4169 high temperature alloy structural member repair method

Abstract

The application provides a 4169 high-temperature alloy structural member repairing method, and belongs to the field of casting, which comprises the following steps: (1) performing through mechanical processing on the defect part, and performing pickling treatment on the processed surface to remove residues; (2) performing pickling treatment on the processed inlay, and then assembling the inlay to the processed part through liquid nitrogen cooling, and tightly matching; (3) completely melting and connecting the inlay to the notch of the structural member; (4) performing overall cleaning on the weld and the surface of the inlay through laser cleaning; (5) scanning the notch surface, obtaining three-dimensional point clouds and converting them into a solid model, performing slice processing on the model, and planning a scanning path of laser directional energy deposition, and the scanning strategy should be that the paths between adjacent layers are perpendicular in the plane direction; and (6) overall restoring the remaining missing size according to the planned scanning path. The application can accurately repair the through defects and damaged parts of the high-temperature alloy structural member.

Description

Technical Field

[0001] This invention relates to the field of casting technology, and in particular to a method for laser-assisted composite repair of through-hole defects and damaged parts of 4169 high-temperature alloy casting structural parts with a diameter of less than 10mm. Background Technology

[0002] Due to its excellent high-temperature performance (4169 high-temperature alloy can maintain stable performance at 600-1200℃) and high strength (tensile strength reaches 800-1200MPa), 4169 high-temperature alloy is widely used in casting structural components in high-end fields such as aerospace and energy. However, during the casting process, due to factors such as fluctuations in melt purity (gas content exceeding 0.005% easily leads to porosity), unstable pouring speed (flow rate deviation of ±0.5m / s can cause shrinkage porosity), and poor mold venting (defect rate increases by 30% when venting rate is below 5L / min), these structural components inevitably suffer from through-type defects and damage, such as porosity, shrinkage porosity, and cracks. Once these defects occur, they will have a significant negative impact on the performance of the structural components. In the aerospace field, taking turbine blades of aero-engines as an example, 4169 high-temperature alloy blades must withstand temperatures exceeding 1000℃ and high-frequency vibrations of thousands of revolutions per minute (centrifugal force per square centimeter can reach tens of Newtons). If a through-crack larger than 0.5mm exists, it can cause the blade to fracture due to stress concentration during high-speed rotation. The fracture fragments may penetrate the engine casing, leading to fatal accidents such as in-flight engine shutdown. As a critical load-bearing component of the engine, the casing, with internal pores larger than 0.3mm in diameter or shrinkage exceeding 5% in volume, can reduce the overall structural strength by 20%-30%, potentially causing deformation or even breakage during flight, directly threatening flight safety. In the energy sector, through-cracks in 4169 high-temperature alloy combustion chamber components used in gas turbines can cause gas leakage, with leakage rates reaching 0.5-2 cubic meters per hour. This not only reduces combustion efficiency by 5%-10% but may also exacerbate corrosion and wear due to excessively high local temperatures of 300-500℃, shortening equipment lifespan by more than 30%.

[0003] Currently, while traditional argon arc welding repair is relatively simple to operate and has low equipment requirements, making it widely used in the repair of conventional metal structures, it faces insurmountable drawbacks in repairing through-hole defects in high-performance materials like 4169 superalloy. During welding, the low energy density of the argon arc (only 50-100 W / mm²) results in extremely high heat input, leading to a heat-affected zone (HAZ) of 10-15 mm. For 4169 superalloy, this sustained high temperature causes abnormal grain growth within the material—the originally uniform and fine grains (5-10 μm in size) coarsen to 50-100 μm in the HAZ after welding, directly resulting in a 15%-20% decrease in high-temperature strength and a more than 25% reduction in high-temperature creep life, failing to meet its service requirements under high-temperature conditions.

[0004] While plasma spraying repair technology can quickly cover surface defects and shows certain advantages in repairing some surface wear and shallow pits, it falls short when dealing with through-type defects. The coating formed by this technology is a composite of metallurgical and mechanical bonding, with a bonding strength of only 50-80 MPa, far lower than the strength of the base material itself (4169 high-temperature alloy tensile strength ≥900 MPa). Under the high-frequency alternating loads experienced by aerospace equipment (such as the rotational vibration of engine blades at thousands of revolutions per minute), stress concentration easily occurs at the coating-substrate interface, leading to further degradation after 10... 7 After one cycle, the coating peeling rate is as high as 35% or more. More importantly, the technical principle of plasma spraying determines that it can only cover surface and near-surface defects and cannot penetrate into the internal area of ​​penetrating defects. For cracks or pores with a depth of more than 2mm, there is still an 8%-12% void rate inside the defect after repair, and the integrity and load-bearing capacity of the structure cannot be fundamentally guaranteed.

[0005] To avoid repair risks, some companies resort to replacing entire components to address defects. However, this approach has significant drawbacks in terms of economy and timeliness. The production process of 4169 high-temperature alloy cast structural components is complex, requiring more than ten key steps, including mold design and manufacturing (5-7 days), vacuum melting (gas content must be controlled ≤0.005%), precision casting (flow rate deviation must be controlled within ±0.5m / s), and multi-stage heat treatment (aging temperature accuracy ±10℃). The production cycle can last 2-3 months. From a cost perspective, the manufacturing cost of a single structural component can range from tens of thousands to hundreds of thousands of yuan depending on the structural complexity (e.g., the cost of a single aero-engine casing can reach 100,000-200,000 yuan). Frequent replacements can increase equipment maintenance costs by 40%-60%. Furthermore, the long replacement cycle leads to prolonged equipment downtime. For example, the daily loss from downtime for a single aero-engine can reach 20,000-50,000 yuan, severely impacting equipment availability.

[0006] Furthermore, while existing laser repair technologies have shown certain advantages in surface defect repair, they are mostly designed for non-penetrating damage such as surface depressions and shallow cracks. A mature solution for repairing penetrating defects has not yet been developed. The main problems are: a lack of precise defect pretreatment methods; traditional manual judgment or simple detection is insufficient for accurately locating the boundaries of small penetrating defects smaller than 10mm, with positioning errors often reaching ±0.3mm; the absence of a scientific layered repair strategy; and the inability of a single laser energy parameter to adapt to the repair needs of defects at different depths from the surface to the interior, leading to dimensional deviations (exceeding 0.2mm) or insufficient bonding strength (only 70%-80% of the substrate) at the repair site; and improper heat input control during the repair process can also cause localized structural degradation, making it difficult to meet the stringent reliability requirements of high-end equipment.

[0007] Therefore, how to accurately adapt to small-sized through-type defects and balance repair accuracy and material performance has become a key issue in solving the maintenance problems of high-end equipment in the aerospace and energy fields, and is of great significance for improving equipment reliability and reducing maintenance costs. Summary of the Invention

[0008] A primary objective of this invention is to overcome at least one of the deficiencies of the prior art and to provide a repair method for 4169 high-temperature alloy structural components that can accurately adapt to small-sized through-type defects and take into account both repair accuracy and material properties.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] According to one aspect of the present invention, a method for repairing 4169 high-temperature alloy structural components is provided, comprising the following steps:

[0011] Step 1: Select a 4169 high-temperature alloy casting structural part with a through-crack defect, perform through-crack machining on the defect area according to the standard cut, machine the bottom into a vertical structure, machine the upper surface into a bevel, and pickle the machined surface to remove residue.

[0012] Step 2: Use 4169 high-temperature alloy, the same material as the structural component, to process the insert. After processing, pickle the insert and then assemble it into the processed part by liquid nitrogen cold fitting, ensuring a tight fit.

[0013] Step 3: Use laser welding to completely fuse the inlay to the cut of the structural component. Perform X-ray and ultrasonic testing on the formed weld after welding, and evaluate it according to Class I weld in NB / T 47013.

[0014] Step 4: After the laser welding is completed and passes inspection, the weld and the surface of the inlay are cleaned using laser cleaning.

[0015] Step 5: Use a laser 3D scanner to scan the notch surface, obtain a 3D point cloud and convert it into a solid model. Slice the model and plan the scanning path for laser directional energy deposition. The scanning strategy should be that the paths between adjacent layers are perpendicular in the planar direction.

[0016] Step 6: Using laser directional energy deposition, restore the remaining missing dimensions according to the planned scanning path. The height of the deposited surface layer should be 0.7-1mm higher than the original part design dimensions. Reshape the repaired part according to the original design dimensions through machining to ensure that the dimensional accuracy of the repaired structural component meets the usage requirements.

[0017] According to a specific embodiment of the present invention, in step one, the upper surface is machined into an extensional bevel of 45° × 1 mm.

[0018] According to a specific embodiment of the present invention, in step one, the cutting force and cutting parameters of the 4169 high-temperature alloy satisfy the following relationship: ;in, The main cutting force, This is the cutting force coefficient. This refers to the cutting cross-sectional area, specifically for turning operations. Where f is the feed rate, a p This represents the cutting depth.

[0019] According to a specific embodiment of the present invention, in step two, the insert and the machining removal part are transitionally assembled and fitted with a clearance tolerance of ≤0.1mm.

[0020] According to a specific embodiment of the present invention, in step two, the assembly gap and the cooling temperature satisfy the relationship of thermal expansion and contraction: ;in, This is the amount of compensation for assembly clearance. For the length of the restoration, The coefficient of linear expansion is 1 / 3. This refers to the temperature difference.

[0021] According to a specific embodiment of the present invention, in step three, a copper plate with an outer contour 5-10 mm larger than the opening size is used as a substrate for laser welding.

[0022] According to a specific embodiment of the present invention, the laser welding energy density satisfies the formula: ;in, For energy density, For laser power, For welding speed, denoted as the diameter of the light spot.

[0023] According to a specific embodiment of the present invention, in step four, the relationship between the surface roughness and energy density of the laser-cleaned surface satisfies: ;in, For material coefficients, It is an index.

[0024] According to a specific embodiment of the present invention, in step five, the relationship between scanning error and point cloud density is as follows: ;in, For scanning error, The point cloud density is ≥50 points / mm², and the scanning error is ≤0.005mm.

[0025] According to a specific embodiment of the present invention, in step six, the thickness of the deposited layer for laser-directed energy deposition satisfies the formula: ;in, This is the process coefficient. For powder delivery rate, For material density, For scanning speed, This represents the scan width.

[0026] As can be seen from the above technical solution, the advantages and positive effects of the 4169 high-temperature alloy structural component repair method of the present invention are as follows:

[0027] This invention can accurately repair through-type defects and damaged parts of 4169 high-temperature alloy structural parts with a diameter of less than 10mm, improve repair efficiency, reduce material consumption and the performance of the repaired structural parts, and reduce repair costs. Attached Figure Description

[0028] Figure 1 This is a front view schematic diagram of the first standard cut in the 4169 high-temperature alloy structural component repair method of the present invention.

[0029] Figure 2 This is a cross-sectional schematic diagram of the first standard cut in the 4169 high-temperature alloy structural component repair method of the present invention.

[0030] Figure 3 This is a front view schematic diagram of the second standard cut in the 4169 high-temperature alloy structural component repair method of the present invention.

[0031] Figure 4 This is a cross-sectional schematic diagram of the second standard cut in the 4169 high-temperature alloy structural component repair method of the present invention. Detailed Implementation

[0032] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0033] In the following description of various examples of the invention, reference is made to the accompanying drawings, which form part of the invention, and in which different exemplary structures, systems, and steps that can implement various aspects of the invention are shown by way of example. It should be understood that other specific embodiments of the components, structures, exemplary devices, systems, and steps may be used, and structural and functional modifications may be made without departing from the scope of the invention. Furthermore, while the terms “top,” “bottom,” “front,” “rear,” “side,” etc., may be used in this specification to describe various exemplary features and elements of the invention, these terms are used herein only for convenience, such as the orientation according to the examples shown in the drawings. Nothing in this specification should be construed as requiring a specific three-dimensional orientation of the structure to fall within the scope of the invention.

[0034] According to one aspect of the present invention, a method for repairing 4169 high-temperature alloy structural components is provided, comprising the following steps:

[0035] Step 1: Select a 4169 high-temperature alloy casting structural part with a through-crack defect. Perform through-crack machining on the defect area according to standard notches. Machin the bottom into a vertical structure and the upper surface into a bevel. Then, perform acid pickling on the machined surface to remove any residue. The notch should look like this. Figures 1 to 4 As shown, these are two different shapes of cuts.

[0036] Step 2: Use 4169 high-temperature alloy, the same material as the structural component, to process the insert. After processing, pickle the insert and then assemble it into the processed part by liquid nitrogen cold fitting, ensuring a tight fit.

[0037] Step 3: Use laser welding to completely fuse the inlay to the cut of the structural component. Perform X-ray and ultrasonic testing on the formed weld after welding, and evaluate it according to Class I weld in NB / T 47013.

[0038] Step 4: After the laser welding is completed and passes inspection, the weld and the surface of the inlay are cleaned using laser cleaning.

[0039] Step 5: Use a laser 3D scanner to scan the notch surface, obtain a 3D point cloud and convert it into a solid model. Slice the model and plan the scanning path for laser directional energy deposition. The scanning strategy should be that the paths between adjacent layers are perpendicular in the planar direction.

[0040] Step 6: Using laser directional energy deposition, restore the remaining missing dimensions according to the planned scanning path. The height of the deposited surface layer should be 0.7-1mm higher than the original part design dimensions. Reshape the repaired part according to the original design dimensions through machining to ensure that the dimensional accuracy of the repaired structural component meets the usage requirements.

[0041] According to a specific embodiment of the present invention, in step one, the upper surface is machined into an extensional bevel of 45° × 1 mm.

[0042] According to a specific embodiment of the present invention, in step one, the cutting force and cutting parameters of the 4169 high-temperature alloy satisfy the following relationship: ;in, The main cutting force, This is the cutting force coefficient. For turning operations, the cutting cross-sectional area is... Where f is the feed rate, a p This represents the cutting depth.

[0043] According to a specific embodiment of the present invention, in step two, the insert and the machining removal part are transitionally assembled and fitted with a clearance tolerance of ≤0.1mm.

[0044] According to a specific embodiment of the present invention, in step two, the assembly gap and the cooling temperature satisfy the relationship of thermal expansion and contraction: ;in, This is the amount of compensation for assembly clearance. For the length of the restoration, The coefficient of linear expansion is 1 / 3. This refers to the temperature difference.

[0045] According to a specific embodiment of the present invention, in step three, a copper plate with an outer contour 5-10 mm larger than the opening size is used as a substrate for laser welding.

[0046] According to a specific embodiment of the present invention, the laser welding energy density satisfies the formula: ;in, For energy density, For laser power, For welding speed, denoted as the diameter of the light spot.

[0047] According to a specific embodiment of the present invention, in step four, the relationship between the surface roughness and energy density of the laser-cleaned surface satisfies: ;in, For material coefficients, It is an index.

[0048] According to a specific embodiment of the present invention, in step five, the relationship between scanning error and point cloud density is as follows: ;in, For scanning error, The point cloud density is ≥50 points / mm², and the scanning error is ≤0.005mm.

[0049] According to a specific embodiment of the present invention, in step six, the thickness of the deposited layer for laser-directed energy deposition satisfies the formula: ;in, This is the process coefficient. For powder delivery rate, For material density, For scanning speed, This represents the scan width.

[0050] The present invention has the following technical effects:

[0051] High-precision repair: By removing defects, fitting and welding inlaid repair parts, and combining laser 3D scanning and path planning with directional energy deposition repair, followed by machining to restore the original dimensional accuracy of the repaired area, this technology solves the problem of repairing through defects or damage less than 10mm in large-sized cast structural components. Unlike existing laser repair technologies that rely on manual positioning (error ±0.3mm) and single-parameter repair, this technology achieves a repair dimensional deviation of ≤0.1mm through standardized bevel preprocessing + laser 3D scanning modeling (accuracy ±0.02mm) + offline path planning, improving accuracy by more than 60% compared to traditional technologies.

[0052] Excellent bonding strength: The combination of the 45° bevel design and laser welding, along with the improved surface roughness after laser cleaning, significantly enhances the bonding strength between the repair and the substrate. The bonding strength at the repair site can reach over 90% of the substrate material's strength, effectively ensuring the mechanical properties of the repaired structure. Compared to the 15%-20% strength reduction in argon arc welding joints and the mere 50-80 MPa bonding strength of plasma spraying, this technology, through a composite bonding mechanism of "mechanical assembly pre-fixation + laser metallurgical welding + roughness-enhanced interlocking," achieves a strength recovery rate of ≥92% for 4169 high-temperature alloy repaired joints, more than three times higher than existing technologies.

[0053] Minimal Heat-Affected Zone (HAZ): During laser welding and laser-directed energy deposition, energy is concentrated and the HAZ is small, minimizing the impact on the properties of the base material. The repaired 4169 high-temperature alloy structural components retain their original high-temperature performance, strength, and other key performance indicators essentially unchanged. Compared to the problems of argon arc welding, where the HAZ reaches 10-15 mm and grain coarsening is 5-10 times, this technology, through high laser energy density (100-500 W / mm²) and precise energy control, controls the HAZ to ≤3 mm, maintains the 4169 high-temperature alloy grain size at 10-20 μm, and achieves a material performance degradation rate of ≤5%.

[0054] Economic Benefits: Compared to traditional methods, the repair method described in this invention can salvage defective cast structural components to the greatest extent possible, reducing product scrap rates. This method effectively combines the advantages of laser welding and laser additive manufacturing, significantly improving material utilization and repair efficiency. It also reduces heat input, minimizes thermal deformation during repair, and reduces subsequent machining allowances, resulting in a significant improvement in overall economic benefits. Compared to a complete replacement solution (cycle 2-3 months, cost tens of thousands of yuan per piece), this technology shortens the repair cycle to 7-10 days, increases material utilization from 40% to over 85%, and reduces the cost per piece by 60%-70%. Compared to the 35% coating peeling rate of plasma spraying repair, the components repaired using this technology have a lower peeling rate after 10 days. 7 No spalling failure under alternating loads, extending maintenance cycle by more than 3 times.

[0055] The present invention will be further described below with reference to the embodiments.

[0056] Select a 4169 high-temperature alloy casting structural component with a through-crack defect (crack length approximately 12 mm) and a defect thickness of approximately 5 mm.

[0057] (a) Handling of defects in parts:

[0058] 1. Preprocessing and Defect Location

[0059] Before repair, ultrasonic testing (UT) and penetrant testing (PT) were used to confirm the crack initiation and termination locations, extension direction, and hidden branches to ensure no defects were missed. Simultaneously, a coordinate measuring machine (accuracy ±0.003mm) was used to measure the overall dimensions of the component and record the relative position of the defect location to surrounding reference surfaces, providing dimensional references for subsequent processing and reshaping. The maximum crack length was ultimately confirmed to be 12.5mm, and the crack branch width to be 8mm. To ensure the completeness of defect removal, the maximum length and width of the removed defect were determined to be 15mm and 10mm, respectively.

[0060] 2. Machining of part defects

[0061] A high-precision CNC machining center (positioning accuracy ±0.005mm, repeatability ±0.003mm) is used, paired with AlTiN-coated carbide cutting tools (hardness HRC 65 or higher), to remove defects through-cutting. The machining process employs a micro-lubrication and cooling method (plant-based environmentally friendly cutting fluid, flow rate 5-8mL / min) to avoid thermal deformation of the high-temperature alloy affecting accuracy. The final machining shape is strictly controlled according to the standard notch pattern for defect removal.

[0062] Bottom: Processed into a vertical plane structure, with flatness and perpendicularity errors ≤ ±0.03mm, ensuring a tight fit with the bottom of the inlay;

[0063] The upper surface is machined to a 1mm high, 45° bevel to increase the fusion area for subsequent laser welding, reduce stress concentration, and facilitate the coverage of protective gas to reduce the risk of oxidation.

[0064] 3. Pickling treatment of machined surfaces

[0065] Pickling is performed on the surface after machining to remove residual plant-based cutting fluid, metal shavings, and oxide film. The specific implementation process is as follows:

[0066] Pickling solution preparation: nitric acid (20%) + hydrofluoric acid (5%) + deionized water (75%);

[0067] Pickling operation procedure:

[0068] Pretreatment: Rinse the machined parts with a high-pressure water gun for 5 minutes, focusing on cleaning the machined areas to remove floating dust and large pieces of debris;

[0069] Pickling: At room temperature (20-25℃), immerse the machined parts in the pickling solution for 10-15 minutes, shaking the parts every 5 minutes to ensure that the acid solution fully contacts the parts without any blind spots. After pickling, rinse the pickled parts with running water for 5 minutes.

[0070] Neutralization treatment: After cleaning the acid-washed area with water, soak it in a 5% sodium hydroxide solution for 8 minutes to neutralize the residual acidic substances and prevent subsequent corrosion.

[0071] Rinsing and drying: Finally, rinse with deionized water 3 times (3 minutes each time). After rinsing, dry the surface of the parts with hot air at 200℃, with a wind speed of 1.5m / s and a drying time of 10 minutes, to ensure that there is no moisture residue (pay special attention to ensuring the drying of the defect-removed parts).

[0072] (ii) Inlay processing and assembly

[0073] 1. Determination of assembly clearance tolerance

[0074] The clearance tolerance between the defect-removed part and the inlay is calculated by combining thermal expansion compensation and the optimal gap (≤0.01mm) for laser welding. The formula is as follows: (ΔL is the assembly clearance compensation amount,) (where α is the maximum length of the inlay, α is the coefficient of linear expansion, and ΔT is the temperature difference).

[0075] =15mm (determined based on the maximum length of defect removal);

[0076] α = 13.3 × 10 -6 / ℃;

[0077] ΔT = 221℃ (room temperature 25℃ - liquid nitrogen temperature - 196℃);

[0078] The calculated value is ΔL≈0.044mm. Based on the optimal fit clearance for laser welding, the machining dimensional tolerance range of the inlay assembly surface is determined to be 0-0.054mm.

[0079] 2. Inlay Material and Processing Preparation

[0080] The insert is made of 4169 high-temperature alloy material, the same material as the base, and the machining process adopts a three-step method of "rough machining - semi-finishing - precision grinding".

[0081] Rough machining: Most of the excess material is removed by machining, leaving a machining allowance of 0.4-0.5mm;

[0082] Semi-finishing: Milling to roughly shape, leaving a grinding allowance of 0.1-0.2mm;

[0083] Precision grinding: CNC grinding machine (grinding accuracy ±0.002mm) is used to process the mating surfaces to ensure that the length, width, and thickness match the cavity dimensions, and the surface roughness Ra≤1.6.

[0084] 3. Pickling treatment after inlay processing

[0085] The mating surfaces of the machined inserts are acid-washed to remove residual grinding fluid, grinding debris, and localized oxide spots. The specific implementation process is as follows:

[0086] Prepare the pickling solution: consistent with the solution used for the defective area (20% nitric acid + 5% hydrofluoric acid + 75% deionized water);

[0087] Pickling operation procedure:

[0088] Pretreatment: First, the machined insert is placed in an ultrasonic cleaner for 5 minutes. The cleaning solution is deionized water, the ultrasonic power is 300w, and the frequency is 40kHz to initially remove the wear debris.

[0089] Pickling: Immerse the mounting completely for 8 minutes at room temperature (20-25℃), then clean it with deionized water;

[0090] Residual acid neutralization and drying: The pickled insert was soaked in 5% sodium hydroxide solution for 6 minutes, then rinsed with deionized water 3 times (3 minutes each time), and finally dried with hot air at 200℃ for 10 minutes at a wind speed of 1.5 m / s;

[0091] 4. Liquid nitrogen cold assembly process

[0092] Preparation before cold mounting: Immerse the cleaned inlay in a 50L, 99.999% pure liquid nitrogen insulated tank for 8-10 minutes; wipe the mating surfaces of the cavity with 99.9% alcohol to confirm that there are no impurities;

[0093] Assembly operation: Use a special stainless steel clamp (coated with polytetrafluoroethylene to prevent scratches) to quickly remove the insert and press it into place within 10 seconds, aligning it with the cavity.

[0094] (III) Laser welding

[0095] 1. Optimization of welding equipment and parameters

[0096] An industrial robot (with a repeatability of ±0.05mm) is used to drive a fiber laser welding head (IPG YLS-6000 laser source), with a wavelength of 1070nm. The process parameters are as follows:

[0097] laser power 4000W Ensure a penetration depth of 5mm (consistent with the defect thickness) to avoid incomplete penetration or excessive power, which could lead to burn-through and coarse grains. Welding speed 35mm / s Reduce the width of the heat-affected zone, decrease thermal deformation, and ensure uniform weld formation. Defocus +3mm (positive defocus) The focal spot is positioned above the workpiece to increase the spot area, making the weld seam smoother and preventing overheating at the bottom. The focal spot diameter is 0.67mm. Protective gas and flow rate 99.99% argon gas, 10-15 L / min Dual-path protection: Main gas 12-15L / min covers the molten pool, back gas 10-12L / min prevents back oxidation and isolates air.

[0098] 2. Welding operations and quality inspection

[0099] Before welding, the components are fixed on a dedicated tooling table. The path is set via a robot teach pendant (aligned with the bevel centerline), and the program is started to complete the automated welding. Post-weld inspection:

[0100] Visual inspection: The weld after welding is silvery white or light yellow, with no visible cracks, pores, or slag inclusions;

[0101] Non-destructive testing: Penetrant testing (PT) of welds and heat-affected zones to confirm the absence of latent surface defects.

[0102] (iv) Laser cleaning

[0103] 1. Cleaning equipment and process parameters

[0104] A multimode pulsed Nd:YAG laser (wavelength 1064nm) was used to perform laser cleaning on the weld seam and inlay surface after welding to remove the oxide layer and increase the surface roughness, providing a better adhesion surface for subsequent laser-directed energy deposition. Specific parameters are as follows:

[0105] Laser power: 300W (avoid excessive power that could burn the substrate or insufficient power that would fail to remove the oxide scale).

[0106] Single pulse energy: 5mJ (energy density 1.5J / cm², meeting the oxide scale removal threshold).

[0107] Scan width: 20mm (to match defect width and improve efficiency);

[0108] Scanning speed: 500 mm / s (to control energy per unit area and avoid overheating of the substrate);

[0109] Pulse frequency: 20kHz (to ensure continuous scanning without blind spots).

[0110] 3. Verification of cleaning effect

[0111] Visual inspection confirmed the absence of residual oxide scale, oil stains, and impurities. Further surface roughness testing using a surface roughness tester showed an average roughness Ra≈8.0μm, meeting the requirements.

[0112] (v) Laser 3D Scanning and Path Planning

[0113] 1. Laser 3D Scanning and Model Processing

[0114] The notch surface was scanned using a structured light laser 3D scanner (accuracy ±0.01mm, point cloud density ≥50 points / mm²).

[0115] Pre-scan calibration: Calibrate the scanner using a 25mm standard ball (accuracy ±0.001mm) to ensure data accuracy;

[0116] Scanning process: 8 views are stitched together for 30 seconds each. The stitching software (accuracy ±0.005mm) merges the point clouds to form a complete notch point cloud model.

[0117] Model conversion and optimization: Point cloud data is imported into professional processing software and converted into a solid model after denoising, smoothing, and meshing. Compared with the original design model, the height of the solid model is optimized to be 0.7-1mm higher than the original design to reserve the subsequent processing allowance and avoid insufficient size.

[0118] 2. Scanning Path Planning

[0119] The optimized solid model is imported into laser directional energy deposition offline programming software for slicing and path planning:

[0120] Slicing process: Slice along the thickness direction of the component, with a layer thickness planned at 0.7mm;

[0121] Scanning strategy: The paths of adjacent layers are perpendicular (n layers X-axis, n+1 layers Y-axis, with an angle of 90°) to make the weld overlap area uniform and avoid uneven structure and performance weakening;

[0122] Path verification: The software dynamically simulates the path to check for overlaps, missed scans, or interference. Once the verification is successful, the parameters are exported to the robot control system.

[0123] (vi) Laser-guided energy deposition repair and restoration: precise filling, restoration of size and performance

[0124] 1. Preparation of deposition equipment and materials

[0125] Using a coaxial powder-feeding laser-guided energy deposition system (1070nm fiber laser source, dual-hopper powder feeder with an accuracy of ±0.1g / min), the performance indicators of the 4169 high-temperature alloy spherical powder for deposition are as follows:

[0126] Particle size distribution: 53-150 μm;

[0127] Sphericity: ≥90%;

[0128] Flowability: ≤15s / 50g.

[0129] 2. Laser-Directed Energy Deposition Process Parameters and Process Control

[0130] Deposition parameters are matched with the substrate material to ensure metallurgical bonding between the interlayer and the substrate.

[0131] Powder feeding rate: 50g / min;

[0132] Laser power: 1500W;

[0133] Scanning speed: 16 mm / s;

[0134] Protective gas: 99.99% argon (powder carrier gas 5-8L / min, coaxial protective gas 15-20L / min);

[0135] Temperature control: The infrared thermometer (0-1500℃, accuracy ±1℃) monitors the temperature. When the average temperature of the repair area exceeds 600℃, the process is paused and cooled to below 300℃ with argon gas at a rate of 30L / min before continuing, in order to avoid deformation or coarse grains.

[0136] 3. Machining replication and dimensional verification

[0137] After deposition, the dimensions are restored through "rough machining - semi-finishing - fine grinding - polishing".

[0138] Rough machining: Remove excess material and leave a 0.3-0.5mm allowance for semi-finishing;

[0139] Semi-finishing: Machining to near the final size, with a 0.1-0.2mm finishing allowance;

[0140] Fine grinding: Fine grinding process to ensure that the repaired dimensions are consistent with the original component (error ≤ 0.01mm), and the surface roughness Ra = 1.6μm;

[0141] Dimensional verification: The coordinate measuring machine is used for full-dimensional inspection to confirm that it meets the requirements of the design drawings.

[0142] Those skilled in the art should understand that the specific structures and processes shown in the above detailed embodiments are merely exemplary and not restrictive. Furthermore, those skilled in the art can combine the various technical features described above in various possible ways to form new technical solutions or make other modifications, all of which fall within the scope of this invention.

Claims

1. A method for repairing 4169 high-temperature alloy structural components, characterized in that, Includes the following steps: Step 1: Select a 4169 high-temperature alloy casting structural part with a through-crack defect, perform through-crack machining on the defect area according to the standard cut, machine the bottom into a vertical structure, machine the upper surface into a bevel, and pickle the machined surface to remove residue. Step 2: Use 4169 high-temperature alloy, the same material as the structural component, to process the insert. After processing, pickle the insert and then assemble it into the processed part by liquid nitrogen cold fitting, ensuring a tight fit. Step 3: Using laser welding, the inlay is completely fused and connected to the cut of the structural component. The weld seam is then subjected to X-ray and ultrasonic testing. According to the Class I weld evaluation in NB / T 47013, the laser welding energy density satisfies the formula: ;in, For energy density, For laser power, For welding speed, The diameter of the light spot; Step 4: After the laser welding is completed and passes inspection, the weld and the surface of the inlay are cleaned using laser cleaning. Step 5: Use a laser 3D scanner to scan the notch surface, acquire a 3D point cloud, convert it into a solid model, slice the model, and plan the scanning path for laser directional energy deposition. The scanning strategy should ensure that the paths between adjacent layers are perpendicular in the planar direction. The relationship between scanning error and point cloud density is as follows: ;in, For scanning error, Point cloud density; Step 6: Using laser directional energy deposition, restore the remaining missing dimensions according to the planned scanning path. The height of the deposited surface layer should be 0.7-1mm higher than the original part design dimensions. Reshape the repaired part according to the original design dimensions through machining to ensure that the dimensional accuracy of the repaired structural component meets the usage requirements.

2. The method for repairing 4169 high-temperature alloy structural components according to claim 1, characterized in that: In step one, the upper surface is machined into an extended bevel of 45° × 1 mm.

3. The method for repairing 4169 high-temperature alloy structural components according to claim 2, characterized in that: In step one, the cutting force and cutting parameters of the 4169 high-temperature alloy satisfy the following relationship: ;in, The main cutting force, This is the cutting force coefficient. This refers to the cutting cross-sectional area, specifically for turning operations. Where f is the feed rate, a p This represents the cutting depth.

4. The method for repairing 4169 high-temperature alloy structural components according to claim 1, characterized in that: In step two, the inlay and the machining removal part are fitted together with a clearance tolerance of ≤0.1mm.

5. The method for repairing 4169 high-temperature alloy structural components according to claim 4, characterized in that: In step two, the assembly gap and cooling temperature satisfy the relationship of thermal expansion and contraction: ;in, This is the amount of compensation for assembly clearance. For the length of the restoration, The coefficient of linear expansion is 1 / 3. This refers to the temperature difference.

6. The method for repairing 4169 high-temperature alloy structural components according to claim 1, characterized in that: In step three, a copper plate with an outer contour 5-10mm larger than the opening size is used as a substrate for laser welding.

7. The method for repairing 4169 high-temperature alloy structural components according to claim 1, characterized in that: In step four, the relationship between the surface roughness and energy density of laser cleaning satisfies: ;in, For material coefficients, It is an index.

8. The method for repairing 4169 high-temperature alloy structural components according to claim 1, characterized in that: In step six, the thickness of the deposition layer for laser-directed energy deposition satisfies the formula: ;in, This is the process coefficient. For powder delivery rate, For material density, For scanning speed, This represents the scan width.

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