A process method for inhibiting porosity in laser cladding deposited layers of aluminum alloy materials

Abstract

The application provides a kind of aluminum alloy material laser cladding deposition layer porosity inhibition process method, it is related to laser additive repair technical field, to solve the problem that the porosity of cladding layer obtained by the existing method is higher, lack of the process method for optimizing the overlap strategy and process parameters between cladding layers simultaneously.The application first determines the process parameters and range that affect the porosity of aluminum alloy material laser cladding deposition layer, carries out single-channel cladding layer single-factor experiment, analyzes the forming law of single-channel cladding layer, and determines the process parameter range of multi-channel multi-layer cladding layer;Then, for different overlap strategies, carry out cladding experiment to determine the optimal inter-cladding layer overlap strategy;Finally, based on the optimal inter-cladding layer overlap strategy and the process parameter range of multi-channel multi-layer cladding layer, carry out multi-channel multi-layer cladding orthogonal experiment to determine the process parameter combination with the lowest porosity.Based on the process parameter combination of the application, a cladding layer with almost no porosity defects can be prepared on the aluminum alloy substrate.

Description

Technical Field

[0001] This invention relates to the field of laser additive repair technology, and more specifically, to a process method for suppressing the porosity of laser cladding deposition layers on aluminum alloy materials. Background Technology

[0002] Laser cladding, also known as directional energy deposition, is a coaxial powder-feed laser metal additive manufacturing technology. Laser cladding can prepare metallurgically bonded coatings on metal surfaces, primarily used for surface repair or strengthening. It has broad application prospects for repairing damaged surfaces of aluminum alloy parts. However, compared to common materials like steel, which are easier to laser clad, aluminum alloy surfaces are prone to oxide film formation, resulting in significant porosity in the cladding layer. If the porosity of the laser cladding layer on aluminum alloy surfaces cannot be effectively suppressed, on the one hand, excessive porosity leads to a non-uniform distribution of the cladding material, rendering tests on its tensile properties, wear resistance, hardness, and other mechanical properties meaningless; on the other hand, excessively high porosity results in performance significantly lower than the substrate, making it unsuitable for repairing aluminum alloy parts. Therefore, scholars in related fields both domestically and internationally have focused on the causes and suppression methods of porosity in laser cladding layers on aluminum alloy surfaces.

[0003] The main causes of porosity in aluminum alloy laser cladding layers include: hollow powder, hydrogen evolution forming pores, protective gas entrainment into the molten pool forming pores, metal element evaporation, and lack of fusion between cladding layers. To suppress porosity, many researchers have adopted various approaches, such as improving powder preparation processes, adding nano-ceramic particles, modifying powder alloying elements, drying powder, providing an argon atmosphere, and applying external electromagnetic fields. Besides these methods, from a process perspective, the overlap strategy and process parameters between cladding layers also significantly affect porosity. The overlap strategy directly impacts the remelting area between the current and previous cladding layers during processing. A suitable overlap strategy can, on the one hand, avoid porosity caused by lack of fusion between cladding layers, and on the other hand, reduce porosity in the overlapping areas of the cladding layers through remelting. Laser power, scanning speed, and powder feed rate are process parameters that control heat input. Insufficient heat input may cause powder to not fuse and form pores. Excessive heat input can reduce the solidification rate of the molten pool, which helps the pores to escape before the molten pool solidifies. On the other hand, it will increase the flow of the molten pool, exacerbate the powder trapping of protective gas into the molten pool, and at the same time, some metal elements will evaporate, resulting in an increase in the porosity of the cladding layer.

[0004] Currently, most methods for reducing the porosity of cladding layers focus on reducing hollow powder, adding nano-ceramic particles, and designing powder material composition. There are no specific methods to optimize the interlayer overlap strategy and process parameters to suppress the porosity of laser cladding deposits on aluminum alloy surfaces. Summary of the Invention

[0005] The technical problem to be solved by this invention is:

[0006] Existing methods yield cladding layers with high porosity, but lack a process method that simultaneously optimizes the overlap strategy and process parameters between cladding layers.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0008] This invention provides a method for suppressing the porosity of laser cladding deposition layers on aluminum alloy materials, comprising the following steps:

[0009] Step 1: Determine the process parameters and ranges that affect the porosity of the laser cladding deposited layer on aluminum alloy materials;

[0010] Step 2: Conduct single-factor experiments on single-pass cladding layers according to the process parameters and ranges, detect the cladding layer cross-section melt height H, melt depth h, melt width W, and total melt height B, establish the relationship between each process parameter and the parameters melt height H, melt depth h, melt width W, and total melt height B, analyze the forming law of single-pass cladding layers, and determine the process parameter range for multi-pass multi-layer cladding layers.

[0011] Step 3: Based on the process parameter range of the multi-layer cladding layer, conduct multi-layer cladding experiments for different overlapping strategies, detect the porosity of the experimental results, and determine the optimal overlapping strategy between cladding layers with the goal of minimizing porosity.

[0012] Step 4: Based on the optimal interlayer overlap strategy and the range of process parameters for multi-pass multi-layer cladding, design an orthogonal experimental scheme with the process parameters as the parameters to be optimized and the minimum porosity of the cladding layer as the objective. Conduct multi-pass multi-layer cladding experiments according to the orthogonal experimental scheme, detect the porosity of the cladding layer under each set of process parameters, and determine the process parameter combination with the lowest porosity.

[0013] Furthermore, the process parameters mentioned in step one include: laser power W, scanning speed mm / s, and powder feeding rate mg / min.

[0014] Furthermore, the orthogonal experimental scheme described in step four is a three-factor, three-level orthogonal experimental design.

[0015] Furthermore, the overlapping strategies described in step three include: superimposed scanning overlapping strategy, that is, the upper single-pass cladding layer overlaps directly above the lower single-pass cladding layer; staggered scanning overlapping strategy, that is, the upper single-pass cladding layer overlaps with the lower single-pass cladding layer in a staggered manner; and cross scanning overlapping strategy, that is, the upper single-pass cladding layer overlaps orthogonally with the lower single-pass cladding layer.

[0016] Furthermore, in the staggered scanning overlap strategy, the width of the overlap portion between each layer is 40% of the weld width of a single cladding layer, and the offset between adjacent layers is 30% of the weld width of a single cladding layer.

[0017] Furthermore, in step three, the porosity is characterized by the proportion of pores in the cladding layer cross-section to the total cross-sectional area of ​​the cladding layer. Specifically, the process involves obtaining an image of the cladding layer cross-section, extracting an image of the stable processing position in the cladding layer as the calculation region image, performing binarization on the calculation region image, and determining the percentage of black pixels in the calculation region to the total number of pixels as the porosity of the cladding layer cross-section.

[0018] Furthermore, in step four, the range is used to evaluate the influence of each process parameter on the porosity of the cladding layer; the variance analysis is used to analyze the significance of the influence of each process parameter on the porosity of the cladding layer, and the influencing factors with a P value less than 0.05 are taken as significant influencing factors.

[0019] Furthermore, after step four is completed, cladding experiments are conducted based on the determined combination of process parameters for the lowest porosity and the optimal cladding layer overlap strategy. The experimental results are compared with the experimental results under other parameters in the orthogonal experiment to verify the accuracy and feasibility of the combination of process parameters.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention discloses a method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials. First, single-pass cladding layer forming rules are analyzed through single-factor experiments, eliminating process parameter ranges unfavorable to multi-pass cladding layer formation, and determining the range of multi-pass, multi-layer process parameters that result in good geometric dimensions of the cladding layer on the aluminum alloy surface, providing a basis for subsequent orthogonal experiments. Then, multi-pass, multi-layer cladding experiments are conducted for different overlapping strategies to select the optimal overlapping strategy between cladding layers. Finally, orthogonal experiments are used to optimize process parameters to suppress the porosity of the cladding layer. Range and variance analyses are performed to determine the degree and significance of the influence of each process parameter on the porosity of the cladding layer, identifying process parameters with significant influence and providing guidance for targeted optimization of process parameters. Based on the principle of porosity formation and suppression in laser cladding deposition layers, this invention can prepare cladding layers with almost no porosity defects on aluminum alloy substrates, providing technical guidance and reference for high-quality additive repair of aluminum alloy parts. Attached Figure Description

[0022] Figure 1 This is a flowchart of the process for suppressing porosity in the laser cladding deposition layer of aluminum alloy materials in this embodiment of the invention;

[0023] Figure 2 This is a schematic diagram of ultra-depth-of-field microscope calibration of cladding layer size in an embodiment of the present invention;

[0024] Figure 3 This illustrates the influence of laser processing parameters on the melt height of the cladding layer in this embodiment of the invention.

[0025] Figure 4 This illustrates the influence of laser processing parameters on the cladding depth in this embodiment of the invention.

[0026] Figure 5 This illustrates the effect of laser processing parameters on the weld width of the cladding layer in this embodiment of the invention.

[0027] Figure 6 This illustrates the influence of laser processing parameters on the total melt height of the cladding layer in this embodiment of the invention.

[0028] Figure 7 The diagram illustrates the scanning strategy in an embodiment of the present invention; wherein, a) is a diagram of the superimposed scanning strategy, b) is a diagram of the staggered scanning strategy, and c) is a diagram of the cross-scanning strategy.

[0029] Figure 8 This is a schematic diagram of the overlap of two adjacent single-layer cladding layers in an embodiment of the present invention;

[0030] Figure 9 The following are comparison diagrams and porosity distribution diagrams of the cladding layers corresponding to different scanning strategies in the embodiments of the present invention; wherein, a) is a comparison diagram of the forming effect and porosity of the cladding layers with different scanning strategies, b) is a cross-sectional diagram of the cladding layer with the superimposed scanning strategy, c) is a cross-sectional diagram of the cladding layer with the staggered scanning strategy, and d) is a cross-sectional diagram of the cladding layer with the cross-scanning strategy.

[0031] Figure 10 These are various pore morphology diagrams in the cladding layer according to embodiments of the present invention; wherein, a) is a morphology diagram of sheet-like pores in the cladding layer, b) is a morphology diagram of fine pores in the cladding layer, and c) is a morphology diagram of large pores in the cladding layer.

[0032] Figure 11 This is a schematic diagram of the image processing procedure for obtaining the porosity of the cladding layer cross section in an embodiment of the present invention; wherein, a) is the original metallographic image of the cladding layer cross section, b) is the image of the cladding layer cross section porosity calculation area after single-channel processing, and c) is the image of the cladding layer cross section porosity calculation area after binarization processing.

[0033] Figure 12 This is a trend diagram of experimental factor levels and porosity in an embodiment of the present invention;

[0034] Figure 13 This is a pore distribution diagram of the aluminum alloy substrate in an embodiment of the present invention;

[0035] Figure 14The above are comparative diagrams of pore distribution in the cladding layer in the embodiments of the present invention. Among them, a) is the pore distribution diagram of cladding layer No. 8 in the orthogonal experiment, and b) is the pore distribution diagram of cladding layer under the process parameter combination with the lowest porosity and the staggered overlapping strategy. Detailed Implementation

[0036] In the description of this invention, it should be noted that the terms "first," "second," and "third" mentioned in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," and "third" may explicitly or implicitly include one or more of that feature.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] Combination Figures 1 to 14 As shown, this invention provides a method for suppressing the porosity of laser cladding deposition layers on aluminum alloy materials, comprising the following steps:

[0039] Step 1: Determine the process parameters and ranges that affect the porosity of the laser cladding deposited layer on aluminum alloy materials. These parameters are: laser power 1700-2000W, scanning speed 6-12mm / s, and powder feed rate 12000-2400mg / min.

[0040] Step 2: Conduct single-factor experiments on single-pass cladding layers according to the process parameters and ranges, detect the cladding layer cross-section melt height H, melt depth h, melt width W, and total melt height B, establish the relationship between each process parameter and the parameters melt height H, melt depth h, melt width W, and total melt height B, analyze the forming law of single-pass cladding layers, and determine the process parameter range for multi-pass multi-layer cladding layers.

[0041] The single-factor experimental design is shown in Table 1.

[0042] Table 1

[0043]

[0044] Note: The values ​​marked with "*" in Table 1 are the values ​​selected for this factor when exploring other variables.

[0045] With laser power P as the variable, starting at 1700W and with a gradient of 100W, the scanning speed v was selected as 6mm / s and 10mm / s respectively, and the powder feeding rate f was selected as 1200mg / min and 2000mg / min respectively, and a single-pass cladding experiment was conducted.

[0046] With scanning speed v as the variable, starting at 6 mm / s and with a gradient of 2 mm / s, laser power P was selected as 1800 W and 2000 W respectively, and powder feeding rate f was selected as 1200 mg / min and 2000 mg / min respectively, and single-pass cladding experiments were conducted.

[0047] With the powder feeding rate f as the variable, starting at 1200 mg / min and with a gradient of 400 mg / min, the laser power P was selected as 1800 W and 2000 W respectively, and the scanning speed v was selected as 6 mm / s and 10 mm / s respectively, and a single-pass cladding experiment was conducted.

[0048] The experimental procedure includes:

[0049] Substrate pretreatment: The ZL105 aluminum alloy test plate is chemically cleaned to remove surface oil, organic matter, and oxide film.

[0050] First, soak the substrate in a 5% NaOH aqueous solution for 5 minutes, followed by a 5-minute soak in a 20% HNO3 aqueous solution. Rinse off any remaining solution with clean water, wipe with anhydrous ethanol, and dry the substrate surface with an air gun. The treated substrate must be tested immediately to prevent re-oxidation.

[0051] Powder material pretreatment: The powder material is AlSi10Mg spherical powder with a particle size of 40-90 μm, which is vacuum dried at 110℃ for 2 h.

[0052] Instrument and equipment inspection and experimental parameters: Check the coaxiality of the laser beam output from the cladding head, whether the powder feeding is stable and smooth, and whether the protective lens has any stains. After confirming that the equipment is normal, adjust the gas pressure to 0.2MPa, exhaust the gas until the internal pressure reaches -3MPa, and then fill with argon gas. Repeat twice. During the cladding test, always maintain the oxygen content below 1%. During laser cladding, the powder carrier gas is 3L / s and the coaxial protective gas is 10L / s to ensure stable powder feeding. Produce light according to the set parameters, and move the CNC test bench to achieve single-pass cladding.

[0053] With a spot diameter of 3.6 mm, the process parameters for single-factor experiments were set, and cladding processing was carried out.

[0054] Experimental Results Detection: The cladding layer obtained in the experiment was cut by wire electrical discharge machining, sanded, and then observed and calibrated using a super depth-of-field microscope. The results are as follows: Figure 2 As shown. In this embodiment, the cladding layer forming effect is represented by melt height, melt width, melt depth, and total melt height. The relationships between each process parameter and the parameters melt height H, melt depth h, melt width W, and total melt height B are established as follows: Figure 3 , 4 As shown in Figures 5 and 6.

[0055] Because multi-pass, multi-layer cladding requires consideration of issues such as molding stability and substrate overheating due to continuous heat input, appropriate adjustments to process parameters are necessary. The forming characteristics of a single-pass cladding layer are analyzed to determine the suitable range of process parameters for multi-pass, multi-layer cladding. The melt height increases significantly with decreasing scanning speed and increasing powder feed rate, and is not significantly affected by laser power. Under various process parameters, the melt height varies from 200 to 1000 μm. If the melt height is too small, the cladding forming efficiency is too low; if the cladding layer is too high, defects increase in the unmelted portion at the overlap. Therefore, the melt height range for multi-pass, multi-layer cladding is selected as 300–800 μm.

[0056] The penetration depth increases with increasing laser power and decreases with increasing powder feed rate. Scanning speed has little effect on the penetration depth. If the penetration depth is too small, less laser energy is input into the substrate, which can easily lead to incomplete fusion defects during multi-pass, multi-layer cladding. If the penetration depth is too large, more laser energy is input into the substrate, which can easily lead to substrate collapse during multi-pass, multi-layer cladding. Therefore, the penetration depth range for multi-pass, multi-layer cladding is selected as 200–500 μm.

[0057] The weld width is less affected by powder feed rate and scanning speed, but more significantly by laser power. When the laser power is 1700W, the weld width is in the range of 2200–2400 μm; when the laser power is 1800W, it is in the range of 2400–2700 μm; when the laser power increases to 1900W, the weld width is 2600–2900 μm; and as the laser power increases to 2000W, the weld width range increases to 2700–3100 μm. A weld width that is too small results in low overlap forming efficiency. Therefore, when overlapping multiple layers of cladding, the weld width range is selected to be 2400–3000 μm.

[0058] The total fusion height increases with increasing laser power, increasing powder feed rate, and decreasing scanning speed. If the total fusion height is too large, incomplete fusion defects are prone to occur at the overlap; if the total fusion height is too small, the efficiency of overlap formation is too low. Therefore, the range of total fusion height is selected as 800–1000 μm for multi-pass, multi-layer cladding overlap.

[0059] According to the forming rules of single-pass cladding layers, when the laser power reaches 1800W or above, the cladding layer width tends to stabilize. At 1700W, the cladding width is relatively small, which is not conducive to the overlapping formation of multi-pass cladding layers. Therefore, the laser power should be selected in the range of 1800-2000W for multi-pass and multi-layer overlapping. When the scanning speed increases to 12mm / s, the cladding layer height and total cladding height decrease sharply. At a laser power of 2000W and a powder feed rate of 1200mg / min, the cladding layer height is less than 250μm and the total cladding height is 720μm. At this time, most of the laser energy is input into the substrate metal, which is not conducive to multi-layer overlapping. During cladding, excessive melting of the cladding layer and the substrate metal can easily occur. Therefore, the scanning speed should be appropriately reduced when performing multi-pass, multi-layer cladding, with the scanning speed range adjusted to 5–11 mm / s. When the powder feed rate is increased from 2000 mg / min to 2400 mg / min, the melting height of the cladding layer increases to 1.5 times that at 2000 mg / min, and the melting depth also decreases. At this time, performing multi-pass, multi-layer cladding will lead to an increase in defects in the unmelted portion at the cladding layer overlap, which is not conducive to preparing a high-quality cladding layer. Therefore, the powder feed rate range should be selected within the range of 1200–2000 mg / min.

[0060] In summary, the process parameters for preparing multi-layer cladding layers are as follows: laser power 1800–2000 W; scanning speed 5–11 mm / s; powder feed rate 1200–2000 mg / min.

[0061] Step 3: Based on the process parameter range of the multi-layer cladding layer, conduct multi-layer cladding experiments for different overlapping strategies, detect the porosity of the experimental results, and determine the optimal overlapping strategy between cladding layers with the goal of minimizing porosity.

[0062] Based on the range of multi-stage and multi-layer process parameters, three sets of process parameters were proposed for experiments: laser power 1900W, powder feed rate 1200mg / min, scanning speed 6mm / s; laser power 2000W, powder feed rate 1600mg / min, scanning speed 6mm / s; and laser power 1900W, powder feed rate 2000mg / min, scanning speed 6mm / s.

[0063] like Figure 7 As shown, the overlapping strategy includes: Figure 7 The overlapping scanning strategy shown in a) is that the upper single-pass cladding layer overlaps directly above the lower single-pass cladding layer; as shown in a) Figure 7 b) The staggered scanning overlap strategy, that is, the upper single-pass cladding layer overlaps with the lower single-pass cladding layer in a staggered manner, and the offset between adjacent layers is 30% of the weld width of the single-pass cladding layer; such as Figure 7 c) illustrates the cross-scanning overlap strategy, where the upper single-pass cladding layer overlaps orthogonally (i.e., cross-scanning) with the lower single-pass cladding layer. Figure 8As shown, the width of the overlap between each layer and each pass in each overlapping strategy is taken as 40% of the weld width of a single cladding layer.

[0064] Based on the proposed three sets of process parameters and three overlapping strategies, cladding experiments were conducted respectively, such as... Figure 11 As shown in a), b), and c), porosity is characterized by the proportion of pores in the cladding layer cross-section to the total cross-sectional area of ​​the cladding layer. First, the cladding layer cross-section is obtained using wire electrical discharge machining (EDM). The cladding layer is then polished using 7000-grit sandpaper to ensure a scratch-free surface and avoid affecting the porosity calculation. An image of the cladding layer cross-section is obtained using a super-depth-of-field microscope. An image of a stable processing position within the cladding layer is extracted as the calculation region image. This calculation region image is binarized, and the percentage of black pixels in the calculation region relative to the total number of pixels represents the porosity of the cladding layer cross-section.

[0065] like Figure 9 The image shows a comparison of the porosity and porosity distribution of the cladding layer cross-section under different overlap parameters: laser power 1900W, scanning speed 6mm / min, and powder feed rate 2000mg / min. Figure 9 As can be seen in a), b), c), and d), the cross-section of the cladding layer of the superimposed scanning overlap strategy and the cross-scanning overlap strategy has obvious pores, and the pores are mainly distributed at the overlap of the cladding layer. There are also many sheet-like pores and large pores. In contrast, the pore pattern of the cross-section of the cladding layer of the misaligned scanning overlap strategy is not obvious, and most of them are small pores.

[0066] like Figure 10 As shown, the porosity can be further explained by classifying it into sheet-like pores, fine pores, and large pores. For sheet-like pores and large pores, it is necessary to improve the melting state of alloy powder in the molten pool by reasonably increasing the laser power, reducing the powder feeding rate, or increasing the scanning speed, so as to reduce the porosity of the cladding layer.

[0067] The calculated porosity of the cladding layers prepared under different process parameters is as follows: the staggered scanning overlap strategy has the lowest porosity, ranging from 0.2% to 0.4%; followed by the cross-scanning overlap strategy, with a porosity between 0.25% and 0.5%, which is significantly affected by process parameters; the repeated stacking scanning overlap strategy has the highest porosity, ranging from 0.4% to 0.6%. Therefore, the optimal overlap strategy between cladding layers is the staggered scanning overlap strategy.

[0068] Step 4: Based on the optimal interlayer overlap strategy and the range of process parameters for multi-pass multi-layer cladding, design an orthogonal experimental scheme with the process parameters to be optimized and the goal of minimizing the porosity of the cladding layer. Conduct multi-pass multi-layer cladding experiments according to the orthogonal experimental scheme, detect the porosity of the cladding layer under each set of process parameters, and determine the process parameter combination with the lowest porosity.

[0069] Nine cladding layer processing experiments were conducted using a three-factor, three-level orthogonal analysis method, based on the influencing factors and the values ​​of each level shown in Table 2.

[0070] Table 2

[0071]

[0072] The orthogonal experimental design scheme and the corresponding porosity results of the cladding layer are shown in Table 3.

[0073] Table 3

[0074]

[0075]

[0076] Table 4 shows the results of the range analysis of the orthogonal experiment.

[0077] Table 4

[0078]

[0079] Table 5 shows the results of the orthogonal experiment variance analysis.

[0080] Table 5

[0081]

[0082] The range value reflects the degree of influence of three factors—laser power, powder feed rate, and porosity—on the porosity of the cladding layer. The larger the range, the greater the influence of the corresponding factor on the porosity result. According to the calculation results in Table 4, laser power has the greatest impact on the porosity of the cladding layer, followed by powder feed rate, while scanning speed has the least impact on the porosity of the cladding layer.

[0083] To investigate whether the effects of the three experimental factors on the porosity of the cladding layer were statistically significant, the variance probability p-value was used for judgment. The significance level α for the orthogonal experiment was set to 0.05. As shown in Table 5, the p-values ​​for laser power and powder feeding rate were both less than 0.05, while the p-value for scanning speed was greater than 0.05. This indicates that, statistically, the porosity of the cladding layer is significantly affected by laser power and powder feeding rate, but less affected by scanning speed.

[0084] The results of range analysis and variance analysis show that, under the parameter range of 1800-2000W laser power, 1200-2000mg / min powder feed rate, and 5-11mm / s scanning speed, laser power and powder feed rate are the main factors affecting the porosity of the cladding layer, and the influence of laser power on porosity is greater than that of powder feed rate.

[0085] The main factors affecting the porosity of the cladding layer are laser power and powder feed rate. To investigate the combination of process parameters for the cladding layer with the lowest porosity, the experimental results were plotted as follows: Figure 12 The graph shows the trend of the average porosity of the influencing factors. Since the minimum porosity is taken as the target value, the lowest point of each factor curve in the graph is taken as the combination of process parameters with the lowest porosity, namely, laser power 1800W and powder feed rate 1600mg / min.

[0086] The casing is made of cast aluminum alloy used in aero-engines, and the porosity distribution of the aluminum alloy substrate is as follows: Figure 13 As shown, the average porosity of three different substrates was calculated to be 1.56%. Cladding experiments were conducted based on the determined minimum porosity combination of process parameters and a staggered overlap strategy. Figure 14 As shown, comparing the experimental results with those of orthogonal experiment number 8, it can be seen that the porosity of the cladding layer under the lowest porosity process parameter combination and the staggered overlapping strategy can be reduced to 0.09%, which is a significant improvement compared to the porosity results of the process parameters before optimization in the orthogonal experiment. Furthermore, this porosity result is 1 / 17 of the substrate porosity (1.56%). It should be noted that the porosity of the laser cladding deposited layer of aluminum alloy materials obtained by existing methods is generally higher than that of the substrate, which makes the effect of aluminum alloy laser additive repair unsatisfactory. In the repair of cast aluminum alloy casings of aero-engines, the porosity of the laser cladding deposited layer is much lower than that of the substrate cast aluminum alloy casing, effectively suppressing the porosity of the aluminum alloy laser cladding deposited layer.

[0087] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials, characterized in that, Includes the following steps: Step 1: Determine the process parameters and ranges that affect the porosity of the laser cladding deposited layer on aluminum alloy materials; Step 2: Conduct single-factor experiments on single-pass cladding layers according to the process parameters and ranges, detect the cladding layer cross-section melt height H, melt depth h, melt width W, and total melt height B, establish the relationship between each process parameter and the parameters melt height H, melt depth h, melt width W, and total melt height B, analyze the forming law of single-pass cladding layers, and determine the process parameter range for multi-pass multi-layer cladding layers. Step 3: Based on the process parameter range of the multi-layer cladding layer, conduct multi-layer cladding experiments for different overlapping strategies, detect the porosity of the experimental results, and determine the optimal overlapping strategy between cladding layers with the goal of minimizing porosity. Step 4: Based on the optimal interlayer overlap strategy and the range of process parameters for multi-pass multi-layer cladding, design an orthogonal experimental scheme with the process parameters as the parameters to be optimized and the minimum porosity of the cladding layer as the objective. Conduct multi-pass multi-layer cladding experiments according to the orthogonal experimental scheme, detect the porosity of the cladding layer under each set of process parameters, and determine the process parameter combination with the lowest porosity. The overlapping strategies described in step three include: superimposed scanning overlapping strategy, in which the upper single-pass cladding layer overlaps directly above the lower single-pass cladding layer; staggered scanning overlapping strategy, in which the upper single-pass cladding layer overlaps with the lower single-pass cladding layer in a staggered manner; and cross scanning overlapping strategy, in which the upper single-pass cladding layer overlaps with the lower single-pass cladding layer at an orthogonal angle.

2. The method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials according to claim 1, characterized in that, The process parameters mentioned in step one include: laser power (W), scanning speed (mm / s), and powder feeding rate (mg / min).

3. The method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials according to claim 2, characterized in that, The orthogonal experimental design described in step four is a three-factor, three-level orthogonal experimental design.

4. The method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials according to claim 1, characterized in that, The width of the overlap portion between each layer in the staggered scanning overlap strategy is 40% of the weld width of a single cladding layer, and the offset between adjacent layers is 30% of the weld width of a single cladding layer.

5. The method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials according to claim 1, characterized in that, In step three, the porosity is characterized by the proportion of pores in the cladding layer cross-section to the total cross-sectional area of ​​the cladding layer. Specifically, the process involves obtaining an image of the cladding layer cross-section, extracting an image of the stable processing position in the cladding layer as the calculation region image, performing binarization on the calculation region image, and determining the percentage of black pixels in the calculation region to the total number of pixels as the porosity of the cladding layer cross-section.

6. The method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials according to claim 1, characterized in that, In step four, the range was used to evaluate the influence of each process parameter on the porosity of the cladding layer; the variance analysis was used to analyze the significance of the influence of each process parameter on the porosity of the cladding layer, and the factors with a P value less than 0.05 were taken as significant influencing factors.

7. The method for suppressing porosity in laser cladding deposition layers of aluminum alloy materials according to claim 1, characterized in that, After step four is completed, cladding experiments are carried out based on the determined combination of process parameters with the lowest porosity and the optimal cladding layer overlap strategy. The experimental results are compared with the experimental results under other parameters in the orthogonal experiment to verify the accuracy and feasibility of the combination of process parameters.

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