A laser shock combined strengthening process for improving bearing contact fatigue performance

Abstract

The application provides a laser shock combined strengthening process for improving bearing contact fatigue performance, first, a machining allowance layer is reserved on the raceway surface of the bearing; then a protective layer is attached; then large-spot laser shock is performed to form a first plastic strengthening layer; further micro-scale laser shock is performed to form a second plastic strengthening layer on the superficial layer of the first plastic strengthening layer; finally, the reserved machining allowance layer is removed. The process forms a large-depth first plastic strengthening layer on the surface of the raceway area through large-spot laser shock, and on this basis, a relatively shallow second plastic strengthening layer is formed on the surface through micro-scale laser shock, the secondary strengthening can improve the performance of the strengthened area, and more importantly, the smoothness and plastic deformation uniformity of the plastic strengthening layer can be optimized; then the strengthened area is removed and polished by a certain thickness to ensure that the smoothness of the raceway surface meets the relevant technical requirements, thereby finally significantly improving the rolling contact fatigue performance of the bearing.

Description

Technical Field

[0001] This invention relates to the field of laser shock peening technology, and in particular to a combined laser shock peening process for improving the contact fatigue performance of bearings. Background Technology

[0002] High-end bearings used in aircraft engines, gas turbines, steam turbines, high-speed trains, and other equipment are facing increasingly stringent performance requirements as overall equipment specifications improve. These requirements are evolving towards higher DN values, higher temperature environments, heavy loads, longer lifespans, and higher reliability. As the supporting and transmission components of the entire rotor system, bearings are prone to wear and scratches, contact fatigue fractures, jamming, and seizure, which can severely impact the operational safety of rotating equipment.

[0003] During bearing operation, rollers roll at high speed and under heavy load on the raceway, making contact fatigue failure of the raceway surface material unavoidable. This is especially true when the raceway surface is damaged, such as by wear or scratches, which further accelerates the initiation of contact fatigue cracks and the fracture process. Therefore, effectively modifying the bearing raceway surface to improve its rolling contact fatigue performance is crucial.

[0004] Laser shock peening technology ( Laser Shock Peening LSP (Laser-Based Plasticity Enhancement) is a surface plasticity enhancement technology that uses short pulses (nanosecond level) and high power (GW / cm²). 2 The interaction between a high-pressure (GPa level) laser and matter generates a high-pressure plasma shock wave. The mechanical effect of the shock wave causes plastic deformation of the surface layer of the metal material, forming residual compressive stress and improving the microstructure, thereby significantly improving the fatigue performance of the material.

[0005] However, like traditional mechanical shot peening, laser shock peening creates numerous plastic deformation pits within the treated area, increasing surface roughness and compromising the uniformity of plastic deformation. For high-end bearings, where raceways operate under high-speed, heavy-load conditions for extended periods, extremely high surface finish is required. High surface roughness or uneven material hardness can accelerate contact fatigue failure of the bearing raceway.

[0006] Therefore, applying laser shock peening to the raceway of high-end bearings urgently requires an innovative and engineering-feasible process that takes into account multiple aspects. On the one hand, it is necessary to ensure the degree and depth of plastic deformation, and on the other hand, it is necessary to eliminate the problems of increased surface roughness and uniformity of plastic deformation, so as to significantly improve the rolling contact fatigue performance of the bearing. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the object of the present invention is:

[0008] Firstly, a laser-shock combined strengthening process for improving the contact fatigue performance of bearings is provided, the key of which lies in the preparation according to the following steps:

[0009] S1. Pre-machining: A machining allowance layer is reserved on the raceway surface of the bearing, and the thickness of the raceway is [missing information]. d The thickness of the machining allowance layer is d 0;

[0010] S2, Covering Protection: An absorbent protective layer is applied to the raceway surface of the bearing, and a restraint layer is applied to the surface of the absorbent protective layer;

[0011] S3, Large-spot laser shock: A large-spot laser shock is used to enhance the rolling track area, forming a depth of... d The first plastic reinforcement layer of 1 d 1> d 0;

[0012] S4. Microscale Laser Shock: A constraint layer is directly applied to the surface of the first plastic strengthening layer, without the need for an absorbing protective layer. Microscale laser shock is used to strengthen the raceway region, forming a depth of [missing information]. d 2. The second plastic reinforcement layer, d 1> d 2> d 0;

[0013] S5. Remove the reserved machining allowance layer.

[0014] In conjunction with the first aspect, in one implementation, the depth of the first plastic reinforcement layer d 1 represents the thickness of the raceway. d 0.1 to 0.3 times that.

[0015] In conjunction with the first aspect, in one implementation, the energy of the large-spot laser shock is greater than the energy of the micro-scale laser shock; the spot diameter of the large-spot laser shock is greater than the spot diameter of the micro-scale laser shock; the pulse width of the large-spot laser shock is greater than the pulse width of the micro-scale laser shock; and the repetition frequency of the large-spot laser shock is less than the repetition frequency of the micro-scale laser shock.

[0016] In conjunction with the first aspect, in one implementation, the energy of the large-spot laser shock is 2~25J, the spot diameter is 1~3mm, the pulse width is 20~50ns, and the repetition frequency is 1~20Hz.

[0017] In conjunction with the first aspect, in one implementation, the depth of the first plastic reinforcement layer is 1~2mm, forming a plastic reinforcement layer with high surface elevation and large cross-sectional depth.

[0018] In combination with the first aspect, in an implementation manner, the micro-scale laser shock has an energy of 10-500 mJ, a spot diameter of 100-500 μm, a pulse width of 5-10 ns, and a repetition frequency of 100-1000 Hz.

[0019] In combination with the first aspect, in an implementation manner, the second plastic strengthening layer has a depth of 0.4-0.6 mm. The mechanical properties and the uniformity of the microstructure of the plastic strengthening layer are significantly improved.

[0020] In combination with the first aspect, in an implementation manner, the absorbing protective layer is a black adhesive tape, and the constraint layer is a water curtain formed by applying deionized water.

[0021] In combination with the first aspect, in an implementation manner, the machining allowance layer reserved for removal is machined and removed from the surface of the raceway by a fine grinding and polishing process.

[0022] The second aspect further provides a bearing machining process, which is characterized by comprising the laser shock combined strengthening process for improving the contact fatigue performance of a bearing according to any one of the implementation manners of the first aspect.

[0023] As described above, the laser shock combined strengthening process for improving the contact fatigue performance of a bearing according to the application at least has the following beneficial effects: a first plastic strengthening layer with a large depth is formed on the surface of the raceway area by large-spot laser shock, and on this basis, a second plastic strengthening layer with a smaller depth is formed on the surface by micro-scale laser shock, the secondary strengthening can improve the performance of the strengthened area, and more importantly, can optimize the smoothness and plastic deformation uniformity of the plastic strengthening layer; and then a certain thickness of the strengthened area is removed and finished to ensure that the smoothness of the surface of the raceway meets the relevant technical requirements, thereby finally significantly improving the rolling contact fatigue performance of the bearing. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1 is a schematic diagram of the process of the application for machining a bearing; wherein 1 is a bearing raceway, 2 is an absorbing protective layer, 3 is a constraint layer, 4 is a large-spot laser shock wave, and 5 is a micro-scale laser shock wave.

[0025] Fig. 2 is a process flow diagram of the application;

[0026] Figure 3 Depth distribution curves of residual compressive stress under different strengthening processes;

[0027] Figure 4 Transmission electron microscope images of surface microstructures under different strengthening processes (wherein a is an original state, b is a strengthening result of a traditional process, and c is a strengthening result of the laser shock combined strengthening process of the application);

[0028] Figure 5The results are from contact fatigue performance tests under different strengthening processes. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0030] First, the technical solution of this invention provides a laser shock combined strengthening process for improving the contact fatigue performance of bearings, which is prepared according to the following steps:

[0031] S1. Pre-machining: A machining allowance layer is reserved on the raceway surface of the bearing, and the thickness of the raceway is [missing information]. d The thickness of the machining allowance layer is d 0; This allows for sufficient machining redundancy in the later finishing processes.

[0032] S2. Protective coating: An absorbent protective layer is applied to the raceway surface of the bearing, and a constraint layer is applied to the surface of the absorbent protective layer.

[0033] S3, Large-spot laser shock: A large-spot laser shock is used to enhance the rolling track area, forming a depth of... d The first plastic reinforcement layer of 1 d 1> d 0; The depth of the first plastic strengthening layer is on the millimeter level, which means that a deep strengthening and hardening layer is obtained, and residual compressive stress and hardness with high amplitude and gradient distribution are formed on the surface at the depth.

[0034] S4. Microscale Laser Shock: A constraint layer is directly applied to the surface of the first plastic strengthening layer without the need for an absorbing protective layer. Microscale laser shock is used to strengthen the raceway region, forming a depth of [missing information]. d 2. The second plastic reinforcement layer, d 1> d 2> d 0; that is, a second plastic strengthening layer is formed in the shallow layer of the first plastic strengthening layer, which makes the surface grain structure highly refined, and makes the surface distribution of residual compressive stress, hardness, etc. more uniform, ensuring the uniformity of surface strengthening / hardening.

[0035] S5. Remove the reserved machining allowance layer, because d 1> d 2> d0. Therefore, after removing the machining allowance layer, the raceway reinforcement area retains only the first plastic reinforcement layer and forms a second plastic reinforcement layer in the shallow layer of the first plastic reinforcement layer. The surface can be treated to achieve the desired surface finish.

[0036] It should be further clarified that large-spot laser shock and micro-scale laser shock are relative concepts based on the difference in strengthening depth of laser shock technology. Large-spot laser shock forms a deeper plastic strengthening layer and has a larger spot size than micro-scale laser shock.

[0037] In some embodiments, the depth of the first plastic reinforcement layer d 1 represents the thickness of the raceway. d The reinforcement depth is 0.1 to 0.3 times that of the bearing. This ratio provides a good strengthening effect without causing excessive plastic deformation that could lead to overall bearing deformation.

[0038] In some embodiments, the energy of the large-spot laser shock is greater than that of the micro-scale laser shock; the spot diameter of the large-spot laser shock is greater than that of the micro-scale laser shock; the pulse width of the large-spot laser shock is greater than that of the micro-scale laser shock; and the repetition frequency of the large-spot laser shock is less than that of the micro-scale laser shock. By combining high-energy, large-spot, long-pulse-width, low-repetition-frequency processing methods with low-energy, small-spot, short-pulse-width, high-repetition-frequency processing methods, a deep strengthening / hardening layer can be obtained while ensuring the uniformity of surface strengthening / hardening, thus improving contact fatigue performance from both factors.

[0039] On the one hand, based on energy conservation considerations, and on the other hand, based on the actual application of bearing processing, it is necessary to optimize the relevant parameters of large-spot laser shock to ensure that the strengthening and hardening effect is achieved without wasting excessive energy and resources. Therefore, in some embodiments, the energy of the large-spot laser shock is 2~25J, the spot diameter is 1~3mm, the pulse width is 20~50ns, and the repetition frequency is 1~20Hz. In some embodiments, the depth of the first plastic strengthening layer is 1~2mm.

[0040] As mentioned above, to ensure the strengthening and hardening effect is achieved without wasting excessive energy and resources, in some embodiments, the energy of the microscale laser shock is 10~500mJ, the spot diameter is 100~500μm, the pulse width is 5~10ns, and the repetition frequency is 100~1000Hz. In some embodiments, the depth of the second plastic strengthening layer is 0.4~0.6mm, which significantly improves the mechanical properties and microstructure uniformity of the plastic strengthening layer.

[0041] In some embodiments, the absorbent protective layer is black tape; the constraint layer is a water curtain formed by applying deionized water.

[0042] In some embodiments, the removing the reserved machining allowance layer adopts a fine grinding and polishing process to machine and remove the machining allowance layer of the raceway surface. A certain thickness of the reinforced area is removed and finished, and the material surface damage layer is removed, so as to ensure that the raceway surface finish meets the relevant technical requirements.

[0043] Secondly, a bearing machining process is also provided, which comprises the laser shock combined strengthening process for improving the bearing contact fatigue performance in any of the above embodiments. Preferably, the laser shock combined strengthening process is arranged between the bearing mechanical machining processes and between the rough grinding and fine grinding, so that the application of the raceway laser shock strengthening can be realized, and the surface finish and other requirements of the raceway can be ensured, and the engineering applicability is good.

[0044] The application will be described in detail below through specific example embodiments. It should also be understood that the following embodiments are only used to specifically describe the application, and cannot be understood as limiting the protection scope of the application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the application all belong to the protection scope of the application. The specific process parameters and the like described below are only one example in the appropriate range, i.e. those skilled in the art can select within the appropriate range through the description herein, and are not limited to the specific values of the examples below.

[0045] Example 1: A combined strengthening process is carried out on a main bearing of a certain type of aero-engine, the material of which is M50 steel, the raceway width is 30 mm, and the raceway thickness is 10 mm. The specific implementation process is as follows:

[0046] (1) The bearing blank is subjected to mechanical machining such as cutting and turning, and is subjected to rough grinding process on a grinding machine. The process is stopped when the raceway thickness size is 10.2 mm, and a processing allowance layer with a thickness of 0.2 mm is reserved. d 0 is reserved.

[0047] (2) Black adhesive tape is used as an absorption protective layer and is attached to the surface of the bearing raceway. Then the bearing is fixed on a 5-axis robot arm. Subsequently, deionized water flow is applied to the raceway area through a universal joint water pipe to form a water curtain with a thickness of 1-2 mm on the raceway surface as a constraint layer.

[0048] (3) The posture of the robot arm is adjusted so that the bearing raceway faces the fixed light path outlet. Then, the pulse laser parameters are set through a laser shock strengthening integrated control system. The laser energy is 25 J, the spot diameter is 3 mm, the pulse width is 50 ns, and the repetition frequency is 20 Hz. At this time, the laser power density is 7.08 GW / cm 2 , and the spot lap joint scheme and implementation path of the entire raceway are designed, and the process task is formulated.

[0049] (4) Start the traditional laser shock peening system to process the bearing raceway area, and form a deep plastic strengthening / hardening layer with a depth of 2 mm d 1 is a first plastic strengthening layer with a thickness of 2 mm, which is preformed with a high amplitude residual compressive stress, and the maximum residual compressive stress can reach 700 MPa or above, and the microhardness can be increased by 20% or above.

[0050] (5) Fix the strengthened bearing on the micro-scale laser shock peening system, tear off the black tape used in the previous process, and do not use any absorption protective layer.

[0051] (6) Set the pulse laser parameters on the micro-scale laser shock peening system, the laser energy is 500 mJ, the spot diameter is 500 μm, the pulse width is 10 ns, and the repetition frequency is 1000 Hz, at this time the laser power density is 25.48 GW / cm 2 , and the spot lap scheme and implementation path for the entire raceway are designed, and the process task is formulated.

[0052] (7) The bearing raceway is processed by micro-scale laser shock peening in the form of water and light in the same way, and laser ablation will occur on the raceway surface, the ablation layer is several microns, but a high degree of grain refinement can be formed within a depth of 2 mm d 2, even reaching the level of nanocrystalline structure, and a high uniform plastic deformation is formed, making the mechanical properties such as residual compressive stress and hardness more uniform, and the numerical fluctuation value is controlled within 10%.

[0053] (8) Finally, the bearing raceway is processed by precision grinding, polishing and other processes to remove the processing allowance d 0, so that the thickness of the bearing raceway d is 10 mm, and the surface finish also meets the relevant technical requirements.

[0054] (9) The combined strengthening process method forms a large-depth plastic strengthening / hardening layer through a large-energy, large-spot, long-pulse-width, and low-repetition-frequency process method, forms a high-uniformity plastic strengthening / hardening layer in the shallow surface layer through a small-energy, small-spot, short-pulse-width, and high-repetition-frequency process method, and ensures that the surface finish meets the relevant technical requirements through precision grinding, polishing and other processes, thereby more significantly improving the rolling contact fatigue performance of the bearing.

[0055] Example 2: Take a certain type of aero-engine main bearing as an example to perform the combined strengthening process, the material of which is M50 steel, the raceway width is 30 mm, and the raceway thickness is 10 mm. The specific implementation process is as follows:

[0056] (1) The bearing blank is subjected to cutting, turning and other mechanical processing, and the rough grinding process is performed on the grinding machine, and the process is stopped when the raceway thickness size is 10.2 mm, and the processing allowance d 0 is 0.2 mm.

[0057] (2) Black tape is used as an absorption protective layer and is attached to the bearing raceway surface. The bearing is then fixed on a 5-axis robot arm. Subsequently, deionized water is applied to the raceway area through a universal joint pipe to ensure that a water curtain of 1-2 mm is formed on the raceway surface, serving as a constraint layer.

[0058] (3) The bearing raceway is adjusted to face the fixed light path outlet by adjusting the robot arm posture. The pulse laser parameters are set through a laser shock peening integrated control system. The laser energy is 2 J, the spot diameter is 1 mm, the pulse width is 20 ns, and the repetition frequency is 1 Hz. At this time, the laser power density is 12.74 GW / cm 2 , and the entire raceway is designed for spot lap joint scheme and implementation path, and process tasks are formulated.

[0059] (4) The conventional laser shock peening system is started to process the bearing raceway area. A first plastic strengthening layer of 1 mm in depth d 1 is formed on the raceway area, which preforms high amplitude residual compressive stress, with a maximum residual compressive stress of more than 800 MPa, and improves the microhardness by more than 30%.

[0060] (5) The strengthened bearing is fixed to the micro-scale laser shock peening system, and the black tape used in the previous process is removed. No absorption protective layer is used.

[0061] (6) The pulse laser parameters are set on the micro-scale laser shock peening system. The laser energy is 10 mJ, the spot diameter is 100 μm, the pulse width is 5 ns, and the repetition frequency is 100 Hz. At this time, the laser power density is 25.48 GW / cm 2 , and the entire raceway is designed for spot lap joint scheme and implementation path, and process tasks are formulated.

[0062] (7) The bearing raceway is processed by micro-scale laser shock peening in a water-light same path mode. Laser ablation occurs on the raceway surface, with an ablation layer of several microns. However, a high degree of grain refinement, even reaching the level of nanocrystalline structure, is formed within a depth d 2 of 600 μm, and a high uniform plastic deformation is formed, making the distribution of residual compressive stress, hardness, and other mechanical properties more uniform, with a numerical fluctuation value controlled within 10%.

[0063] (8) Finally, the bearing raceway is processed by precision grinding, polishing, and other processes to remove the processing allowance d 0, so that the bearing raceway thickness size d is 10 mm, and the surface finish also meets the relevant technical requirements.

[0064] (9) The combined strengthening process method forms a deep plastic strengthening / hardening layer by using high energy, large spot size, long pulse width and low repetition frequency process method; and forms a highly uniform plastic strengthening / hardening layer on the shallow surface by using low energy, small spot size, short pulse width and high repetition frequency process method; and then ensures that the surface finish meets the relevant technical requirements by fine grinding, polishing and other processes, thereby significantly improving the rolling contact fatigue performance of the bearing.

[0065] Example 3: Taking a certain type of aero-engine main bearing as an example, a combined strengthening process is implemented. The material is M50 steel, the raceway width is 30mm, and the raceway thickness is 10mm. The specific implementation process is as follows:

[0066] (1) The bearing blank is machined by cutting, turning and other machining processes, and then rough grinding is performed on a grinding machine. The grinding is stopped when the raceway thickness is 10.2mm, leaving a thickness allowance. d 0 represents a machining allowance layer of 0.2 mm.

[0067] (2) Use black tape as an absorbent protective layer, apply it to the bearing raceway surface, then fix the bearing on the 5-axis robot arm, and then apply deionized water flow to the raceway area through the universal water-saving pipe to ensure that a 1~2mm water curtain is formed on the raceway surface as a constraint layer.

[0068] (3) By adjusting the posture of the robot arm, the bearing raceway is made to face the fixed optical path exit. Then, the pulsed laser parameters are set through the laser shock enhancement integrated control system. The laser energy is 10J, the spot diameter is 3mm, the pulse width is 20ns, and the repetition frequency is 5Hz. At this time, the laser power density is 7.08GW / cm². 2 Furthermore, the design of the entire raceway's light spot overlap scheme and implementation path was formulated, along with the development of process tasks.

[0069] (4) Activate the traditional laser shock peening system to treat the bearing raceway area and form a deep layer in the raceway area. d 1 is a 1.2mm first plastic reinforcement layer, pre-stressed with high amplitude residual compressive stress, the maximum residual compressive stress can reach more than 700MPa, and its microhardness can be increased by more than 20%.

[0070] (5) Fix the reinforced bearing onto the microscale laser shock strengthening system, remove the black tape used in the previous process, and no longer use any absorption protective layer.

[0071] (6) On the microscale laser shock peening system, the pulsed laser parameters were set as follows: laser energy of 50 mJ, spot diameter of 300 μm, pulse width of 5 ns, and repetition frequency of 500 Hz. At this time, the laser power density was 14.15 GW / cm². 2 Furthermore, the design of the entire raceway's light spot overlap scheme and implementation path was formulated, along with the development of process tasks.

[0072] (7) Microscale laser shock peening treatment of bearing raceways is performed using a water-laser co-path method. Laser ablation will occur on the raceway surface, and the ablation layer is a few micrometers in size, but it can reach a depth of d 2. High degree of grain refinement, even reaching the level of nanocrystalline structure, is formed within 400μm, and highly uniform plastic deformation is formed, so that the distribution of mechanical properties such as residual compressive stress and hardness is more uniform, and the numerical fluctuation value is controlled within 10%.

[0073] (8) Finally, the bearing raceway is subjected to precision grinding, polishing and other processes to remove machining allowances. d 0, making the bearing raceway thickness dimension d The thickness is 10mm, and the surface finish also meets the relevant technical requirements.

[0074] (9) The combined strengthening process method forms a deep plastic strengthening / hardening layer by using high energy, large spot size, long pulse width and low repetition frequency process method; and forms a highly uniform plastic strengthening / hardening layer on the shallow surface by using low energy, small spot size, short pulse width and high repetition frequency process method; and then ensures that the surface finish meets the relevant technical requirements by fine grinding, polishing and other processes, thereby significantly improving the rolling contact fatigue performance of the bearing.

[0075] Comparative Example 1: Taking a certain type of aero-engine main bearing as an example, it is strengthened using traditional processes. The material is M50 steel, the raceway width is 30mm, and the raceway thickness is 10mm. The specific implementation process is as follows:

[0076] (1) The bearing blank is machined by cutting, turning and other machining processes, and then rough grinding is performed on a grinding machine. The grinding is stopped when the raceway thickness is 10.2mm, leaving a thickness allowance. d 0 represents a machining allowance layer of 0.2 mm.

[0077] (2) Use black tape as an absorbent protective layer, apply it to the bearing raceway surface, then fix the bearing on the 5-axis robot arm, and then apply deionized water flow to the raceway area through the universal water-saving pipe to ensure that a 1~2mm water curtain is formed on the raceway surface as a constraint layer.

[0078] (3) By adjusting the posture of the robot arm, the bearing raceway is made to face the fixed optical path exit. Then, the pulsed laser parameters are set through the laser shock enhancement integrated control system. The laser energy is 10J, the spot diameter is 3mm, the pulse width is 20ns, and the repetition frequency is 5Hz. At this time, the laser power density is 7.08GW / cm². 2 Furthermore, the design of the entire raceway's light spot overlap scheme and implementation path was formulated, along with the development of process tasks.

[0079] (4) Activate the traditional laser shock peening system to treat the bearing raceway area and form a deep layer in the raceway area. d 1 is a 1.2mm first plastic reinforcement layer, pre-stressed with high amplitude residual compressive stress, the maximum residual compressive stress can reach more than 700MPa, and its microhardness can be increased by more than 20%.

[0080] (5) Finally, the bearing raceway is subjected to precision grinding, polishing and other processes to remove machining allowances. d 0, making the bearing raceway thickness dimension d It is 10mm.

[0081] Experimental Comparison and Results: A comparative analysis was conducted on the bearings strengthened in Comparative Example 1 and Example 3.

[0082] 1. The depth distribution of residual compressive stress was experimentally tested, and the results are as follows: Figure 3 As shown. According to Figure 3 It can be seen that in traditional processes, the depth distribution of residual compressive stress fluctuates greatly in the shallow layer, while the combined strengthening process of this invention exhibits a more stable and uniform depth distribution of residual compressive stress in both the shallow and deep layers.

[0083] 2. The surface microstructure was examined, and the results are as follows: Figure 4 As shown. According to Figure 4 It can be seen that the uniformity of the reinforcing layer in the traditional process is not as good as the combined reinforcing process of the present invention.

[0084] 3. Contact fatigue performance was tested, and the results are as follows: Figure 5 As shown. According to Figure 5 It can be seen that the average contact fatigue life of the combined strengthening process is nearly twice that of the traditional strengthening process.

[0085] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A laser shock combined strengthening process for improving bearing contact fatigue performance, characterized in that Preparation is as follows: S1, pre-machining: a machining allowance layer is reserved on the raceway surface of the bearing, the thickness of the raceway is d , and the thickness of the machining allowance layer is d 0; S2, coating protection: coating an absorbing protective layer on the raceway surface of the bearing, and applying a constraint layer on the surface of the absorbing protective layer; S3, large spot laser shock: using large spot laser shock to strengthen the raceway area, forming a first plastic strengthening layer with a depth of d1, d1>d0; the energy of the large spot laser shock is 2-25 J, the spot diameter is 1-3 mm, the pulse width is 20-50 ns, and the repetition frequency is 1-20 Hz; S4, micro-scale laser shock: directly applying a constraint layer on the surface of the first plastic strengthening layer without an absorbing protective layer, and using micro-scale laser shock to strengthen the raceway area, forming a second plastic strengthening layer with a depth of d2, d1>d2>d0; S5, removing the reserved machining allowance layer.

2. The process for laser shock combined strengthening for improving bearing contact fatigue performance according to claim 1, characterized in that: The depth of the first plastically strengthened layer d 1 is the thickness of the raceway is d 0.1 to 0.3 times.

3. The process for laser shock combined strengthening for improving bearing contact fatigue performance according to claim 1, characterized in that: The energy of the large spot laser shock is greater than that of the micro-scale laser shock; the spot diameter of the large spot laser shock is greater than that of the micro-scale laser shock; the pulse width of the large spot laser shock is greater than that of the micro-scale laser shock; and the repetition frequency of the large spot laser shock is less than that of the micro-scale laser shock.

4. The process for laser shock combined strengthening for improving bearing contact fatigue performance according to claim 1, characterized in that: The depth of the first plastic strengthening layer is 1-2 mm.

5. The process for laser shock combined strengthening for improving bearing contact fatigue performance according to claim 1, characterized in that: The energy of the micro-scale laser shock is 10-500 mJ, the spot diameter is 100-500 μm, the pulse width is 5-10 ns, and the repetition frequency is 100-1000 Hz.

6. The process for laser shock combined strengthening for improving bearing contact fatigue performance according to claim 5, characterized in that: The depth of the second plastic strengthening layer is 0.4-0.6 mm.

7. The process for laser shock combined strengthening for improving the bearing contact fatigue performance according to any one of claims 1-6, characterized in that: The absorbing protective layer uses black tape; and the constraint layer is a water curtain formed by applying deionized water.

8. The process for laser shock combined strengthening for improving bearing contact fatigue performance according to claim 1 or 2 or 3, characterized in that: The reserved machining allowance layer is removed in step S5 by using a precision grinding and polishing process to process and remove the machining allowance layer on the raceway surface.

9. A bearing machining process characterized by: The laser shock combined strengthening process for improving the contact fatigue performance of a bearing according to any one of claims 1-8.

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