Laser cladding repair process for R angle of steam turbine rotor

Abstract

The invention belongs to the technical field of laser remanufacturing and high-end equipment repairing, and particularly discloses a steam turbine rotor R angle laser cladding repairing process which is used for conducting segmented multi-layer laser cladding on a steam turbine rotor R angle to ensure that the laser cladding thickness reaches the steam turbine rotor R angle repairing thickness and has machining allowance. The thickness of each layer of laser cladding is 0.7 mm-0. 9 mm, and ultrasonic impact stress relief treatment is carried out after each section of laser cladding is completed. And PT nondestructive flaw detection, phased array ultrasonic detection, hardness detection and residual stress detection are fused to ensure the repair quality. The rotor is suitable for 530 DEG C high-temperature and high-pressure working conditions, the cost is greatly reduced compared with rotor replacement, and the rotor has remarkable industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of laser remanufacturing and high-end equipment repair, and in particular to a process for laser cladding repair of the R corner of a steam turbine rotor. Background Art

[0002] The combination of all rotating parts in a steam turbine is called a rotor, which is one of the most important components of a steam turbine.

[0003] The rotor consists of a shaft, impeller or drum, moving blades, balancing piston, emergency safety device, turning gear, and coupling. During daily use, the rounded corners (R-corners) behind the first-stage disc of the high-pressure shaft seal can wear or crack. These R-corner wear and cracks can seriously affect the performance of the turbine rotor. To ensure rotor performance, severe R-corner wear often requires replacement, significantly increasing the cost of turbine operation. R-corner cracks can be addressed by turning and reducing the rotor, but this reduces operating efficiency and increases the risk of shaft breakage. Furthermore, after turning and reducing the rotor to a certain size, it must be replaced for operational safety, significantly increasing the cost of turbine operation.

[0004] Realizing green remanufacturing through laser repair of the R corner of a turbine rotor can, on the one hand, effectively extend the life cycle of the turbine rotor, and on the other hand, greatly reduce the operating cost of the turbine, effectively save resources and reduce solid waste pollution. It has important economic and environmental benefits and is of great significance. Therefore, it is imperative to repair the wear and cracks of the R corner of the turbine.

[0005] Laser cladding remanufacturing technology is an advanced repair technology developed based on the concept of laser rapid prototyping and remanufacturing. This technology uses high-energy beam laser and motion control system as heat source and path drive respectively to perform local high-quality repair on damaged parts caused by wear, corrosion and cracks due to various reasons. This technology not only has high bonding strength, but also has the advantages of small deformation of the base material and controllable heat-affected zone. It shows great application potential in the repair of failed parts with high requirements.

[0006] The following problems exist when applying laser cladding remanufacturing technology to repair the R corner of a steam turbine rotor:

[0007] Process limitations: Laser cladding technology is difficult to balance interlayer bonding strength and residual stress control in deep R corner repair, resulting in cracks and pores in the cladding layer;

[0008] Stress accumulation risk: The existing process relies on overall stress relief in the later stage. As the thickness of the cladding layer increases, the residual stress increases significantly, which can easily cause deformation or cracking;

[0009] Detection lag: Conventional nondestructive testing, such as PT nondestructive testing (penetrant testing), is mostly used for final inspection and cannot provide real-time feedback on quality risks during the repair process.

[0010] Manually operating the laser cladding device for laser cladding has low cladding efficiency and high labor intensity. Summary of the Invention

[0011] In order to solve the above-mentioned problems existing in the application of laser cladding technology to the repair of the R corner of a turbine rotor, the present invention provides a laser cladding repair process for the R corner of a turbine rotor. This repair process can effectively avoid the occurrence of cracks and pores in the cladding layer, and can also avoid deformation or cracking of the cladding layer when the thickness of the cladding layer increases. It can also replace manual laser cladding, greatly improving the efficiency of laser cladding.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0013] A steam turbine rotor R corner laser cladding repair process, characterized by comprising the following steps:

[0014] Steam turbine rotor R angle detection steps: detect the steam turbine rotor R angle to obtain the wear depth and crack depth of the steam turbine R angle;

[0015] Machining steps: Determine the depth of machining based on the crack depth detected at the R corner of the turbine rotor, and remove the fatigue layer and cracks at the R corner of the turbine rotor by machining. After machining, the surface roughness of the R corner of the turbine rotor is Ra ≤ 3.2 μm.

[0016] Determine the laser cladding scheme: Perform segmented multi-layer laser cladding on the R corner of the turbine rotor, and determine the laser cladding scheme based on the calculated laser cladding repair thickness. The laser cladding scheme includes the number of laser cladding layers and the thickness of each laser cladding layer.

[0017] Laser cladding and stress control steps: laser cladding is performed using a laser cladding device according to a laser cladding plan. The laser cladding device includes a laser cladding nozzle, a laser, a machine base, a wheel fixing device and a frame. The wheel fixing device is fixed on the wheel of the turbine rotor. The frame is installed on the wheel fixing device. The frame can rotate circumferentially on the wheel fixing device. The machine base is connected to the frame. The machine base can slide left and right and move up and down on the frame. The laser cladding nozzle and laser are installed on the machine base.

[0018] The thickness of laser cladding is 0.7mm-0.9mm.

[0019] When performing multi-layer segmented laser cladding on the R corner of the turbine, the laser power is 2500-3000W, the linear speed is 800-1000mm / min, the powder feed rate is 28-31.5g / min, the segment arc length is 250-300mm, and the cladding is symmetrical at 180 degrees to prevent deformation.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention first detects the wear and crack depth of the R angle of the turbine rotor, and then determines the repair thickness based on the detected wear and crack depth. During the repair, multi-layer laser cladding is used, and the thickness of each layer is controlled between 0.7-0.9mm. A laser cladding device is used instead of manual automatic laser cladding, and ultrasonic stress relief is performed during cladding, which greatly improves the efficiency of laser cladding. This can also effectively reduce the residual stress of the cladding layer and improve the interlayer bonding strength, avoiding the occurrence of cracks and pores in the cladding layer. The existing process directly clads to the required thickness and relies entirely on the subsequent overall stress relief. As the thickness of the cladding layer increases, the residual stress increases significantly, which can easily cause deformation or cracking. The present invention, on the other hand, uses multi-layer laser cladding, and the thickness of each layer is controlled between 0.7-0.9mm. Ultrasonic impact treatment is also performed after each cladding layer. Through multiple stress reductions, the residual stress is greatly reduced, and it no longer relies on the subsequent overall stress relief. It can significantly reduce stress without causing deformation or cracking, thus ensuring the quality of laser cladding. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a process flow chart of the present invention;

[0022] Figure 2 This is a schematic structural diagram of the laser cladding device of the present invention without the wheel disc fixing device;

[0023] Figure 3 This is a schematic diagram of the arc frame structure of the laser cladding device of the present invention;

[0024] Figure 4 Schematic diagram of the arc track structure of the laser cladding device of the present invention;

[0025] Figure 5 A schematic structural diagram of the disc fixing device of the laser cladding device of the present invention after being installed on the turbine rotor disc.

[0026] The reference numerals in the figure are 1, machine base, 2, laser cladding nozzle, 3, laser, 4, ultrasonic impact equipment, 5, frame, 6, wheel, 7, arc track, 8, bolt hole, 9, arc rack, 10, T-shaped limiter, 11, arc frame, 110, circular groove, 111, opening, 12, mounting plate, 13, connecting block, 14, guide column, 15, guide sleeve, 16, connecting seat, 17, transmission shaft, 18, transmission gear, 19, bolt, 20, gear, 21, telescopic member. DETAILED DESCRIPTION

[0027] The rear R-angle of the first-stage impeller of the high-pressure shaft seal of a steam turbine rotor will wear and crack during daily use. To ensure the working performance of the rotor, in actual applications, the rotor is replaced to solve the problem of R-angle wear, and the R-angle crack is solved by turning and reducing the diameter. This treatment method has the problem of significantly increasing the cost of using the steam turbine or reducing the working efficiency after the rotor is turned and reduced, and there is also the risk of shaft breakage after the diameter reduction. Laser cladding remanufacturing technology is an advanced repair technology developed based on the concepts of laser rapid prototyping and remanufacturing. This technology uses high-energy beam lasers and motion control systems as heat sources and path drives respectively. It performs local high-quality repairs on damaged parts caused by wear, corrosion, cracks, etc. due to various reasons. This technology not only combines high strength, but also has the advantages of small deformation of the base material and controllable heat-affected zone. It shows great application potential in repairing failed parts with high requirements.

[0028] In order to avoid the high cost of replacing the turbine rotor, the inventors came up with the idea of applying laser cladding remanufacturing technology to the laser repair of the R corner of the turbine rotor. When applying laser cladding remanufacturing technology to the laser repair of the R corner of the turbine rotor, the inventors found the following problems:

[0029] The existing laser cladding reconstruction process is difficult to control the bonding strength and residual stress of the laser cladding layer of the turbine rotor, resulting in cracks and pores in the laser cladding layer; it cannot meet the use requirements of the rotor.

[0030] The existing laser cladding reconstruction process relies on the overall stress relief in the later stage. When the thickness of the laser cladding layer increases, the residual stress increases significantly, which can easily cause deformation or cracking.

[0031] There is also a lag in detection: conventional non-destructive testing is mostly used for final inspection, and it cannot provide real-time feedback on quality risks during the repair process, nor can it control repair risks in real time, resulting in the failure to meet usage requirements after repair.

[0032] Therefore, in response to the above-mentioned problems existing in the application of laser cladding regeneration technology in the repair of the R corner of a turbine rotor, the present invention provides a process for repairing the wear and cracks of the R corner of a turbine rotor. This repair process no longer uses traditional laser cladding technology, but improves laser cladding into multiple repairs in layers and segments, and uses ultrasonic impact to remove residual stress, reduce residual stress, improve the bonding force between the repair layers, and avoid the occurrence of cracks and pores. Since it is multiple cladding and multiple stress removal, rather than the overall stress elimination of the existing technology, it can be ensured that the residual stress will not increase significantly when the thickness of the cladding layer increases, and will not cause deformation or cracking of the cladding layer. At the same time, routine inspections are carried out before and after each processing step, such as PT non-destructive testing, residual stress testing, hardness testing, vibration testing and phased array ultrasonic testing, multiple inspections, and inspections at each link to ensure the cladding quality of each link, and ultimately ensure the quality of the entire cladding, control the quality risks in the repair process in real time, ensure the effectiveness of the repair, and ultimately ensure that the repair quality meets the use requirements of the rotor.

[0033] The following describes the details in conjunction with specific embodiments and drawings.

[0034] Example 1

[0035] Repair of R angle of steam turbine rotor in a power plant:

[0036] like Figure 1 As shown in the figure, the turbine rotor is subject to factory inspection after entering the factory. The factory inspection mainly checks the following contents:

[0037] The hardness and wear size of the R corner of the turbine rotor were tested. After testing, the wear depth of the R corner of the turbine rotor was 5mm, and the hardness of the R corner was: HB235-275.

[0038] The R-corner of the turbine rotor is inspected for cracks using PT nondestructive testing (NDT), phased array ultrasonic testing (PAUT), or both. The PT NDT method involves dye penetrant testing of the surfaces of all R-corner components. Both the penetrant and developer are sprayed for at least 10 minutes. DPT-5 is used for cleaning, penetrant development, and development. The testing standard used is NB / T47013-2015. The R-corner crack depth was found to be 6 mm.

[0039] The residual stress test of the R angle of the steam turbine rotor is carried out, and the specific test results are shown in the following table:

[0040]

[0041] It can be seen from the above table that when the wear depth of the R corner of the turbine rotor is 5mm, its maximum residual tensile stress is 246.22MPa.

[0042] The R corner of the steam turbine rotor was inspected at the factory and the wear depth of the R corner was 5mm and the crack depth was 6mm.

[0043] In order to eliminate the cracks, the thickness of the cracks that need to be removed by mechanical processing needs to be greater than or equal to 6mm to achieve the purpose of completely removing the cracks.

[0044] A fatigue layer removal depth of 2mm is sufficient for the R-corner of a steam turbine rotor. Therefore, machining (preferably turning) of 6mm can remove both the fatigue layer and cracks. This effectively removes both the fatigue layer and cracks. After machining, the surface roughness of the R-corner of the steam turbine rotor should be Ra ≤ 3.2μm. After machining to remove the fatigue layer and cracks, PT nondestructive testing (NDT) is performed to detect any remaining cracks. If cracks are present, further machining is performed until the R-corner is crack-free. Hardness testing is then performed after machining to remove the fatigue layer and cracks.

[0045] Since the wear depth of the R corner of the turbine rotor is 5 mm and the machining depth is 6 mm, the R corner depth is 11 mm at this time. Therefore, the depth of the laser cladding repair of the R corner of the turbine rotor is 11 mm.

[0046] Build the laser cladding operation platform, start laser cladding and stress control, and perform segmented multi-layer cladding repair on the R corner of the turbine. When performing segmented multi-layer cladding repair, the thickness of each layer of cladding is controlled between 0.7mm and 0.9mm. The thickness of each repair layer can be the same or different. The thickness of the upper layer can be greater than the thickness of the next layer or less than the thickness of the next layer. There is no restriction here. In this embodiment, the thickness of each cladding repair layer is selected to be 0.8mm, and the thickness of each cladding repair layer is the same. A total of sixteen layers are clad, so that the cladding thickness reaches 12.8mm. When repairing each layer of laser cladding, the laser power is 2500W, the line speed is 800, and the powder feeding amount is g / min.

[0047] The cladding material is nickel-based powder alloy powder, which includes Cr: 22%, Mo: 9%, Nb: 3.5%, Fe: 3%, Ti: 0.3%, and the balance is Ni, calculated by weight percentage.

[0048] The specific steps for segmented multi-layer cladding repair are as follows: During the first laser cladding layer, segmented cladding is performed with arc lengths ranging from 250-300 mm, and symmetrical cladding is performed at 180° angles. After each laser cladding stage, the cladding layer is mechanically polished to remove surface slag. This polishing not only improves the bond strength between the cladding layers but also reduces residual stress. After polishing, the cladding layer is ultrasonically impacted using a spherical impactor with a 4 mm diameter, an impact velocity of 200 mm / s, and an impact intensity of 0.15-0.25 mmA. Ultrasonic impact and mechanical polishing can reduce residual stress in the laser cladding layer. During laser cladding, the wheel runout is monitored in real time using a dial indicator, with a requirement of ≤0.02 mm. After ultrasonic impact treatment, PT nondestructive testing is performed to check for cracks in the cladding layer. If cracks are found, they are polished away and re-cladding is performed. After one laser cladding layer is completed, the next section is applied. This section also requires mechanical polishing and ultrasonic impact treatment. Each section is processed in this order, following the laser cladding, polishing, and ultrasonic impact treatment steps until the first layer of laser cladding is complete. The first laser cladding layer is then subjected to PT nondestructive testing to ensure it is crack-free. If cracks are present, they are mechanically removed until they are completely crack-free. After PT testing, the first laser cladding layer undergoes ultrasonic impact treatment to further eliminate residual stress. Layers 2 through 16 are processed in the same manner as the first layer.

[0049] In this embodiment, repairing the R-angle of a steam turbine rotor begins by inspecting the R-angle in question, confirming the repair workload, and developing a laser cladding process plan. Fatigue layers and cracks are then removed. Removing the fatigue layer also prevents it from affecting the strength of the laser repair. Using segmented, multi-layer laser cladding repair, instead of directly laser cladding to the repair thickness, ultrasonic impact stress relief is applied to the cladding layer after each laser cladding segment. Furthermore, each laser cladding layer undergoes PT nondestructive testing (or phased array ultrasonic testing) and ultrasonic stress relief. This ensures that each laser cladding layer has low residual stress and is crack-free. When multiple laser cladding layers are clad together, the entire laser cladding layer maintains low residual stress and crack-free performance. This ensures high inter-layer bonding strength and low residual stress throughout the entire laser cladding layer, effectively controlling the residual stress of the laser cladding layer. PT nondestructive testing, hardness testing, residual stress relief, runout testing, and phased array ultrasonic testing were performed at multiple points. This multi-step process ensures the quality of each cladding step, ultimately guaranteeing the overall quality of the cladding and allowing for real-time control of quality risks during the repair process. Furthermore, the laser cladding material, made of nickel-based alloy powder, produces a superior cladding layer with enhanced bonding strength.

[0050] After laser cladding and stress control of the turbine rotor's R-corner, the cladding layer undergoes rough machining (using turning). The purpose of rough machining is to reduce residual stress and ensure sufficient machining allowance for residual stress testing (stress testing requires drilling 0.5-0.8mm deep). The surface roughness after rough machining is Ra ≤ 3.2μm. In this example, the required laser cladding thickness is 11mm, while the actual laser cladding thickness is 12.8mm. The extra dimension is to ensure sufficient R-corner thickness for rough machining and residual stress testing, and to ensure sufficient machining allowance for crack removal during segmented, multi-layer laser cladding.

[0051] After rough machining is completed, the cladding layer is subjected to PT non-destructive testing, phased array ultrasonic testing, or a combination of the two to detect whether there are defects such as cracks. After testing, no cracks are generated in the cladding layer. If there are cracks, they are eliminated by mechanical processing to ensure that there are no cracks.

[0052] After the rough machining is completed, the residual stress of the cladding layer is tested. The stress value should be less than the stress value when entering the factory to be qualified. The test results are shown in the following table:

[0053]

[0054] It can be seen from the above table that after rough processing, the maximum residual tensile stress is 148.71MPa. The stress value at this time is less than the residual tensile stress value of 246.22MPa when entering the factory, which is qualified.

[0055] After rough machining, the cladding layer on the R-corner of the turbine rotor was fine-machined (using turning) to restore the required R-corner dimensions. After fine machining, the surface roughness of the cladding layer reached Ra ≤ 1.6 μm. The cladding layer was then subjected to PT nondestructive testing (PT) (specific testing methods: dye penetrant testing of the surfaces of all R-corner components of the turbine rotor was performed. The penetrant and developer were both applied by spraying, with penetration and development times exceeding 10 minutes. DPT-5 was used for cleaning, penetrant testing, and development, according to the NB / T47013-2015 standard). Phased array ultrasonic testing, hardness testing, runout re-inspection, and residual stress testing were also performed. PT and phased array ultrasonic testing revealed no cracks, pores, deformation, or cracking in the R-corner cladding layer. After laser cladding and fine machining, the R-corner of the turbine rotor was restored to its original shape. After repair, the hardness reached HB242-267, matching the substrate, with a residual stress of 148.71 MPa and a high-speed dynamic balancing accuracy of G1.0. Phased array ultrasonic testing and PT nondestructive testing confirmed the absence of cracks and slag inclusions, with a 100% pass rate. The runout value was ≤ 0.01 mm, and the material passed high-temperature and high-pressure testing at 530°C and 8.0 MPa.

[0056] Example 2

[0057] Repair of R angle of steam turbine rotor of a power generation company:

[0058] The turbine rotor's R-corner was inspected for hardness, cracks (phased array ultrasonic testing, PT nondestructive testing), residual stress, and wear. The R-corner hardness before repair was HB235-275, the maximum residual tensile stress was 250.25 MPa, the R-corner wear depth was 4 mm, and the R-corner crack depth was 5 mm. The fatigue layer is typically about 2 mm thick, so turning 5 mm removes both the fatigue layer and the cracks.

[0059] The total depth of the turbine rotor R-corner after turning the fatigue layer and cracks is 4mm + 5mm = 9mm, so the required laser cladding thickness is 9mm. In this embodiment, the thickness of each cladding repair layer is selected to be 0.8mm, and each cladding repair layer has the same thickness. A total of 14 layers are clad, resulting in a cladding thickness of 11.2mm. The total depth after machining is 9mm, and the surface roughness of the turbine rotor R-corner is Ra ≤ 3.2μm. After machining to remove the fatigue layer, PT non-destructive testing is performed to detect whether the turbine rotor R-corner has cracks to ensure that the R-corner is crack-free.

[0060] A laser cladding operation platform was built, and laser cladding and stress control were started. In this embodiment, the thickness of the laser cladding was required to be 9 mm. During each layer of laser cladding, the laser power was 2800 W, the linear speed was 900 mm / min, and the powder feeding rate was 29 g / min.

[0061] The cladding material is nickel-based powder alloy powder, including Cr: 20%, Mo: 10.5%, Nb: 2%, Fe: 3.5%, Ti: 0.35%, and the balance is Ni.

[0062] This example also uses segmented, multi-layer cladding, with segment arc lengths ranging from 250mm to 300m, and symmetrical 180° cladding. Each layer is 0.8mm thick, for a total of 11.2mm. During laser cladding, the wheel runout is monitored in real time using a dial indicator, with a requirement of ≤0.02mm. After ultrasonic impact treatment, PT nondestructive testing is performed to check the cladding layer for cracks. Any cracks are removed by grinding and then re-cladding is performed.

[0063] After laser cladding and stress control of the turbine rotor's R-angle, the cladding layer undergoes rough machining (using turning). The purpose of rough machining is to reduce residual stress and restore the turbine rotor's R-angle dimensions, and to ensure a surface roughness Ra ≤ 3.2μm. After rough machining, the cladding layer undergoes PT nondestructive testing and phased array ultrasonic testing to detect cracks and other defects. The cladding layer is found to be free of cracks.

[0064] After rough machining, the cladding layer on the turbine rotor's R-corner was fine-machined. The surface roughness of the cladding layer was Ra ≤ 1.6 μm. PT non-destructive testing, phased array ultrasonic testing, hardness testing, runout re-inspection, and residual stress testing were performed on the cladding layer. PT and phased array ultrasonic testing revealed no cracks, pores, or deformation in the R-corner cladding layer. After laser cladding and fine machining, the R-corner of the turbine rotor was restored to its required dimensions. The repaired hardness matched that of the substrate, and the residual stress was 151 MPa, less than the 250.25 MPa before repair, confirming compliance. High-speed dynamic balancing achieved G1.0 accuracy. Phased array ultrasonic testing and PT non-destructive testing confirmed the absence of cracks and slag inclusions, achieving a 100% pass rate. Runout was ≤ 0.01 mm, and the cladding passed high-temperature and high-pressure testing at 530°C / 8.0 MPa.

[0065] Example 3

[0066] Repair of R angle of steam turbine rotor in a power plant:

[0067] After the steam turbine rotor enters the factory, it undergoes factory inspection. The factory inspection mainly checks the following contents:

[0068] The hardness and wear size tests were carried out on the R corner of the turbine rotor. After testing, it was found that the R corner of the turbine rotor was severely worn, with a wear depth of 17mm and a R corner hardness of HB235-275.

[0069] The R-corner of the turbine rotor was subjected to nondestructive testing (PT) testing. The specific testing method was as follows: Each component of the R-corner of the turbine rotor was subjected to dye penetrant testing. The penetrant and developer were both applied by spraying, with penetration and development times exceeding 10 minutes. DPT-5 was used as the cleaning agent, penetrant, and developer, and the testing standard used was NB / T47013-2015. No cracks were found during testing.

[0070] According to the residual stress test, when the wear depth of the R corner is 17 mm, the maximum residual tensile stress is 278.36 MPa.

[0071] After factory inspection, the turbine rotor's R-angle is machined to remove the fatigue layer. The thickness of the removed fatigue layer is 2 mm, and the R-angle depth is 19 mm. This fatigue layer removal is necessary to prevent cracks from forming in the fatigue layer after laser cladding, which could affect the quality of the R-angle repair. After machining, the surface roughness of the turbine rotor's R-angle is Ra ≤ 3.2 μm. After machining to remove the fatigue layer, PT nondestructive testing (NDT) is performed to detect cracks in the turbine rotor's R-angle to ensure they are crack-free. If cracks are present, they are machined to remove them until they are completely eliminated.

[0072] The work platform was set up, and laser cladding and stress control began. Since the R-corner depth was 19mm, a complete repair would result in excessive residual tensile stress, failing to meet the requirement of a residual tensile stress less than that before repair. Therefore, the repair thickness was calculated as 19 × (0.6-0.8) the groove depth, with a factor of 0.7 applied, resulting in a value of 13.3mm. Laser cladding of 13.3mm increased strength by 70%. Considering the rotor's safety and repair quality, a 13.3mm R-corner repair thickness was found to be appropriate. The repaired corner would meet operational requirements, and the residual tensile stress would be less than that before repair.

[0073] Based on the calculated repair thickness, the turbine R corner was laser clad and stress-controlled. To achieve a better repair effect, TIG welding (tungsten inert gas welding, commonly known as non-metallic arc welding) was first used to repair the bottom layer to a thickness of 2 mm. The remaining layers were then repaired using segmented, multi-layer cladding. The specific steps for the segmented, multi-layer cladding repair can be followed in real time according to Example 1 and will not be repeated in this example.

[0074] In this embodiment, a total of 15 layers are repaired, the first layer is 0.7 mm, the second layer is 0.8 mm, the third layer is 0.9 mm, the fourth to tenth layers are all 0.8 mm, and the eleventh to fifteenth layers are 0.9 mm, so that the cladding thickness reaches 2 mm + 12.5 mm = 14.5 mm.

[0075] In this embodiment, the laser cladding has a laser power of 3000 W, a linear speed of 1000 mm / min, and a powder feeding rate of 31.5 g / min.

[0076] The cladding material is nickel-based powder alloy powder, including Cr: 24%, Mo: 7%, Nb: 4.5%, Fe: 2.5%, Ti: 0.2%, and the balance is Ni.

[0077] This example also uses segmented, multi-layer cladding, with segment arc lengths ranging from 250mm to 300mm. Cladding is performed symmetrically at 180° to prevent deformation. During laser cladding, the wheel runout is monitored in real time using a dial indicator, with a requirement of ≤0.02mm. After ultrasonic impact treatment, PT nondestructive testing is performed to check the cladding layer for cracks. Any cracks are removed by grinding and then re-cladding is performed.

[0078] After laser cladding and stress control of the turbine rotor R corner, the cladding layer was rough-machined to a surface roughness of Ra ≤ 3.2 μm. After rough machining, the cladding layer was subjected to PT nondestructive testing and phased array ultrasonic testing to detect cracks and other defects. The testing confirmed no cracks in the cladding layer.

[0079] After rough machining, the cladding layer on the R-corner of the turbine rotor was fine-machined. The surface roughness of the cladding layer was Ra ≤ 1.6μm. PT non-destructive testing, phased array ultrasonic testing, hardness testing, runout re-testing, and residual stress testing were performed on the cladding layer. PT and phased array ultrasonic testing revealed no cracks, pores, or deformation in the R-corner cladding layer. After laser cladding and fine machining, the R-corner of the turbine rotor was restored to the drawing dimensions. The post-repair hardness was HB242-267, matching the substrate. The residual stress was 178 MPa, less than the 278.36 MPa before repair, confirming compliance. High-speed dynamic balancing achieved G1.0 accuracy. Phased array ultrasonic testing and PT non-destructive testing confirmed the absence of cracks and slag inclusions, achieving a 100% pass rate. Runout was ≤ 0.01mm, and the cladding passed high-temperature and high-pressure testing at 530°C / 8.0 MPa.

[0080] Example 4

[0081] This embodiment is based on the above embodiment and uses a laser cladding device for automatic laser cladding, which greatly improves the laser cladding efficiency. The difference between this embodiment and the above embodiment is that a laser cladding device is used instead of a manual handheld laser cladding machine for laser cladding. The specific structure of the laser cladding device provided in this embodiment is as follows:

[0082] like Figure 2 As shown, the laser cladding apparatus of this embodiment includes a machine base 1, on which are mounted a laser cladding nozzle 2, a laser 3, and an ultrasonic impact device 4. The laser 3 and ultrasonic impact device 4 are mounted on the machine base 1. The laser cladding nozzle 2 is connected to the laser 3, and the ultrasonic impact device 4 is located in front of the laser cladding nozzle. Laser light emitted by the laser 3 is ejected from the laser cladding nozzle 2 and contacts the laser cladding material to form a laser cladding layer. The ultrasonic impact device 4 is located in front of the laser cladding nozzle. During laser cladding welding, the laser cladding nozzle performs laser cladding along the R angle of the turbine. After the laser cladding layer is formed, the ultrasonic impact device moves along the trajectory of the laser cladding nozzle, ultrasonically impacting the formed laser cladding layer. This ultrasonic stress relief operation is performed simultaneously with laser cladding, thereby reducing stress in real time. After a section of laser cladding is completed, the laser cladding device 3 is turned off and continues to move until all sections of the laser cladding layer have been ultrasonically treated. This simultaneous laser cladding and ultrasonic stress relief operation reduces residual stress in real time. In this embodiment, since the laser cladding material contains titanium, which is an active substance, contact with air should be avoided as much as possible during laser cladding, so inert gas is used for protected laser cladding. Of course, the end of the laser cladding nozzle 2 can also be set to an arc shape to match the arc surface of the turbine rotor. In this way, during laser cladding, it is in close contact with the arc surface of the turbine rotor, reducing contact with air and avoiding affecting the welding quality.

[0083] In order to further improve the efficiency of laser cladding, a laser cladding device is used for automatic laser cladding. The operator only needs to input the thickness, number of layers and arc length of each section of each layer, and the laser cladding device can automatically control and clad according to the set parameters. In order to achieve the above effect, the laser cladding device also includes the following structure:

[0084] The wheel disc fixing device is used to install the frame 5 on the wheel disc 6 of the turbine rotor. Figure 4 and Figure 5As shown, the wheel disc fixing device includes multiple curved tracks 7, preferably eight, with four on each side. Four curved tracks 7 are fixed to the left side of the wheel disc 6, and four curved tracks 7 are fixed to the right side of the wheel disc 6. Bolt holes 8 are provided at the bottom of the curved tracks 7. Bolts 19 and bolt holes 8 are used to first fix the curved tracks 7 to the wheel disc. Then, bolts 19 are tightened to firmly secure the curved tracks 7 to the wheel disc 6. An arcuate rack 9 is provided within the inner groove of the curved tracks 7. A T-shaped stopper 10 is provided on one side of the curved tracks 7, extending along the curved tracks 7.

[0085] The rack 5 is used to install the laser cladding nozzle 2, the laser 3, and the ultrasonic impact device 4. Figure 2 and Figure 3 As shown, the frame 5 specifically comprises two curved frames 11, one mounted on the left side of the wheel disc 6 and the other on the right side. The curvature of the curved frames 11 matches the curved track 7. Each curved frame 11 is provided with a circular groove 110, each with an opening 111. The circular groove 110 mates with a T-shaped stopper 10. The stopper 10 and the circular groove 110 cooperate to hold the frame in position on the curved track 7. A mounting plate 12 is welded to the tops of the two curved frames. The lower sides of the mounting plate are connected to two guide posts 14 via two connecting blocks 13. Guide sleeves 15 are mounted on the guide posts 14. These sleeves can slide left and right on the guide posts 14 under the action of a pneumatic cylinder or electric push rod. A transmission shaft 17 is also mounted on the mounting plate via a connecting seat 16. The transmission shaft 17 is mounted on the connecting seat via a bearing. A transmission gear 18 is sleeved on the transmission shaft 17, which is connected to the drive motor. A gear 20 is sleeved on each end of the transmission shaft 17, and the gear 20 meshes with the arc-shaped rack 9 of the arc-shaped track 7. The drive motor drives the transmission gear 18, which drives the transmission shaft 17 to rotate, and the transmission shaft 17 drives the gear 20 to rotate, thereby realizing the rotation of the gear along the arc-shaped rack, driving the entire frame to perform circular motion around the wheel fixture.

[0086] The base 1 of the laser cladding device is connected to the guide sleeve through a telescopic member 21, and the laser cladding nozzle 2, laser 3, and ultrasonic impact device 4 are installed on the base 1. The laser cladding nozzle 2 can slide left and right on the guide column through the action of a cylinder or an electric push rod, and the laser cladding nozzle can move up and down through the action of the telescopic member 21. The telescopic member can be a cylinder or an electric push rod. The frame can also make circumferential movements around the wheel disc of the turbine rotor, so that the segmented multi-layer laser cladding action of the turbine rotor wheel disc can be achieved. The ultrasonic wave emitted by the ultrasonic impact device is located at the front side of the laser cladding. When the laser cladding starts, the laser cladding nozzle makes circumferential movements around the wheel disc of the turbine rotor, and the ultrasonic impact device also makes circumferential movements, so that the action of laser cladding and ultrasonic stress relief is achieved at the same time, and stress relief is achieved in real time. The entire device can achieve automated control of laser cladding through a control system. Workers only need to input the number of laser cladding layers, the segmented arc length, and the thickness of each layer to perform automatic laser cladding. This replaces manual handheld laser cladding equipment for laser cladding, greatly improving laser cladding efficiency while freeing up manpower and reducing worker intensity. The control system simply controls the three movements of the laser cladding nozzle: up and down movement, left and right sliding, and circumferential rotation. This simple control requires only a simple control program, making the entire control system easy to build and low-cost.

[0087] In this embodiment, the entire installation and operation process is as follows:

[0088] Workers clamp four curved rails 7 onto the left side of the turbine rotor disc 6 and tighten bolts 19 to secure the curved rails 7 to the disc 6. They then clamp another four curved rails 7 onto the right side of the turbine rotor disc 6 and tighten bolts 19 to secure the curved rails 7 to the right side of the disc 6. The curved frames 11 of the frame are then installed on the curved rails 7. After assembly, the T-shaped stopper 10 is retained within the circular groove 110 of the curved frame 11, and the gear 20 engages with the curved rack 9. The control system is connected to the ultrasonic impact device 4, the laser 3, the electric push rod or cylinder that drives the machine base 1 to move left and right, the telescopic part 21 that drives the machine base 1 to move up and down, and the drive motor that drives the gear 20 to rotate. The control system sends control signals to the ultrasonic impact device 4, the laser 3, the electric push rod or cylinder, the telescopic part 21, and the drive motor to control the laser emission of the laser, the impact action of the ultrasonic impact device, and the left and right, up and down, and circumferential movements of the laser cladding nozzle, thereby realizing automatic control of the entire laser cladding action, replacing manual hand-held laser cladding equipment for laser cladding.

[0089] Based on the above embodiments, the present invention adopts multi-layer laser cladding during laser cladding, and the thickness of each cladding layer is controlled between 0.7mm-9mm. Moreover, polishing and ultrasonic impact stress relief are performed after each section of cladding to eliminate stress in real time. Moreover, during cladding, the laser power is 2500-3000W, the linear speed is 800-1000mm / min, and the powder feeding amount is 28-31.5g / min. The cladding is performed in sections with a length of 250-300mm and symmetrical 180 degrees to prevent deformation, and multimodal detection technology is integrated to ensure the quality of the repair. After repair, the rotor runout value is ≤0.02mm, the hardness matches the substrate, and it is suitable for high temperature and high pressure conditions of 530℃. Compared with the traditional rotor replacement solution, the cost is reduced by 90%, and it has significant industrial application value. Cladding is performed in sections with a length of 250-300mm and symmetrical 180 degrees. This not only prevents cladding deformation, but also allows cladding and stress relief to be performed in sections during laser cladding. Each section is subjected to PT non-destructive testing and phased array ultrasonic testing to avoid the occurrence of cracks, thus ensuring the cladding quality of each section of laser cladding. After the multiple sections are clad, a layer of laser cladding layer is formed. This layer of laser cladding layer is subjected to ultrasonic impact stress relief, and the entire layer is stress relieved again to further reduce stress. This layer is then subjected to PT non-destructive testing and phased array ultrasonic testing to avoid the occurrence of cracks, ensuring that the entire layer of laser cladding layer has low stress and no cracks. Through this segmented multi-layer laser cladding method, it is possible to ensure that each section and each layer of the laser cladding layer has low stress and no cracks, thereby ensuring that the entire laser cladding layer has low stress and no cracks. The cladding material used in the present invention is nickel-based powder alloy powder, wherein Cr: 20%, Mo: 10.5%, Nb: 2%, Fe: 3.5%, and Ti: 0.35%. When laser cladding is performed on nickel-based alloy powder with this composition ratio, the hardness of the laser cladding layer formed can better match the substrate. When ultrasonic impact stress relief is performed, the cladding layer will not produce cracks, which can further ensure the quality of laser cladding.

[0090] Although the present invention has been described herein with reference to a number of illustrative embodiments thereof, it will be understood that numerous other modifications and implementations may be devised by those skilled in the art that fall within the scope and spirit of the principles disclosed herein. More specifically, within the scope of the present disclosure, the drawings, and the claims, numerous variations and modifications may be made to the components and / or layout of the subject combination arrangement. In addition to variations and modifications to the components and / or layout, other uses will also be apparent to those skilled in the art.

Claims

1. A steam turbine rotor R corner laser cladding repair process, characterized by: The steps include: Steam turbine rotor R angle detection steps: detect the steam turbine rotor R angle to obtain the wear depth and crack depth of the steam turbine R angle; Fatigue layer and crack removal steps: Determine the depth of machining based on the crack depth detected at the R corner of the steam turbine, and remove the fatigue layer and crack at the R corner of the steam turbine rotor by machining; Steps to determine the laser cladding repair thickness: Calculate the laser cladding repair thickness based on the wear depth of the turbine R corner and the machining depth; Determine the laser cladding scheme: Perform segmented multi-layer laser cladding on the R corner of the turbine rotor, and determine the laser cladding scheme based on the calculated laser cladding repair thickness. The laser cladding scheme includes the number of laser cladding layers and the thickness of each laser cladding layer. Laser cladding and stress control steps: laser cladding is performed using a laser cladding device according to a laser cladding plan. The laser cladding device includes a laser cladding nozzle, a laser, a machine base, a wheel fixing device and a frame. The wheel fixing device is fixed on the wheel of the turbine rotor. The frame is installed on the wheel fixing device. The frame can rotate circumferentially on the wheel fixing device. The machine base is connected to the frame. The machine base can slide left and right and move up and down on the frame. The laser cladding nozzle and laser are installed on the machine base.

2. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 1, characterized in that: The wheel disc fixing device includes multiple arc tracks, the lower part of the arc track is provided with bolt holes, the inner groove of the arc track is provided with an arc rack, and one side of the arc track is provided with a T-shaped limit piece, and the T-shaped limit piece extends along the arc track; the frame includes an arc frame, the arc frame is provided with a round groove, the round groove is provided with an opening, and the round groove is adapted to the T-shaped limit piece, a mounting plate is fixed on the top of the arc frame, the lower side surfaces of the left and right ends of the mounting plate are connected to the guide columns through connecting blocks, and a guide sleeve is installed on the guide column, and the guide sleeve can slide left and right on the guide column, and the mounting plate is also installed with a transmission shaft through a connecting seat, and the transmission shaft is installed on the connecting seat through a bearing, and a transmission gear is sleeved on the transmission shaft, and the transmission gear is connected to a driving motor, and a gear is sleeved on the left and right ends of the transmission shaft, and the gear is meshed with the arc rack of the arc track.

3. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 2, characterized in that: The machine base is connected to the guide sleeve through a telescopic member. The machine base can move up and down on the frame through the action of the telescopic member, and can slide left and right on the frame through the action of the guide sleeve.

4. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 1, characterized in that: When performing segmented multi-layer laser cladding on the R corner of a steam turbine, the laser power is 2500-3000W, the linear speed is 800-1000mm / min, the powder feed rate is 28-31.5g / min, and the segmented arc length is 250-300mm.

5. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 1, characterized in that: In the laser cladding and stress control step, when performing segmented multi-layer laser cladding, the laser cladding material is nickel-based powder alloy powder, which is calculated by weight as follows: Cr: 20-24%, Mo: 7-10.5%, Nb: 2-4.5%, Fe: 2.5-3.5%, Ti: 0.2-0.35%, and the balance is Ni.

6. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 1, characterized in that: In the laser cladding and stress control steps, after each section of laser cladding is completed, the cladding layer of that section needs to be polished, and then subjected to ultrasonic impact treatment after polishing, with an impact speed of 200 mm / s and an impact strength of 0.15-0.25 mmA, and then PT non-destructive testing is performed.

7. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 6, characterized in that: In the laser cladding and stress control steps, after each layer of laser cladding is completed, the cladding layer is subjected to ultrasonic impact treatment and PT non-destructive testing.

8. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 1, characterized in that: In the laser cladding and stress control step, the actual laser cladding thickness according to the laser cladding plan is greater than the laser cladding repair thickness calculated in the step of determining the laser cladding repair thickness by more than 1 mm.

9. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 1, characterized in that: After completing the laser cladding and stress control steps, the R corner of the turbine rotor is rough-machined. After rough machining, the surface roughness of the cladding layer at the R corner of the turbine rotor is Ra≤3.2μm; after rough machining, PT non-destructive testing, phased array ultrasonic testing and residual stress testing are also performed.

10. The laser cladding repair process for the R corner of a steam turbine rotor according to claim 1, characterized in that: After rough machining, the R corner of the turbine rotor is fine-machined. After fine machining, the surface roughness of the R corner cladding layer of the turbine rotor is Ra≤1.6μm; after fine machining, PT non-destructive testing, hardness testing and runout testing are carried out.

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