A system and method for underwater localized dry laser additive repair

Abstract

The application discloses a system and method based on underwater local dry method laser additive repair, the system comprises a controller, a laser, a gas supply device, a laser cladding head, a powder feeder, a moving device, a molten pool monitoring device, the laser is connected with the laser cladding head through an optical fiber, the laser cladding head is connected with the gas supply device, the powder feeder and the moving device, the gas supply device is used for providing inert gas, the powder feeder is used for providing additive powder, and the molten pool monitoring device is used for monitoring the temperature distribution of the molten pool; a drainage device is arranged on the laser cladding head, and the controller is used for setting repair parameters and data processing. The method ensures that the center of the laser cladding head is away from the effective inert gas protection range by a length L p , the effective local dry area by a length L d , and the 400 DEG C high-temperature area of the molten pool by a length L t , and the three lengths are kept as L t ≤ L p , L t ≤ L d , so that the repair area is not oxidized and the repair quality is ensured.

Description

Technical Field

[0001] This invention relates to the field of underwater additive repair technology, and in particular to a system and method for underwater local dry laser additive repair. Background Technology

[0002] Marine engineering equipment is prone to damage due to prolonged exposure to seawater corrosion, the additional load of water currents, and the abrasion of sand currents, necessitating in-situ online repair in underwater environments. Laser additive manufacturing technology can achieve rapid in-situ repair of damaged parts, reducing production costs. However, some repair materials are highly chemically reactive and prone to oxidation, leading to a decline in the quality of the repaired parts. Existing methods to reduce oxidation reactions involve setting up a sealed cavity in the repair processing area, creating an inert atmosphere within the cavity to isolate external oxygen and prevent oxidation of the molten pool. However, the sealed cavity structure occupies a certain amount of space, lacking flexibility when repairing complex and delicate components, which affects the repair effect. Therefore, a new repair device and method are needed to more flexibly avoid the influence of oxygen on the repair process. Summary of the Invention

[0003] Purpose of the invention: To address the above-mentioned shortcomings, this invention provides a system and method for underwater local dry laser additive repair, which can effectively isolate oxygen during the repair process without the need for additional sealing structures.

[0004] Technical Solution: To solve the above problems, this invention employs a system for underwater local dry laser additive repair. The system, characterized by comprising a controller, a laser, a gas supply device, a laser cladding head, a powder feeder, a moving device, and a molten pool monitoring device, wherein the laser is connected to the laser cladding head via an optical fiber, and the laser cladding head is connected to the gas supply device, the powder feeder, and the moving device. The gas supply device provides inert gas, the powder feeder provides additive powder, the moving device moves the laser cladding head, and the molten pool monitoring device monitors the temperature distribution of the molten pool. A drainage device is installed on the laser cladding head, and the controller is used to set repair parameters and process data.

[0005] Furthermore, the laser cladding head includes a cladding nozzle and a drainage device disposed outside the cladding nozzle. An optical lens group is provided at the top of the cladding nozzle, and a cavity is opened in the middle of the cladding nozzle. The laser generated by the laser enters the cavity through the optical lens group and is emitted from the outlet of the cladding nozzle. The cladding nozzle is also provided with an air inlet channel and a powder feeding channel. One end of the air inlet channel is connected to the air supply device, and the other end of the air inlet channel is connected to the cavity. The powder feeding channel is connected to the powder feeder.

[0006] Furthermore, the drainage device includes an outer drainage cover and an inner drainage cover. The inner drainage cover surrounds the outside of the cladding nozzle, and the outer drainage cover surrounds the outside of the inner drainage cover. The inner drainage cover has a first drainage chamber, and the outer drainage cover has a second drainage chamber. The upper inlets of the first drainage chamber and the second drainage chamber are both connected to the gas supply device. The lower outlet axes of the first drainage chamber and the second drainage chamber are coaxial with the axis of the cladding nozzle.

[0007] Furthermore, a flow meter for monitoring the flow rate of each airflow path is installed at the outlet of the gas supply device.

[0008] Furthermore, the molten pool monitoring device is a color CCD camera.

[0009] This invention also provides a repair method using the above system, comprising the following steps:

[0010] Step 1: Obtain the length L of the effective inert gas protection range from the center of the laser cladding head through standard experiments. p Equation 1 shows the relationship between the gas flow rate q of the exhaust device and the exhaust system.

[0011] Step 2: Obtain the length L of the effective localized drying area from the center of the laser cladding head through standard experiments. d Equation 2 shows the relationship between the gas flow rate q of the exhaust device and the exhaust system.

[0012] Step 3: The moving device moves the laser cladding head to the position to be repaired, and sets the initial repair parameters, including laser power, powder feeding rate, and gas flow rate of the drainage device. The controller calculates the initial L based on Equations 1 and 2. p L d The value, L, is obtained by using a molten pool monitoring device to measure the distance L from the center of the laser cladding head to the 400°C high-temperature zone of the molten pool. t Determine whether it meets L t ≤L p And L t ≤L d If the conditions are met, single-layer repair will be performed according to the current settings. If not, the gas flow rate of the drainage device and the laser power will be adjusted until the L value is met. t ≤L p And L t ≤L d After the parameters are set, turn on the laser, gas supply device, laser cladding head, and powder feeder to perform single-layer repair.

[0013] Step 4: Repeat step 3 to repair the next layer until the repair is complete.

[0014] Furthermore, the effective inert gas protection range is set to a region where the oxygen content is within 1000 ppm.

[0015] Further, step one specifically involves: using Fluent software to obtain oxygen content distribution cloud maps on the substrate plane below the drainage device under different gas flow rates, and extracting L under different gas flow rates of the drainage device. p The value is obtained by performing polynomial fitting on the data using a quadratic polynomial. p Equation 1 shows the relationship between the gas flow rate q and the gas flow rate.

[0016] Furthermore, the effective localized drying region is set as a region with a gas volume fraction of 99.99%.

[0017] Furthermore, step two specifically involves: using Fluent software to obtain gas volume fraction distribution cloud maps on the substrate plane below the drainage device under different gas flow rates, and extracting L under different gas flow rates. d The value is obtained by performing polynomial fitting on the data using a quadratic polynomial. d Equation 2 shows the relationship between the gas flow rate q and the flow rate q.

[0018] Furthermore, the length L from the center of the laser cladding head to the 400°C high-temperature zone of the molten pool is obtained through a molten pool monitoring device. t The specific method is as follows: Preliminary experiments are conducted using an infrared thermal imager and a CCD camera to simultaneously capture images of the laser cladding head repair. The distance L from the center of the laser cladding head to the 400℃ high-temperature zone is obtained using the infrared thermal imager. t By adjusting the CCD camera aperture, the distance between the outer edge of the bright circle in the CCD image and the center of the laser cladding head is L. t The grayscale value A and brightness value B of the image at the outer edge of the bright circle are extracted, which are the image parameters of the 400℃ high-temperature area in the CCD camera image. During the restoration process, the CCD camera is used to capture real-time restoration images to obtain the area with grayscale value A and brightness value B. The distance L from the center of the laser cladding head to this area is the value of L. t .

[0019] Beneficial effects: Compared with the prior art, the significant advantage of this invention is that it eliminates the need for an inert gas cavity structure. By adjusting the repair parameters, the repair location is placed in a protective gas atmosphere, ensuring repair quality. It can repair more complex structures and effectively improves the flexibility and applicability of the repair system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the repair system of the present invention;

[0021] Figure 2 This is a cross-sectional view of the laser cladding head of the present invention;

[0022] Figure 3 This is a schematic diagram of the lower structure of the laser cladding head of the present invention;

[0023] Figure 4 This is a cross-sectional view of the lower part of the laser cladding head of the present invention;

[0024] Figure 5 This is a schematic diagram of the repair method of the present invention;

[0025] Figure 6 This is a physical image of the additive repair component of the present invention. Detailed Implementation

[0026] like Figure 1 As shown, this embodiment of a system for underwater local dry laser additive repair includes a controller 1, a laser 2, a gas supply device 4, a laser cladding head 6, a powder feeder 7, a moving device 11, and a molten pool monitoring device 12. The laser 2 is connected to the laser cladding head 6 via an optical fiber 3. The laser cladding head 6 is connected to the gas supply device 4, the powder feeder 7, and the moving device 11. The gas supply device 4 provides inert gas; in this embodiment, the gas supply device 4 is a gas cylinder, and a flow meter is installed at the outlet of the gas cylinder to monitor the flow rate of each gas flow path. The powder feeder 7 provides additive powder. The moving device 11 moves the laser cladding head 6; in this embodiment, the moving device 11 is an industrial robot. The molten pool monitoring device 12 monitors the temperature distribution of the molten pool; in this embodiment, a color CCD camera is used. The controller 1 is used to set repair parameters and process data.

[0027] like Figure 2 and Figure 3 As shown, the laser cladding head 6 includes a cladding nozzle 64 and a drainage device 10 disposed outside the cladding nozzle 64. An optical lens group 62 is provided at the top of the cladding nozzle 64, comprising a collimating protective lens, a collimating lens, a focusing lens, and a focusing protective lens arranged layer by layer from top to bottom. A cavity 67 is opened in the middle of the cladding nozzle 64. The laser generated by the laser 2 enters the cavity 67 through the optical lens group 62 and exits from the outlet of the cladding nozzle 64. The cladding nozzle 64 also has an air inlet channel 61 and a powder feeding channel 63 inside. One end of the air inlet channel 61 is connected to the air supply device 4, and the other end is connected to the cavity 67. The powder feeding channel 63 is connected to the powder feeder 7. Four powder feeding channels 63 are provided on the cladding nozzle 64, and the four powder feeding channels 63 are inclined inward so that their axes intersect at a point, where the laser also converges. This point is the repair position. The laser provides laser energy, the powder feeder delivers powder, the laser and powder converge in the repair area, the laser melts the powder and the repair area to form a molten pool, and the molten pool cools to form a single-layer repair layer.

[0028] The drainage device 10 includes an outer drainage cover 66 and an inner drainage cover 65. The inner drainage cover 65 surrounds the outside of the cladding nozzle 64, and the outer drainage cover 66 surrounds the outside of the inner drainage cover 65. The inner drainage cover 65 has a first drainage chamber, and the outer drainage cover 66 has a second drainage chamber. The upper inlets of the first and second drainage chambers are connected to the gas supply device 4. The lower outlet axes of the first and second drainage chambers are coaxial with the axis of the cladding nozzle 64. The cladding head drainage device adopts a double-layer drainage cover structure, which serves two purposes: drainage and the formation of a local inert atmosphere in the laser cladding area to prevent oxidation of the molten pool during laser cladding.

[0029] like Figure 4 and Figure 5 As shown, this embodiment also provides a repair method using the above-described repair system, employing titanium alloy as the substrate for repair, including the following steps:

[0030] Step 1: Obtain the length L of the effective inert gas protection range from the center of the laser cladding head 6 through standard experiments. p The relationship between the gas flow rate q of the exhaust device and the gas flow rate is given by Equation 1. The effective inert gas protection range is set to the region where the oxygen content is within 1000 ppm. Specifically, the method involves using Fluent software to obtain oxygen content distribution cloud maps on the substrate plane below the exhaust device under different exhaust device gas flow rates, and extracting L under different exhaust device gas flow rates. p The value is obtained by performing polynomial fitting on the data using a quadratic polynomial. p Equation 1 shows the relationship between the gas flow rate q and the average airflow distribution method used in the inner and outer drainage covers of the drainage device in this embodiment. The resulting Equation 1 is as follows:

[0031]

[0032] q represents the total protective gas flow rate, in L / min. p The unit is mm.

[0033] Step 2: Obtain the length L of the effective localized drying area from the center of the laser cladding head 6 through standard experiments. d Equation 2 shows the relationship between the gas flow rate q of the exhaust device and the gas flow rate q. The effective local drying area is defined as a region with a gas volume fraction of 99.99%. Specifically, the method involves using Fluent software to obtain a cloud map of the gas volume fraction distribution on the substrate plane below the drainage device under different drainage device gas flow rates, and extracting L under different gas flow rates. d The value is obtained by performing polynomial fitting on the data using a quadratic polynomial. d Equation 2: Relationship with gas flow rate q

[0034]

[0035] q represents the total protective gas flow rate, in L / min. d The unit is mm.

[0036] Step 3: The moving device 11 moves the laser cladding head 6 to the position to be repaired, and sets the initial repair parameters, including laser power, powder feeding rate, and gas flow rate of the drainage device. The controller 1 calculates the initial L based on equations one and two. p L d value.

[0037] The length L from the center of the laser cladding head to the 400℃ high-temperature zone of the molten pool is obtained by the molten pool monitoring device 12. t The specific method is as follows: A preliminary experiment was conducted using an infrared thermal imager and a CCD camera to simultaneously capture images of the laser cladding head 6 being repaired. The distance L from the center of the laser cladding head to the 400℃ high-temperature zone was obtained using the infrared thermal imager. t By adjusting the CCD camera aperture, the distance between the outer edge of the bright circle in the CCD image and the center of the laser cladding head 6 is L. t The grayscale value A and brightness value B of the image at the outer edge of the bright circle are extracted, which are the image parameters of the 400℃ high-temperature area in the CCD camera image. During the restoration process, the CCD camera is used to capture real-time restoration images to obtain the area of ​​grayscale value A and brightness value B. The distance from the center of the laser cladding head 6 to this area is L. t .

[0038] Determine if it meets L t ≤L p And L t ≤L d If the conditions are met, single-layer repair is performed according to the current settings. If not, the gas flow rate and laser power of the drainage device are adjusted. In this embodiment, the initial laser power is 2200W, the protective gas flow rate is 120L / min, and the protective gas flow rates of both the inner and outer drainage covers are 60L / min. p L d The diameters are 18.01 mm and 20.64 mm, respectively. L p L d The adjustment is made by changing the total gas flow rate of the exhaust system, L t Adjust the laser power until L is satisfied. t ≤L p And L t ≤L d .

[0039] After setting the parameters, turn on the laser 2, gas supply device 4, laser cladding head 6, and powder feeder 7 for single-layer repair. Typically, the air flow rate of the inlet channel 61 is set to 15~25 L / min, the powder-carrying gas flow rate to 5~10 L / min, and the total flow rate of the protective gas from the inner and outer drainage covers to 70~130 L / min. Since the total flow rate of the protective gas is much greater than that of the inlet channel and the powder-carrying gas, this embodiment does not consider the influence of these two gas flows on the inert gas atmosphere range during repair. Furthermore, these two gas flows can help expand the inert gas range; therefore, if only the airflow of the drainage device is considered, the expected effect can be achieved, and the actual effect is even better.

[0040] Step 4: Repeat step 3 to repair the next layer until the repair is complete. This embodiment involves 10 horizontal passes and 10 vertical layers of TC4 titanium alloy laser additive manufacturing. Based on the melt pool monitoring system results, L... t Exceeding L when the number of sedimentary layers is 3, 6, and 8. p L d Therefore, the laser power was reduced to 2150W, 2100W and 2070W in 3 layers, 6 layers and 8 layers respectively, and finally a titanium alloy additive part of 90mm×20mm×8mm was obtained.

[0041] Figure 6 The image shows a photograph of TC4 titanium alloy manufactured using underwater laser additive manufacturing. As can be seen from the image, the surface of the titanium alloy additive part is bright silvery-white, indicating that the molten pool was protected by a localized inert atmosphere and a localized dry zone during the deposition process, resulting in minimal oxidation and good forming quality. Samples were taken from the upper, middle, and lower parts of the titanium alloy additive part, and the oxygen, nitrogen, and hydrogen contents were measured using an oxygen, nitrogen, and hydrogen analyzer. The results are shown in Table 1. Table 1 shows that the oxygen, nitrogen, and hydrogen contents at various points inside the titanium alloy additive part are all lower than the national standard GB / T 3620.1-2016 (oxygen content ≤2000ppm, nitrogen content ≤500ppm, hydrogen content ≤150ppm). This indicates that the underwater localized dry laser additive manufacturing method of this invention can achieve continuous deposition forming of titanium alloys in an underwater environment. Under the action of the protective gas, a localized inert forming atmosphere and a localized dry zone can be formed, resulting in good forming quality and minimal oxidation of the additively manufactured part.

[0042] Table 1. Oxygen, nitrogen, and hydrogen content at different locations in TC4 titanium alloy additive parts.

[0043] Sampling location upper position Central position lower position Oxygen content (ppm) 971.4 966.4 954.2 Nitrogen content (ppm) 18.47 18.25 17.95 Hydrogen content (ppm) 32.24 31.74 30.25

Claims

1. A system for underwater local dry laser additive repair, characterized in that, The device includes a controller (1), a laser (2), a gas supply device (4), a laser cladding head (6), a powder feeder (7), a moving device (11), and a molten pool monitoring device (12). The laser (2) is connected to the laser cladding head (6) via an optical fiber (3). The laser cladding head (6) is connected to the gas supply device (4), the powder feeder (7), and the moving device (11). The gas supply device (4) is used to provide inert gas, the powder feeder (7) is used to provide additive powder, the moving device (11) is used to move the laser cladding head (6), and the molten pool monitoring device (12) is used to monitor the temperature distribution of the molten pool. A drainage device (10) is provided on the laser cladding head (6), and the controller (1) is used to set repair parameters and process data.

2. The system for underwater local dry laser additive repair as described in claim 1, characterized in that, The laser cladding head (6) includes a cladding nozzle (64) and a drainage device located outside the cladding nozzle (64). An optical lens group (62) is provided on the top of the cladding nozzle (64). A cavity (67) is opened in the middle of the cladding nozzle (64). The laser generated by the laser (2) enters the cavity (67) through the optical lens group (62) and is emitted from the outlet of the cladding nozzle (64). The cladding nozzle (64) is also provided with an air inlet channel (61) and a powder feeding channel (63). One end of the air inlet channel (61) is connected to the air supply device (4), and the other end of the air inlet channel (61) is connected to the cavity (67). The powder feeding channel (63) is connected to the powder feeder (7).

3. The system for underwater local dry laser additive repair as described in claim 1, characterized in that, The drainage device (10) includes an outer drainage cover (66) and an inner drainage cover (65). The inner drainage cover (65) surrounds the outside of the cladding nozzle (64), and the outer drainage cover (66) surrounds the outside of the inner drainage cover (65). The inner drainage cover (65) has a first drainage chamber, and the outer drainage cover (66) has a second drainage chamber. The upper inlets of the first drainage chamber and the second drainage chamber are connected to the gas supply device (4). The lower outlet axes of the first drainage chamber and the second drainage chamber are coaxial with the axis of the cladding nozzle (64).

4. The system for underwater local dry laser additive repair as described in claim 1, characterized in that, The outlet of the gas supply device (4) is equipped with a flow meter for monitoring the flow rate of each airflow path, and the molten pool monitoring device (12) is a color CCD camera.

5. A repair method using the system as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Obtain the length L of the effective inert gas protection range between the center of the laser cladding head (6) and the center through standard experiments. p Equation 1 shows the relationship between the gas flow rate q of the exhaust device and the exhaust system. Step 2: Obtain the length L of the effective local dry area from the center of the laser cladding head (6) through standard experiments. d Equation 2 shows the relationship between the gas flow rate q of the exhaust device and the exhaust system. Step 3: The moving device (11) moves the laser cladding head (6) to the position to be repaired, sets the initial repair parameters, including laser power, powder feeding rate, and gas flow rate of the drainage device. The controller (1) calculates the initial L according to Equation 1 and Equation 2. p L d The value is obtained by using the molten pool monitoring device (12) to measure the length L of the laser cladding head center from the 400℃ high-temperature zone of the molten pool. t Determine whether it meets L t ≤L p And L t ≤L d If the conditions are met, single-layer repair will be performed according to the current settings. If not, the gas flow rate of the drainage device and the laser power will be adjusted until the L value is met. t ≤L p And L t ≤L d After the parameters are set, turn on the laser (2), gas supply device (4), laser cladding head (6), and powder feeder (7) to perform single-layer repair; Step 4: Repeat step 3 to repair the next layer until the repair is complete.

6. The repair method as described in claim 5, characterized in that, The effective inert gas protection range is set to the area where the oxygen content is within 1000 ppm.

7. The repair method as described in claim 6, characterized in that, Step one specifically involves: using Fluent software to obtain oxygen content distribution cloud maps on the substrate plane below the drainage device under different gas flow rates, and extracting L under different gas flow rates of the drainage device. p The value is obtained by performing polynomial fitting on the data using a quadratic polynomial. p Equation 1 shows the relationship between the gas flow rate q and the gas flow rate.

8. The repair method as described in claim 5, characterized in that, The effective localized drying zone is defined as a region with a gas volume fraction of 99.99%.

9. The repair method as described in claim 8, characterized in that, Step two specifically involves: using Fluent software to obtain gas volume fraction distribution cloud maps on the substrate plane below the drainage device under different gas flow rates, and extracting L under different gas flow rates. d The value is obtained by performing polynomial fitting on the data using a quadratic polynomial. d Equation 2 shows the relationship between the gas flow rate q and the flow rate q.

10. The repair method as described in claim 5, characterized in that, The length L of the laser cladding head center from the 400℃ high-temperature zone of the molten pool is obtained by the molten pool monitoring device (12). t The specific method is as follows: a preliminary experiment is conducted by simultaneously capturing images of the laser cladding head (6) repaired using an infrared thermal imager and a CCD camera. The distance L from the center of the laser cladding head to the 400℃ high-temperature zone is obtained through the infrared thermal imager. t ', By adjusting the aperture of the CCD camera, the distance between the outer edge of the bright circle of the CCD image and the center of the laser cladding head (6) is L. t Extract the grayscale value A and brightness value B from the outer edge of the bright circle. These are the image parameters of the 400℃ high-temperature area in the CCD camera image. During the restoration process, use a CCD camera to capture real-time restoration images and obtain the area with grayscale value A and brightness value B. The distance from the center of the laser cladding head (6) to this area is L. t .

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