A laser cladding repair process for fatigue cracks on gear tooth surfaces

Abstract

The present application relates to a laser cladding repair process for fatigue cracks on gear tooth surfaces. A control system is used to detect the shape of the fatigue crack in real time. Different laser processing parameters are used for the straight segments and curved segments of the fatigue crack. In particular, a single laser beam is replaced with two laser beams for the curved segments of the fatigue crack, thereby effectively ensuring the welding quality of the entire fatigue crack. The fatigue crack welding efficiency is high, and the grain structure of the cladding area is uniform, thereby effectively improving the overall repair quality of the fatigue crack.

Description

Technical Field

[0001] The invention belongs to the field of laser repair, and more specifically, relates to a laser cladding repair process for fatigue cracks on gear tooth surfaces. Background Art

[0002] Gears are an important part of mechanical transmission systems. Continuous operation under high speed or high load conditions will cause gear failure and damage. The failure and damage forms of gears are determined by many factors such as lubrication conditions, working conditions, parts materials, heat treatment methods adopted in the manufacturing process, and parts manufacturing and installation processes. Gear failure can generally be divided into two categories: tooth body damage and tooth surface damage. Tooth body damage is tooth breakage, and tooth surface damage includes four types of plastic deformation of gear teeth, tooth surface bonding, wear and tooth surface fatigue.

[0003] Tooth surface fatigue is a common situation of tooth surface damage. Since the equivalent stress on the tooth surface of the gear is variable, when the bearing capacity on the tooth surface is greater than the alternating equivalent stress on the tooth surface material, fatigue cracks will occur in this part for a long time. For some equipment with precise structure and high manufacturing cost, direct replacement will cause great economic losses. For example, the production cost of high-precision gears and generator gears is high. Direct replacement of failed gears leads to excessive cost, while repair can significantly reduce maintenance costs. Currently, the repair processes on the market usually include spraying, electroplating, chemical plating, laser cladding and other methods. Laser cladding, as an emerging surface modification technology, is the most widely used in gear repair. Compared with traditional repair methods, it has the advantages of small heat-affected zone and high metallurgical bonding. Based on the actual production process, the fatigue cracks on the gear tooth surface are usually irregular in shape, with curves, corners and other shapes. During the cladding process, the convection, heat transfer and mass transfer generated by the liquid in the molten pool are affected by the temperature field, which affects the solidification and composition uniformity of the metal liquid in the molten pool, and further has a decisive influence on the surface quality of the cladding layer. However, the existing technology has not conducted in-depth research on laser processing technology, and generally uses the most common Gaussian spot to be incident on the area to be repaired.

[0004] Since the actual fatigue crack is irregular in shape, when the laser is incident on a curved path, the laser scanning speed at the curve or corner is slow. If the same laser spot, laser power and other parameters as the straight segment are still used, it will cause a mismatch between the laser heat source and the scanning speed, leading to welding overburning, coarse grains and other phenomena. Therefore, it is an important issue that needs to be urgently solved to modulate the appropriate laser spot, laser power, etc. according to the actual fatigue crack shape to improve the repair quality. Summary of the invention

[0005] The invention relates to a laser cladding repair process for gear tooth surface fatigue cracks, aiming to solve the problem of poor repair quality caused by overburning of laser cladding welds and coarse grains in the prior art of gear tooth surface fatigue cracks.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A laser cladding repair process for fatigue cracks on gear tooth surfaces, the laser cladding repair process adopts single-layer multi-pass welding, characterized in that: the fatigue cracks are straight line segments and curved segments, and the repair process comprises the following steps:

[0008] Step 1), the control system obtains the curvature of the fatigue crack on the gear tooth surface to be repaired, and when the control system detects that the current shape of the fatigue crack is a straight line segment, the laser transmitter emits a first wavelength laser beam with a laser power of 1800-2100W, and the first wavelength laser beam is incident on the straight line segment of the fatigue crack;

[0009] Step 2), the control system detects the curvature of the fatigue crack in real time. When the control system detects that the current shape of the fatigue crack is a curved segment, a laser processing process matching the curvature of the current curved segment is selected based on the database, the laser transmitter turns off the first wavelength laser beam and emits a second wavelength laser beam, the second wavelength laser beam is split into a completely identical split laser beam and another split laser beam by a spectroscope, the laser power of the split laser beam and the other split laser beam is 1500-1700W, and the split laser beam and the other split laser beam are incident on the fatigue crack curved segment;

[0010] Step 3), when the control system detects that the current shape of the fatigue crack is restored to a straight line segment, the laser transmitter turns off the second wavelength laser beam and emits the first wavelength laser beam, the laser power is 1800-2100W, and the first wavelength laser beam is incident on the fatigue crack straight line segment;

[0011] The database in step 2) is pre-modeled offline to achieve welding process data integration, and different curvatures of fatigue cracks correspond to different laser powers, laser spots, laser scanning speeds and powder feeding speeds.

[0012] Furthermore, the laser transmitter is a switchable multi-wavelength fiber laser, the gear material is 45 carbon structural steel, and the cladding layer alloy powder in the powder feeding channel includes components C, Cr, B, Si, Ni, and Fe, wherein the weight ratio of Fe is not less than 80%.

[0013] Furthermore, the first wavelength laser beam is 1064 nm, and the second wavelength laser beam is 1050 nm.

[0014] Furthermore, in step 1) and step 3), the laser defocusing amount is 0 to -20 mm, the laser scanning rate is 300-600 mm / min, the powder feeding rate is 30-50 g / min, and the angle α between the powder feeding channel (10) and the vertical direction is 30°-60°.

[0015] In step 2), the laser defocus is 0 to -20 mm, the laser scanning rate is 240-480 mm / min, the powder feeding rate is 24-40 g / min, and the angle α is 30°-60°.

[0016] Further, in step 1) and step 3), before the laser emitter emits a laser beam of a first wavelength, the control system controls the first linear light shaping unit to move horizontally out of the optical path; in step 2), before the laser emitter emits a laser beam of a second wavelength, the control system controls the second linear light shaping unit and the third linear light shaping unit to move horizontally out of the optical path; in step 1) and step 3), the spot of the first wavelength laser incident on the straight segment of the fatigue crack is a Gaussian laser spot A, and the laser spot A is circular with a diameter of 2-3 mm; in step 2), the second wavelength laser is a Gaussian laser beam, and the spot of the split laser beam and the other split laser beam incident on the fatigue crack curve segment after splitting is a Gaussian laser spot B, and the laser spot B is circular with a diameter of 1.8-2.7 mm.

[0017] According to another embodiment of the present application, in step 1) and step 3), before the laser emitter emits a laser beam of a first wavelength, the control system controls the first linear light shaping unit to move horizontally out of the optical path; in step 2), before the laser emitter emits a laser beam of a second wavelength, the control system controls the second linear light shaping unit and the third linear light shaping unit to move horizontally into the optical path; in step 1) and step 3), the spot of the first wavelength laser incident on the straight line segment of the fatigue crack is a Gaussian laser spot A, and the laser spot A is circular with a diameter of 2-3 mm; in step 2), the second wavelength laser is a Gaussian laser beam, and the one split laser beam is modulated by the second linear light shaping unit into a rectangular spot C incident on the fatigue crack curve segment, and the other split laser beam is also modulated by the third linear light shaping unit into a rectangular spot C incident on the fatigue crack curve segment, and the rectangular spot C has a width of 1-2 mm in the direction of advancement of the fatigue crack and a length perpendicular to the direction of advancement of the fatigue crack of 1.8-2.7 mm.

[0018] According to another embodiment of the present application, in step 1) and step 3), before the laser emitter emits a laser beam of a first wavelength, the control system controls the first linear light shaping unit to move horizontally into the optical path; in step 2), before the laser emitter emits a laser beam of a second wavelength, the control system controls the second linear light shaping unit and the third linear light shaping unit to move horizontally into the optical path; in step 1) and step 3), the first wavelength laser beam is a Gaussian laser beam, and the first wavelength laser beam is modulated by the first linear light shaping unit into a rectangular light spot D incident on the straight line segment of the fatigue crack, and the rectangular light spot D is at the fatigue The width of the crack in the advancing direction is 1-2 mm, and the length perpendicular to the advancing direction of the fatigue crack is 2-3 mm; in the step 2), the second wavelength laser beam is a Gaussian laser beam, and the one split laser beam is modulated by the second linear light shaping unit into a rectangular spot C incident on the fatigue crack curve segment, and the other split laser beam is also modulated by the third linear light shaping unit into a rectangular spot C incident on the fatigue crack curve segment, and the width of the rectangular spot C in the advancing direction of the fatigue crack is 1-2 mm, and the length perpendicular to the advancing direction of the fatigue crack is 1.8-2.7 mm.

[0019] Beneficial Effects

[0020] The laser cladding repair process for fatigue cracks on the gear tooth surface of the present application uses a control system to detect the shape of the fatigue crack in real time, and adopts different laser processing parameters for the straight segment and curved segment of the fatigue crack, thereby effectively ensuring the welding quality of the entire fatigue crack, with high welding efficiency and uniform grain structure in the cladding area, which effectively improves the overall repair quality of the fatigue crack. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the laser cladding repair equipment and gear tooth surface fatigue crack structure of this application;

[0022] Figure 2 Schematic diagram of circular Gaussian spot energy distribution;

[0023] Figure 3 Schematic diagram of rectangular linear spot energy distribution;

[0024] Figure 4 (a) is a schematic diagram of the first laser optical path of the present application; (b) is a schematic diagram of the second laser optical path of the present application; (c) is a schematic diagram of the third laser optical path of the present application.

[0025] In the figure,

[0026] 1. Laser generator; 2. Control system; 3. First wavelength laser beam; 4. Second wavelength laser beam; 5. Multifunctional lens; 5. Splitting laser beam; 6. Another splitting laser beam; 7. First linear light shaping unit; 8. Second linear light shaping unit; 9. Third linear light shaping unit; 10. Powder feeding channel; 11. Fatigue crack on gear tooth surface. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0028] As an emerging surface modification technology, laser cladding is the most widely used in gear repair. Compared with traditional repair methods, it has the advantages of small heat-affected zone and high metallurgical bonding. The quality of gear tooth surface fatigue crack repair depends on the welding quality of the cladding layer. There are many factors that affect the welding quality of the cladding layer. Generally, it is necessary to consider the cladding material, laser power, laser spot, scanning speed and powder feeding speed. Only when the above parameters match each other can a cladding layer with excellent welding performance be obtained.

[0029] Embodiment 1

[0030] See also Figure 1-4 (a) The embodiment of the present invention provides a laser cladding repair process for fatigue cracks on gear tooth surfaces, which specifically includes the following processes:

[0031] Step 1), the control system 2 obtains the curvature of the fatigue crack on the gear tooth surface to be repaired. When the control system detects that the current shape of the fatigue crack is basically a straight line segment, the laser transmitter 1 emits a first wavelength laser beam 3 with a laser power of 1800-2100W, and the first wavelength laser beam 3 is incident on the straight line segment of the fatigue crack 11;

[0032] Step 2), the control system 2 detects the curvature of the fatigue crack in real time. When the control system 2 detects that the current shape of the fatigue crack is a curved segment, a laser processing process matching the curvature of the current curved segment is selected based on the database, and the laser transmitter 1 turns off the first wavelength laser beam 3 and emits the second wavelength laser beam 4. The second wavelength laser beam 4 is split by a spectroscope (not shown) into a completely identical split laser beam 5 and another split laser beam 6. The laser powers of the split laser beam 5 and the another split laser beam 6 are 1500-1700W. The split laser beam 5 and the another split laser beam 6 are incident on the curved segment of the fatigue crack 11.

[0033] Step 3), when the control system 2 detects that the current shape of the fatigue crack is restored to a basically straight line segment, the laser transmitter 1 turns off the second wavelength laser beam 4 and emits the first wavelength laser beam 3, the laser power is 1800-2100W, and the first wavelength laser beam 3 is incident on the straight line segment of the fatigue crack 11;

[0034] The database in step 2) is pre-built offline to realize the integrated construction of welding process data, and different curvatures of fatigue cracks correspond to different laser powers, laser spots, laser scanning rates and powder feeding speeds.

[0035] In this embodiment, in step 2), when the fatigue crack detected is a curved segment, if the scanning speed is too high, it will cause the welding path to deviate and the welding jitter. Therefore, the laser scanning rate should be appropriately reduced at the curve or corner. After reducing the laser scanning rate, if a higher laser power is still used, it will lead to mismatch of process parameters, resulting in overburning of the cladding weld, coarse grains and other phenomena. Therefore, for the fatigue cracks in the curved segment, the welding speed and laser power are appropriately reduced, and in theory, a cladding layer with better welding quality can be obtained. On the other hand, in actual operation, if the welding speed and laser power are reduced, the welding efficiency will be slowed down. At the same time, the slower laser scanning rate will also affect the flow and uniformity of the molten pool. Therefore, modulating the two-beam laser beam can significantly improve the welding efficiency of the curved segment, and the simultaneous emission of the two-beam beam can improve the uniformity of the molten pool, thereby obtaining good welding quality.

[0036] In this embodiment, a single-layer multi-pass welding cladding repair method is adopted, the laser transmitter 1 is a switchable multi-wavelength fiber laser, the gear material is 45 carbon structural steel, and the cladding layer alloy powder in the powder feeding channel 10 includes components C, Cr, B, Si, Ni, and Fe, wherein the weight ratio of Fe is not less than 80%.

[0037] In this embodiment, the first wavelength laser beam 3 is 1064 nm, and the second wavelength laser beam 4 is 1050 nm.

[0038] In this embodiment, in the steps 1) and 3), the laser defocusing amount is 0 to -20 mm, the laser scanning rate is 300-600 mm / min, the powder feeding rate is 30-50 g / min, and the angle α between the powder feeding channel 10 and the vertical direction is 30°-60°; in the step 2), the laser defocusing amount is 0 to -20 mm, the laser scanning rate is 240-480 mm / min, the powder feeding rate is 24-40 g / min, and the angle α is 30°-60°.

[0039] Since the fatigue crack in step 2) is curved, the scanning rate is reduced by 20%, and the corresponding laser powder feeding rate and laser power are reduced at the same time, so that a better weld of the cladding layer can be obtained. Among them, since the reflectivity of metal materials is high, in order to improve the laser absorption rate, the laser can be set to a negative defocus amount.

[0040] Furthermore, the powder feeding method adopts pneumatic powder feeding, and pneumatic powder feeding can accurately control the powder feeding rate.

[0041] Furthermore, in order to avoid interference between the powder feeding channel and the laser incident head, the powder feeding inclination angle is set to 30°-60°.

[0042] Further, in this embodiment, in step 1) and step 3), before the laser emitter 1 emits the first wavelength laser beam 3, the control system 2 controls the first linear light shaping unit 7 to move horizontally out of the optical path; in step 2), before the laser emitter 1 emits the second wavelength laser beam 4, the control system 2 controls the second linear light shaping unit 8 and the third linear light shaping unit 9 to move horizontally out of the optical path; in the steps 1) and 3), the spot of the first wavelength laser 3 incident on the fatigue crack straight line segment is a Gaussian laser spot A, and the laser spot A is circular with a diameter of 2-3 mm; in the step 2), the second wavelength laser 4 is a Gaussian laser beam, and the spot of the split laser beam 5 and the other split laser beam 6 incident on the fatigue crack curve segment is a Gaussian laser spot B, and the laser spot B is circular with a diameter of 1.8-2.7 mm.

[0043] In this embodiment, the first wavelength laser beam 3 in step 1) and step 3) and the two split laser beams in step 2) are all Gaussian spots. The Gaussian spot is generally a common circular heat source distribution. The heat source is in the form of high energy in the middle and low energy at the edge. The energy is Gaussian distributed. The Gaussian spot is relatively simple to shape. Figure 2 In step 2), the heat accumulation effect of the fatigue crack curve segment is more obvious. Therefore, in order to make the grain structure at the boundary of the cladding weld more uniform, the Gaussian laser spot diameter in step 2) is reduced by 10% compared with the Gaussian laser spot diameter in step 1), and the diameter is about 1.8-2.7 mm. The reduced spot diameter can improve the welding quality at the boundary of the cladding area.

[0044] Embodiment 2

[0045] See also Figure 1-Figure 4 (b) This embodiment is an improvement on the first embodiment. For matters not covered in this embodiment, please refer to the description in the first embodiment.

[0046] In this embodiment, in step 1) and step 3), before the laser emitter 1 emits the first wavelength laser beam 3, the control system 2 controls the first linear light shaping unit 7 to move horizontally out of the optical path; in step 2), before the laser emitter 1 emits the second wavelength laser beam 4, the control system 2 controls the second linear light shaping unit 8 and the third linear light shaping unit 9 to move horizontally into the optical path; in the steps 1) and 3), the spot of the first wavelength laser 3 incident on the straight line segment of the fatigue crack is a Gaussian laser spot A, and the laser spot A is circular with a diameter of 2-3 mm; in the step 2), the second wavelength laser 4 is a Gaussian laser beam, the one split laser beam 5 is modulated by the second linear light shaping unit 8 into a rectangular spot C incident on the fatigue crack curve segment, and the other split laser beam 6 is also modulated by the third linear light shaping unit 9 into a rectangular spot C incident on the fatigue crack curve segment, and the width of the rectangular spot C in the advancing direction of the fatigue crack is 1-2 mm, and the length perpendicular to the advancing direction of the fatigue crack is 1.8-2.7 mm.

[0047] In this embodiment, the spot of the first wavelength laser beam 3 incident on the straight segment of the fatigue crack in step 1) and step 3) is a Gaussian laser spot A. The Gaussian laser spot A is circular in size with a diameter of 2-3 mm. The laser shaping is simple and the cladding weld has good flatness.

[0048] Due to the complexity of curved section welding, in order to obtain better welding performance, the energy distribution of the laser is also required to be high. Therefore, a rectangular linear spot with uniform energy distribution is used at the curve. Figure 3 , which can significantly improve the uniformity of the grain structure of the cladding layer in the fatigue crack curve segment. In step 2), one split laser beam 5 and another split laser beam 6 are modulated to form a rectangular spot C, and the rectangular cladding weld has a higher uniformity of grain structure. In addition, the length of the rectangular spot C in step 2) is reduced by 10% compared to the diameter of the laser spot A in step 1). The appropriately reduced rectangular spot can significantly reduce the heat accumulation at the boundary of the cladding area, thereby further improving the welding quality.

[0049] Embodiment 3

[0050] See also Figure 1-Figure 4 (c) This embodiment is an improvement on the first embodiment. For matters not covered in this embodiment, please refer to the description in the first embodiment.

[0051] In step 1) and step 3), before the laser emitter 1 emits the first wavelength laser beam 3, the control system 2 controls the first linear light shaping unit 7 to move horizontally into the optical path; in step 2), before the laser emitter 1 emits the second wavelength laser beam 4, the control system 2 controls the second linear light shaping unit 8 and the third linear light shaping unit 9 to move horizontally into the optical path; in step 1) and step 3), the first wavelength laser beam 3 is a Gaussian laser beam, and the first wavelength laser beam 3 is modulated by the first linear light shaping unit 7 to be incident on the straight line segment of the fatigue crack, and the rectangular light spot D is at the fatigue crack. The width in the advancing direction is 1-2 mm, and the length perpendicular to the advancing direction of the fatigue crack is 2-3 mm; in the step 2), the second wavelength laser beam 4 is a Gaussian laser beam, the one split laser beam 5 is modulated by the second linear light shaping unit 8 into a rectangular spot C incident on the fatigue crack curve segment, and the other split laser beam 6 is also modulated by the third linear light shaping unit 9 into a rectangular spot C incident on the fatigue crack curve segment, and the width of the rectangular spot C in the advancing direction of the fatigue crack is 1-2 mm, and the length perpendicular to the advancing direction of the fatigue crack is 1.8-2.7 mm.

[0052] In this embodiment, the first wavelength laser beam 3 in step 1) and step 3) and the split laser beam 5 and the other split laser beam 6 in step 2) are all modulated into rectangular spots, and the rectangular spots are selected for the cladding path of the entire fatigue crack, which can greatly improve the uniformity of the grain structure of the cladding weld.

[0053] The rectangular spot D in step 1) has a width of 1-2mm along the advancing direction of the weld and a length of 2-3mm perpendicular to the advancing direction of the weld. The rectangular spot C in step 2) has a width of 1-2mm in the advancing direction of the fatigue crack and a length of 1.8-2.7mm perpendicular to the advancing direction of the fatigue crack. This is because the heat accumulation effect of the curve section is more obvious. Therefore, in order to make the grain structure at the boundary of the cladding weld more uniform, the length of the rectangular spot C in step 2) is reduced by 10% compared with the rectangular spot D in step 1). The appropriately reduced rectangular spot can significantly reduce the heat accumulation at the boundary of the cladding area, thereby further improving the welding quality.

Claims

1. A laser cladding repair process for fatigue cracks on gear tooth surfaces, the laser cladding repair process adopts single-layer multi-pass welding, and is characterized by: The fatigue crack is in the form of straight line segments and curved line segments, and the repair process comprises the following steps: Step 1), the control system (2) obtains the curvature of the fatigue crack on the gear tooth surface to be repaired, and when the control system (2) detects that the current shape of the fatigue crack is a straight line segment, the laser transmitter (1) emits a first wavelength laser beam (3), the laser power is 1800-2100W, and the first wavelength laser beam (3) is incident on the straight line segment of the fatigue crack (11); Step 2), the control system (2) detects the curvature of the fatigue crack in real time. When the control system (2) detects that the current shape of the fatigue crack is a curved segment, a laser processing process matching the curvature of the current curved segment is selected based on the database, the laser transmitter (1) turns off the first wavelength laser beam (3) and emits the second wavelength laser beam (4), the second wavelength laser beam (4) is split by a beam splitter into a completely identical split laser beam (5) and another split laser beam (6), the laser power of the split laser beam (5) and the other split laser beam (6) being 1500-1700W, and the split laser beam (5) and the other split laser beam (6) are incident on the curved segment of the fatigue crack (11); Step 3), when the control system (2) detects that the current shape of the fatigue crack has recovered to a straight line segment, the laser transmitter (1) turns off the second wavelength laser beam (4) and transmits the first wavelength laser beam (3), the laser power is 1800-2100W, and the first wavelength laser beam (3) is incident on the straight line segment of the fatigue crack (11); The database in step 2) is pre-modeled offline to achieve integration of welding process data, and different curvatures of fatigue cracks correspond to different laser powers, laser spots, laser scanning rates and powder feeding rates.

2. The repair process according to claim 1, characterized in that: The laser transmitter (1) is a switchable multi-wavelength fiber laser, the gear material is 45# carbon structural steel, and the cladding layer alloy powder in the powder feeding channel (10) includes components C, Cr, B, Si, Ni, and Fe, wherein the weight ratio of Fe is not less than 80%.

3. The repair process according to claim 2, characterized in that: The first wavelength laser beam (3) is 1064 nm, and the second wavelength laser beam (4) is 1050 nm.

4. The repair process according to claim 3, characterized in that: In the steps 1) and 3), the laser defocusing amount is 0 to -20 mm, the laser scanning rate is 300-600 mm / min, the powder feeding rate is 30-50 g / min, and the angle α between the powder feeding channel (10) and the vertical direction is 30°-60°; In step 2), the laser defocus is 0 to -20 mm, the laser scanning rate is 240-480 mm / min, the powder feeding rate is 24-40 g / min, and the angle α is 30°-60°.

5. The repair process according to claim 4, characterized in that: In step 1) and step 3), before the laser emitter (1) emits the first wavelength laser beam (3), the control system (2) controls the first linear light shaping unit (7) to move horizontally out of the optical path; In step 2), before the laser emitter (1) emits the second wavelength laser beam (4), the control system (2) controls the second linear light shaping unit (8) and the third linear light shaping unit (9) to move horizontally out of the optical path; In the steps 1) and 3), the spot of the first wavelength laser beam (3) incident on the straight line segment of the fatigue crack is a Gaussian laser spot A, and the laser spot A is circular with a diameter of 2-3 mm; in the step 2), the second wavelength laser beam (4) is a Gaussian laser beam, and the spot of the split laser beam (5) and the other split laser beam (6) incident on the curved line segment of the fatigue crack is a Gaussian laser spot B, and the laser spot B is circular with a diameter of 1.8-2.7 mm.

6. The repair process according to claim 4, characterized in that: In step 1) and step 3), before the laser emitter (1) emits the first wavelength laser beam (3), the control system (2) controls the first linear light shaping unit (7) to move horizontally out of the optical path; In step 2), before the laser emitter (1) emits the second wavelength laser beam (4), the control system (2) controls the second linear light shaping unit (8) and the third linear light shaping unit (9) to move horizontally into the optical path; In the steps 1) and 3), the spot of the first wavelength laser (3) incident on the fatigue crack straight line segment is a Gaussian laser spot A, and the laser spot A is circular with a diameter of 2-3 mm; in the step 2), the second wavelength laser (4) is a Gaussian laser beam, the one split laser beam (5) is modulated by the second linear light shaping unit (8) into a rectangular spot C incident on the fatigue crack curve segment, and the other split laser beam (6) is also modulated by the third linear light shaping unit (9) into a rectangular spot C incident on the fatigue crack curve segment, and the rectangular spot C has a width of 1-2 mm in the fatigue crack advancing direction and a length of 1.8-2.7 mm perpendicular to the fatigue crack advancing direction.

7. The repair process according to claim 4, characterized in that: In step 1) and step 3), before the laser emitter (1) emits the first wavelength laser beam (3), the control system (2) controls the first linear light shaping unit (7) to move horizontally into the optical path; In step 2), before the laser emitter (1) emits the second wavelength laser beam (4), the control system (2) controls the second linear light shaping unit (8) and the third linear light shaping unit (9) to move horizontally into the optical path; In the step 1) and the step 3), the first wavelength laser beam (3) is a Gaussian laser beam, and the first wavelength laser beam (3) is modulated by a first linear light shaping unit (7) into a rectangular light spot D incident on the straight line segment of the fatigue crack, and the width of the rectangular light spot D in the direction of the fatigue crack is 1-2 mm, and the length perpendicular to the direction of the fatigue crack is 2-3 mm; in the step 2), the second wavelength laser beam (4) is a Gaussian laser beam, and the one split laser beam (5) is modulated by a second linear light shaping unit (8) into a rectangular light spot C incident on the fatigue crack curve segment, and the other split laser beam (6) is also modulated by a third linear light shaping unit (9) into a rectangular light spot C incident on the fatigue crack curve segment, and the width of the rectangular light spot C in the direction of the fatigue crack is 1-2 mm, and the length perpendicular to the direction of the fatigue crack is 1.8-2.7 mm.

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