vacuum degree of the vacuum brazing in step S2 is 2×10⁻⁶. -3 ~5×10 -3 Pa.

10. The method for brazed joining of porous SiC ceramics to 2507 duplex stainless steel according to claim 1, characterized in that, The temperature rising rate of the vacuum brazing in step S2 is as follows: Rise the temperature to 350℃ at a rate of 8-10℃ / min and keep for 25 min; Rise the temperature to 800℃ at a rate of 8-10℃ / min and keep for 20 min; Continue to rise the temperature to brazing temperature of 1000-1050℃ at a rate of 4-5℃ / min and keep for 10-20 min, and finally cool to room temperature with the furnace.

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