Partitioned ultrasonic-assisted method based on multilayer laser cladding repair and application of partitioned ultrasonic-assisted method

Abstract

The invention belongs to the field of laser processing, and relates to a partitioned ultrasonic-assisted method based on multilayer laser cladding repair and application of the partitioned ultrasonic-assisted method. The method comprises the following steps: step 1, carrying out surface pretreatment on a to-be-repaired area; 2, a first ultrasonic head is arranged around the to-be-repaired area, a longitudinal ultrasonic energy field with first power is released, and laser cladding is conducted on the to-be-repaired area; 3, a second ultrasonic head is replaced, a second-power ultrasonic energy field is applied to the surface of the first-layer laser cladding layer, and laser is started, so that second-layer laser cladding operation is completed on the surface of the first-layer laser cladding layer; the steps are repeated until the target number of cladding repairing layers is reached; the first power is greater than the second power; and 4, after laser cladding repairing is completed, aftertreatment is conducted on the surface of the formed repairing layer. According to the method disclosed by the invention, adaptive ultrasonic energy fields are respectively applied to different interfaces, so that targeted strengthening of various interfaces is realized, and the overall performance of the multi-layer cladding structure is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of laser processing, and relates to a partition ultrasonic auxiliary method based on multi-layer laser cladding repair and application thereof. BACKGROUND

[0002] As a core consumable component of tunnel boring equipment, the shield cutter often appears surface damage and performance degradation due to complex geological environment and high-intensity wear during service. Laser cladding technology has become one of the promising processes for shield cutter remanufacturing repair, with high-energy beam, high-precision control and excellent metallurgical bonding capacity. By cladding high-performance alloy materials on the cutter surface, not only the precise repair of damaged areas can be achieved, but also the wear resistance and service life of the cutter can be effectively improved. Compared with traditional surfacing, thermal spraying and other surface repair methods, laser cladding has significant advantages such as small heat-affected zone, low dilution rate and high bonding strength, which can meet the efficient, energy-saving and green remanufacturing needs of shield cutters under complex working conditions. The popularization and application of this technology is of great significance to improve the reliability of shield equipment, reduce maintenance costs and promote the sustainable development of the engineering machinery industry.

[0003] However, the existing method of laser cladding repair of shield cutters still faces many technical bottlenecks. For example: due to the rapid melting and non-equilibrium solidification characteristics in the laser cladding process, the cladding layer is prone to defects such as uneven organization, dendritic segregation, pores and micro-cracks, which affect the compactness and mechanical properties of the repair layer. The rapid change of high temperature gradient and cooling rate limits the grain refinement mechanism, and local areas may form coarse columnar crystals or abnormal grain growth, resulting in insufficient wear resistance and performance anisotropy of the cladding layer. In addition, residual stress is concentrated during the dynamic solidification of the molten pool, which easily causes unstable interface bonding, decreased fatigue performance and weakened stress corrosion resistance.

[0004] To break through the technical difficulties of wear resistance and interface bonding stability in the process of laser cladding repair of shield cutters, domestic and foreign research teams have been continuously conducting research on field-assisted systems. Existing researches mainly focus on ultrasonic strengthening of only a single interface (such as the substrate-cladding material interface). However, in the actual process of laser cladding repair of shield cutters, the substrate-cladding material interface and the cladding material-cladding material interface have significant differences in key characteristics such as physical structure and metallurgical reaction. If only a single ultrasonic intensity and a unified action mode are used to treat all interfaces, it is difficult to meet the actual needs of different interfaces, and it is also easy to cause multiple technical defects, which restricts the improvement of repair effect. SUMMARY

[0005] The present application aims to avoid the deficiencies in the prior art and provides a partitioned ultrasonic-assisted method based on multilayer laser cladding repair, which uses high-energy ultrasonic energy field assistance for the substrate-cladding material interface to effectively promote the metallurgical bonding between the cladding material and the substrate, improve the interface density, and reduce the formation of pores and cracks. Low-energy ultrasonic energy field assistance is used for the cladding material-cladding material interface to induce cladding layer organization refinement and promote uniform grain growth. The overall cladding layer bonding strength, density, and organization uniformity are improved, and the overall performance of the multilayer cladding structure is significantly improved.

[0006] To achieve one of the above purposes, the present application provides the following technical solutions: A partitioned ultrasonic-assisted method based on multilayer laser cladding repair, comprising the following steps: Step 1: surface pretreatment of the substrate's repair area; Step 2: set the first ultrasonic head around the repair area and in direct contact with the substrate, the first ultrasonic head releases a longitudinal ultrasonic energy field with a first power, starts the laser, and performs laser cladding on the repair area to complete the first layer of laser cladding; Step 3: replace the second ultrasonic head, which is not in direct contact with the substrate; apply an ultrasonic energy field with a second power to the surface of the first layer of laser cladding, start the laser, and control the second ultrasonic head to move synchronously with the cladding head so that the second ultrasonic head and the cladding head act on the same action area on the surface of the first layer of laser cladding, thereby completing the second layer of laser cladding on the surface of the first layer of laser cladding; Repeat the next layer of laser cladding on the surface of the formed cladding layer until the target number of cladding repair layers is reached; Wherein, the first power is greater than the second power; Step 4: after completing the laser cladding repair, perform post-processing on the surface of the formed repair layer.

[0007] Further, the second ultrasonic head is a side-axis non-contact ultrasonic head.

[0008] Further, the first power is greater than or equal to 350W.

[0009] Further, the second power is less than or equal to 150W.

[0010] Further, the average power of the laser cladding is 1.8kW, the spot diameter is 2mm, the scanning speed is 12mm / s, the powder feeding rate is 10g / min, and the overlap rate is 45%.

[0011] Further, the surface pretreatment is laser polishing treatment of the worn surface using picosecond laser.

[0012] Furthermore, the post-processing involves laser milling and laser polishing of the final cladding surface.

[0013] Furthermore, the laser polishing parameters are as follows: average power 15W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 1000mm / min, and filling spacing 20μm.

[0014] Furthermore, the laser milling parameters are as follows: average power 25W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 400mm / min, and filling spacing 10μm.

[0015] To achieve the second objective mentioned above, the present invention also provides an application of the above-mentioned multi-layer laser cladding repair-based partitioned ultrasonic-assisted method in the laser cladding repair of tunnel boring machine cutters.

[0016] The beneficial effects of the partitioned ultrasound-assisted method for multilayer laser cladding repair based on the present invention are as follows: This invention applies matched ultrasonic energy fields to the substrate-cladding material interface and the cladding material-cladding material interface during multilayer laser cladding repair. Through parameter optimization and zonal control, targeted strengthening of various interfaces is achieved. Specifically, a high-intensity ultrasonic energy field acts on the interface between the substrate and the cladding material, significantly promoting element diffusion and metallurgical reactions at the interface, enhancing the bonding strength between the cladding layer and the substrate, reducing interface defects such as porosity and cracks, and improving the service safety and reliability of the repair layer. Conversely, a low-intensity ultrasonic energy field acts on the interlayer interfaces between the multilayer cladding materials, effectively refining the interlayer microstructure, improving the density and uniformity of the multilayer cladding structure, and reducing the probability of interlayer defects such as delamination and microcracks. The synergistic effect of the zonal ultrasonic energy fields not only optimizes the microstructure of the cladding layer, promoting grain refinement and orientation diversification, strengthening the grain boundary structure, and improving the mechanical and wear resistance of the cladding layer, but also makes the interlayer transition smoother, reducing stress concentration and the formation of brittle phases, resulting in a more stable overall structure. By controlling the ultrasound parameters in different zones, the performance can be synergistically optimized for different interfaces, breaking through the technical bottlenecks of traditional laser cladding repair processes in terms of interface bonding and tissue uniformity.

[0017] In the laser cladding repair process of tunnel boring machine (TBM) cutters, by applying ultrasonic energy fields of different intensities in different zones, the bonding strength, density, and uniformity of the cladding layer are significantly improved. This not only efficiently repairs damaged areas on the surface of the TBM cutter, but also achieves synergistic performance optimization for different interfaces, significantly improving the repair quality and providing a brand-new technical solution for the remanufacturing and service performance enhancement of TBM cutters. Attached Figure Description

[0018] Figure 1This is a schematic diagram of laser cladding at the interface between the shield cutter body and the cladding material in Example 3; Figure 2 This is a schematic diagram of laser cladding at the interface of the shield tunneling cutter cutting material in Example 3; Figure label: 1. Substrate; 2. Laser beam; 3. First ultrasonic head; 4. First laser cladding layer; 5. Second ultrasonic head; 6. Formed laser cladding layer; 7. Next laser cladding layer. Detailed Implementation

[0019] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0020] Example 1: A partitioned ultrasound-assisted method for multilayer laser cladding repair A partitioned ultrasound-assisted method for repair based on multilayer laser cladding includes the following steps: Step 1: Perform surface pretreatment on the area of ​​the substrate to be repaired; Step 2: Place the first ultrasonic head around the area to be repaired and make direct contact with the substrate. The first ultrasonic head releases a longitudinal ultrasonic energy field with a first power, activates the laser, and performs laser cladding on the area to be repaired to complete the first layer of laser cladding. Step 3: Replace the second ultrasonic head. The second ultrasonic head does not directly contact the substrate. Apply a second power ultrasonic energy field to the surface of the first laser cladding layer, start the laser, and control the second ultrasonic head and the cladding head to move synchronously so that the second ultrasonic head and the cladding head work together to act on the same area of ​​the surface of the first laser cladding layer, thereby completing the second laser cladding operation on the surface of the first laser cladding layer. Repeat the laser cladding process on the surface of the formed cladding layer until the target number of cladding repair layers is reached; Wherein, the first power is greater than the second power; Step 4: After completing the laser cladding repair, perform post-processing on the surface of the formed repair layer.

[0021] In multilayer laser cladding repair, current technologies often employ a single ultrasonic intensity and uniform action method to treat all interfaces. This approach ignores the inherent differences in physical structure, metallurgical reaction, and actual treatment requirements of different interfaces, easily leading to various defects. Specifically, for the substrate-cladding material interface, using high-intensity ultrasound and direct contact with the substrate can effectively enhance the flow of molten metal and element diffusion at the interface, promote metallurgical bonding, improve bonding strength and density, and reduce interface defects such as porosity and cracks. However, if the same high-intensity ultrasound and contact method are applied to the interlayer interfaces of the cladding material, it may lead to excessive disturbance of the interlayer structure, abnormal grain growth, and even new structural defects such as microcracks and delamination, affecting the overall uniformity and mechanical properties of the multilayer cladding structure. Conversely, if a uniform low-intensity ultrasonic energy field is used and applied to all interfaces in a non-contact manner, although it is beneficial for the uniform refinement of the interlayer structure, it cannot fully stimulate the metallurgical reaction at the substrate-cladding material interface, resulting in insufficient density in the bonding zone, reduced bonding strength, and affecting the service safety of the repair layer. It is evident that a single ultrasonic intensity and mode of action cannot simultaneously meet the optimization requirements of different interfaces, and it is easy for one end to improve while the other end deteriorates, thus limiting the overall effect and application value of laser cladding repair technology.

[0022] Therefore, this invention applies matched ultrasonic energy fields to the substrate-cladding material interface and the cladding material-cladding material interface during multilayer laser cladding repair. Through parameter optimization and zonal control, targeted strengthening of various interfaces is achieved. Specifically, a high-intensity ultrasonic energy field acts on the interface between the substrate and the cladding material, significantly promoting element diffusion and metallurgical reactions at the interface, enhancing the bonding strength between the cladding layer and the substrate, reducing interface defects such as porosity and cracks, and improving the service safety and reliability of the repair layer. Conversely, a low-intensity ultrasonic energy field acts on the interlayer interfaces between the multilayer cladding materials, effectively refining the interlayer structure, improving the density and uniformity of the multilayer cladding structure, and reducing the probability of interlayer defects such as delamination and microcracks. The synergistic effect of the zonal ultrasonic energy fields not only optimizes the microstructure of the cladding layer, promoting grain refinement and orientation diversification, strengthening the grain boundary structure, and improving the mechanical and wear resistance of the cladding layer, but also makes the interlayer transition smoother, reducing stress concentration and the formation of brittle phases, resulting in a more stable overall structure. By controlling the ultrasound parameters in different zones, the performance can be synergistically optimized for different interfaces, breaking through the technical bottlenecks of traditional laser cladding repair processes in terms of interface bonding and tissue uniformity.

[0023] Example 2: A partitioned ultrasound-assisted method for multilayer laser cladding repair A partitioned ultrasound-assisted method for repair based on multilayer laser cladding includes the following steps: Step 1: Perform surface pretreatment on the area of ​​the substrate to be repaired; In this embodiment, the surface pretreatment is: laser polishing of the worn surface using a picosecond laser.

[0024] In this embodiment, the laser polishing parameters are as follows: average power 15W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 1000mm / min, and filling spacing 20μm.

[0025] Using picosecond lasers to perform laser polishing on the worn surface of the substrate can effectively improve the surface quality of the worn area, significantly reduce the surface roughness of the area to be repaired, make the microstructure more flat and smooth, and reduce defects such as oxide layer and microcracks in the worn area. This creates a uniform and clean interface for the subsequent cladding repair process, thereby improving the bonding stability between the repair layer and the substrate and ensuring the repair quality.

[0026] Step 2: Place the first ultrasonic head around the area to be repaired and make direct contact with the substrate. The first ultrasonic head releases a longitudinal ultrasonic energy field with a first power, activates the laser, and performs laser cladding on the area to be repaired to complete the first layer of laser cladding. In this embodiment, the first power is greater than or equal to 350W.

[0027] In this embodiment, the average power of the laser cladding is 1.8kW, the spot diameter is 2mm, the scanning speed is 12mm / s, the powder feeding rate is 10g / min, and the overlap rate is 45%.

[0028] A first ultrasonic head is positioned around the area to be repaired on the substrate, making direct contact with the substrate and simultaneously releasing longitudinal ultrasound of the same high power. The number of the first ultrasonic heads can be adjusted according to the size of the area to be repaired. For example, if the area to be repaired is a long, narrow strip, one ultrasonic head can be positioned at each end of the area; if the area to be repaired is large, three or more ultrasonic heads can be positioned around the area to ensure the effectiveness of the ultrasonic energy field on the area to be repaired. In summary, the ultrasonic heads are placed at key points around the area to be repaired to ensure coverage. The direct contact between the ultrasonic heads and the substrate ensures the transmission of the ultrasonic energy field, avoids energy attenuation during transmission, and improves the efficiency of the ultrasonic energy field. A laser is then activated to perform laser cladding on the area to be repaired, so that the area to be repaired is simultaneously subjected to the first ultrasonic energy field and the laser, completing the first layer of laser cladding and forming a substrate-cladding material interface. Applying a high-intensity ultrasonic energy field during the first layer of laser cladding can significantly promote element diffusion and metallurgical reactions at the interface, enhance the bonding strength between the cladding layer and the substrate, reduce interface defects such as pores and cracks, and improve the service safety and reliability of the repair layer.

[0029] Step 3: Replace the second ultrasonic head. The second ultrasonic head does not directly contact the substrate. Apply a second power ultrasonic energy field to the surface of the first laser cladding layer, start the laser, and control the second ultrasonic head and the cladding head to move synchronously so that the second ultrasonic head and the cladding head work together to act on the same area of ​​the surface of the first laser cladding layer, thereby completing the second laser cladding operation on the surface of the first laser cladding layer. Repeat the laser cladding process on the surface of the formed cladding layer until the target number of cladding repair layers is reached; Wherein, the first power is greater than the second power; In this embodiment, the second ultrasonic head is a cross-axial non-contact ultrasonic head.

[0030] In this embodiment, the second power is less than or equal to 150W.

[0031] When performing the second laser cladding operation on the surface of the first laser cladding layer, a second ultrasonic head is used to apply a second power ultrasonic energy field to the surface of the first cladding layer. This second ultrasonic head is a off-axis non-contact ultrasonic head, whose advantage is that it can directly act on the target position on the workpiece surface, effectively avoiding damage to the already formed first cladding layer; at the same time, this type of ultrasonic head has precise positioning capability, and can achieve precise alignment with the laser beam during the laser cladding process. The laser is started, and the ultrasonic head and the cladding head are controlled to move synchronously so that the ultrasonic head and the cladding head work together to act on the same area on the surface of the first cladding layer, completing the second laser cladding operation and forming a cladding material interface. Similarly, when performing the third laser cladding operation on the surface of the second laser cladding layer, a second ultrasonic head is used to apply a second power ultrasonic energy field to the surface of the second cladding layer, the laser is activated, and the ultrasonic head and the cladding head are controlled to move synchronously so that the ultrasonic head and the cladding head work together to act on the same area of ​​the first cladding layer surface, completing the third laser cladding operation. This operation logic is repeated to perform the next layer of laser cladding operation on the already formed cladding layer surface until the preset target number of cladding repair layers is reached. When performing multi-layer laser cladding, the application of a low-intensity ultrasonic energy field effectively refines the interlayer structure, improves the density and uniformity of the multi-layer cladding structure, and reduces the probability of interlayer defects such as delamination and microcracks.

[0032] Step 4: After completing the laser cladding repair, perform post-processing on the surface of the formed repair layer.

[0033] In this embodiment, the post-processing is: laser milling and laser polishing of the final cladding surface.

[0034] In this embodiment, the laser polishing parameters are as follows: average power 15W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 1000mm / min, and filling spacing 20μm.

[0035] In this embodiment, the laser milling parameters are as follows: average power 25W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 400mm / min, and filling spacing 10μm.

[0036] During the cladding process, unevenness can easily occur on the surface of the cladding layer due to issues such as powder adhesion and unevenness at nodes. Laser milling can remove surface burrs and unevenness at nodes, while laser polishing can further improve the smoothness and flatness of the cladding layer surface, eliminate residual burrs, oxide layers and other impurities, and ensure that the surface roughness meets the requirements of precision machining. The synergistic effect of both processes can improve the surface accuracy and quality of the cladding layer.

[0037] Example 3: Application of a zoned ultrasonic-assisted method based on multi-layer laser cladding repair in laser cladding repair of tunnel boring machine cutters. Laser cladding repair of the worn surface of the H13 tunnel boring machine cutter head includes the following steps: Step 1: Use a picosecond laser to perform laser polishing on the worn surface of the tunnel boring machine cutter head to improve the surface quality of the worn area of ​​substrate 1. The laser polishing parameters are: average power 15W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 1000mm / min, and fill spacing 20μm.

[0038] Step 2: As Figure 1 As shown, four first ultrasonic heads 3 are distributed around the pre-defined area to be repaired and contact the shield cutterhead base 1, simultaneously releasing longitudinal ultrasonic waves with a power of 350 W. The laser is then activated, and the laser beam 2 acts on the area to be repaired to perform laser cladding, forming the first laser cladding layer 4. The laser cladding parameters are: average power 1.8 kW, spot diameter 2 mm, scanning speed 12 mm / s, powder feeding rate 10 g / min, and overlap rate 45%.

[0039] Step 3: As Figure 2 As shown, the second ultrasonic head 5 is replaced. The second ultrasonic head 5 is a 150W off-axis non-contact ultrasonic head. The laser is activated, and the laser beam 2 acts on the surface of the first laser cladding layer 4 to perform the second laser cladding operation. During the cladding process, the second ultrasonic head and the cladding head are controlled to move synchronously so that the second ultrasonic head and the cladding head work together on the same target area on the surface of the formed cladding layer 6. The laser cladding parameters are: average power 1.8kW, spot diameter 2mm, scanning speed 12mm / s, powder feeding rate 10g / min, and overlap rate 45%. The next laser cladding operation is repeated on the surface of the formed laser cladding layer 6 to form the next laser cladding layer 7, until the target number of cladding repair layers is reached.

[0040] Step 4: Perform laser milling and laser polishing on the final cladding surface to optimize the cladding quality. The laser milling parameters are as follows: average power 25W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 400mm / min, and fill spacing 10μm; the laser polishing parameters are as follows: average power 15W, repetition frequency 100kHz, spot diameter 20-40μm, scanning speed 1000mm / min, and fill spacing 20μm.

[0041] In the laser cladding repair of tunnel boring machine (TBM) cutters, there are significant differences in physical structure and metallurgical reaction between the substrate-cladding material interface and the cladding material-cladding material interface. Treating all interfaces with a single ultrasonic intensity and uniform application method often fails to meet the actual needs of each interface, easily leading to various technical defects. This invention significantly improves the bonding strength, density, and uniformity of the cladding layer by applying ultrasonic energy fields of varying intensities in different zones. It not only efficiently repairs damaged areas on the surface of the TBM cutter but also achieves synergistic performance optimization for different interfaces, significantly improving repair quality and providing a novel technical solution for the remanufacturing and enhanced service performance of TBM cutters.

[0042] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method of partitioned ultrasonic-assisted repair based on multi-layer laser cladding repair, characterized in that, The method comprises the following steps: Step 1: surface pretreatment is performed on the region to be repaired of the base body; Step 2: a first ultrasonic head is arranged around the region to be repaired and in direct contact with the base body, the first ultrasonic head releases a longitudinal ultrasonic energy field of a first power, a laser is started, laser cladding is performed on the region to be repaired, and a first layer of laser cladding is completed; Step 3: a second ultrasonic head is replaced, the second ultrasonic head is not in direct contact with the base body, an ultrasonic energy field of a second power is applied to the surface of the first layer of laser cladding, a laser is started, the second ultrasonic head is controlled to move synchronously with the cladding head so that the second ultrasonic head and the cladding head act on the same action region of the surface of the first layer of laser cladding, thereby completing a second layer of laser cladding on the surface of the first layer of laser cladding; The next layer of laser cladding is repeatedly performed on the surface of the formed cladding layer until the target number of cladding repair layers is reached; The first power is greater than the second power. Step 4: after the laser cladding repair is completed, post-treatment is performed on the surface of the formed repair layer.

2. The method of claim 1, wherein the method is a multi-layer laser cladding repair based partitioning ultrasonic-assisted method. The second ultrasonic head is a side-shaft non-contact ultrasonic head.

3. The method of claim 1, wherein, The first power is greater than or equal to 350 W.

4. The method of claim 1, wherein, The second power is less than or equal to 150 W.

5. The method of claim 1, wherein, The average power of the laser cladding is 1.8 kW, the spot diameter is 2 mm, the scanning speed is 12 mm / s, the powder feeding rate is 10 g / min, and the overlap rate is 45%.

6. The method of claim 1, wherein, The surface pretreatment is laser polishing treatment of the worn surface using a picosecond laser.

7. The method of claim 1, wherein the method is a multi-layer laser cladding repair based partitioning ultrasonic-assisted method. The post-treatment is laser milling and laser polishing treatment of the final cladding surface.

8. A method according to claim 6 or 7, wherein the method is a zoned ultrasonic assisted method based on multi-layer laser cladding repair. The laser polishing parameters are as follows: average power 15 W, repetition frequency 100 kHz, spot diameter 20-40 μm, scanning speed 1000 mm / min, and filling pitch 20 μm.

9. The method of claim 7, wherein the method is a multi-layer laser cladding laser repair based zonal ultrasonic assisted method. The laser milling parameters are as follows: average power 25 W, repetition frequency 100 kHz, spot diameter 20-40 μm, scanning speed 400 mm / min, and filling pitch 10 μm.

10. The application of the partition ultrasonic auxiliary method based on multi-layer laser cladding repair according to any one of claims 1-9 to laser cladding repair of a shield cutter.

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