Electromagnetic coupling assisted aero-engine single crystal blade additive manufacturing repairing method

Abstract

The invention discloses an electromagnetic-coupling-assisted aero-engine single-crystal blade additive manufacturing repairing method, and belongs to the technical field of aero-engine turbine blade repairing. The method comprises the steps that pretreatment and first electromagnetic coupling treatment are conducted on a to-be-repaired area of a blade; repairing a to-be-repaired area of the blade by adopting laser additive manufacturing and carrying out secondary electromagnetic coupling treatment; strengthening a blade repair area by adopting a shot blasting technology; and machining treatment and third electromagnetic coupling treatment are conducted on the blade repairing area. According to the method, the nickel-based single-crystal high-temperature alloy blade is repaired by combining electromagnetic coupling treatment and the additive manufacturing technology, on the premise that the size precision of the blade is not changed, residual stress generated in all links in the additive manufacturing repairing process of the nickel-based single-crystal turbine blade is effectively reduced, microstructure defects generated in the additive manufacturing process are repaired, and the quality of the blade is improved. And meanwhile, the service life of the repaired blade is prolonged through shot peening strengthening, and the whole treatment process is green and low in consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft engine turbine blade repair, and in particular relates to an electromagnetic coupling-assisted aircraft engine single crystal blade additive manufacturing and repair method. Background Art

[0002] As the core power system of advanced fighter jets, aircraft engines not only directly affect the performance of aircraft, but also represent the level of national industrial development. As the most important hot end component of aircraft engines, turbine blades need to work in a high temperature, high pressure and highly 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 high-pressure turbine blades for aircraft engines. After years of development, the materials used for aircraft engine turbine blades have evolved from early deformed superalloys and equiaxed crystal casting superalloys to directional solidification and single-crystal superalloys. However, in the service environment of high temperature, high pressure, and high-speed rotation, aircraft engine turbine blades will inevitably be affected by factors such as high-cycle fatigue, creep elongation, environmental and thermal stress combination, corrosive atmosphere in the combustion chamber, and foreign body erosion, causing damage such as blade tip wear, cracks, surface ablation and corrosion. These damages will greatly limit the service life of single-crystal blades and lead to frequent replacement of engine components. However, nickel-based single-crystal turbine blades have a complex structure and are expensive to manufacture, resulting in high maintenance costs. Therefore, compared with directly replacing blades, exploring more efficient, low-cost, and engineering-applicable single-crystal blade repair technology has a very broad prospect.

[0004] The laser additive manufacturing technology that has emerged in recent years has shown broad application prospects in the manufacturing / remanufacturing of single-crystal nickel-based high-temperature alloy parts, and provides a possible solution for the repair of turbine blades: First, the customized design and manufacturing characteristics of laser additive manufacturing technology can ensure the precise forming of parts with complex morphologies; secondly, the high temperature gradient and high cooling rate in the laser additive manufacturing process can realize the epitaxial growth of single-crystal materials, ensuring that the turbine blades maintain a single crystal structure after repair.

[0005] As an emerging manufacturing technology, laser additive manufacturing technology has a very broad application prospect in the field of aircraft engine turbine blade repair. However, there are still many problems in the process of blade laser additive manufacturing repair: first, it is not easy to control the heat flow direction during the laser additive manufacturing process of blade repair, and the frequent and drastic temperature changes in the molten pool will cause large residual stress and dislocation defects in the cladding layer; second, micro defects such as microcracks, pores, and impurities are easily formed in the repair area. If the standard solution heat treatment process is directly carried out, the γ′ phase is completely dissolved, so that high-density dislocations can move almost unhindered, which is easy to produce recrystallization nucleation and grain growth, destroying the integrity of the single crystal, and then affecting the performance of the blade after repair, and reducing the qualified rate of blade additive manufacturing repair. Therefore, it is necessary to study the internal mechanism of recrystallization in the process of nickel-based single crystal additive manufacturing repair and the law of evolution of the microstructure of the deposition area during the heat treatment process, and propose a strengthening treatment process to inhibit micro defects such as recrystallization, avoid recrystallization, reduce the dislocation density of the deposition layer, reduce 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, causing cyclic plastic deformation on the surface and forming a residual compressive stress layer of a certain depth, thereby improving its surface properties. 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 the uneven distribution of residual stress is the root cause of recrystallization. Therefore, when introducing shot peening, it is necessary to reduce the incidence of recrystallization by regulating the residual stress distribution level. Summary of the invention

[0007] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide an electromagnetic coupling-assisted method for additive manufacturing and repair of single-crystal aircraft engine blades, so as to solve the problems of poor repair effect and large residual stress of existing single-crystal turbine blades.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for additive manufacturing and repairing of single crystal blades of an aero-engine assisted by electromagnetic coupling, comprising the following steps:

[0010] S1. Perform nondestructive testing and digital modeling on the area of ​​the blade to be repaired;

[0011] S2. Pre-treating the area of ​​the blade to be repaired by machining;

[0012] S3, performing a first electromagnetic coupling treatment on the pre-treated blade area to be repaired;

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

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

[0015] S6. Use shot peening technology to strengthen the blade repair area;

[0016] S7, machining the repaired area of ​​the blade after strengthening;

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

[0018] S9. Check the quality of the repaired blades.

[0019] Furthermore, S1 specifically includes:

[0020] X-rays or ultrasound are used to assess the damage extent and location of the blades, and 3D scanning is used to obtain the damage data and digital model of the blades. The repair path and area for additive manufacturing of the blades are designed based on CAD software.

[0021] Furthermore, S2 specifically includes: removing pollutants, oxides and damaged coatings on the blade surface by grinding and sandblasting.

[0022] Furthermore, S3 specifically includes:

[0023] The blade is clamped at both ends of the electrode generating the pulse current by a clamp, and the blade is placed at the center of the pulse magnetic field. The direction of the clamp is adjusted to control the direction of the electric field and the magnetic field to be parallel to the blade axis.

[0024] The magnetic field parameters of the first electromagnetic coupling treatment were 0.5T~1.0T, and the current density was 1×10 2 A / mm 2 ~3×10 2 A / mm 2 ; The number of electromagnetic coupling processing groups is 5 to 10 groups.

[0025] Furthermore, after completing the laser additive manufacturing of the blade in S4, metallographic microscope and electron microscope observations were used to determine the epitaxial growth direction of the dendrites in the laser additive manufacturing repair area.

[0026] Furthermore, S5 specifically includes:

[0027] The blade is clamped at both ends of the electrode generating the pulse current by a fixture, and the blade is placed at the center of the pulse magnetic field, with the directions of the electric field and the magnetic field being parallel to the epitaxial growth direction of the repair layer dendrite;

[0028] The magnetic field parameters of the second electromagnetic coupling treatment were 1.0T~2.0T, and the current density was 3×10 2 A / mm 2 ~5×10 2 A / mm 2 ; The number of electromagnetic coupling processing groups is 10 to 20 groups.

[0029] Furthermore, S6 specifically includes: spraying a large number of high-speed projectiles onto the surface of the blade repair area, and forming a residual compressive stress influence layer through the impact of small particles.

[0030] Furthermore, S7 specifically includes: finely polishing and grinding the surface of the blade repair area after shot peening to reduce the surface roughness of the blade repair area.

[0031] Furthermore, S8 specifically includes:

[0032] The blade is clamped at both ends of the electrodes generating pulse current by a fixture, and the repaired area of ​​the blade after shot peening is placed at the center of the pulse magnetic field, with the directions of the electric field and the magnetic field parallel to the epitaxial growth direction of the repaired layer dendrites;

[0033] The magnetic field parameters of the third electromagnetic coupling treatment were 1.0T~2.0T, and the current density was 5×10 2 A / mm 2 ~1×10 3 A / mm 2 ; The number of electromagnetic coupling processing groups is 10 to 20 groups.

[0034] The electromagnetic coupling-assisted additive manufacturing and repair method for single-crystal blades of an aero-engine provided by the present invention has the following beneficial effects:

[0035] The present invention repairs the damaged area of ​​the blade through additive manufacturing technology, and enhances the surface hardness and fatigue resistance of the blade through shot peening technology, thereby increasing the service life of the blade. At the same time, combined with electromagnetic coupling processing technology, the residual stress generated in each link of the repair process is effectively reduced, and the microscopic defects of the material are repaired. On the basis of not changing the macroscopic size and shape of the blade, the performance of the repair area is improved, the vacancy defects and atomic diffusion behavior in the material are promoted, the peak stress is relaxed, and the residual stress generated in the additive manufacturing process is homogenized; at the same time, the movement of the dislocation source is activated, the dislocation density is reduced, and the microscopic structural defects are repaired, thereby improving the mechanical properties of the material. Compared with traditional repair technology, the present invention combines the electromagnetic coupling processing method to improve the blade repair effect and quality, reduce the maintenance cost and cycle, and has the advantages of being clean, efficient, green and pollution-free.

[0036] The present invention combines electromagnetic coupling processing technology with additive manufacturing technology to repair nickel-based single crystal high-temperature alloy blades. Without changing the blade size accuracy, it effectively reduces the residual stress generated in each link of the nickel-based single crystal turbine blade additive manufacturing repair process, repairs the microstructural defects generated in the additive manufacturing process, and at the same time increases the service life of the repaired blades through shot peening. The entire processing process is green and low-consumption.

[0037] The present invention combines electromagnetic coupling with additive manufacturing to repair single crystal turbine blades. The electromagnetic coupling processing parameters are set to achieve better coupling effects during the processing, better repair effects on micro defects of additively manufactured nickel-based single crystal blades, and more obvious reductions in residual stress. Compared with traditional heat treatment technology, the electromagnetic coupling processing technology used in the present invention is efficient, clean, and safe, and does not change the macroscopic size of the blades during the processing. Through electromagnetic coupling processing, high-intensity magnetic and electric fields can be generated, causing high-density currents to be generated on the surface of the material, thereby forming a nanoscale effect on the surface of the material, improving the microstructural defects of the parts, and homogenizing the residual stresses in the manufacturing process, thereby effectively repairing the micro defects in the additive manufacturing process of the blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention is a flow chart of the electromagnetic coupling-assisted additive manufacturing and repair method for single crystal blades of an aero-engine. DETAILED DESCRIPTION

[0039] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0040] Example 1

[0041] This embodiment provides an electromagnetic coupling-assisted method for additive manufacturing and repair of single-crystal blades of aircraft engines, which combines electromagnetic coupling technology, additive manufacturing technology and shot peening technology to improve the blade repair effect and quality, reduce the maintenance cost and cycle, and the entire processing process is clean, efficient, green and pollution-free. Figure 1 This embodiment takes DD5 nickel-based single crystal turbine blade as the repair object, which specifically includes the following contents:

[0042] Step S1, performing nondestructive testing and digital modeling on the area to be repaired of the blade;

[0043] Specifically, this embodiment uses X-rays, ultrasound or other technical means to evaluate the damage degree and location of the blade, and uses three-dimensional scanning on the damaged location 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 CAD software.

[0044] Step S2, pre-treating the area of ​​the blade to be repaired by machining;

[0045] Specifically, this embodiment uses grinding and sandblasting to remove pollutants, oxides and damaged coatings on the blade surface to ensure that the substrate surface is clean and ready for subsequent additive manufacturing.

[0046] Step S3, performing a first electromagnetic coupling treatment on the pre-treated area of ​​the blade to be repaired;

[0047] In order to reduce the residual stress caused by grinding, in this embodiment, the blade is clamped at both ends of the electrode generating the pulse current by a clamp, and the blade is placed at the center of the pulse magnetic field. By adjusting the clamping direction, the electric field and magnetic field directions are controlled to be parallel to the blade axis.

[0048] In specific operation, start the electromagnetic coupling processing device, wait for the two coaxial copper electrodes to return to the two ends, clamp the blade at the center of the pulse magnetic field through the clamp, start the motor to move the two motors toward the center, and control the size of the cross-section clamping force to clamp the blade in the center of the processing chamber; after clamping, withdraw the clamp and control the two magnetic field coils to move to the center of the processing chamber. By adjusting the clamping direction, the electric field and magnetic field directions are controlled to be parallel to the blade axis.

[0049] The magnetic field parameters of the first electromagnetic coupling treatment were set to 0.5 T and the current density was 1×10 2 A / mm 2 ; The number of treatment groups was set to 5.

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

[0051] Laser additive manufacturing uses laser to heat the substrate to form a molten pool, and metal powder / wire is fed into the molten pool through a powder feeding system. When the laser beam leaves the molten pool, the molten pool solidifies rapidly to form the target part. By properly adjusting the process parameters, an epitaxial growth structure consistent with the original substrate growth direction can be obtained, thereby achieving the purpose of repairing single crystal blades, so that the repair area and the part are consistent in composition, structure and performance to the greatest extent. However, in the additive process, (usually local) deformation is inevitable under high thermal stress, resulting in large residual stress in the repair area.

[0052] After completing the laser additive manufacturing of the blade in this embodiment, a metallographic microscope and an electron microscope are used to observe and determine the epitaxial growth direction of the dendrites in the laser additive manufacturing repair area.

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

[0054] The principle of laser additive manufacturing of single crystals is similar to that of directional solidification process for preparing single crystals. Both use the dendrite growth theory under forced conditions to make the dendrites grow epitaxially along the orientation. Unlike single crystal materials of directionally solidified, the dendrite structure inside the grains of laser additive manufacturing is uniform and fine, with small deviation in the growth direction. The growth direction of dendrites is an important factor in the solidification structure of single crystal high-temperature alloys. It has an important influence on the volume fraction and element segregation of the eutectic structure, and directly affects the difficulty of subsequent heat treatment process and the mechanical properties of the alloy.

[0055] The principle of blade clamping in the second electromagnetic coupling treatment is that the directions of the electric field and the magnetic field are parallel to the epitaxial growth direction of the dendrites of the repair layer, and the treatment area should be placed in the center of the pulsed magnetic field to reduce the residual stress caused by frequent temperature changes and ensure the stability and durability of the repair effect.

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

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

[0058] As a preferred embodiment of this invention, according to the S4 repair result, it is determined that the epitaxial growth direction of the DD5 single crystal turbine blade is consistent with the repair substrate, thereby determining the clamping direction. The electromagnetic coupling parameters are set to a magnetic field strength of 1.5T and a current density J of 4×10 2 A / mm 2 The number of treatment groups for the second electromagnetic coupling treatment was 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 on the surface and near-surface layer of the additive manufacturing repair area and improve the fatigue life and corrosion resistance, this embodiment adopts shot peening strengthening technology to spray a large number of high-speed projectiles on the surface of the blade repair area. Through the impact of small particles, a residual compressive stress influence layer is formed, which effectively enhances the surface hardness and fatigue resistance of the blade.

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

[0062] Step S7, machining the repaired area of ​​the blade after strengthening;

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

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

[0065] The blade is clamped at both ends of the electrodes generating pulse current by a fixture, and the repaired area of ​​the blade after shot peening is placed at the center of the pulse magnetic field, with the directions of the electric field and the magnetic field parallel to the epitaxial growth direction of the repaired layer dendrites;

[0066] The magnetic field parameters of the third electromagnetic coupling treatment were 2.0 T and the current density was 5×10 2 A / mm 2 ; The number of electromagnetic coupling processing groups is 20.

[0067] This embodiment uses electromagnetic coupling treatment to reduce and homogenize the residual compressive stress influence layer introduced by shot peening, and further optimizes the stress distribution inside the blade additive manufacturing repair area. After the third electromagnetic coupling treatment, the five points in S6 were subjected to a second round of residual stress testing, and the test results showed that the residual stress at each point had decreased significantly.

[0068] Step S9: Detect the quality of the repaired blades.

[0069] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for additive manufacturing and repairing of single crystal blades of an aero-engine assisted by electromagnetic coupling, characterized in that: The following steps are involved: S1. Perform nondestructive testing and digital modeling on the area of ​​the blade to be repaired; S2. Pre-treating the area of ​​the blade to be repaired by machining; S3, performing a first electromagnetic coupling treatment on the pre-treated blade area to be repaired; S4, repairing the area to be repaired of the blade by laser additive manufacturing according to the repair path and area designed by digital modeling in S1; S5, performing a second electromagnetic coupling treatment on the blade repair area after laser additive manufacturing to repair micro defects generated during the laser additive manufacturing process; S6. Use shot peening technology to strengthen the blade repair area; S7, machining the repaired area of ​​the blade after strengthening; S8, performing a third electromagnetic coupling treatment on the blade repair area to homogenize the residual stress generated by shot peening; S9. Check the quality of the repaired blades.

2. The electromagnetic coupling-assisted additive manufacturing and repair method for single crystal aero-engine blades according to claim 1, characterized in that: The S1 specifically includes: X-rays or ultrasound are used to assess the damage extent and location of the blades, and 3D scanning is used to obtain the damage data and digital model of the blades. The repair path and area for additive manufacturing of the blades are designed based on CAD software.

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

4. The electromagnetic coupling-assisted additive manufacturing and repair method for single crystal aero-engine blades according to claim 1, characterized in that: The S3 specifically includes: The blade is clamped at both ends of the electrode generating the pulse current by a clamp, and the blade is placed at the center of the pulse magnetic field. The direction of the clamp is adjusted to control the direction of the electric field and the magnetic field to be parallel to the blade axis. The magnetic field parameters of the first electromagnetic coupling treatment were 0.5T~1.0T, and the current density was 1×10 2 A / mm 2 ~3×10 2 A / mm 2 ; The number of electromagnetic coupling processing groups is 5 to 10 groups.

5. The electromagnetic coupling-assisted additive manufacturing and repair method for single crystal aero-engine blades according to claim 1, characterized in that: After the laser additive manufacturing of the blade is completed in S4, a metallographic microscope and an electron microscope are used to observe and determine the epitaxial growth direction of the dendrites in the laser additive manufacturing repair area.

6. The electromagnetic coupling-assisted additive manufacturing and repair method for single crystal aero-engine blades according to claim 1, characterized in that: The S5 specifically includes: The blade is clamped at both ends of the electrode generating the pulse current by a fixture, and the blade is placed at the center of the pulse magnetic field, with the directions of the electric field and the magnetic field being parallel to the epitaxial growth direction of the repair layer dendrite; The magnetic field parameters of the second electromagnetic coupling treatment were 1.0T~2.0T, and the current density was 3×10 2 A / mm 2 ~5×10 2 A / mm 2 ; The number of electromagnetic coupling processing groups is 10 to 20 groups.

7. The electromagnetic coupling-assisted additive manufacturing and repair method for single crystal aero-engine blades according to claim 1, characterized in that: The S6 specifically includes: spraying a large number of high-speed projectiles onto the surface of the blade repair area, and forming a residual compressive stress influence layer through the impact of small particles.

8. The electromagnetic coupling-assisted additive manufacturing and repair method for single crystal aero-engine blades according to claim 1, characterized in that: The 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.

9. The electromagnetic coupling-assisted additive manufacturing and repair method for single crystal aero-engine blades according to claim 1, characterized in that: The S8 specifically includes: The blade is clamped at both ends of the electrodes generating pulse current by a fixture, and the repaired area of ​​the blade after shot peening is placed at the center of the pulse magnetic field, with the directions of the electric field and the magnetic field parallel to the epitaxial growth direction of the repaired layer dendrites; The magnetic field parameters of the third electromagnetic coupling treatment were 1.0T~2.0T, and the current density was 5×10 2 A / mm 2 ~1×10 3 A / mm 2 ; The number of electromagnetic coupling processing groups is 10 to 20 groups.

Images