Method of repairing high purity silicon carbide parts

Abstract

The application relates to the field of silicon carbide repair, and particularly discloses a repair method for a high-purity silicon carbide piece. The repair method comprises the following steps: placing a piece to be repaired in a chamber, applying a heat source to the bottom of the piece to be repaired after the air pressure in the chamber is stabilized, and applying two gas flows of carrier gas to the top of the piece to be repaired to form a gradient temperature field in the deposition direction of the piece to be repaired; wherein the gas flows of carrier gas comprise a sweeping gas flow of carrier gas parallel to the surface direction of the piece to be repaired and a reactant gas flow of carrier gas perpendicular to the surface direction of the piece to be repaired; after the gradient temperature field is stabilized, a silicon / carbon source reaction gas is added to the reactant gas flow of carrier gas to deposit silicon carbide, and the temperature of the gas flow of carrier gas is gradually increased, the piece to be repaired is taken out after deposition is completed, heat treatment and surface polishing are performed, and a silicon carbide piece is obtained after heat treatment. The method can reduce the sharp hollow phenomenon when filling sharp depressions / cracks, and can reduce the excess deposition on the surface of the piece after repair.

Description

Technical Field

[0001] This application relates to the field of silicon carbide parts, and more specifically, it relates to a method for repairing high-purity silicon carbide parts. Background Technology

[0002] Silicon carbide and its high-purity components possess superior properties due to the strong covalent bonds of the Si-C bond, including high hardness, high strength, high temperature resistance, and corrosion resistance, along with suitable electrical characteristics. These advantages enable high-purity silicon carbide components to operate in special environments such as high radiation, high temperature, and high corrosion, and they are in high demand and widely used in high-value-added industries such as chip etching, aerospace, and nuclear industry. However, after prolonged use in specific environments, such as prolonged plasma impact in corrosive environments, prolonged oxygen ion erosion in high-temperature environments, prolonged fixed-area bombardment by high-energy neutrons in high-temperature environments, and high-frequency physical impacts in special environments, high-purity silicon carbide components may exhibit structural failure behaviors such as dispersed banded cracks and pitted defects on their surface. Therefore, repairing high-purity silicon carbide components has become an important process for extending component life and reducing production costs.

[0003] Currently, there are two main methods for repairing silicon carbide parts:

[0004] Method 1: For parts with low purity requirements, coating repair technology is the main method. This technology mainly uses ceramic precursors coated with nano-silicon carbide powder as the raw material for the repair agent. The ceramic precursors are decomposed at high temperature to generate silicon carbide nitride and silicon carbide. The filler composed of silicon carbide powder and other powders is used to achieve the coating repair effect. This method has the following disadvantages: (1) In the nano-powder filler in the raw material of this repair coating, the mass percentage of non-silicon carbide nano-powders is 10%-40%, which does not meet the requirements of high-purity silicon carbide parts; (2) The raw material of this repair coating includes non-oxide ceramic precursors with a mass percentage of 20%-50%, such as polycarbosilane, polysilazane and other polymers, which can be decomposed at high temperature into silicon carbide, silicon carbide nitride and other ceramics. However, the ceramic precursor decomposition process inevitably has a linear shrinkage rate of more than 30%, which leads to various hidden cracks in the parts, which does not meet the requirements of high hardness and high density of high-purity silicon carbide parts. (3) Regarding the repair coating and its application, a large amount of ceramic powder is contained in the pyrolysis-cured coating. There is no sintering neck between the powder particles. The powder is fixed only by the pyrolysis-cured coating, which makes the repaired parts prone to powder shedding and release during operation, which greatly affects the working environment in clean / special chambers.

[0005] Method 2: For parts with large defect areas or scattered defect locations, chemical vapor deposition of silicon carbide is used to repair the depressions. The disadvantages are as follows: (1) The existing chemical vapor deposition silicon carbide technology used in this method is characterized by uniform growth at the same rate in each area, which leads to excessive deposition in undamaged areas (e.g. Figure 1 (1) In the middle, a lot of (physical / chemical) grinding and leveling is required to ensure the surface of the part is flat. However, the ultra-high hardness and corrosion resistance of silicon carbide make grinding and leveling of large thickness (usually about 2-3 mm) very difficult and very slow. At present, the grinding rate is about 5-20 μm / h, and grinding a thickness of 2-3 mm usually requires 100-600 hours of grinding time. (2) When this scheme is faced with repairing the depression / crack at the bottom tip, silicon carbide molecules often form islands on both sides of the crack wall, expand and gradually merge as the deposition progresses, causing the tip to form a hollow (such as Figure 1 (2) In some cases, the repair area deposited by this scheme often has varying degrees of internal stress and a small number of defect concentrations, resulting in low strength of the repaired part.

[0006] Therefore, there is an urgent need to develop a repair method for high-purity silicon carbide parts that can not only reduce the amount of grinding work, but also overcome the phenomenon of hollow spots at the tips. Summary of the Invention

[0007] To address the issues of tip hollowing and excessively thick excess deposits that easily occur during the repair process of high-purity silicon carbide, this application provides a repair method for high-purity silicon carbide parts.

[0008] This application provides the following technical solution:

[0009] A method for repairing high-purity silicon carbide parts, comprising:

[0010] The part to be repaired is placed in the chamber, and after evacuation, carrier gas is continuously introduced.

[0011] After the air pressure in the chamber stabilizes, a heat source is applied to the bottom of the workpiece to be repaired, and two carrier gas streams are applied to the top of the workpiece to be repaired to form a gradient temperature field in the deposition direction of the workpiece to be repaired; wherein, the carrier gas streams include a purge carrier gas stream parallel to the surface of the workpiece to be repaired and a reactant carrier gas stream perpendicular to the surface of the workpiece to be repaired. The temperature of the heat source is T1, and the temperature of the carrier gas streams is T2, and they satisfy: T1-T2=200~700℃;

[0012] After the gradient temperature field stabilizes, silicon / carbon source reaction gas is added to the reactant carrier gas flow to carry out silicon carbide deposition, and the temperature of the carrier gas flow is gradually increased. When the deposition is completed, the temperature of the carrier gas flow is T3, and it satisfies T1-T3=0~400℃, thus obtaining the initial product of the repair part.

[0013] The initial repair part is heat-treated and surface-polished to obtain a silicon carbide part.

[0014] Furthermore, the heat source temperature T1 applied to the bottom of the part to be repaired is 1200-1300℃.

[0015] Furthermore, the flow rate ratio of the purge carrier gas to the reactant carrier gas is 5-8:2-5.

[0016] Furthermore, during the formation of the gradient temperature field and the silicon carbide deposition process, the chamber is in a stable low-pressure state of 1000–3000 Pa; when the temperature of the carrier gas flow gradually increases from T2 to T3 during the silicon carbide deposition process, the gas pressure in the chamber gradually decreases to 500–1500 Pa.

[0017] Furthermore, the initial heat treatment of the repaired parts is a three-stage heat treatment process, including:

[0018] First, heat the furnace body to 1600-1700℃ and hold it at that temperature for 0.5-1.5 hours.

[0019] The furnace body is then heated to 1750-1850℃ and held for 1.5-2.5 hours, during which the initial repair parts are vibrated and repaired.

[0020] Finally, the furnace body is cooled to 1600-1700℃ and then cooled along with the furnace.

[0021] Furthermore, in the above three-stage heat treatment process, the heating rate of the first stage is 1-12℃ / min, the heating rate of the second stage is 1-3℃ / min, and the cooling rate of the third stage is 1-3℃ / min.

[0022] Furthermore, the aforementioned silicon / carbon source reactant gas includes both carbon source and silicon source materials, with the silicon source materials including CH3SiCl3 and C7H. 20 At least one of Si2, SiH4, SiH3Cl, SiH2Cl2, SiHCl3, and SiCl4; the carbon source includes CH3SiCl3 and C7H 20 At least one of Si2 and C1-C4 alkanes.

[0023] Furthermore, when silicon / carbon source reactant gas is added to the reactant carrier gas stream for silicon carbide deposition, the volume ratio of carrier gas to silicon / carbon source reactant gas in the reactant carrier gas stream is 3 to 20:1.

[0024] Furthermore, the carrier gas is hydrogen and argon in a volume ratio of 1:1 to 3.

[0025] Furthermore, before placing the part to be repaired into the chamber, a dust-free cleaning process is also included on the surface of the part to be repaired.

[0026] In summary, this application has the following beneficial effects:

[0027] The high-purity silicon carbide part repair process proposed in this application creates a temperature field with a gradient temperature range along the thickness of the silicon carbide part by adjusting the action of the bottom heat source and the carrier gas flow. That is, the temperature is highest at the bottom of the silicon carbide part and gradually decreases from the bottom to the top. Temperature affects the chemical vapor deposition rate. The higher the temperature, the faster the silicon carbide deposition rate. This allows silicon carbide to be preferentially deposited at the deepest part of the defect (the area with the highest temperature in the defect) during the deposition process, and reduces the phenomenon of tip voids when filling sharp depressions / cracks. At the same time, as the deposition proceeds, the carrier gas temperature is gradually increased and the gas pressure in the chamber is decreased, which greatly reduces the excess deposition on the surface of the repaired part and avoids the need for long-term grinding of the part afterward. This shortens the subsequent machining time and greatly improves the yield. Furthermore, the silicon carbide part obtained after heat treatment largely restores the original mechanical properties of the part. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the repair process of Scheme 2 in the prior art;

[0029] Figure 2 A schematic diagram illustrating the principle of the high-purity silicon carbide repair process provided in this application;

[0030] Figure 3 This is a flowchart of the high-purity silicon carbide repair process provided in Embodiment 1 of this application;

[0031] Figure 4 This is a photograph of the damaged portion of the high-purity silicon carbide part in Embodiment 1 of this application;

[0032] Figure 5 This is a photograph of the repaired defective part of the high-purity silicon carbide component in Example 1 of this application. Detailed Implementation

[0033] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0034] The technical solution of this invention is as follows:

[0035] A repair method for high-purity silicon carbide parts, the schematic diagram of which is shown below. Figure 2 As shown, it includes the following steps:

[0036] Step S1: Place the part to be repaired in the chamber, evacuate the vacuum, and then continuously introduce carrier gas.

[0037] Furthermore, after the carrier gas is introduced, the gas pressure in the chamber is maintained at 1000-3000 Pa (preferably 1500-2500 Pa). This parameter range is beneficial for the reaction to proceed and for the exhaust gas to be discharged.

[0038] Furthermore, the carrier gas is hydrogen and argon in a volume ratio of 1:1 to 3; preferably, the volume ratio of argon to hydrogen is 2:1.

[0039] Furthermore, before placing the part to be repaired into the chamber, the process includes a dust-free cleaning step on the surface of the part to be repaired. Specifically, this includes dissolving surface contaminants, organic matter, and metal ion contaminants with liquid chemical solvents, and performing dust-free cleaning on the surface of the part to be repaired using methods such as ultrasonic waves, multiple rinsing, and drying.

[0040] Step S2: After the gas pressure in the chamber stabilizes, a heat source is applied to the bottom of the part to be repaired, and two carrier gas streams are applied to the top of the part to be repaired to form a gradient temperature field in the deposition direction of the part to be repaired. The carrier gas streams include a purge carrier gas stream without reactants parallel to the surface of the part to be repaired, and a reactant carrier gas stream perpendicular to the surface of the part to be repaired. The volume ratio of carrier gas to reactant gas is calculated after the two are mixed evenly in the chamber. The temperature of the heat source is T1, and the temperature of the carrier gas streams is T2, and they satisfy: T1-T2=200~700℃.

[0041] In this step, the bottom heat source temperature applied to the part to be repaired is high (e.g., 1300°C), while the temperature of the two carrier gas streams applied to the top of the part to be repaired is relatively low (e.g., 900°C), and the airflow directions of the two carrier gas streams are perpendicular to each other. This controls the chamber temperature to be slightly higher than the carrier gas temperature and lower than the bottom heat source temperature, so that a stable gradient temperature field with a lower bottom and a higher top is formed in the thickness direction (deposition direction) of the part to be repaired.

[0042] Furthermore, the heat source temperature T1 applied to the bottom of the part to be repaired is 1200–1300°C, preferably 1230–1260°C; the carrier gas flow temperature T2 is 700–1000°C, preferably 800–900°C. In order to form a stable gradient temperature field that can achieve the deposition target, it is necessary to satisfy: T1-T2 = 200–700°C, preferably 300–500°C.

[0043] Furthermore, the flow rate ratio of the purge carrier gas to the reactant carrier gas is 5–8:2–5, preferably 6–7:3–4. The advantage of a lower flow rate of the reactant carrier gas in the vertical direction is that it maintains the surface-temperature gas flow as an upward-flowing stream with a certain velocity, thereby reducing excess deposition. Furthermore, during the formation of the gradient temperature field and the silicon carbide deposition process, the chamber maintains a stable low-pressure state of 1000–3000 Pa (preferably 1500–2500 Pa).

[0044] Step S3: After the gradient temperature field stabilizes, silicon / carbon source reaction gas is added to the carrier gas flow to deposit silicon carbide, and the temperature of the carrier gas flow is gradually increased. When the deposition is completed, the temperature of the carrier gas flow is T3, and it satisfies T1-T3=0~400℃, thus obtaining the initial product of the repair part.

[0045] Because reaction temperature has a significant impact on the rate of chemical vapor deposition (CVD), deposition is difficult to achieve on the surface of the part at lower temperatures. Furthermore, the parallel flow direction of the gas to the part surface makes it difficult for molecules to adhere and form islands, making silicon carbide deposition even more challenging on the undamaged surface. In contrast, the bottom of the defective part is located in a higher temperature region and is unaffected by surface gas flow. The slow gas flow rate allows for preferential deposition, and the silicon carbide deposition rate at the defective area is much higher than that at the undamaged area. This largely avoids the problem of excessive deposition on the repaired undamaged area and also solves the problem of hollow areas forming after repairing sharp defects.

[0046] Furthermore, the aforementioned silicon / carbon source reactant gas includes both carbon source and silicon source materials, with the silicon source materials including CH3SiCl3 and C7H. 20 At least one of Si2, SiH4, SiH3Cl, SiH2Cl2, SiHCl3, and SiCl4; the carbon source includes CH3SiCl3 and C7H 20 At least one of Si2 and C1-C4 alkanes. Specifically, CH3SiCl3 and C7H... 20 Si2 can be used as both a silicon source and a carbon source. Preferably, the silicon / carbon source reaction gas is CH3SiCl3 or C7H. 20 Si2.

[0047] Furthermore, when silicon / carbon source reaction gas is added to the reactant carrier gas stream for silicon carbide deposition, the volume ratio of carrier gas to silicon / carbon source reaction gas in the reactant carrier gas stream is 3 to 20:1, preferably 1:10 to 15:1.

[0048] Furthermore, during the silicon carbide deposition process, as the temperature of the carrier gas flow gradually increases from T2 to T3, the gas pressure inside the chamber gradually decreases to 500–1500 Pa (preferably, 700–1200 Pa). Gradually reducing the gas pressure inside the chamber during the heating process helps to further reduce the reaction rate, thereby reducing excess deposition on the surface of the silicon carbide part.

[0049] Step S4: Perform heat treatment and surface polishing on the initial repair part to obtain a silicon carbide part.

[0050] Because of the significant temperature gradient during the deposition process in step S3, the silicon carbide deposition rate varies during the repair process. Consequently, at the interface between the repair site and the substrate, there are varying degrees of internal stress and a small amount of defect concentration, which affects the bending strength of the component. Therefore, the initial repair part needs to be heat-treated to release stress and eliminate the impact of internal stress and a small amount of defect concentration from the deposition process on the component's strength.

[0051] The surface of the initial repair part is lightly polished. For parts with special requirements, dimensional correction is performed on special locations (inner wall of the hole, side of the step, etc.), thus completing the repair of this high-purity silicon carbide.

[0052] Furthermore, the initial heat treatment of the repaired parts is a three-stage heat treatment process, including:

[0053] (1) First, heat the furnace body to 1600-1700℃ (heating rate is 1-12℃ / min) and keep it at that temperature for 0.5-1.5h;

[0054] (2) Then heat the furnace body to 1750-1850℃ (heating rate is 1-3℃ / min), keep it at the temperature for 1.5-2.5h, and vibrate the repaired parts during the holding period;

[0055] (3) Finally, the furnace body is cooled to 1600-1700℃ (cooling rate is 1-3℃ / min) and then cooled along with the furnace.

[0056] This three-stage heat treatment process first preheats the part by raising the temperature to 1600℃ and holding it at that temperature, so that it has a uniform temperature field at high temperature. Then, the temperature is gradually raised to 1750℃ and held at that temperature. During this period, small-amplitude mechanical vibration is applied to the part to completely release the internal stress of the part. During this period, the crystal form of the part changes from β crystal form to α crystal form. With the external vibration and micro-lattice changes, the internal stress and lattice defects are eliminated.

[0057] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0058] Example

[0059] Example 1

[0060] This embodiment provides a repair method for high-purity silicon carbide parts, the flowchart of which is shown below. Figure 3 As shown, it includes:

[0061] (1) Dissolve surface contaminants, organic matter, and metal ion contaminants using liquid chemical solvents, and then apply ultrasonic waves, multiple rinses, and drying to the surface of the part to be repaired (e.g., ...). Figure 4 (As shown) a dust-free cleaning process was performed, and the deepest point to be repaired was measured to be 0.8 mm. The bending strength before repair was 138 MPa.

[0062] (2) After placing the part to be repaired in the chamber, evacuate the chamber and continuously introduce a small amount of argon and hydrogen mixture as a carrier gas. The volume ratio of argon to hydrogen is 2:1, and the chamber pressure is maintained at 2000pa (1000-3000).

[0063] (3) After the gas pressure stabilizes, a heat source (1200-1350℃) with a temperature T1 of 1300℃ is applied to the bottom of the part, and two cooling carrier gas streams are applied to the top of the part: a purge carrier gas stream parallel to the surface of the part (flow rate accounting for 66% of the total carrier gas flow rate), and a reactant carrier gas stream perpendicular to the surface of the part (flow rate accounting for 34% of the total carrier gas flow rate). The temperature T2 of both cooling carrier gas streams is 900℃. The chamber temperature inside the furnace is controlled to be slightly higher than the gas flow temperature and lower than the bottom heat source temperature, i.e., the chamber temperature is 1000℃, so that a stable, gradient temperature field with a higher temperature at the bottom and a lower temperature at the top is formed in the thickness direction (deposition direction) of the part. During this period, the gas pressure inside the chamber is maintained at 2000 Pa.

[0064] (4) After the gradient temperature field stabilizes, silicon / carbon source gas is introduced from the reactant carrier gas end, wherein the silicon / carbon source gas is CH3SiCl3, and the ratio of carrier gas to reactant gas is 3:1. Silicon carbide deposition is preferentially performed from the high-temperature part at the bottom of the defect in the part. During the deposition process, the temperature of the carrier gas flow is gradually increased to 1150℃;

[0065] (5) After removing the part, it is heat-treated and surface-polished at 1600℃ to obtain a silicon carbide part (e.g. Figure 5 (As shown).

[0066] Example 2

[0067] This embodiment provides a repair method for high-purity silicon carbide parts, including:

[0068] (1) Surface contaminants, organic matter and metal ion contaminants are dissolved by liquid chemical solvents, and the surface of the part to be repaired is cleaned in a dust-free manner by means of ultrasonic waves, multiple rinsing and drying, and the deepest depth of the part to be repaired is measured to be 0.8 mm, and the bending strength before repair is 138 MPa.

[0069] (2) After placing the part to be repaired in the chamber, evacuate the chamber and continuously introduce a small amount of argon and hydrogen mixture as a carrier gas. The volume ratio of argon to hydrogen is 1.5:1, and the chamber pressure is maintained at 1500 Pa.

[0070] (3) After the gas pressure stabilizes, a heat source with a temperature T1 of 1200℃ is applied to the bottom of the part, and two cooling carrier gas streams are applied to the top of the part: a purge carrier gas stream parallel to the surface of the part (flow rate accounting for 80% of the total carrier gas flow rate), and a reactant carrier gas stream perpendicular to the surface of the part (flow rate accounting for 20% of the total carrier gas flow rate). The temperature T2 of both cooling carrier gas streams is 1000℃. The chamber temperature inside the furnace is controlled to be slightly higher than the gas flow temperature and lower than the bottom heat source temperature, i.e., the chamber temperature is 1100℃, so that a stable, gradient temperature field with a higher temperature at the bottom and a lower temperature at the top is formed in the thickness direction of the part. During this period, the gas pressure inside the chamber is maintained at 1500 Pa.

[0071] (4) After the gradient temperature field stabilizes, silicon / carbon source gas is introduced from the reactant carrier gas end. The silicon / carbon source gas is a 1:1 mixture of SiCl4 and methane, and the ratio of carrier gas to reactant gas is 5:1. Silicon carbide deposition is preferentially performed from the high-temperature part at the bottom of the part defect. During the deposition process, the temperature of the carrier gas flow is gradually increased to 1200℃;

[0072] (5) After the part is removed, it is heat-treated and surface-polished at 1600℃ to obtain the silicon carbide part.

[0073] Example 3

[0074] This embodiment provides a repair method for high-purity silicon carbide parts, including:

[0075] (1) Surface contaminants, organic matter and metal ion contaminants are dissolved by liquid chemical solvents, and the surface of the part to be repaired is cleaned in a dust-free manner by means of ultrasonic waves, multiple rinsing and drying, and the deepest depth of the part to be repaired is measured to be 0.8 mm, and the bending strength before repair is 138 MPa.

[0076] (2) After placing the part to be repaired in the chamber, evacuate the chamber and continuously introduce a small amount of argon and hydrogen mixture as a carrier gas. The volume ratio of argon to hydrogen is 1.5:1, and the chamber pressure is maintained at 1000 Pa.

[0077] (3) After the gas pressure stabilizes, a heat source with a temperature T1 of 1350℃ is applied to the bottom of the part, and two cooling carrier gas streams are applied to the top of the part: a purge carrier gas stream parallel to the surface of the part (flow rate accounting for 50% of the total carrier gas flow rate), and a reactant carrier gas stream perpendicular to the surface of the part (flow rate accounting for 50% of the total carrier gas flow rate). The temperature T2 of both cooling carrier gas streams is 700℃. The chamber temperature inside the furnace is controlled to be slightly higher than the gas flow temperature and lower than the bottom heat source temperature, i.e., the chamber temperature is 900℃, so that a stable, gradient temperature field with a higher temperature at the bottom and a lower temperature at the top is formed in the thickness direction of the part. During this period, the gas pressure inside the chamber is maintained at 1000 Pa.

[0078] (4) After the gradient temperature field stabilizes, silicon / carbon source gas is introduced from the reactant carrier gas end. The silicon / carbon source gas is CH3SiCl3, and the ratio of carrier gas to reactant gas is 10:1. Silicon carbide deposition is preferentially performed from the high-temperature part at the bottom of the defect in the part. During the deposition process, the temperature of the carrier gas flow is gradually increased to 1050℃;

[0079] (5) After the part is removed, it is heat-treated and surface-polished at 1600℃ to obtain the silicon carbide part.

[0080] Example 4

[0081] This embodiment provides a repair method for high-purity silicon carbide parts, the steps of which are basically the same as those in Embodiment 1, except for the heat treatment method in step (5):

[0082] 1. Heat to 1650℃ at a heating rate of 10℃ / min and hold for 1 hour; 2. Heat to 1800℃ at a heating rate of 2℃ / min and hold for 2 hours, during which time the workpiece is frequently subjected to mechanical vibration.

[0083] ③ After cooling to 1650℃ at a rate of 1℃ / min, it is cooled in the furnace. The entire process is carried out in an inert atmosphere, and the heat treatment process is not fixed, but depends on parameters such as the structure of the part, the overall thickness, and the repair thickness.

[0084] Example 5

[0085] This embodiment provides a repair method for high-purity silicon carbide parts. The steps are basically the same as those in embodiment 4. The difference is that there is no vibration in the second step of the heat treatment process in step (5) to examine its effect on the strength of the parts, as shown in Table 1.

[0086] Table 1. Influence of heat treatment process on internal stress of the part

[0087]

[0088] As shown in Table 1, compared with Example 1, Examples 4 and 5 adopted a three-stage heat treatment process, which effectively improved the bending strength of the repaired parts; in particular, in Example 4, mechanical vibration was added during the heating and heat preservation process, and the bending strength of the repaired parts was the best, which largely restored the original mechanical properties of the parts.

[0089] Comparative Example 1

[0090] This comparative example provides a repair method for high-purity silicon carbide parts, the steps of which are basically the same as those in Example 4, except that the temperature in the thickness direction of the high-purity silicon carbide is controlled to be a stable and uniform temperature field of 1000°C.

[0091] Comparative Example 2

[0092] This comparative example provides a repair method for high-purity silicon carbide parts, the steps of which are basically the same as those in Example 4, except that the carrier gas flow (carrier gas to CH3SiCl3 ratio is 3:1) is a single stream and the flow direction is perpendicular to the surface of the part.

[0093] Comparative Example 3

[0094] This comparative example provides a repair method for high-purity silicon carbide parts, the steps of which are basically the same as those in Example 4, except that the carrier gas flow (carrier gas to CH3SiCl3 ratio is 3:1) is a single stream and the flow direction is horizontal to the surface of the part.

[0095] Comparative Example 4

[0096] This comparative example provides a repair method for high-purity silicon carbide parts, the steps of which are basically the same as those in Example 4, except that:

[0097] The heat source temperature T1 is 1300℃, the carrier gas flow temperature T2 is 1200℃, and T3 is 1200℃;

[0098] Comparative Example 5

[0099] This comparative example provides a repair method for high-purity silicon carbide components. The steps are basically the same as those in Example 4, except that the heat source temperature T1 is 1300℃, the carrier gas flow temperature T2 is 900℃, and T3 is 800℃.

[0100] Comparative Example 6

[0101] This comparative example provides a prior art repair process using dressing pyrolysis, which includes:

[0102] Weigh out 15 wt% polyborosilazane, 25 wt% SiC powder, 25 wt% ZrB2 powder, and 35 wt% petroleum ether, respectively, where the SiC powder has a particle size of 500 nm and the ZrB2 powder has a particle size of 200 nm. Place the above materials in a ceramic ball mill jar and ball mill for 30 minutes to form a coating slurry. Grind the damaged areas of the SiC composite coating to form a buffer zone with a width of 5 mm, wash and dry. Use a brush to apply the coating slurry to the surface of the composite material, allowing it to dry after each layer, until it is flush with the surrounding coating. Set the temperature of the hot air gun to 240℃ and blow for 90 minutes to cure the coating. At this point, the damaged areas of the SiC composite coating are repaired.

[0103] Performance tests were conducted on the repaired silicon carbide parts from Examples 4 and Comparative Examples 1-6:

[0104] I. Testing Method:

[0105] (1) Purity after repair

[0106] Its purity was determined by glow discharge mass spectrometry (GDMS).

[0107] (2) Density after repair

[0108] Its density was tested using the Archimedes (displacement) method, and the ratio of its density to the standard density of the sample was used to determine the homogeneous density.

[0109] (3) Thickness of excess deposit after repair

[0110] The thickness of the excess deposit after repair can be determined by calculating the difference in part thickness before and after deposition.

[0111] (4) Dimensions of the missing tip after repair

[0112] The dimensions of the defect tip after repair were determined by observing the cross-section of the repaired part under an optical microscope.

[0113] (5) Polishing time after repair

[0114] Based on the current average grinding speed of 15μm / h, the grinding time for different thicknesses was calculated.

[0115] (6) Bending strength

[0116] The bending strength under three-point bending was tested using a universal testing machine according to ISO-14704-2000.

[0117] II. Test Results:

[0118] As shown in Table 3.

[0119] Table 3. Performance comparison of repair processes in Example 4 and Comparative Examples 1-6

[0120]

[0121]

[0122] As can be seen from Table 3, compared with the repair processes provided in Comparative Examples 1-6, the repair process of Example 4 of this application for repairing high-purity silicon carbide parts can not only improve the purity and density of the repaired area, but also result in a small defect tip size and no tip hollowing phenomenon; at the same time, the thickness of the excess deposit on the surface of the silicon carbide part is small, which greatly reduces the polishing time.

[0123] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for repairing high-purity silicon carbide parts, characterized in that, It includes: The part to be repaired is placed in the chamber, and after evacuation, carrier gas is continuously introduced. After the gas pressure in the chamber stabilizes, a heat source is applied to the bottom of the workpiece to be repaired, and two carrier gas streams are applied to the top of the workpiece to be repaired to form a gradient temperature field in the deposition direction of the workpiece to be repaired; wherein, the carrier gas streams include a purge carrier gas stream parallel to the surface of the workpiece to be repaired and a reactant carrier gas stream perpendicular to the surface of the workpiece to be repaired, the temperature of the heat source is T1, and the temperature of the carrier gas streams is T2, and satisfies: T1- T2= 200~700℃; After the gradient temperature field stabilizes, silicon / carbon source reaction gas is added to the reactant carrier gas stream to perform silicon carbide deposition, and the temperature of the carrier gas stream is gradually increased. When the deposition is completed, the temperature of the carrier gas stream is T3, and it satisfies T1-T3=0~400℃, thus obtaining the initial product of the repair part. The initial repair part is subjected to heat treatment and surface polishing to obtain a silicon carbide part.

2. The repair method for high-purity silicon carbide parts according to claim 1, characterized in that, The heat source temperature T1 applied to the bottom of the part to be repaired is 1200~1300℃.

3. The repair method for high-purity silicon carbide parts according to claim 1, characterized in that, The flow rate ratio of the purge carrier gas to the reactant carrier gas is 5~8:2~5.

4. The repair method for high-purity silicon carbide parts according to claim 1, characterized in that, During the formation of the gradient temperature field and the silicon carbide deposition process, the chamber is in a stable low-pressure state of 1000~3000Pa; when the temperature of the carrier gas flow gradually increases from T2 to T3 during silicon carbide deposition, the gas pressure in the chamber gradually decreases to 500~1500Pa.

5. The repair method for high-purity silicon carbide parts according to any one of claims 1-4, characterized in that, The initial heat treatment of the repaired part is a three-stage heat treatment process, including: First, heat the furnace body to 1600~1700℃ and hold it at that temperature for 0.5~1.5 hours; The furnace body is then heated to 1750~1850℃ and held for 1.5~2.5 hours, while the initial repaired part is vibrated during the holding period. Finally, the furnace body is cooled to 1600~1700℃ and then cooled along with the furnace.

6. The repair method for high-purity silicon carbide parts according to claim 5, characterized in that, In the three-stage heat treatment process, the heating rate of the first stage is 1~12℃ / min, the heating rate of the second stage is 1~3℃ / min, and the cooling rate of the third stage is 1~3℃ / min.

7. The repair method for high-purity silicon carbide parts according to claim 1, characterized in that, The silicon / carbon source reactant gas includes a carbon source and a silicon source, wherein the silicon source includes CH3SiCl3 and C7H. 20 At least one of Si2, SiH4, SiH3Cl, SiH2Cl2, SiHCl3, and SiCl4; the carbon source includes CH3SiCl3 and C7H 20 At least one of Si2 and C1-C4 alkanes.

8. The repair method for high-purity silicon carbide parts according to claim 1, characterized in that, When silicon / carbon source reaction gas is added to the reactant carrier gas stream for silicon carbide deposition, the volume ratio of the carrier gas to the silicon / carbon source reaction gas in the reactant carrier gas stream is 3~20:

1.

9. The repair method for high-purity silicon carbide parts according to claim 1 or 8, characterized in that, The carrier gas is hydrogen and argon in a volume ratio of 1:1 to 3.

10. The repair method for high-purity silicon carbide parts according to any one of claims 1-4, characterized in that, Before placing the part to be repaired into the chamber, the process also includes a step of performing a dust-free cleaning treatment on the surface of the part to be repaired.

Images