Method and equipment for removing residual silicon on surface of reactive sintering silicon carbide or carbon ceramic by laser

Abstract

The invention aims to provide a method and equipment for removing residual silicon on the surface of reaction-sintered silicon carbide ceramic or carbon ceramic with a complex structure, and belongs to the technical field of silicon carbide ceramic or carbon ceramic. According to the method, residual silicon is corroded through laser cladding alkali powder, inert gas purging and sand blasting treatment are combined, the position and parameters of the residual silicon are determined through pre-scanning, laser and alkali powder treatment is accurately controlled, efficient removal is achieved, and damage to a base material is avoided. The device comprises a pre-scanning device, a workbench, a laser generating device, a powder supply device, a control device and a closed working chamber, flexible programming and precise operation are ensured through intelligent control, inert gas purges and protects a base body, oxidation is avoided, meanwhile, alkali corrosion residues are effectively removed, the closed working chamber controls the atmosphere, environmental pollution is prevented, and operation safety is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon carbide ceramics or carbon ceramics, and in particular relates to a method and equipment for removing residual silicon on the surface of reaction-sintered silicon carbide ceramics or carbon ceramic parts. Background Art

[0002] Reaction sintered silicon carbide or carbon ceramics have the advantages of low sintering temperature, near net size molding, high hot strength, no deformation at high temperature, high thermal conductivity, oxidation resistance, wear resistance and good chemical stability. It has been widely used in aerospace, thermal engineering, semiconductors and lithium batteries. The preparation process of reaction sintered silicon carbide ceramics or carbon ceramics first prepares a porous SiC / C or C / C blank, and uses liquid silicon or gaseous silicon as an infiltrant. Liquid or gaseous silicon infiltrates the blank through the capillary action of the porous material and sinters it into a ceramic part. After the infiltration reaction, as the temperature decreases, part of the silicon liquid adheres to the surface of the ceramic workpiece.

[0003] For some components with complex structures, the residual silicon on the surface of the components is removed by machining, such as sandblasting, grinding and other processing methods. However, for hard and brittle materials, machining is time-consuming and difficult, and the removal is not thorough, and there is a risk of cracking during the processing of thin-walled structures.

[0004] The silicon remaining on the surface of the reaction-sintered silicon carbide or carbon ceramic workpiece is firmly attached and extremely stable at room temperature. It hardly reacts with acid and alkali. It is difficult to remove it by sandblasting directly, but it is easy to damage the silicon carbide or carbon ceramic workpiece. When the strong alkali is heated to about 400°C, the metallic silicon reacts violently with the alkali to generate Na2SiO3 or K2SiO3 residues, which may also adhere to the matrix and cause pollution. Although silicon carbide does not react with alkali, the silicon carbide matrix often contains elemental silicon. The residual silicon on the surface of the silicon carbide matrix is ​​removed by immersing the workpiece in hot alkali, which often corrodes part of the elemental silicon in the matrix structure of the workpiece, thereby causing hole defects inside the workpiece. The method of removing residual silicon by immersing the workpiece in hot alkali reaction has a large safety risk, poor controllability, and is prone to overreaction and damage to the original substrate of the component.

[0005] Therefore, there is an urgent need to propose a method for removing residual silicon on the surface of brittle and hard materials, especially reaction-sintered silicon carbide or carbon ceramic complex components without damaging the component substrate. Summary of the invention In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method and equipment for removing residual silicon on the surface of complex structure reaction-sintered silicon carbide ceramics or carbon ceramics, using laser cladding alkali powder corrosion reaction sintered silicon carbide workpiece surface residual silicon, while coordinating with inert gas purging and sand blasting to achieve accurate and efficient removal of residual silicon in the component.

[0006] To achieve the above object, the present invention provides the following technical solutions: The first object of the present invention is to provide a method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic, comprising the following steps: Step 1, performing a first scan on the workpiece to be processed, and recording the position parameters and size parameters of residual silicon at various locations on the surface of the workpiece to be processed; Step 2, based on the position parameters and size parameters, set residual silicon removal process parameters, and sequentially perform laser alkaline thermal melting-sandblasting composite treatment on the residual silicon at various positions on the surface of the workpiece to be processed to remove the residual silicon; Step 3, performing a second scan on the workpiece after being processed in step 2 to determine whether the residual silicon on the surface of the workpiece has been cleaned. If there is still residual silicon remaining, repeat step 2 until no residual silicon remains; Step 4, cleaning the workpiece from which the residual silicon has been completely removed.

[0007] Preferably, the laser alkaline thermal melting-sandblasting composite treatment is specifically: Alkali powder is delivered to the residual silicon position and laser thermal melting is performed simultaneously to perform alkali corrosion on the residual silicon. At the same time, the residual silicon alkali corrosion position is sandblasted to remove the alkali corrosion residues generated by laser ablation of the residual silicon.

[0008] Further preferably, the powder feeding gas for delivering the alkali powder is an inert gas with a gas pressure of 0.4~0.8MPa, a gas flow rate of 0~10L / min, and an adjustment accuracy of ±1%. The alkali powder is sodium hydroxide or potassium hydroxide; the compressed gas pressure used for the sand blasting is 0.3~0.7MPa, and the sand used for sand blasting is one or more of corundum, corundum, garnet sand, and quartz sand.

[0009] Further preferably, inert gas is simultaneously used to purge the working area during the laser alkaline thermal melting-sand blasting composite treatment, so as to further protect the silicon components in the substrate near the laser alkaline thermal melting-sand blasting composite treatment working area.

[0010] More preferably, the particle size of the alkali powder is 10-200 μm, and the particle size of the sand used for the sandblasting treatment is 100-2000 μm.

[0011] Preferably, the residual silicon removal process parameters include: laser power, laser spot diameter, powder feeding speed, scanning speed, hot melt thickness and overlap rate.

[0012] Preferably, the laser power is 1-10 kW, the spot diameter is 0.2-5 mm, the powder feeding speed is 2-12 kg / h, the scanning speed is 0.2-2 m / min, the cladding thickness is 0.2-1.2 mm, and the overlap rate is 30%-80%.

[0013] Preferably, the above method is carried out under a protective atmosphere.

[0014] The second object of the present invention is to provide a device for realizing the above-mentioned method of laser cleaning residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic, comprising: A pre-scanning device, used to check and record the position parameters and geometric parameters of residual silicon on the surface of the workpiece to be processed; A workbench, used to place workpieces to be processed; A laser generating device, comprising a laser source and a laser beam channel, wherein the laser beam channel is suspended above the workbench; A powder supply device, including an alkali powder spray chamber and a sandblasting gun, is fixedly connected to the laser beam channel, the alkali powder spray gun nozzle and the sandblasting gun nozzle are aligned with the residual silicon removal area, the alkali powder spray gun is connected to the alkali powder feeder, and the sandblasting gun is connected to the sand powder feeder; A control device, which controls the motion path of the laser generating device and the powder supply device and the residual silicon removal process parameters according to the position parameters and geometric parameters of the residual silicon obtained by the pre-scanning device; The laser generating device, the control device, the powder supply device and the workbench are arranged in the closed working room, and the floating powder in the closed working room is sucked and collected by the exhaust and exhaust system.

[0015] Preferably, the exhaust duct and exhaust duct of the exhaust and exhaust device are independently made of polypropylene, polyvinyl chloride, high-density polyethylene or polytetrafluoroethylene; a spray water tank is also provided outside the closed working room, the spray water tank is connected to the air outlet of the exhaust port, and the spray water tank contains an aqueous solution of an acidic substance to reabsorb and neutralize the strong alkaline substance extracted from the closed working room, and the acidic substance is one or more of citric acid, acetic acid, boric acid or hydrochloric acid.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The method for removing residual silicon on the surface of complex structure reaction sintered silicon carbide ceramic or carbon ceramic adopted by the present invention determines the position, area and thickness of residual silicon on the workpiece to be processed by pre-scanning, edits the movement route of the laser head, sets the laser output power and alkali powder delivery amount, gas flow rate and other parameters, uses laser cladding to alkali powder corrosion reaction sintered silicon carbide workpiece surface residual silicon, and cooperates with sandblasting and blowing to remove the residues produced by alkali corrosion residual silicon, so as to achieve accurate and efficient removal of residual silicon on the component, and will not cause damage to the workpiece substrate caused by machining or hot alkali immersion removal. The present invention adopts intelligent equipment and control system, the movement trajectory can be flexibly programmed, the laser head movement is flexible and accurate, and can cope with complex components.

[0017] Furthermore, the present invention provides a gas purge device, and when cleaning the residual silicon on the surface of the easily oxidizable substrate, an inert gas can be used to purge the working area, so as to protect the components in the silicon carbide ceramic or carbon ceramic that are easily oxidized and ablated by oxygen. The sandblasting treatment after the laser head alkali ablation of the residual silicon can avoid the floating Na2SiO3 or K2SiO3 generated by the reaction from cooling again and adhering to the surface of the workpiece to cause secondary pollution. The surface residue can be cleaned by using a relatively small gas pressure.

[0018] The laser device for removing residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic proposed in the present invention can be arranged in a closed space. On the one hand, the atmosphere of the closed space can be controlled, and the working area can be adjusted to an inert reaction area, which can further prevent unnecessary oxidation processes during the alkali ablation cleaning process of the workpiece. On the other hand, by arranging a ventilation and exhaust system in the closed working room, the pollution of the environment by strong alkaline substances is effectively avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A diagram of a workpiece to be cleaned in Example 1 of the present invention; Figure 2 A diagram of a workpiece to be cleaned in Example 2 of the present invention; Figure 3 A diagram of a workpiece to be cleaned in Example 3 of the present invention; Figure 4 A physical picture of a workpiece before and after silicon is removed by the method of the present invention; Figure 5 is a flow chart of the method of the present invention; Among them, there are workpiece 1 to be processed, workpiece 2 to be processed, and workpiece 3 to be processed. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0022] See also Figure 5 , is a flow chart of the cleaning method of the present invention, and the present invention is further described in detail below in conjunction with the accompanying drawings: Example 1 A split mobile robot flexible cladding processing system is adopted, including a robot joint arm mechanism, a laser, a powder feeder, an intelligent control system, a compressed air or inert gas supply station, etc.

[0023] The closed studio is made of polypropylene, and the workpiece-bearing platform is made of N08926 alloy. The closed studio is equipped with a ventilation and exhaust system. The pipe material is polyvinyl chloride. The collected alkaline dust is absorbed and neutralized by the aqueous solution of the acidic substance in the water tank and then recycled. The acidic substance is glacial acetic acid.

[0024] The capacity of a single powder tube of the powder feeder is 1.5L, and 10μm sodium hydroxide powder is used. Corundum sand particles with a particle size of 100μm are used, and sandblasting is used to remove residues.

[0025] 1) For Figure 1 The workpiece 1 with a thin-wall cavity structure shown in the figure is pre-scanned to record the position and size parameters of the residual silicon in the workpiece to be processed; 2) Fix the workpiece 1 on the workbench, fill the alkali powder and sand into the powder feeder respectively, close the closed working room, and set the laser head movement path, process parameters and powder feeding amount according to the position of residual silicon in the workpiece 1: The alkali powder feeding rate is 2g / min; the alkali powder feeding gas is compressed air with an air pressure of 0.4MPa and a gas flow rate of 1L / min; compressed air is used for sandblasting with a compressed air pressure of 0.3MPa; the laser power is set to 2KW, the spot diameter is 1mm, the powder feeding speed is 2Kg / h, the scanning speed is 0.5m / min, the cladding thickness is 0.1mm, and the overlap rate is 50%.

[0026] 3) Turn on the laser generator, and at the same time turn on the exhaust and ventilation systems and control devices. The exhaust and ventilation systems exhaust the alkaline waste gas generated during the process; 4) According to the working parameters determined in step 2), the laser head moves to the top of the residual silicon of the workpiece 1, firstly sends out alkali powder for alkali powder laser heat melting, alkali corrodes the silicon on the surface of the workpiece 1, and then sandblasts the sandblasting pipeline to remove the residue attached to the surface of the workpiece 1; 5) Repeat the process of step 4) on different residual silicon until the residual silicon on the surface of the workpiece 1 is removed.

[0027] 6) Keep the purge system open and turn off other devices until the pH value of the acidic aqueous solution in the spray water tank no longer increases; 7) Open the closed working room, remove the workpiece 1, soak and clean the surface of the workpiece 1 with a large amount of pure water until the pH value of the cleaned aqueous solution reaches about 7, and dry the workpiece 1.

[0028] Example 2 An integrated mobile robot flexible cladding processing system is adopted, including a robot articulated arm mechanism, a laser, a powder feeder, a high-speed laser cladding head, an intelligent control system, a compressed air or inert gas supply station, etc.

[0029] The closed workroom is made of high-density polyethylene, and the workpiece-bearing platform is made of 316L stainless steel. The closed workroom is equipped with a ventilation and exhaust system, and the pipe material is polytetrafluoroethylene. The collected alkaline dust is absorbed and neutralized by an acidic aqueous solution and then recycled. The acidic substance is citric acid.

[0030] The capacity of a single powder tube of the powder feeder is 2L. It uses 20μm sodium hydroxide powder and quartz sand with a particle size of 200μm. Sand blasting is used to remove residues.

[0031] The specific steps are as follows: 1) For Figure 2 The workpiece 2 with a circular complex structure shown in the figure is pre-scanned to record the position and size parameters of the residual silicon in the workpiece 2 to be processed; 2) Fix the workpiece 2 on the workbench, fill the sodium hydroxide powder and quartz sand into the powder feeder respectively, close the closed working room, and set the laser head movement path, process parameters and powder feeding amount according to the position of the residual silicon in the circular complex structure: The feed rate is 15g / min; the powder feeding gas is compressed air with an air pressure of 0.6MPa and a gas flow rate of 3L / min; compressed air is used for sandblasting with a compressed air pressure of 0.5MPa; the process parameters for laser desiliconization are set as follows: laser power 4KW, spot diameter 2mm, powder feeding speed 4Kg / h, scanning speed 1m / min, cladding thickness 0.3mm, and overlap rate 40%.

[0032] 3) Turn on the laser generator, and at the same time turn on the exhaust and ventilation systems and control devices. The exhaust and ventilation systems exhaust the alkaline waste gas generated during the process; 4) According to the working parameters determined in step 2), the laser head moves to the top of the residual silicon of the workpiece 2, firstly sends out alkali powder for alkali powder laser heat melting, alkali corrodes the silicon on the surface of the workpiece 2, and then sandblasts the pipe to remove the residue attached to the surface of the workpiece 2; 5) Repeat the process of step 4) on different residual silicon on the workpiece 2 until the residual silicon on the surface of the workpiece 2 is removed.

[0033] 6) Keep the purge system open and turn off other devices until the pH value of the acidic aqueous solution in the spray water tank no longer increases; 7) Open the closed working room, remove the workpiece 2, soak and clean the surface of the workpiece 2 with a large amount of pure water until the pH value of the cleaned aqueous solution reaches about 7, and dry the workpiece 2.

[0034] Example 3 An integrated mobile robot flexible cladding processing system is adopted, including a robot articulated arm mechanism, a laser, a powder feeder, a high-speed laser cladding head, an intelligent control system, a compressed air or inert gas supply station, etc.

[0035] The closed studio is made of polypropylene, and the workpiece-bearing platform is made of 304 stainless steel. The studio is equipped with a ventilation and exhaust system, and the pipe material is polytetrafluoroethylene. The collected alkaline dust is absorbed and neutralized by an acidic aqueous solution and then recycled. The acidic substance is boric acid.

[0036] The capacity of a single powder tube of the powder feeder is 5L, and 100μm potassium hydroxide powder is used. Garnet sand with a particle size of 150μm is used, and sandblasting is used to remove residues.

[0037] The specific steps are as follows: 1) For Figure 3 The workpiece 3 with a circular complex structure shown in the figure is pre-scanned to record the position and size parameters of the residual silicon in the workpiece 3 to be processed; 2) Fix the workpiece 3 on the workbench, fill the sodium hydroxide powder and quartz sand into the powder feeder respectively, close the closed working chamber, and set the laser head movement path, process parameters and powder feeding amount according to the position of residual silicon in the workpiece 3: The feed rate is 5g / min; the powder feeding gas is compressed air with an air pressure of 0.5MPa and a gas flow rate of 2L / min; compressed air is used for sandblasting with a compressed air pressure of 0.4MPa; the process parameters for laser desiliconization are set as follows: laser power 5KW, spot diameter 3mm, powder feeding speed 6Kg / h, scanning speed 2m / min, cladding thickness 0.5mm, and overlap rate 30%.

[0038] 3) Turn on the laser generator, and at the same time, the exhaust system and control device, and the exhaust system exhausts the alkaline waste gas generated during the process; 4) According to the working parameters determined in step 2), the laser head moves to the top of the residual silicon on the surface of the workpiece 3, firstly sends out alkali powder for alkali powder laser heat melting, alkali corrodes the silicon on the surface of the workpiece 3, and then sandblasts the pipe to remove the residue attached to the surface of the workpiece 3; 5) Repeat the process of step 4) on different residual silicon on the workpiece 3 until the residual silicon on the surface of the workpiece 3 is removed.

[0039] 6) Keep the ventilation and exhaust systems open and turn off other devices until the pH value of the acidic aqueous solution in the spray water tank no longer increases; 7) Open the sealed working room, remove the workpiece 3, soak and clean the surface of the workpiece 3 with a large amount of pure water until the pH value of the cleaned aqueous solution reaches about 7, and dry the workpiece 3.

[0040] Figure 4 The left side shows the workpiece surface before cleaning according to the present invention, and the right side shows the workpiece surface after treatment. It can be seen that the residual silicon on the workpiece surface has been completely treated, and the treatment result is good.

[0041] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for removing residual silicon on the surface of reactively sintered silicon carbide or carbon ceramic by laser, characterized in that: The following steps are involved: Step 1, performing a first scan on the workpiece to be processed, and recording the position parameters and size parameters of residual silicon at various locations on the surface of the workpiece to be processed; Step 2, based on the position parameters and size parameters, set residual silicon removal process parameters, and sequentially perform laser alkaline thermal melting-sandblasting composite treatment on the residual silicon at various positions on the surface of the workpiece to be processed to remove the residual silicon; Step 3, performing a second scan on the workpiece after being processed in step 2 to determine whether the residual silicon on the surface of the workpiece has been cleaned. If there is still residual silicon remaining, repeat step 2 until no residual silicon remains; Step 4, cleaning the workpiece from which the residual silicon has been completely removed.

2. The method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to claim 1, characterized in that: The laser alkaline thermal melting-sandblasting composite treatment is specifically: Alkali powder is delivered to the residual silicon position and laser thermal melting is performed simultaneously to perform alkali corrosion on the residual silicon. At the same time, the residual silicon alkali corrosion position is sandblasted to remove the alkali corrosion residues generated by laser ablation of the residual silicon.

3. The method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to claim 2, characterized in that: The powder feeding gas for sending out the alkali powder is an inert gas with a gas pressure of 0.4~0.8MPa, a gas flow rate of 0~10L / min, and an adjustment accuracy of ±1%. The alkali powder is selected from sodium hydroxide or potassium hydroxide; the compressed gas pressure used for the sand blasting is 0.3~0.7MPa, and the sand used for sand blasting is one or more of corundum, corundum, garnet sand, and quartz sand.

4. The method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to claim 2, characterized in that: In the laser alkaline thermal melting-sandblasting composite treatment, an inert gas is simultaneously used to purge the working area.

5. The method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to claim 2, characterized in that: The particle size of the alkali powder is 10-200 μm, and the particle size of the sand used for the sandblasting treatment is 100-2000 μm.

6. The method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to claim 1, characterized in that: The residual silicon removal process parameters include: laser power, laser spot diameter, powder feeding speed, scanning speed, hot melt thickness and overlap rate.

7. The method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to claim 6, characterized in that: The laser power is 1-10 kW, the spot diameter is 0.2-5 mm, the powder feeding speed is 2-12 kg / h, the scanning speed is 0.2-2 m / min, the cladding thickness is 0.2-1.2 mm, and the overlap rate is 30%-80%.

8. The method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to any one of claims 1 to 7, characterized in that: Carry out under protective atmosphere.

9. A device for implementing the method for laser removal of residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic as described in any one of claims 1 to 8, characterized in that: include: A pre-scanning device, used to check and record the position parameters and geometric parameters of residual silicon on the surface of the workpiece to be processed; A workbench, used to place workpieces to be processed; A laser generating device, comprising a laser source and a laser beam channel, wherein the laser beam channel is suspended above the workbench through a mechanical arm; A powder supply device, including an alkali powder spray chamber and a sandblasting gun, is fixedly connected to the laser beam channel, the alkali powder spray gun nozzle and the sandblasting gun nozzle are aligned with the residual silicon removal area, the alkali powder spray gun is connected to the alkali powder feeder, and the sandblasting gun is connected to the sand powder feeder; A control device, which controls the motion path of the laser generating device and the powder supply device and the residual silicon removal process parameters according to the position parameters and geometric parameters of the residual silicon obtained by the pre-scanning device; The laser generating device, the control device, the powder supply device and the workbench are arranged in the closed working room, and the floating powder in the closed working room is collected by the exhaust and exhaust system.

10. The laser cleaning device for residual silicon on the surface of reaction-sintered silicon carbide or carbon ceramic according to claim 9, characterized in that: The exhaust and exhaust device pipes are independently made of polypropylene, polyvinyl chloride, high-density polyethylene or polytetrafluoroethylene; a spray water tank is also provided outside the closed working room, the spray water tank is connected to the air outlet of the exhaust port, and the spray water tank contains an aqueous solution of an acidic substance to reabsorb and neutralize the strong alkaline substance extracted from the closed working room. The acidic substance is one or more of citric acid, acetic acid, boric acid or hydrochloric acid.

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