Ceramic and metal brazing method based on self-resistance heating metal foil
By using a graded Joule thermal brazing method with self-resistance heating metal foil, the problems of uneven heat distribution and insufficient stress control in Joule thermal brazing for joining dissimilar materials are solved, achieving high-strength and reliable ceramic-metal bonding.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2026-02-02
- Publication Date
- 2026-05-01
AI Technical Summary
Existing Joule hot brazing methods have difficulty in synergistically controlling interfacial reactions and residual stress when joining materials such as Y2O3-MgO nanocomposite ceramics and TC4 titanium alloys. This results in problems such as uneven heat distribution and insufficient control of heating rate, leading to easy cracking of ceramics and insufficient joint strength.
A graded Joule thermal brazing method using self-resistance heating metal foil is adopted. By controlling the current in graded stages during the preheating and brazing stages, combined with the flexible intermediate layer of the self-resistance heating metal foil, a tough diffusion layer is formed to regulate thermal stress and interfacial reaction.
It effectively solves the thermal shock resistance differences of oxide ceramics, reduces residual thermal stress, avoids the formation of brittle compounds, and improves the strength and reliability of the joint.
Smart Images
Figure CN121948993A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of dissimilar material joining and advanced manufacturing technology. Background Technology
[0002] In the fields of aerospace, nuclear energy, and semiconductor manufacturing, advanced ceramic materials such as Y2O3-MgO nanocomposite ceramics and SiC, due to their excellent high-temperature performance and wave transmission properties, often need to be structurally bonded to lightweight, high-strength metals such as TC4 titanium alloys. However, achieving high-quality bonding between ceramics and titanium alloys faces many challenges:
[0003] First, there is a severe mismatch in thermophysical properties. The coefficient of thermal expansion of ceramics is usually much lower than that of metals. During the long cooling process of traditional vacuum furnace brazing, huge residual thermal stress is easily generated at the interface, which can lead to joint fracture or a significant reduction in strength on the ceramic side.
[0004] Secondly, it is difficult to balance heating efficiency with interfacial reaction. Traditional vacuum furnace brazing uses radiant heating, which requires heating the entire furnace chamber and fixtures, resulting in high energy consumption and long cycles. Prolonged high-temperature holding can cause a transitional reaction between the brazing filler metal and the highly chemically reactive titanium alloy, forming continuous, coarse, brittle intermetallic compounds that significantly weaken the joint toughness.
[0005] Furthermore, there are limitations to existing rapid heating technologies. Although high-energy beam technologies such as laser welding and electron beam welding heat up quickly, the heat input is too concentrated and difficult to distribute evenly in the intermediate layer, which can easily cause localized overheating. More importantly, for oxide ceramics such as Y2O3-MgO, which have poor thermal shock resistance, if a "transient" heating method that cannot precisely control the heating rate is used, the ceramic body is very likely to crack due to the instantaneous and huge thermal shock.
[0006] In recent years, Joule brazing, as a localized rapid heating technology, has alleviated some of the aforementioned problems to a certain extent. It generates resistance heat by directly passing an electric current through the workpiece or intermediate layer, achieving rapid heating and localized heating. This helps reduce the overall heat-affected zone and suppress excessive interfacial reactions, thus providing new possibilities for ceramic-metal bonding.
[0007] However, existing Joule brazing methods still have significant technical drawbacks when applied to joining dissimilar materials such as Y2O3-MgO nanocomposite ceramics and TC4 titanium alloys: First, it is difficult to control the uniformity of current and temperature distribution, especially near the ceramic / metal interface where heat accumulation is likely to occur, which may still lead to local thermal shock damage to the ceramic; Second, existing processes lack the ability to programmatically control the heating rate, holding time, and cooling process, making it difficult to actively regulate the residual stress at the interface while suppressing the formation of brittle compounds.
[0008] Therefore, while existing Joule heating technology offers the advantage of rapid localized heating, it still faces bottlenecks in achieving highly reliable and strong connections between ceramics with poor thermal shock resistance and highly reactive metals, including insufficient controllability and weak stress regulation capabilities. There is an urgent need for a more efficient and stable connection method that, based on rapid Joule heating, further achieves precise control over the heating process, effective suppression of interfacial reactions, and active regulation of the connection stress distribution. Summary of the Invention
[0009] This invention aims to address the problem that existing Joule heating brazing methods have difficulty in synergistically controlling interfacial reactions and residual stress when joining materials such as Y2O3-MgO nano-composite ceramics and TC4 titanium alloys. Therefore, it provides a ceramic-metal brazing method based on self-resistance heating metal foil.
[0010] A ceramic-to-metal brazing method based on self-resistance heating metal foil, comprising the following steps:
[0011] I. Assembly of components to be welded:
[0012] The components are stacked and assembled in the following order: first base material / first solder layer / self-resistance heating metal foil / second solder layer / second base material to obtain the workpiece to be welded.
[0013] II. Applying preload:
[0014] Pre-tightening pressure is applied in the stacking direction of the workpieces to be welded under vacuum conditions or a protective atmosphere to obtain pre-tightened workpieces to be welded;
[0015] III. Graded Joule hot brazing:
[0016] Connect the two ends of the self-resistance heating metal foil in the pre-tightened workpiece to the positive and negative terminals of a DC power supply, respectively. Under vacuum or protective atmosphere, first apply the first stage current to raise the interface peak temperature to 300℃~500℃ and hold it for 5s~30s. Then increase the current to the second stage and use the Joule heat generated by the self-resistance heating metal foil for brazing.
[0017] IV. Cooling:
[0018] The power is stopped, and the molten brazing filler metal is cooled and solidified under pre-tightening pressure to obtain a welded joint, thus completing the ceramic-metal brazing method based on self-resistance heating metal foil.
[0019] The beneficial effects of this invention are:
[0020] 1. The method of this invention abandons the simple "transient impact" and introduces a current-graded heating strategy. By reducing the temperature gradient on the ceramic side through the preheating stage, it effectively solves the problem of poor thermal shock resistance and easy cracking of oxide ceramics such as Y2O3-MgO during rapid welding.
[0021] 2. The method of this invention retains unmelted metal foil as a flexible interlayer at the center of the weld. Its coefficient of thermal expansion is between that of ceramics and titanium alloys, forming a gradient physical transition and significantly reducing residual thermal stress. More importantly, the selected niobium, tantalum, or high-entropy alloy foils can interdiffused with the titanium alloy during welding, forming a ductile diffusion layer dominated by solid solution. This interface layer effectively avoids the formation of continuously distributed brittle intermetallic compound phases, thus completely replacing the inherent brittle interface in traditional joints.
[0022] 3. The method of the present invention utilizes the Joule heating principle of high current and low voltage, with the heat source highly concentrated at the joint interface, resulting in extremely high energy utilization. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the ceramic-metal brazing assembly based on self-resistance heating metal foil of the present invention. 1 is the positive terminal of the power supply, 2 is the first base material, 3 is the brazing filler layer, 4 is the self-resistance heating metal foil, 5 is the second base material, 6 is the negative terminal of the power supply, and 7 is the base.
[0024] Figure 2 SEM images and elemental distribution diagrams of the microstructure of the welded joint interface prepared in Example 1;
[0025] Figure 3 The image shows the SEM morphology and elemental distribution of the microstructure of the welded joint interface prepared in Example 2.
[0026] Figure 4 The diagram shows the room temperature shear strength of the welded joints prepared in Examples 1 and 2. Detailed Implementation
[0027] Specific implementation method one, combined with Figure 1 Detailed explanation: This embodiment describes a ceramic-metal brazing method based on self-resistance heating metal foil, which is carried out according to the following steps:
[0028] I. Assembly of components to be welded:
[0029] The components are stacked and assembled in the following order: first base material / first solder layer / self-resistance heating metal foil / second solder layer / second base material to obtain the workpiece to be welded.
[0030] II. Applying preload:
[0031] Pre-tightening pressure is applied in the stacking direction of the workpieces to be welded under vacuum conditions or a protective atmosphere to obtain pre-tightened workpieces to be welded;
[0032] III. Graded Joule hot brazing:
[0033] Connect the two ends of the self-resistance heating metal foil in the pre-tightened workpiece to the positive and negative terminals of a DC power supply, respectively. Under vacuum or protective atmosphere, first apply the first stage current to raise the interface peak temperature to 300℃~500℃ and hold it for 5s~30s. Then increase the current to the second stage and use the Joule heat generated by the self-resistance heating metal foil for brazing.
[0034] IV. Cooling:
[0035] The power is stopped, and the molten brazing filler metal is cooled and solidified under pre-tightening pressure to obtain a welded joint, thus completing the ceramic-metal brazing method based on self-resistance heating metal foil.
[0036] This specific implementation addresses dissimilar materials such as Y2O3-MgO nanocomposite ceramics and TC4 titanium alloys, which have significantly different coefficients of thermal expansion and are sensitive to thermal shock. It innovatively explores the dual function of high-melting-point metal foil in dissimilar joining, combined with a "graded current control" process: First, as a "controllable in-situ heat source," the resistive characteristics of the metal foil are utilized to generate Joule heat through a high current and low voltage. This is combined with a two-stage heating process of preheating and brazing. In the preheating stage, the first base material is preheated uniformly, reducing the impact of the thermal gradient. In the brazing stage, the current rapidly increases to the second stage, using the Joule heat generated by the self-resisting heating of the metal foil to melt the brazing filler metal on both sides and wet the base material through heat conduction, thus ensuring joining efficiency while preventing ceramic cracking. Second, as a "structural functional layer," the unmelted metal foil remains in the weld after brazing. It utilizes the good solid solution properties with active metals such as titanium (Ti) to form a tough interface, and its matching coefficient of thermal expansion alleviates joint stress.
[0037] The beneficial effects of this specific implementation method are:
[0038] 1. This specific implementation method abandons the simple "transient impact" and introduces a current-graded heating strategy. By reducing the temperature gradient on the ceramic side during the preheating stage, it effectively solves the problem of poor thermal shock resistance and easy cracking of oxide ceramics such as Y2O3-MgO during rapid welding.
[0039] 2. In this specific embodiment, an unmelted metal foil is retained at the center of the weld as a flexible interlayer. Its coefficient of thermal expansion is between that of ceramics and titanium alloys, creating a gradient physical transition and significantly reducing residual thermal stress. More importantly, the selected niobium, tantalum, or high-entropy alloy foils can interdiffused with the titanium alloy during welding, forming a ductile diffusion layer dominated by solid solution. This interface layer effectively avoids the formation of continuously distributed brittle intermetallic compound phases, thus completely replacing the inherent brittle interface in traditional joints.
[0040] 3. The method of this specific implementation utilizes the Joule heating principle of high current and low voltage, with the heat source highly concentrated at the joint interface, resulting in extremely high energy utilization.
[0041] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the two ends of the self-resistance heating metal foil mentioned in step one extend through the workpiece to be welded and serve as electrode connection points. Everything else is the same as in Specific Implementation Method One.
[0042] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the self-resistance heating metal foil mentioned in step one is niobium foil, tantalum foil, molybdenum foil, tungsten foil, vanadium foil, zirconium foil, hafnium foil, titanium alloy foil, nickel-based high-temperature alloy foil, or high-entropy alloy foil; the thickness of the self-resistance heating metal foil mentioned in step one is 0.05mm~0.5mm. Everything else is the same as in Specific Implementation Method One or Two.
[0043] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the first substrate mentioned in step one is Y2O3-MgO nano-composite ceramic; the second substrate mentioned in step one is TC4 titanium alloy. Everything else is the same as in Specific Implementation Methods One to Three.
[0044] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the first and second solder layers mentioned in step one are both Ag-Cu-In-Ti active solder foils, with a thickness of 50μm to 200μm. Everything else is the same as in Specific Implementation Methods One to Four.
[0045] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step two, a preload pressure of 0.5MPa to 5MPa is applied in the stacking direction of the workpieces to be welded. Everything else is the same as in Specific Implementation Methods One to Five.
[0046] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: the protective atmosphere described in steps two and three is argon or helium; the vacuum condition described in steps two and three is a vacuum degree ≤ 1×10⁻⁶. -2 Pa. The rest is the same as in specific embodiments one through six.
[0047] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the DC power supply mentioned in step three is a low-voltage, high-current power supply with an output voltage of 0.5V to 10V. Everything else is the same as in Specific Implementation Methods One to Seven.
[0048] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: in step three, a first-stage current of 50A~300A is first applied to raise the interface peak temperature to 300℃~500℃ and maintain it for 5s~30s. Then, the current is increased to a second-stage current of 200A~1000A, raising the interface peak temperature to 750℃~950℃. Under the condition of 750℃~950℃, Joule heating generated by the self-resistance heating metal foil is used for brazing for 5s~60s. Everything else is the same as in Specific Implementation Methods One to Eight.
[0049] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the weld area of the welded joint described in step four has a layered structure, with an unmelted self-heating metal foil at the center. Everything else is the same as in Specific Implementation Methods One to Nine.
[0050] The beneficial effects of the present invention are verified using the following embodiments:
[0051] Example 1:
[0052] A ceramic-to-metal brazing method based on self-resistance heating metal foil, comprising the following steps:
[0053] I. Assembly of components to be welded:
[0054] The components are stacked and assembled in the following order: first base material / first solder layer / self-resistance heating metal foil / second solder layer / second base material to obtain the workpiece to be welded.
[0055] II. Applying preload:
[0056] At a vacuum degree of 5×10 -3 Under vacuum conditions of Pa, an insulating ceramic pressure head is used to apply a pre-tightening pressure of 1 MPa in the stacking direction of the workpiece to be welded, thereby obtaining a pre-tightened workpiece to be welded;
[0057] III. Graded Joule hot brazing:
[0058] Using water-cooled copper electrodes, the two ends of the self-resistive heating metal foil in the pre-tightened workpiece are connected to the positive and negative terminals of a DC power supply, respectively, under a vacuum of 5×10⁻⁶. -3 Under vacuum conditions of Pa, a first-stage current of 150A is first applied to raise the interface peak temperature to 400℃ and hold it for 20s. Then, the current is increased to the second-stage current of 380A to raise the interface peak temperature to 880℃. Under the condition of interface peak temperature of 880℃, Joule heating generated by the self-resistance heating metal foil is used for 10s for brazing.
[0059] The DC power supply is a low-voltage, high-current power supply with an output voltage of 3V;
[0060] IV. Cooling:
[0061] The power is stopped, and the molten brazing filler metal is cooled and solidified under pre-tightening pressure to obtain a welded joint, thus completing the ceramic-metal brazing method based on self-resistance heating metal foil.
[0062] The self-resistance heating metal foil mentioned in step one extends through both ends of the workpiece to be welded and serves as electrode connection points.
[0063] The self-resistance heating metal foil mentioned in step one is niobium foil with a purity of 99.95%; the thickness of the self-resistance heating metal foil mentioned in step one is 0.1 mm, and the size is 10 mm × 60 mm.
[0064] The first base material mentioned in step one is Y2O3-MgO nano-multiphase ceramic with a size of 10mm×10mm×3mm; the second base material mentioned in step one is TC4 titanium alloy with a size of 10mm×10mm×3mm; and both the first and second base materials are polished with 2000# sandpaper and ultrasonically cleaned with acetone.
[0065] The first and second solder layers mentioned in step one are both Ag-Cu-In-Ti active solder foils with a thickness of 100μm (composition wt.%: 44Ag-29Cu-24In-3Ti).
[0066] Example 2: This example differs from Example 1 in that: the self-resistance heating metal foil mentioned in step 1 is a molybdenum foil with a purity of 99.95%; in step 3, the vacuum degree is 5×10 -3 Under vacuum conditions of Pa, a first-stage current of 220A was first applied to raise the interface peak temperature to 420°C and maintain it for 15s. Then, the current was increased to a second-stage current of 600A to raise the interface peak temperature to 900°C. At a temperature of 900°C, Joule heating of the metal foil was performed for 10s using the self-resistance heating element. The rest was the same as in Example 1.
[0067] Figure 2 The images show the SEM morphology and elemental distribution of the weld joint interface prepared in Example 1. As can be seen from the images, the weld is fully formed and free of cracks. The central niobium foil remains intact, forming a dense solid solution diffusion layer with the two sides.
[0068] Figure 3 The images show the SEM morphology and elemental distribution of the weld joint interface prepared in Example 2. As can be seen from the figures, the molybdenum foil did not soften or deform at high temperatures, acting as a rigid framework to support the weld. Furthermore, the Ti element in the Ag-Cu-In-Ti solder reacted chemically with the molybdenum foil, forming a discontinuous Ti-Mo solid solution diffusion layer at the interface, resulting in a tight interfacial bond.
[0069] Figure 4The figures show the room temperature shear strength of the welded joints prepared in Examples 1 and 2. The tests were conducted using a universal testing machine with a loading rate of 0.5 mm / min. The room temperature shear strength of the joint in Example 1 was 65 MPa. The room temperature shear strength of the joint in Example 2 was 62 MPa.
Claims
1. A method for ceramic-metal brazing based on self-resistance heating metal foil, characterized in that... It is done in the following steps: I. Assembly of components to be welded: The components are stacked and assembled in the following order: first base material / first solder layer / self-resistance heating metal foil / second solder layer / second base material to obtain the workpiece to be welded. II. Applying preload: Pre-tightening pressure is applied in the stacking direction of the workpieces to be welded under vacuum conditions or a protective atmosphere to obtain pre-tightened workpieces to be welded; III. Graded Joule hot brazing: Connect the two ends of the self-resistance heating metal foil in the pre-tightened workpiece to the positive and negative terminals of a DC power supply, respectively. Under vacuum or protective atmosphere, first apply the first stage current to raise the interface peak temperature to 300℃~500℃ and hold it for 5s~30s. Then increase the current to the second stage and use the Joule heat generated by the self-resistance heating metal foil for brazing. IV. Cooling: The power is stopped, and the molten brazing filler metal is cooled and solidified under pre-tightening pressure to obtain a welded joint, thus completing the ceramic-metal brazing method based on self-resistance heating metal foil.
2. The ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... The self-resistance heating metal foil mentioned in step one extends through both ends of the workpiece to be welded and serves as electrode connection points.
3. The ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... The self-resistance heating metal foil mentioned in step one is niobium foil, tantalum foil, molybdenum foil, tungsten foil, vanadium foil, zirconium foil, hafnium foil, titanium alloy foil, nickel-based high-temperature alloy foil, or high-entropy alloy foil; the thickness of the self-resistance heating metal foil mentioned in step one is 0.05mm~0.5mm.
4. The ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... The first substrate mentioned in step one is Y2O3-MgO nano-composite ceramic; the second substrate mentioned in step one is TC4 titanium alloy.
5. A ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... The first and second solder layers mentioned in step one are both Ag-Cu-In-Ti active solder foils with a thickness of 50μm~200μm.
6. The ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... In step two, a preload pressure of 0.5 MPa to 5 MPa is applied in the stacking direction of the workpieces to be welded.
7. A ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... The protective atmosphere described in steps two and three is argon or helium; the vacuum condition described in steps two and three is a vacuum degree ≤ 1 × 10⁻⁶. -2 Pa.
8. The ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... The DC power supply mentioned in step three is a low-voltage, high-current power supply with an output voltage of 0.5V to 10V.
9. A ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... In step three, a first-stage current of 50A~300A is first applied to raise the interface peak temperature to 300℃~500℃ and hold it for 5s~30s. Then, the current is increased to the second-stage current of 200A~1000A to raise the interface peak temperature to 750℃~950℃. Under the condition of 750℃~950℃, Joule heating generated by the self-resistance heating metal foil is used for brazing for 5s~60s.
10. A ceramic-metal brazing method based on self-resistance heating metal foil according to claim 1, characterized in that... The weld area of the welded joint described in step four has a layered structure with an unmelted self-heating metal foil at the center.