Broken tooth repairing method based on laser cladding technology

Abstract

The invention discloses a broken tooth repairing method based on a laser cladding technology. The broken tooth repairing method is specifically implemented according to the following steps that 1, the profile of a broken tooth surface is obtained; 2, broken tooth repairing preparation; 3, repairing the section; and 4, heat treatment and performance optimization. The broken gear can be efficiently repaired, the mechanical property and the tribological property of the broken gear can be improved, and the service life of the gear is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of gear repair, and in particular relates to a broken tooth repair method based on laser cladding technology. Background Art

[0002] The rocker gear transmission system of underground coal mining machines is a critical component of coal mining equipment, fulfilling the core function of power transmission. These gears operate under extremely harsh conditions for a long time. Not only do they withstand cyclical alternating loads and transient shock loads, but they are also constantly exposed to high concentrations of coal dust, moisture, and corrosive media. This combined stress easily causes early damage to the gear surfaces, such as micropitting, spalling, and plastic deformation, which can progress to severe tooth wear and even tooth breakage. According to statistics, gearbox failures account for over 35% of coal mining machinery failures, with rocker gear damage accounting for the majority of these failures. These failures not only significantly reduce the equipment's transmission efficiency but also cause abnormal vibration and noise. In severe cases, they can cause the entire machine to shut down, resulting in significant economic losses and safety risks to coal mining operations.

[0003] Traditional gear repair techniques primarily rely on physical finishing or complete replacement. While physical finishing methods such as manual surfacing and mechanical grinding are simple to operate, they have significant technical limitations: The repair process makes it difficult to precisely control heat input, which can easily lead to structural degradation and residual stress concentration in the base material. The tooth profile accuracy after repair often fails to meet design requirements, significantly reducing meshing performance. More critically, these methods fail to fundamentally improve the mechanical properties of the material, and the repaired area often becomes a new weak link, making secondary failure more likely during subsequent use. While complete replacement solutions can guarantee equipment performance, they face challenges such as high procurement costs, heavy spare parts inventory pressures, and prolonged downtime. Especially for large coal mining gears, the procurement cost of a single piece can reach hundreds of thousands of yuan, and the cycle from order placement to delivery often takes several months, seriously impacting the coal mine's normal production schedule.

[0004] With the advancement of remanufacturing technology, laser cladding has become a research hotspot in gear repair due to its unique advantages. This technique uses a high-energy laser beam to metallurgically bond a specific alloy powder to the base material, producing a high-performance cladding layer with minimal heat input. Compared to traditional overlay welding, laser cladding offers significant advantages, including a narrow heat-affected zone, low dilution rate, and high bond strength. However, the successful application of this technology in gear repair still faces numerous technical challenges. First, the complex three-dimensional morphology of the broken tooth area makes high-precision reconstruction difficult using conventional measurement methods. Second, the cladding material must achieve good metallurgical compatibility and performance matching with the gear substrate (such as alloy steels such as 42CrMo and 18CrNiMo7-6). Furthermore, the unique geometric characteristics of the gear surface place stringent requirements on the cladding process parameters. These technical bottlenecks have severely hampered the widespread application of laser cladding technology in gear repair. Summary of the Invention

[0005] The purpose of the present invention is to provide a broken tooth repair method based on laser cladding technology, which can not only achieve efficient repair of broken gear teeth, but also improve its mechanical properties and tribological properties, thereby extending the service life of the gear.

[0006] The technical solution adopted by the present invention is a broken tooth repair method based on laser cladding technology, which is specifically implemented according to the following steps: Step 1: Obtain the broken tooth surface profile; Step 2: Preparation for broken tooth repair; Step 3: Section repair; Step 4: Heat treatment and performance optimization.

[0007] The present invention is also characterized in that: Step 1 is implemented as follows: Step 1.1: Ultrasonic clean the gears for 10-30 minutes to ensure that the gear surfaces are completely free of grease, dust, and other contaminants. Dry the cleaned gears at 30-40°C for 15-20 minutes to ensure that no moisture remains. Step 1.2, cross-sectional scanning and calibration: Based on the size of the gear and the shape of the broken teeth, a high-resolution CT scanner and a standard calibration plate are used to scan and calibrate the equipment to ensure scanning accuracy. The calibration error of the scanner is less than ±0.01 mm. Step 1.3. Scan the broken tooth area: For CT scanning, use slice scanning with a resolution of 50μm and a scanning time of 30-50 minutes to ensure that each layer of data can accurately reconstruct the internal structure and surface morphology of the gear. For laser scanning, use continuous scanning mode, and control the spacing between each measurement point within 0.2mm. Scan at least 5mm around the broken tooth to ensure that the tooth surface damage and defects are included. Step 1.4: Data processing and cross-section reconstruction.

[0008] Step 1.4 is as follows: Step 1.4.1. Data import and preprocessing: The scanned point cloud data was imported into 3D processing software and preprocessed. The preprocessing included: for laser scanning data, noise removal and outlier filtering were performed, and the iterative closest point (ICP) algorithm was used for multi-view point cloud stitching to ensure a stitching error of ≤0.03mm. For CT scan data, the threshold segmentation method was used to remove metal artifacts, and the broken tooth area was extracted using the region growing algorithm. The grayscale threshold range was set to 2000-3000HU. Step 1.4.2, 3D geometric model reconstruction: For laser scanning data, Delaunay triangulation was used for surface reconstruction, with the maximum triangle side length set to ≤0.05 mm, the curvature sampling angle set to 15°, and the sharp edge protection mode enabled to ensure the accuracy of broken tooth edges. For CT scanning data, the FDK back-projection algorithm was used for tomographic reconstruction, with a slice thickness of ≤0.1 mm. 3D models were generated by isosurface extraction, with a threshold error set to <0.03 mm. Step 1.4.3, model optimization and accuracy verification: Perform mesh diagnosis to ensure that the number of non-manifold edges is ≤10 and there are no self-intersecting surfaces. Use 3D comparison tools to verify the deviation between the model and the original point cloud, and control the tolerance range within ±0.05mm. Take at least five section lines at key locations on the tooth surface for comparison to ensure that the overall dimensional error is ≤±0.08mm and the local feature error is ≤±0.05mm. Step 1.4.4. Model output Save the optimized 3D model as a standard format file, including: STL format (binary), with the number of triangles controlled between 500,000 and 1,000,000, and the chord height tolerance set to 0.01mm; STEP or IGES format, ensuring that complete entity information is included.

[0009] Step 2 is implemented as follows: Step 2.1. Clean the gear surface with a cleaning agent: the cleaning agent is isopropyl alcohol (IPA) or acetone (CH3COCH3), and the cleaning time is 10-20 minutes. Then, use alumina with a particle size of 80-120 mesh for sandblasting, and the spray pressure is 0.4-0.6 MPa. For stubborn oil stains, use trichloroethylene (C2HCl3) or acetone (CH3COCH3) for degreasing. After cleaning, wipe it clean with anhydrous ethanol. If there are still defects on the surface, use CNC precision milling or grinding wheel grinding for finishing, and control the grinding feed rate to 0.01-0.02 mm / time, and the roughness reaches Ra 0.8-1.2 μm. Step 2.2, geometric shape repair and optimization: Based on the broken tooth surface contour obtained by scanning, the broken tooth defect area is repaired using the finite element analysis method FEM.

[0010] Step 2.2 is implemented as follows: The scanned 3D model of the broken tooth was imported into finite element analysis software, compared with a standard gear model, and the boundaries of the defect area were extracted to establish a parameterized defect model. After setting the mechanical parameters of the base material and the Ni60A cladding layer, a stress analysis was performed by applying 1.5 times the rated load to identify high-stress areas. A topology optimization method was used to generate the optimal restoration shape with stiffness and strength as optimization targets, and a layered cladding scheme was formulated, including a 0.2mm layer height, a 0.8-1.2mm path spacing, and a cross-scanning process in high-stress areas. The preheating temperature was controlled at 200±10°C and the interlayer temperature was ≤150°C. By verifying the stress distribution and fatigue performance of the restoration, a 3D model and processing path were output, which reduced the weight of the restoration by 20-35%, reduced the stress concentration factor to below 1.2, and achieved a service life of more than 85% of that of a new tooth. The repair path was optimized. The repair material used was Ni60A nickel-based alloy powder with a particle size of 50-150 μm and a cladding thickness of 1.0-2.0 mm to ensure that the repaired tooth surface had good wear resistance and fatigue strength. On the surface of the repaired area, a MoS2 or TiC reinforcement coating was applied using plasma spraying APS technology with a coating thickness of 0.2-0.3 mm. The gear base material was preheated for 20-30 minutes to reduce the occurrence of thermal cracks and improve the bonding strength between the cladding layer and the base material.

[0011] Step 3 is implemented as follows: Step 3.1, laser cladding repair: Use laser cladding technology to repair broken teeth. The laser power is set to 1000-1500 W, the scanning speed is 6-10 mm / s, the powder feed rate is controlled at 12-18 g / min, the cladding layer thickness is 1.0-2.0 mm, and the protective gas is argon with a gas flow rate of 15-20 L / min to ensure stability during the cladding process and avoid oxidation and the formation of pores. During the cladding process, 5-10 scans are performed according to the actual size of the gear, and the layers are gradually accumulated to ensure that the repair layer is uniform and dense. Step 3.2: Heat treatment after laser cladding: Using a quenching and tempering process, heat the repaired gear to 850-900°C, hold for 30-60 minutes, and then quickly quench in an oil bath. After quenching, hold for another 3-4 hours to improve the hardness and fatigue resistance of the repair layer. After heat treatment, the surface hardness of the gear reaches HRC 55-60. Step 3.3, subsequent processing and finishing: After heat treatment, the repair area is subjected to CNC precision machining or grinding to ensure that the interface between the repair layer and the substrate is smooth and the accuracy meets the requirements. After machining, it is ground with a roughness requirement of Ra 0.4~0.8μm to ensure the flatness of the tooth surface and appropriate contact spots. In addition, the repaired area is subjected to non-destructive testing to check whether there are cracks or voids in the repair layer to ensure that the repair quality meets the standards.

[0012] The precision machining process in step 3.3 includes the following: rough machining phase: using a φ6mm carbide end mill at a speed of 8000 r / min, a feed rate of 1500 mm / min, a cutting depth of 0.5mm, and removing the cladding layer allowance; semi-finishing phase: replacing with a φ4mm ball end mill at a speed of 12000 r / min, a feed rate of 800 mm / min, and a cutting depth of 0.2mm; finishing phase: using a φ2mm diamond-coated milling cutter at a speed of 15000 r / min, a feed rate of 500 mm / min, and a cutting depth of 0.05mm, and the final surface roughness reaches Ra0.8μm; When processing the repair layer with hardness greater than 50HRC, a precision grinding process is adopted. The processing process includes: rough grinding stage: using 80# white corundum grinding wheel, linear speed 35m / s, feed speed 0.1mm / pass, grinding depth 0.02mm; fine grinding stage: replacing 240# CBN grinding wheel, linear speed 45m / s, feed speed 0.05mm / pass, grinding depth 0.005mm; finishing stage: using 800# diamond grinding wheel for polishing, and the surface roughness is controlled within Ra0.4μm.

[0013] Step 4 is implemented as follows: Step 4.1. Pretreatment before heat treatment: First, the repair area is further refined by computer numerical control (CNC) machining, including: rough machining with a φ6 mm carbide end mill at a speed of 6000-8000 r / min, a feed of 800-1200 mm / min, and a 0.2 mm allowance, followed by semi-finishing with a φ4 mm ball end mill at a speed of 10000-12000 r / min, a feed of 500-800 mm / min, and finally finishing with a φ2 mm diamond-coated milling cutter at a speed of 15000-18000 r / min, a feed of 300-500 mm / min, ensuring a surface roughness of Ra 0.8 μm and a contour accuracy of ±0.02 mm. After processing, ultrasonic cleaning and acetone wiping are used to provide a qualified surface for heat treatment. After that, the gears are evenly heated to 250-300℃ and kept warm for 30-60 minutes to eliminate stress and avoid cracks during the heat treatment process. Step 4.2, quenching treatment: Heat the gear to 850-900℃ and keep it warm for 30-60 minutes to ensure that the repair layer and the matrix are fully austenitized. Then, quickly immerse the gear in an oil bath for quenching. The cooling rate is controlled at 20-30℃ / min. The surface hardness of the gear after quenching reaches HRC 55-60, which meets the requirements of high load and wear resistance. Step 4.3 Tempering: After quenching, tempering treatment is performed to reduce the brittleness of the material and optimize its mechanical properties. Heat the gear to 300-400℃ and maintain the temperature for 2-4h, then cool it naturally to room temperature.

[0014] The beneficial effect of the present invention is that the broken tooth repair method based on laser cladding technology establishes a complete gear laser cladding repair technology system through the innovative integration of key technologies such as high-precision three-dimensional scanning, material formulation optimization, precise control of laser process parameters, and customized heat treatment. This technology not only accurately restores the geometric shape of the gear, but also significantly improves the mechanical properties and service life of the repaired area, providing a new technical solution to the difficult problem of coal mine machinery gear repair. Compared with existing technologies, this method has significant advantages such as high repair accuracy, good performance recovery, and excellent cost-effectiveness, and has broad application prospects in the field of mining machinery remanufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the damaged area of ​​the gear to be repaired in the present invention; Figure 2 It is a gear repair flow chart of the present invention; Figure 3 It is the surface morphology before and after the wheel fracture repair in the present invention. DETAILED DESCRIPTION

[0016] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] The present invention is based on the broken tooth repair method of laser cladding technology, combined with Figure 2 , specifically follow the steps below: Step 1: Obtain the broken tooth surface profile; Combine Figure 1 , step 1 is implemented according to the following steps: Step 1.1: Ultrasonic clean the gears with a cleaning agent for 10-30 minutes to ensure that grease, dust, and other contaminants are completely removed from the gear surface. The cleaned gears are then dried in a drying oven at 30-40°C for 15-20 minutes to ensure that no moisture remains. The cleaning agent is a 50% isopropyl alcohol (IPA) solution or an ethyl acetate solution.

[0018] Step 1.2, Cross-Section Scanning and Calibration: Depending on the size of the gear and the fractured tooth morphology, a CT scanner or laser scanner is preferred. If the fractured tooth area is deep or the gear is large, a high-resolution CT scanner (such as the GE vtomex M 240, with a maximum resolution of 5μm) should be used. If the gear is small or the fractured tooth morphology is simple, a laser scanner (such as the Hexagon LaserScanner, with a resolution of up to 0.1 mm) should be used. Use a standard calibration plate (such as a 3D measurement calibration plate, measuring 200mm × 200mm × 50mm) to calibrate the device to ensure scanning accuracy. The scanner calibration error should be less than ±0.01 mm. Step 1.3. Scan the broken tooth area: For CT scanning, use slice scanning with a resolution of 50μm and a scanning time of 30-50 minutes to ensure that each layer of data can accurately reconstruct the internal structure and surface morphology of the gear. For laser scanning, use continuous scanning mode, and control the spacing between each measurement point within 0.2mm. Scan at least 5mm around the broken tooth to ensure that the tooth surface damage and defects are included. Step 1.4: Data processing and cross-section reconstruction.

[0019] Step 1.4 is as follows: Step 1.4.1. Data import and preprocessing: Import the scanned point cloud data into 3D processing software (such as Geomagic Design X or MeshLab) and perform preprocessing. For laser scanning data, perform noise removal and outlier filtering, and use the iterative closest point (ICP) algorithm to stitch the multi-view point cloud together, ensuring a stitching error of ≤0.03mm. For CT scan data, use threshold segmentation to remove metal artifacts and use the region growing algorithm to extract broken tooth areas, setting the grayscale threshold to 2000-3000 HU. Step 1.4.2, 3D geometric model reconstruction: For laser scanning data, Delaunay triangulation was used for surface reconstruction, with the maximum triangle side length set to ≤0.05 mm, the curvature sampling angle set to 15°, and the sharp edge protection mode enabled to ensure the accuracy of broken tooth edges. For CT scanning data, the FDK back-projection algorithm was used for tomographic reconstruction, with a slice thickness of ≤0.1 mm. 3D models were generated by isosurface extraction, with a threshold error set to <0.03 mm. Step 1.4.3, model optimization and accuracy verification: Perform mesh diagnosis to ensure that the number of non-manifold edges is ≤10 and there are no self-intersecting surfaces. Use 3D comparison tools to verify the deviation between the model and the original point cloud, and control the tolerance range within ±0.05mm. Take at least five section lines at key locations on the tooth surface for comparison to ensure that the overall dimensional error is ≤±0.08mm and the local feature error is ≤±0.05mm. Step 1.4.4. Model output Save the optimized 3D model as a standard format file, including: STL format (binary), with the number of triangles controlled between 500,000 and 1,000,000, and the chord height tolerance set to 0.01mm; STEP or IGES format, ensuring that complete entity information is included.

[0020] Step 2: Preparation for broken tooth repair; Step 2 is implemented as follows: Step 2.1. Clean the gear surface with a cleaning agent: the cleaning agent is isopropyl alcohol (IPA) or acetone (CH3COCH3), and the cleaning time is 10-20 minutes. Then, use alumina with a particle size of 80-120 mesh for sandblasting, and the spray pressure is 0.4-0.6 MPa. For stubborn oil stains, use trichloroethylene (C2HCl3) or acetone (CH3COCH3) for degreasing. After cleaning, wipe it clean with anhydrous ethanol. If there are still defects on the surface, use CNC precision milling or grinding wheel (SiC grinding wheel, grit size 600#) for finishing, and control the grinding feed rate to 0.01-0.02 mm / time, and the roughness reaches Ra 0.8-1.2 μm. Step 2.2, geometric shape repair and optimization: Based on the broken tooth surface contour obtained by scanning, the broken tooth defect area is repaired using the finite element analysis method FEM.

[0021] Step 2.2 is implemented as follows: The scanned 3D model of the broken tooth was imported into finite element analysis software, compared with a standard gear model, and the boundaries of the defect area were extracted to establish a parameterized defect model. After setting the mechanical parameters of the base material and the Ni60A cladding layer, a stress analysis was performed by applying 1.5 times the rated load to identify high-stress areas. A topology optimization method was used to generate the optimal restoration shape with stiffness and strength as optimization targets, and a layered cladding scheme was formulated, including a 0.2mm layer height, a 0.8-1.2mm path spacing, and a cross-scanning process in high-stress areas. The preheating temperature was controlled at 200±10°C and the interlayer temperature was ≤150°C. By verifying the stress distribution and fatigue performance of the restoration, a 3D model and processing path were output, which reduced the weight of the restoration by 20-35%, reduced the stress concentration factor to below 1.2, and achieved a service life of more than 85% of that of a new tooth. The repair path was optimized. The repair material used was Ni60A nickel-based alloy powder with a particle size of 50-150 μm and a cladding thickness of 1.0-2.0 mm to ensure that the repaired tooth surface had good wear resistance and fatigue strength. On the surface of the repaired area, a MoS2 or TiC reinforcement coating was applied using plasma spraying APS technology with a coating thickness of 0.2-0.3 mm. For the gear base material (such as 42CrMo, 18CrNiMo7-6, etc.), a preheating treatment of 20-30 minutes was performed to reduce the occurrence of thermal cracks and improve the bonding strength between the cladding layer and the base material.

[0022] Step 3: Section repair; Combine Figure 3 , step 3 is implemented as follows: Step 3.1, laser cladding repair: Use laser cladding technology to repair broken teeth. The laser power is set to 1000-1500 W, the scanning speed is 6-10 mm / s, the powder feed rate is controlled at 12-18 g / min, the cladding layer thickness is 1.0-2.0 mm, and the protective gas is argon with a gas flow rate of 15-20 L / min to ensure stability during the cladding process and avoid oxidation and the formation of pores. During the cladding process, 5-10 scans are performed according to the actual size of the gear, and the layers are gradually accumulated to ensure that the repair layer is uniform and dense. Step 3.2: Heat treatment after laser cladding: Using a quenching and tempering process, heat the repaired gear to 850-900°C, hold for 30-60 minutes, and then quickly quench in an oil bath. After quenching, hold for another 3-4 hours to improve the hardness and fatigue resistance of the repair layer. After heat treatment, the surface hardness of the gear reaches HRC 55-60. Step 3.3, subsequent processing and finishing: After heat treatment, the repaired area is precision machined using Computer Numerical Control (CNC) or ground with a grinding wheel to ensure that the interface between the repair layer and the substrate is smooth and meets the required accuracy. After machining, it is ground to a roughness of Ra 0.4-0.8 μm to ensure tooth surface flatness and appropriate contact spots. In addition, the repaired area is subjected to non-destructive testing (such as X-ray inspection or ultrasonic testing) to check whether there are cracks or voids in the repair layer to ensure that the repair quality meets the standards.

[0023] The precision machining process in step 3.3 includes the following: rough machining phase: using a φ6mm carbide end mill at a speed of 8000 r / min, a feed rate of 1500 mm / min, a cutting depth of 0.5mm, and removing the cladding layer allowance; semi-finishing phase: replacing with a φ4mm ball end mill at a speed of 12000 r / min, a feed rate of 800 mm / min, and a cutting depth of 0.2mm; finishing phase: using a φ2mm diamond-coated milling cutter at a speed of 15000 r / min, a feed rate of 500 mm / min, and a cutting depth of 0.05mm, and the final surface roughness reaches Ra0.8μm; When processing the repair layer with hardness greater than 50HRC, a precision grinding process is adopted. The processing process includes: rough grinding stage: using 80# white corundum grinding wheel, linear speed 35m / s, feed speed 0.1mm / pass, grinding depth 0.02mm; fine grinding stage: replacing 240# CBN grinding wheel, linear speed 45m / s, feed speed 0.05mm / pass, grinding depth 0.005mm; finishing stage: using 800# diamond grinding wheel for polishing, and the surface roughness is controlled within Ra0.4μm.

[0024] Step 4: Heat treatment and performance optimization.

[0025] Step 4 is implemented as follows: Step 4.1. Pretreatment before heat treatment: First, the repair area is further refined by computer numerical control (CNC) machining, including rough machining with a φ6 mm carbide end mill at a speed of 6000-8000 r / min, a feed of 800-1200 mm / min, and a 0.2 mm margin. Subsequently, semi-finishing is performed with a φ4 mm ball end mill at a speed of 10000-12000 r / min, a feed of 500-800 mm / min, and finally finishing is performed with a φ2 mm diamond-coated milling cutter at a speed of 15000-18000 r / min, a feed of 300-500 mm / min, ensuring a surface roughness of Ra 0.8 μm and a contour accuracy of ±0.02 mm. After processing, ultrasonic cleaning and acetone wiping are used to provide a qualified surface for heat treatment. After that, the gears are evenly heated. The gears are heated to 250-300℃ and kept warm for 30-60 minutes to eliminate stress and avoid cracks during the heat treatment process. During the preheating process, an electric furnace or an atmosphere furnace is used for heating to ensure a uniform heating speed and avoid rapid temperature changes.

[0026] Step 4.2, quenching treatment: Heat the gear to 850-900℃ and keep it warm for 30-60 minutes to ensure that the repair layer and the matrix are fully austenitized. Then, quickly immerse the gear in an oil bath for quenching. The cooling rate is controlled at 20-30℃ / min to avoid excessive internal stress. The surface hardness of the gear after quenching reaches HRC 55-60, which meets the requirements of high load and wear resistance. Step 4.3: Tempering: After quenching, tempering is performed to reduce the material's brittleness and optimize its mechanical properties. Heat the gear to 300-400°C and maintain this temperature for 2-4 hours, then cool naturally to room temperature. Tempering improves the gear's overall mechanical properties, enhancing its toughness and fatigue resistance, ensuring the repaired gear can withstand repeated loads without failure in actual operation.

[0027] Example 1 The broken tooth repair method based on laser cladding technology of the present invention is specifically implemented according to the following steps: Step 1: Obtain the broken tooth surface profile; Step 2: Preparation for broken tooth repair; Step 3: Section repair; Step 4: Heat treatment and performance optimization.

[0028] Example 2 The broken tooth repair method based on laser cladding technology of the present invention is specifically implemented according to the following steps: Step 1: Obtain the broken tooth surface profile; Step 1 is implemented as follows: Step 1.1: Ultrasonic clean the gears with a cleaning agent for 10-30 minutes to ensure that grease, dust, and other contaminants are completely removed from the gear surface. The cleaned gears are then dried in a drying oven at 30-40°C for 15-20 minutes to ensure that no moisture remains. The cleaning agent is a 50% isopropyl alcohol (IPA) solution or an ethyl acetate solution.

[0029] Step 1.2, Cross-Section Scanning and Calibration: Depending on the size of the gear and the fractured tooth morphology, a CT scanner or laser scanner is preferred. If the fractured tooth area is deep or the gear is large, a high-resolution CT scanner (such as the GE vtomex M 240, with a maximum resolution of 5μm) should be used. If the gear is small or the fractured tooth morphology is simple, a laser scanner (such as the Hexagon LaserScanner, with a resolution of up to 0.1 mm) should be used. Use a standard calibration plate (such as a 3D measurement calibration plate, measuring 200mm × 200mm × 50mm) to calibrate the device to ensure scanning accuracy. The scanner calibration error should be less than ±0.01 mm. Step 1.3. Scan the broken tooth area: For CT scanning, use slice scanning with a resolution of 50μm and a scanning time of 30-50 minutes to ensure that each layer of data can accurately reconstruct the internal structure and surface morphology of the gear. For laser scanning, use continuous scanning mode, and control the spacing between each measurement point within 0.2mm. Scan at least 5mm around the broken tooth to ensure that the tooth surface damage and defects are included. Step 1.4: Data processing and cross-section reconstruction.

[0030] Step 1.4 is as follows: Step 1.4.1. Data import and preprocessing: Import the scanned point cloud data into 3D processing software (such as Geomagic Design X or MeshLab) and perform preprocessing. For laser scanning data, perform noise removal and outlier filtering, and use the iterative closest point (ICP) algorithm to stitch the multi-view point cloud together, ensuring a stitching error of ≤0.03mm. For CT scan data, use threshold segmentation to remove metal artifacts and use the region growing algorithm to extract broken tooth areas, setting the grayscale threshold to 2000-3000 HU. Step 1.4.2, 3D geometric model reconstruction: For laser scanning data, Delaunay triangulation was used for surface reconstruction, with the maximum triangle side length set to ≤0.05 mm, the curvature sampling angle set to 15°, and the sharp edge protection mode enabled to ensure the accuracy of broken tooth edges. For CT scanning data, the FDK back-projection algorithm was used for tomographic reconstruction, with a slice thickness of ≤0.1 mm. 3D models were generated by isosurface extraction, with a threshold error set to <0.03 mm. Step 1.4.3, model optimization and accuracy verification: Perform mesh diagnosis to ensure that the number of non-manifold edges is ≤10 and there are no self-intersecting surfaces. Use 3D comparison tools to verify the deviation between the model and the original point cloud, and control the tolerance range within ±0.05mm. Take at least five section lines at key locations on the tooth surface for comparison to ensure that the overall dimensional error is ≤±0.08mm and the local feature error is ≤±0.05mm. Step 1.4.4. Model output Save the optimized 3D model as a standard format file, including: STL format (binary), with the number of triangles controlled between 500,000 and 1,000,000, and the chord height tolerance set to 0.01mm; STEP or IGES format, ensuring that complete entity information is included.

[0031] Step 2: Preparation for broken tooth repair; Step 3: Section repair; Step 4: Heat treatment and performance optimization.

[0032] Example 3 The broken tooth repair method based on laser cladding technology of the present invention is specifically implemented according to the following steps: Step 1: Obtain the broken tooth surface profile; Step 1 is implemented as follows: Step 1.1: Ultrasonic clean the gears with a cleaning agent for 10-30 minutes to ensure that grease, dust, and other contaminants are completely removed from the gear surface. The cleaned gears are then dried in a drying oven at 30-40°C for 15-20 minutes to ensure that no moisture remains. The cleaning agent is a 50% isopropyl alcohol (IPA) solution or an ethyl acetate solution.

[0033] Step 1.2, Cross-Section Scanning and Calibration: Depending on the size of the gear and the fractured tooth morphology, a CT scanner or laser scanner is preferred. If the fractured tooth area is deep or the gear is large, a high-resolution CT scanner (such as the GE vtomex M 240, with a maximum resolution of 5μm) should be used. If the gear is small or the fractured tooth morphology is simple, a laser scanner (such as the Hexagon LaserScanner, with a resolution of up to 0.1 mm) should be used. Use a standard calibration plate (such as a 3D measurement calibration plate, measuring 200mm × 200mm × 50mm) to calibrate the device to ensure scanning accuracy. The scanner calibration error should be less than ±0.01 mm. Step 1.3. Scan the broken tooth area: For CT scanning, use slice scanning with a resolution of 50μm and a scanning time of 30-50 minutes to ensure that each layer of data can accurately reconstruct the internal structure and surface morphology of the gear. For laser scanning, use continuous scanning mode, and control the spacing between each measurement point within 0.2mm. Scan at least 5mm around the broken tooth to ensure that the tooth surface damage and defects are included. Step 1.4: Data processing and cross-section reconstruction.

[0034] Step 1.4 is as follows: Step 1.4.1. Data import and preprocessing: Import the scanned point cloud data into 3D processing software (such as Geomagic Design X or MeshLab) and perform preprocessing. For laser scanning data, perform noise removal and outlier filtering, and use the iterative closest point (ICP) algorithm to stitch the multi-view point cloud together, ensuring a stitching error of ≤0.03mm. For CT scan data, use threshold segmentation to remove metal artifacts and use the region growing algorithm to extract broken tooth areas, setting the grayscale threshold to 2000-3000 HU. Step 1.4.2, 3D geometric model reconstruction: For laser scanning data, Delaunay triangulation was used for surface reconstruction, with the maximum triangle side length set to ≤0.05 mm, the curvature sampling angle set to 15°, and the sharp edge protection mode enabled to ensure the accuracy of broken tooth edges. For CT scanning data, the FDK back-projection algorithm was used for tomographic reconstruction, with a slice thickness of ≤0.1 mm. 3D models were generated by isosurface extraction, with a threshold error set to <0.03 mm. Step 1.4.3, model optimization and accuracy verification: Perform mesh diagnosis to ensure that the number of non-manifold edges is ≤10 and there are no self-intersecting surfaces. Use 3D comparison tools to verify the deviation between the model and the original point cloud, and control the tolerance range within ±0.05mm. Take at least five section lines at key locations on the tooth surface for comparison to ensure that the overall dimensional error is ≤±0.08mm and the local feature error is ≤±0.05mm. Step 1.4.4. Model output Save the optimized 3D model as a standard format file, including: STL format (binary), with the number of triangles controlled between 500,000 and 1,000,000, and the chord height tolerance set to 0.01mm; STEP or IGES format, ensuring that complete entity information is included.

[0035] Step 2: Preparation for broken tooth repair; Step 2 is implemented as follows: Step 2.1. Clean the gear surface with a cleaning agent: the cleaning agent is isopropyl alcohol (IPA) or acetone (CH3COCH3), and the cleaning time is 10-20 minutes. Then, use alumina with a particle size of 80-120 mesh for sandblasting, and the spray pressure is 0.4-0.6 MPa. For stubborn oil stains, use trichloroethylene (C2HCl3) or acetone (CH3COCH3) for degreasing. After cleaning, wipe it clean with anhydrous ethanol. If there are still defects on the surface, use CNC precision milling or grinding wheel (SiC grinding wheel, grit size 600#) for finishing, and control the grinding feed rate to 0.01-0.02 mm / time, and the roughness reaches Ra 0.8-1.2 μm. Step 2.2, geometric shape repair and optimization: Based on the broken tooth surface contour obtained by scanning, the broken tooth defect area is repaired using the finite element analysis method FEM.

[0036] Step 2.2 is implemented as follows: The scanned 3D model of the broken tooth was imported into finite element analysis software, compared with a standard gear model, and the boundaries of the defect area were extracted to establish a parameterized defect model. After setting the mechanical parameters of the base material and the Ni60A cladding layer, a stress analysis was performed by applying 1.5 times the rated load to identify high-stress areas. A topology optimization method was used to generate the optimal restoration shape with stiffness and strength as optimization targets, and a layered cladding scheme was formulated, including a 0.2mm layer height, a 0.8-1.2mm path spacing, and a cross-scanning process in high-stress areas. The preheating temperature was controlled at 200±10°C and the interlayer temperature was ≤150°C. By verifying the stress distribution and fatigue performance of the restoration, a 3D model and processing path were output, which reduced the weight of the restoration by 20-35%, reduced the stress concentration factor to below 1.2, and achieved a service life of more than 85% of that of a new tooth. The repair path was optimized. The repair material used was Ni60A nickel-based alloy powder with a particle size of 50-150 μm and a cladding thickness of 1.0-2.0 mm to ensure that the repaired tooth surface had good wear resistance and fatigue strength. On the surface of the repaired area, a MoS2 or TiC reinforcement coating was applied using plasma spraying APS technology with a coating thickness of 0.2-0.3 mm. For the gear base material (such as 42CrMo, 18CrNiMo7-6, etc.), a preheating treatment of 20-30 minutes was performed to reduce the occurrence of thermal cracks and improve the bonding strength between the cladding layer and the base material.

[0037] Step 3: Section repair; Step 4: Heat treatment and performance optimization.

[0038] Step 4 is implemented as follows: Step 4.1. Pretreatment before heat treatment: First, the repair area is further refined by computer numerical control (CNC) machining, including rough machining with a φ6 mm carbide end mill at a speed of 6000-8000 r / min, a feed of 800-1200 mm / min, and a 0.2 mm margin. Subsequently, semi-finishing is performed with a φ4 mm ball end mill at a speed of 10000-12000 r / min, a feed of 500-800 mm / min, and finally finishing is performed with a φ2 mm diamond-coated milling cutter at a speed of 15000-18000 r / min, a feed of 300-500 mm / min, ensuring a surface roughness of Ra 0.8 μm and a contour accuracy of ±0.02 mm. After processing, ultrasonic cleaning and acetone wiping are used to provide a qualified surface for heat treatment. After that, the gears are evenly heated. The gears are heated to 250-300℃ and kept warm for 30-60 minutes to eliminate stress and avoid cracks during the heat treatment process. During the preheating process, an electric furnace or an atmosphere furnace is used for heating to ensure a uniform heating speed and avoid rapid temperature changes.

[0039] Step 4.2, quenching treatment: Heat the gear to 850-900℃ and keep it warm for 30-60 minutes to ensure that the repair layer and the matrix are fully austenitized. Then, quickly immerse the gear in an oil bath for quenching. The cooling rate is controlled at 20-30℃ / min to avoid excessive internal stress. The surface hardness of the gear after quenching reaches HRC 55-60, which meets the requirements of high load and wear resistance. Step 4.3: Tempering: After quenching, tempering is performed to reduce the material's brittleness and optimize its mechanical properties. Heat the gear to 300-400°C and maintain this temperature for 2-4 hours, then cool naturally to room temperature. Tempering improves the gear's overall mechanical properties, enhancing its toughness and fatigue resistance, ensuring the repaired gear can withstand repeated loads without failure in actual operation.

[0040] Example 4 Repair method of broken teeth in rocker gear transmission system of underground coal mining machine based on laser cladding technology Step 1: Obtaining the broken tooth surface profile Step 1 is implemented as follows: Step 1.1: Ultrasonic clean the gears using a 50% isopropyl alcohol (IPA) solution for 20 minutes to completely remove grease, dust, and other contaminants from the gear surfaces. Place the cleaned gears in a drying oven at 30°C for 15 minutes to ensure no moisture remains.

[0041] Step 1.2: Select and calibrate the cross-sectional scanning device. Use a Hexagon Laser Scanner. Calibrate the device using a standard calibration plate (200 mm × 200 mm × 50 mm), ensuring the scanner's calibration error is less than ±0.01 mm.

[0042] Step 1.3 Scan the broken tooth. Select laser scanning and use continuous scanning mode. Keep the spacing between each measurement point within 0.2mm. Scan the 5mm area around the broken tooth to ensure that any damage and defects on the tooth surface are included.

[0043] Step 1.4 Data Processing and Section Reconstruction. Import the scanned point cloud data into the professional software Geomagic Design X for processing. Use the software's 3D reconstruction algorithm to convert the point cloud data into a 3D geometric model. Reconstruct the 3D model using point cloud stitching technology. The reconstructed 3D model should have an accuracy of 0.1 mm to ensure an accurate representation of the geometry of the fractured tooth. Save the generated 3D model in STL format for subsequent restoration and processing.

[0044] Step 2: Preparation for Broken Tooth Repair Step 2 is implemented as follows: Step 2.1: Clean the gear surface with acetone (CH3COCH3) for 10 minutes. Then, sandblast with aluminum oxide (100-mesh grit) at a pressure of 0.6 MPa. For stubborn oil stains, degrease with trichloroethylene (C2HCl3) and wipe clean with anhydrous ethanol. If any surface defects remain, refinish them using CNC precision milling to a roughness of Ra 0.8 μm.

[0045] Step 2.2: Geometric Repair and Optimization. Based on the scanned tooth profile, the broken tooth defect area was repaired using finite element analysis (FEM) to optimize the repair path. The repair material used was Ni60A nickel-based alloy powder (particle size 100 μm), with a cladding thickness of 1 mm to ensure good wear resistance and fatigue strength of the repaired tooth surface. A MoS2 reinforcement coating with a thickness of 0.2 mm was applied to the repaired area using plasma spraying (APS). The gear base material (42CrMo) was preheated for 25 minutes to reduce thermal cracking and improve the bonding strength between the cladding layer and the base.

[0046] Step 3: Section repair Step 3 is implemented as follows: Step 3.1: Laser cladding repair. Laser cladding technology was used to repair the broken tooth. The laser power was set to 1200W, the scanning speed was 8mm / s, the powder feed rate was controlled at 14g / min, and the cladding layer thickness was 1mm. Argon was used as the shielding gas at a flow rate of 16 L / min to ensure stability during the cladding process and prevent oxidation and porosity. During the cladding process, eight scans were performed based on the actual dimensions of the gear, with layers gradually accumulated to ensure a uniform and dense repair layer.

[0047] Step 3.2: Post-laser cladding heat treatment. Using a quenching and tempering process, heat the repaired gear to 850°C, hold for 30 minutes, and then quickly quench in an oil bath. After quenching, hold for another 3 hours to improve the hardness and fatigue resistance of the repaired layer. After heat treatment, the gear surface hardness should reach HRC 55.

[0048] Step 3.3: Post-Processing and Finishing: After heat treatment, the repaired area undergoes CNC precision machining to ensure a smooth interface between the repair layer and the substrate, with the required accuracy. After machining, grinding is performed to a roughness of Ra 0.5μm to ensure tooth surface flatness and proper contact patching. Furthermore, an X-ray inspection is performed on the repaired area to check for cracks or voids in the repair layer, ensuring that the repair meets quality standards.

[0049] Step 4: Heat treatment and performance optimization Step 4 is implemented as follows: Step 4.1 Pretreatment before heat treatment: First, the repaired area is further refined through CNC machining to ensure a smooth surface and dimensional accuracy. Next, the gear is uniformly heated to 250°C for 30 minutes to eliminate stress and prevent cracks during the heat treatment. During the preheating process, an electric furnace is used to ensure a uniform heating rate and avoid rapid temperature fluctuations.

[0050] Step 4.2: Quenching: Heat the gear to 850°C and hold for 40 minutes to ensure full austenitization of the repair layer and the substrate. Then, quickly immerse the gear in an oil bath for quenching, controlling the cooling rate to 20°C / min to avoid excessive internal stress. After quenching, the gear surface hardness can reach HRC 55, meeting high load and wear resistance requirements.

[0051] Step 4.3: Tempering. After quenching, tempering is performed to reduce the material's brittleness and optimize its mechanical properties. Heat the gear to 300°C and maintain this temperature for 3 hours, then cool naturally to room temperature. Tempering improves the gear's overall mechanical properties, enhancing its toughness and fatigue resistance, ensuring that the repaired gear can withstand repeated loads without failure in actual operation.

[0052] Example 5 Heavy equipment gear fracture repair method based on laser cladding technology Step 1: Obtaining the broken tooth surface profile Step 1 is implemented as follows: Step 1.1: Ultrasonic clean the gears using ethyl acetate for 10 minutes to completely remove grease, dust, and other contaminants from the gear surfaces. Place the cleaned gears in a drying oven at 40°C for 20 minutes to ensure no residual moisture.

[0053] Step 1.2: Selection and calibration of cross-sectional scanning equipment. A high-resolution CT scanner (GE VTomex M 240) was selected and calibrated using a standard calibration plate (200 mm × 200 mm × 50 mm) to ensure that the scanner calibration error was less than ±0.01 mm.

[0054] Step 1.3 Scan the broken tooth. Select CT scanning, using a 50μm slice resolution and a scanning time of 35 minutes. Ensure that each layer of data accurately reconstructs the gear's internal structure and surface morphology. Scan a 5mm area around the broken tooth to include any damage or defects on the tooth surface.

[0055] Step 1.4 Data Processing and Section Reconstruction. Import the scanned point cloud data into the specialized MeshLab software for processing. Use the software's 3D reconstruction algorithm to convert the point cloud data into a 3D geometric model. Reconstruct the 3D model using tomographic reconstruction techniques. The reconstructed 3D model should have an accuracy of 0.1 mm and accurately reflect the geometry of the fractured tooth. Save the generated 3D model in STEP format for subsequent restoration and processing.

[0056] Step 2: Preparation for Broken Tooth Repair Step 2 is implemented as follows: Step 2.1: Clean the gear surface with isopropyl alcohol (IPA) for 15 minutes. Then, sandblast with aluminum oxide (90-mesh grit) at a pressure of 0.4 MPa. For stubborn oil stains, degrease with acetone (CH₃COCH₃) and wipe clean with anhydrous ethanol. If any surface defects remain, regrind with a 600# grit SiC grinding wheel, controlling the grinding feed to 0.02 mm / pass and achieving a roughness of Ra 0.9 μm.

[0057] Step 2.2: Geometric Repair and Optimization. Based on the scanned tooth profile, finite element analysis (FEM) was used to repair the broken tooth defect area and optimize the repair path. Ni60A nickel-based alloy powder (80 μm particle size) was used as the repair material, with a cladding thickness of 1.5 mm to ensure excellent wear resistance and fatigue strength of the repaired tooth surface. A TiC reinforced coating was applied to the repaired area using plasma spraying (APS) technology with a coating thickness of 0.3 mm. The gear substrate, 42CrMo, was preheated for 20 minutes to reduce thermal cracking and improve the bond strength between the cladding layer and the substrate.

[0058] Step 3: Section repair Step 3 is implemented as follows: Step 3.1: Laser cladding repair. Laser cladding technology was used to repair the broken tooth. The laser power was set to 1400W, the scanning speed was 9mm / s, the powder feed rate was controlled at 15g / min, and the cladding layer thickness was 1.5mm. Argon was used as the shielding gas at a flow rate of 18L / min to ensure stability during the cladding process and avoid oxidation and porosity. During the cladding process, six scans were performed based on the actual dimensions of the gear, with layers gradually accumulated to ensure a uniform and dense repair layer.

[0059] Step 3.2: Post-laser cladding heat treatment. Using a quenching and tempering process, heat the repaired gear to 860°C, hold for 45 minutes, and then quickly quench in an oil bath. After quenching, hold for another 4 hours to improve the hardness and fatigue resistance of the repaired layer. After heat treatment, the gear surface hardness should reach HRC 60.

[0060] Step 3.3: Post-processing and finishing. After heat treatment, the repaired area is ground with a grinding wheel to ensure a smooth interface between the repair layer and the substrate and meet the required precision. After processing, grinding is performed using a roughness requirement of Ra 0.6μm to ensure tooth surface flatness and proper contact patching. Furthermore, ultrasonic testing is performed on the repaired area to check for cracks or voids in the repair layer to ensure that the repair meets quality standards.

[0061] Step 4: Heat treatment and performance optimization Step 4 is implemented as follows: Step 4.1 Pretreatment before heat treatment: First, CNC machining is used to further refine the repaired area to ensure a smooth surface and dimensional accuracy. Next, the gear is uniformly heated to 280°C for 40 minutes to eliminate stress and prevent cracks during the heat treatment. During the preheating process, an electric furnace or atmosphere furnace is used to ensure a uniform heating rate and avoid rapid temperature fluctuations.

[0062] Step 4.2: Quenching: Heat the gear to 850°C and hold for 45 minutes to ensure full austenitization of the repair layer and the substrate. Then, quickly immerse the gear in an oil bath for quenching, controlling the cooling rate to 24°C / min to avoid excessive internal stress. After quenching, the gear surface hardness can reach HRC 60, meeting high load and wear resistance requirements.

[0063] Step 4.3: Tempering. After quenching, tempering is performed to reduce the material's brittleness and optimize its mechanical properties. Heat the gear to 360°C and maintain this temperature for 2 hours, then cool naturally to room temperature. Tempering improves the gear's overall mechanical properties, enhancing its toughness and fatigue resistance, ensuring that the repaired gear can withstand repeated loads without failure in actual operation.

[0064] Example 6 Repair method of broken teeth of mining machine gear set based on laser cladding technology Step 1: Obtaining the broken tooth surface profile Step 1 is implemented as follows: Step 1.1: Ultrasonic clean the gears using a 50% isopropyl alcohol (IPA) solution for 20 minutes to completely remove grease, dust, and other contaminants from the gear surfaces. Dry the cleaned gears in a drying oven at 40°C for 20 minutes to ensure no residual moisture. Use either a 50% isopropyl alcohol (IPA) solution or an ethyl acetate solution.

[0065] Step 1.2: Select and calibrate the cross-sectional scanning equipment. A high-resolution CT scanner, the GE vtomex M 240, was selected. The equipment was calibrated using a standard calibration plate (200 mm × 200 mm × 50 mm) to ensure that the calibration error of the scanner was less than ±0.01 mm.

[0066] Step 1.3 Scan the broken tooth. Select CT scanning, using a 50μm slice resolution and a 45-minute scan time. Ensure that each slice accurately reconstructs the gear's internal structure and surface morphology. Scan a 5mm area around the broken tooth to ensure that any damage or defects are included.

[0067] Step 1.4 Data Processing and Section Reconstruction. Import the scanned point cloud data into the professional software Geomagic Design X for processing. Use the software's 3D reconstruction algorithm to convert the point cloud data into a 3D geometric model. Using tomographic reconstruction techniques, the reconstructed 3D model should have an accuracy of 0.1 mm and accurately reflect the geometry of the fractured tooth. Save the generated 3D model in IGES format for subsequent restoration and processing.

[0068] Step 2: Preparation for Broken Tooth Repair Step 2 is implemented as follows: Step 2.1: Clean the gear surface with acetone (CH3COCH3) for 18 minutes. Then, sandblast with aluminum oxide (100-mesh grit) at a pressure of 0.5 MPa. For stubborn oil stains, degrease with trichloroethylene (C2HCl3) and wipe clean with anhydrous ethanol. If any surface defects remain, refinish them using CNC precision milling to a roughness of Ra 0.8–1.2 μm.

[0069] Step 2.2: Geometric Repair and Optimization. Based on the scanned tooth profile, finite element analysis (FEM) was used to repair the broken tooth defect area and optimize the repair path. Ni60A nickel-based alloy powder (particle size 80 μm) was used as the repair material, with a cladding thickness of 2 mm to ensure excellent wear resistance and fatigue strength of the repaired tooth surface. A MoS2 reinforcement coating with a thickness of 0.3 mm was applied to the repaired area using plasma spraying (APS). The gear substrate material, 18CrNiMo7-6, was preheated for 20 minutes to reduce thermal cracking and improve the bond strength between the cladding layer and the substrate.

[0070] Step 3: Section repair Step 3 is implemented as follows: Step 3.1: Laser cladding repair. Laser cladding technology was used to repair the broken tooth. The laser power was set to 1300W, the scanning speed was 9mm / s, the powder feed rate was controlled at 16g / min, and the cladding layer thickness was 2.0mm. Argon was used as the shielding gas at a flow rate of 18 L / min to ensure stability during the cladding process and avoid oxidation and porosity. During the cladding process, 10 scans were performed based on the actual dimensions of the gear, with layers gradually accumulated to ensure a uniform and dense repair layer.

[0071] Step 3.2: Post-laser cladding heat treatment. Using a quenching and tempering process, heat the repaired gear to 850°C, hold it for 40 minutes, and then quickly quench it in an oil bath. After quenching, hold it for another 4 hours to improve the hardness and fatigue resistance of the repaired layer. After heat treatment, the gear surface hardness should reach HRC 60.

[0072] Step 3.3: Post-processing and finishing. After heat treatment, the repaired area is ground with a grinding wheel to ensure a smooth interface between the repair layer and the substrate and meet the required precision. After processing, grinding is performed using a roughness requirement of Ra 0.6μm to ensure tooth surface flatness and proper contact patching. Furthermore, an X-ray inspection is performed on the repaired area to check for cracks or voids in the repair layer to ensure that the repair meets quality standards.

[0073] Step 4: Heat treatment and performance optimization Step 4 is implemented as follows: Step 4.1 Pretreatment before heat treatment: First, CNC machining is used to further refine the repaired area to ensure a smooth surface and dimensional accuracy. Next, the gear is uniformly heated to 280°C for 40 minutes to eliminate stress and prevent cracks during the heat treatment. During the preheating process, an electric furnace or a heating system is used to ensure a uniform heating rate and avoid sudden temperature fluctuations.

[0074] Step 4.2: Quenching: Heat the gear to 860°C and hold for 40 minutes to ensure full austenitization of the repair layer and the substrate. Then, quickly immerse the gear in an oil bath for quenching, controlling the cooling rate to 26°C / min to avoid excessive internal stress. After quenching, the gear surface hardness can reach HRC 60, meeting high load and wear resistance requirements.

[0075] Step 4.3: Tempering. After quenching, tempering is performed to reduce the material's brittleness and optimize its mechanical properties. Heat the gear to 360°C and maintain this temperature for 3 hours, then cool naturally to room temperature. Tempering improves the gear's overall mechanical properties, enhancing its toughness and fatigue resistance, ensuring that the repaired gear can withstand repeated loads without failure in actual operation.

Claims

1. A broken tooth repair method based on laser cladding technology, characterized in that: Please follow the steps below to implement it: Step 1: Obtain the broken tooth surface profile; Step 2: Preparation for broken tooth repair; Step 3: Section repair; Step 4: Heat treatment and performance optimization.

2. The broken tooth repair method based on laser cladding technology according to claim 1 is characterized in that: The step 1 is specifically implemented according to the following steps: Step 1.1: Ultrasonic clean the gears for 10-30 minutes to ensure that the gear surfaces are completely free of grease, dust, and other contaminants. Dry the cleaned gears at 30-40°C for 15-20 minutes to ensure that no moisture remains. Step 1.2, cross-sectional scanning and calibration: Based on the size of the gear and the shape of the broken teeth, a high-resolution CT scanner and a standard calibration plate are used to scan and calibrate the equipment to ensure scanning accuracy. The calibration error of the scanner is less than ±0.01 mm. Step 1.

3. Scan the broken tooth area: For CT scanning, use slice scanning with a resolution of 50μm and a scanning time of 30-50 minutes to ensure that each layer of data can accurately reconstruct the internal structure and surface morphology of the gear. For laser scanning, use continuous scanning mode, and control the spacing between each measurement point within 0.2mm. Scan at least 5mm around the broken tooth to ensure that the tooth surface damage and defects are included. Step 1.4: Data processing and cross-section reconstruction.

3. The broken tooth repair method based on laser cladding technology according to claim 2 is characterized in that: The step 1.4 is as follows: Step 1.4.

1. Data import and preprocessing: The scanned point cloud data was imported into 3D processing software and preprocessed. The preprocessing included: for laser scanning data, noise removal and outlier filtering were performed, and the iterative closest point (ICP) algorithm was used for multi-view point cloud stitching to ensure a stitching error of ≤0.03mm. For CT scan data, the threshold segmentation method was used to remove metal artifacts, and the broken tooth area was extracted using the region growing algorithm. The grayscale threshold range was set to 2000-3000HU. Step 1.4.2, 3D geometric model reconstruction: For laser scanning data, Delaunay triangulation was used for surface reconstruction, with the maximum triangle side length set to ≤0.05 mm, the curvature sampling angle set to 15°, and the sharp edge protection mode enabled to ensure the accuracy of broken tooth edges. For CT scanning data, the FDK back-projection algorithm was used for tomographic reconstruction, with a slice thickness of ≤0.1 mm. 3D models were generated by isosurface extraction, with a threshold error set to <0.03 mm. Step 1.4.3, model optimization and accuracy verification: Perform mesh diagnosis to ensure that the number of non-manifold edges is ≤10 and there are no self-intersecting surfaces. Use 3D comparison tools to verify the deviation between the model and the original point cloud, and control the tolerance range within ±0.05mm. Take at least five section lines at key locations on the tooth surface for comparison to ensure that the overall dimensional error is ≤±0.08mm and the local feature error is ≤±0.05mm. Step 1.4.

4. Model output Save the optimized 3D model as a standard format file, including: STL format (binary), with the number of triangles controlled between 500,000 and 1,000,000, and the chord height tolerance set to 0.01mm; STEP or IGES format, ensuring that complete entity information is included.

4. The broken tooth repair method based on laser cladding technology according to claim 3 is characterized in that: The step 2 is specifically implemented according to the following steps: Step 2.

1. Clean the gear surface with a cleaning agent: the cleaning agent is isopropyl alcohol (IPA) or acetone (CH3COCH3), and the cleaning time is 10-20 minutes. Then, use alumina with a particle size of 80-120 mesh for sandblasting, and the spray pressure is 0.4-0.6 MPa. For stubborn oil stains, use trichloroethylene (C2HCl3) or acetone (CH3COCH3) for degreasing. After cleaning, wipe it clean with anhydrous ethanol. If there are still defects on the surface, use CNC precision milling or grinding wheel grinding for finishing, and control the grinding feed rate to 0.01-0.02 mm / time, and the roughness reaches Ra 0.8-1.2 μm. Step 2.2, geometric shape repair and optimization: Based on the broken tooth surface contour obtained by scanning, the broken tooth defect area is repaired using the finite element analysis method FEM.

5. The broken tooth repair method based on laser cladding technology according to claim 4 is characterized in that: The step 2.2 is specifically implemented according to the following steps: The scanned 3D model of the broken tooth was imported into finite element analysis software, compared with a standard gear model, and the boundaries of the defect area were extracted to establish a parameterized defect model. After setting the mechanical parameters of the base material and the Ni60A cladding layer, a stress analysis was performed by applying 1.5 times the rated load to identify high-stress areas. A topology optimization method was used to generate the optimal restoration shape with stiffness and strength as optimization targets, and a layered cladding scheme was formulated, including a 0.2mm layer height, a 0.8-1.2mm path spacing, and a cross-scanning process in high-stress areas. The preheating temperature was controlled at 200±10°C and the interlayer temperature was ≤150°C. By verifying the stress distribution and fatigue performance of the restoration, a 3D model and processing path were output, which reduced the weight of the restoration by 20-35%, reduced the stress concentration factor to below 1.2, and achieved a service life of more than 85% of that of a new tooth. The repair path was optimized. The repair material used was Ni60A nickel-based alloy powder with a particle size of 50-150 μm and a cladding thickness of 1.0-2.0 mm to ensure that the repaired tooth surface had good wear resistance and fatigue strength. On the surface of the repaired area, a MoS2 or TiC reinforcement coating was applied using plasma spraying APS technology with a coating thickness of 0.2-0.3 mm. The gear base material was preheated for 20-30 minutes to reduce the occurrence of thermal cracks and improve the bonding strength between the cladding layer and the base material.

6. The broken tooth repair method based on laser cladding technology according to claim 5, characterized in that: The step 3 is specifically implemented according to the following steps: Step 3.1, laser cladding repair: Use laser cladding technology to repair broken teeth. The laser power is set to 1000-1500 W, the scanning speed is 6-10 mm / s, the powder feed rate is controlled at 12-18 g / min, the cladding layer thickness is 1.0-2.0 mm, and the protective gas is argon with a gas flow rate of 15-20 L / min to ensure stability during the cladding process and avoid oxidation and the formation of pores. During the cladding process, 5-10 scans are performed according to the actual size of the gear, and the layers are gradually accumulated to ensure that the repair layer is uniform and dense. Step 3.2: Heat treatment after laser cladding: Using a quenching and tempering process, heat the repaired gear to 850-900°C, hold for 30-60 minutes, and then quickly quench it in an oil bath. After quenching, hold for another 3-4 hours to improve the hardness and fatigue resistance of the repair layer. After heat treatment, the surface hardness of the gear reaches HRC 55-60. Step 3.3, subsequent processing and finishing: After heat treatment, the repair area is subjected to CNC precision machining or grinding to ensure that the interface between the repair layer and the substrate is smooth and the accuracy meets the requirements. After machining, it is ground with a roughness requirement of Ra 0.4~0.8μm to ensure the flatness of the tooth surface and appropriate contact spots. In addition, the repaired area is subjected to non-destructive testing to check whether there are cracks or voids in the repair layer to ensure that the repair quality meets the standards.

7. The broken tooth repair method based on laser cladding technology according to claim 6, characterized in that: The precision machining process in step 3.3 includes: a rough machining stage: using a φ6mm carbide end mill, a rotation speed of 8000r / min, a feed speed of 1500mm / min, a cutting depth of 0.5mm, and removing the cladding layer allowance; a semi-finishing stage: replacing a φ4mm ball end mill, a rotation speed of 12000r / min, a feed speed of 800mm / min, and a cutting depth of 0.2mm; a finishing stage: using a φ2mm diamond-coated milling cutter, a rotation speed of 15000r / min, a feed speed of 500mm / min, and a cutting depth of 0.05mm, and finally achieving a surface roughness of Ra0.8μm; When processing the repair layer with hardness greater than 50HRC, a precision grinding process is adopted. The processing process includes: rough grinding stage: using 80# white corundum grinding wheel, linear speed 35m / s, feed speed 0.1mm / pass, grinding depth 0.02mm; fine grinding stage: replacing 240# CBN grinding wheel, linear speed 45m / s, feed speed 0.05mm / pass, grinding depth 0.005mm; finishing stage: using 800# diamond grinding wheel for polishing, and the surface roughness is controlled within Ra0.4μm.

8. The broken tooth repair method based on laser cladding technology according to claim 7, characterized in that: The step 4 is specifically implemented according to the following steps: Step 4.1, pretreatment before heat treatment: First, the repair area is further refined by computer numerical control (CNC) machining, specifically including: rough machining with a φ6mm carbide end mill, speed 6000-8000r / min, feed 800-1200mm / min, leaving a 0.2mm margin, followed by semi-finishing with a φ4mm ball end mill, speed 10000-12000r / min, feed 500-800mm / min, and finally finishing with a φ4mm ball end mill. Finish machining is performed using a φ2mm diamond-coated milling cutter at a speed of 15,000-18,000 rpm and a feed rate of 300-500 mm / min, ensuring a surface roughness of Ra0.8 μm and a profile accuracy of ±0.02 mm. Ultrasonic cleaning and acetone wiping are used after machining to provide a qualified surface for heat treatment. The gears are then uniformly heated to 250-300°C and held at this temperature for 30-60 minutes to eliminate stress and avoid cracks during the heat treatment process. Step 4.2, quenching treatment: Heat the gear to 850-900℃ and keep it warm for 30-60 minutes to ensure that the repair layer and the matrix are fully austenitized. Then, quickly immerse the gear in an oil bath for quenching. The cooling rate is controlled at 20-30℃ / min. The surface hardness of the gear after quenching reaches HRC 55-60, which meets the requirements of high load and wear resistance. Step 4.3 Tempering: After quenching, tempering treatment is performed to reduce the brittleness of the material and optimize its mechanical properties. Heat the gear to 300-400℃ and maintain the temperature for 2-4h, then cool it naturally to room temperature.

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