Reaction sintering silicon carbide ceramic connecting piece and preparation method thereof

Abstract

The invention belongs to the technical field of silicon carbide ceramic connecting pieces, and discloses a reaction sintered silicon carbide ceramic connecting piece and a preparation method thereof.The reaction sintered silicon carbide ceramic connecting piece is prepared by the steps that mixed slurry composed of SiC powder and a phenolic resin solution is evenly coated between reaction sintered silicon carbide ceramic base materials, assembling is conducted, then heat preservation cracking at 700-1000 DEG C and infiltration connection at 1330-1400 DEG C are conducted in a vacuum atmosphere, and the reaction sintered silicon carbide ceramic connecting piece is obtained. The thermal expansion coefficient of the connecting piece is matched with the elastic modulus, so that the interface residual stress of the connecting piece is obviously smaller than that of a connecting layer prepared by other connecting methods, and the connecting piece has an obvious benefit for improving the reliability of the connecting layer. The preparation method provided by the invention has the characteristics of low connection temperature, simple process, low cost and high strength, and has great practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon carbide ceramic connectors, and more specifically relates to a reaction-sintered silicon carbide ceramic connector and a preparation method thereof. Background Art

[0002] Reaction-sintered silicon carbide ceramics are made by pressing fine-grained α-SiC and additives into a green blank, which is then exposed to liquid silicon at high temperature. The carbon in the blank reacts with the infiltrated Si to generate β-SiC, which combines with α-SiC, and the free silicon fills the pores, thus obtaining a highly dense ceramic material. Reaction-sintered silicon carbide has the advantages of low sintering temperature, short sintering time, and near-net shape preparation. Reaction-sintered silicon carbide can not only maintain the excellent mechanical properties of silicon carbide ceramics such as high strength, high hardness, and wear resistance, but also has thermal properties such as thermal shock resistance, high thermal conductivity, low expansion coefficient, and high electrical conductivity. It is an important ceramic material in modern industry.

[0003] With the widespread application of silicon carbide ceramics, some special application environments have put forward requirements on the size and shape of ceramic materials. However, due to the limitations of ceramic forming methods and preparation equipment, large-sized and complex-shaped silicon carbide ceramic parts can only be prepared by connection technology. At present, the main methods used for connecting silicon carbide ceramic materials are brazing, diffusion welding and reaction connection. The main disadvantage of brazing ceramics is that stress is generated in the joint due to the mismatch of thermal expansion coefficients of dissimilar materials. Diffusion welding connection technology has the disadvantages of high connection pressure, the composition and properties of the intermediate layer material cannot match the parent material, and it is difficult to apply to the welding of large-sized components. Therefore, the composition and properties of the connection layer materials of brazing and diffusion welding cannot match the parent material, and the uniformity of the organization is poor.

[0004] The ceramic connection layer is used to connect ceramic materials. Since its physical properties are closest to those of the parent material and the interface residual stress is the lowest, the joint performance is better. In the connection technology of silicon carbide ceramics, the ceramic connection layer is mainly constructed by reaction connection technology. The components of the connection layer include added silicon carbide particles, newly formed silicon carbide, residual silicon, etc. Due to the use of melt infiltration technology, the distribution of residual silicon is uneven and the performance of the connection layer is not ideal. Chinese invention patent CN 111187092A discloses a method for connecting silicon carbide ceramic parts. The method is to apply a suspension slurry (solvent, organic precursor, catalyst, silicon carbide powder and carbon black powder) to the gap between two silicon carbide ceramic parts to be connected, pressurize and dry, and then crack the parts to be connected at a high temperature of 1100-1350°C (holding time is 2-4 hours), and finally siliconize the parts to be connected at a temperature of 1500-1650°C (holding time is 0.5-2 hours), thereby realizing the connection between silicon carbide ceramic parts. However, the preparation process of ceramic slurry is relatively complicated. At the same time, since the ceramic slurry needs to be subjected to high-temperature siliconization treatment after solidification and high-temperature cracking, the process flow is long and the cost is high. Chinese invention patent CN112851388A discloses a silicon carbide ceramic connection method, which is to mix a mixed powder of SiC nanopowder and a liquid phase sintering aid with an organic solvent to obtain a connecting brazing material, and evenly apply it between silicon carbide parent materials to perform high-temperature connection at 1500-1700°C (heat preservation time is 0.5-2 hours) to obtain a preliminary connecting piece; then the precursor slurry is applied or immersed in the connection area of ​​the preliminary connecting piece, solidified at 100-300°C in an Ar or vacuum atmosphere (heat preservation time is 0.5-2 hours), and then cracked at 1000-1500°C (heat preservation time is 0.5-2 hours), and the silicon carbide ceramic connecting piece is obtained after the precursor impregnation cracking process is cycled 1-5 times. However, the preparation process of ceramic slurry is relatively complicated. At the same time, after the ceramic is connected at high temperature, it needs to go through steps such as circulating coating slurry curing and high-temperature cracking. The process flow is long, which will undoubtedly increase the manufacturing cost.

[0005] From the above analysis, it can be seen that in the existing silicon carbide ceramic connection technology, due to the huge physical property difference between the ceramic base material and the metal brazing material (or metal diffusion intermediate layer) in the metal connection layer, there is a large residual stress in the weld area and the reliability of the joint is reduced; while the connection temperature of silicon carbide ceramics connected by a ceramic connection layer is high, the slurry preparation and connection process is long, and the cost is high.

[0006] Therefore, how to provide a reaction-sintered silicon carbide ceramic connector and a preparation method thereof is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0007] In order to overcome the shortcomings and deficiencies in the prior art, the present invention provides a reaction-sintered silicon carbide ceramic connecting piece and a preparation method thereof. In view of the characteristics of free silicon and a small amount of micropores in reaction-sintered silicon carbide ceramics, a melt infiltration process is used to match the material composition and properties of the ceramic connecting layer with those of the parent material, thereby achieving high-strength connection of silicon carbide ceramics. In addition, the melt infiltration connection has a low temperature, a simple process and low cost.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing a reaction-sintered silicon carbide ceramic connector comprises the following steps:

[0010] (1) polishing the surface of the reaction-sintered silicon carbide ceramic to be welded, ultrasonically cleaning it with acetone, and drying it to obtain a reaction-sintered silicon carbide ceramic base material;

[0011] (2) adding SiC powder to the phenolic resin solution and mixing to obtain silicon carbide slurry;

[0012] (3) The silicon carbide slurry obtained in step (2) is coated on the surface of the reaction-sintered silicon carbide ceramic base material to be welded, at least two reaction-sintered silicon carbide ceramic base materials are assembled through the surface to be welded, and then phenolic resin is cracked and silicon-titanium alloy is infiltrated to form a connecting layer to obtain a connecting part.

[0013] Preferably, the polishing requirement in step (1) is that the surface roughness Ra≤20 μm.

[0014] Preferably, the mass ratio of the SiC powder to the phenolic resin solution in step (2) is 6-8:2-4.

[0015] Preferably, the residual carbon content of the phenolic resin solution in step (2) is 20 to 30 wt%.

[0016] Preferably, the content of SiC powder in the silicon carbide slurry in step (2) is 60-80wt%, and the average particle size of the SiC powder is 10-30μm.

[0017] Preferably, the mixing in step (2) is performed by centrifugal stirring, using a solder paste mixer for stirring, with a rotation speed of 400 to 600 r / min and a stirring time of 10 to 15 min.

[0018] Preferably, the coating in step (3) is performed by tape casting, and the coating thickness of the silicon carbide slurry is 100 to 200 μm.

[0019] Preferably, the silicon content in the silicon-titanium alloy in step (3) is 70-85wt%.

[0020] Preferably, the pyrolysis atmosphere in step (3) is vacuum, the pyrolysis temperature is 700-1000° C., and the insulation time is 10-60 min.

[0021] Preferably, the infiltration atmosphere in step (3) is vacuum, the temperature is 1330-1400° C., and the insulation time is 10-30 min.

[0022] The present invention also provides a reaction-sintered silicon carbide ceramic connector prepared according to the above preparation method.

[0023] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a system and method for preparing a suture with a developing function, which has the following beneficial effects:

[0024] (1) The material system of the connection layer constructed by the present invention is silicon carbide + newly generated silicon carbide + residual silicon titanium, wherein the total silicon carbide content reaches more than 80 vol%. Such a connection layer composition is close to the reaction sintered base material silicon carbide, and its thermal expansion coefficient and elastic modulus match, so the interface residual stress will be significantly smaller than the connection layer prepared by other connection methods, which has obvious benefits for improving the reliability of the connection layer. It is mainly reflected in the following aspects: 1) Compared with the traditional brazing method, this method is a homogeneous connection with less stress concentration; 2) Compared with the reaction connection method, the phenolic resin is converted into carbon by high-temperature pyrolysis and then the SiC particles are bonded together in the form of ceramic bonding, thereby obtaining a microporous connection layer, which is helpful for subsequent infiltration connection, without the need to add additional carbon or other organic precursors, and the connection layer strength is higher; 3) Compared with the diffusion welding method, the connection process does not require the application of pressure, which is suitable for the connection of large-sized and complex-shaped components.

[0025] (2) With phenolic resin solution as the source of carbon, during the infiltration process, carbon reacts with silicon in the silicon-titanium alloy to form silicon carbide. Therefore, the carbon content remaining in the connecting layer after cracking can be adjusted by adjusting the residual carbon content of the phenolic resin. Alternatively, the amount and distribution of silicon carbide formed by the reaction in the connecting layer after infiltration can be controlled by adjusting the silicon carbide particle size and silicon carbide powder content (mass ratio of SiC powder to phenolic resin solution) in the silicon carbide slurry, thereby improving the mechanical properties of the connecting parts.

[0026] (3) Compared with the currently common cracking (or welding) and then siliconizing connection process, the cracking and infiltration treatment processes of the present invention are carried out simultaneously, without the need for heating, cracking (welding), cooling, and then heating for siliconizing. The process is simple and the cost of raw materials used is low, which helps to improve production efficiency and reduce manufacturing costs.

[0027] (4) Compared with the currently common siliconizing connection process which requires a temperature higher than 1450°C and a holding time of 1 to 2 hours, the present invention can achieve the connection of reaction-sintered silicon carbide ceramics at a lower temperature of 1330 to 1400°C and a shorter holding time of 10 to 30 minutes.

[0028] (5) Taking advantage of the presence of free silicon and a small amount of micropores in reaction-sintered silicon carbide ceramics, a silicon-titanium alloy with excellent penetration and a melting point lower than that of silicon is used to form a liquid phase at a temperature lower than the melting point of silicon, and can quickly penetrate into the reaction-sintered silicon carbide ceramics and the connection area under the action of capillary force. The process of infiltration can not only achieve the connection of ceramics, but also improve the density and strength of reaction-sintered silicon carbide ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 This is a scanning electron microscope image of the microstructure of the reaction-sintered silicon carbide ceramic connector prepared in Example 1;

[0031] Figure 2 a and b are respectively the microstructure metallographic image and scanning electron microscope image of the reaction sintered silicon carbide ceramic connector prepared in Example 2;

[0032] Figure 3 This is a scanning electron microscope image of the microstructure of the reaction-sintered silicon carbide ceramic connector prepared in Example 3;

[0033] Figure 4 The microstructure metallographic image of the reaction-sintered silicon carbide ceramic connector prepared in Comparative Example 1;

[0034] Figure 5 This is a scanning electron microscope image of the microstructure of the reaction-sintered silicon carbide ceramic connector prepared in Comparative Example 2. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing a reaction-sintered silicon carbide ceramic connector comprises the following steps:

[0038] (1) polishing the surface to be connected of the reaction-sintered silicon carbide ceramic (the silicon content in the ceramic is 10%) to a surface roughness Ra of 15 μm, ultrasonically cleaning it with acetone, and drying it to obtain a reaction-sintered silicon carbide ceramic base material;

[0039] (2) SiC powder with an average particle size of 23 μm and a phenolic resin solution with a residual carbon content of 25 wt% were mixed in a solder paste mixer at a speed of 500 r / min for 10 min to obtain a uniformly mixed silicon carbide slurry with a SiC powder content of 60 wt%;

[0040] (3) The obtained silicon carbide slurry is evenly coated on the surface to be connected of a reaction-sintered silicon carbide ceramic base material by a tape casting method, the coating thickness of the silicon carbide slurry is 200 μm, and a certain pressure is applied by a tool to assemble it with another reaction-sintered silicon carbide ceramic base material to form a sandwich structure, and the applied pressure value is 100 Pa;

[0041] (4) Place it in a graphite mold and perform cracking and infiltration treatment in a vacuum furnace. The cracking temperature is 800°C, which is kept for 20 minutes, and then the temperature is continued to rise. The infiltration temperature of the silicon-titanium alloy 76Si-24Ti (wt%) is 1360°C, which is kept for 20 minutes, and then cooled to room temperature to obtain a reaction-sintered silicon carbide ceramic connector.

[0042] The connection layer of the connection piece is tested by scanning electron microscope, and the scanning electron microscope image is shown in Figure 1 It can be seen that the interface of the connecting layer is well connected, no obvious defects are found, and the structure of the connecting layer is similar to that of the base material.

[0043] Example 2

[0044] A method for preparing a reaction-sintered silicon carbide ceramic connector, which is different from Example 1 in that the mass ratio of SiC powder to phenolic resin solution is 7:3.

[0045] The connector was tested by metallographic microscope and scanning electron microscope, and the results are shown in Figure 2 As can be seen from the figure, the interface of the connecting layer is well connected, no obvious defects are found, and the structure of the connecting layer is similar to that of the base material.

[0046] Example 3

[0047] A method for preparing a reaction-sintered silicon carbide ceramic connector, which is different from Example 1 in that the mass ratio of SiC powder to phenolic resin solution is 8:2.

[0048] The connector was tested by scanning electron microscope, and the results are shown in Figure 3 It can be seen that the interface of the connecting layer is well connected, no obvious defects are found, and the structure of the connecting layer is similar to that of the base material.

[0049] Example 4

[0050] A method for preparing a reaction-sintered silicon carbide ceramic connector, which is different from Example 1 in that the average particle size of SiC powder is 13 μm.

[0051] Example 5

[0052] A method for preparing a reaction-sintered silicon carbide ceramic connector, which is different from Example 1 in that the silicon-titanium alloy infiltration temperature is 1380°C.

[0053] Example 6

[0054] A method for preparing a reaction-sintered silicon carbide ceramic connector, which is different from Example 1 in that the residual carbon content of the phenolic resin solution is 30wt%.

[0055] Comparative Example 1

[0056] A method for preparing a reaction-sintered silicon carbide ceramic connector comprises the following steps:

[0057] (1) polishing the surface to be connected of the reaction-sintered silicon carbide ceramic (the silicon content in the ceramic is 10%) to a surface roughness Ra ≤ 15 μm;

[0058] (2) Place the sample to be welded in a graphite mold and perform infiltration connection in a vacuum furnace. First, heat it to 800°C, keep it warm for 20 minutes, and then continue to heat it up. The infiltration temperature of silicon-titanium alloy (76Si-24Ti (wt%)) is 1360°C, keep it warm for 20 minutes, and then cool it down to room temperature to obtain a reaction-sintered silicon carbide ceramic connector.

[0059] The connector is tested by metallographic microscope, and the results are shown in Figure 4 It can be seen that the connecting layer contains only silicon and no silicon carbide.

[0060] Comparative Example 2

[0061] A method for infiltration connection of reaction-sintered silicon carbide ceramics comprises the following steps:

[0062] (1) polishing the surface to be connected of the reaction-sintered silicon carbide ceramic (the silicon content in the ceramic is 10%) to a surface roughness Ra ≤ 20 μm;

[0063] (2) mixing silicon carbide powder having an average particle size of 23 μm and a phenolic resin solution having a residual carbon content of 25 wt % at a mass ratio of 7:3 in a solder paste mixer at a rotation speed of 500 r / min for 10 min to obtain a uniformly mixed silicon carbide slurry;

[0064] (3) The obtained silicon carbide slurry is evenly coated on the surface to be connected of one of the reaction-sintered silicon carbide ceramics by tape casting, the coating thickness of the silicon carbide slurry is 200 μm, and a certain pressure is applied by a tool to assemble it with another reaction-sintered silicon carbide ceramic to form a sandwich structure, and the applied pressure value is 100 Pa;

[0065] (4) Place in a graphite mold and perform infiltration connection in a vacuum furnace, heat to 800°C, keep warm for 0 min, and continue to heat to the infiltration temperature. The infiltration temperature of silicon-titanium alloy (76Si-24Ti (wt%)) is 1360°C, keep warm for 20 min, and then cool to room temperature to obtain a reaction-sintered silicon carbide ceramic connector.

[0066] The connector was tested by scanning electron microscope, and the results are shown in Figure 5 As can be seen from the figure, if the cracking and heat preservation is not carried out at 800℃, there will be holes that are not fully infiltrated remaining in the connecting layer.

[0067] Performance Test:

[0068] In order to compare and analyze the strength of reaction-sintered silicon carbide ceramic connectors under different processes, a three-point bending strength test was carried out on the connector using a mechanical testing machine to test the room temperature bending strength of the samples. Three samples were prepared in parallel for each example for the bending test, and the bending strength was the average value of the bending strengths of the three samples. The bending strength data of the connectors obtained in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1.

[0069] Table 1 Flexural strength test results of reaction sintered silicon carbide ceramic connectors

[0070]

[0071] According to Table 1, compared with samples not coated with silicon carbide slurry or samples not insulated at the cracking temperature of phenolic resin, the example adopts coating of silicon carbide slurry and cracking insulation to greatly improve the connection strength of the connecting piece. The connecting piece breaks at the base material, indicating that the interface connection strength is higher than the strength of the base material itself.

[0072] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a reaction-sintered silicon carbide ceramic connector, characterized in that: The steps include: (1) polishing the surface of the reaction-sintered silicon carbide ceramic to be welded, ultrasonically cleaning it with acetone, and drying it to obtain a reaction-sintered silicon carbide ceramic base material; (2) adding SiC powder to the phenolic resin solution and mixing to obtain silicon carbide slurry; (3) The silicon carbide slurry obtained in step (2) is coated on the surface of the reaction-sintered silicon carbide ceramic base material to be welded, at least two reaction-sintered silicon carbide ceramic base materials are assembled through the surface to be welded, and then phenolic resin is cracked and silicon-titanium alloy is infiltrated to form a connecting layer to obtain a connecting part.

2. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The requirement for polishing in step (1) is that the surface roughness Ra≤20 μm.

3. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The mass ratio of the SiC powder to the phenolic resin solution in step (2) is 6-8:2-4.

4. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The residual carbon content of the phenolic resin solution in step (2) is 20 to 30 wt%.

5. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The content of SiC powder in the silicon carbide slurry in step (2) is 60-80wt%, and the average particle size of the SiC powder is 10-30μm.

6. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The coating in step (3) is performed by tape casting, and the coating thickness of the silicon carbide slurry is 100 to 200 μm.

7. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The silicon content in the silicon-titanium alloy in step (3) is 70-85wt%.

8. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The cracking atmosphere in step (3) is vacuum, the cracking temperature is 700-1000° C., and the insulation time is 10-60 min.

9. The method for preparing a reaction-sintered silicon carbide ceramic connector according to claim 1, characterized in that: The infiltration atmosphere in step (3) is vacuum, the temperature is 1330-1400° C., and the insulation time is 10-30 minutes.

10. A reaction-bonded silicon carbide ceramic connector prepared according to the preparation method according to any one of claims 1 to 9.

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