A method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation

Abstract

This invention belongs to the technical field of heterogeneous materials, specifically relating to a method for joining ceramic / metal heterogeneous materials based on thermal-shape synergistic regulation. This invention utilizes a dual mechanism of shape regulation and thermal regulation: microtexture enhances solder wettability, and optimized stress field through uniform or progressive distribution alleviates thermal mismatch effects; a negative pressure environment combined with precise laser parameters forms a uniform finger-shaped molten pool, suppressing excessive growth of intermetallic compounds and microcracks caused by temperature gradients, thus achieving synergistic optimization of interfacial metallurgical reactions and thermal stress. This method significantly improves the connection strength and sealing performance between ceramics and metals such as copper, titanium alloys, and stainless steel, and is suitable for manufacturing three-dimensional complex components in aerospace and electronic devices.

Description

Technical Field

[0001] This invention belongs to the technical field of heterogeneous materials, specifically relating to a method for joining ceramic / metal heterogeneous materials based on thermal-form synergistic regulation. Background Technology

[0002] With the continuous improvement of lightweight, high-temperature resistance, and corrosion resistance of structural components in high-end equipment, ceramic / metal composite components have become a research and application hotspot due to their combination of the high hardness and high-temperature stability of ceramics and the high toughness and good electrical and thermal conductivity of metals. However, ceramics and metals have significant differences in thermal expansion coefficients, chemical activity, and wettability. Traditional brazing processes often require the introduction of multiple transition interfaces or are carried out under high temperature and high pressure conditions, resulting in complex process flows, limited connection strength, and difficulty in meeting the stringent requirements for sealing and reliability of complex three-dimensional components.

[0003] In recent years, laser welding has become an important development direction for future manufacturing due to its high efficiency, precision, environmental friendliness, and flexibility. Existing laser brazing technology achieves reliable connections by precisely controlling energy input and relying on heat conduction mechanisms to melt the filler metal and wet it along a preset path. This method combines the advantages of brazing and laser welding, avoiding the severe interfacial reactions caused by direct laser irradiation of ceramics while fully leveraging the high efficiency and morphology adaptability of laser processing, demonstrating broad application prospects in joining ceramic / metal heterogeneous materials.

[0004] However, traditional laser brazing technology still faces several technical challenges in practical applications. First, the laser creates a non-uniform temperature field along the thickness direction, with significant energy gradient attenuation. This results in insufficient wetting ability of the brazing filler metal during rapid heating and cooling, easily leading to localized incomplete weld defects. Second, the temperature gradient induces excessive growth of intermetallic compounds (IMCs) in the high-temperature region, forming a brittle layer that easily causes joint cracking; while the low-temperature region shows insufficient reaction, resulting in weak interfacial bonding. Third, the non-uniformity of the thermal field exacerbates the thermal expansion mismatch effect, inducing microcracks and severely affecting the reliability and mechanical properties of the joint.

[0005] Therefore, it is urgent to explore and construct a novel laser connection method with the ability to uniformly control the thermal field in order to achieve high-quality and high-reliability connection of ceramic / metal components. Summary of the Invention

[0006] The purpose of this invention is to provide a method for joining ceramic / metal heterogeneous materials based on thermal-form synergistic regulation, addressing the bottleneck problems in ceramic / metal joining, such as poor interfacial wettability, thermal stress concentration, difficulty in controlling interfacial structure, and insufficient adaptability of the method structure.

[0007] By introducing a negative pressure environment and a thermo-shape synergistic control design of surface microtexture during laser brazing, the temperature gradient at the bonding interface is effectively reduced. Furthermore, through precise parameter control, the interface wettability, thermal stress, and microstructure uniformity are synergistically improved, resulting in high-quality bonding. This technology can be applied to the manufacture of ceramic / metal composite structures in aerospace, new energy equipment, electronic device packaging, and biomedical implants.

[0008] The core innovation of this invention lies in the synergistic effect of shape control and thermal control: microtexture enhances the wettability of the solder, and optimizes the stress field through uniform or progressive distribution, mitigating thermal mismatch effects; a negative pressure environment combined with precise laser parameters forms a uniform finger-shaped molten pool, suppressing excessive growth of intermetallic compounds and microcracks caused by temperature gradients, thus achieving synergistic optimization of interfacial metallurgical reactions and thermal stress. This method significantly improves the connection strength and sealing performance between ceramics and metals such as copper, titanium alloys, and stainless steel, and is suitable for manufacturing three-dimensional complex components in aerospace and electronic devices.

[0009] The specific technical solution is as follows: A method for joining ceramic / metal heteromaterials based on thermal-shape synergistic regulation includes the following steps: (1) Prepare uniformly distributed or progressively distributed surface microtextures on the ceramic surface to be joined; The preparation of the surface microtexture is mainly based on precision laser processing, and the laser used can be any one of nanosecond laser, picosecond laser or femtosecond laser.

[0010] Based on traditional laser processing, the gas environment of laser processing can be controlled, such as negative pressure environment, argon environment, nitrogen environment, etc., to achieve the control of the physical and chemical properties of the processed surface.

[0011] Based on traditional laser processing, the liquid environment of laser processing can be controlled, such as deionized water, organic solvents, acidic solutions, and alkaline solutions, to achieve synergistic control of surface morphology and surface function.

[0012] (2) Assemble the ceramic and the metal to be welded together, and pre-place the brazing filler metal within a gap of 30~100μm to obtain the assembly; the thickness of the selected brazing filler metal is matched with the gap.

[0013] (3) Place the assembly in a negative pressure environment of 10. -2 ~10 2 In the negative pressure chamber of Pa.

[0014] When the thickness of the metal to be welded is 0.5mm ≤ 1.5mm, the negative pressure is 1~10. 2 Pa; When the thickness of the metal to be welded is 1.5mm < 3mm, the negative pressure is 10. -2 ~1Pa.

[0015] The negative pressure environment is constructed through an external negative pressure chamber, which is mainly achieved by drawing negative pressure with a negative pressure pump. The airflow can be stabilized by the layout of the air extraction and dust removal in the negative pressure chamber. The location of the air extraction port and dust removal port for drawing negative pressure needs to be combined with the specific dimensions of the chamber to conduct flow field numerical simulation to ensure the stability of the airflow inside the chamber and the uniformity of the local negative pressure environment in the area to be welded.

[0016] Preferably, the air extraction port for creating negative pressure can be placed 5-20cm from the bottom of the chamber, and the dust removal port can be placed 3-8cm from the top of the chamber, with both ports located on the same side or both sides of the chamber. The negative pressure environment is equipped with a certain dust removal function to prevent metal vapor or dust from suspending inside the chamber or adhering to the light-transmitting lens, thus affecting the transmission of light.

[0017] The negative pressure chamber can be constructed of metallic or translucent non-metallic materials, with a wall thickness of 3-10 mm. The pressure can be measured using a negative pressure sensor installed inside the chamber, and the pressure inside the chamber can be displayed in real time via a digital display.

[0018] (4) Adjust the laser to a suitable position so that the center of its spot is offset to the metal side, and use negative defocusing for welding to form a uniform finger-shaped molten pool. The laser can be any of a fiber laser, semiconductor laser, or CO2 laser. Its spot energy characteristics can be any of a Gaussian laser, multi-beam laser, ring-core mode tunable laser, or oscillating laser.

[0019] The laser power is 2000~3000W, the welding speed is 1~2m / min, and the distance between the laser spot and the brazing filler metal is 0.3~3mm; the defocusing amount is ≤1 / 2 of the thickness of the metal plate to ensure the uniformity of the thermal field distribution at the joint interface.

[0020] Preferably, the defocusing amount is -2mm to +2mm.

[0021] The laser head can be placed inside the chamber or outside the chamber, with a light-transmitting lens reserved on the top of the chamber, and the lens transmittance is not less than 99%.

[0022] When the thermal conductivity of the metal to be soldered is below 15 W / (m·K), the distance between the solder spot and the brazing filler metal is 0.3~1 mm. When the thermal conductivity of the metal to be soldered is above 15 W / (m·K), the distance between the solder spot and the brazing filler metal is 1~3 mm.

[0023] In this invention, the ceramic / metal heterostructure connection method based on thermal-form synergistic regulation is described in step (1), where the ceramic is any one of oxide ceramics, carbide ceramics, nitride ceramics, etc.

[0024] The ceramic can be either transparent or opaque.

[0025] In this invention, the ceramic / metal heterostructure joining method based on thermal-form synergistic regulation has a ceramic thickness of 0.5~3mm in step (1); the thickness of the ceramic is consistent with the thickness of the metal to be welded.

[0026] In this invention, the ceramic / metal heterostructure joining method based on thermal-form synergistic regulation, in step (1), the uniformly distributed surface microtexture is equally spaced, and its microtexture period is 0.1~0.3mm. The specific values ​​can be optimized through numerical simulation of joint stress.

[0027] In this invention, the ceramic / metal heterostructure joining method based on thermal-form synergistic regulation has a progressively distributed surface microtexture in step (1) that is not equally spaced. The microtexture spacing in the top region of the joint is 0.05~0.15mm, and the microtexture spacing in the bottom region of the joint is 0.15~0.3mm. The specific values ​​can be optimized through numerical simulation of joint stress.

[0028] In this invention, the ceramic / metal heterostructure connection method based on thermal-shape synergistic regulation, in step (1), the surface microtexture pattern can be any one of dot matrix, linear, grid, or biomimetic pattern.

[0029] In this invention, the ceramic / metal heteromaterial joining method based on thermal-shape synergistic regulation, in step (2), the metal to be joined is any one of carbon steel, stainless steel, titanium alloy, Kovar alloy, etc., and its thickness is consistent with the thickness of the ceramic.

[0030] In this invention, the selection of surface microtexture in step (1) of the method for joining ceramic / metal heteromaterials based on thermal-shape synergistic regulation is as follows: When the thickness of the ceramic to be connected is <1.5mm and the thermal conductivity of the metal to be welded is below 15W / (m·K), the surface microtexture is designed with equal intervals and an interval period of 0.1~0.15mm. When the thickness of the ceramic to be connected is <1.5mm and the thermal conductivity of the metal to be welded is above 15W / (m·K), the surface microtexture is designed with equal intervals and an interval period of 0.15~0.3mm. When the thickness of the ceramic to be connected is 1.5~3mm and the thermal conductivity of the metal to be welded is below 15W / (m·K), the surface microtexture is designed with non-uniform spacing, with the microtexture spacing in the top region of the joint being 0.05~0.1mm and the microtexture spacing in the bottom region of the joint being 0.1~0.15mm. When the thickness of the ceramic to be connected is 1.5~3mm and the thermal conductivity of the metal to be welded is above 15W / (m·K), the surface microtexture is designed with non-uniform spacing, with the microtexture spacing in the top region of the joint being 0.1~0.15mm and the microtexture spacing in the bottom region of the joint being 0.15~0.3mm.

[0031] In this invention, the ceramic / metal heterostructure connection method based on thermal-shape synergistic regulation has a brazing filler metal with a melting point at least 100°C lower than the metal melting point in step (2).

[0032] Preferably, the solder is any one of silver-based solder, copper-based solder, or tin-based solder.

[0033] In this invention, the ceramic / metal heterostructure connection method based on thermal-form synergistic regulation is described, and the brazing filler metal in step (2) is in the form of powder, paste or foil.

[0034] In this invention, the ceramic / metal heteromaterial joining method based on thermal-form synergistic regulation, specifically in step (2), involves applying clamping pressure to both sides of the base materials (metal and ceramic) to be welded, with a pressure range of 30~60N. Research has shown that this pressure range is more conducive to the stability of the connection.

[0035] In this invention, the ceramic / metal heteromaterial connection method based on thermal-shape synergistic regulation, in step (4), the wavelength of the laser can be any one or multiple wavelength composite light sources of infrared light, blue light, and green light.

[0036] In this invention, the ceramic / metal heterostructure connection method based on thermal-shape synergistic regulation, in step (4), the optical fiber equipped with the laser has a core diameter of 10~100μm to ensure precise control of the beam energy.

[0037] The beneficial effects of this invention are as follows: This invention integrates a dual regulation mechanism of thermal regulation and shape regulation: thermal regulation relies on negative pressure laser welding technology, and the finger-shaped molten pool of the component replaces the inverted triangular molten pool formed by traditional laser welding. Then, through heat conduction, precise energy control is achieved at the interface, enhancing the uniformity of the thermal field in the thickness direction of the joint, and stabilizing the interface temperature within the ideal range, thus laying a good metallurgical foundation for interface behavior regulation.

[0038] Shape control improves the morphology of intermetallic compounds by constructing microtextures on the ceramic surface and inducing interfacial thermal fields under negative pressure to drive the solder wetting process, thereby adjusting the stress distribution within the joint. Ultimately, through metallurgical-structural synergy, it enhances the welding quality and mechanical properties of the joint, making it particularly suitable for high-strength, high-sealing connections between ceramics such as sapphire and alumina and metals such as copper, titanium alloys, and stainless steel. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a thermally-shaped synergistically controlled negative pressure laser connection method for ceramic-metal docking according to the present invention.

[0040] In the figure, 1 is the negative pressure chamber, 2 is the ceramic to be welded, 3 is the microtexture of the ceramic surface, 4 is the brazing filler metal, 5 is the metal side molten pool, 6 is the laser, 7 is the metal, and 8 is the lateral pressure.

[0041] Figure 2 This is a diagram illustrating the effect of preparing a uniformly distributed microtexture on the ceramic side surface in Embodiment 1 of the present invention.

[0042] Figure 3 This is an illustration of the progressively distributed microtexture on the ceramic side surface of Embodiment 2 of the present invention, which is not evenly spaced.

[0043] Figure 4 This is a typical weld formation diagram of the ceramic-metal connection joint of the present invention.

[0044] Figure 5 This is a typical microstructure diagram of the ceramic-metal interface of the present invention. Detailed Implementation

[0045] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0046] Detailed welding process diagram as follows Figure 1 As shown, the cleaned ceramic 2, metal 7, and brazing filler metal 4 with ceramic surface microtexture 3 are placed together in the welding fixture, and a certain lateral pressure 8 is applied to both sides of the parts to be connected by the fixture.

[0047] Place the assembled sample and fixture in the appropriate position inside the negative pressure chamber 1. Close the negative pressure chamber 1 to seal the entire system environment, and evacuate the entire system to reduce the environmental pressure to the preset value.

[0048] After adjusting the laser 6 to be positioned directly above the area to be welded and setting the welding parameters, welding is performed. The laser 6 moves to form a molten pool 5 on the metal side of the metal 7 and melts the brazing filler metal 4 through heat conduction, thereby achieving the connection between the ceramic 2 to be welded and the metal 7.

[0049] Example 1 This embodiment provides a negative pressure laser connection method for ceramic-metal butt welding with heat and shape coordinated control. According to the actual working conditions, the objects to be welded are non-transparent 95 series alumina ceramic and 304 stainless steel, both with a thickness of 1mm.

[0050] The thermal conductivity of 304 stainless steel is approximately 16 W / (m·K).

[0051] The alumina ceramic has a size of 50mm×100mm, and the stainless steel has a size of 50mm×100mm.

[0052] Specifically, the following steps are included: (1) Prepare surface microtextures on the ceramic surfaces to be joined.

[0053] The selected ceramic is a 95-series alumina non-transparent ceramic with a thickness of 1 mm.

[0054] The preparation of surface microtextures is mainly based on precision laser processing, using a femtosecond laser and an argon atmosphere during the process to reduce the decomposition of ceramics.

[0055] The processed pattern uses straight grooves and a uniformly distributed microtexture with equal intervals, and the microtexture period is 0.2 mm.

[0056] (2) Assemble the ceramic and the metal to be welded together, and place the brazing filler metal in the gap between the two.

[0057] The metal to be welded is stainless steel with a thickness of 1 mm.

[0058] The brazing filler metal used is silver-based AgCu28Ti2, which has a melting point of approximately 780°C, much lower than the melting point of stainless steel (1400°C), thus meeting the brazing filler metal selection criteria.

[0059] The solder used is a foil-shaped solder with a thickness of 50μm.

[0060] After cleaning the microtextured alumina ceramic and stainless steel to be joined, they are assembled by mating. Foil-shaped AgCu28Ti2 brazing filler metal is placed in the mating gap to ensure that the mating gap is uniform.

[0061] Apply a clamping pressure of 50N to both sides of the base material to be welded.

[0062] (3) Place the assembly in the negative pressure environment of the construction.

[0063] The negative pressure environment is constructed by an external negative pressure chamber, with the laser head placed outside the chamber and a light-transmitting lens reserved on the top of the chamber, the lens having a light transmittance of not less than 99%.

[0064] The negative pressure chamber is made of aluminum alloy, and its walls are 5mm thick.

[0065] The negative pressure environment is mainly achieved by evacuating air using a negative pressure pump. The degree of negative pressure can be tested by a negative pressure sensor installed inside the cabin, and the cabin pressure is displayed in real time via a digital display, ensuring that the negative pressure environment inside the cabin is 10Pa.

[0066] The negative pressure chamber is equipped with a certain dust removal function to prevent metal vapor or dust from being suspended inside the chamber or adhering to the light-transmitting lens, thus affecting the transmission of light.

[0067] The air extraction port for drawing negative pressure is located 10cm from the bottom of the chamber, and the dust removal port is located 5cm from the top of the chamber. Both are distributed on both sides of the chamber to ensure stable airflow inside the chamber and uniform local negative pressure environment in the area to be welded.

[0068] (4) Adjust the laser to a suitable position and complete the welding parameter settings before welding.

[0069] The laser is a fiber laser, and its beam energy characteristics are selected from single-mode Gaussian lasers with a wavelength of 1064nm infrared light.

[0070] Equipped with a fiber core diameter of 30μm to ensure precise control of beam energy.

[0071] The laser spot center is positioned off-center on the metal side, 2mm away from the brazing filler metal.

[0072] The laser power is 2350W and the welding speed is 2m / min.

[0073] Welding is performed using negative defocusing, with a defocusing amount of -0.5mm, to ensure the uniformity of the thermal field distribution at the joint interface.

[0074] After all parameters are set, welding is performed to obtain the connection joint.

[0075] Microstructural observation of the joint revealed a unique double-weld structure: the metal side under laser irradiation locally melts, forming finger-shaped welds with a large depth-to-width ratio; while the ceramic side relies on heat conduction to spread the brazing filler metal, forming a relatively uniform brazed weld. No obvious defects such as fine porosity or cracks were found in the entire joint.

[0076] Example 2 This embodiment provides a negative pressure laser connection method for ceramic-metal butt welding with thermal-form coordinated control. According to the actual working conditions, the objects to be welded are transparent sapphire ceramic and TC4 titanium alloy, both with a thickness of 3mm.

[0077] The thermal conductivity of TC4 titanium alloy is approximately 7.9 W / (m·K).

[0078] The sapphire ceramic material measures 50mm × 100mm, while the TC4 titanium alloy material measures 50mm × 100mm.

[0079] Specifically, the following steps are included: (1) Prepare surface microtextures on the ceramic surfaces to be joined.

[0080] The selected ceramic is sapphire transparent ceramic, with a thickness of 3mm.

[0081] The fabrication of surface microtextures is mainly achieved through precision laser processing, using a femtosecond laser and a nitrogen atmosphere during the process to reduce the decomposition of ceramics.

[0082] The processed pattern uses a grid-type groove and a progressively distributed microtexture with non-equal intervals. The microtexture interval in the top area of ​​the joint is 0.05mm, and the microtexture interval in the bottom area of ​​the joint is 0.1mm.

[0083] (2) Assemble the ceramic and the metal to be connected by mating, and place the brazing filler metal in the mating gap.

[0084] The metal to be connected is a TC4 titanium alloy with a thickness of 3mm.

[0085] The brazing filler metal selected is CuZn48, which has a melting point of approximately 900℃, much lower than the melting point of TC4 titanium alloy (1600℃), thus meeting the brazing filler metal selection criteria.

[0086] The brazing filler metal is in powder form and has a thickness of 60 μm.

[0087] After cleaning, the microtextured sapphire ceramic and TC4 titanium alloy to be connected are assembled. Powdered CuZn48 brazing filler metal is placed in the joint gap to ensure that the joint gap is uniform.

[0088] Apply a clamping pressure of 30N to both sides of the base material to be welded to avoid excessive pressure that could squeeze out the brazing filler metal.

[0089] (3) Place the assembly in the negative pressure environment of the construction.

[0090] The negative pressure environment is constructed using an external negative pressure chamber, with the laser head housed within it. The negative pressure chamber is made of stainless steel, with walls 10mm thick.

[0091] The negative pressure environment is mainly achieved by evacuating air using a negative pressure pump. The degree of negative pressure can be measured by a negative pressure sensor installed inside the chamber, and the pressure inside the chamber is displayed in real time via a digital display, ensuring a negative pressure environment of 10 inside the chamber. -2 Pa.

[0092] The negative pressure chamber is equipped with a certain dust removal function to prevent metal vapor or fumes from suspending inside the chamber or adhering to the light-transmitting lens, thus affecting the transmission of light. The air extraction port for drawing negative pressure is located 10cm from the bottom of the chamber, and the dust removal port is located 20cm above the laser processing plane. Both are located on the same side of the chamber to ensure stable airflow inside the chamber and uniform local negative pressure environment in the area to be welded.

[0093] (4) Adjust the laser to a suitable position and complete the welding parameter settings before welding.

[0094] The laser is a fiber laser with tunable spot energy characteristics in ring-core mode and a wavelength of 1064nm infrared light.

[0095] Equipped with fiber core diameter of 14 / 100μm to ensure precise control of beam energy.

[0096] The laser spot center is offset to the metal side, with a distance of 0.5mm from the brazing filler metal.

[0097] The laser power is 2000W, and the welding speed is 1.2m / min.

[0098] Welding is performed using negative defocusing, with a defocusing amount of -1.5mm, to ensure the uniformity of the thermal field distribution at the joint interface.

[0099] Example 3 This embodiment provides a negative pressure laser joining method for ceramic-metal butt welding with thermal-form synergistic control. Based on actual working conditions, the objects to be welded are non-transparent silicon carbide ceramic and Kovar alloy. Both have a thickness of 1.5 mm.

[0100] The thermal conductivity of Kovar alloy is 20.6 W·m. -1 ·K -1 .

[0101] The silicon carbide ceramic has a size of 80mm×120mm, and the Kovar alloy has a size of 80mm×120mm.

[0102] Specifically, the following steps are included: (1) Prepare surface microtextures on the ceramic surfaces to be joined.

[0103] The selected ceramic is a non-transparent silicon carbide ceramic with a thickness of 1.5 mm.

[0104] The preparation of surface microtextures is mainly based on precision laser processing, using a femtosecond laser and an argon atmosphere during the process to reduce the decomposition of ceramics.

[0105] The processed pattern uses dot matrix grooves and employs evenly spaced, uniformly distributed microtextures with a microtexture period of 0.3 mm.

[0106] (2) Assemble the ceramic and the metal to be welded together, and place the brazing filler metal in the gap between the two.

[0107] The metal to be welded is a Kovar alloy with a thickness of 1.5 mm.

[0108] The brazing filler metal selected is silver-based AgCu28Ti2, which has a melting point of approximately 780℃, much lower than the melting point of stainless steel (1450℃), thus meeting the brazing filler metal selection criteria.

[0109] The solder used is a foil-shaped solder with a thickness of 50μm.

[0110] After cleaning the microtextured silicon carbide ceramic and Kovar alloy to be joined, they are assembled by mating. Foil-shaped AgCu28Ti2 brazing filler metal is placed in the mating gap to ensure that the mating gap is uniform.

[0111] Apply a clamping pressure of 40N to both sides of the base material to be welded.

[0112] (3) Place the assembly in the negative pressure environment of the construction.

[0113] The negative pressure environment is constructed by an external negative pressure chamber, with the laser head placed outside the chamber and a light-transmitting lens reserved on the top of the chamber, the lens having a light transmittance of not less than 99%.

[0114] The negative pressure chamber is made of aluminum alloy, and its walls are 4mm thick.

[0115] The negative pressure environment is mainly achieved by evacuating air using a negative pressure pump. The degree of negative pressure can be tested by a negative pressure sensor installed inside the cabin, and the cabin pressure can be displayed in real time via a digital display, ensuring that the negative pressure environment inside the cabin is 100Pa.

[0116] The negative pressure chamber is equipped with a certain dust removal function to prevent metal vapor or dust from being suspended inside the chamber or adhering to the light-transmitting lens, thus affecting the transmission of light.

[0117] The air extraction port for drawing negative pressure is located 10cm from the bottom of the chamber, and the dust removal port is located 5cm from the top of the chamber. Both are distributed on both sides of the chamber to ensure stable airflow inside the chamber and uniform local negative pressure environment in the area to be welded.

[0118] (4) Adjust the laser to a suitable position and complete the welding parameter settings before welding.

[0119] The laser is a fiber laser with tunable spot energy characteristics in ring-core mode and a wavelength of 1064nm infrared light.

[0120] Equipped with fiber core diameters of 30 / 100μm to ensure precise control of beam energy.

[0121] The laser spot center is offset to the metal side, and the distance from the solder is 2.5mm.

[0122] The laser power is 2300W, and the welding speed is 1.5m / min.

[0123] Welding is performed using negative defocusing, with a defocusing amount of -0.7mm, to ensure the uniformity of the thermal field distribution at the joint interface.

[0124] After all parameters are set, welding is performed to obtain the connection joint.

[0125] Compared to Example 1, this example makes corresponding adjustments to the process to address the characteristics of thin silicon carbide ceramics with good thermal conductivity and Kovar alloy with high thermal conductivity: First, a lattice-type equally spaced microtexture design is adopted, which is beneficial for uniform stress distribution and interface bonding; second, the laser power is appropriately increased and the spot offset distance is adjusted to accommodate the higher thermal conductivity of Kovar alloy and optimize heat input control. Under optimized process conditions, the metal side melts uniformly under laser action, and the ceramic side achieves good spread of the brazing filler metal through heat conduction, forming a continuous and dense brazed weld. The joint as a whole is free of obvious porosity, cracks, and other welding defects, meeting the actual connection quality requirements.

[0126] This embodiment addresses the material properties of silicon carbide ceramics and Kovar alloys by optimizing multiple process stages: adjusting the type and distribution of the microtexture pattern, and optimizing the clamping force and negative pressure environment parameters; in the laser welding stage, improving the spot energy distribution pattern and adjusting the heat input parameters and defocusing amount configuration. Through these comprehensive adjustments, the characteristics and thickness variations of the material combination are effectively adapted, ultimately resulting in a high-quality joint with a double weld seam structure, complete interface bonding, and no visible defects.

[0127] Example 4 This embodiment provides a negative pressure laser joining method for ceramic-metal butt welding with thermal-form coordinated control. Based on actual working conditions, the objects to be welded are non-transparent aluminum nitride ceramic and carbon steel. The selected ceramic is aluminum nitride ceramic with a thickness of 2.5 mm.

[0128] The thermal conductivity of carbon steel is 45 W·m. -1 ·K -1 .

[0129] The aluminum nitride ceramic has a size of 50mm×100mm, and the stainless steel has a size of 50mm×100mm.

[0130] Specifically, the following steps are included: (1) Prepare surface microtextures on the ceramic surfaces to be joined.

[0131] The preparation of surface microtextures is mainly based on precision laser processing, using a femtosecond laser and an argon atmosphere during the process to reduce the decomposition of ceramics.

[0132] The processed pattern uses a grid-type groove and a progressively distributed microtexture with non-equal intervals. The microtexture interval in the top area of ​​the joint is 0.1 mm, and the microtexture interval in the bottom area of ​​the joint is 0.2 mm.

[0133] (2) Assemble the ceramic and the metal to be welded together, and place the brazing filler metal in the gap between the two.

[0134] The metal to be welded is a TC4 titanium alloy with a thickness of 2.5 mm.

[0135] The brazing filler metal selected is CuZn48, which has a melting point of approximately 900℃, much lower than the melting point of TC4 titanium alloy (1600℃), thus meeting the brazing filler metal selection criteria.

[0136] The brazing filler metal is in powder form and has a thickness of 55 μm.

[0137] After cleaning, the microtextured aluminum nitride ceramic and TC4 titanium alloy to be connected are assembled. Powdered CuZn48 brazing filler metal is placed in the joint gap to ensure that the joint gap is uniform.

[0138] Apply a clamping pressure of 30N to both sides of the base material to be welded to avoid excessive pressure that could squeeze out the brazing filler metal.

[0139] (3) Place the assembly in the negative pressure environment of the construction.

[0140] The negative pressure environment is constructed using an external negative pressure chamber, with the laser head housed within it. The negative pressure chamber is made of stainless steel, with walls 3mm thick.

[0141] The negative pressure environment is mainly achieved by evacuating air using a negative pressure pump. The degree of negative pressure can be tested by a negative pressure sensor installed inside the cabin, and the cabin pressure is displayed in real time via a digital display, ensuring that the negative pressure environment inside the cabin is 0.1 Pa.

[0142] The negative pressure chamber is equipped with a certain dust removal function to prevent metal vapor or fumes from suspending inside the chamber or adhering to the light-transmitting lens, thus affecting the transmission of light. The air extraction port for drawing negative pressure is located 10cm from the bottom of the chamber, and the dust removal port is located 20cm above the laser processing plane. Both are located on the same side of the chamber to ensure stable airflow inside the chamber and uniform local negative pressure environment in the area to be welded.

[0143] (4) Adjust the laser to a suitable position and complete the welding parameter settings before welding.

[0144] The laser is a fiber laser, and its beam energy characteristics are selected from single-mode Gaussian lasers with a wavelength of 1064nm infrared light.

[0145] It is equipped with an optical fiber core diameter of 14μm to ensure precise control of beam energy.

[0146] The laser spot center is positioned off-center from the metal side, at a distance of 3mm from the brazing filler metal.

[0147] The laser power is 2100W, and the welding speed is 1.3m / min.

[0148] Welding is performed using negative defocusing, with a defocusing amount of -1.2mm, to ensure the uniformity of the thermal field distribution at the joint interface.

[0149] After all parameters are set, welding is performed to obtain the connection joint.

[0150] Compared to Example 2, this example systematically adjusts the process parameters based on the material combination of aluminum nitride ceramic and carbon steel and its thermophysical properties. Regarding surface texture, a non-uniformly distributed grid-type groove design is adopted; the clamping force settings are optimized during assembly; and the negative pressure environment parameters are adjusted according to the differences in material thermal conductivity.

[0151] During the laser welding stage, different spot modes were selected, and the heat input parameters and beam position were optimized to accommodate the higher thermal conductivity and ensure uniform heat field distribution. These targeted adjustments effectively controlled the interfacial reaction process, resulting in a well-formed double-weld joint with a dense interfacial bond and no defects.

[0152] Comparative Example 1 The difference from Example 1 is that this comparative example does not provide a negative pressure environment but provides an argon-protected environment, while other welding materials, structures and process parameters are the same.

[0153] This comparative example provides a negative pressure laser connection method for ceramic-metal butt welding with thermal-form synergistic control. According to the actual working conditions, the objects to be welded are 95 series alumina ceramic and 304 stainless steel, both with a thickness of 1mm.

[0154] The thermal conductivity of 304 stainless steel is approximately 16 W / (m·K). The alumina ceramic size is 50 mm × 100 mm, and the stainless steel size is 50 mm × 100 mm.

[0155] Specifically, the process includes the following steps: using traditional laser welding technology, direct melting welding is performed in an atmospheric environment. (1) Prepare surface microtextures on the ceramic surfaces to be joined.

[0156] The selected ceramic is a 95-series alumina non-transparent ceramic with a thickness of 1 mm.

[0157] The preparation of surface microtextures is mainly based on precision laser processing, using a femtosecond laser and an argon atmosphere during the process to reduce the decomposition of ceramics.

[0158] The processed pattern uses straight grooves and a uniformly distributed microtexture with equal intervals, and the microtexture period is 0.2 mm.

[0159] (2) Assemble the ceramic and the metal to be connected by mating, and place the brazing filler metal in the mating gap.

[0160] The metal to be connected is stainless steel with a thickness of 1mm.

[0161] The brazing filler metal used is silver-based AgCu28Ti2, which has a melting point of approximately 780°C, much lower than the melting point of stainless steel (1400°C), thus meeting the brazing filler metal selection criteria.

[0162] The solder used is a foil-shaped solder with a thickness of 50μm.

[0163] After cleaning the microtextured alumina ceramic and stainless steel to be joined, they are assembled by mating. Foil-shaped AgCu28Ti2 brazing filler metal is placed in the mating gap to ensure that the mating gap is uniform.

[0164] Apply a clamping pressure of 50N to both sides of the base material to be welded.

[0165] (3) The assembled sample to be welded is placed in the same chamber as in Example 1, and the chamber is filled with argon gas to suppress oxidation during the welding process, and the chamber is kept at a standard atmospheric pressure of 10. 5 Pa.

[0166] (4) Adjust the laser to a suitable position and complete the welding parameter settings before welding.

[0167] The laser is a fiber laser, and its beam energy characteristics are selected from single-mode Gaussian lasers with a wavelength of 1064nm infrared light.

[0168] Equipped with a fiber core diameter of 30μm to ensure precise control of beam energy.

[0169] The laser spot center is positioned off-center on the metal side, 2mm away from the brazing filler metal.

[0170] The laser power is 2350W and the welding speed is 2m / min.

[0171] Welding is performed using negative defocusing, with a defocusing amount of -0.5mm, to ensure the uniformity of the thermal field distribution at the joint interface.

[0172] After all parameters are set, welding is performed to obtain the connection joint.

[0173] Compared to Example 1, this comparative example uses a conventional laser welding process under atmospheric pressure argon protection, and the results show a significant difference in joint quality. Due to the lack of a negative pressure environment, the metal vapors and gases generated during welding cannot be effectively discharged, resulting in numerous porosity defects at the joint interface.

[0174] Meanwhile, the thermal conductivity under normal pressure differs significantly from that under negative pressure, leading to uneven heat distribution, insufficient brazing filler metal spread on the ceramic side, and decreased interfacial bonding quality. Metallographic observation revealed an irregular inverted triangular molten pool morphology on the metal side of the joint, and microcracks were visible at the ceramic interface. These defects significantly degraded the mechanical properties of the joint, validating the crucial role of negative pressure in suppressing welding defects and optimizing heat distribution.

[0175] Comparative Example 2 The objects to be welded in this comparative example are 95 series alumina ceramic and 304 stainless steel.

[0176] The difference from Example 1 is that the object to be welded in this comparative example is a ceramic surface that has not undergone microtexturing treatment.

[0177] The others are the same as in Example 1.

[0178] Compared to Example 1, this comparative example did not perform microtexturing treatment on the ceramic surface, and the results showed a significant decrease in joint quality. Due to the lack of the mechanical interlocking effect of surface microtexturing, the wetting and spreading of the solder on the ceramic surface was significantly limited, and the interfacial bonding strength was greatly reduced.

[0179] Meanwhile, the smooth ceramic surface cannot effectively release the thermal stress during the welding process, leading to noticeable microcracks at the interface. Microstructural observation shows that the ceramic side interface bonding is discontinuous, with localized unbonded areas. These defects confirm the important role of surface microtexture in promoting solder spread, alleviating thermal stress, and enhancing interfacial bonding.

[0180] Comparative Example 3 The difference from Example 1 is that the laser power in step (4) of this comparative example is 3200W.

[0181] The others are the same as in Example 1.

[0182] Compared to Example 1, this comparative example used excessively high laser power for welding, resulting in a significant deterioration in joint quality. Excessive heat input caused over-melting on the metal side, leading to substantial evaporation and loss of the brazing filler metal, while macroscopic cracks formed on the ceramic side due to thermal shock. The overly intense interfacial reaction resulted in coarse weld microstructure and a significant increase in porosity defects. This demonstrates that precise control of laser power plays a crucial role in maintaining interfacial thermal balance and ensuring joint quality.

[0183] The airtightness of the butt weld between the ceramic and metal plate was tested using helium mass spectrometry leak detection. During the test, one side of the weld was evacuated and connected to a helium mass spectrometer leak detector, while helium gas at a certain pressure was applied to the other side of the weld. The leakage rate of the weld was determined by the leak rate reading of the detection instrument.

[0184] The tensile strength of the butt weld between the ceramic and metal plates was tested using a universal testing machine. During the test, the two ends of the butt weld specimen were clamped in the upper and lower fixtures of the testing machine, respectively. Then, an axial tensile load was applied at a constant rate until the specimen fractured. The tensile strength of the weld was calculated based on the maximum load recorded during the test and the original cross-sectional area of ​​the weld.

[0185] The specific test results are shown in Table 1.

[0186]

Claims

1. A method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation, characterized in that, Includes the following steps: (1) Prepare uniformly distributed or progressively distributed surface microtextures on the ceramic surface to be joined; (2) Assemble the ceramic and the metal to be welded by butt joint, and pre-place the brazing filler metal within a butt joint gap of 30~100μm to obtain the assembly; the thickness of the selected brazing filler metal is matched with the butt joint gap. (3) Place the assembly in a negative pressure environment of 10. -2 ~10 2 In the negative pressure chamber of Pa; When the thickness of the metal to be welded is 0.5mm ≤ 1.5mm, the negative pressure is 1~10. 2 Pa; When the thickness of the metal to be welded is 1.5mm < 3mm, the negative pressure is 10. -2 ~1Pa; (4) Adjust the laser to a suitable position so that the center of its spot is offset on the metal side, and use negative defocusing for welding to form a uniform finger-shaped molten pool; The laser power is 2000~3000W, the welding speed is 1~2m / min, the distance between the laser spot and the brazing filler metal is 0.3~3mm, and the defocusing amount is ≤1 / 2 of the thickness of the metal plate. When the thermal conductivity of the metal to be soldered is below 15 W / (m·K), the distance between the solder spot and the brazing filler metal is 0.3~1 mm; When the thermal conductivity of the metal to be soldered is above 15 W / (m·K), the distance between the solder spot and the brazing filler metal is 1~3 mm.

2. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, In step (1), the thickness of the ceramic is 0.5~3mm; the thickness of the ceramic is consistent with the thickness of the metal to be welded. The uniformly distributed surface microtexture in step (1) is equally spaced, and its microtexture period is 0.1~0.3mm; When the thickness of the ceramic to be connected is <1.5mm and the thermal conductivity of the metal to be welded is below 15W / (m·K), the surface microtexture is designed with equal intervals and an interval period of 0.1~0.15mm. When the thickness of the ceramic to be connected is <1.5mm and the thermal conductivity of the metal to be welded is above 15W / (m·K), the surface microtexture is designed with equal intervals and an interval period of 0.15~0.3mm. When the thickness of the ceramic to be connected is 1.5~3mm and the thermal conductivity of the metal to be welded is below 15W / (m·K), the surface microtexture is designed with non-uniform spacing, with the microtexture spacing in the top region of the joint being 0.05~0.1mm and the microtexture spacing in the bottom region of the joint being 0.1~0.15mm. When the thickness of the ceramic to be connected is 1.5~3mm and the thermal conductivity of the metal to be welded is above 15W / (m·K), the surface microtexture is designed with non-uniform spacing, with the microtexture spacing in the top region of the joint being 0.1~0.15mm and the microtexture spacing in the bottom region of the joint being 0.15~0.3mm.

3. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, In step (1), the ceramic is any one of oxide ceramics, carbide ceramics, or nitride ceramics.

4. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, In step (1), the ceramic can be either transparent or opaque.

5. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, In step (2), the metal to be welded is any one of carbon steel, stainless steel, titanium alloy or Kovar alloy.

6. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, In step (2), the melting point of the brazing filler metal is at least 100°C lower than that of the metal. The brazing filler metal is in the form of powder, paste, or foil.

7. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, The specific operation of the butt assembly in step (2) is as follows: apply clamping pressure on both sides of the base material to be welded, with a pressure range of 30~60N.

8. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, In step (4), the light source wavelength of the laser is any one of infrared light, blue light, or green light, or a combination of multiple wavelengths.

9. The method for joining ceramic / metal heteromaterials based on thermal-form synergistic regulation according to claim 1, characterized in that, The core diameter of the optical fiber equipped with the laser in step (4) is 10~100μm.

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