SiC coating graphite disc used for large-size high-axial-temperature-gradient working condition and preparation method of SiC coating graphite disc

Abstract

The invention relates to a SiC coating graphite disc used for a large-size high axial temperature gradient working condition and a preparation method thereof.The SiC coating graphite disc comprises a graphite base body and SiC coatings, a plurality of pits are formed in one side face of the graphite base body, the SiC coatings are deposited in the pits and on the side face of the graphite base body, the distance between the centers of the adjacent pits is 150-200 micrometers, the thickness of each SiC coating is 30-50 micrometers, and the thickness of each SiC coating is 30-50 micrometers. The grain size of the SiC coating ranges from 100 micrometers to 130 micrometers. The preparation method comprises the following steps: S1, processing one side surface of a graphite substrate to form a plurality of pits; and S2, depositing on the pits and the side surface of the graphite substrate through chemical vapor deposition. According to the invention, large crystal grains (dozens of microns) are formed in the pits, and then through vapor phase epitaxial growth, the crystal grains transversely grow until the crystal grains are completely combined, and finally ultra-large crystal grains with the size of 100-130 microns are formed; and after the transverse combination, the crystal grains continuously and vertically grow to 30-50 [mu] m to obtain the SiC coating.

Description

Technical Field

[0001] This invention relates to the field of graphite disk technology, and in particular to a SiC-coated graphite disk for large-size applications with high axial temperature gradients and its preparation method. Background Technology

[0002] In high-temperature industrial applications, isostatically pressed graphite disks are often used as core load-bearing or reaction components due to their excellent high-temperature resistance, thermal conductivity, and structural stability. To further improve their oxidation resistance, corrosion resistance, and surface strength, the industry commonly adopts a technique of preparing a SiC coating on the surface of the graphite disk. However, under special operating conditions with large-size graphite disks (especially those with large axial dimensions) and axial temperature gradients exceeding 200°C, existing SiC-coated graphite disks suffer from severe lifespan limitations. This is because: isostatic graphite and SiC coating have inherently different coefficients of thermal expansion (CTE), and their thermal deformation during heating and cooling is mismatched, inevitably leading to thermal stress at the interface; the large axial temperature gradient further amplifies this thermal mismatch effect, causing not only a sharp increase in interface stress, but also a significant increase in additional stress within the SiC coating due to the axial temperature gradient. Ultimately, this leads to through-cracks or propagating cracks in the SiC coating along the axial direction. After coating failure, the graphite disk is directly exposed to the harsh environment, resulting in a significantly shortened service life and severely impacting equipment operational stability and production efficiency. In existing technologies, solutions to thermal mismatch problems often include coating composition modification and interface transition layer design. However, these solutions are not adaptable to scenarios involving large size and large axial temperature gradient, and cannot effectively address the core problem of axial cracking in coatings. More targeted technological breakthroughs are urgently needed. Summary of the Invention

[0003] To achieve the above objectives, the present invention adopts the following technical solution: A SiC-coated graphite disk for large-size applications with high axial temperature gradients includes a graphite substrate with multiple pits formed on one side, and a SiC coating deposited in the pits and on the same side of the graphite substrate. The spacing between the centers of adjacent pits is 150-200 μm, the thickness of the SiC coating is 30-50 μm, and the grain size of the SiC coating is 100-130 μm.

[0004] Preferably, the pits have a diameter of 30-50 μm and a depth of 5-15 μm. This size range of micropits maximizes the mechanical interlocking effect while ensuring that the slurry or reactive gas can be fully filled to form a robust SiC seed layer.

[0005] Preferably, the pits are hexagonal, the spacing between adjacent pits is 80-120 μm, and the grain size of the SiC coating is 100 μm. Using a hexagonal array with a spacing of 80-120 μm provides the most uniform and stable support for the 30-50 μm thick deposition layer, resulting in optimal thermal stress distribution and the most balanced and reliable crack resistance of the entire coating system.

[0006] A method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients includes the following steps: S1. Multiple pits are formed on one side of a graphite substrate, and the spacing between adjacent pits is 80-150μm; S3: A SiC coating with a thickness of 30-50 μm is formed by chemical vapor deposition in the pit and on the side of the graphite substrate, and the grain size of the SiC coating is 100-130 μm.

[0007] Preferably, step S1 includes: A photoresist mask is formed on a graphite substrate using photolithography. Place the dried graphite substrate into an ion etching apparatus and introduce 30-50 sccm of O2 and 10-20 sccm of Ar. Under conditions of 5-10 Pa pressure, 150-200 W RF power and 50-80 W bias power, perform plasma etching on the substrate for 15-25 min. Finally, the photoresist mask is removed to form a graphite substrate with pits.

[0008] By utilizing photolithography, high-precision and high-consistency transfer of micron-level patterns is achieved, ensuring precise control over the size and position of the pit array.

[0009] Preferably, step S1 further includes: polishing the graphite substrate before the photolithography process, then cleaning it sequentially with acetone, ethanol, and deionized water for 10-20 minutes each, and then drying it at 60-80°C for 1-2 hours. Preferably, the polishing is performed until Ra ≤ 0.03 μm. Preferably, step S2 includes: introducing hydrogen and methyltrichlorosilane in a molar ratio of (9-11):1, C / Si molar ratio of (1.2-1.5):1, maintaining the pressure at 100-500 Torr, heating to 1400-1600℃ at 4-6℃ / min, a deposition rate of 1-2 μm / h, and a deposition time of 15-50h.

[0010] Preferably, after deposition, the temperature is lowered to 1100-1200℃ at a rate of 1-3℃ / min and held for 1-3 hours; then it is lowered to room temperature at a rate of 4-6℃ / min.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention forms pits in a graphite substrate. Since the pits contain high-energy nucleation sites, one or more SiC nuclei will preferentially form inside the pits during the initial stage of chemical vapor deposition, making each pit a "grain growth unit" and achieving "low-density controllable nucleation". Then, through high-temperature deposition, the grains grow laterally and diffuse until they completely merge, eventually forming ultra-large grains with a size of 100-130 μm. After lateral merging, the grains continue to grow vertically to a SiC coating with a size of 30-50 μm.

[0012] The SiC-coated graphite disk of this invention reduces the total stress within the SiC coating and at the coating-graphite interface by 60%-70%. Under temperature gradient conditions above 200°C, the axial cracking rate of the SiC coating is reduced from over 80% in the prior art to below 10%, completely solving the core failure problem. The effective service life of the graphite disk is extended from the original 1-3 months to 6-12 months, and the equipment maintenance cost is reduced by more than 50%. Detailed Implementation

[0013] The present invention will now be described in more detail. It should be noted that the description of the present invention is illustrative only and not restrictive. Various embodiments can be combined with each other to form other embodiments not shown in the following description.

[0014] Example 1

[0015] The method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients provided in this embodiment includes the following steps: S1. Select a high-purity isostatic graphite disk as the graphite substrate, and form a photoresist mask on the graphite substrate through photolithography. Place it in an ion etching device, introduce 30 sccm of O2 and 10 sccm of Ar, and perform plasma etching on the dried graphite substrate under the conditions of pressure 5 Pa, RF power 150 W, and bias power 50 W for 15 min. Finally, remove the photoresist mask to form a graphite substrate with pits, the pit diameter is 30 μm, the pit depth is 5 μm, and the center distance (spacing) is 150 μm.

[0016] Step S2: Introduce 1500 sccm of hydrogen, 500 sccm of argon, and 150 sccm of MTS, maintain the pressure at 8 kPa, and heat to 1250℃ at 5℃ / min. Deposit for 2 hours to obtain a continuous SiC coating with a total thickness of about 35 μm and a grain size of about 105 μm.

[0017] The interfacial stress and axial cracking rate of the prepared product were tested, and the results showed that... The maximum axial tensile stress inside the SiC coating is 83 MPa, while the maximum axial tensile stress inside the traditional SiC coating is about 300-350 MPa. Under temperature gradient conditions above 200°C, the axial cracking rate of the SiC coating is 11%, while that of the traditional technology is over 80%.

[0018] Example 2

[0019] The method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients provided in this embodiment includes the following steps: S1. Select a high-purity isostatic graphite disk as the graphite substrate, and form a photoresist mask on the graphite substrate through photolithography. Place it in an ion etching device, introduce 50 sccm of O2 and 20 sccm of Ar, and perform plasma etching on the dried graphite substrate under the conditions of 10 Pa pressure, 200 W RF power and 80 W bias power for 25 min. Finally, remove the photoresist mask to form a graphite substrate with pits, with a pit diameter of 50 μm, a pit depth of 15 μm and a center distance (spacing) of 200 μm.

[0020] Step S2: Introduce 1500 sccm of hydrogen, 500 sccm of argon, and 150 sccm of MTS, maintain the pressure at 8 kPa, and heat to 1250℃ at 5℃ / min. Deposit for 2 hours to obtain a continuous SiC coating with a total thickness of about 35 μm and a grain size of about 131 μm.

[0021] The interfacial stress and axial cracking rate of the prepared product were tested, and the results showed that... The maximum axial tensile stress inside the SiC coating is 85 MPa, while the maximum axial tensile stress inside the traditional SiC coating is about 300-350 MPa. Under temperature gradient conditions above 200°C, the axial cracking rate of the SiC coating is 10%, while that of the traditional technology is over 80%.

[0022] Example 3

[0023] The method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients provided in this embodiment includes the following steps: S1. A high-purity isostatic graphite disk was selected as the graphite substrate. The disk was polished on one side to Ra ≈ 0.03 μm, and then cleaned sequentially with acetone, ethanol, and deionized water for 10 min each. The substrate was then dried at 60°C for 1 h. A photoresist mask was formed on the graphite substrate using photolithography. The substrate was placed in an ion etching apparatus, and O2 at 50 sccm and Ar at 20 sccm were introduced. Plasma etching was performed on the dried graphite substrate under the conditions of 10 Pa pressure, 200 W RF power, and 80 W bias power for 25 min. Finally, the photoresist mask was removed to form a graphite substrate with pits. The pit diameter was 50 μm, the pit depth was 15 μm, and the center distance (spacing) was 180 μm.

[0024] Step S2: Introduce 1500 sccm of hydrogen, 500 sccm of argon, and 150 sccm of MTS, maintain the pressure at 8 kPa, increase the temperature to 1250℃ at 5℃ / min, and deposit for 3 hours to obtain a continuous SiC coating with a total thickness of about 50 μm and a grain size of about 118 μm.

[0025] The interfacial stress and axial cracking rate of the prepared product were tested, and the results showed that... The maximum axial tensile stress inside the SiC coating is 81 MPa, while the maximum axial tensile stress inside the traditional SiC coating is about 300-350 MPa. Under temperature gradient conditions above 200°C, the axial cracking rate of the SiC coating is 9%, while that of the traditional technology is over 80%.

[0026] Example 4

[0027] The method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients provided in this embodiment includes the following steps: S1. A high-purity isostatic graphite disk was selected as the graphite substrate. The disk was polished on one side to Ra ≈ 0.01 μm, then sequentially cleaned with acetone, ethanol, and deionized water for 210 min each, and dried at 80℃ for 2 h. A photoresist mask was formed on the graphite substrate using photolithography. The substrate was then placed in an ion etching apparatus, and 50 sccm of O2 and 20 sccm of Ar were introduced. Under conditions of 10 Pa pressure, 200 W RF power, and 80 W bias power, plasma etching was performed on the dried graphite substrate for 25 min. Finally, the photoresist mask was removed to form a graphite substrate with pits. The pit diameter was 50 μm, the pit depth was 15 μm, and the center-to-center distance (spacing) was 180 μm.

[0028] Step S2: Introduce 2000 sccm of hydrogen, 1000 sccm of argon, and 200 sccm of MTS, maintain the pressure at 10 kPa, and heat to 1250℃ at 5℃ / min. Deposit for 3 hours to obtain a continuous SiC coating with a total thickness of about 50 μm and a grain size of about 120 μm.

[0029] The interfacial stress and axial cracking rate of the prepared product were tested, and the results showed that... The maximum axial tensile stress inside the SiC coating is 84 MPa, while the maximum axial tensile stress inside the traditional SiC coating is about 300-350 MPa. Under temperature gradient conditions above 200°C, the axial cracking rate of the SiC coating is 10%, while that of the traditional technology is over 80%.

[0030] Example 5

[0031] The method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients provided in this embodiment includes the following steps: S1. A high-purity isostatic graphite disk was selected as the graphite substrate. The disk was polished on one side to Ra ≈ 0.01 μm, then sequentially cleaned with acetone, ethanol, and deionized water for 210 min each, and dried at 80℃ for 2 h. A photoresist mask was formed on the graphite substrate using photolithography. The substrate was placed in an ion etching apparatus, and 50 sccm of O2 and 20 sccm of Ar were introduced. Under conditions of 10 Pa pressure, 200 W RF power, and 80 W bias power, plasma etching was performed on the dried graphite substrate for 25 min. Finally, the photoresist mask was removed to form a graphite substrate with pits. The pit diameter was 50 μm, the pit depth was 15 μm, and the center-to-center distance (spacing) was 170 μm.

[0032] Step S2: Introduce 2000 sccm of hydrogen, 1000 sccm of argon, and 200 sccm of MTS, maintain the pressure at 10 kPa, increase the temperature to 1250℃ at 5℃ / min, and deposit for 3 hours to obtain a continuous SiC coating with a total thickness of about 50 μm and a grain size of about 109 μm.

[0033] The interfacial stress and axial cracking rate of the prepared product were tested, and the results showed that... The maximum axial tensile stress inside the SiC coating is 80 MPa, while the maximum axial tensile stress inside the traditional SiC coating is about 300-350 MPa. Under temperature gradient conditions above 200°C, the axial cracking rate of the SiC coating is 8%, while that of the traditional technology is over 80%.

[0034] Example 6

[0035] The method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients provided in this embodiment includes the following steps: S1. A high-purity isostatic graphite disk was selected as the graphite substrate. The disk was polished on one side to Ra ≈ 0.01 μm, then sequentially cleaned with acetone, ethanol, and deionized water for 210 min each, and dried at 80℃ for 2 h. A photoresist mask was formed on the graphite substrate using photolithography. The substrate was placed in an ion etching apparatus, and 50 sccm of O2 and 20 sccm of Ar were introduced. Under conditions of 10 Pa pressure, 200 W RF power, and 80 W bias power, plasma etching was performed on the dried graphite substrate for 25 min. Finally, the photoresist mask was removed to form a graphite substrate with pits. The pit diameter was 50 μm, the pit depth was 15 μm, and the center-to-center distance (spacing) was 170 μm.

[0036] Step S3: Introduce 2000 sccm of hydrogen, 1000 sccm of argon, and 200 sccm of MTS, maintain the pressure at 10 kPa, increase the temperature to 1250℃ at 5℃ / min, and deposit for 3 hours to obtain a continuous SiC coating with a total thickness of about 50 μm and a grain size of about 110 μm.

[0037] The interfacial stress and axial cracking rate of the prepared product were tested, and the results showed that... The maximum axial tensile stress inside the SiC coating is 87 MPa, while the maximum axial tensile stress inside the traditional SiC coating is about 300-350 MPa. Under temperature gradient conditions above 200°C, the axial cracking rate of the SiC coating is 11%, while that of the traditional technology is over 80%.

[0038] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A SiC-coated graphite disk for large-size applications with high axial temperature gradients, characterized in that, The invention comprises a graphite substrate having multiple pits on one side, and a SiC coating deposited in the pits and on the same side of the graphite substrate, wherein the spacing between the centers of adjacent pits is 150-200 μm, the thickness of the SiC coating is 30-50 μm, and the grain size of the SiC coating is 100-130 μm.

2. The SiC-coated graphite disk for large-size applications with high axial temperature gradients according to claim 1, characterized in that, The pit has a diameter of 30-50 μm and a depth of 5-15 μm.

3. The SiC-coated graphite disk for large-size applications with high axial temperature gradients according to claim 1, characterized in that, The pits are hexagonal, the spacing between adjacent pits is 80-120 μm, and the grain size of the SiC coating is 100 μm.

4. A method for preparing a SiC-coated graphite disk for large-size applications with high axial temperature gradients, characterized in that, Includes the following steps: S1. Multiple pits are formed on one side of a graphite substrate, and the spacing between adjacent pits is 80-150μm; S2. A SiC coating with a thickness of 30-50 μm is formed by chemical vapor deposition in the pit and on the side of the graphite substrate, and the grain size of the SiC coating is 100-130 μm.

5. The method for preparing SiC-coated graphite disks for large-size applications with high axial temperature gradients according to claim 4, characterized in that, Step S1 includes: A photoresist mask is formed on a graphite substrate using photolithography. Place the dried graphite substrate into an ion etching apparatus and introduce 30-50 sccm of O2 and 10-20 sccm of Ar. Under conditions of 5-10 Pa pressure, 150-200 W RF power and 50-80 W bias power, perform plasma etching on the substrate for 15-25 min. Finally, the photoresist mask is removed to form a graphite substrate with pits.

6. The method for preparing SiC-coated graphite disks for large-size applications with high axial temperature gradients according to claim 5, characterized in that, Step S1 also includes: polishing the graphite substrate before the photolithography process, then cleaning it sequentially with acetone, ethanol and deionized water for 10-20 minutes each, and then drying it at 60-80℃ for 1-2 hours.

7. The method for preparing SiC-coated graphite disks for large-size applications with high axial temperature gradients according to claim 4, characterized in that, Step S2 includes: introducing hydrogen and methyltrichlorosilane in a molar ratio of (9-11):1, C / Si molar ratio of (1.2-1.5):1, maintaining the pressure at 100-500 Torr, heating to 1400-1600℃ at 4-6℃ / min, deposition rate of 1-2 μm / h, and deposition time of 15-50h.

8. The method for preparing SiC-coated graphite disks for large-size applications with high axial temperature gradients according to claim 7, characterized in that, After deposition, the temperature is lowered to 1100-1200℃ at a rate of 1-3℃ / min and held for 1-3 hours; then cooled to room temperature at a rate of 4-6℃ / min.