Laser shock peening method based on surface microstructure

Abstract

The invention provides a laser shock peening method based on a surface microstructure, and aims to generate refraction, reflection, interference and local energy focusing effects on generated high-strain-rate stress waves in the laser shock process through the metal surface microstructure. Therefore, directional regulation and control of the residual compressive stress field, regionalized enhancement of the strengthening effect and deep controllable gain are achieved, and the fatigue performance and the surface service function of the material are remarkably improved. Specifically, according to the method, regularly-arranged microstructure textures are formed on the surface of a material to be reinforced through machining; and then laser shock treatment is carried out on the surface of the texture-constructed material, so that laser-induced shock waves are refracted, reflected, split or locally focused at the boundary or interface of the texture, and a deep, high-amplitude and directional residual compressive stress layer is formed. Compared with a traditional flat surface laser shock peening technology, the laser shock peening method has the advantages that the depth of a strengthened layer and the amplitude and uniformity of residual compressive stress can be remarkably improved, and programmable stress field, adjustable parameters and predictable enhancement effect can be realized. The method is suitable for surface strengthening treatment of aerospace turbine blades, structural fasteners, additive manufacturing metal components and high-performance mechanical key parts, and has generalizability and engineering application value.

Description

Technical Field

[0001] This invention relates to the field of metal material strengthening technology, specifically to a laser shock strengthening method based on surface microstructures. The method involves preparing microstructures on the workpiece surface that refract, reflect, or locally focus stress waves generated by the shock, thereby achieving directional amplification and depth controllability of the residual compressive stress field. Background Technology

[0002] Laser shock peening (LSP) is a non-contact, high-strain-rate surface treatment technology that uses laser-induced plasma to generate high-energy shock waves, forming deep and stable residual compressive stresses on the material surface. This significantly improves fatigue life, crack propagation resistance, and surface mechanical properties, and has been widely applied in the manufacturing of aero-engine blades, key automotive components, and high-reliability structures. However, existing LSP processes still have significant limitations: the propagation direction of the shock stress wave is uncontrollable, leading to highly random residual stress distribution; the depth of the strengthened layer is limited and its uniformity is insufficient, easily resulting in abrupt hardness changes and localized stress concentrations; and the evolution of the material microstructure lacks predictability, with strengthening quality relying on empirical adjustments and parameter trials. Furthermore, existing methods that improve microstructure and strengthening effects by simply optimizing laser parameters have limited room for improvement and significantly impact process stability and consistency. Therefore, there is an urgent need for a novel LSP technology system that can achieve controllable stress wave behavior, directional control of the residual stress field, and high repeatability and consistency to overcome existing process performance bottlenecks and meet the needs of complex engineering applications.

[0003] Therefore, this invention provides a laser shock strengthening method based on surface microstructure texture-induced laser shock strengthening. It uses a femtosecond laser to process structures on the surface of metallic materials that can guide the directional scattering, refraction, and local splitting effects of shock waves, thereby achieving directional amplification and depth controllability of the residual compressive stress field. By processing microstructures on the surface of metallic materials with femtosecond lasers that can reflect or absorb stress waves generated by laser shock strengthening, the propagation of stress waves during laser shock strengthening becomes more uniform and controllable, improving the controllability and application capabilities of laser shock strengthening. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a laser shock strengthening method based on surface microstructures. By using femtosecond laser processing, microstructures that can reflect or absorb stress waves generated by laser shock strengthening are fabricated on the surface of metallic materials. This makes the propagation of stress waves more uniform and controllable during laser shock strengthening, thereby improving the controllability and application capabilities of laser shock strengthening.

[0005] A laser shock peening method based on surface microstructure, comprising the following steps:

[0006] Step 1: Pre-treat the workpiece to ensure that the surface roughness Ra ≤ 1.6 μm, so as to ensure the consistency of texture formation and the stability of laser energy absorption.

[0007] Step 2: Use a femtosecond laser to construct microstructures on the workpiece surface.

[0008] Step 3: A sacrificial layer and a constraint layer are coated on the surface of the microstructure, and laser shock peening is performed.

[0009] Preferably, the metal surface microstructure manufacturing method described in step two includes femtosecond laser etching, photolithography + reactive ion etching, nanoimprinting, micromachining, microelectrode machining, etc.

[0010] Preferably, the metal surface microstructure described in step two includes linear groove structure arrays, periodic lattice structures, concentric ring texture structures, parabolic focusing texture structures, gradient geometric texture structures, and any other structures that can guide shock waves to undergo directional scattering, refraction, and local splitting effects.

[0011] Preferably, the processing in step three uses pulsed laser, with laser processing parameters of laser wavelength 193-2940nm and power 10-10 9 W / cm 2 The pulse width is 15fs-1000ns, the processing frequency is 1Hz-10MHz, the overlap rate is 30%-70%, the number of impacts is 1-10, the constraint layer includes a water layer, K9 glass, an air constraint layer, and a composite layer of water film and K9 glass, and the absorption layer includes aluminum foil, black tape, and toner.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1. Microstructures can enhance residual stress peak value through laser shock peening;

[0014] 2. Microstructures can enable laser shock peening to form deeper reinforcement layers;

[0015] 3. Process combinations can significantly extend the service life of materials and improve their overall mechanical properties. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 Laser shock peening method based on surface microstructure.

[0018] Figure labeling: 1: Microstructure; 12: Sample after femtosecond laser processing; 13: Sacrificial layer; 14: Constraint layer; 15: Laser. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more definite definition of the scope of protection of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Step 1: Pre-treat the workpiece to ensure that the surface roughness Ra ≤ 1.6 μm, so as to ensure the consistency of texture formation and the stability of laser energy absorption.

[0021] Step 2: Use a femtosecond laser to construct microstructures on the workpiece surface.

[0022] Step 3: A sacrificial layer and a constraint layer are coated on the surface of the microstructure, and laser shock peening is performed.

[0023] Preferably, the metal surface microstructure manufacturing method described in step two includes femtosecond laser etching, photolithography + reactive ion etching, nanoimprinting, micromachining, microelectrode machining, etc.

[0024] Preferably, the metal surface microstructure described in step two includes linear groove structure arrays, periodic lattice structures, concentric ring texture structures, parabolic focusing texture structures, gradient geometric texture structures, and any other structures that can guide shock waves to undergo directional scattering, refraction, and local splitting effects.

[0025] Preferably, the processing in step three uses pulsed laser, with laser processing parameters of laser wavelength 193-2940nm and power 10-10 9 W / cm 2 The pulse width is 15fs-1000ns, the processing frequency is 1Hz-10MHz, the overlap rate is 30%-70%, the number of impacts is 1-10, the constraint layer includes a water layer, K9 glass, an air constraint layer, and a composite layer of water film and K9 glass, and the absorption layer includes aluminum foil, black tape, and toner.

[0026] Implementation Case 1:

[0027] Step 1: Polish the surface of an A286 alloy sample with standard tensile dimensions until smooth.

[0028] Step 2: A linear groove array microstructure is constructed on the workpiece surface using femtosecond laser etching.

[0029] Step 3: A sacrificial layer and a constraint layer are coated on the microtextured surface, and laser shock peening is performed.

[0030] Implementation Case 2:

[0031] Step 1: Polish the surface of an A286 alloy sample with standard tensile dimensions until smooth.

[0032] Step 2: A sacrificial layer and a constraint layer are coated on the microtextured surface, and laser shock peening is performed.

[0033] The tensile properties of Examples 1, 2, and 3 are shown in Table 1. As can be seen from the table, this method effectively improves the mechanical properties of A286 alloy.

[0034]

[0035] In summary, this technical solution discloses a laser shock stabilization method based on surface microstructure. First, femtosecond laser processing is used to fabricate a structure on the surface of a metal material that can guide the directional scattering, refraction, and local splitting effects of shock waves. Then, laser shock stabilization is performed on the material surface, introducing deep residual compressive stress and nanocrystalline layer structures into the surface layer using a high-energy pulsed laser. The femtosecond laser processing creates microstructures on the metal surface that can reflect or absorb the stress waves generated by laser shock stabilization, making the propagation of stress waves more uniform and controllable during the laser shock stabilization process, thus improving the controllability and application capability of laser shock stabilization. This laser shock stabilization method based on surface microstructure texture-induced structure has a reasonable process design, strong operability, and wide applicability. It can effectively solve the problems of uneven microstructure distribution, instability, and insufficient strengthening effect in metal materials prepared by traditional processes, enabling high-load, long-term safe operation of metal materials.

[0036] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0037] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A laser shock peening method based on surface microstructure, the method comprising the following steps: Step 1: Pre-treat the workpiece to ensure that the surface roughness Ra ≤ 1.6 μm, so as to ensure the consistency of texture formation and the stability of laser energy absorption. Step 2: Use femtosecond laser etching to construct microstructure textures on the workpiece surface. Step 3: A sacrificial layer and a constraint layer are coated on the microtextured surface, and laser shock peening is performed.

2. The laser shock peening method based on surface microstructure according to claim 1, characterized in that: It prepares microstructures on the surface of workpieces that can refract, reflect or locally focus stress waves, thereby achieving directional amplification and depth control of the residual compressive stress field.

3. The laser shock peening method based on surface microstructure according to claim 1, characterized in that: The types of metal samples mentioned in step one include stainless steel, nickel-based alloys, aluminum alloys, titanium alloys, and alloy steels. The preparation work includes polishing the metal surface to a smooth finish, machining it to the appropriate size, and surface inspection.

4. The laser shock peening method based on surface microstructure according to claim 1, characterized in that: The metal surface microstructure manufacturing methods described in step two include femtosecond laser etching, photolithography + reactive ion etching, nanoimprinting, micromachining, and microelectrode machining.

5. The laser shock peening method based on surface microstructure according to claim 1, characterized in that: The metal surface microstructures described in step two include linear groove arrays, periodic lattice structures, concentric ring texture structures, parabolic focusing texture structures, gradient geometric texture structures, and any other structures that can guide shock waves to undergo directional scattering, refraction, and local splitting effects.

6. The laser shock peening method based on surface microstructure according to claim 1, characterized in that: The laser shock processing parameters described in step three are: laser wavelength 193-2940nm, power 10-10 9 W / cm 2 The pulse width is 15fs-1000ns, the processing frequency is 1Hz-10MHz, the overlap rate is 30%-80%, the number of impacts is 1-10, the constraint layer includes a water layer, K9 glass, an air constraint layer, and a composite layer of water film and K9 glass, and the absorption layer includes aluminum foil, black tape, and toner.

Images