A composite interlayer for low-activation steel / Ti3SiC2 ceramic connectors and its application method

Abstract

The application discloses a composite interlayer for a low-activation steel / Ti3SiC2 ceramic connecting piece and a use method, wherein the composite interlayer comprises metal I, an intermediate metal layer and metal II arranged in sequence from top to bottom; the metal I and the metal II are both selected from titanium or zirconium, and the thicknesses of the metal I and the metal II are both 10-50 micrometers; the intermediate metal layer is copper or a copper alloy, and the thickness is 0.4-0.6 mm; and the application further discloses a transient liquid phase connecting method for the composite interlayer for the low-activation steel / Ti3SiC2 ceramic connecting piece. The composite interlayer in the application does not contain a high-activation element, welding is carried out at a normalizing heat treatment temperature lower than that of the low-activation steel, and a high-strength high-temperature connecting piece expected to be applied to a nuclear environment is formed.

Description

Technical Field

[0001] This invention relates to the field of ceramic-metal welding technology, and more specifically to a composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors and its application method. Background Technology

[0002] Low-activation steel is a structural material used in nuclear reactors, possessing excellent radiation resistance and creep resistance, along with good strength, toughness, and weldability. These superior properties make it the preferred structural material for the International Thermonuclear Experimental Reactor (ITER) and demonstration reactors. However, the maximum service temperature of low-activation steel is around 550°C, at which point its mechanical properties significantly decrease. Therefore, achieving high-quality bonding between low-activation steel and other high-temperature resistant and radiation-resistant materials, and using it as an integral component, can fully leverage the advantages of both materials and increase the service temperature of the low-activation steel.

[0003] Ti3SiC2 ceramic is a typical MAX phase ceramic with a unique layered structure and a variety of excellent properties, such as good radiation resistance, high-temperature stability, and excellent corrosion and oxidation resistance, making it a candidate material for core structures. Therefore, studying the bonding between low-activation steel and Ti3SiC2 ceramic is of great significance for improving the service temperature and service life of low-activation steel and expanding the application value of Ti3SiC2 ceramic.

[0004] Studies have shown that brazing, diffusion brazing, and contact reaction brazing can be used to join Ti3SiC2 ceramics with metals. Researchers have achieved vacuum brazing of Ti3SiC2 ceramics with copper or Ti2AlNb titanium alloys using Ag-Cu-Ti or Ag-Cu brazing filler metals. However, the melting point of Ag-Cu-Ti and Ag-Cu filler metals is only 780℃, resulting in a relatively low operating temperature for the joined parts. Furthermore, Ag is a highly activating element and cannot be used in a nuclear environment. On the other hand, researchers have also used diffusion bonding technology to join NiTi alloys with Ti3SiC2 ceramics, but effective bonding is only achieved at diffusion welding temperatures above 1100℃. In addition, researchers have also explored diffusion welding connections between Ti3SiC2 and Ni, Ti3SiC2 and Fe, Ti3SiC2 and W, and Ti3SiC2 and SUS304 stainless steel. However, diffusion welding requires high bonding pressure (tens of MPa), which limits the shape and size of the joined parts. Moreover, a Ni interlayer is often used as a transition material in the diffusion welding process, and Ni is also a highly activating element. To avoid applying excessive bonding pressure and lowering the bonding temperature during welding, researchers have used contact reaction brazing to join TC4 alloy and Ti3SiC2 ceramic. However, contact reaction brazing requires strict control of material type and thickness; otherwise, the joint strength will decrease sharply when a continuous intermetallic compound layer appears.

[0005] Currently, there are no research reports on the bonding of low-activation steel with Ti3SiC2 ceramics. In the bonding process of low-activation steel and Ti3SiC2 ceramics, avoiding the use of highly activating elements (such as Ag and Ni) and applying excessive welding pressure during the welding process, while simultaneously reducing the bonding temperature (if the temperature exceeds the normalizing heat treatment temperature of low-activation steel (980℃), its performance will drastically decrease) and obtaining a high-temperature resistant joint, has become a pressing problem for technicians in the welding field, especially in the field of nuclear materials welding. Summary of the Invention

[0006] In view of this, the present invention proposes a composite interlayer and welding process for transient liquid-phase bonding of low-activation steel and Ti3SiC2 ceramic for nuclear environment applications. The present invention can obtain high-strength low-activation steel / Ti3SiC2 ceramic connectors at relatively low welding temperatures. The composite interlayer does not contain highly activating elements such as Ag and Ni, and the microstructure of the composite interlayer is easy to control and has low preparation cost.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors, the composite intermediate layer comprising metal I, an intermediate metal layer and metal II arranged sequentially from top to bottom;

[0009] Wherein, both metal I and metal II are selected from titanium or both metal I and metal II are selected from zirconium;

[0010] The intermediate metal layer is selected from copper, chromium-zirconium-copper alloy, or tungsten-copper alloy.

[0011] Preferably, the intermediate metal layer is selected from chromium-zirconium-copper alloy or tungsten-copper alloy.

[0012] Preferably, the thickness of metal I and metal II is the same, both being 10–50 μm; the thickness of the intermediate metal layer is 0.4–0.6 mm.

[0013] The advantages of adopting the above technical solution are: the welding material does not contain highly activating elements. Simultaneously, by constructing a metal / copper (alloy) / metal composite intermediate layer, titanium or zirconium reacts with copper (alloy) at the eutectic temperature during welding to form a liquid phase, promoting diffusion and bonding between the weld layer and the welded material (low-activation steel, Ti3SiC2 ceramic) with almost no external pressure. Furthermore, after welding, titanium or zirconium forms a compound with Cu that has a high melting point, resulting in a joint with a high operating temperature.

[0014] Another object of the present invention is to provide a method of using a composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors, characterized by comprising the following steps:

[0015] (1) Grind and polish the surfaces to be welded, including low-activation steel, Ti3SiC2 ceramic, metal I, metal II and intermediate metal layer, and then perform ultrasonic cleaning and drying.

[0016] (2) The low-activation steel, metal I, intermediate metal layer, metal II and Ti3SiC2 ceramic obtained in step (1) are combined in sequence, placed in a mold, and then sent to a vacuum furnace for instantaneous liquid phase connection to obtain the low-activation steel / Ti3SiC2 connector.

[0017] Preferably, in step (1), the grinding and polishing requires a surface roughness Ra ≤ 10 μm.

[0018] Preferably, in step (1), the solvent used for ultrasonic cleaning is acetone or alcohol.

[0019] Preferably, the ultrasonic cleaning time in step (1) is 3 to 15 minutes.

[0020] Preferably, the mold in step (2) is a graphite mold.

[0021] Preferably, the process parameters for the instantaneous liquid phase connection are: vacuum degree ≤ 5 × 10⁻⁶. -2Pa, welding temperature 950~980℃, holding time 10~30min, welding pressure 10 -5 ~10 -3 MPa, heating rate of 10-20℃ / min, cooling rate of 5-10℃ / min to 300℃, and then cooling to room temperature with the furnace.

[0022] By constructing an active metal / copper (alloy) / active metal composite interlayer, titanium or zirconium reacts with copper (alloy) at the eutectic temperature (approximately 885℃) during welding to form a liquid phase. This requires very little (almost no) bonding pressure, enabling diffusion and bonding between the weld layer and the interface between the weld layer and the low-activation steel and Ti3SiC2 ceramic. The welding temperature is lower than the normalizing heat treatment temperature of 980℃ for the low-activation steel, thus not adversely affecting its properties. Furthermore, after welding, titanium or zirconium forms a compound with Cu that has a high melting point (above 950℃), resulting in a joint with a high service temperature.

[0023] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The metal / copper (alloy) / metal composite intermediate layer does not contain highly active elements such as Ag and Ni.

[0025] (2) By using a metal / copper (alloy) / metal composite intermediate layer to connect low-activation steel and Ti3SiC2 ceramic, a liquid phase can be formed at the eutectic temperature of copper (alloy) and titanium or zirconium. Due to the presence of the liquid phase, the diffusion and bonding of the weld layer to the interface of low-activation steel and Ti3SiC2 ceramic can be achieved with very low (almost no pressure) bonding pressure.

[0026] (3) The welding temperature is lower than the normalizing heat treatment temperature of low activation steel, which will not have an adverse effect on the performance of low activation steel.

[0027] (4) Because the microstructure of the joint can be easily controlled by adjusting the thickness of each layer in the composite intermediate layer, without having to change the composition of the welding material by using the traditional method of melting and preparing the brazing filler metal, the present invention has the advantages of flexible operation and low cost.

[0028] (5) Titanium or zirconium forms compounds with Cu with high melting points (melting point above 950℃), thus low-activation steel / Ti3SiC2 ceramic joints have good prospects for high-temperature applications. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 A schematic diagram of a low-activation steel / Ti3SiC2 ceramic connector structure fabricated using the composite intermediate layer described in this invention.

[0031] Figure 2 The image shows a scanning electron microscope (SEM) image of the connector obtained in Example 1 of this invention. It can be seen from the image that the connection interface is well bonded and no welding defects were found.

[0032] Figure 3 The image shows a scanning electron microscope (SEM) image of the connector obtained in Example 2 of this invention. It can be seen from the image that the connection interface is well bonded and no welding defects were found.

[0033] Figure 4 The image shows a scanning electron microscope (SEM) image of the connector obtained in Example 4 of this invention. It can be seen from the image that the connection interface is well bonded and no welding defects were found.

[0034] Figure 5 The image shows a scanning electron microscope (SEM) image of the connector obtained in Example 6 of this invention. It can be seen from the image that the connection interface is well bonded and no welding defects were found.

[0035] Figure 6 The image shows a scanning electron microscope (SEM) image of the connector obtained in Example 7 of this invention. It can be seen from the image that the connection interface is well bonded and no welding defects were found. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] A method for instantaneous liquid-phase bonding of low-activation steel / Ti3SiC2 ceramic connectors includes the following steps:

[0039] (1) Cut the low-activation steel into blocks of 8mm×8mm×8mm, cut the Ti3SiC2 ceramic matrix into blocks of 5mm×8mm×8mm, the thickness of the pure Ti foil is 20μm, and the thickness of the Cu sheet is 500μm.

[0040] (2) Grind and polish the surfaces of low-activation steel, pure Ti foil, copper sheet, and Ti3SiC2 ceramic to be welded until the surface roughness Ra≤10μm;

[0041] (3) Place the low-activation steel, pure Ti foil, copper sheet and Ti3SiC2 ceramic into acetone in sequence for ultrasonic cleaning for 15 minutes, and then blow dry for later use.

[0042] (4) Assemble the materials in the following order: low-activation steel, pure Ti foil, copper sheet, pure Ti foil, and Ti3SiC2 ceramic. Then place the assembly in a graphite mold. Place the graphite mold containing the sample to be welded into a vacuum tube furnace for instantaneous liquid-phase bonding. The heating rate is 10℃ / min, and the vacuum degree is ≤10℃. -2 Pa, welding pressure is 10 -4 The welding temperature was 950℃, and the temperature was held for 30 minutes. Then, the temperature was reduced to 300℃ at a rate of 5℃ / min and cooled to room temperature in the furnace to obtain a low-activation steel / Ti / Cu / Ti / Ti3SiC2 ceramic connector.

[0043] Example 2

[0044] The instantaneous liquid phase connection method for low-activation steel / Ti3SiC2 ceramic connectors differs from Example 1 in that the instantaneous liquid phase connection heat preservation time is 20 min.

[0045] Example 3

[0046] The instantaneous liquid phase connection method for low-activation steel / Ti3SiC2 ceramic connectors differs from Example 1 in that the instantaneous liquid phase connection heat preservation time is 10 min.

[0047] Example 4

[0048] A method for instantaneous liquid phase bonding of low-activation steel / Ti3SiC2 connectors includes the following steps:

[0049] (1) Cut the low-activation steel into blocks of 8mm×8mm×8mm, cut the Ti3SiC2 ceramic matrix into blocks of 5mm×8mm×8mm, the thickness of the pure Zr foil is 50μm, and the thickness of the Cu sheet is 500μm.

[0050] (2) Grind and polish the surfaces to be welded, such as low-activation steel, pure Zr foil, copper sheet, and Ti3SiC2 ceramic, until the surface roughness Ra≤10μm;

[0051] (3) Place the low-activation steel, pure Zr foil, copper sheet and Ti3SiC2 ceramic into acetone in sequence for ultrasonic cleaning for 15 minutes, and then dry them for later use.

[0052] (4) The materials are assembled in the following order: low-activation steel, pure Zr foil, copper sheet, pure Zr foil, and Ti3SiC2 ceramic. This assembly is then placed in a graphite mold. The graphite mold containing the sample to be welded is placed in a vacuum tube furnace for instantaneous liquid-phase bonding. The heating rate is 10℃ / min, and the vacuum degree is ≤10℃. -2 Pa, welding pressure is 10 -4 The welding temperature was 975℃, and the temperature was held for 20 minutes. Then, the temperature was reduced to 300℃ at a rate of 5℃ / min and cooled to room temperature in the furnace to obtain a low-activation steel / Zr / Cu / Zr / Ti3SiC2 ceramic connector.

[0053] Example 5

[0054] The instantaneous liquid phase bonding method for low-activation steel / Ti3SiC2 ceramic connectors differs from Example 4 in that the instantaneous liquid phase bonding temperature is 950°C.

[0055] Example 6

[0056] A method for instantaneous liquid phase bonding of low-activation steel / Ti3SiC2 connectors includes the following steps:

[0057] (1) Cut the low-activation steel into blocks of 8mm×8mm×8mm, cut the Ti3SiC2 ceramic matrix into blocks of 5mm×8mm×8mm, the pure Zr foil has a thickness of 50μm, and the copper chromium zirconium (CuCrZr) sheet has a thickness of 500μm.

[0058] (2) Grind and polish the surfaces to be welded, such as low-activation steel, pure Zr foil, CuCrZr sheet, and Ti3SiC2 ceramic, until the surface roughness Ra≤10μm;

[0059] (3) Place the low-activation steel, pure Zr foil, CuCrZr sheet and Ti3SiC2 ceramic into acetone in sequence for ultrasonic cleaning for 15 min, and then blow dry for later use.

[0060] (4) The materials are assembled in the following order: low-activation steel, pure Zr foil, CuCrZr sheet, pure Zr foil, and Ti3SiC2 ceramic. This assembly is then placed in a graphite mold. The graphite mold containing the sample to be welded is placed in a vacuum tube furnace for instantaneous liquid-phase bonding. The heating rate is 10℃ / min, and the vacuum degree is ≤10℃. -2 Pa, welding pressure is 10 -4The welding temperature was 950℃, and the temperature was held for 20 minutes. Then, the temperature was reduced to 300℃ at a rate of 5℃ / min, and the furnace was cooled to room temperature to obtain a low-activation steel / Zr / CuCrZr / Zr / Ti3SiC2 ceramic connector.

[0061] Example 7

[0062] The instantaneous liquid phase bonding method for low-activation steel / Ti3SiC2 ceramic connectors differs from Example 6 in that copper chromium zirconium (CuCrZr) is replaced with tungsten copper (Cu-15W) alloy.

[0063] Comparative Example 1

[0064] The instantaneous liquid phase bonding method for low-activation steel / Ti3SiC2 ceramic connectors differs from Example 1 in that the Ti foil thickness is 100 μm.

[0065] Comparative Example 2

[0066] The instantaneous liquid phase bonding method for low-activation steel / Ti3SiC2 ceramic connectors differs from Example 5 in that the Zr foil thickness is 100 μm.

[0067] Performance testing

[0068] To compare and analyze the joint strength of low-activation steel / Ti3SiC2 ceramic connectors under different processes, a three-point bending test was conducted on the instantaneous liquid-phase connection joints of low-activation steel / Ti3SiC2 ceramic connectors using a mechanical testing machine to test the room temperature bending strength of the specimens. Three specimens were selected for each group for the bending test, and the bending strength was the average of the three specimen strengths. The bending strength data of the welded joints obtained in Examples 1-7 and Comparative Examples 1-2 are shown in Table 1 below:

[0069] Table 1. Bending strength test results of the low-activation steel / Ti3SiC2 ceramic instantaneous liquid phase bonded joint.

[0070]

[0071]

[0072] The data in the table above shows that the bending strength of the connector obtained using the method described in this invention is significantly higher than that obtained using the comparative method. The results also indicate that when the Ti or Zr foil thickness is too thick, excessive intermetallic compounds are formed in the joint, causing a decrease in joint strength. Therefore, it is essential to control the thickness of the Ti or Zr foil.

[0073] This invention constructs a metal / copper (alloy) / metal composite interlayer. This composite interlayer does not contain highly activating elements. During welding, titanium or zirconium reacts with Cu to form a liquid phase. The welding temperature is lower than the normalizing heat treatment temperature of 980°C for low-activation steel, thus not adversely affecting the performance of the low-activation steel. Simultaneously, due to the presence of the liquid phase at the joint interface during welding, diffusion and bonding between the weld layer and the low-activation steel and Ti3SiC2 ceramic interface can be achieved with very low (almost no pressure) bonding pressure. Furthermore, after welding, titanium or zirconium forms a compound with Cu that has a high melting point (above 950°C), thus the low-activation steel / Ti3SiC2 ceramic joint has good prospects for high-temperature applications.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0075] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of using a composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors, characterized in that, The composite intermediate layer comprises metal I, an intermediate metal layer, and metal II arranged sequentially from top to bottom; Wherein, both metal I and metal II are selected from titanium or both metal I and metal II are selected from zirconium; The intermediate metal layer is selected from chromium-zirconium-copper alloy or tungsten-copper alloy; The thickness of metal I and metal II is the same, both ranging from 10 to 50 μm; the thickness of the intermediate metal layer is 0.4 to 0.6 mm. The usage method includes the following steps: (1) Grind and polish the surfaces to be welded, including low-activation steel, Ti3SiC2 ceramic, metal I, metal II and intermediate metal layer, and then perform ultrasonic cleaning and drying. (2) The low-activation steel, metal I, intermediate metal layer, metal II and Ti3SiC2 ceramic obtained in step (1) are combined in sequence, placed in a mold, and then sent to a vacuum furnace for instantaneous liquid-phase bonding to obtain a low-activation steel / Ti3SiC2 connector; the process parameters for the instantaneous liquid-phase bonding are: vacuum degree ≤ 5×10 -2 Pa, welding temperature 950~980℃, holding time 10~30min, welding pressure 10 -5 ~10 -3 MPa, heating rate of 10~20℃ / min, cooling rate of 5~10℃ / min to 300℃, and then cooling to room temperature with the furnace.

2. The method of using the composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors according to claim 1, characterized in that, In step (1), the grinding and polishing requires a surface roughness Ra ≤ 10 μm.

3. The method of using the composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors according to claim 1, characterized in that, In step (1), the solvent used for ultrasonic cleaning is acetone or alcohol.

4. The method of using a composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors according to claim 1, characterized in that, The ultrasonic cleaning time in step (1) is 3~15 min.

5. The method of using a composite intermediate layer for low-activation steel / Ti3SiC2 ceramic connectors according to claim 1, characterized in that, The mold mentioned in step (2) is a graphite mold.

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