A blade laser cladding process optimization method based on stress compensation strategy

Abstract

The present invention relates to a blade laser cladding process optimization method based on a stress compensation strategy, which divides the blade into sections and clads the front side of the blade. After cladding, the deformation of each measuring point on the front side is tested, and then the back side of the blade is clad. After cladding, the deformation of each measuring point on the back side is tested. The relationship between deformation, stress, and elastic modulus is used to calculate the stress difference between the corresponding areas on the front and back sides. Based on the stress compensation optimization strategy, the stress difference is used to increase or decrease the thermal stress value on the back side of the blade by adjusting the cladding process parameters, thereby optimizing the process parameters when cladding the back side of the blade. Based on the stress compensation strategy, the present invention dynamically adjusts parameters such as power, linear speed, and powder feeding rate during back side cladding, so that the thermal stresses on both sides offset each other, effectively controlling the deformation of the blade, and ensuring dimensional accuracy and quality. At the same time, through regional division and point-by-point measurement, the parameters are differentially adjusted for different areas of the blade, realizing fine control of the cladding process.

Description

Technical Field

[0001] The present invention relates to the technical field of laser cladding, and in particular to a blade laser cladding process optimization method based on a stress compensation strategy. Background Art

[0002] Blades are widely used in aerospace, shipbuilding, and oil transportation, where the working environment is harsh and has strict material, performance, and precision requirements. Laser cladding, as an emerging technology, can form a metallurgically bonded coating on the surface of the workpiece, and can freely select materials to improve the workpiece's wear resistance, corrosion resistance, and high temperature resistance. Laser cladding blade processing has the advantages of extending the service life of the workpiece and reducing costs. However, in general, various impeller blades are relatively thin. During the laser cladding process, due to the thin thickness of the blades, they are easily deformed under the influence of high temperature under the dominance of thermal stress. This deformation will affect the cladding process and product quality.

[0003] From the perspective of the cladding process, blade deformation will cause the distance between the workpiece surface and the laser focus to shift, resulting in uneven laser energy distribution and varying depths of the molten pool, leading to uneven or discontinuous thickness of the cladding layer. At the same time, thermal deformation causes changes in the geometric dimensions of the blade, which reduces the positioning accuracy of the cladding path and easily causes the laser to misalign with the target area, affecting the cladding accuracy. Parameters such as the laser focal length and scanning trajectory need to be repeatedly adjusted to match the deformed surface profile, significantly reducing processing efficiency.

[0004] From the perspective of product quality, laser cladding is used to repair or enhance blade performance. However, thermal deformation will cause the geometric morphology to be inconsistent with the original design, affecting assembly accuracy. At the same time, the bending or warping caused by thermal stress will cause residual stress differences between the cladding layer and the substrate, which can easily lead to failure defects such as cracks and peeling, affecting service life and reliability.

[0005] In summary, the use of appropriate process optimization methods can ensure the smooth progress of laser cladding and obtain a coating with good cladding quality. At the same time, the deformation of the blade can be effectively controlled after the laser cladding is completed. This is a problem that needs to be solved urgently. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a blade laser cladding process optimization method based on a stress compensation strategy.

[0007] The present invention is achieved through the following technical solutions:

[0008] A blade laser cladding process optimization method based on a stress compensation strategy comprises the following steps:

[0009] S1. Laser cladding alloy powder onto metal plates of the same size using different cladding process parameters to obtain a cladding layer of consistent thickness and calculate the thermal stress values ​​under different cladding process parameters.

[0010] S2. The blade includes a front surface and a back surface. N front areas are divided on the front surface of the blade, M front stress measurement points are set in each front area, back stress measurement points are set at positions on the back surface of the blade relative to the front stress measurement points, and N×M back areas are divided on the back surface of the blade relative to each back stress measurement point.

[0011] S3. Scan the original workpiece of the blade using a 3D line scanner to obtain a blade model, and use offline programming software to plan the cladding path on the front of the blade and perform cladding. After the cladding is completed, the deformation of the front area of ​​each of the front stress measurement points is obtained;

[0012] S4. Using a 3D line scanner and offline programming software to plan the cladding path on the reverse side of the blade and perform cladding, after cladding is completed, the deformation of the reverse area of ​​each stress measurement point on the reverse side is obtained;

[0013] S5. Based on the deformation amount of the front area and the deformation amount of the reverse area, calculating the bending stress value of the reverse stress measurement point of each reverse area;

[0014] S6. Re-determine the optimal cladding process parameters for each of the reverse surface regions by combining the bending stress value of each reverse surface region with the thermal stress values ​​under different cladding process parameters.

[0015] According to the above technical solution, preferably, in step S1, the cladding process parameters include line speed (m / min), power (W), and powder feeding rate (g / min), and step S1 includes:

[0016] Using alloy powder to perform laser cladding on metal plates of the same size with different cladding process parameters to obtain a cladding layer with consistent thickness;

[0017] After cladding, the temperature of the metal plate is measured using a thermometer, and the relationship between thermal stress and temperature is used to calculate the thermal stress value under different cladding process parameters.

[0018] σ=E×α×ΔT,

[0019] σ is the thermal stress, in Pa; E is the elastic modulus of the material, in Pa; α is the linear expansion coefficient of the material, in 1 / °C; ΔT is the temperature change, in °C.

[0020] According to the above technical solution, preferably, in step S2, the blade also includes a blade edge located at the clamping edge of the front and back sides of the blade. During cladding, the blade edge is first clad, and then the front and back sides of the blade are clad respectively.

[0021] According to the above technical solution, preferably, step S3 includes:

[0022] Scanning the original workpiece of the blade using a 3D line scanner to obtain a blade model, and planning a cladding path for a first front area of ​​the front side of the blade using offline programming software;

[0023] After each front area is clad, the 3D line scanner is used to scan again and obtain the blade shape and size data in the current state, and the offline programming software is used to adjust the cladding path of the next front area, and so on, until the front of the blade is clad;

[0024] A three-coordinate measuring machine is used to obtain the deformation of the front area of ​​each front stress measurement point.

[0025] According to the above technical solution, preferably, step S5 includes:

[0026] Adding the deformation amounts of the front area and the back area of ​​each of the front stress measurement point and the back stress measurement point to obtain the total deformation amount of the back stress measurement point in each back area;

[0027] The bending stress value of the reverse surface stress measurement point of each reverse surface area is calculated using the relationship between the total deformation, stress, and elastic modulus.

[0028] According to the above technical solution, preferably, step S6 includes:

[0029] Add the bending stress value of each reverse surface area and the thermal stress value under different cladding process parameters, and take the absolute value;

[0030] The cladding process parameter with the smallest absolute value is selected as the adjusted optimal cladding process parameter of the reverse surface area, and cladding is performed on the reverse surface of the blade based on the optimal cladding process parameter of each reverse surface area.

[0031] The beneficial effects of the present invention are:

[0032] The present invention measures the deformation of the front and back surfaces during the cladding process to calculate the stress difference. In combination with a stress compensation strategy, the power, linear speed, powder feed rate and other parameters are dynamically adjusted during the cladding of the back surface, so that the thermal stresses on the two surfaces offset each other. This effectively controls the deformation of the blade, ensures dimensional accuracy and quality, and avoids defects such as cracking, delamination or peeling of the cladding layer caused by excessive local residual stress. The bonding strength between the cladding layer and the substrate is enhanced, the density and integrity of the cladding layer are improved, and the overall structural stability and fatigue life of the blade are improved.

[0033] At the same time, the present invention uses regional division and point-by-point measurement to differentially adjust parameters for different areas of the blade, thereby achieving fine control of the cladding process, avoiding local over-compensation or under-compensation problems caused by traditional global processes, improving process repeatability and controllability, and having high application and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the front area and front stress measurement points of the blade front divided according to the present invention.

[0035] Figure 2 It is a schematic diagram of the reverse area divided by the reverse side of the blade and the reverse side stress measurement points of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and the best embodiment. Based on the embodiments of the invention, all other embodiments obtained by those skilled in the art without making any creative work shall fall within the scope of protection of the invention.

[0037] The present invention comprises the steps of:

[0038] S1. Laser cladding alloy powders on metal plates of the same size using different cladding process parameters to obtain cladding layers of consistent thickness. Calculate the thermal stress values ​​under different cladding process parameters.

[0039] This application is applicable to alloy powders such as iron-based, nickel-based, cobalt-based and composite powders. In this example, an alloy powder (with a chromium content of 18% by mass, an iron content of 2% by mass, a molybdenum content of 18% by mass, a nickel content of 62% by mass, a particle size range of 50-106μm, and dried in a drying oven at 120°C for 2h) is taken as an example to introduce the specific optimization steps of this application.

[0040] Laser cladding was performed using a coaxial powder feeding method. To ensure consistent blade cladding layer formation, the spot size was fixed at 5 mm, and the single-pass traverse was fixed at 2 mm. In conventional laser cladding, the line speed ranged from 0.6 to 1.5 m / min, the power ranged from 900 W to 2400 W, and the powder feed rate ranged from 5 to 30 g. The line speed, laser power, and powder feed rate were adjusted. To achieve a cladding layer thickness of 1 ± 0.05 mm, process parameters were optimized using a single-factor experimental method, as shown in Table 1.

[0041] Table 1

[0042]

[0043] Select processes 4, 5, 6, 10, 12, 13 and 14 with appropriate thickness. Seven groups of processes were clad on seven identical 100×30×6mm 45# steel plates (thickness is close to that of the subsequent test blades), with consistent cladding trajectories and a cladding area of ​​80×15mm (due to the short cladding time, the deformation of the steel plate has little effect on the cladding working distance). After cladding, the temperature was measured using a thermometer, and the relationship between thermal stress and temperature was used to

[0044] σ=E×α×ΔT,

[0045] Where σ is the thermal stress in Pa; E is the elastic modulus of the material in Pa; α is the linear expansion coefficient of the material in 1 / °C; ΔT is the temperature change in °C. In this example, the initial temperature before cladding is 20°C, the elastic modulus of 45# steel is 200 GPa, and the linear expansion coefficient is 12×10 -6 / ℃, the thermal stress values ​​of each area under process numbers 4, 5, 6, 10, 12, 13, and 14 are calculated respectively, and named as σ1, σ2, σ3, σ4, σ5, σ6, and σ7 respectively. The specific thermal stress values ​​are shown in Table 2.

[0046] Table 2

[0047]

[0048] S2. The blade includes a front side, a back side, and a blade edge. N front areas are divided on the front side of the blade, M front stress measurement points are set in each front area, and back stress measurement points are set at positions on the back side of the blade relative to the front stress measurement points. N×M back areas are divided on the back side of the blade relative to each of the back stress measurement points.

[0049] like Figure 1 、 2As shown, in this example, the front side of the blade is divided into 6 small areas (A, B, C, D, E, F), and the back side is divided into 18 areas (A1-3, B1-3, C1-3, D1-3, E1-3, F1-3) at the corresponding positions on the front side. Three front stress measurement points are set in each front area, and a back stress measurement point is set on the back side of the blade relative to the front stress measurement point. The stress value is subsequently calculated using the deformation.

[0050] S3. Use a 3D line scanner to scan the original workpiece of the blade to obtain a blade model, use offline programming software to plan the cladding path on the front of the blade and perform cladding, and after the cladding is completed, obtain the deformation of the front area of ​​each of the front stress measurement points.

[0051] In this example, the cladding process used was process 14, which has a moderate stress value. The line speed was 1.2 m / min, the power was 2100 W, the powder feed was 17.1 g, and the cladding run duration was approximately 3 minutes. The blade edge is located at the edge between the front and back surfaces of the blade. During cladding, the blade edge is first clad, which constrains the subsequent cladding area and reduces overall blade deformation. Cladding is then performed on the front and back surfaces separately.

[0052] It should be noted that the use of a 3D line scanner combined with offline programming for blade laser cladding is currently available. PQArt industrial robot offline programming software is preferred, but not limited to, for blade laser cladding path planning. To address blade deformation during laser cladding, a 3D line scanner combined with offline programming is employed to optimize process parameters while generating a motion program that changes with blade deformation. This effectively addresses the potential for blade deformation-induced changes in working distance and collisions between the blade and the cladding head during cladding, allowing for the complete formation of one blade in a single pass while achieving a high-quality coating.

[0053] Specifically, the initial blade model of the blade workpiece is obtained based on a 3D line scanner, and offline programming software is used to plan the cladding path for the first front area and perform laser cladding. After completing the cladding of the current area and recording the average temperature value of the area, the 3D line scanner is immediately used to perform a global scan of the clad front of the blade to obtain the three-dimensional model of the current state (i.e., the shape and size data of the blade in the current state). After the scan is completed, the blade is insulated with insulation cotton, and based on the current three-dimensional model, the offline programming software is used to perform adaptive path planning for the next front area to ensure that the cladding path matches the actual shape of the blade. The closed-loop process of "scanning → path planning → cladding" is iterated in sequence until the cladding processing of N areas on the front of the blade is completed. In addition, before cladding in each area, the blade is heated as a whole by a flame to the temperature recorded after the cladding of the previous area, and then cladding is performed to ensure consistent heat accumulation.

[0054] After the front cladding of the blade was completed, it was compared with the initial blade model and the front of the blade was tested using a three-coordinate measuring machine (only the change in the z-axis direction was recorded). The deformation of the front area at each front stress measurement point was obtained (mm), as shown in Table 3.

[0055] Table 3

[0056]

[0057] S4. Use a 3D line scanner and offline programming software to plan the cladding path for the back of the blade and perform cladding. After the cladding is completed, obtain the deformation of the back area of ​​each stress measurement point on the back.

[0058] Specifically, after cladding the front side of the blade and cooling to room temperature, cladding was performed on the back side. Following the same method as step S3, 18 back side regions were clad using a combination of a 3D line scanner and offline programming. The deformation (mm) of each of the 18 back side regions after cladding was calculated, as shown in Table 4.

[0059] Table 4

[0060]

[0061] S5. Based on the deformation amount of the front area and the deformation amount of the back area, calculate the bending stress value of the back stress measurement point of each back area.

[0062] Specifically, the deformation amounts of the front area and the deformation amounts of the back area of ​​each of the front stress measurement point and the back stress measurement point are added together to obtain the total deformation amount of the back stress measurement point in each back area, as shown in Table 5.

[0063] Table 5

[0064]

[0065] The total deformation is mainly caused by the inconsistent bending stress difference between the front and back surfaces of the blade. The key is that the deformation of the impeller blade in laser cladding is regarded as the bending of the beam, and the deformation is regarded as the deflection. The formula of deformation and bending moment is:

[0066]

[0067] Where f is the deformation (deflection) of the free end of the blade, in meters (m); M is the bending moment acting on the blade, in Newton meters (N·m); L is the length of the blade, in meters (m); E is the elastic modulus of the material, in Pascals (Pa); I is the moment of inertia of the area, in m 4 .

[0068] The bending stress calculation formula is:

[0069]

[0070] Where σ is the bending stress in Pascals (Pa); M is the bending moment acting on the blade in Newton meters (N m); y is the distance from the neutral axis of the section to the calculation point in meters (m); I is the moment of inertia of the section, that is, the moment of inertia of the section about the neutral axis, in meters 4 .

[0071] The blade cross section is considered as a rectangular cross section, so the distance from the neutral axis of the cross section to the calculation point can be expressed as:

[0072]

[0073] Where h is the blade thickness in meters (m).

[0074] Combining the above formula, we can get:

[0075]

[0076] Using the above formula, the bending stress value of each point in each area can be obtained. The 18 areas are named σ8, σ9, σ10, σ11, σ12, σ13, σ14, σ15, σ16, σ17, σ18, σ19, σ20, σ21, σ22, σ23, σ24, and σ25, as shown in Table 6.

[0077] Table 6

[0078]

[0079] S6. Re-determine the optimal cladding process parameters for each of the reverse surface regions by combining the bending stress value of each reverse surface region with the thermal stress values ​​under different cladding process parameters.

[0080] Specifically, the bending stress value of each reverse area is added to the thermal stress value under different cladding process parameters (thermal stress values ​​of processes 4, 5, 6, 10, 12, 13 and 14), and the absolute value is taken. The thermal stress value of each process is σi (i=1, 2, 3, 4, 5, 6, 7), and the bending stress value of the reverse area is σj (j=8, 9, 10, 11, 12, ..., 23, 24, 25). In order to obtain the best process, its minimum stress value is calculated.

[0081]

[0082] The cladding process parameter with the smallest absolute value is selected as the optimal cladding process parameter after adjustment for the reverse area, as shown in Table 7.

[0083] Table 7

[0084]

[0085] Then, based on the optimal cladding process parameters for each backside region and combined with offline programming for each backside region, the process for each region was adjusted to the above process, and cladding was performed on the backside of the blade. The selected processes for different backside regions and the stress values ​​after stress compensation are shown in Table 8.

[0086] Table 8

[0087]

[0088] Based on the blade laser cladding process optimization method disclosed in this application, blade cladding was performed. First, process 14 with a moderate stress value was selected, with a linear speed of 1.2 m / min, a power of 2100 W, and a powder feed of 17.1 g. Using the existing program, the blade edges were first clad. The six front-side cladding region programs were then merged, and process 14 with a moderate stress value was selected, with a linear speed of 1.2 m / min, a power of 2100 W, and a powder feed of 17.1 g. The entire front side of the blade was clad. The 18 rear-side cladding region programs were then merged, with the individual region processes shown in Table 8, to perform the entire rear side cladding.

[0089] After process optimization, the total deformation of the blade was effectively suppressed, and the total deformation of each area is shown in Table 9.

[0090] Table 9

[0091]

[0092] In summary, the present invention calculates the stress difference by measuring the deformation of the front and back surfaces during the cladding process, and combines the stress compensation strategy to dynamically adjust the power, line speed, powder feeding amount and other parameters during the cladding of the back surface, so that the thermal stresses on both sides offset each other, effectively controlling the deformation of the blade, ensuring dimensional accuracy and quality, and at the same time avoiding defects such as cracking, delamination or peeling of the cladding layer caused by excessive local residual stress, enhancing the bonding strength between the cladding layer and the substrate, improving the density and integrity of the cladding layer, and improving the overall structural stability and fatigue life of the blade. At the same time, the present invention adjusts parameters differentially for different areas of the blade through regional division and point-by-point measurement, achieving fine control of the cladding process, avoiding the problem of local over-compensation or under-compensation caused by traditional global processes, improving process repeatability and controllability, and having high application and promotion value.

[0093] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A blade laser cladding process optimization method based on stress compensation strategy, characterized in that: The steps include: S1. Laser cladding alloy powder onto metal plates of the same size using different cladding process parameters to obtain a cladding layer of consistent thickness and calculate the thermal stress values ​​under different cladding process parameters. S2. The blade includes a front surface and a back surface. N front areas are divided on the front surface of the blade, M front stress measurement points are set in each front area, back stress measurement points are set at positions on the back surface of the blade relative to the front stress measurement points, and N×M back areas are divided on the back surface of the blade relative to each back stress measurement point. S3. Scan the original workpiece of the blade using a 3D line scanner to obtain a blade model, and use offline programming software to plan the cladding path on the front of the blade and perform cladding. After the cladding is completed, the deformation of the front area of ​​each of the front stress measurement points is obtained; S4. Using a 3D line scanner and offline programming software to plan the cladding path on the reverse side of the blade and perform cladding, after cladding is completed, the deformation of the reverse area of ​​each stress measurement point on the reverse side is obtained; S5. Based on the deformation amount of the front area and the deformation amount of the reverse area, calculating the bending stress value of the reverse stress measurement point of each reverse area; S6. Re-determine the optimal cladding process parameters for each of the reverse regions by combining the bending stress value of each reverse region with the thermal stress value under different cladding process parameters; In step S2, the blade further includes blade edges located at the clamping edges of the front and back surfaces of the blade. During cladding, the blade edges are first clad, and then the front and back surfaces of the blade are clad respectively. Step S3 includes: Scanning the original workpiece of the blade using a 3D line scanner to obtain a blade model, and planning a cladding path for a first front area of ​​the front side of the blade using offline programming software; After each front area is clad, the 3D line scanner is used to scan again and obtain the blade shape and size data in the current state, and the offline programming software is used to adjust the cladding path of the next front area, and so on, until the front of the blade is clad; Using a three-coordinate measuring machine to obtain the deformation of the front area of ​​each front stress measurement point; Step S5 includes: Adding the deformation amounts of the front area and the back area of ​​each of the front stress measurement point and the back stress measurement point to obtain the total deformation amount of the back stress measurement point in each back area; Calculating the bending stress value of the reverse stress measurement point of each reverse area by using the relationship among the total deformation, stress and elastic modulus; Step S6 includes: Add the bending stress value of each reverse surface area and the thermal stress value under different cladding process parameters, and take the absolute value; The cladding process parameter with the smallest absolute value is selected as the adjusted optimal cladding process parameter of the reverse surface area, and cladding is performed on the reverse surface of the blade based on the optimal cladding process parameter of each reverse surface area.

2. The blade laser cladding process optimization method based on stress compensation strategy according to claim 1 is characterized in that: In step S1, the cladding process parameters include line speed, power, and powder feeding rate.

3. The blade laser cladding process optimization method based on stress compensation strategy according to claim 2 is characterized in that: Step S1 includes: Using alloy powder to perform laser cladding on metal plates of the same size with different cladding process parameters to obtain a cladding layer with consistent thickness; After cladding, the temperature of the metal plate is measured using a thermometer, and the relationship between thermal stress and temperature is used to calculate the thermal stress value under different cladding process parameters. σ=E×α×ΔT, σ is the thermal stress, in Pa; E is the elastic modulus of the material, in Pa; α is the linear expansion coefficient of the material, in 1 / °C; ΔT is the temperature change, in °C.

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