Laser strengthening method for regulating and controlling surface performance of additive component of combustion chamber

Abstract

The invention is applicable to the field of laser strengthening, and provides a laser strengthening method for regulating and controlling the surface performance of an additive part of a combustion chamber, which comprises the following steps: S1, pretreatment: sequentially performing stress relief annealing, surface cleaning, cleaning and drying on a metal part of the additive combustion chamber; s2, coating-free laser shock peening is conducted, specifically, the pretreated part is fixed to a five-axis workbench through a special clamp to be positioned, and Nd: YAG or Nd: YLF pulse laser is adopted for shock according to a path planned by a three-dimensional CAD model; s3, post-treatment and performance verification are conducted, specifically, after the part is cleaned, the surface appearance, roughness, residual stress and microhardness are detected, and a microstructure is observed; according to the method, the coating procedure of traditional laser shock is omitted, the pollution risk is eliminated, the surface roughness is synchronously reduced, the deep residual compressive stress is introduced, the microhardness is improved, the fatigue resistance of the combustion chamber component is remarkably improved, and the method is suitable for materials such as nickel-based high-temperature alloy and cobalt-based high-temperature alloy and components of complex structures.

Description

Technical Field

[0001] This invention belongs to the field of laser strengthening, and particularly relates to a laser strengthening method for controlling the surface properties of additive components for combustion chambers. Background Technology

[0002] As a core hot-end component of aero-engines and gas turbines, the combustion chamber is subjected to high temperature (600-1200℃), high pressure (1-3MPa) and alternating load environments for a long time, requiring extremely high surface finish and mechanical properties (hardness, residual stress). However, combustion chamber metal components formed by additive manufacturing technology (such as selective laser melting and direct energy deposition) have inherent defects: high surface roughness (Ra10-15μm), large internal residual tensile stress (+150 to +300MPa), and uneven microstructure, resulting in poor fatigue resistance, easy early crack failure, and severely limiting service life. Traditional surface strengthening techniques (such as mechanical shot peening) can introduce residual compressive stress through plastic deformation, but they have poor coverage of complex structures such as the "closed inner cavity and fine flow channels" of the combustion chamber, and cannot achieve internal wall strengthening. Moreover, the shot peening process is prone to surface scratches and shot residue, which further deteriorates the surface quality and cannot meet the processing requirements of precision parts. While traditional laser shock peening technology can introduce deep (≥200μm) residual compressive stress, it requires coating the component surface with an absorption layer (such as black paint or aluminum foil) and a constraint layer (such as water or glass). The absorption layer material is prone to remaining in the complex flow channels of the combustion chamber, and it is easy to fall off and carbonize at high temperatures, leading to flow channel blockage. The constraint layer (such as water) is prone to seeping into the inner cavity and causing corrosion. Moreover, the coating and cleaning process is cumbersome (requiring 3-5 steps), resulting in low processing efficiency and increasing the risk of pollution, which threatens the safe operation of the engine. Therefore, a laser strengthening method is needed to control the surface properties of additive components for combustion chambers to solve the above problems. Summary of the Invention

[0003] The purpose of this invention is to provide a laser strengthening method for controlling the surface properties of additive components in combustion chambers, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A laser strengthening method for surface property control of additive manufacturing components for combustion chambers includes the following steps: S1. Preprocessing, S1 includes the following steps: S11. Place the additively manufactured combustion chamber metal parts in a vacuum or protective atmosphere heat treatment furnace and perform solution treatment, aging treatment or hot isostatic pressing treatment according to the material of the parts. Eliminate residual tensile stress generated during additive manufacturing, stabilize the microstructure, and avoid cracks caused by stress concentration during laser shock. S12. Surface cleaning is performed using dry sandblasting or electrochemical polishing; Surface cleaning is achieved by physically removing unfused powder and oxide scale from the surface through "dry sandblasting" or by chemically dissolving surface protrusions through "electrochemical polishing," reducing the roughness from Ra10-15μm to Ra1-8μm, while removing oil and impurities and improving laser energy absorption rate. S13. After ultrasonic cleaning with deionized water, dehydrate with anhydrous ethanol and dry in an oven. The cleaning and drying process involves "ultrasonic cleaning + anhydrous ethanol dehydration" to thoroughly remove residual abrasive / electrolyte and avoid the "impurity vaporization-surface ablation" phenomenon during subsequent laser impact. After pretreatment, the laser energy absorption rate of the component surface increases from 40% to over 80%, providing a key guarantee for the uniformity of S2 laser strengthening. S2, Uncoated Laser Shock Enhancement, S2 includes the following steps: S21. Fix the part processed in S1 onto the five-axis CNC worktable using a special fixture, and position it using a laser displacement sensor or machine vision system. The five-axis linkage worktable, combined with a laser displacement sensor / machine vision system, enables precise positioning of complex curved surfaces with a positioning accuracy of ≤0.05mm, ensuring that the laser beam acts perpendicularly on the surface to be impacted, thus avoiding energy loss. S22. Select an Nd:YAG or Nd:YLF pulsed laser for laser shock; Using Nd:YAG / Nd:YLF pulsed lasers, and with parameters designed for "low power density (0.5-3.0GW / cm²) and short pulse width (10-30ns)," an extremely thin layer (1-5μm) on the metal surface is rapidly vaporized to generate a 1-5GPa high-pressure plasma shock wave. The shock wave induces plastic deformation of the surface layer (200-500μm), introducing high-density dislocations and residual compressive stress. At the same time, the "micro-forging" effect smooths out surface protrusions, further reducing roughness. Moreover, the design without absorption or constraint layers completely eliminates the risk of contamination. This process reduces 2-3 steps compared to traditional laser shock, increases processing efficiency by 40%, and eliminates coating residue problems, completely solving the risk of flow channel blockage. S23. Plan the scanning path based on the 3D CAD model of the combustion chamber components; The scanning path planning adopts differentiated solutions for different structures: "serpentine reciprocating scanning" is used for planar areas to ensure uniform overlap (no missed areas); "equidistant offset scanning" is used for curved areas to conform to the curvature changes of the curved surface; "spiral scanning" is used for closed cavities / fine flow channels, expanding from the center to the outer circle to achieve reinforcement without dead angles; this path design can achieve 100% reinforcement coverage for complex structures, solving the problem of "cavities cannot be reinforced" in traditional technology; S3, Post-processing and Performance Verification: S3 includes the following steps: S31. Surface cleaning: Wipe the surface of the component with a lint-free cloth dampened with analytical grade anhydrous ethanol or acetone. No damaging cleaning is required to ensure the integrity of the surface. S32. Surface morphology and roughness inspection: Ra and Rz values ​​are detected using a white light interferometric surface profilometer. S33. Residual stress detection: X-ray diffraction stress analyzer combined with electrolytic peeling technology is used to detect surface and subsurface residual stress and plot compressive stress layer depth distribution curve. S34. Microhardness testing: Using a micro Vickers hardness tester, the hardness values ​​in the surface and depth directions are measured under a load of 0.3 kgf. S35. Microstructure observation: Prepare metallographic samples of the component cross-section and observe the surface microstructure using an optical microscope or scanning electron microscope. S32-S35 respectively test roughness (verify surface finish), residual stress (verify compressive stress magnitude and layer depth), microhardness (verify mechanical properties), and microstructure (verify no damage), forming a "performance closed loop"; this testing process can control the performance failure rate to below 3%, ensuring that each product meets the requirements of extreme combustion chamber operating conditions.

[0005] Pretreatment provides a surface foundation of "low stress, high cleanliness, and low roughness" for laser shock, uncoated laser shock achieves core strengthening, and posttreatment verifies the effect. The three form a complete process chain of "pretreatment-strengthening-verification". This process design ensures that each step provides a guarantee for subsequent steps, avoiding uneven laser impact effects due to incomplete pretreatment or the omission of unqualified parts due to the lack of verification steps, thereby improving process stability to over 95% and achieving a product qualification rate of 98%.

[0006] In a further technical solution, in step S11, the hot isostatic pressing parameters are 1100±50℃, 100±10MPa, and heat preservation for 2±0.5 hours.

[0007] In a further technical solution, in step S12, dry sandblasting uses 50-150μm spherical ceramic / glass beads, air pressure 0.2-0.5MPa, spray gun distance 100-200mm, and spray angle 45-90°; electrochemical polishing uses 40-70℃ acidic / neutral electrolyte, voltage 10-20V, and processing time 3-10 minutes.

[0008] In a further technical solution, in step S13, the ultrasonic cleaning time with deionized water is 10-20 minutes, the oven temperature is 60-80℃, and the drying time is 30-60 minutes.

[0009] In a further technical solution, in step S21, the angle between the laser beam and the normal of the surface to be impacted is ≤5°; in step S22, the laser wavelength is 1064nm or 532nm (inclusive of 527nm±2nm), the pulse energy is 2-15J, the pulse width is 10-30ns, the spot diameter is 2-6mm, and the power density is 0.5-3.0GW / cm². 2 The repetition frequency is 1-10Hz, and the overlap rate is 40-70%. In step S23, the planar area adopts serpentine reciprocating scanning, the curved area adopts equidistant offset scanning, and the closed inner cavity / fine flow channel adopts spiral scanning.

[0010] In a further technical solution, in step S22, the thickness of the heat-affected zone on the surface of the component after laser shock is ≤10μm, and there are no visible molten recast layer, microcracks or ablation pits on the surface.

[0011] A further technical solution is to add a plasma cleaning process after dry sandblasting in step S12: using argon or argon-hydrogen mixed plasma (argon-hydrogen volume ratio 9:1-7:3) to bombard the surface of the component, with a processing time of 5-15 minutes and a power of 500-1000W.

[0012] In a further technical solution, in step S22, the laser shock process is carried out in an inert gas local protective environment: the inert gas is argon (purity ≥99.99%) or nitrogen (purity ≥99.99%), the gas flow rate is 5-15L / min, and the gas flow direction is coaxial with the laser beam or blown laterally toward the spot point (distance from the center of the spot ≤10mm); the material of the combustion chamber metal component is selected from nickel-based high-temperature alloy, cobalt-based high-temperature alloy or titanium-aluminum alloy; the additive manufacturing technology is powder bed melting technology or direct energy deposition technology; the method is applicable to complex structure combustion chamber components such as engine support plates with internal cooling channels and flame tubes with fine flow channels; the surface roughness of the key stress area / thermal fatigue sensitive area of ​​the component is Ra1-6μm, the surface residual compressive stress is -300 to -600MPa, the compressive stress layer depth is ≥200μm, the surface microhardness is increased by 15%-35% compared with the original additive state, and there is no absorption layer residue or laser ablation damage.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This invention simplifies the process and eliminates pollution: by connecting the "cleaning and drying" pretreatment in S1 with the "coating-free laser shock" in S2, the absorption layer coating, constraint layer covering and subsequent cleaning processes of traditional laser shock are eliminated, simplifying the process flow (reducing 2-3 processes); at the same time, it eliminates the risk of pollution from the absorption layer residue in the flow channel, and is especially suitable for combustion chamber components with fine flow channels, ensuring the safe operation of the engine; This invention achieves synergistic performance enhancement: by eliminating initial tensile stress through S1 "stress-relief annealing," it lays the foundation for introducing deep compressive stress through S2 laser shock; the synergistic design of S2 laser parameters and scanning path introduces 200-500μm deep residual compressive stress and increases microhardness by 15%-35%, while further reducing surface roughness (Ra is reduced by 10%-44% compared to the pretreatment) through the "micro-forging" effect, achieving synergistic optimization of surface finish and mechanical properties, and significantly improving the fatigue resistance of the component; This invention is highly adaptable: through the combination of S2 "five-axis positioning" and "differentiated scanning path", it can achieve comprehensive reinforcement of complex structures such as engine support plates with internal cooling channels and fuel nozzles with closed internal cavities; at the same time, it is compatible with a variety of materials such as nickel-based high-temperature alloys, cobalt-based high-temperature alloys, and titanium-aluminum alloys, covering the mainstream additive combustion chamber component types and having a wide range of applications.

[0014] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0015] Figure 1 This is a flowchart of the process flow of the present invention; Figure 2 This is a comparison of the surface microhardness of the "unstrengthened" and "laser-strengthened" samples of the present invention. Figure 3 This is a comparison diagram of the surface residual stress of the "unstrengthened" and "laser-strengthened" samples of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0018] Example 1 like Figure 1 , Figure 2 and Figure 3 As shown, this embodiment of the invention provides a laser strengthening method for controlling the surface properties of additive manufacturing components in combustion chambers, comprising the following steps: S1. Preprocessing, S1 includes the following steps: S11. Place the Ti6Al4V titanium alloy engine support plate (with internal cooling channels, channel diameter 8mm) formed by selective laser melting into a high vacuum heat treatment furnace (vacuum degree ≤1×10⁻). 5According to the material properties of Ti6Al4V, stress-relief annealing was performed at a temperature of 800℃ and a holding time of 2 hours. The material was then cooled in the furnace to below 300℃ before being removed from the furnace. S12. Electrochemical polishing is used for surface cleaning. An environmentally friendly electrolyte (phosphoric acid-sulfuric acid system) that does not contain perchloric acid is selected. The temperature is set at 35℃, the voltage at 15V, and the processing time at 6 minutes. S13. Ultrasonic cleaning with deionized water for 15 minutes (power 300W), followed by dehydration with anhydrous ethanol, and then drying in a 70℃ oven for 45 minutes. S2, Uncoated Laser Shock Enhancement, S2 includes the following steps: S21. The support plate after S1 treatment is fixed to the five-axis linkage CNC worktable using a special titanium alloy fixture. A laser displacement sensor (accuracy ±0.02mm) is used to position the blade root transition R area (curvature radius 5mm) to ensure that the angle between the laser beam and the normal of the surface to be impacted is ≤5°. S22. A Nd:YLF pulsed laser was selected for laser shock, with the following settings: laser wavelength 532nm, pulse energy 6J, pulse width 18ns, spot diameter 3mm, and power density ≈1.6GW / cm². 2 The repetition frequency is 6Hz and the overlap rate is 50%. The process is carried out in a local protective environment of inert gas (argon, purity ≥99.99%), with a gas flow rate of 8L / min and the gas flow direction is coaxial with the laser beam. S23. Plan the scanning path according to the 3D CAD model of the support plate: use contour line offset scanning for the blade root R area (offset distance 1.5mm), and use serpentine reciprocating scanning for the blade body surface (scanning speed 100mm / s). S3, Post-processing and Performance Verification: S3 includes the following steps: S31. Surface cleaning: Wipe the surface of the support plate with a lint-free cloth dampened with analytical grade acetone. S32. Surface morphology and roughness detection: The Ra and Rz values ​​of the leaf root R region were detected using a white light interferometric surface profilometer (resolution 0.1 nm). S33. Residual stress detection: X-ray diffraction stress analyzer (Cu target, Kα rays) combined with electrolytic stripping technology was used to detect residual stress on the surface and at a depth of 280μm, and the compressive stress layer depth distribution curve was plotted. S34. Microhardness testing: A micro Vickers hardness tester is used to test the hardness values ​​of the surface and depth directions (50μm, 100μm, 200μm, 280μm) under a load of 0.3kgf (holding pressure for 15s). One test point is set every 50μm. S35. Microstructure observation: Prepare metallographic samples of the cross-section of the support plate (polished with 400#-2000# sandpaper and 1μm diamond polishing), and observe the surface microstructure using an optical microscope (magnification 500×).

[0019] In this embodiment, the strengthening effect of the Ti6Al4V titanium alloy engine support plate is as follows: Surface quality: The roughness Ra was reduced from 10 μm after additive manufacturing to 1.5 μm through electrochemical polishing, and further reduced to 1.1 μm after laser strengthening. The Rz value was reduced by 35% simultaneously, meeting the "low flow resistance" requirement of the cooling channel. There were no visible molten recast layer or microcracks on the surface, and the thickness of the heat-affected zone was 8 μm, which met the surface integrity requirements of precision components. Mechanical properties: The residual stress changes from +200MPa (tensile stress) before strengthening to -420MPa (compressive stress), and the compressive stress layer depth is 280μm, which can effectively inhibit the initiation of fatigue cracks; the microhardness increases from 350HV0.3 in the matrix to 445HV0.3 on the surface, an increase of 27%, and the wear resistance is significantly enhanced; Safety and Efficiency: No coating residue; cooling channels are 100% clean as inspected endoscopically, completely eliminating the risk of flow channel blockage; processing steps are reduced from the traditional 8 to 5, and single-piece processing time is shortened from 8 hours to 5 hours, increasing processing efficiency by 37.5%. Fatigue performance: High-cycle fatigue test (10 7 After one cycle (stress ratio R=0.1, load 500MPa), the fatigue life of the support plate is increased by 2.5 times compared with the unstrengthened part, which fully meets the requirements of aero-engine use.

[0020] Example 2 The difference between this embodiment and Embodiment 1 is that: Component to be processed: Inconel 718 nickel-based superalloy flame tube (with fine flow channels, flow channel diameter 3mm, thin wall thickness 2mm) formed by direct energy deposition, the material being selected from the nickel-based superalloy as defined in claim 8; Step S1 Pretreatment: S11. Based on the material characteristics of Inconel 718, stress-relief annealing is performed in an atmospheric protection furnace (argon atmosphere, flow rate 10L / min), with a temperature of 980℃ and a holding time of 1 hour, followed by air cooling to room temperature; S12. Surface cleaning is performed using dry sandblasting, using 50-80μm spherical ceramic beads, a gas pressure of 0.3MPa, a spray gun distance of 150mm, and a spray angle of 75°; after dry sandblasting, a plasma cleaning process is added, using argon plasma to bombard the surface of the flame tube for 10 minutes at a power of 800W; S13. Ultrasonic cleaning with deionized water for 20 minutes, followed by dehydration with anhydrous ethanol, and then drying in a 60℃ oven for 60 minutes; Step S2 Uncoated Laser Shock Enhancement: S22, Select an Nd:YAG pulsed laser, set the laser wavelength to 1064nm, pulse energy to 8J, pulse width to 20ns, spot diameter to 4mm, and power density to approximately 1.6GW / cm². 2The repetition frequency is 8Hz and the overlap rate is 55%. The inert gas used is nitrogen (purity ≥99.99%), the airflow rate is 10L / min, and the airflow direction is lateral blowing towards the spot point of action. S23. According to the three-dimensional CAD model of the flame tube, the inner wall of the fine flow channel is spirally scanned, expanding from the center of the flow channel to the outer ring, with a pitch of 2mm and a scanning speed of 80mm / s. Step S3 Performance Verification: S33 Residual stress detection depth is 350μm, S34 Hardness detection depth is 350μm.

[0021] In this embodiment, the strengthening effect of the Inconel 718 nickel-based high-temperature alloy flame tube is as follows: Surface quality: The roughness Ra was reduced from 12μm after additive manufacturing to 5μm by dry sandblasting, and there was no residual abrasive after plasma cleaning. After laser strengthening, it was further reduced to 3.8μm, effectively reducing carbon deposits at high temperatures; the surface heat-affected zone thickness was 9μm, with no ablation pits or microcracks, and the thin-walled structure was free from deformation. Mechanical properties: The residual stress changed from +180MPa (tensile stress) before strengthening to -500MPa (compressive stress), and the compressive stress layer depth was 350μm, which significantly improved the resistance to high temperature creep; the microhardness increased from 380HV0.3 in the matrix to 500HV0.3 on the surface, an increase of 31%, and the wear resistance met the "high frequency friction" requirements of the flame tube. High-temperature performance: Nitrogen protection effectively inhibits oxidation of nickel-based alloy surfaces, with an oxide layer thickness of ≤0.3μm. No oxidation peeling occurs after 500 hours of continuous operation at 800℃. Thermomechanical fatigue tests (500 cycles, 600℃ to room temperature, stress amplitude 100MPa) show that the life of the flame tube is 3 times longer than that of the unstrengthened part. Structural adaptability: The spiral scanning achieves 100% reinforcement of the inner wall of the flow channel (3mm in diameter), solving the problem of "the flow channel cannot be reinforced" in traditional technology. The flow channel is unobstructed after a gas pressure test (0.5MPa), and the pressure loss is ≤5%, which meets the standards for use in gas turbine combustion chambers.

[0022] Example 3 The difference between this embodiment and Embodiment 2 is that: Component to be processed: Haynes 188 cobalt-based superalloy fuel nozzle (with a closed inner cavity, inner cavity diameter 10 mm, fuel atomization hole diameter 1 mm) formed by selective laser melting, the material of which is selected from the cobalt-based superalloy as defined in claim 8; Step S1 Pretreatment: S11. Based on the material characteristics of Haynes188, hot isostatic pressing is used, with a temperature of 1100℃, a pressure of 100MPa, and a holding time of 2 hours; S12. Dry sandblasting uses 80-100μm spherical glass beads, an air pressure of 0.4MPa, a spray gun distance of 120mm, and a spray angle of 60°; Plasma cleaning uses argon-hydrogen mixed plasma to bombard the nozzle surface for 15 minutes at a power of 1000W. Step S2 Uncoated Laser Shock Enhancement: S22, Select an Nd:YAG pulsed laser, set the laser wavelength to 532nm, pulse energy to 5J, pulse width to 15ns, spot diameter to 3mm, and power density to approximately 1.8GW / cm². 2 1. Repetition frequency 5Hz, overlap rate 60%; S23. Based on the nozzle 3D CAD model, the inner wall of the closed cavity is scanned with equidistant offset, offset distance 1.2mm, scanning speed 60mm / s; the area around the fuel atomizing hole is scanned in a ring (radius 2mm, number of scans 3). Step S3 Performance Verification: Add fuel atomization efficiency testing (using a laser particle size analyzer to test droplet diameter distribution).

[0023] In this embodiment, the strengthening effect of the Haynes 188 cobalt-based superalloy fuel nozzle is as follows: Surface quality: The roughness Ra was reduced from 11 μm after additive manufacturing to 4.5 μm by dry sandblasting, and further reduced to 2.5 μm after laser strengthening, optimizing fuel flow characteristics; the inner wall of the sealed cavity was 100% reinforced with no leaks or areas, and the inner wall was free from ablation damage. Mechanical properties: The residual stress changed from +190MPa (tensile stress) before strengthening to -450MPa (compressive stress), the compressive stress layer depth was 320μm, and no thermal cracks were generated after 800℃ high temperature cycle test (1000 times); the microhardness increased from 400HV0.3 in the matrix to 500HV0.3 on the surface, an increase of 25%, and the impact resistance met the nozzle's "high frequency fuel impact" requirement; Functional performance: Fuel atomization efficiency testing showed that the average droplet diameter decreased from 80μm to 65μm, atomization uniformity (RSD) decreased from 15% to 8%, and combustion chamber efficiency improved by 5%; Material compatibility: Hot isostatic pressing effectively eliminates the internal porosity of Haynes188 cobalt-based alloy (density increases from 99.2% to 99.9%), and the microstructure does not crack after laser shock, meeting the "high temperature strength and toughness" requirements of cobalt-based alloys.

[0024] Working principle and usage process of this invention: Pre-treatment stage: Laying the foundation for stability and strengthening. First, addressing the residual tensile stress and microstructure inhomogeneity within the additive combustion chamber components, S11 "stress-relief annealing under vacuum / protective atmosphere" utilizes thermal cycling to rearrange dislocations within the components, eliminating residual tensile stress (reducing it from +150 to +300 MPa to ≤ +50 MPa) while refining the grains (grain size from 5-10 μm to 2-5 μm), preventing cracks caused by stress concentration during laser shock. Second, addressing defects such as unfused powder and oxide scale on the component surface, S12 " Dry blasting (physical removal) or electrochemical polishing (chemical dissolution) removes surface defects and reduces initial roughness (from Ra10-15μm to Ra1-8μm), while removing oil and impurities and increasing laser energy absorption rate (from 40% to 70%). Finally, S13 "deionized water ultrasonic cleaning + anhydrous ethanol dehydration + oven drying" thoroughly removes residual abrasives or electrolytes from the surface, preventing impurities from vaporizing and causing surface ablation during laser impact, and providing a "low-stress, high-cleanliness, low-roughness" surface condition for subsequent laser strengthening. Uncoated Laser Shock Enhancement Stage: To achieve core performance control, the component that has passed the S1 treatment is fixed to a five-axis CNC worktable using a dedicated fixture. The complex areas of the component are precisely positioned using the S21 "laser displacement sensor / machine vision system," ensuring that the angle between the laser beam and the normal to the surface to be impacted is ≤5°, avoiding energy loss due to angular deviation. Subsequently, using the S22 "Nd:YAG / Nd:YLF pulsed laser," based on the component's material properties and structural requirements, a low power density (0.5-3.0 GW / cm²) is set. 2 The parameters of "short pulse width (10-30ns)" allow the laser energy to be rapidly absorbed and vaporized by an extremely thin layer (1-5μm) on the surface of the component, forming a high temperature (10... 4 -10 5 High-pressure (1-5 GPa) plasma at ℃; the shock wave generated by the expansion of the plasma propagates into the interior of the component, causing plastic deformation of the metal within a depth range of 200-500 μm on the surface, forming high-density dislocations (dislocation density from 10 to 10^24 GHz). 12 m -2 Upgraded to 10 14 m -2 This process introduces residual compressive stress ranging from -300 to -600 MPa; simultaneously, the "micro-forging" effect of the shock wave flattens surface protrusions, further reducing roughness; for different component structures, the S23 "differentiated scanning path (planar serpentine, curved equidistant offset, internal cavity spiral)" ensures that the strengthened area has no missed punching or repeated over-punching, achieving uniform strengthening; the entire process does not require the coating of an absorption layer and a constraint layer, completely eliminating the risk of contamination; Post-processing and performance verification stage: After laser shock treatment to ensure product qualification, trace amounts of oxides on the component surface are removed by wiping with a lint-free cloth dampened with analytical grade anhydrous ethanol or acetone (S31) to avoid damaging the strengthened surface. Subsequently, the strengthening effect is verified through multi-dimensional inspections (S32-S35): S32 uses a white light interferometer to detect surface roughness, ensuring the Ra value is controlled within 1-6 μm; S33 uses an X-ray diffraction stress analyzer combined with electrolytic peeling technology to detect residual stress on the surface and subsurface layers, ensuring… The compressive stress layer depth is ≥200μm; the S34 "micro Vickers hardness tester" tests the hardness at different depths under a 0.3kgf load, ensuring that the hardness is 15%-35% higher than that of the additive manufacturing state; the S35 "optical microscope / scanning electron microscope" observes the surface microstructure to ensure that there is no molten recast layer, microcracks or other damage; only parts that meet all the test standards can be put into the warehouse for use in the combustion chamber assembly of aero engines or gas turbines. Parts that do not meet the standards need to be analyzed for the reasons, and the parameters need to be adjusted and then re-strengthened (only once, to avoid excessive plastic deformation).

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser strengthening method for controlling the surface properties of additive manufacturing components for combustion chambers, characterized in that, Includes the following steps: S1. Preprocessing, S1 includes the following steps: S11. Place the additively manufactured combustion chamber metal parts in a vacuum or protective atmosphere heat treatment furnace and perform solution treatment, aging treatment or hot isostatic pressing treatment according to the material of the parts. S12. Surface cleaning is performed using dry sandblasting or electrochemical polishing; S13. After ultrasonic cleaning with deionized water, dehydrate with anhydrous ethanol and dry in an oven. S2, Uncoated Laser Shock Enhancement, S2 includes the following steps: S21. Fix the part processed in S1 onto the five-axis CNC worktable using a special fixture, and position it using a laser displacement sensor or machine vision system. S22. Select an Nd:YAG or Nd:YLF pulsed laser for laser shock; S23. Plan the scanning path based on the 3D CAD model of the combustion chamber components; S3, Post-processing and Performance Verification: S3 includes the following steps: S31. Surface cleaning: Wipe the surface of the component with a lint-free cloth dampened with analytical grade anhydrous ethanol or acetone. S32. Surface morphology and roughness inspection: Ra and Rz values ​​are detected using a white light interferometric surface profilometer. S33. Residual stress detection: X-ray diffraction stress analyzer combined with electrolytic peeling technology is used to detect surface and subsurface residual stress and plot compressive stress layer depth distribution curve. S34. Microhardness testing: Using a micro Vickers hardness tester, the hardness values ​​of the surface and depth directions (one measuring point every 50μm) are measured under a load of 0.3kgf. S35. Microstructure observation: Prepare metallographic samples of the component cross-section and observe the surface microstructure using an optical microscope or scanning electron microscope.

2. The laser strengthening method for surface property control of additive manufacturing components in combustion chambers according to claim 1, characterized in that, In step S11, the hot isostatic pressing parameters are 1100±50℃, 100±10MPa, and heat preservation for 2±0.5 hours.

3. The laser strengthening method for surface property control of additive manufacturing components in combustion chambers according to claim 1, characterized in that, In step S12, dry sandblasting uses 50-150μm spherical ceramic / glass beads, air pressure 0.2-0.5MPa, spray gun distance 100-200mm, and spray angle 45-90°; electrochemical polishing uses 40-70℃ acidic / neutral electrolyte, voltage 10-20V, and processing time 3-10 minutes.

4. The laser strengthening method for surface property control of additive manufacturing components in combustion chambers according to claim 1, characterized in that, In step S13, the ultrasonic cleaning time with deionized water is 10-20 minutes, the oven temperature is 60-80℃, and the drying time is 30-60 minutes.

5. The laser strengthening method for surface property control of additive manufacturing components in combustion chambers according to claim 1, characterized in that, In step S21, the angle between the laser beam and the normal of the surface to be impacted is ≤5°; in step S22, the laser wavelength is 1064nm or 532nm, the pulse energy is 2-15J, the pulse width is 10-30ns, the spot diameter is 2-6mm, and the power density is 0.5-3.0GW / cm². 2 The repetition frequency is 1-10Hz, and the overlap rate is 40-70%. In step S23, the planar area adopts serpentine reciprocating scanning, the curved area adopts equidistant offset scanning, and the closed inner cavity / fine flow channel adopts spiral scanning.

6. The laser strengthening method for surface property control of additive manufacturing components for combustion chambers according to claim 1, characterized in that, In step S22, the thickness of the heat-affected zone on the surface of the component after laser shock is ≤10μm, and there are no visible molten recast layer, microcracks or ablation pits on the surface.

7. The laser strengthening method for surface property control of additive manufacturing components for combustion chambers according to claim 1, characterized in that, In step S12, a plasma cleaning process is added after dry sandblasting: argon or argon-hydrogen mixed plasma is used to bombard the surface of the part, with a processing time of 5-15 minutes and a power of 500-1000W.

8. The laser strengthening method for surface property control of additive manufacturing components for combustion chambers according to claim 1, characterized in that, In step S22, the laser shock process is carried out in an inert gas local protective environment: the inert gas is argon or nitrogen, the gas flow rate is 5-15 L / min, and the gas flow direction is coaxial with the laser beam or blown laterally toward the spot point; the material of the combustion chamber metal component is selected from nickel-based high-temperature alloy, cobalt-based high-temperature alloy or titanium-aluminum alloy.

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