Method for repairing hollow blade of aero-engine

Abstract

This invention discloses a method for repairing hollow blades of aero-engines, comprising the following steps: determining the area on the hollow blade where the film cooling holes need to be restored; determining the processing parameters for the film cooling holes; setting the femtosecond laser processing parameters; mounting the hollow blade to be repaired onto a machine tool for positioning; processing the film cooling holes to be repaired using femtosecond laser processing technology; performing quality inspection on the repaired film cooling holes according to the process parameters of the film cooling holes; and testing the water flow rate of the repaired hollow blade. This invention utilizes the ultrashort pulse laser of femtosecond laser processing to irradiate the blocked film cooling holes on the hollow blade. The ultra-high energy density of the femtosecond laser ablates and vaporizes the non-conductive material blocked at the film cooling holes due to welding or additive repair, thereby achieving the effect of restoring or adjusting the size of the film cooling holes. The water flow rate is then tested to detect the aperture of the film cooling holes, ensuring that the water flow rate of the repaired hollow blade fully meets the technical standards.

Description

Technical Field

[0001] This invention relates to the field of aircraft engine component repair technology, and in particular to a method for repairing hollow aircraft engine blades. Background Technology

[0002] Maintenance extends the service life of aero-engines by more than 80% of their total lifespan, with the maintenance of hollow blades being a crucial aspect. Hollow blades typically suffer from cracks, ablation, and material loss. Maintenance primarily involves repairing material defects using welding and laser additive manufacturing, followed by adaptive machining to restore the blade's shape. For hollow blades, such as... Figure 1 As shown, during the repair process of welding and laser additive manufacturing, it is inevitable that some air film pores on the hollow blade 100 will be partially or completely blocked, resulting in air film pores 200 with unqualified pore size. The blocked air film pores must be repaired.

[0003] Currently, the industry typically uses electrical discharge machining (EDM) to repair blocked film vents on hollow blades. For example, Chinese patent application CN114289808A discloses an EDM method for machining irregular film vents on turbine blades. This method employs a CNC EDM small-hole machine to perform distributed EDM machining on the film vents on the turbine blades. The CNC EDM small-hole machine uses a thin copper tube electrode wire for EDM. This patented method for machining irregular film vents on turbine blades utilizes a simple EDM copper tube electrode wire instead of a cutting tool, machining irregular holes in materials that cannot be machined by a cutting tool. It high-speed mills the irregular film vents on high-temperature alloy blades according to the machining trajectory. The entire machining of irregular film vents on turbine blades requires only one setup and is fully automated, resulting in high machining efficiency. Furthermore, by analyzing the real-time wear of the electrode wire during machining, the actual machining trajectory is re-determined, effectively improving machining accuracy.

[0004] However, the aforementioned patent application uses electrical discharge machining (EDM) to repair the film pores. EDM removes excess metal through electro-erosion caused by pulsed spark discharge between the electrode and the workpiece, requiring the workpiece to be conductive. Therefore, it can only process conductive metal substrates and cannot remove non-conductive material from the film pores; furthermore, if... Figure 2As shown, during electrical discharge machining of metal materials, the high temperature generated by the pulse discharge causes electro-corrosion of the surface layer of the metal substrate 300. Some of the molten metal re-solidifies on the surface of the film pores, forming a remelted layer 400 with a thickness of 10μm to 40μm. Since hollow blades of aero engines operate in harsh high-temperature environments, the presence of the remelted layer will cause uneven surface texture of the hollow blade, resulting in a decrease in the performance of the hollow blade. Furthermore, the microcracks in the remelted layer will cause fatigue crack propagation of the hollow blade under long-term alternating thermal stress, leading to the failure of the hollow blade and causing an accident, posing a serious safety hazard. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for repairing hollow blades of aero engines, which can effectively improve the repair effect of blocked air film pores on hollow blades.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for repairing hollow blades of aero-engines, comprising the following steps:

[0007] Step 1: Compare the hollow blade to be repaired, which has undergone welding, additive repair, spraying and adaptive machining, with the design drawings to determine the areas on the hollow blade where the film cooling holes need to be restored.

[0008] Step 2: Determine the machining parameters of the air film holes according to the design drawings;

[0009] Step 3: Set the femtosecond laser processing parameters according to the processing parameters determined in Step 2;

[0010] Step 4: Install the hollow blade to be repaired onto the machine tool and position the hollow blade.

[0011] Step 5: Use femtosecond laser processing technology to process the air film pores to be repaired. The ultra-high energy density of the ultra-short pulse in femtosecond laser processing technology is used to remove the non-conductive material covering or blocking the air film pores.

[0012] Step 6: Perform quality inspection on the repaired air film pores according to the process parameters of the air film pores;

[0013] Step 7: Install the repaired hollow blade into the water flow testing equipment to test the water flow rate of the hollow blade.

[0014] Furthermore, in step two, the processing parameters for the air film pores include the pore diameter, pore position, pore surface roughness, and parameters of the pore opening and the recast layer on the pore wall.

[0015] Furthermore, in step three, the processing parameters of the femtosecond laser include parameters such as laser beam type, lens focal length, front dark box hole, distance from the final lens to the workpiece surface, auxiliary gas type, auxiliary gas flow rate, pulse width, pulse speed, laser energy, laser power, laser beam motion mode, laser beam motion angle, and feed rate.

[0016] Furthermore, in step three, the processing parameters of the femtosecond laser are: pulse width range of 10fs to 200fs, pulse speed of 100KHz, laser power of 10W, feed rate of 10μm, and number of processing layers of 50.

[0017] Furthermore, in step four, the hollow blade to be repaired is installed onto the machine tool using tooling, and the hollow blade is positioned using the machine tool positioning test sensor.

[0018] Furthermore, in step five, the energy density of the ultrashort pulse in the femtosecond laser processing technology is greater than or equal to 10. 18 J / cm 2 .

[0019] Furthermore, in step five, the non-conductive material covering or blocking the air film pores is a ceramic thermal barrier coating.

[0020] Furthermore, in step six, the quality inspection parameters of the repaired air film pores include pore diameter, pore position accuracy, pore surface roughness, and parameters of the recast layer at the pore opening and pore wall.

[0021] Furthermore, in step seven, if the water flow test value meets the specified range, the hollow blade repair is deemed qualified; if the water flow test value is less than the lower limit of the specified range, the processing diameter of the air film hole is increased within the range specified in the design drawings, and then steps three to seven are executed sequentially; if the water flow test value is greater than the upper limit of the specified range, the unqualified air film hole on the hollow blade is resealed, and then the processing diameter of the air film hole is reduced within the range specified in the design drawings, and then steps one to seven are executed sequentially.

[0022] The beneficial effects of this invention are as follows: This invention improves the repair method for hollow blades of aero-engines by optimizing the electrical discharge machining (EDM) used in traditional repair methods to femtosecond laser machining. The ultrashort pulse laser of femtosecond laser machining irradiates the blocked film cooling pores of the hollow blade. The ultra-high energy density of the femtosecond laser ablates and vaporizes the non-conductive material blocked at the film cooling pores due to welding or additive repair, achieving the preparation of micropores without a remelting layer. This restores or adjusts the size of the film cooling pores. Furthermore, water flow rate testing is used to detect the pore diameter, ensuring that the water flow rate of the repaired hollow blade fully meets the technical standards. Attached Figure Description

[0023] Figure 1 A schematic diagram of a hollow blade with blocked film air pores;

[0024] Figure 2 This is a cross-sectional view of a microhole produced by electrical discharge machining in the prior art.

[0025] Figure 3 This is a cross-sectional view of the micropores processed using the repair method of the present invention;

[0026] Figure 4 This is a longitudinal cross-sectional view of the micropores processed using the repair method of the present invention.

[0027] The markings in the figure are: 100-hollow blade, 200-unqualified film pores, 300-metal substrate, 400-remelted layer, 500-micropores, 600-ceramic thermal barrier coating. Detailed Implementation

[0028] To facilitate understanding of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] In the description of this invention, it should be noted that the terms "front", "rear", "left", "right", "up", "down", "inner", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0030] Example

[0031] The method for repairing hollow blades of aero-engines disclosed in this invention is carried out according to the following steps:

[0032] Step 1: Identify the processing area

[0033] Hollow blades, after welding, additive repair, spraying, and adaptive machining, such as Figure 1 As shown, the film cooling pores on the hollow blade 100 may become blocked during welding and laser additive manufacturing repair processes, resulting in film cooling pores 200 with substandard diameters on the hollow blade 100. These areas on the hollow blade 100 with substandard film cooling pores 200 must be repaired. The first step is to determine the repair area. This is done by comparing the hollow blade to be repaired with its design drawings to identify which areas on the hollow blade have mismatched film cooling pore diameters and thus, these areas are designated for repair.

[0034] Step 2: Determine the machining parameters for the film pores

[0035] In this step, the machining parameters of the air film hole are determined according to the design drawings. The machining parameters of the air film hole include hole diameter, hole position accuracy, hole surface roughness, and parameters of the recast layer at the hole opening and hole wall.

[0036] Step 3: Determine the femtosecond laser processing parameters

[0037] Based on the gas film aperture processing parameters determined in step two, the corresponding femtosecond laser processing parameters are determined. The femtosecond laser processing parameters include laser beam type, lens focal length, front cassette hole, distance from the final lens to the workpiece surface, auxiliary gas type, auxiliary gas flow rate, pulse width, pulse speed, laser energy, laser power, laser beam motion mode, laser beam motion angle, and feed rate. Among them, the femtosecond laser processing parameters are a pulse width range of 10fs to 200fs, a pulse speed of 100KHz, a laser power of 10W, a feed rate of 10μm, and 50 processing layers.

[0038] Step 4: Clamping and Positioning

[0039] The hollow blade to be repaired is installed on the tooling, and then clamped onto the machine tool using the tooling. The machine tool positioning test sensor is then used to position the hollow blade.

[0040] Step 5: Micro-hole fabrication

[0041] Input the femtosecond laser processing parameters and the film cooling hole processing parameters, and use femtosecond laser processing to process the film cooling holes in the restored processing area on the hollow blade. Utilize a femtosecond laser processing energy density greater than or equal to 10-1. 18 J / cm 2的 An ultrashort pulse laser is used to irradiate the blocked film cooling holes of the hollow blade, causing the non-conductive materials such as the ceramic thermal barrier coating at the film cooling holes to ablate and vaporize. After all the machining holes are completed, the hollow blade is removed from the machine tool.

[0042] Step 6: Quality Inspection of Air Film Pores

[0043] The quality inspection of the repaired film pores on the hollow blades includes pore diameter, pore position accuracy, pore surface roughness, and parameters of the recast layer at the pore opening and pore wall.

[0044] Step 7: Water Flow Measurement

[0045] The repaired hollow blade is installed in a water flow testing device to test the water flow. If the water flow test value is within the specified range, the hollow blade repair is deemed qualified; if the water flow test value is less than the lower limit of the specified range, the processing diameter of the air film hole is increased within the range specified in the design drawings, and steps three to seven are executed sequentially; if the water flow test value is greater than the upper limit of the specified range, the unqualified air film hole on the hollow blade is resealed, and then the processing diameter of the air film hole is reduced within the range specified in the design drawings, and steps one to seven are executed sequentially.

[0046] After additive repair, machining, and thermal barrier coating restoration of a certain type of aero-engine guide vane, a water flow test was conducted. The test results showed that the water flow was less than the lower limit specified in the technical standard. Upon inspection, it was found that some film cooling pores were blocked by ceramic thermal barrier coating material, thus requiring adjustment of the water flow on the vane. The condition of the film cooling pores on the vane surface was visually inspected. A 0.4mm diameter go / no-go gauge was used to test the diameter of the film cooling pores on the vane. If the go / no-go gauge passed through, the diameter was acceptable; if it failed, the diameter was unacceptable, and the unacceptable film cooling pores were marked. The diameter of the unacceptable film cooling pores was increased by femtosecond laser processing, and the water flow was adjusted to meet the technical standard requirements. During water flow adjustment, the vane was first clamped in the equipment, and the coordinates of the marked holes to be processed were acquired using the equipment's rangefinder camera. After setting the femtosecond laser equipment parameters, all marked film cooling pores were processed, and the water flow was tested again. If the water flow was acceptable, the next process could proceed. If the water flow rate is too low, the marked air film holes will be re-processed with femtosecond laser. The processing hole diameter will be appropriately increased within the range required by the design drawings. After processing, the water flow rate of the blade will be tested again until the water flow rate meets the technical standard requirements.

[0047] A schematic diagram of the micropores after femtosecond laser processing in the above embodiments is shown below. Figure 4 As shown, the ultrashort pulse laser used in femtosecond laser processing passes through the ceramic thermal barrier coating 600 covering the surface of the metal substrate 300, causing the ceramic thermal barrier coating 600, which was blocking the original gas film pores, to ablate and vaporize, thus reforming micropores 500 within the metal substrate 300 that meet the pore size requirements; the cross-sectional view of the gas film pores after processing is shown in the figure. Figure 3 As shown, the micropore diameter is qualified, the micropore periphery is smooth, the pore shape is complete, and no remelting layer appears on the micropore.

[0048] Comparative Example

[0049] Electrical discharge machining (EDM) was used to repair areas with substandard film-forming pores on hollow blades. The resulting micropore cross-section is shown in the image. Figure 2As shown, the high temperature generated by the pulse discharge in electrical discharge machining (EDM) melts the surface layer of the metal substrate 300, causing electro-corrosion. Part of the molten metal resolidifies on the surface of the machined micropores, forming a 30 μm thick remelted layer 400, which deforms the shape around the micropores, resulting in irregular pore shapes. After the repaired hollow blade operates in a high-temperature environment, the remelted layer 400 causes uneven surface texture, leading to a decline in the blade's performance. Furthermore, microcracks in the remelted layer 400 cause fatigue crack propagation under long-term alternating thermal stress, ultimately resulting in blade failure.

Claims

1. A method for repairing hollow blades of an aero-engine, characterized in that: Includes the following steps: Step 1: Compare the hollow blade to be repaired, which has undergone welding, additive repair, spraying and adaptive machining, with the design drawings to determine the areas on the hollow blade where the film cooling holes need to be restored. Step 2: Determine the machining parameters of the air film holes according to the design drawings; Step 3: Set the femtosecond laser processing parameters according to the processing parameters determined in Step 2; Step 4: Install the hollow blade to be repaired onto the machine tool and position the hollow blade. Step 5: Use femtosecond laser processing technology to process the air film pores to be repaired. The ultra-high energy density of the ultra-short pulse in femtosecond laser processing technology is used to remove the non-conductive material covering or blocking the air film pores. Step 6: Perform quality inspection on the repaired air film pores according to the process parameters of the air film pores; Step 7: Install the repaired hollow blade into the water flow testing equipment and test the water flow rate of the hollow blade. If the water flow rate test value is within the specified range, the hollow blade repair is deemed qualified. If the water flow rate test value is less than the lower limit of the specified range, increase the processing diameter of the air film hole within the range specified in the design drawings and then proceed with Step 3 to Step 7 in sequence. If the water flow rate test value is greater than the upper limit of the specified range, reseal the unqualified air film hole on the hollow blade, and then reduce the processing diameter of the air film hole within the range specified in the design drawings and then proceed with Step 1 to Step 7 in sequence.

2. The method for repairing hollow blades of an aero-engine as described in claim 1, characterized in that: In step two, the processing parameters of the air film hole include hole diameter, hole position, hole surface roughness, and parameters of the recast layer at the hole opening and hole wall.

3. The method for repairing hollow blades of an aero-engine as described in claim 1, characterized in that: In step three, the femtosecond laser processing parameters include laser beam type, lens focal length, front dark box hole, distance from the final lens to the workpiece surface, auxiliary gas type, auxiliary gas flow rate, pulse width, pulse speed, laser energy, laser power, laser beam motion mode, laser beam motion angle, and feed rate.

4. The method for repairing hollow blades of an aero-engine as described in claim 3, characterized in that: In step three, the femtosecond laser processing parameters are: pulse width range of 10fs to 200fs, pulse speed of 100KHz, laser power of 10W, feed rate of 10μm, and number of processing layers of 50.

5. The method for repairing hollow blades of an aero-engine as described in claim 1, characterized in that: In step four, the hollow blade to be repaired is installed onto the machine tool using tooling, and the hollow blade is positioned using the machine tool positioning test sensor.

6. The method for repairing hollow blades of an aero-engine as described in claim 1, characterized in that: In step five, the energy density of the ultrashort pulse in the femtosecond laser processing technology is greater than or equal to 10. 18 J / cm 2 .

7. The method for repairing hollow blades of an aero-engine as described in claim 1, characterized in that: In step five, the non-conductive material covering or blocking the air film pores is a ceramic thermal barrier coating.

8. The method for repairing hollow blades of an aero-engine as described in claim 1, characterized in that: In step six, the quality inspection parameters of the repaired air film pores include pore diameter, pore position accuracy, pore surface roughness, and parameters of the recast layer at the pore opening and pore wall.

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