A soldering flux for soldering ceramic to ceramic, a method for soldering ceramic to ceramic, and a ceramic piece

Abstract

The application provides a soldering flux for soldering ceramics to ceramics, a ceramic-to-ceramic soldering preparation method and a ceramic piece, the soldering flux containing titanium dioxide, carbon, metallic cobalt and / or cobalt oxide, and the molar ratio of titanium element to cobalt element in the soldering flux being 1:7-1:14. The soldering flux has a low soldering temperature and high soldering strength when soldering zirconia ceramics or alumina ceramics.

Description

Technical Field

[0001] This application relates to a flux for welding ceramics to ceramics, specifically in the field of ceramic to ceramic welding. Background Technology

[0002] Ceramics possess high strength, high hardness, wear resistance, and excellent high-temperature mechanical properties and thermal stability, making them widely used in aerospace, energy, electronics, and automotive fields. However, Si3N4 ceramics are brittle, difficult to deform, and challenging to machine. Furthermore, the inherent brittleness of ceramic materials easily leads to extremely small critical cracks, further complicating their processing and making it difficult to manufacture complex shapes, thus limiting their applications.

[0003] Metal brazing technology is widely used for joining ceramic components due to its advantages such as simple operation, low investment cost, good dimensional adaptability, and high joint strength. AgCuTi series active brazing alloys possess excellent welding performance and superior room temperature bending resistance, making them the most widely used active fluxes. However, the cost of currently used AgCuTi active brazing alloy fluxes is relatively high, which is not conducive to large-scale industrial production.

[0004] Existing technologies disclose a ceramic flux containing carbon and metal, but these fluxes suffer from high welding temperatures or relatively poor welding strength when welding zirconia or alumina ceramics. Summary of the Invention

[0005] Therefore, this application provides a ceramic flux with a low welding temperature and high welding strength when welding zirconia ceramics or alumina ceramics.

[0006] The present invention provides a flux for welding ceramics to ceramics, the flux containing titanium dioxide, carbon, metallic cobalt and / or cobalt oxide, wherein the molar ratio of titanium to cobalt in the flux is 1:7-1:14, preferably in the range of 1:9-1:10.

[0007] Optionally, when the flux contains titanium dioxide, carbon, and metallic cobalt, the molar ratio of carbon to metallic cobalt in the flux is 1:1.5-1:4, preferably in the range of 1:2-1:3.

[0008] Optionally, when the flux contains titanium dioxide, carbon, and cobalt oxide, the molar ratio of carbon to cobalt in the flux is 2:1-3:4, preferably in the range of 3:2-1:1.

[0009] Optionally, the ceramic is zirconia ceramic or alumina ceramic.

[0010] The present invention also provides a method for preparing ceramic-ceramic welding, which includes the following steps:

[0011] (1) Clean the ceramic parts to be welded;

[0012] (2) The ceramic parts are assembled in the order of ceramic parts / fuse / ceramic parts from top to bottom, and pressure is applied to the surface of the ceramic parts to fix them. The assembled workpiece is placed in a vacuum heating furnace. The flux is the aforementioned flux.

[0013] (3) Vacuum sintering for 20-40 minutes;

[0014] (4) Cool to room temperature to obtain ceramic-ceramic welded parts.

[0015] Optionally, in step (2), a pressure of 0.5-1 MPa is applied to the surface of the ceramic part for fixing.

[0016] Optionally, the vacuum sintering temperature in step (3) is 1350-1480℃. After heating to 1350-1480℃ at a rate of 15℃ / min from room temperature, the temperature is held for 20-40 minutes, and then cooled to 400℃ at a rate of 15℃ / min, and then cooled to room temperature with the furnace.

[0017] Optionally, the vacuum degree is 1×10 -3 -8×10 -3 Pa.

[0018] The present invention also provides a ceramic part comprising a first ceramic body, a transition layer and a second ceramic body stacked sequentially, wherein the transition layer comprises titanium carbide, cobalt carbide, carbon and cobalt.

[0019] The ceramic parts described above were prepared by the aforementioned method.

[0020] Through extensive experiments, the inventors of this invention discovered that, at high temperatures, if the flux contains titanium dioxide, carbon, and metallic cobalt, some of the carbon will penetrate into the ceramic. Both the cobalt and titanium dioxide in the flux react with the carbon. This reaction occurs inside the flux and at the interface between the flux and the ceramic. The resulting cobalt carbide has a relatively strong bond with the ceramic, while the reacted titanium carbide has a certain solubility in the molten cobalt, thus strengthening the weld layer.

[0021] If the flux contains cobalt oxide, the carbon will reduce the cobalt oxide to cobalt, repeating the reaction principle described above when the flux contains titanium dioxide, carbon, and metallic cobalt, thereby strengthening the weld strength between ceramics. Detailed Implementation

[0022] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0023] The present invention provides a flux for welding ceramics to ceramics, the flux containing titanium dioxide, carbon, metallic cobalt and / or cobalt oxide, wherein the molar ratio of titanium to cobalt in the flux is 1:7-1:14, preferably in the range of 1:9-1:10.

[0024] Through extensive experimentation, the inventors of this invention discovered that, at high temperatures, when the flux contains titanium dioxide, carbon, and metallic cobalt, some of the carbon will penetrate into the ceramic. Both the cobalt and titanium dioxide in the flux react with the carbon. This reaction occurs both inside the flux and at the interface between the flux and the ceramic. The resulting cobalt carbide has a strong bond with the ceramic, while the reacted titanium carbide has a certain solubility in molten cobalt, thus strengthening the weld layer. If the flux contains cobalt oxide, the carbon will at least partially reduce the cobalt oxide to cobalt, repeating the reaction principle described above when the flux contains titanium dioxide, carbon, and metallic cobalt, thereby strengthening the weld strength between ceramics.

[0025] The cobalt content is much higher than the titanium content. Cobalt not only participates in the formation of cobalt carbide, but also forms a molten cobalt solution to dissolve titanium carbide. Carbon not only penetrates the ceramic interface to enhance the welding strength of the flux, but also participates in the reaction with cobalt to form cobalt carbide and with titanium to form titanium carbide. Titanium dioxide can react to form titanium carbide at a low sintering temperature, and titanium carbide strengthens the welding strength. Therefore, the combination of titanium dioxide, carbon, metallic cobalt and / or cobalt oxide in this invention allows the components to support each other, forming a flux with better welding effect.

[0026] Alternatively, the carbon may be toner commonly used by those skilled in the art.

[0027] Optionally, when the flux contains titanium dioxide, carbon, and metallic cobalt, the molar ratio of carbon to metallic cobalt in the flux is 1:1.5-1:4, preferably in the range of 1:2-1:3.

[0028] Optionally, when the flux contains titanium dioxide, carbon, and cobalt oxide, the molar ratio of carbon to cobalt in the flux is 2:1-3:4, preferably 3:2-2:1. Because when carbon is present in the composition containing cobalt oxide, some of the cobalt oxide needs to be reduced to cobalt, repeating the reaction principle described above when the flux contains titanium dioxide, carbon, and metallic cobalt, the content of carbon oxide in the flux composition is higher than that in a flux composition containing only cobalt.

[0029] Optionally, the ceramic is a zirconia ceramic or an alumina ceramic, which are common in the field. Zirconia ceramics or alumina ceramics have stable properties and a wide range of applications. In particular, electronic products often use zirconia ceramics or alumina ceramics.

[0030] The present invention also provides a method for preparing ceramic-ceramic welding, which includes the following steps:

[0031] (1) Clean the ceramic parts to be welded;

[0032] (2) Assemble the ceramic parts in the order of ceramic parts / fuse / ceramic parts from top to bottom, apply pressure to the surface of the ceramic parts to fix them, and put the assembled workpiece into a vacuum heating furnace.

[0033] (3) Vacuum sintering for 20-40 minutes;

[0034] (4) Cool to room temperature to obtain ceramic-ceramic welded parts.

[0035] The cleaning method in step (1) above is a common method for cleaning ceramic parts that is known to those skilled in the art, such as degreasing, washing with water, and drying.

[0036] Optionally, the vacuum sintering temperature is 1350–1480℃. The sintering temperature used in this invention is a relatively low range. Some existing ceramic fluxes require welding temperatures as high as 1700℃ or even above, consuming a large amount of energy and placing high demands on equipment. However, the flux of this invention has a reasonable composition, as analyzed above. Therefore, the relatively low sintering temperature of 1350–1480℃ used in this invention reduces energy consumption and lowers the requirements for sintering equipment, which is beneficial for large-scale production.

[0037] Optionally, the vacuum level in the vacuum heating furnace is within the range of 1×10⁻⁶, which is common to those skilled in the art. -3 -8×10 -3 Pa.

[0038] Optionally, the heating and cooling rates are common heating and cooling operations in the art. Those skilled in the art can heat the material to 1350–1480°C at a rate of 15°C / min from room temperature, hold it at that temperature for 20–40 min, and then cool it to 400°C at a rate of 15°C / min, subsequently cooling it to room temperature with the furnace. This is a common heating and cooling rate and operation method in the preparation of ceramics and ceramic welding, and will not be elaborated further here.

[0039] This invention also provides a ceramic part comprising a first ceramic body, a transition layer, and a second ceramic body stacked sequentially. The transition layer comprises titanium carbide, cobalt carbide, carbon, and cobalt. The transition layer is prepared by flux. This transition layer may also contain cobalt oxide and other substances, but the inventors believe that the titanium carbide, cobalt carbide, carbon, and cobalt are primarily responsible for the welding process; if the carbon content is sufficient, even if the flux initially contains cobalt oxide, the cobalt oxide will ultimately react completely to form metallic cobalt and cobalt carbide after the sintering reaction.

[0040] The ceramic part is prepared by the aforementioned method.

[0041] The workpiece of the present invention will be described in detail below with reference to specific embodiments.

[0042] Example 1:

[0043] (1) Clean two zirconia ceramic parts, each 5cm long, 5cm wide, and 1.2cm high. Weigh 1 gram of titanium dioxide (i.e., 0.0125 mol of titanium dioxide), 0.8 grams of carbon powder (i.e., 0.067 mol of carbon), and 5.9 grams of metallic cobalt (i.e., 0.1 mol of metallic cobalt) and mix them evenly to form a flux;

[0044] (2) Take a ceramic part, place flux in a welding area 2cm long and 2cm wide, press another ceramic part on the flux, and assemble in the form of ceramic part / flux / ceramic part from top to bottom. Apply a pressure of 1MPa to the surface of the ceramic part to fix it. Place the assembled workpiece in a vacuum heating furnace, and adjust the vacuum degree in the vacuum furnace to 1×10 -3 Pa;

[0045] (3) Start heating from room temperature to 1350℃ at a rate of 15℃ / min, hold for 25min, then cool down to 400℃ at a rate of 15℃ / min, and then cool down to room temperature with the furnace to obtain the ceramic-ceramic welded parts.

[0046] Example 2

[0047] The difference from Example 1 is that:

[0048] (1) Weigh 0.3 g of titanium dioxide (i.e., 0.0037 mol of titanium dioxide), 0.72 g of carbon powder (i.e., 0.06 mol of carbon), and 7.22 g of cobalt oxide (i.e., 0.03 mol of cobalt oxide) and mix them evenly to form a flux.

[0049] Example 3:

[0050] The difference from Example 1 is that:

[0051] (1) Weigh 0.3 g of titanium dioxide (i.e., 0.0037 mol of titanium dioxide), 0.72 g of carbon powder (i.e., 0.06 mol of carbon), 2.95 g of metallic cobalt (i.e., 0.05 mol of metallic cobalt), and 3.61 g of cobalt oxide (i.e., 0.015 mol of cobalt oxide) and mix them evenly to form a flux.

[0052] Example 4:

[0053] The difference from Example 1 is that:

[0054] (1) Weigh 0.8 g of titanium dioxide (i.e., 0.01 mol of titanium dioxide), 0.6 g of carbon powder (i.e., 0.05 mol of carbon), and 5.9 g of metallic cobalt (i.e., 0.1 mol of metallic cobalt) and mix them evenly to form a flux.

[0055] Example 5:

[0056] The difference from Example 2 is that:

[0057] (1) Weigh 0.8 g of titanium dioxide (i.e., 0.01 mol of titanium dioxide), 0.6 g of carbon powder (i.e., 0.05 mol of carbon), and 7.95 g of cobalt oxide (i.e., 0.033 mol of cobalt oxide) and mix them evenly to form a flux.

[0058] Example 6:

[0059] The difference from Example 1 is that the ceramic part is made of alumina ceramic.

[0060] Example 7:

[0061] The difference from Example 1 is that:

[0062] (1) Heat the room temperature to 1480℃ at a rate of 15℃ / min, hold for 40min, and then heat at 15℃ / min.

[0063] The temperature is reduced to 400℃ at a rate of 1 / min, and then cooled to room temperature with the furnace to obtain ceramic-ceramic welded parts.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that:

[0066] Weigh 0.48 grams of metallic titanium (i.e., 0.01 mol of metallic titanium), 0.6 grams of carbon powder (i.e., 0.05 mol of carbon), and 5.9 grams of metallic cobalt (i.e., 0.1 mol of metallic cobalt) and mix them evenly to form a flux.

[0067] Comparative Example 2

[0068] The difference from Example 1 is that:

[0069] (1) Weigh 1.6 g of titanium dioxide (i.e., 0.02 mol of titanium dioxide), 0.6 g of carbon powder (i.e., 0.05 mol of carbon), and 5.9 g of metallic cobalt (i.e., 0.1 mol of metallic cobalt) and mix them evenly to form a flux.

[0070] Performance testing

[0071] The fluxes obtained in Examples 1-7 and Comparative Examples 1-2 were subjected to performance tests, including tests for cracking at the weld joint and weld tensile strength tests. The results are shown in Table 1.

[0072] The testing method is as follows:

[0073] 1. Room temperature shear strength

[0074] The ceramic-ceramic welded parts are stretched on a tensile testing machine to test the shear force at which the weld joint is torn.

[0075] 2. Weld joint crack test: visual inspection and optical magnification.

[0076] Table 1

[0077] Test Project Are there cracks at the weld? Room temperature shear strength (MPa) Example 1 none 56 Example 2 none 69 Example 3 none 54 Example 4 none 73 Example 5 none 74 Example 6 none 52 Example 7 none 51 Comparative Example 1 none 12 Comparative Example 2 cracking ——

[0078] According to the embodiments and comparative examples of the present invention, and the test results in Table 1, the flux of the present invention contains titanium dioxide, carbon, metallic cobalt, and / or cobalt oxide. At high temperatures, if the flux contains titanium dioxide, carbon, and metallic cobalt, some carbon will penetrate into the ceramic. Both cobalt and titanium dioxide in the flux react with carbon. This reaction occurs inside the flux and at the interface between the flux and the ceramic. The resulting cobalt carbide has a strong bond with the ceramic, and the reacted titanium carbide has a certain solubility in the molten cobalt, strengthening the strength of the weld layer to over 50 MPa, making it suitable for large-scale industrial welding of ceramic parts in electronic products. In contrast, Comparative Example 1 contains metallic titanium, and the sample obtained at a sintering temperature of 1350°C showed poor welding performance. The inventors of the present invention presume that because the sintering temperature is not high, the metallic titanium did not react at this temperature, and titanium carbide was not generated; therefore, the welding performance was poor. In Comparative Example 2, excessive titanium dioxide resulted in cracking at the weld joint. The inventors of this invention presume that since titanium dioxide is in powder form, even under high-temperature sintering, some of the excess titanium dioxide cannot participate in the reaction. Furthermore, the excess titanium dioxide occupies space, reducing the contact area between the solder and the ceramic, thus leading to poor welding performance and cracking at the weld joint. Moreover, the welding flux in this specific embodiment can be used for welding in the lower temperature range of 1350–1480°C, without requiring temperatures of 1700°C or higher, and the welding strength is high, reaching over 50 MPa.

[0079] The above description is an exemplary embodiment of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A flux for welding ceramics to ceramics, characterized in that, The flux contains titanium dioxide, carbon, metallic cobalt and / or cobalt oxide, and the molar ratio of titanium to cobalt in the flux is 1:7 to 1:

14.

2. The flux according to claim 1, characterized in that, The molar ratio of titanium to cobalt in the flux is 1:9 to 1:

10.

3. The flux according to claim 1, characterized in that, When the flux contains titanium dioxide, carbon, and metallic cobalt, the molar ratio of carbon to metallic cobalt in the flux is 1:1.5-1:

4.

4. The flux according to claim 1, characterized in that, When the flux contains titanium dioxide, carbon, and metallic cobalt, the molar ratio of carbon to metallic cobalt in the flux is 1:2 to 1:

3.

5. The flux according to claim 1, characterized in that, When the flux contains titanium dioxide, carbon, and cobalt oxide, the molar ratio of carbon to cobalt in the flux is 2:1 to 3:

4.

6. The flux according to claim 1, characterized in that, When the flux contains titanium dioxide, carbon, and cobalt oxide, the molar ratio of carbon to cobalt in the flux is 3:2 to 2:

1.

7. The flux according to claim 1, characterized in that, The ceramic is either zirconia ceramic or alumina ceramic.

8. A method for preparing ceramic-to-ceramic welding, comprising the following steps: (1) Clean the ceramic parts to be welded; (2) The ceramic parts are assembled in the form of ceramic parts / flux / ceramic parts from bottom to top, and pressure is applied to the surface of the ceramic parts to fix them. The assembled workpiece is placed in a vacuum heating furnace. The flux is the flux for welding ceramics to ceramics as described in any one of claims 1-7. (3) Vacuum sintering for 20-40 minutes; (4) Cool to room temperature to obtain the welded ceramic part.

9. The method for preparing ceramics by welding according to claim 8, characterized in that, In step (2), a pressure of 0.5-1 MPa is applied to the surface of the ceramic part for fixation.

10. The method for preparing ceramics by welding according to claim 8, characterized in that, In step (3), the vacuum sintering temperature is 1350~1480℃. After heating to 1350~1480℃ at a rate of 15℃ / min from room temperature, the temperature is held for 20-40min, and then cooled to 400℃ at a rate of 15℃ / min, and then cooled to room temperature with the furnace.

11. The method for preparing ceramics by welding according to claim 8, characterized in that, Vacuum degree is 1×10 -3 -8×10 -3 Pa.

12. A ceramic part comprising a first ceramic body, a transition layer, and a second ceramic body stacked sequentially, wherein the transition layer comprises titanium carbide, cobalt carbide, carbon, and cobalt, and the ceramic part is prepared by the method of claim 8.