Laser deposition-chemical mechanical grinding integrated flexible forming system and method for complex curved surface ceramic coating

Abstract

The invention relates to a laser deposition-chemical mechanical grinding integrated flexible forming system and method for a complex curved surface ceramic coating. The laser deposition-chemical mechanical grinding integrated flexible forming system comprises a workpiece preheating unit, a ceramic powder electrostatic spraying unit, a laser deposition unit and a ceramic coating chemical mechanical grinding unit. The workpiece preheating unit preheats a workpiece to a certain temperature, and the electrostatic spraying unit, the laser deposition unit and the chemical mechanical grinding unit are connected with a multi-degree-of-freedom mechanical arm through an indexable clamp and are arranged on a machine tool body to realize switching of all the units; the electrostatic spraying unit is used for uniformly spraying ceramic powder on the surface of the preheated workpiece; the laser deposition unit is used for melting and depositing ceramic powder on the surface of a workpiece to form a ceramic coating; and the chemical mechanical grinding unit is used for performing high-quality and high-efficiency forming processing on the complex curved surface ceramic coating. According to the method, high-efficiency preparation of the complex curved surface ceramic coating with low surface defects and high bonding strength can be realized, and finally, the wear resistance and corrosion resistance of parts in an extreme environment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of surface modification and precision machining of advanced metal alloy materials, and in particular to a laser deposition-chemical mechanical grinding integrated flexible forming system and method for ceramic coatings on complex curved surfaces. Background Art

[0002] Compared with metal alloys, ceramics have significantly higher hardness and excellent wear resistance, high temperature resistance and corrosion resistance. Therefore, depositing ceramic materials on the surface of metal alloys to form a dense ceramic coating without surface defects can effectively improve the ability of alloy materials to resist deformation and failure caused by external high mechanical loads in extreme service environments, and obtain high wear resistance and corrosion resistance.

[0003] At present, ceramic powders commonly used to prepare ceramic coatings involve titanium dioxide, aluminum oxide or composite powders of the two. Ceramic powders have extremely high melting points (usually greater than 1600°C), so high-energy beam laser deposition methods are widely used to prepare wear-resistant ceramic coatings on the surface of metal plates. The metal matrix and ceramic powder are melted simultaneously by the rapid heating effect of the high-power laser beam to form a metallurgical bonding layer of ceramic and metal, thereby improving the wear resistance of the product. Laser-deposited ceramic coatings have the advantages of high bonding strength, good coating density, and high controllability. However, the temperature gradient effect of rapid heating and cooling during laser deposition can cause microcracks between the substrate and the coating and inside the coating. At the same time, when the ceramic powder melts rapidly, the residual gas between the powders cannot be quickly discharged, which leads to residual pores in the coating, ultimately affecting the mechanical properties of the coating. In addition, the surface of the laser-deposited ceramic coating will have defects such as cracks and holes, and the ceramic coating solidified by "pressureless" natural cooling is uneven, so subsequent mechanical processing is required to remove surface defects and flatten the coating.

[0004] The ceramic coating prepared by laser deposition has the characteristics of high hardness and low fracture toughness, as well as defects such as microcracks and holes on the surface. Therefore, the subsequent mechanical processing needs to be relatively "gentle". Excessive mechanical force will further induce the expansion of surface cracks, which will then extend into the coating, eventually leading to the failure of the protective performance of the entire coating. Therefore, a ductile domain grinding technology that controls the maximum undeformed cutting thickness to be less than the critical grinding depth for cracks in the coating material is a key strategy for efficiently obtaining high-quality ceramic coatings.

[0005] At present, the conventional ductile domain abrasive processing method is to use fixed abrasive grinding or abrasive water jet for processing, but the worktable size and movement direction of the grinding machine are limited, which makes it impossible to perform precision grinding of ceramic coatings on the surface of large parts or complex curved parts, and it is also impossible to achieve integrated manufacturing of coating deposition and grinding. Abrasive water jet uses high-pressure water and abrasives to erode and micro-cut the coating respectively to achieve material removal, but the high-speed impact of the high-pressure jet will cause further expansion of cracks on the coating surface, and the fine abrasives will be embedded in the pores of the coating, which will affect the final forming performance.

[0006] Patent CN20221077500.3 proposes a method for preparing an ultra-high-speed laser beam cladding-residual heat cutting coating, which uses an ultra-high-speed laser beam to clad metal powder onto the surface of a rotating part, and then uses a turning tool, a milling cutter or a grinding wheel to process the cladding layer that still has residual heat, so as to obtain cylindrical, conical, and rotating end face parts with a layer of metal coating on the surface. However, the hardness of the cutting tool used in this patent is relatively low, and the tool movement is simple, so it can only process the metal coating on the surface of rotating parts, and cannot process the ceramic coating on the surface of complex curved parts; in particular, the parts obtained by processing with metal coatings still cannot effectively solve the problem of wear failure in high-temperature corrosion environments. In addition, this patent reduces the cutting force by controlling the temperature of the coating layer to a certain high temperature, but after processing and forming, the metal coating layer will still naturally cool to room temperature and produce certain thermal stress. Therefore, this method is not suitable for ceramic coatings, because the residual thermal stress can easily cause microcracks to appear again in the ceramic coating after processing.

[0007] Patent CN20181044224.2 proposes a heat treatment assisted laser cladding method, which uses a heat treatment furnace for temperature control to extend the grain growth time inside the coating and improve the problem of cracks and pores in the cladding layer caused by rapid cooling and heating of the substrate and the preset layer. However, the coating in this patent is still "pressureless" and naturally cooled and solidified, so the coating is uneven, so subsequent mechanical processing is required to flatten the coating. In addition, this patent only reduces the generation of cracks by adjusting the temperature, which is uncertain, and cracks and pores may still occur, and the coating usually requires subsequent treatment. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a laser deposition-chemical mechanical grinding integrated flexible forming system and method for complex curved surface ceramic coatings. The system and method can significantly improve the wear resistance, high temperature resistance and corrosion resistance of the workpiece material, and efficiently obtain high-quality ceramic coatings.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] In the first aspect, the present invention provides a laser deposition-chemical mechanical grinding integrated flexible forming system for complex curved surface ceramic coatings, comprising a workpiece preheating unit, an electrostatic spraying unit, a laser deposition unit, and a chemical mechanical grinding unit, and is implemented by the following technical solutions:

[0011] A workpiece preheating unit, which is placed on the machine tool body through a heat insulation device and includes a heating module and a temperature measuring module. The heating module heats the workpiece to a set temperature, and the temperature measuring module is used for real-time monitoring of the surface temperature of the workpiece;

[0012] An electrostatic spraying unit, wherein the electrostatic spraying unit sprays statically charged ceramic powder onto the preheated workpiece surface;

[0013] A laser deposition unit, wherein the laser deposition unit melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer;

[0014] The chemical mechanical grinding unit includes a grinding wheel grinding module and a micro-lubrication module. The micro-lubrication module can spray thermally active grinding fluid onto the grinding surface of the grinding wheel and the ceramic coating to reduce interface friction and the hardness of the ceramic material. The grinding wheel grinding module can perform micro-cutting on the surface material of the ceramic coating to remove surface defects.

[0015] The above system first uses a workpiece preheating unit to preheat the workpiece material to a certain temperature, and then uses a high-voltage electrostatic corona charging method to charge the ceramic powder with a certain amount of static electricity. At the same time, with the help of the adiabatic nozzle of the electrostatic spraying unit and the vacuum negative pressure effect of compressed air, the statically charged ceramic powder is continuously sprayed onto the surface of the workpiece material, and then the laser of the laser deposition unit is used to deposit a ceramic coating on the surface of the workpiece material, and the ceramic coating chemical mechanical grinding unit is used to post-process the ceramic coating; that is, the system finally obtains a smooth, dense and surface defect-free ceramic coating through the mutual cooperation and coordination between the workpiece preheating unit, the electrostatic spraying unit, the laser deposition unit and the chemical mechanical grinding unit.

[0016] As a further technical solution, the electrostatic spraying unit, laser deposition unit, and chemical mechanical grinding unit are connected to a multi-degree-of-freedom robotic arm through an indexable fixture and placed on the machine tool body to achieve switching of each unit.

[0017] As a further technical solution, the electrostatic spraying unit includes an electrostatic charging module and a pneumatic spraying module. The electrostatic charging module can charge the ceramic powder in the powder feeder with static electricity, and the pneumatic spraying module sprays the statically charged ceramic powder onto the preheated workpiece surface.

[0018] As a further technical solution, the laser deposition unit includes a gas storage device, an injection device and a laser. The gas storage device can store inert gas. The injection device sprays the inert gas to the focus of the laser spot on the workpiece surface. The laser melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer.

[0019] In a second aspect, the present invention further proposes a method for laser deposition-chemical mechanical grinding integrated forming of a complex curved surface ceramic coating using the laser deposition-chemical mechanical grinding integrated forming system of the complex curved surface ceramic coating, comprising the following steps:

[0020] S1. Surface pretreatment of the workpiece material to be sprayed by removing the oxide layer and cleaning the oil stains;

[0021] S2. The workpiece preheating unit heats the processed workpiece material;

[0022] S3. The electrostatic spraying unit performs high-voltage electrostatic corona charging on the ceramic powder, and sprays the electrostatically charged ceramic powder evenly onto the surface of the workpiece;

[0023] S4. The laser deposition unit melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer;

[0024] S5. The lubrication module sprays the thermally active grinding fluid evenly onto the grinding surface of the grinding wheel and the ceramic coating;

[0025] S6. The grinding wheel grinding module performs efficient and high-quality micro-cutting processing on ceramic coating surface materials.

[0026] As a further technical solution, the heating temperature of the workpiece preheating unit can reach up to 1000°C, and the workpiece surface temperature can be monitored at all times and heated in an inert gas atmosphere.

[0027] As a further technical solution, the ceramic powder is a single TiO 2 Micro powder or Al 2 O 3 Micro powder or 20-60 parts TiO 2 Micro powder and 40-80 parts of Al 2 O 3 A mixture of fine powders.

[0028] As a further technical solution, the laser power used in the laser deposition unit is 1-2 kW, the spot diameter is 1-3 mm, and the scanning speed is 20-200 mm / s;

[0029] As a further technical solution, the selection range of the high-voltage electrostatic voltage of the electrostatic spray unit is 50-60 kV; the selection range of the compressed air flow and pressure of the electrostatic spray unit is 30-60 L / min and 0.3-0.8 MPa respectively.

[0030] As a further technical solution, the thermally active grinding fluid comprises 50-70 wt.% of a fully synthetic grinding fluid, 25-40 wt.% of polyethylene glycol, and 5-10 wt.% of an azo compound or an organic peroxide compound; the flow rate of the thermally active grinding fluid is 10-100 mL / h; the critical grinding depth d c =λ(H / E) 1 / 2 (K c / H) 2 , where λ is approximately equal to 8.7, is the brittle-to-plastic transition factor of the ceramic coating material, H is the hardness of the ceramic coating formed by laser deposition, E is the elastic modulus of the ceramic coating formed by laser deposition, and K c is the fracture toughness of the ceramic coating formed by laser deposition.

[0031] The beneficial effects of the present invention are as follows:

[0032] The laser deposition-chemical mechanical grinding integrated forming system of the complex curved surface ceramic coating of the present invention, the system finally obtains a flat, dense and surface defect-free ceramic coating through the mutual cooperation and coordination between the workpiece preheating unit, the electrostatic spraying unit, the laser deposition unit and the chemical mechanical grinding unit; first, the complex curved surface workpiece is heated by the workpiece preheating unit, and then the ceramic powder is charged with static electricity by the charging effect of high-voltage static electricity, and then the multi-freedom electrostatic spraying unit sprays the ceramic powder evenly onto the surface of the complex curved surface workpiece, and at the same time, the multi-freedom high-energy laser beam is used to scan the material surface, and the ceramic powder is induced to melt and form a ceramic coating with metallurgical bonding with the surface of the complex curved surface workpiece material. Then, the multi-freedom chemical mechanical grinding of the ceramic coating is carried out, and the thermally active grinding fluid is used to induce the surface material of the ceramic coating to react chemically to form a soft layer, and the ultra-fine diamond abrasive grinding wheel processes the workpiece surface by micro-cutting to remove the surface defects such as cracks, holes and fragmentation, and finally achieves high-quality and efficient removal of the surface material of the ceramic coating, and finally obtains a flat, dense and surface defect-free ceramic coating. The workpiece preheating unit is placed on the machine tool body to preheat the workpiece to a certain temperature. The electrostatic spraying unit, laser deposition unit, and chemical mechanical grinding unit are connected to a multi-degree-of-freedom robotic arm through an indexable fixture and placed on the machine tool body to realize switching of each unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0035] Figure 2 is a heating state diagram of the workpiece preheating unit of the present invention;

[0036] Figure 3 is a schematic diagram of a ceramic powder electrostatic spraying unit of the present invention;

[0037] Figure 4 is a schematic diagram of a laser deposition unit of the present invention;

[0038] Figure 5 is a schematic diagram of a ceramic coating chemical mechanical grinding unit of the present invention;

[0039] Among them, 1-machine tool body, 2-workpiece preheating unit, 3-complex curved workpiece, 4-micro-lubrication device, 5-thermally active grinding droplets, 6-indexable fixture, 7-gas storage device, 8-infrared thermal imager, 9-multi-degree-of-freedom robotic arm, 10-powder bin, 11-laser, 12-jet device, 13-powder spraying device, 14-diamond abrasive grinding wheel, 15-high-voltage electrostatic generating device. DETAILED DESCRIPTION

[0040] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0042] At present, in the existing technology, advanced alloy materials such as titanium alloy, stainless steel and nickel-based high-temperature alloy have high strength, excellent high temperature resistance and good corrosion resistance, so they are widely used in aviation, aerospace, medical equipment and chemical equipment. However, the hardness of the above alloy materials is relatively low, resulting in poor resistance to mechanical removal, especially the material's ability to resist abrasive wear and abrasive-corrosion wear in high temperature and corrosive environments. Compared with metal alloys, ceramics have significantly higher hardness and excellent wear resistance, high temperature resistance and corrosion resistance. Therefore, depositing ceramic materials on the surface of metal alloys to form a dense and surface defect-free ceramic coating can effectively improve the ability of alloy materials to resist deformation and failure caused by external high mechanical loads in extreme service environments, and obtain high wear resistance and corrosion resistance. It can be seen that the application of ceramic coatings can greatly reduce the loss of parts caused by high-temperature mechanical wear and corrosive wear. The field of performance optimization of advanced alloy materials is focusing on the theoretical and technical research of obtaining high-performance alloy materials by modifying the alloy surface with ceramic coatings. The ceramic coating modification strategy can not only retain the advantages of lightweight and high strength of alloy materials, but also effectively solve the failure problems caused by high mechanical loads or corrosion in extreme environments of alloys, further expanding the application scope of advanced alloy materials.

[0043] Ceramic powders commonly used to prepare ceramic coatings involve titanium dioxide, aluminum oxide or composite powders of the two. Ceramic powders have extremely high melting points (usually greater than 1600°C), so high-energy beam laser deposition methods are widely used to prepare wear-resistant ceramic coatings on the surface of metal plates. The metal matrix and ceramic powder are melted simultaneously by the rapid heating effect of a high-power laser beam to form a metallurgical bonding layer of ceramic and metal, thereby improving the wear resistance of the product. Laser-deposited ceramic coatings have the advantages of high bonding strength, good coating density, and high controllability. However, the temperature gradient effect of rapid heating and cooling during laser deposition can cause microcracks between the substrate and the coating and inside the coating. At the same time, when the ceramic powder melts rapidly, the residual gas between the powders cannot be quickly discharged, which leads to residual pores in the coating, ultimately affecting the mechanical properties of the coating. In addition, the surface of the laser-deposited ceramic coating will have defects such as cracks and holes, and the ceramic coating solidified by "pressureless" natural cooling is uneven, so subsequent mechanical processing is required to remove surface defects and flatten the coating. The ceramic coating prepared by laser deposition has the characteristics of high hardness and low fracture toughness, as well as defects such as microcracks and holes on the surface. Therefore, the subsequent mechanical processing needs to be relatively "gentle". Excessive mechanical force will further induce the expansion of surface cracks, which will then extend into the interior of the coating, ultimately leading to the failure of the protective performance of the entire coating. Therefore, a ductile domain grinding technology that controls the maximum undeformed cutting thickness to be less than the critical grinding depth for cracks in the coating material is a key strategy for efficiently obtaining high-quality ceramic coatings. Based on this, the present embodiment discloses a laser deposition-chemical mechanical grinding integrated flexible forming system and method for complex curved surface ceramic coatings; the system and method can significantly improve the wear resistance, high temperature resistance and corrosion resistance of the workpiece material, and efficiently obtain high-quality ceramic coatings.

[0044] Specifically, the laser deposition-chemical mechanical grinding integrated flexible forming system for complex curved surface ceramic coatings proposed in this embodiment includes a workpiece preheating unit, an electrostatic spraying unit, a laser deposition unit, and a chemical mechanical grinding unit; the details are as follows:

[0045] A workpiece preheating unit, which is arranged on the machine tool body through a heat insulation device, comprises a heating module and a temperature measuring module, wherein the heating module heats the workpiece to a set temperature, and the temperature measuring module is used for real-time monitoring of the surface temperature of the workpiece; the alloy material is heated to a certain temperature by means of the heating effect of the resistance wire heating device, so that the temperature gradient of the ceramic powder during the laser cladding process can be reduced, thereby effectively reducing thermal stress and preventing microcracks from being generated between the substrate and the ceramic coating and inside the ceramic coating;

[0046] An electrostatic spraying unit, wherein the electrostatic spraying unit sprays statically charged ceramic powder onto the preheated workpiece surface; a certain amount of static charge is applied to the ceramic powder by means of high-voltage electrostatic corona charging, so that the ceramic powder is evenly adsorbed onto the non-charged workpiece surface according to the principle of "opposites attract";

[0047] A laser deposition unit, wherein the laser deposition unit melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer; the laser is used to melt the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer, and the high-temperature melting characteristics of the laser can not only fully melt the ceramic powder, but also accelerate the recrystallization process between the ceramic powders and the high-temperature metallurgical reaction with the surface of the workpiece material, thereby forming a high-strength and high-density ceramic layer;

[0048] The chemical mechanical grinding unit includes a grinding wheel grinding module and a micro-lubrication module. The micro-lubrication module can spray thermally active grinding fluid onto the grinding surface of the grinding wheel and the ceramic coating to reduce interface friction and the hardness of the ceramic material. The grinding wheel grinding module can perform micro-cutting on the surface material of the ceramic coating to remove surface defects.

[0049] The laser deposition-chemical mechanical grinding integrated flexible forming system of the complex curved surface ceramic coating proposed by the present invention reduces the temperature difference between the ceramic melt and the workpiece material during laser deposition, reduces thermal stress, and inhibits the formation of microcracks between the substrate and the coating and inside the coating by means of the heating effect of the resistance wire heating device 2 on the workpiece material. Then, through the laser melting effect of the laser 11, the ceramic powder is fully melted, the melting recrystallization of the ceramic powder on the surface of the workpiece material and the high-temperature metallurgical reaction with the metal elements are accelerated to form a dense ceramic coating. Finally, the thermally active grinding fluid is sprayed onto the grinding surface of the grinding wheel and the ceramic coating to form a softening layer on the surface, thereby achieving the effect of reducing the interface friction and the hardness of the ceramic material. Then, the ceramic coating is micro-cut by the diamond abrasive grinding wheel to remove the microcracks and hole defects on the surface of the ceramic coating, and a uniform, dense, hole-free and crack-free high-wear-resistant ceramic coating is obtained, which ultimately improves the wear resistance of the advanced alloy material. That is, the system realizes the forming of complex curved ceramic coatings through the mutual coordination and cooperation among the above-mentioned workpiece preheating unit, electrostatic spraying unit, laser deposition unit and chemical mechanical grinding unit, and finally obtains a smooth, dense and surface defect-free ceramic coating.

[0050] Furthermore, the electrostatic spraying unit, laser deposition unit, and chemical mechanical grinding unit are connected to a multi-degree-of-freedom robotic arm through an indexable fixture and placed on the machine tool body to achieve switching of each unit, such as Figure 1As shown, it includes a machine tool body 1, on which a resistance wire heating device 2 and a multi-degree-of-freedom robot arm 9 are arranged. The multi-degree-of-freedom robot arm 9 can realize the movement of the X-axis, Y-axis, and Z-axis and the rotation of the A-axis and C-axis. The end of the multi-degree-of-freedom robot arm 9 is equipped with an indexable fixture 6, and the electrostatic spraying unit, the laser deposition unit, and the chemical mechanical grinding unit are installed on the indexable fixture 6.

[0051] Furthermore, the electrostatic spraying unit includes a powder bin 10, an electrostatic charging module and a pneumatic spraying module. The electrostatic charging module can charge the ceramic powder in the powder feeder with static electricity, and the pneumatic spraying module sprays the statically charged ceramic powder onto the preheated workpiece surface. The electrostatic charging module charges the ceramic powder using high-voltage electrostatic corona charging. Subsequently, the pneumatic spraying module continuously sprays the charged ceramic powder onto the workpiece surface through the vacuum negative pressure effect generated by the adiabatic nozzle and compressed air. Figure 1 The pneumatic spraying module is a powder spraying device 13; the electrostatic charging module is a high-voltage electrostatic generating device 15; the high-voltage electrostatic generating device 15 can charge the ceramic powder in the powder bin 10 with static electricity, and the powder bin 10 can ensure a stable supply of ceramic powder in the powder spraying device 13; the ceramic powder is charged with a certain amount of static charge by high-voltage electrostatic corona charging, so that the ceramic powder can be evenly adsorbed onto the surface of the workpiece without charge according to the principle of "opposites attract".

[0052] Furthermore, the laser deposition unit includes a gas storage device 7, an injection device 12 and a laser 11. The gas storage device 7 can store inert gas. The injection device 12 sprays the inert gas to the focus of the laser spot on the surface of the workpiece. The laser 11 melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer. The gas storage device 7 is installed on one side of the machine tool body 1. In this embodiment, it is installed on the right side of the machine tool body 1. The high-temperature melting characteristics of the laser in the laser deposition unit can not only fully melt the ceramic powder, but also accelerate the recrystallization process between the ceramic powders and the high-temperature metallurgical reaction with the surface of the workpiece material to form a high-strength and high-density ceramic layer.

[0053] Furthermore, in the present embodiment, the workpiece preheating unit adopts a resistance wire heating device 2, on which there is a workpiece material 3, and an infrared thermal imager 8 and a micro-lubrication device 4 are respectively provided on the left and right sides of the workpiece material 3, wherein the micro-lubrication device 4 atomizes a certain amount of thermally active grinding fluid into small droplets and then sprays them onto the grinding surface of the grinding wheel and the ceramic coating; the infrared thermal imager 8 can receive infrared radiation emitted by the object and convert it into an electrical signal, thereby realizing real-time monitoring of the workpiece surface temperature, that is, the heating module in the present embodiment heats the workpiece to a specific temperature by means of resistance wire heating, and at the same time, the temperature measuring module adopts an infrared thermal imager to monitor the temperature change of the workpiece surface in real time; the heating temperature of the workpiece preheating unit can reach up to 1000°C, and can realize real-time monitoring of the workpiece surface temperature and heating under an inert gas atmosphere.

[0054] Specifically, first, the workpiece preheating unit preheats the workpiece material to a certain temperature by means of resistance wire heating, which can reduce the temperature gradient of the ceramic powder during the laser cladding process, thereby effectively reducing thermal stress and preventing microcracks between the substrate and the ceramic coating and inside the ceramic coating. Subsequently, the charging module in the ceramic powder electrostatic spraying unit is used to charge the ceramic powder with a certain amount of charge, and then the ceramic powder is evenly sprayed onto the surface of the workpiece material with the help of an adiabatic nozzle. Next, the high-temperature melting effect of the laser is used to fully melt the ceramic powder, accelerate the recrystallization effect between the ceramic powder and the high-temperature metallurgical reaction with the surface of the workpiece material, and form a high-strength and high-density ceramic layer. Finally, the thermally active grinding fluid is sprayed onto the grinding surface of the grinding wheel and the ceramic coating to reduce the interface friction and the hardness of the ceramic material. The diamond abrasive grinding wheel performs micro-cutting on the ceramic coating, achieving a high material removal rate while reducing the processing damage caused by the removal of a single high mechanical stress, and finally obtaining a smooth, dense and surface defect-free ceramic coating with high quality and efficiency.

[0055] As a further technical solution, the heating temperature of the resistance wire heating device 2 can reach up to 1000° C. at most, and the workpiece can be heated in an inert gas atmosphere.

[0056] As a further technical solution, the ceramic powder is a single TiO 2 Micro powder or Al 2 O 3 Micro powder or 20-60 parts TiO 2 Micro powder and 40-80 parts of Al 2 O 3 As a further technical solution, the TiO 2 and Al 2 O 3 The powder particle size is 5-10 μm;

[0057] As a further technical solution, the powder spraying rate of the powder spraying unit 13 is 5-10 g / min.

[0058] As a further technical solution, the power of the laser 11 used in the laser deposition unit is 1-2 kW, the spot diameter is 1-3 mm, and the scanning speed is 20-200 mm / s.

[0059] As a further technical solution, the grinding wheel 14 of the grinding module is a diamond abrasive grinding wheel, the abrasive particle size is 1-20 μm, and the bonding agent is a metal bonding agent or a resin bonding agent.

[0060] As a further technical solution, the thermally active grinding fluid comprises 50-70 wt.% of fully synthetic grinding fluid, 25-40 wt.% of polyethylene glycol, and 5-10 wt.% of azo compounds or organic peroxide compounds.

[0061] The processing method corresponding to the laser deposition-chemical mechanical grinding integrated flexible forming system of the above-mentioned complex curved surface ceramic coating is as follows:

[0062] S1. Surface pretreatment of the workpiece material to be sprayed by removing the oxide layer and cleaning the oil stains;

[0063] S2. The workpiece preheating unit heats the processed workpiece material;

[0064] S3. The electrostatic spraying unit performs high-voltage electrostatic corona charging on the ceramic powder, and sprays the electrostatically charged ceramic powder evenly onto the surface of the workpiece;

[0065] S4. The laser deposition unit melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer;

[0066] S5. The lubrication module sprays the thermally active grinding fluid evenly onto the grinding surface of the grinding wheel and the ceramic coating;

[0067] S6. The grinding wheel grinding module performs efficient and high-quality micro-cutting processing on ceramic coating surface materials.

[0068] Furthermore, the flow rate of the thermally active grinding fluid is 10 to 100 mL / h; the critical grinding depth d c =λ(H / E) 1 / 2 (K c / H) 2 , where λ is approximately equal to 8.7, is the brittle-to-plastic transition factor of the ceramic coating material, H is the hardness of the ceramic coating formed by laser deposition, E is the elastic modulus of the ceramic coating formed by laser deposition, and K c is the fracture toughness of the ceramic coating formed by laser deposition.

[0069] A further more specific method is as follows, comprising the following steps:

[0070] Step 1: TiO 2 Powder or Al 2 O 3 The powder or the mixed ceramic powder of the two is put into the powder bin of the electrostatic spraying unit; the specific process is as follows: weigh a single TiO 2 Micro powder or Al 2 O 3 Micro powder or 20-60 parts TiO 2 Micro powder and 40-80 parts of Al 2 O 3 The mixture of micro powder is then placed into the powder bin of the electrostatic spraying unit;

[0071] Step 2: Surface pretreatment of the workpiece material to be sprayed by removing the oxide layer and cleaning the oil stains;

[0072] Step 3: Set the heating parameters of the heating module to heat the workpiece material processed in step 2;

[0073] Step 4: Set the working parameters of the electrostatic spraying unit, start the high-voltage electrostatic generator, and perform high-voltage electrostatic corona charging on the ceramic powder;

[0074] Step 5: Adjust the inclination angle of the insulation nozzle and start the compressed air device to evenly spray the statically charged ceramic powder onto the workpiece surface;

[0075] Step 6: Setting the working parameters of the laser deposition unit, including laser power, scanning speed, spot diameter, etc., which need to be adjusted according to the specific material properties; the specific process is as follows: the laser power of the laser deposition unit is 1-2kW, the spot diameter is 1-3mm, and the scanning speed is 20-200mm / s;

[0076] Step 7: Setting the working parameters of the micro-lubrication module, spraying the thermally active grinding fluid evenly onto the grinding surface of the grinding wheel and the ceramic coating; the specific process is as follows: the thermally active grinding fluid comprises 50-70wt.% of a fully synthetic grinding fluid, 25-40wt.% of polyethylene glycol, and 5-10wt.% of an azo compound or an organic peroxide compound, and the flow rate of the thermally active grinding fluid is 10-100mL / h;

[0077] Step 8: Set the parameters of the grinding module to perform efficient and high-quality micro-cutting processing on the ceramic coating surface material.

[0078] The chemical mechanical grinding in the present invention is a grinding process for hard, brittle and difficult-to-process ceramic materials. It can effectively achieve high-precision, large-area surface flattening of ceramic materials through the synergistic effect of chemical modification and mechanical removal. In chemical mechanical grinding, the grinding fluid first reacts with the surface of the hard and brittle ceramic material to induce the formation of a softened layer on the surface of the ceramic material, and then the fixed abrasive removes the softened layer through mechanical micro-cutting. It can be seen that the chemical mechanical ductile domain grinding process based on the chemical-mechanical synergistic effect is expected to remove surface defects of ceramic coatings with high efficiency and high quality, while avoiding the introduction of further damage defects such as cracks.

[0079] The laser deposition-chemical mechanical grinding integrated flexible forming system of the complex curved surface ceramic coating proposed in this embodiment first heats the alloy material to a certain temperature by means of the heating effect of the resistance wire heating device, so that the temperature gradient of the ceramic powder during the laser cladding process can be reduced, thereby effectively reducing the thermal stress and preventing the generation of microcracks between the substrate and the ceramic coating and inside the ceramic coating. In particular, the ceramic powder is charged with a certain amount of static charge by means of high-voltage electrostatic corona charging, so that the ceramic powder can be uniformly adsorbed onto the surface of the workpiece without charge according to the principle of "opposites attract". At the same time, the laser is used to melt the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer. The high-temperature melting characteristics of the laser can not only fully melt the ceramic powder, but also accelerate the recrystallization process between the ceramic powder and the high-temperature metallurgical reaction with the surface of the workpiece material to form a high-strength and high-density ceramic layer. Finally, the thermally active grinding fluid is sprayed onto the grinding surface of the ceramic coating and the grinding wheel to achieve the effect of reducing the interface friction and the hardness of the ceramic material, and finally obtain a high-quality ceramic coating.

[0080] Therefore, the manufacturing method proposed in this embodiment, which is suitable for high-quality and high-efficiency processing of ceramic coatings on complex curved surface parts, can effectively remove defects in the ceramic coating without further introducing new defects.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A laser deposition-chemical mechanical grinding integrated forming system for complex curved surface ceramic coatings, characterized in that: include: A workpiece preheating unit, which is placed on the machine tool body through a heat insulation device and includes a heating module and a temperature measuring module. The heating module heats the workpiece to a set temperature, and the temperature measuring module is used for real-time monitoring of the surface temperature of the workpiece; An electrostatic spraying unit, wherein the electrostatic spraying unit sprays statically charged ceramic powder onto the preheated workpiece surface; A laser deposition unit, wherein the laser deposition unit melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer; The chemical mechanical grinding unit includes a grinding wheel grinding module and a micro-lubrication module. The micro-lubrication module can spray thermally active grinding fluid onto the grinding surface of the grinding wheel and the ceramic coating to reduce interface friction and the hardness of the ceramic material. The grinding wheel grinding module can perform micro-cutting on the surface material of the ceramic coating to remove surface defects.

2. The laser deposition-chemical mechanical grinding integrated forming system for complex curved surface ceramic coatings according to claim 1, characterized in that: The electrostatic spraying unit, laser deposition unit and chemical mechanical grinding unit are connected to a multi-degree-of-freedom robotic arm through an indexable fixture and are placed on the machine tool body to achieve switching of each unit.

3. The laser deposition-chemical mechanical grinding integrated forming system for complex curved surface ceramic coatings according to claim 1, characterized in that: The electrostatic spraying unit comprises an electrostatic charging module and a pneumatic spraying module. The electrostatic charging module can charge the ceramic powder in the powder feeder with static electricity, and the pneumatic spraying module sprays the statically charged ceramic powder onto the preheated workpiece surface.

4. The laser deposition-chemical mechanical grinding integrated forming system for complex curved surface ceramic coatings according to claim 1, characterized in that: The laser deposition unit includes a gas storage device, an injection device and a laser. The gas storage device can store inert gas. The injection device sprays the inert gas to the focus of the laser spot on the workpiece surface. The laser melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer.

5. A method for laser deposition-chemical mechanical grinding integrated forming of a ceramic coating with a complex curved surface using a laser deposition-chemical mechanical grinding integrated forming system for a ceramic coating with a complex curved surface as described in any one of claims 1 to 4, characterized in that: The steps include: S1. Surface pretreatment of the workpiece material to be sprayed to remove the oxide layer and clean the oil stains; S2. The workpiece preheating unit heats the processed workpiece material; S3. The electrostatic spraying unit performs high-voltage electrostatic corona charging on the ceramic powder, and sprays the electrostatically charged ceramic powder evenly onto the surface of the workpiece; S4. The laser deposition unit melts the ceramic powder layer covering the surface of the preheated workpiece to form a molten layer; S5. The lubrication module sprays the thermally active grinding fluid evenly onto the grinding surface of the grinding wheel and the ceramic coating; S6. The grinding wheel grinding module performs efficient and high-quality micro-cutting processing on ceramic coating surface materials.

6. The laser deposition-chemical mechanical grinding integrated forming method of complex curved surface ceramic coating according to claim 5, characterized in that: The heating temperature of the workpiece preheating unit can reach up to 1000°C, and it can realize real-time monitoring of the workpiece surface temperature and heating under an inert gas atmosphere.

7. The laser deposition-chemical mechanical grinding integrated forming method of complex curved surface ceramic coating according to claim 5, characterized in that: The ceramic powder is a single TiO2 micropowder or Al2O3 micropowder or a mixture of 20 to 60 parts of TiO2 micropowder and 40 to 80 parts of Al2O3 micropowder.

8. The laser deposition-chemical mechanical grinding integrated forming method of complex curved surface ceramic coating according to claim 5, characterized in that: The laser power used in the laser deposition unit is 1-2 kW, the spot diameter is 1-3 mm, and the scanning speed is 20-200 mm / s.

9. The laser deposition-chemical mechanical grinding integrated forming method of complex curved surface ceramic coating according to claim 5, characterized in that: The selection range of the high-voltage electrostatic voltage of the electrostatic spray unit is 50-60 kV; the selection range of the compressed air flow and pressure of the electrostatic spray unit is 30-60 L / min and 0.3-0.8 MPa respectively.

10. The laser deposition-chemical mechanical grinding integrated forming method of complex curved surface ceramic coating according to claim 5, characterized in that: The thermally active grinding fluid comprises 50-70 wt.% of a fully synthetic grinding fluid, 25-40 wt.% of polyethylene glycol, and 5-10 wt.% of an azo compound or an organic peroxide compound; the flow rate of the thermally active grinding fluid is 10-100 mL / h; the critical grinding depth d c =λ(H / E) 1 / 2 (K c / H) 2 , where λ is approximately equal to 8.7, is the brittle-to-plastic transition factor of the ceramic coating material, H is the hardness of the ceramic coating formed by laser deposition, E is the elastic modulus of the ceramic coating formed by laser deposition, and K c is the fracture toughness of the ceramic coating formed by laser deposition.

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