A laser-laser combination forming method for group hole complex structure

Abstract

The present application relates to the technical field of additive manufacturing, and discloses a laser-laser additive and subtractive combined forming method for group-hole complex structures, which is used for manufacturing a nozzle head of a space engine by using a pulse laser selective melting device, and is used for performing group punching on the fuel nozzle by using a pulse laser, so that the nozzle head part of the space engine becomes an integral whole, and the punching efficiency is improved, and the manufacturing time and cost are greatly shortened. The present application is simple to operate, basically does not need manual operation, shortens the processing time, saves manpower, greatly improves the processing efficiency, has good forming quality, and has product quality superior to that of traditional mechanical processing.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a laser-laser additive-subtractive combination forming method for complex structures with multiple holes. Background Technology

[0002] The nozzle head is one of the core components of aerospace engines, responsible for mixing fuel and sending it into the combustion chamber. Traditional liquid aerospace engine nozzle heads are mostly made of Inconel 718 alloy, which can operate in environments up to 700°C. They are generally composed of more than 200 parts, including more than 100 fuel injectors, base plates, and front panels. Each nozzle of the engine has 12 centrifugal holes with a diameter of 1.05 mm for fuel mixing.

[0003] Currently, the manufacturing of aerospace engine nozzles primarily relies on casting followed by machine tool machining. This method is not only inefficient but also demands extremely high precision from the machine tools, resulting in low yield and pass rates. The numerous mechanical connections within the aerospace engine nozzle structure increase the overall weight of the workpiece and reduce the strength of the joints. Machining the centrifugal holes requires drilling on curved surfaces with high precision requirements, leading to long processing times and significant challenges. Traditional manufacturing methods are not only time-consuming and labor-intensive but also reduce the strength of joints in some areas, impacting aerospace engine performance. Existing methods for machining centrifugal holes on fuel injectors mainly involve mechanical drilling. The parts to be machined are made of hard nickel-based superalloys, exhibiting high hardness and causing significant wear on the drill bit, resulting in long drilling times. Drilling on curved surfaces requires high precision and demands highly skilled operators, leading to low yields and long processing cycles.

[0004] Laser drilling uses thermal energy to melt and evaporate the part to be drilled, forming a hole. It has no requirements on the material being processed or the surface being processed. Multiple holes can be processed at once, and the processing time is fast, typically completing multiple holes in just a few seconds. Due to the small diameter of the laser spot, the processing precision is also high, making it suitable for the drilling requirements of fuel injectors.

[0005] To address the aforementioned problems, Chinese invention patent CN202111421838.4 proposes a method for forming liquid aerospace engine injection disks using laser powder bed melting. This technology can directly form injection disks for liquid aerospace engines. However, the microstructure and grain size of the formed metal by continuous laser are uneven, the boundaries of the molten pool are obvious, and the reinforcing particles of the material are prone to agglomeration during manufacturing, thus affecting the strengthening effect. In addition, Chinese invention patent CN116393847A proposes a two-stage laser drilling method, setting two different parameters for drilling ceramic coatings and metal inner layers respectively. However, it ignores the fact that the drilling is carried out in air, and most existing Chinese patents process directly in air, resulting in thicker recast layers of micropores, poor surface quality, and more particles deposited at the edges of the micropores, affecting the overall drilling quality. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a laser-laser additive-subtractive combination forming method for complex multi-hole structures. This method utilizes pulsed laser selective melting equipment to manufacture aerospace engine nozzle heads, and employs pulsed laser drilling to perform clustered drilling on the fuel injector, thus integrating the aerospace engine nozzle head parts into a single unit and significantly improving drilling efficiency. This method greatly reduces manufacturing time and costs. The invention is simple to operate, requires virtually no manual intervention, shortens processing time, saves manpower, greatly improves processing efficiency, and produces high-quality products superior to those from traditional machining processes.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A laser-laser augmentation-subtraction combination forming method for complex structures with multiple holes includes the following steps:

[0009] The mixed powder was prepared and dried. Then, the three-dimensional structural data was collected and a model was built. The three-dimensional data was then imported into a pulsed laser selective melting device to generate a two-dimensional laser scanning path.

[0010] Install the substrate, load the dried mixed powder into the forming chamber of the pulsed laser selective melting equipment, and pre-lay the first layer of powder;

[0011] The pulsed laser selective melting equipment generates process parameters and printing trajectory. First, the forming chamber is evacuated, then protective argon gas is injected, and the forming laser is turned on to complete nozzle manufacturing.

[0012] Turn off the forming laser and turn on the drilling laser. Align the structure with the laser focus, set the laser drilling parameters, evacuate the forming chamber, and then perform the drilling process. After the process is completed, separate the processed structure from the substrate.

[0013] As a further implementation method, nickel-based alloy powder particles with a particle size of 15-53 μm are mixed with TiC to obtain a mixed powder.

[0014] As a further implementation method, after sieving out impurities and ball-milled particles from the mixed powder, it is spread evenly and dried in a vacuum drying oven with a vacuum degree ≤1.0×10⁻⁶. -1 Pa.

[0015] As a further implementation method, before installing the substrate, the forming chamber and powder chamber in the pulsed laser selective melting equipment are cleaned. When installing the substrate, the substrate is placed on the working platform and fixed so that the upper edge of the substrate is aligned with the working platform in the forming chamber and the holes are aligned.

[0016] As a further implementation, the height of the working platform is adjusted so that the platform surface moves downward to the focal plane position, and the position of the scraper is adjusted so that the gap between the scraper and the substrate is zero.

[0017] As a further implementation method, a first layer of powder is pre-laid using a flat method, with a powder layer thickness of 45-50μm, laser power of 180-200W, exposure time of 200-220μs, dot pitch of 25-30μm, row pitch of 60-65μm, scanning method of interlayer rotation of 90°, substrate preheating temperature of 70-80℃, substrate material of 316L, squeegee material of rubber, and laser spot diameter of 60-70μm.

[0018] As a further implementation method, after leveling the substrate and laying the first layer of mixed powder, the chamber is first evacuated to a vacuum, and then argon gas is injected as a protective gas. The argon gas pressure is maintained at 8-12 MPa, and the oxygen content in the chamber is kept below 0.0001%.

[0019] As a further implementation method, after the manufacturing is completed and the temperature inside the molding chamber drops to the same level as the room temperature, the work platform is raised, the glove box door is opened, the residual powder in the structure is cleaned, and the glove box door is closed after the powder is cleaned.

[0020] As a further implementation, the pulsed laser selective melting device is connected to a vacuum device to remove the argon gas in the forming chamber, so that the forming chamber is in a vacuum state before drilling is performed.

[0021] As a further implementation, the laser drilling parameters are as follows: helical scanning mode, Z-axis feed rate of 20μm, number of scans of 8-10, laser energy of 35-40μJ, repetition frequency of 120-125KHz, scan rate of 90-100mm / s, laser wavelength of 1000-1030nm, pulse width of 270-276fs, and Z-axis feed of 30 times.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. In the process of laser powder bed melting, the present invention uses pulsed laser mode. The continuous impact and stirring effect of pulsed laser on the molten pool can make the reinforced ceramic particles more uniformly distributed in the Inconel718 alloy matrix and prevent agglomeration. In addition, the stirring of the molten pool by pulsed laser makes the dendrite size more uniform and reduces the layering phenomenon.

[0024] 2. When drilling a workpiece, the present invention uses a vacuum pump to remove the argon gas from the forming chamber, making the forming chamber a vacuum state. This results in a thinner recast layer for the microholes and fewer particles deposited at the edges of the microholes, thus improving the overall drilling quality. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0026] Figure 1 This is a flowchart of a laser-laser addition and subtraction combination forming method for complex structures with multiple holes, as described in this embodiment of the invention.

[0027] Figure 2 It refers to the distribution of ceramic reinforcing particles in the molten pool of a continuous laser powder bed melt;

[0028] Figure 3 This describes the distribution of ceramic reinforcing particles in the molten pool of the pulsed laser powder bed melting process in this embodiment of the invention.

[0029] Figure 4 These are schematic diagrams of pulsed laser selective melting and laser drilling in embodiments of the present invention.

[0030] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0031] Among them: 1. Forming laser, 2. Drilling laser, 3. Beam splitter, 4. Galvanometer, 5. Concentrator, 6. Lifting platform, 7. Forming chamber, 8. Powder chamber, 9. Argon gas, 10. Scraper. Detailed Implementation

[0032] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] Example 1

[0034] In a typical embodiment of the present invention, reference is made to Figures 1-4As shown, a laser-laser augmentation-subtraction combination forming method for complex hole structures includes the following steps:

[0035] Step 1: Powder Mixing

[0036] 1.1) Nickel-based alloy (Inconel 718) powder particles with a particle size of 15-53μm were used. Agate ball mill jars were selected, with a maximum mixing mass of 250g per jar, a ball-to-powder ratio of 1:5, and a TiC mass fraction of 1%. 247.5g of Inconel 718 alloy and 2.5g of TiC powder were weighed in a precision balance each time to ensure thorough and uniform mixing.

[0037] 1.2) Powder mixing was performed using a ball mill, specifically an adjustable oscillating planetary ball mill, with the following parameters: speed 50Hz, switching time 20min, and total milling time 2h.

[0038] Step 2: Powder Preparation

[0039] 2.1) Filter the mixed Inconel 718 / TiC powder particles twice using a 200-mesh filter sieve to remove large impurities and ball-milled particles.

[0040] 2.2) Place the sieved powder into a ceramic tray and spread it to a thickness of 1 cm. Place it in a vacuum drying oven and set the temperature to 100℃. The drying time is 8 hours. The drying oven is then evacuated to a vacuum level of ≤1.0×10-1 Pa to remove any moisture that may be contained in the powder.

[0041] It should be noted that during the above operating procedures, operators must wear protective gloves, anti-static safety shoes, protective face shields, and anti-static wrist straps.

[0042] Step 3: Design and Modeling

[0043] 3.1) First, collect the three-dimensional coordinate data of the aerospace engine nozzle head, and then use three-dimensional modeling software such as SolidWorks and UG to build the nozzle head model.

[0044] 3.2) Use Slic3r or Simplify3D to generate an STL file from the nozzle head model to generate two-dimensional slice data, and import it into the pulsed laser selective melting device to generate a two-dimensional laser scanning path.

[0045] like Figure 4As shown, the bottom of the housing (forming chamber) of the laser additive manufacturing equipment is provided with a forming chamber 7 and a powder chamber 8. A scraper 10 is horizontally slidable inside the housing. The equipment is equipped with a forming laser 1 and a drilling laser 2. The laser is guided by a beam splitter 3, a galvanometer 4, and a focusing lens 5. The side wall of the housing is used for vacuuming and argon gas injection 9. A lifting platform is provided at the bottom of the forming chamber 7 and the powder chamber 8.

[0046] Step 4: Preparations before operating the laser additive manufacturing equipment

[0047] 4.1) Clean the molding chamber and powder chamber. After vacuuming out the impurities and powder from the molding chamber and powder chamber, wipe the camera lens and the sealing ring of the molding chamber door with a clean cloth dipped in anhydrous ethanol. Wipe the molding box gloves and safety glass door with a clean cloth dipped in anhydrous ethanol to ensure that the equipment is clean and free of other impurities and powder.

[0048] 4.2) Install the substrate: Place the substrate on the work platform (the lifting platform of the molding chamber) and fix it so that the upper edge of the substrate is aligned with the top surface inside the molding chamber and the holes are aligned.

[0049] 4.3) Install the scraper: Adjust the height of the work platform (lifting platform) so that the platform surface moves downward to the focal plane position, and adjust the scraper position so that the gap between the scraper and the substrate is zero.

[0050] 4.4) Further, the powder from the drying chamber in step two is loaded into the molding chamber, and the data from step three is imported into the computer of the pulsed laser powder bed melting equipment, so that the computer generates the laser scanning path.

[0051] 4.5) Pre-lay the first layer of powder to further ensure that the substrate is in a horizontal position.

[0052] Step 5: Generate process parameters and print path

[0053] 5.1) The process parameters for laser forming include powder layer thickness, laser power, exposure time, dot pitch, row pitch, scanning method, substrate preheating temperature, substrate material, squeegee material, laser spot diameter, and powder spreading method.

[0054] 5.2) The specific process parameters are as follows: powder layer thickness 50μm, laser power 200W, exposure time 220μs, dot pitch 30μm, row pitch 65μm, scanning method is interlayer rotation 90°, substrate preheating temperature is 80℃, substrate material is 316L, squeegee material is rubber, laser spot diameter is 70μm, and powder spreading method is flat spreading.

[0055] 5.3) Gas washing: After leveling the substrate and laying the first layer of powder, first evacuate the chamber to a vacuum, then inject protective argon gas. The argon gas pressure is maintained at 8-12 MPa, and the oxygen content in the chamber is kept below 0.0001%.

[0056] 5.4) Start the machine, turn on the forming laser, and begin manufacturing the nozzle head using pulsed laser. After manufacturing is complete and the temperature inside the forming chamber has dropped to room temperature, raise the platform, open the glove box door, and clean the residual powder from the nozzle head from the glove box. After the powder is cleaned, close the glove box door. Figure 2 , Figure 3 It is known that ceramic reinforcing particles with smaller particle sizes are prone to agglomeration. This agglomeration phenomenon cannot be eliminated in continuous laser powder bed melting. However, pulsed laser powder bed melting can have a continuous impact and stirring effect on the molten pool, which can disperse the agglomerated particles in the molten pool, make the ceramic particles uniformly dispersed, and further enhance the strengthening effect.

[0057] Step 6: Calibrate the drilling position

[0058] 6.1) Turn off the forming laser and turn on the drilling laser, aligning the central axis of the nozzle head with the center line of the laser.

[0059] 6.2) Adjust the position of the laser head so that the laser spot coincides with the relative position of the fuel injector, ensuring that the initial laser focus is on the upper surface of the nozzle head.

[0060] 6.3) Turn on the vacuum equipment to remove the argon gas in the molding chamber, so that the molding chamber is in a vacuum state.

[0061] Step 7: Set laser drilling parameters

[0062] 7.1) The process parameters include: scanning mode, Z-axis feed rate, number of scans, laser energy, repetition frequency, scanning speed, laser wavelength, pulse width, and number of feeds.

[0063] 7.2) The specific parameters are as follows: the scanning mode is helical scanning, the Z-axis feed is 20μm, the number of scans is 10, the laser energy is 40μJ, the repetition frequency is 125KHz, the scan degree is 100mm / s, the laser wavelength is 1030nm, the pulse width is 276fs, and the number of Z-axis feeds is 30.

[0064] 7.3) Start the machine and complete the processing. Then use wire cutting to separate the processed nozzle head from the substrate.

[0065] The aerospace engine nozzle head manufactured using this method exhibits superior high-temperature resistance, and the previously separate 200+ parts are now integrated into a single unit, resulting in increased overall strength. The use of nickel-based composite materials and pulsed laser additive manufacturing technology enables the integrated molding of the aerospace engine nozzle head parts, while pulsed lasers are employed for precision machining of the centrifugal bores in the fuel injector, significantly improving production efficiency and machining accuracy while ensuring a high product yield.

[0066] Using laser processing on the centrifugal holes of the fuel injector, which is the most difficult part to process, not only speeds up the processing but also improves the pass rate. This means that the processing of fuel injector heads for aerospace engines requires very little human intervention and is basically completed by machines, saving labor and processing costs, and shortening the processing time and reducing the difficulty.

[0067] like Figure 2 and Figure 3 As shown, existing laser powder bed melting uses continuous lasers. Because the particle size of the reinforcing particles is too small, they are prone to agglomeration during the manufacturing process, which affects the strengthening effect. Therefore, this invention uses a pulsed laser mode in the laser powder bed melting process. The continuous impact and stirring effect of the pulsed laser on the molten pool can make the reinforcing ceramic particles more uniformly distributed in the Inconel 718 alloy matrix and prevent agglomeration. In addition, the stirring of the molten pool by the pulsed laser makes the dendrite size more uniform and reduces the layering phenomenon.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser-laser augmentation-subtraction combination forming method for complex structures with multiple holes, characterized in that, Includes the following steps: The mixed powder was prepared and dried. Then, three-dimensional data of the aerospace engine nozzle head was collected and a model was built. The three-dimensional data was then imported into a pulsed laser selective melting device to generate a two-dimensional laser scanning path. The substrate is installed by loading the dried mixed powder into the forming chamber of the pulsed laser selective melting equipment and pre-laying the first layer of powder. The mixed powder is obtained by mixing nickel-based alloy powder particles with a particle size of 15-53μm with TiC. The first layer of powder is pre-laid in a flat manner with a powder layer thickness of 45-50μm, laser power of 180-200W, exposure time of 200-220μs, dot pitch of 25-30μm, row pitch of 60-65μm, scanning method of interlayer rotation of 90°, substrate preheating temperature of 70-80℃, substrate material of 316L, squeegee material of rubber, and laser spot diameter of 60-70μm. The pulsed laser selective melting equipment generates process parameters and printing trajectory. First, the forming chamber is evacuated, then protective argon gas is injected, and the forming laser is turned on to complete the manufacturing of the aerospace engine nozzle head. The forming laser is turned off and the drilling laser is turned on. The aerospace engine nozzle head is aligned with the laser focus. The laser drilling parameters are set, and the argon gas in the forming chamber is evacuated to create a vacuum before drilling. After the drilling is completed, the processed aerospace engine nozzle head is separated from the substrate. The laser drilling parameters are as follows: helical scanning mode, Z-axis feed rate of 20μm, number of scans of 8-10, laser energy of 35-40μJ, repetition frequency of 120-125KHz, scan speed of 90-100mm / s, laser wavelength of 1000-1030nm, pulse width of 270-276fs, and Z-axis feed of 30 times.

2. The laser-laser augmentation and subtraction combination forming method for complex hole structures according to claim 1, characterized in that, Before installing the substrate, clean the forming chamber and powder chamber in the pulsed laser selective melting equipment. When installing the substrate, place it on the work platform and fix it so that the upper edge of the substrate is aligned with the work platform in the forming chamber and the holes are aligned.

3. The laser-laser augmentation and subtraction combination forming method for complex hole structures according to claim 2, characterized in that, Adjust the height of the working platform so that the platform surface moves downward to the focal plane position, and adjust the position of the scraper so that the gap between the scraper and the substrate is zero.

4. The laser-laser augmentation and subtraction combination forming method for complex hole structures according to claim 1, characterized in that, After leveling the substrate and laying the first layer of mixed powder, the chamber is first evacuated to a vacuum, and then argon gas is injected as a protective gas. The argon gas pressure is maintained at 8-12 MPa, and the oxygen content in the chamber is kept below 0.0001%.

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