Method of electromagnetic coupling assisted additive manufacturing repair of aeroengine single crystal blade

Abstract

The application discloses a kind of electromagnetic coupling auxiliary's aero-engine single crystal blade additive manufacturing repair method, belong to the technical field of aero-engine turbine blade repair, it includes: to blade to be repaired area is pretreated and first electromagnetic coupling treatment;Laser additive manufacturing is repaired blade to be repaired area and second electromagnetic coupling treatment;Using shot peening technology strengthens blade repair area;To blade repair area is machined and third electromagnetic coupling treatment.The application combines electromagnetic coupling treatment and additive manufacturing technology to repair nickel-based single crystal high-temperature alloy blade, effectively reduces residual stress generated in each link of nickel-based single crystal turbine blade additive manufacturing repair process without changing the size accuracy of blade, repairs microstructure defects generated in additive manufacturing process, and the service life of the repaired blade is improved by shot peening strengthening, and the whole treatment process is green and low in consumption.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aero-engine turbine blade repair, and particularly relates to a method for repairing aero-engine single-crystal blades through additive manufacturing with electromagnetic coupling assistance. BACKGROUND

[0002] As the core power system of advanced fighter aircraft, aero-engines not only directly affect the performance of the aircraft, but also represent the level of national industrial development. Turbine blades, as the most important hot-end components of aero-engines, need to work in a high-temperature, high-pressure, and strongly corrosive environment.

[0003] Due to the excellent high-temperature mechanical properties of complex alternating single-crystal nickel-based superalloys, they are widely used in the preparation of aero-engine high-pressure turbine blades. After years of development, the materials used for aero-engine turbine blades have developed from early deformed superalloys, equiaxed crystal cast superalloys to directional solidification and single-crystal superalloys. However, aero-engine turbine blades will inevitably be subjected to high-cycle fatigue, creep elongation, environmental and thermal stress combination, corrosive atmosphere in the combustion chamber, and foreign object impact in the high-temperature, high-pressure, and high-speed rotating service environment, resulting in tip wear, cracks, surface ablation, and corrosion damage. These damages can greatly limit the service life of single-crystal blades and lead to frequent replacement of engine components. However, nickel-based single-crystal turbine blades are complex in structure and expensive to manufacture, resulting in high maintenance costs. Therefore, compared to directly replacing the blades, exploring more efficient, low-cost, and engineering-applicable single-crystal blade repair technologies has a very broad prospect.

[0004] In recent years, the laser additive manufacturing technology has shown broad application prospects in the manufacturing / remanufacturing field of single-crystal nickel-based superalloy parts, providing a possible solution for turbine blade repair. First, the customized design and manufacturing characteristics of laser additive manufacturing technology can ensure accurate molding of complex-shaped parts. Second, the high temperature gradient and high cooling rate in the laser additive manufacturing process can realize epitaxial growth of single-crystal materials, ensuring that the repaired turbine blades maintain a single-crystal structure.

[0005] As a new manufacturing technology, laser additive manufacturing technology has a very broad application prospect in the field of turbine blade repair of aero-engine. However, there are still many problems in the process of laser additive manufacturing repair of the blade. Firstly, it is not easy to control the heat flow direction in the process of laser additive manufacturing repair of the blade, and frequent and violent temperature changes in the molten pool can cause large residual stress and dislocation defects in the cladding layer. Secondly, micro cracks, pores, heterogeneous crystals and other micro defects are easily formed in the repair area. If the standard solid solution heat treatment process is directly carried out, the complete dissolution of the gamma prime phase makes the high-density dislocations almost unhindered, and it is easy to produce recrystallization nucleation and grain growth, which destroys the integrity of the single crystal and affects the performance of the repaired blade, thereby reducing the qualified rate of the additive manufacturing repair of the blade. Therefore, it is necessary to study the internal mechanism of recrystallization in the process of nickel-based single crystal additive manufacturing repair and the evolution rule of the microstructure of the deposition area in the heat treatment process, and to propose a strengthening treatment process to inhibit recrystallization and other micro defects, so as to avoid recrystallization, reduce the dislocation density of the deposition layer and residual stress, and improve the service performance of the repaired single crystal blade.

[0006] Shot peening mainly uses a large number of high-speed projectiles to continuously spray onto the surface of the material, so that the surface of the material is subjected to cyclic plastic deformation to form a residual compressive stress layer of a certain depth, thereby improving the surface performance. The good strengthening effect after shot peening is due to the crystal defects, grain refinement and residual compressive stress induced by shot peening. However, in the process of introducing residual stress, the strain or local stress concentration caused by uneven distribution of residual stress is the root cause of recrystallization. Therefore, while introducing shot peening, the occurrence rate of recrystallization can be reduced by regulating the level of residual stress distribution. SUMMARY

[0007] The purpose of the present application is to provide a method for electromagnetic coupling assisted additive manufacturing repair of aero-engine single crystal blade, so as to solve the problems of poor repair effect and large residual stress of the existing single crystal turbine blade.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is:

[0009] A method for electromagnetic coupling assisted additive manufacturing repair of aero-engine single crystal blade, comprising the following steps:

[0010] S1, non-destructive testing and digital modeling are performed on the blade repair area;

[0011] S2, machining is used to pretreat the blade repair area;

[0012] S3, the pretreated blade repair area is subjected to a first electromagnetic coupling treatment;

[0013] S4, repairing the blade to be repaired area by laser additive manufacturing according to the repair path and area designed in S1;

[0014] S5, performing second electromagnetic coupling treatment on the blade repair area after laser additive manufacturing to repair the micro defects generated in the laser additive manufacturing process;

[0015] S6, strengthening the blade repair area by shot peening technology;

[0016] S7, performing machining treatment on the blade repair area after strengthening;

[0017] S8, performing third electromagnetic coupling treatment on the blade repair area to homogenize the residual stress generated by shot peening;

[0018] S9, detecting the quality of the repaired blade.

[0019] Further, S1 specifically includes:

[0020] The damage degree and position of the blade are evaluated by X-ray or ultrasonic wave, and the damage position is scanned by three-dimensional scanning to obtain damage data and digital model of the blade, and the repair path and area of the blade additive manufacturing are designed based on CAD software.

[0021] Further, S2 specifically includes: removing the surface contaminants, oxides and damaged coating of the blade by polishing and sand blasting.

[0022] Further, S3 specifically includes:

[0023] The blade is clamped between the electrodes generating pulsed current by a clamp, and the blade is positioned at the center of the pulsed magnetic field, and the direction of the electric field and the magnetic field are controlled to be parallel to the axial direction of the blade by adjusting the clamping direction.

[0024] The magnetic field parameters of the first electromagnetic coupling treatment are 0.5T-1.0T, the current density is 1x10 2 A / mm 2 -3x10 2 A / mm 2 , and the number of electromagnetic coupling treatment groups is 5-10.

[0025] Further, after the laser additive manufacturing of the blade in S4, the dendrite epitaxial growth direction of the laser additive manufacturing repair area is observed and determined by metallographic microscope and electron microscope.

[0026] Further, S5 specifically includes:

[0027] The blade is clamped between the electrodes generating pulsed current by a clamp, and the blade is positioned at the center of the pulsed magnetic field, and the direction of the electric field and the magnetic field are controlled to be parallel to the axial direction of the blade by adjusting the clamping direction.

[0028] The magnetic field parameter of the second electromagnetic coupling treatment is 1.0T-2.0T, and the current density is 3*10 2 A / mm 2 ~5*10 2 A / mm 2 The number of electromagnetic coupling treatment groups is 10-20 groups.

[0029] Further, S6 specifically comprises: a large number of high-speed pellets are sprayed on the surface of the blade repair area, and a residual compressive stress affected layer is formed through small particle impact.

[0030] Further, S7 specifically comprises: the surface of the blade repair area after shot peening is strengthened is finely polished and polished to reduce the surface roughness of the blade repair area.

[0031] Further, S8 specifically comprises:

[0032] The blade is clamped by a clamp at both ends of an electrode generating a pulse current, and the blade repair area after shot peening is placed at the center position of the pulse magnetic field, and the electric field direction and the magnetic field direction are parallel to the repair layer dendrite epitaxial growth direction;

[0033] The magnetic field parameter of the third electromagnetic coupling treatment is 1.0T-2.0T, and the current density is 5*10 2 A / mm 2 ~1*10 3 A / mm 2 The number of electromagnetic coupling treatment groups is 10-20 groups.

[0034] The method for repairing the single-crystal blade of the aero-engine by the electromagnetic coupling assisted additive manufacturing provided by the application has the following beneficial effects:

[0035] The application repairs the damaged area of the blade by the additive manufacturing technology, enhances the surface hardness and fatigue resistance of the blade by the shot peening technology, and improves the service life of the blade. Meanwhile, the electromagnetic coupling treatment technology is combined to effectively reduce the residual stress generated in each link of the repair process and the micro defects of the repair material. The performance of the repair area is improved on the basis of not changing the macro size and shape of the blade, the vacancy defects and atomic diffusion behavior in the material are promoted, the peak stress is relaxed, the residual stress generated in the additive manufacturing process is homogenized, the movement of the dislocation source is activated, the dislocation density is reduced, and the microstructure defects are repaired, so that the mechanical properties of the material are improved. Compared with the traditional repair technology, the application combines the electromagnetic coupling treatment method to improve the blade repair effect and quality, reduce the maintenance cost and period, and has the advantages of being clean, efficient, green and pollution-free.

[0036] The application combines electromagnetic coupling processing technology and additive manufacturing technology to repair nickel-based single crystal high-temperature alloy blades, effectively reduces the residual stress generated in each link of the nickel-based single crystal turbine blade additive manufacturing repair process under the premise of not changing the size accuracy of the blade, repairs the microstructure defects generated in the additive manufacturing process, and prolongs the service life of the repaired blade through shot peening strengthening. The whole processing process is green and low in consumption.

[0037] The application repairs single crystal turbine blades by combining electromagnetic coupling with additive manufacturing. The set electromagnetic coupling processing parameters have better coupling effect in the processing process, better repair effect on the micro defects of the additive manufacturing nickel-based single crystal blade, and more obvious residual stress reduction. Compared with the traditional heat treatment technology, the electromagnetic coupling processing technology adopted by the application has the characteristics of high efficiency, cleanliness and safety, and does not change the macro size of the blade in the processing process. Through electromagnetic coupling processing, a high-strength magnetic field and an electric field can be generated to produce a high-density current on the surface of the material, thereby forming a nanoscale effect on the surface of the material, improving the microstructure defects of the part, homogenizing the residual stress in the processing and manufacturing process, and effectively repairing the micro defects in the additive manufacturing repair blade process. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The flowchart of the method for electromagnetic coupling assisted additive manufacturing repair of aero-engine single crystal blade of the application. DETAILED DESCRIPTION

[0039] The specific embodiments of the application are described below to facilitate the understanding of the application by those skilled in the art, but it should be clear that the application is not limited to the scope of the specific embodiments. It is obvious to those skilled in the art that all the applications utilizing the concept of the application are within the scope of the application as defined and determined by the appended claims.

[0040] Example 1

[0041] The embodiment provides a method for electromagnetic coupling assisted additive manufacturing repair of aero-engine single crystal blade, which combines electromagnetic coupling technology, additive manufacturing technology and shot peening strengthening technology, improves the blade repair effect and quality, reduces the maintenance cost and period, and the whole processing process is clean, efficient, green and pollution-free. Figure 1 , the embodiment takes DD5 nickel-based single crystal turbine blade as the repair object, and specifically includes the following contents:

[0042] Step S1, non-destructive testing and digital modeling are performed on the blade to be repaired area;

[0043] Specifically, the embodiment uses X-ray or ultrasonic wave or other technical means to evaluate the damage degree and position of the blade, and uses three-dimensional scanning on the damage position to obtain the damage data and digital model of the blade, and designs the repair path and area of the blade additive manufacturing based on the CAD software.

[0044] Step S2, using machining to pretreat the blade repair area;

[0045] Specifically, the embodiment uses polishing and sand blasting to remove the surface contaminants, oxides and damaged coatings of the blade, to ensure the cleanliness of the substrate surface and prepare for the subsequent additive manufacturing.

[0046] Step S3, first electromagnetic coupling treatment is performed on the pretreated blade repair area;

[0047] In order to reduce the residual stress generated by polishing, the blade is clamped between the two ends of the electrode generating pulse current by the clamp, and the blade is placed at the center position of the pulse magnetic field, and the direction of clamping is controlled to make the electric field and the magnetic field direction parallel to the axial direction of the blade.

[0048] In the specific operation, the electromagnetic coupling treatment device is started, the two coaxial copper electrodes are retreated to the two ends, the blade is clamped at the center position of the pulse magnetic field by the clamp, the two motors are moved to the center by starting the motor, and the blade is clamped at the center of the treatment cavity by controlling the size of the cross-section clamping force; after clamping, the clamp is withdrawn, and the two magnetic field coils are moved to the center of the treatment cavity. By adjusting the clamping direction, the electric field and the magnetic field direction are parallel to the axial direction of the blade.

[0049] The magnetic field parameter of the first electromagnetic coupling treatment is set to 0.5T, the current density is 1x10 2 A / mm 2 , and the number of treatment groups is set to 5 groups.

[0050] Step S4, according to the repair path and area designed by the digital modeling in S1, laser additive manufacturing is used to repair the blade repair area;

[0051] Laser additive manufacturing is to form a molten pool by heating the substrate with laser, and to send metal powder / silica into the molten pool through the powder feeding system, and when the laser beam leaves the molten pool, the molten pool solidifies rapidly to form the target part. By properly adjusting the process parameters, the epitaxial growth organization consistent with the original substrate growth direction can be obtained, so as to achieve the repair purpose of single crystal blade, so that the repair area and the part are consistent in composition, structure and performance. However, during the additive process, deformation (usually local) inevitably occurs under high thermal stress, resulting in a large residual stress in the repair area.

[0052] The embodiment determines the dendrite epitaxial growth direction of the laser additive manufacturing repair area after the laser additive manufacturing of the blade is completed by using a metallographic microscope and an electron microscope.

[0053] Step S5, to repair the micro-defects generated in the laser additive manufacturing process, the embodiment performs a second electromagnetic coupling treatment on the blade repair area after the laser additive manufacturing is completed;

[0054] The laser additive manufacturing single crystal is similar to the single crystal prepared by the directional solidification process in principle, both of which are to make dendrites grow epitaxially along the orientation by using the dendrite growth theory under forced conditions. Unlike the single crystal material by the directional solidification, the dendrite organization inside the laser additive manufacturing crystal is uniform and small, and the deviation in the growth direction is small. The growth direction of the dendrite is an important factor of the single crystal superalloy solidification organization, which has an important influence on the volume fraction of eutectic organization and element segregation, and directly affects the difficulty of the subsequent heat treatment process and the mechanical properties of the alloy.

[0055] The principle of clamping the blade for the second electromagnetic coupling treatment is that the electric field direction and the magnetic field direction are both parallel to the epitaxial growth direction of the repair layer dendrites, and the treatment area should be placed at the center position of the pulsed magnetic field, which is used to reduce the residual stress generated by the frequent change of temperature and ensure the stability and durability of the repair effect.

[0056] The magnetic field parameter of the second electromagnetic coupling treatment is 1.5T, the current density is 4×10 2 A / mm 2 , and the number of electromagnetic coupling treatment groups is 10.

[0057] The pulsed current density J acting on the blade part during the electromagnetic coupling treatment is determined by the performance characteristics of the part, and the current density is ensured by controlling the current size in the actual treatment process.

[0058] As a preferred embodiment of the embodiment, according to the repair result of S4, it is determined that the epitaxial growth direction of the DD5 single crystal turbine blade is consistent with the repair matrix, so as to determine the clamping direction. The electromagnetic coupling parameters are set as follows: the magnetic field strength is 1.5T, the current density J is 4×10 2 A / mm 2 , and the number of treatment groups of the second electromagnetic coupling treatment is set to 10 groups.

[0059] Step S6, using shot peening technology to strengthen the blade repair area;

[0060] In order to reduce the residual stress of the additive manufacturing repair area surface and near surface and improve the fatigue life and corrosion resistance, the embodiment uses shot peening strengthening technology to spray a large number of high-speed projectiles on the surface of the blade repair area, forms a residual compressive stress affected layer by small particle impact, and effectively enhances the surface hardness and fatigue resistance of the blade.

[0061] Five points are taken along the axial direction of the blade additive manufacturing repair area to test the residual stress after shot peening.

[0062] Step S7, machining the blade repair area after completing the strengthening;

[0063] Specifically, the surface of the blade after shot peening is processed to the required dimensional accuracy of the blade, fine polishing and grinding are performed, and the surface roughness is further reduced and the surface finish is improved

[0064] Step S8, third electromagnetic coupling treatment is performed on the blade repair area to homogenize the residual stress generated by shot peening;

[0065] The blade is clamped by a clamp at both ends of an electrode generating a pulse current, and the blade repair area after shot peening is placed at the center position of the pulse magnetic field, and the electric field direction and the magnetic field direction are parallel to the repair layer dendrite epitaxial growth direction;

[0066] The magnetic field parameter of the third electromagnetic coupling treatment is 2.0T, the current density is 5x10 2 A / mm 2 , and the number of electromagnetic coupling treatment groups is 20.

[0067] This embodiment reduces and homogenizes the residual compressive stress influence layer introduced by shot peening through electromagnetic coupling treatment, and further optimizes the stress distribution inside the blade additive manufacturing repair area. After the third electromagnetic coupling treatment, the five points in S6 are tested for the second round of residual stress test, and the test results show that the residual stress of each point has decreased significantly.

[0068] Step S9, detecting the quality of the repaired blade.

[0069] Although the specific embodiments of the application are described in detail with reference to the accompanying drawings, it should not be understood as limiting the scope of protection of the patent. Various modifications and variations made by those skilled in the art within the scope described in the claims are still within the scope of protection of the patent.

Claims

1. A method for additive manufacturing repair of single-crystal blades for aero-engines with electromagnetic coupling assistance, characterized in that, Includes the following steps: S1. Perform non-destructive testing and digital modeling on the area of ​​the blade to be repaired; S1 specifically includes: X-ray or ultrasonic testing was used to assess the extent and location of blade damage, and three-dimensional scanning was used to obtain damage data and digital models of the blade. Repair paths and areas for additive manufacturing of the blade were designed based on CAD software. S2. Pre-treatment of the blade area to be repaired is carried out by machining; S3. Perform the first electromagnetic coupling treatment on the pretreated area of ​​the blade to be repaired; S3 specifically includes: The blade is clamped to both ends of the electrode that generates the pulse current using a clamp, and the blade is positioned at the center of the pulse magnetic field. The direction of the clamp is adjusted to control the direction of both the electric field and the magnetic field to be parallel to the blade axis. The magnetic field parameters for the first electromagnetic coupling treatment were 0.5T~1.0T, and the current density was 1×10⁻⁶. 2 ~ 3×10 2 The number of electromagnetic coupling treatment groups is 5 to 10. S4. Based on the repair path and area designed by digital modeling in S1, use laser additive manufacturing to repair the area to be repaired on the blade. S5. Perform a second electromagnetic coupling treatment on the repaired area of ​​the blade after laser additive manufacturing to repair micro-defects generated during the laser additive manufacturing process; S5 specifically includes: The blade is clamped to both ends of the electrode that generates the pulse current using a clamp, and the blade is positioned at the center of the pulse magnetic field, with both the electric field direction and the magnetic field direction parallel to the dendritic epitaxial growth direction of the repair layer. The magnetic field parameters for the second electromagnetic coupling treatment were 1.0T~2.0T, and the current density was 3×10⁻⁶. 2 ~5×10 2 The number of electromagnetic coupling treatment groups is 10 to 20. S6. Use shot peening technology to strengthen the blade repair area; S6 specifically includes: spraying a large number of high-speed shot onto the surface of the blade repair area, and forming a residual compressive stress layer through the impact of small particles; S7. Machining is performed on the repaired area of ​​the blade after reinforcement. S8. Perform a third electromagnetic coupling treatment on the blade repair area to homogenize the residual stress generated by shot peening; S8 specifically includes: The blade is clamped to both ends of the electrode that generates the pulse current using a clamp, and the repaired area of ​​the blade after shot peening is placed at the center of the pulse magnetic field, with the electric field direction and the magnetic field direction both parallel to the dendritic epitaxial growth direction of the repair layer. The magnetic field parameters for the third electromagnetic coupling treatment were 1.0T~2.0T, and the current density was 5×10⁻⁶. 2 ~1×10 3 The number of electromagnetic coupling treatment groups is 10 to 20. S9. Inspect the quality of the repaired blades.

2. The method for repairing single-crystal aero-engine blades using electromagnetic coupling-assisted additive manufacturing according to claim 1, characterized in that, S2 specifically includes: removing contaminants, oxides, and damaged coatings from the blade surface by grinding and sandblasting.

3. The method for repairing single-crystal blades of aero-engines using electromagnetic coupling-assisted additive manufacturing according to claim 1, characterized in that: After the laser additive manufacturing of the blade is completed in step S4, the direction of dendritic epitaxial growth in the laser additive manufacturing repair area is determined by observation using a metallographic microscope and an electron microscope.

4. The method for additive manufacturing repair of single-crystal blades of aero-engines with electromagnetic coupling assistance according to claim 1, characterized in that, S7 specifically includes: performing fine polishing and grinding on the surface of the blade repair area after shot peening to reduce the surface roughness of the blade repair area.

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