A method for ceramic-metal ultra-short pulsed laser welding

Abstract

This invention relates to an ultrashort pulse laser welding method for ceramic-metal bonding, belonging to the field of ultrashort pulse laser welding. It addresses the problems of existing brazing methods for ceramic-metal bonding, which require high vacuum and high temperature environments, are complex to operate, and have long welding times; and the problems of existing diffusion welding methods for ceramic-metal bonding, which require high temperature environments, apply additional loads making welding small workpieces difficult, and have long welding times. The method comprises: 1. Cutting the ceramic and metal separately to obtain suitable dimensions and smooth surfaces to be welded; 2. Setting the ceramic and metal surfaces to be welded parallel and opposite each other, leaving a gap between the two surfaces, and finally fixing them to obtain the workpiece to be welded; 3. Performing ultrashort pulse laser welding. This invention is used for ultrashort pulse laser welding of ceramics and metals.

Description

Technical Field

[0001] This invention belongs to the field of ultrashort pulse laser welding. Background Technology

[0002] Ceramic materials possess excellent properties such as high hardness, high strength, high temperature resistance, wear resistance, and corrosion resistance, and are widely used in aerospace, energy, and large-scale equipment. However, due to their high brittleness and poor toughness, ceramic materials are difficult to process, severely limiting their application in many fields. Metal materials, on the other hand, possess high plasticity and toughness, as well as good processing stability. Joining ceramic materials with metal materials can greatly expand the application scenarios of ceramic materials. Domestic and international scholars have conducted extensive research on the connection between the two, and currently, commonly used ceramic-metal joining methods mainly involve brazing and diffusion welding. Brazing often requires the use of active filler metals to wet the ceramic, commonly using filler metals containing active elements such as Ti and Zr. These filler metals are expensive and usually require a high-vacuum environment, placing high demands on equipment. Diffusion welding requires high welding temperatures; using this method to weld temperature-sensitive electronic components can damage them. Furthermore, the welding process usually requires applying a certain load to the sample to be welded, which places high demands on the welding operation of small structural parts. In addition, both welding methods typically require high temperatures, long welding times, high energy consumption, and low production efficiency, which are not conducive to large-scale production. Therefore, there is an urgent need to develop a new and efficient ceramic-metal welding method. Summary of the Invention

[0003] This invention aims to address the problems of existing brazing methods for ceramic-metal bonding, which require high vacuum and high temperature environments, are complex to operate, and have long welding times; and to address the problems of existing diffusion welding methods for ceramic-metal bonding, which require high temperature environments, apply additional loads, make welding small workpieces difficult, and have long welding times. Instead, it provides an ultrashort pulse laser welding method for ceramic-metal bonding.

[0004] An ultrashort pulse laser welding method for ceramic-metal bonding comprises the following steps:

[0005] 1. Cut the ceramics and metals separately to obtain suitable dimensions and smooth surfaces for welding;

[0006] 2. Set the ceramic and metal surfaces to be welded parallel and opposite to each other, leaving a gap between the two surfaces, and finally fix them to obtain the parts to be welded.

[0007] 3. Adjust the laser focus to focus near the joint gap of the workpiece to be welded. Using an ultrashort pulse laser, welding is performed under the following conditions: room temperature, air atmosphere, pulse width of 100 fs to 10 ps, ​​repetition frequency of 0.5 MHz to 10 MHz, welding speed of 0.5 mm / s to 10 mm / s, laser power of 10 W to 50 W, and laser defocusing amount of -500 μm to 0 μm. This completes the ultrashort pulse laser welding method for ceramics-metal.

[0008] The beneficial effects of this invention are:

[0009] 1. This invention enables effective welding of ceramic and metal materials at room temperature and in air atmosphere, without the need for high temperature environment or additional load, thus saving energy. The experimental operation is simple, the welding speed is fast, and the welding efficiency is high.

[0010] 2. The welding affected area of ​​this invention is small, and it has little impact on the microstructure and morphology of ceramic and metal substrates. There is no obvious heat-affected zone around the weld, and the weld width is less than 300μm. In addition, the welding power of this invention is low and the heat input is small, which will not cause over-evaporation of the base material substrate, which is beneficial to improving the strength of the welded sample.

[0011] 3. This invention is applicable to ultrashort pulse laser welding of various types of ceramics, such as alumina ceramics and zirconia ceramics; it is also applicable to ultrashort pulse laser welding of various types of metal materials and their alloys, such as active metals like titanium, zirconium, vanadium, and titanium alloys; and it is also applicable to inactive metals, such as iron, copper, stainless steel, and silver-copper alloys.

[0012] 4. The welded joint obtained by this invention has high strength, with a four-point bending strength of up to 135 MPa.

[0013] 5. In the welding process, the present invention only requires a single laser welding of the area to be welded to connect the two base materials, eliminating the need for multiple laser welding passes. The operation is simple and the welding efficiency is high.

[0014] This invention relates to an ultrashort pulse laser welding method for ceramic-metal composites. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the ultrashort pulse laser welding method for ceramic-metal in Example 1. 1 is ceramic, 2 is metal, 3 is vise, 4 is xy-axis linked laser operating stage, 5 is objective lens for focusing laser beam, and 6 is laser beam.

[0016] Figure 2 A photograph of the surface morphology of the Al2O3-TA2 weldment prepared in Example 1;

[0017] Figure 3The images are cross-sectional scanning electron microscope images of the Al2O3-TA2 welded parts prepared in Example 1. (1) is a magnified view of a local area of ​​the Al2O3- weld, (2) is an overall morphology image of the interface of the Al2O3-TA2 welded parts, and (3) is a magnified view of a local area of ​​the weld-TA2.

[0018] Figure 4 This is an EDS elemental surface scan analysis image of the cross-section of the Al2O3-TA2 weldment prepared in Example 1;

[0019] Figure 5 The fracture surface diagrams of the failed Al2O3-TA2 welded parts prepared in Example 1 after four-point bending test are shown in (1), (2) and (3) are magnified views of local areas in (1).

[0020] Figure 6 The transmission electron microscope (TEM) images of the Al2O3-TA2 welded part prepared in Example 1 located on the alumina-weld side are shown in (1), (2) is the morphology of the weld joint and its EDS elemental surface scan distribution map, and (3) is the high-resolution transmission electron micrograph of the area selected in (1).

[0021] Figure 7 This is a cross-sectional scanning electron microscope image of the Al2O3-TA2 weldment prepared in Example 2;

[0022] Figure 8 The fracture surface diagrams of the Al2O3-TA2 welded parts prepared in Example 2 after a four-point bending test are shown in (1), which is a fracture surface morphology diagram of the fractured sample, and (2) and (3) are magnified views of local areas in (1). Detailed Implementation

[0023] Specific Implementation Method 1: This implementation method describes an ultrashort pulse laser welding method for ceramic-metal composites, which is carried out according to the following steps:

[0024] 1. Cut the ceramics and metals separately to obtain suitable dimensions and smooth surfaces for welding;

[0025] 2. Set the ceramic and metal surfaces to be welded parallel and opposite to each other, leaving a gap between the two surfaces, and finally fix them to obtain the parts to be welded.

[0026] 3. Adjust the laser focus to focus near the joint gap of the workpiece to be welded. Using an ultrashort pulse laser, welding is performed under the following conditions: room temperature, air atmosphere, pulse width of 100 fs to 10 ps, ​​repetition frequency of 0.5 MHz to 10 MHz, welding speed of 0.5 mm / s to 10 mm / s, laser power of 10 W to 50 W, and laser defocusing amount of -500 μm to 0 μm. This completes the ultrashort pulse laser welding method for ceramics-metal.

[0027] principle:

[0028] Ultrashort pulse lasers have extremely short pulse widths, allowing for the achievement of ultra-high peak power with relatively low average laser power. Ceramics that normally do not absorb light of this wavelength undergo nonlinear absorption when irradiated by ultrashort pulse lasers with extremely high peak power. This nonlinear absorption process involves laser-induced multiphoton ionization (tunneling ionization) and avalanche ionization, generating a large number of free electrons. This process releases significant heat, leading to the melting and mechanical mixing of the ceramic and metal materials. Furthermore, the chemical reactions between the ceramic and metal in the localized high-temperature environment also strengthen the joint. Once the laser treatment stops and the molten area cools, the ceramic-metal bond is achieved.

[0029] The beneficial effects of this specific implementation method are:

[0030] 1. This specific embodiment can effectively weld ceramic and metal materials in room temperature and air atmosphere, without the need for high temperature environment or additional load, saving energy, simple experimental operation, fast welding speed and high welding efficiency.

[0031] 2. In this specific embodiment, the welding affected area is small, and the impact on the microstructure and morphology of the ceramic and metal substrates is minimal. There is no obvious heat-affected zone around the weld, and the weld width is less than 300 μm. Furthermore, this specific embodiment has low welding power and low heat input, which will not cause excessive evaporation of the base material substrate, thus contributing to the improvement of the strength of the welded sample.

[0032] 3. This specific implementation method is applicable to ultrashort pulse laser welding of various types of ceramics, such as alumina ceramics and zirconia ceramics; it is also applicable to ultrashort pulse laser welding of various types of metal materials and their alloys, such as active metals like titanium and zirconium, vanadium and titanium alloys, and is equally applicable to inactive metals, such as iron, copper, stainless steel and silver-copper alloys.

[0033] 4. The welded joint obtained by this specific embodiment has high strength, and the four-point bending strength can reach 135MPa.

[0034] 5. In this specific embodiment, only a single laser welding of the area to be welded is required during the welding process to connect the two base materials. There is no need for multiple laser welding passes, making the operation simple and the welding efficiency high.

[0035] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the ceramic mentioned in step one is alumina ceramic or zirconia ceramic. Everything else is the same as in Specific Implementation Method One.

[0036] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the metal mentioned in step one is titanium, zirconium, vanadium, iron, copper, stainless steel, titanium alloy, or silver-copper alloy. Everything else is the same as in Specific Implementation Method One or Two.

[0037] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the thickness of the ceramic and metal mentioned in step one is 0.5mm to 3.0mm. Everything else is the same as in Specific Implementation Methods One to Three.

[0038] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: in step one, the ceramic is cut to obtain a suitable size and a smooth surface to be welded. Specifically, this is done as follows: the ceramic is cut using a diamond wire cutter to obtain a suitable size and a smooth surface to be welded. After cutting, it is placed in a 90%–95% alcohol solution and ultrasonically cleaned for 5–10 minutes at a power of 200W–240W. Everything else is the same as in Specific Implementation Methods One to Four.

[0039] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step one, the metal is cut to obtain a suitable size and a smooth surface to be welded. Specifically, this is done as follows: the metal is cut using a slow wire EDM machine to obtain a suitable size and a smooth surface to be welded. After cutting, the metal is placed in a 90%–95% alcohol solution and ultrasonically cleaned for 5–10 minutes at a power of 200W–240W. Everything else is the same as in Specific Implementation Methods One to Five.

[0040] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the gap width described in step two is 40μm to 70μm. Everything else is the same as in Specific Implementation Methods One to Six.

[0041] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: in step three, adjusting the laser focus to be near the joint gap of the workpiece to be welded specifically means adjusting the distance between the laser focus and the center of the joint gap to ≤50μm. Everything else is the same as in Specific Implementation Methods One to Seven.

[0042] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the wavelength of the ultrashort pulse laser described in step three is 1030 nm. Everything else is the same as in Specific Implementation Methods One to Eight.

[0043] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that: in step three, the laser focus is adjusted to be focused near the joint gap of the workpiece to be welded. Welding is performed using an ultrashort pulse laser under the following conditions: room temperature, air atmosphere, pulse width of 300 fs, repetition frequency of 1 MHz, welding speed of 0.8 mm / s to 1.1 mm / s, laser power of 23.77 W, and laser defocusing amount of -200 μm. Everything else is the same as in Specific Implementation Methods One through Nine.

[0044] The beneficial effects of the present invention are verified using the following embodiments:

[0045] Example 1, combined with Figure 1 Detailed explanation:

[0046] An ultrashort pulse laser welding method for ceramic-metal bonding comprises the following steps:

[0047] 1. Cut the ceramics and metals separately to obtain suitable dimensions and smooth surfaces for welding;

[0048] 2. Set the ceramic and metal surfaces to be welded parallel and opposite to each other, with a gap of 40μm between the two surfaces to be welded. Finally, use a bench vise to fix them to obtain the parts to be welded.

[0049] 3. Place the workpiece to be welded on the xy-axis linked laser operating stage, adjust the laser focus to be above the ceramic, and the distance between the laser focus and the center of the joint gap is 50μm. Using an ultrashort pulse laser, weld under the conditions of room temperature, air atmosphere, pulse width of 300fs, repetition frequency of 1MHz, welding speed of 0.8mm / s, laser power of 23.77W, and laser defocusing amount of -200μm to obtain Al2O3-TA2 welded parts.

[0050] The ceramic mentioned in step one is an alumina ceramic with a purity of 95%.

[0051] The metal mentioned in step one is TA2 titanium alloy.

[0052] The thickness of both the ceramic and metal mentioned in step one is 0.5 mm.

[0053] Step one involves cutting the ceramic to obtain a suitable size and a smooth surface for welding. Specifically, this is done using a diamond wire cutter to cut the ceramic to a size of 15×2×0.5mm. 3 After cutting the sheet-like and smooth surfaces to be welded, place them in a 95% alcohol solution and ultrasonically clean them for 5 minutes at a power of 240W.

[0054] Step one involves cutting the metal to obtain the appropriate size and a smooth surface for welding. Specifically, this is done using a wire EDM machine to cut the metal to a size of 15×2×0.5mm. 3 After cutting the sheet-like and smooth surfaces to be welded, place them in a 95% alcohol solution and ultrasonically clean them for 5 minutes at a power of 240W.

[0055] The wavelength of the ultrashort pulse laser mentioned in step three is 1030 nm.

[0056] Figure 2 The image shows the surface morphology of the Al2O3-TA2 welded part prepared in Example 1. As can be seen from the image, there are no obvious hot cracks on the surface of the ceramic and TA2 base materials, and there are also no obvious hot cracks at the weld joint, indicating that the two materials have a good bonding effect.

[0057] Figure 3 The images shown are cross-sectional scanning electron microscope (SEM) images of the Al2O3-TA2 welded parts prepared in Example 1. (1) is a magnified view of a local area of ​​the Al2O3-TA2 weld, (2) is an overall morphology image of the interface of the Al2O3-TA2 welded parts, and (3) is a magnified view of a local area of ​​the weld-TA2 weld. From the cross-sectional morphology of the samples, it can be seen that the ultrashort pulse laser can weld ceramic and metal materials well, and the back side of the sample can be fully penetrated. The weld joint is dense and free of defects such as cracks. The joint is tightly bonded to the interface between the joint and the two base materials. There is a clearly visible two-phase mixing phenomenon in the joint. The contrast of the joint is significantly different from that of the base materials on both sides. Moreover, the weld-affected zone is small, and the influence on the microstructure and morphology of the ceramic and metal substrates is small. There is no obvious heat-affected zone around the weld, and the weld width is less than 300 μm.

[0058] Figure 4 The image shows the cross-sectional EDS elemental surface scan analysis of the Al2O3-TA2 welded part prepared in Example 1. As can be seen from the image, there is a clear mixture of Ti, O and Al elements in the weld interface, and each element is evenly distributed. There is a clear trend of Al element diffusion towards the TA2 side at the weld-TA2 interface. EDS analysis shows that the joint structure is uniform, there is a certain degree of element diffusion on both sides of the interface, and the sample interface is well bonded.

[0059] According to the GB / T39826-2021 test standard, the four-point bending strength of the Al2O3-TA2 welded part prepared in Example 1 is 135MPa. Figure 5 The fracture surface diagrams of the failed Al2O3-TA2 welded parts prepared in Example 1 after four-point bending test are shown in (1), (2) and (3) are magnified views of local areas in (1). As can be seen from the figures, most of the fracture surface is transgranular fracture, and there are few defects inside the weld, which makes a significant contribution to the improvement of joint strength.

[0060] Figure 6 The images shown are transmission electron microscopy (TEM) images of the Al2O3-TA2 welded part prepared in Example 1, located on the alumina-weld side. (1) shows the morphology of the weld joint and its EDS elemental surface scan distribution. (2) shows the high-resolution TEM image of the area highlighted in (1). (3) shows the electron diffraction patterns of phases A and B in (2). From Figure (1), it can be seen that the sample at the interface is mainly composed of two phases. The inner phase is mainly composed of Ti and O elements, while the outer phase is mainly composed of Al and O elements. The interface between the two phases is clear. From Figure (2), it can be seen that the interface between the two phases is well connected. Figure (3) shows that phase A is Al2O3 and phase B is TiO2. During the welding process, the two base materials melt and mix. Al2O3 does not undergo chemical reaction, while TA2 alloy is oxidized and TiO2 is generated. Through transmission electron microscopy analysis, it can be determined that the two are not simply melted and mechanically mixed during the welding process. A certain chemical reaction can still occur during the rapid welding process. Furthermore, through the analysis of the two-phase interface, it is found that the two are tightly connected without defects, and the welded area is stable and reliable.

[0061] Example 2: This example differs from Example 1 in that the welding speed in step three is 1.1 mm / s. Everything else is the same as in Example 1.

[0062] Figure 7 The image shows a cross-sectional scanning electron microscope (SEM) image of the Al2O3-TA2 welded component prepared in Example 2. As can be seen from the image, the Al2O3 and TA2 joints are well connected, but the welded area does not have a significant impact on the bottom of the sample. This process parameter can be used to connect the two components well without significantly affecting the bottom substrate of the parent material, which has advantages in specific working environments such as avoiding damage to the bottom substrate.

[0063] According to the GB / T39826-2021 test standard, the four-point bending strength of the Al2O3-TA2 welded part prepared in Example 2 is 94.6 MPa; Figure 8 The fracture surface diagrams of the Al2O3-TA2 welded parts prepared in Example 2 after a four-point bending test are shown in (1), which is a fracture surface morphology diagram of the fractured sample, and (2) and (3) are magnified views of local areas in (1). As can be seen from the figures, most of the fracture surface is transgranular fracture, and the sample near the bottom has a flat morphology. The laser has little effect on the sample at the bottom of the interface.

Claims

1. A method for ultrashort pulse laser welding of ceramics and metals, characterized in that... It is done in the following steps:

1. Cut the ceramics and metals separately to obtain suitable dimensions and smooth surfaces for welding; 2. Set the ceramic and metal surfaces to be welded parallel and opposite to each other, with a gap of 40μm between the two surfaces to be welded. Finally, use a bench vise to fix them to obtain the parts to be welded.

3. Place the workpiece to be welded on the xy-axis linked laser operating stage, adjust the laser focus to be above the ceramic, and the distance between the laser focus and the center of the joint gap is 50μm. Using an ultrashort pulse laser, weld under the conditions of room temperature, air atmosphere, pulse width of 300fs, repetition frequency of 1MHz, welding speed of 0.8mm / s, laser power of 23.77W, and laser defocusing amount of -200μm to obtain Al2O3-TA2 welded parts; The ceramic mentioned in step one is an alumina ceramic with a purity of 95%; The metal mentioned in step one is TA2 titanium alloy; The thickness of both the ceramic and metal mentioned in step one is 0.5 mm; Step one involves cutting the ceramic to obtain a suitable size and a smooth surface for welding. Specifically, this is done using a diamond wire cutter to cut the ceramic to a size of 15×2×0.5mm. 3 After cutting the sheet-like and smooth surfaces to be welded, place them in a 95% alcohol solution and ultrasonically clean them for 5 minutes at a power of 240W. Step one involves cutting the metal to obtain the appropriate size and a smooth surface for welding. Specifically, this is done using a wire EDM machine to cut the metal to a size of 15×2×0.5mm. 3 After cutting the sheet-like and smooth surfaces to be welded, place them in a 95% alcohol solution and ultrasonically clean them for 5 minutes at a power of 240W. The wavelength of the ultrashort pulse laser mentioned in step three is 1030 nm.

Images