Silicon carbide ceramic welding method and silicon carbide ceramic welding joint

Abstract

The invention provides a silicon carbide ceramic welding method and a silicon carbide ceramic welding joint, and relates to the technical field of welding, the welding method comprises the following steps: preparing a carbon layer on the surface of silicon carbide ceramic to obtain carbon-coated silicon carbide ceramic; brazing filler metal is placed between the two pieces of carbon-coated silicon carbide ceramics, and a to-be-welded piece is obtained; the brazing filler metal is Si-Pr eutectic brazing filler metal; and under the vacuum condition, the to-be-welded part is heated to the first temperature at the first heating rate, heat preservation is conducted for the first time, then the to-be-welded part is heated to the second temperature at the second heating rate, heat preservation is conducted for the second time, the to-be-welded part is cooled to the room temperature, and the silicon carbide ceramic welded joint is obtained. For the brazing of the silicon carbide ceramic, a welding joint with higher strength can be obtained by adopting the welding method provided by the invention.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and in particular to a welding method for silicon carbide ceramics and a silicon carbide ceramic welded joint. Background Art

[0002] Silicon carbide ceramics have excellent physical and electrical properties and are important materials for semiconductor devices and high-temperature structural parts. However, their high hardness and brittleness make processing difficult, especially challenging in terms of high-reliability connections. Brazing, as a connection process, can achieve the connection between metal and ceramic at relatively low temperatures, with the advantages of simple process and high efficiency. However, the thermal expansion coefficients of the currently widely used metal brazing filler metals and silicon carbide ceramics are quite different, which can easily cause interfacial residual stress during the cooling process, leading to cracking of the welded joint, affecting the strength of the welded joint. In addition, conventional brazing filler metals have poor wettability and weak interface reactions, resulting in low connection strength of the welded joint, which is difficult to meet the needs of high-reliability applications. Summary of the Invention

[0003] The problem solved by the present invention is: how to obtain a weld joint with higher strength for the brazing of silicon carbide ceramics.

[0004] To solve the above problems, the present invention provides a method for welding silicon carbide ceramics, comprising: Step S1, preparing a carbon layer on the surface of silicon carbide ceramics to obtain carbon-coated silicon carbide ceramics; Step S2, placing a brazing filler metal between the two carbon-coated silicon carbide ceramics to obtain a workpiece to be welded; the brazing filler metal is a Si-Pr eutectic brazing filler metal, wherein the molar percentage of Pr is 17% and the molar percentage of Si is 83%; Step S3: Under vacuum or inert gas protection conditions, heating the workpiece to be welded to a first temperature at a first heating rate, keeping it at that temperature for a first time, then heating it to a second temperature at a second heating rate, keeping it at that temperature for a second time, and cooling it to room temperature to obtain a silicon carbide ceramic welded joint.

[0005] Optionally, in step S1, preparing a carbon layer on the surface of the silicon carbide ceramic to obtain a carbon-coated silicon carbide ceramic includes: Step S11, placing the silicon carbide ceramic in a phenolic resin precursor solution, soaking it, and then performing a first heating treatment to obtain a pretreated silicon carbide ceramic; Step S12: Under vacuum conditions, the pretreated silicon carbide ceramic is subjected to a second heating treatment to obtain the carbon-coated silicon carbide ceramic.

[0006] Optionally, in step S11, the phenolic resin precursor solution is composed of phenolic resin and organic solvent in a mass ratio of 1:(1 to 5).

[0007] Optionally, in step S11, the temperature of the first heating treatment is 70° C. to 90° C., and the time is 50 min to 70 min.

[0008] Optionally, in step S12, the temperature of the second heating treatment is 650° C. to 900° C., and the time is 10 min to 30 min.

[0009] Optionally, in step S1, the thickness of the carbon layer is 0.1 μm to 10 μm.

[0010] Optionally, in step S2, the thickness of the solder is 0.2 mm to 0.6 mm.

[0011] Optionally, in step S1, the thickness of the silicon carbide ceramic is 5 mm to 20 mm.

[0012] Optionally, in step S3, the first heating rate is 8°C / min to 10°C / min, the first temperature is 790°C to 810°C, and the first time is 8 min to 12 min; the second heating rate is 4°C / min to 6°C / min, the second temperature is 1260°C to 1350°C, and the second time is 15 min to 30 min.

[0013] The present invention also provides a silicon carbide ceramic welded joint, which is manufactured using the above-mentioned silicon carbide ceramic welding method.

[0014] Compared to related art, the present invention uses a Si-Pr eutectic brazing filler metal for welding silicon carbide ceramics. The molar percentage of Pr in the Si-Pr eutectic brazing filler metal is 17% and the molar percentage of Si is 83%. The Si-Pr eutectic brazing filler metal has a melting point of 1212°C, good high-temperature stability, and a low thermal expansion coefficient. It has good compatibility with silicon carbide ceramics, effectively reducing thermal stress in the weld joint and preventing cracking, thereby improving the strength of the weld joint. Furthermore, Pr and Si easily form stable intermetallic compounds (such as PrSi2), which help enhance the structural density and oxidation resistance of the weld joint, further improving the strength of the weld joint. Furthermore, to overcome the problem of insufficient brazing filler metal wettability, the present invention prepares a carbon layer on the surface of the silicon carbide ceramic, effectively enhancing the brazing filler metal's wettability on the silicon carbide ceramic surface and increasing the diffusion reaction activity, thereby further improving the strength of the weld joint. In summary, for brazing silicon carbide ceramics, the welding method provided by the present invention can produce a weld joint with higher strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1Schematic diagram of the process of welding silicon carbide ceramics according to an embodiment of the present invention; Figure 2 This is a scanning electron microscope analysis image of the silicon carbide ceramic welded joint prepared in Example 1; Figure 3 This is a scanning electron microscope analysis image of the silicon carbide ceramic welded joint prepared in Comparative Example 1. DETAILED DESCRIPTION

[0016] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0017] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0018] The term "including" and its variations used in this document are open inclusions, that is, "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first" and "second" mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0019] like Figure 1 As shown, an embodiment of the present invention provides a method for welding silicon carbide ceramics, comprising: Step S1, preparing a carbon layer on the surface of silicon carbide ceramics to obtain carbon-coated silicon carbide ceramics; Step S2, placing a solder between the two carbon-coated silicon carbide ceramics to obtain a sandwich structure to be welded; the solder is a Si-Pr eutectic solder, and the molar percentage of Pr in the Si-Pr eutectic solder is 17%, and the molar percentage of Si is 83%; Step S3: Under vacuum or inert gas protection conditions, heating the workpiece to be welded to a first temperature at a first heating rate, keeping it at that temperature for a first time, then heating it to a second temperature at a second heating rate, keeping it at that temperature for a second time, and cooling it to room temperature to obtain a silicon carbide ceramic welded joint.

[0020] The present invention utilizes a Si-Pr eutectic brazing filler metal for welding silicon carbide ceramics. The Si-Pr eutectic brazing filler metal contains a molar percentage of Pr of 17% and a molar percentage of Si of 83%. This Si-Pr eutectic brazing filler metal has a melting point of 1212°C, excellent high-temperature stability, and a low coefficient of thermal expansion. It is well compatible with silicon carbide ceramics, effectively reducing thermal stress in welded joints and preventing cracking, thereby improving the strength of the welded joints. Furthermore, Pr and Si readily form stable intermetallic compounds (such as PrSi₂), which enhance the structural density and oxidation resistance of the welded joints, further improving the strength of the welded joints. Furthermore, to overcome the problem of insufficient brazing filler metal wettability, the present invention utilizes a carbon layer formed on the surface of the silicon carbide ceramics. This effectively enhances the brazing filler metal's wettability on the surface of the silicon carbide ceramics and improves the diffusion reaction activity, thereby further improving the strength of the welded joints. In summary, the brazing method provided by the present invention can achieve high-strength welded joints for brazing silicon carbide ceramics.

[0021] In some embodiments of the present invention, illustratively, the Si-Pr eutectic solder is prepared by melting silicon and metal Pr as raw materials.

[0022] In some embodiments of the present invention, in step S1, preparing a carbon layer on the surface of the silicon carbide ceramic to obtain a carbon-coated silicon carbide ceramic comprises: Step S11, placing the silicon carbide ceramic in a phenolic resin precursor solution, soaking it, and then performing a first heating treatment to obtain a pretreated silicon carbide ceramic; Step S12: Under vacuum conditions, the pretreated silicon carbide ceramic is subjected to a second heating treatment to obtain the carbon-coated silicon carbide ceramic.

[0023] In some embodiments of the present invention, in step S11, the phenolic resin precursor solution is composed of phenolic resin and organic solvent in a mass ratio of 1:(1 to 5).

[0024] In some embodiments of the present invention, in step S11, the temperature of the first heating treatment is 70° C. to 90° C., and the time is 50 min to 70 min.

[0025] In some embodiments of the present invention, in step S12, the temperature of the second heating treatment is 650° C. to 900° C., and the time is 10 min to 30 min.

[0026] In some embodiments of the present invention, in step S1 , the thickness of the carbon layer is 0.1 μm to 10 μm.

[0027] In some embodiments of the present invention, in step S2, the thickness of the solder is 0.2 mm to 0.6 mm.

[0028] In some embodiments of the present invention, in step S1, the thickness of the silicon carbide ceramic is 5 mm to 20 mm.

[0029] In some embodiments of the present invention, in step S3, the first heating rate is 8°C / min to 10°C / min, the first temperature is 790°C to 810°C, and the first time is 8 min to 12 min; the second heating rate is 4°C / min to 6°C / min, the second temperature is 1260°C to 1350°C, and the second time is 15 min to 30 min.

[0030] An embodiment of the present invention further provides a silicon carbide ceramic welded joint, which is manufactured using the above-mentioned silicon carbide ceramic welding method.

[0031] The present invention is further described below with reference to specific embodiments.

[0032] Example 1 A1. Place silicon carbide ceramic in a phenolic resin precursor solution, soak it, and then perform a first heat treatment to obtain pretreated silicon carbide ceramic; wherein the silicon carbide ceramic is in a sheet shape with a thickness of 20 mm, the phenolic resin precursor solution is composed of phenolic resin and anhydrous ethanol as an organic solvent in a mass ratio of 1:1, the soaking time is 24 hours, and the first heat treatment temperature is 80°C and the time is 60 minutes.

[0033] A2. Under vacuum conditions, the pretreated silicon carbide ceramic is subjected to a second heating treatment to obtain the carbon-coated silicon carbide ceramic; the temperature of the second heating treatment is 820° C., and the time is 20 min.

[0034] A3. Placing a brazing filler metal between the two carbon-coated silicon carbide ceramics to obtain a sandwich structure to be welded; wherein the brazing filler metal is a Si-Pr eutectic filler metal, wherein the molar percentage of Pr in the Si-Pr eutectic filler metal is 17% and the molar percentage of Si is 83%; the brazing filler metal is a sheet foil material having a thickness of 0.4 mm. A4. Under vacuum conditions, the workpiece to be welded is heated to a first temperature at a first heating rate, kept warm for a first time, then heated to a second temperature at a second heating rate, kept warm for a second time, then cooled to 800°C at a cooling rate of 5°C / min, and to 400°C at a cooling rate of 10°C / min, and cooled to room temperature with the furnace to obtain a silicon carbide ceramic welded joint; wherein, the first heating rate is 10°C / min, the first temperature is 800°C, and the first time is 10 minutes; the second heating rate is 5°C / min, the second temperature is 1280°C, and the second time is 15 minutes.

[0035] Example 2 A1. Place silicon carbide ceramics in a phenolic resin precursor solution, soak them, and then perform a first heat treatment to obtain pretreated silicon carbide ceramics; wherein the silicon carbide ceramics are in a sheet shape with a thickness of 20 mm, the phenolic resin precursor solution is composed of a phenolic resin and an organic solvent, anhydrous ethanol, in a mass ratio of 1:1, the soaking time is 24 hours, and the first heat treatment temperature is 70°C and the time is 70 minutes.

[0036] A2. Under vacuum conditions, the pretreated silicon carbide ceramic is subjected to a second heating treatment to obtain the carbon-coated silicon carbide ceramic; the temperature of the second heating treatment is 900° C., and the time is 10 minutes.

[0037] A3. Placing a brazing filler metal between the two carbon-coated silicon carbide ceramics to obtain a sandwich structure to be welded; wherein the brazing filler metal is a Si-Pr eutectic filler metal, wherein the molar percentage of Pr in the Si-Pr eutectic filler metal is 17% and the molar percentage of Si is 83%; the brazing filler metal is a sheet foil material having a thickness of 0.4 mm. A4. Under vacuum conditions, the workpiece to be welded is heated to a first temperature at a first heating rate, kept warm for a first time, then heated to a second temperature at a second heating rate, kept warm for a second time, then cooled to 800°C at a cooling rate of 4°C / min, and to 400°C at a cooling rate of 10°C / min, and cooled to room temperature with the furnace to obtain a silicon carbide ceramic welded joint; wherein, the first heating rate is 8°C / min, the first temperature is 790°C, and the first time is 12 minutes; the second heating rate is 4°C / min, the second temperature is 1260°C, and the second time is 30 minutes.

[0038] Example 3 A1. Place silicon carbide ceramic in a phenolic resin precursor solution, soak it, and then perform a first heat treatment to obtain pretreated silicon carbide ceramic; wherein the silicon carbide ceramic is in a sheet shape with a thickness of 20 mm, the phenolic resin precursor solution is composed of phenolic resin and anhydrous ethanol as an organic solvent in a mass ratio of 1:1, the soaking time is 24 hours, and the first heat treatment temperature is 90°C and the time is 50 minutes.

[0039] A2. Under vacuum conditions, the pretreated silicon carbide ceramic is subjected to a second heating treatment to obtain the carbon-coated silicon carbide ceramic; the temperature of the second heating treatment is 650° C., and the time is 30 minutes.

[0040] A3. Placing a brazing filler metal between the two carbon-coated silicon carbide ceramics to obtain a sandwich structure to be welded; wherein the brazing filler metal is a Si-Pr eutectic filler metal, wherein the molar percentage of Pr in the Si-Pr eutectic filler metal is 17% and the molar percentage of Si is 83%; the brazing filler metal is a sheet foil material having a thickness of 0.4 mm. A4. Under vacuum conditions, the workpiece to be welded is heated to a first temperature at a first heating rate, kept warm for a first time, then heated to a second temperature at a second heating rate, kept warm for a second time, then cooled to 800°C at a cooling rate of 4°C / min, and to 400°C at a cooling rate of 10°C / min, and cooled to room temperature with the furnace to obtain a silicon carbide ceramic welded joint; wherein, the first heating rate is 9°C / min, the first temperature is 810°C, and the first time is 8 minutes; the second heating rate is 5°C / min, the second temperature is 1350°C, and the second time is 15 minutes.

[0041] Comparative Example 1 A solder is placed between two silicon carbide ceramics (with a carbon layer prepared on their surfaces) to obtain a sandwich structured part to be welded; wherein the solder is a Si-Pr eutectic solder, wherein the molar percentage of Pr in the Si-Pr eutectic solder is 17% and the molar percentage of Si is 83%; the solder is a sheet foil material with a thickness of 0.4 mm.

[0042] Under vacuum conditions, the workpiece to be welded is heated to a first temperature at a first heating rate, kept warm for a first time, then heated to a second temperature at a second heating rate, kept warm for a second time, then cooled to 800°C at a cooling rate of 5°C / min, and to 400°C at a cooling rate of 10°C / min, and cooled to room temperature with the furnace to obtain a silicon carbide ceramic welded joint; wherein, the first heating rate is 10°C / min, the first temperature is 800°C, and the first time is 10 minutes; the second heating rate is 5°C / min, the second temperature is 1280°C, and the second time is 15 minutes.

[0043] Comparative Example 2 The difference from Example 1 is that in step A3, the solder is a Zr-Ni solder, and the molar percentage of Zr in the Zr-Ni solder is 76%, and the molar percentage of Ni is 24%.

[0044] Experimental example The results of scanning electron microscopy characterization of the silicon carbide ceramic welded joints prepared in Example 1 and Comparative Example 1 are shown in FIG. Figure 2 and Figure 3 ,from Figure 2 It can be seen that the silicon carbide ceramic welded joint prepared in Example 1 is continuous and has no defects such as pores and cracks. The silicon element in the brazing material reacts with the surface carbon layer to form silicon carbide as the connection interface. The weld is composed of a mixed structure of PrSi2 and Si. Figure 3 It can be seen that the silicon carbide ceramic welded joint prepared in Comparative Example 1 is continuous, without defects such as pores and cracks. The weld is composed of a mixed structure of PrSi2 and Si. No new compounds are formed at the interface, and the interface is directly connected by the brazing filler metal and the base material.

[0045] The shear strength of the silicon carbide ceramic welded joints prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested, and the results are shown in Table 1. As can be seen from Table 1, the shear strength of the silicon carbide ceramic welded joints prepared in Examples 1 to 3 is higher than that in Comparative Examples 1 to 2.

[0046] Table 1

[0047] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for welding silicon carbide ceramics, characterized in that: include: Step S1, preparing a carbon layer on the surface of silicon carbide ceramics to obtain carbon-coated silicon carbide ceramics; Step S2, placing a brazing filler metal between the two carbon-coated silicon carbide ceramics to obtain a workpiece to be welded; the brazing filler metal is a Si-Pr eutectic brazing filler metal, wherein the molar percentage of Pr is 17% and the molar percentage of Si is 83%; Step S3: Under vacuum or inert gas protection conditions, heating the workpiece to be welded to a first temperature at a first heating rate, keeping it at that temperature for a first time, then heating it to a second temperature at a second heating rate, keeping it at that temperature for a second time, and cooling it to room temperature to obtain a silicon carbide ceramic welded joint.

2. The method for welding silicon carbide ceramics according to claim 1, wherein: In step S1, the carbon layer is prepared on the surface of the silicon carbide ceramic to obtain the carbon-coated silicon carbide ceramic, comprising: Step S11, placing the silicon carbide ceramic in a phenolic resin precursor solution, soaking it, and then performing a first heating treatment to obtain a pretreated silicon carbide ceramic; Step S12: Under vacuum conditions, the pretreated silicon carbide ceramic is subjected to a second heating treatment to obtain the carbon-coated silicon carbide ceramic.

3. The method for welding silicon carbide ceramics according to claim 2, wherein: In the step S11, the phenolic resin precursor solution is composed of phenolic resin and organic solvent in a mass ratio of 1: (1 to 5).

4. The method for welding silicon carbide ceramics according to claim 2, wherein: In the step S11, the temperature of the first heating treatment is 70° C. to 90° C., and the time is 50 min to 70 min.

5. The method for welding silicon carbide ceramics according to claim 2, wherein: In the step S12, the temperature of the second heating treatment is 650° C. to 900° C., and the time is 10 min to 30 min.

6. The method for welding silicon carbide ceramics according to claim 1, wherein: In the step S1 , the thickness of the carbon layer is 0.1 μm to 10 μm.

7. The method for welding silicon carbide ceramics according to claim 1, wherein: In step S2, the thickness of the solder is 0.2 mm to 0.6 mm.

8. The method for welding silicon carbide ceramics according to claim 1, wherein: In the step S1, the thickness of the silicon carbide ceramic is 5 mm to 20 mm.

9. The method for welding silicon carbide ceramics according to claim 1, wherein: In step S3, the first heating rate is 8°C / min to 10°C / min, the first temperature is 790°C to 810°C, and the first time is 8 min to 12 min; the second heating rate is 4°C / min to 6°C / min, the second temperature is 1260°C to 1350°C, and the second time is 15 min to 30 min.

10. A silicon carbide ceramic welded joint, characterized in that: The silicon carbide ceramic is manufactured by the welding method according to any one of claims 1 to 9.

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