Method for repairing 4169 high-temperature alloy structural part

Abstract

The invention provides a 4169 high-temperature alloy structural part repairing method, which belongs to the field of casting, and comprises the following steps: 1, carrying out penetrative machining on a defective part, carrying out acid pickling treatment on a machined surface, and removing residues; secondly, the machined inlay body is subjected to acid pickling treatment, and then the inlay body is assembled to the machining part in a liquid nitrogen cold assembly mode and is in close fit with the machining part; thirdly, the inlay body is completely fused and connected to the notch of the structural part; fourthly, the welding seam and the surface of the inlaid body are integrally cleaned in a laser cleaning mode; 5, the surface of the notch is scanned, a three-dimensional point cloud is obtained and converted into a solid model, the model is sliced, a scanning path of laser directional energy deposition is planned, and the scanning strategy is that paths between adjacent layers are in a vertical relation in the plane direction; and 6, carrying out overall recovery on the remaining missing size according to the planned scanning path. The method can be used for accurately repairing the penetrating type defect and the damaged part of the high-temperature alloy structural part.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of casting, in particular to a laser additive manufacturing method for repairing through-type defects and damaged parts of 4169 high-temperature alloy cast structural parts below 10 mm. BACKGROUND

[0002] The 4169 high-temperature alloy is widely used in cast structural parts in the fields of aerospace and energy due to its excellent high-temperature performance (the 4169 high-temperature alloy can maintain stable performance at 600-1200℃), high strength (tensile strength up to 800-1200MPa), and other characteristics. However, in the casting process, these structural parts inevitably have through-type defects and damages such as pores, shrinkage, cracks, etc. due to factors such as fluctuation in smelting purity (pores are prone to occur when the gas content exceeds 0.005%), unstable pouring speed (shrinkage is caused when the flow rate deviation is ±0.5m / s), and poor mold exhaust (the defect rate increases by 30% when the exhaust rate is lower than 5L / min). Once such defects occur, they will have a great negative impact on the performance of the structural parts. In the field of aerospace, for example, the 4169 high-temperature alloy turbine blade needs to withstand high temperature above 1000℃ and high-frequency vibration of thousands of revolutions per minute (the centrifugal force per square centimeter can reach dozens of newtons) during operation. If there is a through-type crack above 0.5mm, the blade may break due to stress concentration during high-speed rotation, and the broken fragments may penetrate the engine case, causing fatal accidents such as engine in-flight shutdown. The engine case, as a key load-bearing component, has a pore above 0.3mm in diameter or a shrinkage above 5% in volume fraction, which will reduce the overall strength of the structure by 20%-30%, and may cause deformation or even rupture during flight, directly threatening flight safety. In the field of energy, the 4169 high-temperature alloy combustion chamber component for gas turbines has through-type defects that can cause gas leakage at a rate of 0.5-2 cubic meters per hour, which not only reduces the combustion efficiency by 5%-10%, but also intensifies the corrosion and wear of the component due to the local temperature being too high (300-500℃), shortening the service life of the equipment by more than 30%.

[0003] Currently, although traditional argon arc welding repair is relatively simple to operate and has low requirements for equipment, it is widely used in the repair of conventional metal structures, but it has defects that are difficult to overcome in the repair of through-type defects of high-performance materials such as 4169 high-temperature alloy. During welding, the energy density of argon arc is low (only 50-100W / mm 2), resulting in a large amount of heat input and a heat-affected zone (HAZ) of 10-15 mm. For 4169 superalloy, the sustained high temperature can cause abnormal grain growth in the material. The original fine grains (5-10 pm) in the as-cast state can grow to 50-100 pm after welding, directly leading to a 15%-20% decrease in high-temperature strength and a more than 25% reduction in high-temperature endurance life, which cannot meet the service requirements of the material under high-temperature working conditions.

[0004] Although plasma spraying repair technology can quickly cover surface defects and has certain advantages in repairing some surface wear and shallow pit defects, it is not effective in dealing with through-type defects. The bonding mode of the coating formed by this technology is a composite of metallurgical and mechanical bonding, with a bonding strength of only 50-80 MPa, which is much lower than the strength of the base material (the tensile strength of 4169 superalloy is ≥900 MPa). Under the action of high-frequency alternating load (such as the rotational vibration of engine blades at thousands of revolutions per minute), stress concentration can easily occur at the interface between the coating and the substrate. After 10 7 cycles, the coating peeling rate is as high as 35% or more. More importantly, the principle of plasma spraying determines that it can only cover surface and near-surface defects and cannot penetrate into the internal area of through-type defects. For cracks or pores with a depth of more than 2 mm, there are still 8%-12% of voids in the internal area of the defects after repair, and the structural integrity and carrying capacity cannot be fundamentally guaranteed.

[0005] Some enterprises use the whole replacement of components to solve the defect problem to avoid repair risks, but this solution has significant drawbacks in economy and timeliness. The production process of 4169 superalloy cast structural parts is complex and requires more than ten key processes such as mold design and manufacturing (5-7 days), vacuum melting (with gas content controlled to ≤0.005%), precise pouring (flow rate deviation controlled to ±0.5 m / s), multi-stage heat treatment (aging temperature accuracy ±10°C), etc. The production cycle is as long as 2-3 months. In terms of cost, the manufacturing cost of a single structural part can be as high as tens of thousands to hundreds of thousands of yuan (e.g., the cost of a single aero-engine case can be 100-200 thousand yuan) depending on the complexity of the structure. Frequent replacement will increase the operation and maintenance cost of the equipment by 40%-60%. At the same time, the long replacement process will cause the equipment to be out of service for a long time. For example, the daily loss of a single aero-engine can be 20-50 thousand yuan, which seriously affects the availability of the equipment.

[0006] In addition, although the existing laser repair technology has certain advantages in surface defect repair, it is mainly aimed at non-penetrating defects such as surface depression and shallow surface cracks, and a mature scheme for repairing penetrating defects has not yet been formed. The main problems are as follows: there is a lack of accurate defect pretreatment means, and traditional manual judgment or simple detection cannot achieve accurate positioning of the boundary of small-size penetrating defects below 10 mm, and the positioning error is often ±0.3 mm; a scientific layered repair strategy has not been established, and a single laser energy parameter cannot adapt to the repair requirements of defects at different depths from the surface to the interior, resulting in problems such as size deviation (more than 0.2 mm) or insufficient bonding strength (only 70%-80% of the matrix) in the repaired part; at the same time, improper control of heat input during the repair process also causes local tissue deterioration, which is difficult to meet the stringent requirements of high-end equipment on the reliability of structural parts.

[0007] Therefore, how to accurately adapt to small-size penetrating defects while considering repair accuracy and material performance has become a key problem in solving the operation and maintenance problems of high-end equipment in the aerospace and energy fields, and it is of great significance to improve the reliability of equipment and reduce operation and maintenance costs. SUMMARY

[0008] One of the main purposes of the present application is to overcome at least one of the above-mentioned defects of the prior art, and to provide a 4169 high-temperature alloy structural part repair method capable of accurately adapting to small-size penetrating defects while considering repair accuracy and material performance.

[0009] To achieve the above-mentioned purposes of the application, the following technical solutions are adopted:

[0010] According to one aspect of the present application, a 4169 high-temperature alloy structural part repair method is provided, comprising the following steps:

[0011] Step 1: Select a 4169 high-temperature alloy cast structural part with a penetrating crack defect, perform penetrating mechanical processing on the defect site according to the standard notch, process the bottom into a vertical structure, process the upper surface into a bevel, and perform pickling treatment on the processed surface to remove residues;

[0012] Step 2: Process an inlay body from 4169 high-temperature alloy of the same material as the structural part, and perform pickling treatment on the processed inlay body, then assemble the inlay body to the processed site by liquid nitrogen cooling, and tightly fit it;

[0013] Step 3: Use laser welding to completely melt and connect the inlay body to the notch of the structural part, perform X-ray detection and ultrasonic detection on the formed weld after welding, and evaluate according to I-grade weld in NB / T 47013;

[0014] Step four, after laser welding is completed and passed inspection, the whole weld and inlay surface is cleaned by laser cleaning;

[0015] Step five, the notch surface is scanned by a laser three-dimensional scanner, three-dimensional point clouds are obtained and converted into a solid model, the model is sliced and processed, and a scanning path of laser directional energy deposition is planned, and the scanning strategy should be that the paths between adjacent layers are perpendicular in the plane direction.

[0016] Step six, the remaining missing size is integrally restored according to the planned scanning path by using a laser directional energy deposition method, the height of the deposited surface layer should be 0.7-1mm higher than the original part design size, and the repaired part is copied by mechanical processing according to the original design size, so that the size precision of the repaired structure meets the use requirements.

[0017] According to one specific embodiment of the present application, in step one, the upper surface is processed into an epitaxial bevel of 45°x1mm.

[0018] According to one specific embodiment of the present application, in step one, the cutting force and cutting parameters of the 4169 high-temperature alloy satisfy the relationship: F C =K C ×A C ; wherein F C is the main cutting force, K C is the cutting force coefficient, A C is the cutting cross-sectional area, for turning processing, A C =f×a p ; wherein f is the feed rate, and a p is the cutting depth.

[0019] According to one specific embodiment of the present application, in step two, the inlay and the machined removed part are transitionally assembled and fitted, and the gap tolerance is ≤0.1mm.

[0020] According to one specific embodiment of the present application, in step two, the assembly gap and the cooling temperature satisfy the thermal expansion and cold contraction relationship: ΔL=L0×a×ΔT; wherein ΔL is the assembly gap compensation, L0 is the length of the restoration body, a is the linear expansion coefficient, and ΔT is the temperature difference.

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

[0022] According to one specific embodiment of the present application, the laser welding energy density satisfies the formula: wherein E is the energy density, P is the laser power, v is the welding speed, and d is the spot diameter.

[0023] According to one specific embodiment of the present application, in the step four, the relationship between the surface roughness and the energy density of the laser cleaning satisfies: Ra=k×E n ; wherein, k is a material coefficient, and n is an index.

[0024] According to one specific embodiment of the present application, in the step five, the relationship between the scanning accuracy and the point cloud density satisfies: ; wherein, δ is the scanning error, and ρ is the point cloud density, when the point cloud density≥50 points / mm 2 , the scanning error≤0.005mm.

[0025] According to one specific embodiment of the present application, in the step six, the deposition layer thickness of the laser directional energy deposition satisfies the formula: ; wherein, k is a process coefficient, m is the powder feeding rate, ρ is the material density, v is the scanning speed, and w is the scanning width.

[0026] From the above technical solution, the 4169 high-temperature alloy structural part repair method of the present application has the following advantages and positive effects:

[0027] The present application can accurately repair the through-type defects and damaged parts of the 4169 high-temperature alloy structural part below 10mm, improve the repair efficiency, reduce the material loss and the performance of the repaired structural part, and at the same time, reduce the repair cost. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 is the front view schematic diagram of the first standard notch in the 4169 high-temperature alloy structural part repair method of the present application.

[0029] Fig. 2 is the sectional view schematic diagram of the first standard notch in the 4169 high-temperature alloy structural part repair method of the present application.

[0030] Fig. 3 is the front view schematic diagram of the second standard notch in the 4169 high-temperature alloy structural part repair method of the present application.

[0031] Fig. 4 is the sectional view schematic diagram of the second standard notch in the 4169 high-temperature alloy structural part repair method of the present application. DETAILED DESCRIPTION

[0032] Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the specification.

[0033] In the following description of the various examples of the application, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration various example structures, systems, and steps that can be practiced in implementing the application. It is to be understood that other specific arrangements of parts, structures, example devices, systems, and steps can be utilized and structural and functional modifications can be made without departing from the scope of the present application. Also, while the terms "top," "bottom," "front," "back," "side," and the like can be used in this specification to describe various example features and elements of the application, these terms are used herein as a shorthand notations for ease of description only. Any of the terms in this specification should not be interpreted as requiring a particular three-dimensional orientation of structures in order to fall within the scope of the application.

[0034] According to one aspect of the present application, there is provided a 4169 high-temperature alloy structural member repair method, comprising the following steps:

[0035] Step one, select a 4169 high-temperature alloy cast structural member with a through crack defect, according to the standard notch to the defect site for through mechanical processing, the bottom is processed into a vertical structure, the upper surface is processed into a bevel, and the processed surface is pickled to remove residues; the notch is shown in Figs. 1 to 4 , which are two different shapes of notches.

[0036] Step two, process the inlay body with the same material as the structural member using 4169 high-temperature alloy, and pickle the processed inlay body, then assemble the inlay body to the processed site by liquid nitrogen cooling, and tightly fit.

[0037] Step three, use laser welding to completely melt and connect the inlay body to the notch of the structural member, and perform X-ray detection and ultrasonic detection on the formed weld after welding, and evaluate according to NB / T 47013 I grade weld.

[0038] Step four, after laser welding is completed and passes the inspection, use laser cleaning to clean the weld and the surface of the inlay body as a whole.

[0039] Step five, use a laser three-dimensional scanner to scan the notch surface, obtain three-dimensional point cloud and convert it into a solid model, slice the model, and plan the scanning path of laser directional energy deposition, the scanning strategy should be that the adjacent layers are perpendicular to each other in the plane direction.

[0040] Step six, using laser direct energy deposition method, according to the planned scanning path, the remaining missing size is recovered as a whole, the height of the deposited surface layer should be higher than the original part design size 0.7-1mm, according to the original design size through mechanical processing to the repair site for copying, so that the size accuracy of the repaired structure meets the use requirements.

[0041] According to one specific embodiment of the present application, in step one, the upper surface is processed into an epitaxial bevel of 45°x1mm.

[0042] According to one specific embodiment of the present application, in step one, the cutting force and cutting parameters of 4169 high-temperature alloy satisfy the relationship: F C =K C ×A C ; wherein, F C is the main cutting force, K C is the cutting force coefficient, A C is the cutting cross-sectional area, for turning processing, A C =f×a p ; wherein, f is the feed amount, a p is the cutting depth.

[0043] According to one specific embodiment of the present application, in step two, the inlay and the machining removed part are transitionally assembled and fitted, and the gap tolerance is ≤0.1mm.

[0044] According to one specific embodiment of the present application, in step two, the assembly gap and the cooling temperature satisfy the thermal expansion and cold shrinkage relationship: ΔL=L0×a×ΔT; wherein, ΔL is the assembly gap compensation, L0 is the length of the prosthesis, a is the linear expansion coefficient, and ΔT is the temperature difference.

[0045] According to one specific embodiment of the present application, in step three, a 5-10mm red copper plate with an outline profile larger than the hole size is used as a substrate for laser welding.

[0046] According to one specific embodiment of the present application, the laser welding energy density satisfies the formula: Wherein, E is the energy density, P is the laser power, v is the welding speed, and d is the spot diameter.

[0047] According to one specific embodiment of the present application, in step four, the relationship between the laser cleaning surface roughness and the energy density satisfies: Ra=k×E n ; wherein, k is the material coefficient, and n is the index.

[0048] According to one specific embodiment of the present application, in step five, the relationship between the scanning accuracy and the point cloud density is: Wherein, δ is the scanning error, and ρ is the point cloud density, when the point cloud density ≥ 50 points / mm 2 , the scanning error ≤ 0.005 mm.

[0049] According to one specific embodiment of the present application, in step six, the deposition layer thickness of the laser directional energy deposition satisfies the formula: Wherein, k is the process coefficient, m is the powder feeding rate, ρ is the material density, v is the scanning speed, and w is the scanning width.

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

[0051] High-precision repair: By defect removal, inlay repair body cooperation and welding, and combined with laser three-dimensional scanning and path planning, the directional energy deposition repair, and then using mechanical processing to restore the original precision size of the repaired part, the repair problem of through defects or damage below 10 mm in large-size cast structural parts is solved. Unlike the existing laser repair technology which relies on manual positioning (error ± 0.3 mm) and single parameter repair, the present technology realizes repair size deviation ≤ 0.1 mm through standardized bevel preprocessing + laser three-dimensional scanning modeling (accuracy ± 0.02 mm) + offline path planning, which improves the accuracy by more than 60% compared with traditional technology.

[0052] Good bonding strength: The combination of 45° bevel design and laser welding, as well as the improvement of surface roughness after laser cleaning, significantly improves the bonding strength between the repair body and the base body. The bonding strength of the repaired part can reach more than 90% of the base material strength, effectively ensuring the mechanical properties of the repaired structural part. Compared with the 15%-20% reduction in joint strength of argon arc welding and the 50-80 MPa bonding strength of plasma spraying, the present technology can restore the joint strength of 4169 high-temperature alloy to ≥ 92% through the composite bonding mechanism of "mechanical assembly pre-fixing + laser metallurgical welding + roughness enhancement occlusion", which is more than 3 times higher than the existing technology.

[0053] Minimal heat-affected zone: During laser welding and laser directional energy deposition, the energy is concentrated and the heat-affected zone is small, which minimizes the impact on the performance of the base material. The high-temperature performance, strength and other key performance indicators of the original material of the repaired 4169 high-temperature alloy structural part remain basically unchanged. Compared with the 10-15 mm heat-affected zone and 5-10 times grain coarsening of argon arc welding, the present technology controls the heat-affected zone to ≤ 3 mm through laser high-energy density (100-500 W / mm 2 ) and precise energy regulation, and the grain size of 4169 high-temperature alloy is maintained at 10-20 μm, and the material performance attenuation rate is ≤ 5%.

[0054] Economic benefits: compared with the traditional processing method, the repair method involved in the present application can maximize the salvage of the defective cast structural part, reduce the product scrap rate, and effectively combine the technical advantages of laser welding and laser additive manufacturing, greatly improving the effective utilization rate and repair efficiency of the material, while also reducing the heat input to a certain extent, reducing the thermal deformation in the repair process, and reducing the subsequent machining allowance. The overall economic benefit is significantly improved. Compared with the overall replacement scheme (cycle 2-3 months, cost several ten thousand yuan / piece), the repair cycle of the present technology is shortened to 7-10 days, the material utilization rate is increased from 40% to more than 85%, and the single-piece repair cost is reduced by 60%-70%; compared with the peeling rate of 35% of the plasma sprayed coating, the component repaired by the present technology has no peeling failure under 10 7 times alternating load, and the operation and maintenance cycle is prolonged by more than 3 times

[0055] The present application will be further described below in conjunction with examples.

[0056] A 4169 high-temperature alloy cast structural part with a through-type crack defect (crack length about 12 mm) was selected, and the defect site had a thickness of about 5 mm.

[0057] (I) Part defect site processing:

[0058] 1. Pretreatment and defect positioning

[0059] Before repair, ultrasonic testing (UT) and penetration testing (PT) were used to confirm the crack start and end position, extension direction and hidden branch, to ensure that the defect was not missed; at the same time, a three-coordinate measuring instrument (accuracy ±0.003 mm) was used to measure the overall size of the component, and the relative position of the defect site and the surrounding reference surface was recorded to provide size correlation reference for subsequent processing and replication. The final confirmation of the crack length is 12.5 mm, and the crack branch width is 8 mm. To ensure the integrity of defect removal, the maximum length of defect removal is determined to be 15 mm, and the width is 10 mm.

[0060] 2. Mechanical processing of the part defect

[0061] A high-precision numerical control machining center (positioning accuracy ±0.005 mm, repeat positioning accuracy ±0.003 mm) was used, together with an AlTiN coated carbide tool (hardness HRC 65 or higher), to perform through cutting removal on the defect site. During the machining process, a micro-lubrication cooling method (plant-based environmentally friendly cutting fluid, flow rate 5-8 mL / min) was used to avoid the influence of high-temperature alloy thermal deformation on accuracy. According to the standard notch pattern of defect removal, the final processing form is strictly controlled:

[0062] Bottom: processed as a vertical plane structure, with a flatness and perpendicularity error of ≤±0.03 mm, to ensure close fit with the bottom of the inlay;

[0063] Upper surface: Processed into 1mm high, 45° inclined bevel, increase the subsequent laser welding fusion area, reduce stress concentration, while facilitating the protection of gas coverage, reduce the risk of oxidation.

[0064] 3. Pickling treatment of machined surface

[0065] The pickling treatment is performed on the plant-based cutting fluid residues, metal debris and oxidation film remaining on the machined surface, and the specific implementation process is as follows:

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

[0067] Pickling operation process:

[0068] Pretreatment: The machined parts are washed with a high-pressure water gun for 5 minutes, focusing on cleaning the machined parts, and washing off dust and large debris;

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

[0070] Neutralization treatment: After cleaning the pickled parts with water, immerse them 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 the parts with deionized water three times (3 minutes each), and then dry the surface of the parts with hot air at 200°C at a wind speed of 1.5 m / s for 10 minutes to ensure that there is no water residue (focus on ensuring that the defect removal part is dry);

[0072] (II) Inlay processing and assembly

[0073] 1. Determination of assembly gap tolerance

[0074] The assembly gap tolerance between the defect removal part and the inlay is calculated based on the thermal expansion compensation and the optimal gap for laser welding (≤0.01mm), and the formula is ΔL=L0×α×ΔT (ΔL is the assembly gap compensation, L0 is the maximum length of the inlay, α is the linear expansion coefficient, and ΔT is the temperature difference):

[0075] L0=15mm (determined according to the maximum length of the defect removal part);

[0076] α=13.3×10 -6 / ℃;

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

[0078] The calculated AL is about 0.044 mm, combined with the best fit clearance of laser welding, the machining size tolerance range of the inlay assembly surface is determined to be 0-0.054 mm.

[0079] 2. Inlay material and processing preparation

[0080] The inlay is machined from 4169 high-temperature alloy material of the same material as the base body, and the machining process adopts a three-step method of "rough machining-semi-finishing-precision grinding":

[0081] Rough machining: remove most of the excess by mechanical machining, leaving 0.4-0.5 mm machining allowance;

[0082] Semi-finishing: milling the approximate shape, leaving a grinding allowance of 0.1-0.2 mm;

[0083] Precision grinding: the mating surface is machined by a numerical control grinding machine (grinding accuracy ±0.002 mm) to ensure that the length, width, and thickness match the cavity size, and the mating surface roughness Ra≤1.6.

[0084] 3. Pickling treatment of inlay after machining

[0085] The mating surface of the machined inlay is pickled to remove residual grinding fluid residues, grinding dust, and local oxidation spots. The specific implementation process is as follows:

[0086] Prepare pickling solution: consistent with the defect site (20% nitric acid + 5% hydrofluoric acid + 75% deionized water);

[0087] Acid pickling operation process:

[0088] Pretreatment: first, place the machined inlay in an ultrasonic cleaner and clean for 5 minutes, the cleaning solution is deionized water, the ultrasonic power is 300 w, and the frequency is 40 kHz, to preliminarily remove the grinding dust;

[0089] Pickling: immerse the inlay completely at room temperature (20-25°C) for 8 minutes, then clean it with deionized water;

[0090] Neutralization of residual acid and drying: immerse the pickled inlay in 5% sodium hydroxide solution for 6 minutes, then rinse it with deionized water three times (3 minutes each time), and finally dry it with hot air at 200°C for 10 minutes, with an air speed of 1.5 m / s;

[0091] 4. Liquid nitrogen cold assembly process

[0092] Preparation before cold mounting: soak the cleaned inlay in 50L, 99.999% pure liquid nitrogen for 8-10 minutes; wipe the cavity matching surface with 99.9% alcohol to confirm that there is no impurity;

[0093] Assembly operation: use a special stainless steel clamp (surface coated with polytetrafluoroethylene to prevent scratching) to quickly take out the inlay, and press it into the cavity within 10 seconds;

[0094] (Three) Laser welding

[0095] 1. Welding equipment and parameter optimization

[0096] Use an industrial robot (repeat positioning accuracy ±0.05mm) to drive the fiber laser welding head (IPG YLS-6000 laser source), wavelength 1070nm, process parameters as follows:

[0097]

[0098] 2. Welding operation and quality detection

[0099] Before welding, fix the component on the special tooling table, set the path (coincide with the groove center line) through the robot teach pendant, and start the program to complete the automatic welding. After welding, detect:

[0100] Appearance detection: the weld after welding is silver white or light yellow, without visible cracks, pores and slag;

[0101] Non-destructive testing: penetrate the weld and heat affected zone to confirm that there is no surface hidden defect.

[0102] (Four) Laser cleaning

[0103] 1. Cleaning equipment and process parameters

[0104] Use a multi-mode pulsed Nd:YAG laser (wavelength 1064nm) to clean the weld and inlay surface after welding to remove the oxide layer and increase the surface roughness, which provides a better adhesion surface for subsequent laser directional energy deposition. The specific parameters are as follows:

[0105] Laser power: 300W (to avoid burning the substrate due to too high power or not removing the oxide skin due to too low power);

[0106] Single pulse energy: 5mJ (energy density 1.5J / cm 2 , meet the oxide skin peeling threshold);

[0107] Scanning width: 20mm (match the defect width and improve efficiency);

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

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

[0110] 3. Verification of cleaning effect

[0111] Visual observation confirmed that there was no residual scale, oil stains, and impurities. Then, the surface roughness detector was used for detection, and the average roughness Ra was approximately 8.0 μm, meeting the requirements.

[0112] (Five) Laser three-dimensional scanning and path planning

[0113] 1. Laser three-dimensional scanning and model processing

[0114] A structured light laser three-dimensional scanner (accuracy ± 0.01 mm, point cloud density ≥ 50 points / mm 2 ) was used to scan the gap surface:

[0115] Pre-scanning calibration: a 25 mm standard ball (accuracy ± 0.001 mm) was used to calibrate the scanner to ensure data accuracy;

[0116] Scanning process: 8-view angle splicing scanning, 30 s for each view angle, and the point cloud was fused by splicing software (accuracy ± 0.005 mm) to form a complete gap point cloud model;

[0117] Model conversion and optimization: the point cloud data was imported into professional processing software, and the entity model was converted through denoising, smoothing, and meshing processing; compared with the original design model, the entity model was optimized to be 0.7-1 mm higher than the original design, reserving the subsequent processing allowance to avoid insufficient size.

[0118] 2. Scanning path planning

[0119] The optimized entity model was imported into the laser directed energy deposition offline programming software for slicing and path planning:

[0120] Slicing processing: slicing along the thickness direction of the component, and the layer thickness was planned as 0.7 mm;

[0121] Scanning strategy: the paths of adjacent layers were perpendicular (n layers X axis, n+1 layers Y axis, angle 90°), so that the welding bead lap joint area was uniform, and the organization was uniform and the performance was not weakened;

[0122] Path verification: the software dynamically simulated the path, checked for no overlap, missed scanning, or interference, and verified the parameters to be exported to the robot control system after verification.

[0123] (Six) Laser directed energy deposition repair and replication: precise filling to restore size and performance

[0124] 1. Deposition equipment and material preparation

[0125] Coaxial powder feeding type laser directed energy deposition equipment (1070 nm fiber laser source, double hopper powder feeder precision ± 0.1 g / min) was used to deposit 4169 high-temperature alloy spherical powder with the following performance indicators:

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

[0127] Sphericity: ≥ 90%;

[0128] Flowability: ≤ 15 s / 50 g.

[0129] 2. Laser directed energy deposition process parameters and process control

[0130] Deposition parameters match substrate material to ensure metallurgical bonding between layers and substrate:

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

[0132] Laser power: 1500 W;

[0133] Scanning speed: 16 mm / s;

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

[0135] Temperature control: Infrared temperature meter (0-1500°C, accuracy ± 1°C) monitors temperature, pauses when the average temperature of the repair area exceeds 600°C, cools to below 300°C with 30 L / min argon and continues, to avoid deformation or grain coarsening.

[0136] 3. Mechanical processing replication and size verification

[0137] After deposition, the size is restored through "rough machining - semi-finishing - finishing - polishing":

[0138] Rough machining: remove excess allowance, reserve 0.3-0.5 mm semi-finishing allowance;

[0139] Semi-finishing: process to near final size, reserve 0.1-0.2 mm finishing allowance;

[0140] Finishing: finishing machining to ensure that the repair size is consistent with the original component (error ≤ 0.01 mm), surface roughness Ra = 1.6 μm;

[0141] Size verification: three-coordinate measuring instrument full-size detection to confirm compliance with design drawing requirements.

[0142] Those skilled in the art to which the present application pertains will appreciate that the specific structures and processes shown in the above detailed description section are merely illustrative and non-limiting. Moreover, those skilled in the art can combine the various technical features shown in the above description in various possible manners to form new technical solutions, or make other modifications, which all belong to the scope of the present application.

Claims

1. A method of repairing a 4169 superalloy structural component, the method comprising: The method comprises the following steps: Step one, select a 4169 high-temperature alloy cast structure with a through crack defect, according to the standard notch, the defect site is processed by mechanical processing, the bottom is processed into a vertical structure, the upper surface is processed into a bevel, and the processed surface is pickled to remove residues; Step two, use 4169 high-temperature alloy of the same material as the structure to process the inlay, and pickle the processed inlay, then assemble the inlay to the processed part by liquid nitrogen cooling, and tightly fit; Step three, use laser welding to completely melt and connect the inlay to the notch of the structure, and perform X-ray detection and ultrasonic detection on the formed weld after welding, and evaluate according to NB / T 47013 I grade weld; Step four, after laser welding is completed and passed, use laser cleaning to clean the weld and the surface of the inlay as a whole; Step five, use a laser three-dimensional scanner to scan the notch surface, obtain three-dimensional point cloud and convert it into a solid model, slice the model, and plan the scanning path of laser directional energy deposition, and the scanning strategy should be that the adjacent layer paths are perpendicular in the plane direction; Step six, use laser directional energy deposition method to restore the remaining missing size as a whole according to the planned scanning path, and the height of the deposited surface layer should be 0.7-1mm higher than the original part design size, and the repaired part is reprofiled by mechanical processing according to the original design size, so that the size accuracy of the repaired structure meets the use requirements.

2. The method of claim 1, wherein: In step one, the upper surface is processed into a 45°×1mm epitaxial bevel.

3. The method of claim 2, wherein: The step one,4169 high-temperature alloy cutting force and cutting parameters meet the relationship:F C =K C ×A C ;Wherein, F C For the main cutting force, K C Cutting force coefficient, A C Cutting area, for turning, A C =f×a p ;Wherein, f for the feed, a p Cutting depth.

4. The method of claim 1, wherein: In step two, the inlay is assembled with the removed part with a gap tolerance of ≤0.1mm.

5. The method of claim 4, wherein: In step two, the assembly gap and the cooling temperature meet the thermal expansion and cold shrinkage relationship: ΔL=L0×a×ΔT; Wherein, ΔL is the assembly gap compensation, L0 is the length of the repair body, a is the linear expansion coefficient, and ΔT is the temperature difference.

6. The method of claim 1, wherein: In step three, use a 5-10mm copper plate with an outer contour larger than the opening size as a substrate for laser welding.

7. The method of claim 6, wherein: The laser welding energy density satisfies the formula: wherein E is the energy density, P is the laser power, v is the welding speed, and d is the spot diameter.

8. The method of claim 1, wherein: In the fourth step, the relationship between the surface roughness and the energy density of the laser cleaning satisfies: Ra=k×E n ; wherein k is a material coefficient, and n is an index.

9. The method of repairing a 4169 superalloy structural member of claim 1, wherein: The scanning accuracy and the point cloud density in the fifth step are related as follows: wherein δ is the scanning error, and ρ is the point cloud density; when the point cloud density ≥ 50 points / mm 2 , the scanning error ≤ 0.005 mm.

10. The method of claim 1, wherein: In the step six, the deposition layer thickness of the laser directional energy deposition satisfies the formula: wherein k is a process coefficient, m is a powder feeding rate, p is a material density, v is a scanning speed, and w is a scanning width.

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