A process for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring

Abstract

This invention belongs to the field of materials surface engineering technology, specifically relating to a process method for preparing a wear-resistant layer on the sealing surface of a turbine rotor carbon ring. The method employs laser cladding technology to apply high-hardness alloy powder to the sealing position of the turbine rotor carbon ring, forming a high-quality, high-hardness cladding layer free of metallurgical defects. The laser cladding power is 2000–2600 W, the circular spot size is 4.5–5 mm, the overlap rate is 40%–50%, the cladding speed is 8–10 mm / s, the protective gas and powder feeding gas are pure argon, the protective gas flow rate is 5–8 L / min, the powder feeder speed is 1–1.2 r / min, and the powder feeder flow rate is 6–7 L / min. This invention can prepare a high-hardness wear-resistant layer at the sealing position of a turbine rotor carbon ring. The wear-resistant layer is metallurgically bonded to the substrate, with a fine structure free of pores, cracks, inclusions, and other defects. The heat input during the cladding process is small, and the deformation of the rotor is adjustable and controllable, preventing excessive rotor runout or even bending.

Description

Technical Field

[0001] This invention belongs to the field of materials surface engineering technology, specifically relating to a process method for preparing a wear-resistant layer on the carbon ring sealing surface of a steam turbine rotor. This method is used to prepare a high-hardness wear-resistant layer on the carbon ring sealing surface of a small self-contained generator steam turbine rotor. Background Technology

[0002] A steam turbine is a thermodynamic machine that drives mechanical equipment through high-speed rotating turbine blades. It converts thermal energy into mechanical energy through the principle of thermodynamic cycle, and features high efficiency, energy saving, stability, reliability, long service life, and environmental friendliness. Besides dedicated large-scale thermal or nuclear power plants, many enterprises have their own steam turbines of varying specifications for mechanical power output or power generation.

[0003] Aside from maintenance periods, steam turbines are continuously operating moving equipment, 24 hours a day. Friction damage is inevitable at various mating points of the turbine rotor, such as bearing mating points and carbon ring mating points. Generally, the steel used for turbine rotors is used in a quenched and tempered state, resulting in relatively low hardness. Although some manufacturers take preventative measures against potential wear, most employ thermal spraying technology for protection. However, the thermal spray coating is physically bonded to the substrate, resulting in lower bonding strength and a risk of detachment during use. Minor wear can be corrected with appropriate polishing and continued use, while more severe wear will affect the normal operation of the unit. For rotor damage that is severe enough to affect the unit's normal production operation, selecting a non-destructive repair and remanufacturing method is crucial. Summary of the Invention

[0004] To address the wear issues affecting the normal operation of steam turbine rotors at corresponding mating locations, as well as problems such as rotor deformation, excessive welding stress, welding surfacing techniques, and heat-affected zone cracks that may occur with traditional welding processes, this invention provides a process for preparing a wear-resistant layer on the carbon ring sealing surface of a steam turbine rotor. The process employs laser cladding with suitable alloy powder to prepare a wear-resistant layer that is metallurgically bonded to the substrate at the wear-prone mating locations of the steam turbine rotor. The wear-resistant layer is free of pores, cracks, and inclusions, and its hardness exceeds HRC55.

[0005] The technical solution of the present invention is as follows:

[0006] A process for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring, the method employing laser cladding technology to apply high-hardness alloy powder to the sealing position of the steam turbine rotor carbon ring, forming a high-quality, high-hardness cladding layer free of metallurgical defects, specifically including the following steps:

[0007] (1) Cleaning and dimensional measurement: Clean the surface dirt, check the damage of the repaired part, measure and record the outer diameter of the damaged and undamaged parts of the repaired part.

[0008] (2) Runout check: Using the bearing bushes at both ends as a reference, check and record the runout of the rotor journal to confirm that the rotor is not bent.

[0009] (3) Remove the original coating by turning. The turning amount is 0.1 mm each time. When the composition of the turned part is consistent with the composition of the spindle material, a penetrant test is performed. If cracks are found, turn is continued until no cracks are found.

[0010] (4) Rotor laser cladding: Fix the rotor on the cladding machine and then adjust the rotor's runout so that the runout of the repaired part is within 0.1mm; the laser cladding power is 2000-2600W, the circular spot size is 4.5-5mm, the overlap rate is 40%-50%, the cladding speed is 8-10mm / s, the protective gas is pure argon, the protective gas flow rate is 5-8L / min, the powder feeder speed is 1-1.2r / min, the powder feeding gas is pure argon, and the powder feeder flow rate is 6-7L / min;

[0011] (5) Penetrant testing: After the repair area cools to room temperature, penetrant testing is performed on the repair location using the dye penetrant method. The test results are recorded. If defects are found, they need to be ground off and repaired by welding.

[0012] (6) Turning treatment: The repair is precision machined and ground according to the drawing requirements;

[0013] (7) Dye penetrant testing: The carbon ring sealing position after processing shall be subjected to dye penetrant testing again, and there shall be no metallurgical defects.

[0014] (8) Dynamic balancing: The repaired rotor is dynamically balanced to achieve the corresponding grade;

[0015] (9) Inspection: Check the dimensions of the repaired parts according to the drawings and record the results.

[0016] The process for preparing the wear-resistant layer on the carbon ring sealing surface of a steam turbine rotor is described above. The steam turbine rotor is a small steam turbine rotor for self-generating power, and its material is forged steel.

[0017] The process for preparing the wear-resistant layer on the carbon ring sealing surface of a steam turbine rotor requires drying the metal powder before laser cladding at a temperature of 100–120°C.

[0018] The process for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring uses an iron-based alloy powder for laser cladding. The powder's chemical composition, by weight percentage, is: C 0.2-0.36, Cr 18-18.5, Si 0.8-1.1, Ni 2.0-2.5, with Fe as the balance.

[0019] The process for preparing the wear-resistant layer on the carbon ring sealing surface of a steam turbine rotor involves preheating the repair area with flame before laser cladding, with a preheating temperature of not less than 150°C.

[0020] The process for preparing the wear-resistant layer on the carbon ring sealing surface of a steam turbine rotor, wherein the equipment used for testing the chemical composition of the machined part is a handheld XRF spectrometer.

[0021] The design concept of this invention is:

[0022] This invention employs automated laser cladding additive manufacturing technology. By adding cladding material to the surface of a substrate, a high-energy-density laser beam melts and bonds the cladding powder to a thin layer on the substrate surface. The laser cladding layer and the substrate are metallurgically bonded, with a bonding strength of no less than 90% of the original substrate material. During laser processing, the substrate material undergoes micro-melting, with a micro-melted layer of only 0.05–0.1 mm. The heat-affected zone of the substrate is extremely small, typically 0.1–0.2 mm. The combination of a robotic arm and laser cladding allows for control of the size and speed of the molten pool based on the substrate and powder materials, ensuring optimal cladding speed and layer thickness. This allows the alloy metal to be metallurgically bonded to the substrate with minimal heat transfer and dilution. Furthermore, the use of argon gas with a volume purity of over 99% as an inert gas for protection significantly reduces cladding defects. The repaired equipment can operate stably and meet the requirements for normal equipment use.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. This invention uses optimized process parameters and alloy powder to prepare a high-hardness wear-resistant layer at the carbon ring sealing position of a steam turbine rotor. The wear-resistant layer has a thickness greater than 1.5 mm, a hardness greater than HRC55, and excellent wear resistance.

[0025] 2. The wear-resistant layer of this invention is metallurgically bonded to the base material. The wear-resistant layer has a fine structure and is free from defects such as pores, cracks, and inclusions. Actual user feedback is positive.

[0026] 3. The heat input during the cladding process of this invention is small, and the deformation of the rotor is adjustable and controllable, preventing excessive rotor vibration or even bending.

[0027] 4. The cladding process of this invention is a fully automated process with minimal human intervention, and can be widely promoted.

[0028] 5. This invention can repair the carbon ring seal in a timely and effective manner, ensuring the company's rapid resumption of production and solving the cost incurred by replacing a large number of equipment. Attached Figure Description

[0029] Figure 1 A photograph of a steam turbine rotor that is to be laser clad.

[0030] Figure 2 This is a photograph of a steam turbine rotor used in laser cladding.

[0031] Figure 3 This is a metallographic diagram of the wear-resistant layer after laser cladding. Detailed Implementation

[0032] In its specific implementation, this invention proposes a process for preparing a wear-resistant layer on the sealing surface of a turbine rotor carbon ring. This method utilizes laser cladding technology to clad highly alloyed metal powder onto the sealing position of the turbine rotor carbon ring, forming a high-hardness wear-resistant layer. The specific steps are as follows:

[0033] (1) Cleaning and dimensional measurement: Clean the surface dirt, check the damage of the repair area, measure and record the outer diameter of the damaged and undamaged parts of the repair area. (2) Runout check: Use the bearing bushes at both ends as a reference to check the runout of the rotor journal and record it to confirm that the rotor is not bent. (3) Turning to remove the original coating: Turn the material in increments of 0.1 mm. After the composition of the turned part is consistent with the composition of the spindle material, perform penetrant testing. If cracks are found, continue turning until no cracks are found. (4) Laser cladding: Fix the rotor on the cladding machine and then adjust the runout of the rotor to keep the runout of the repair area within 0.1 mm. Before cladding, the metal powder must be dried. The powder used for cladding is iron-based alloy powder. Before cladding, the repair area should be preheated by flame preheating at a temperature not lower than 150°C. Sufficient machining allowance should be left after cladding. (5) Dye penetrant testing: Use the PT method to perform penetrant testing on the repaired area and record the results. If defects such as porosity or cracks are found, they need to be removed by grinding and then re-welded for repair. (6) Finishing and grinding (polishing): Perform finishing and grinding (polishing) treatment on the repaired area according to the drawing requirements. (7) Dye penetrant testing: Perform penetrant testing again on the processed carbon ring seal area. There must be no metallurgical defects. (8) Dynamic balancing: Perform dynamic balancing treatment on the repaired rotor to achieve the corresponding grade. (9) Inspection: Perform dimensional inspection on the repaired area according to the drawing and record the results.

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0035] Example 1:

[0036] like Figure 1 As shown, the carbon ring seal of a 2DYRPE3Ⅲ steam turbine rotor manufactured by ELLIOTT GROUP, a chemical company in Zhejiang Province, has suffered severe wear, affecting the normal operation of the unit. Figure 2 As shown, the wear area was repaired by laser cladding using the present invention, and everything is working well after the repair.

[0037] The specific steps of this embodiment are as follows:

[0038] (1) Clean and measure the dimensions of the rotor. Use a cleaning agent to clean the oil stains in the repair area and use a steel wool to clean the rust in the blade area. Use an outside micrometer to measure and record the outer diameter of the wear area.

[0039] (2) Support the V-shaped iron at the bearing positions at both ends of the rotor, detect and record the rotor journal runout, and confirm that the rotor is not bent.

[0040] (3) The original spray coating was removed by turning on a horizontal lathe. The original rotor carbon ring seal was prepared with a protective coating by thermal spraying. If it is not turned cleanly, it will affect the bonding strength between the laser cladding layer and the substrate. The turning amount was 0.1 mm each time. The composition of the carbon ring seal was detected by a handheld XRF spectrometer until the chemical composition was consistent with the composition of the spindle material.

[0041] (4) Perform PT flaw detection on the machined parts. If cracks or defects are found, continue machining until no cracks are found.

[0042] (5) Laser cladding: The rotor is fixed on the cladding machine, and the rotor's runout is adjusted to ensure the runout of the repair area is within 0.1 mm. The cladding powder is an iron-based alloy powder with the following chemical composition (by weight percentage): C 0.27, Cr 18.35, Si 0.91, Ni 2.16, Fe balance. Before cladding, the powder must be dried at 110℃ for 1 hour; the repair area is preheated by flame at 160℃. The laser cladding power is 2300W, the circular spot size is 4.5mm, the overlap rate is 45%, and the cladding speed is 8mm / s. Argon gas with a volume purity of 99.9% is used for both the protective gas and the powder feeding gas. The protective gas flow rate is 6L / min, the powder feeder speed is 1r / min, and the powder feeder flow rate is 6.7L / min.

[0043] (6) The repair location after cladding should be at least Φ166.5mm in size.

[0044] (7) Dyeing flaw detection: After cooling to room temperature, use the PT method to perform penetrant testing on the repaired area. There must be no defects such as pores or cracks.

[0045] (8) Finishing and grinding (polishing) treatment: According to the drawing requirements, the repair is finished and ground (polished) to the size required by the drawing φ165+0.11+0.09mm, and the surface finish Ra0.8μm.

[0046] (9) Dyeing flaw detection: Dyeing flaw detection is performed on the repaired mechanical seal, and the flaw detection results are recorded. There must be no defects such as pores or cracks.

[0047] (10) Inspection: Check the dimensions of the repaired parts according to the drawings and record the results.

[0048] like Figure 3 As shown in the figure, the metallographic structure of the wear-resistant layer after laser cladding reveals that the wear-resistant layer and the substrate material are metallurgically bonded, and the wear-resistant layer has a uniform and dense structure. In this embodiment, a high-hardness wear-resistant layer was prepared at the carbon ring sealing position of the turbine rotor. The wear-resistant layer has a thickness of approximately 2.4 mm and a hardness of HRC68, exhibiting excellent wear resistance.

[0049] Example 2:

[0050] A company in Liaoning Province experienced coating peeling off at the carbon ring seal of its self-contained power turbine rotor, affecting the normal operation of the unit. This invention was used to repair the worn area using laser cladding, and the unit operated smoothly after the repair.

[0051] The specific steps of this embodiment are as follows:

[0052] (1) Clean and measure the dimensions of the rotor. Use a cleaning agent to clean the oil stains in the repair area and use a steel wool to clean the rust in the blade area. Use an outside micrometer to measure and record the outer diameter of the wear area.

[0053] (2) Support the V-shaped iron at the bearing positions at both ends of the rotor, detect and record the rotor journal runout, and confirm that the rotor is not bent.

[0054] (3) The original spray coating was removed by turning on a horizontal lathe. The original rotor carbon ring seal was prepared with a protective coating by thermal spraying. If it is not turned cleanly, it will affect the bonding strength between the laser cladding layer and the substrate. The turning amount was 0.1 mm each time. The composition of the carbon ring seal was detected by a handheld XRF spectrometer until the chemical composition was consistent with the composition of the spindle material.

[0055] (4) Perform PT flaw detection on the machined parts. If cracks or defects are found, continue machining until no cracks are found.

[0056] (5) Laser cladding: The rotor is fixed on the cladding machine, and the rotor's runout is adjusted to ensure the runout of the repair area is within 0.1 mm. The cladding powder is an iron-based alloy powder with the following chemical composition (by weight percentage): C 0.23, Cr 18.17, Si 1.04, Ni 2.09, Fe balance. Before cladding, the powder must be dried at 120℃ for 1 hour; the repair area is preheated by flame at 150℃. The laser cladding power is 2400W, the circular spot size is 4.8 mm, the overlap rate is 50%, and the cladding speed is 9 mm / s. Argon gas with a volume purity of 99.9% is used for both the protective gas and the powder feeding gas. The protective gas flow rate is 7 L / min, the powder feeder speed is 1.1 r / min, and the powder feeder flow rate is 6.3 L / min.

[0057] (6) The repair location after cladding should be at least Φ170mm in size.

[0058] (7) Dyeing flaw detection: After cooling to room temperature, use the PT method to perform penetrant testing on the repaired area. There must be no defects such as pores or cracks.

[0059] (8) Finishing and grinding (polishing) treatment: According to the drawing requirements, the repair is finished and ground (polished) to the size required by the drawing φ170+0.11+0.09mm, and the surface finish Ra0.8μm.

[0060] (9) Dyeing flaw detection: Dyeing flaw detection is performed on the repaired mechanical seal, and the flaw detection results are recorded. There must be no defects such as pores or cracks.

[0061] (10) Inspection: Check the dimensions of the repaired parts according to the drawings and record the results.

[0062] The metallographic structure of the wear-resistant layer after laser cladding shows that the wear-resistant layer and the substrate material are metallurgically bonded, and the wear-resistant layer has a uniform and dense structure. In this embodiment, a high-hardness wear-resistant layer was prepared at the carbon ring sealing position of the turbine rotor. The wear-resistant layer has a thickness of about 2 mm and a hardness of HRC57, exhibiting excellent wear resistance.

[0063] The results show that the present invention can prepare a high-hardness wear-resistant layer at the carbon ring sealing position of a steam turbine rotor. The wear-resistant layer is metallurgically bonded to the substrate, with a fine structure and no defects such as pores, cracks, or inclusions. The heat input during the cladding process is small, and the deformation of the rotor is adjustable and controllable, without causing excessive rotor runout or even bending.

Claims

1. A process for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring, characterized in that, This method employs laser cladding technology to apply high-hardness alloy powder to the carbon ring sealing position of a steam turbine rotor, forming a high-quality, high-hardness cladding layer free of metallurgical defects, with a hardness greater than HRC55. The specific steps include: (1) Cleaning and dimensional measurement: Clean the surface dirt, check the damage of the repaired part, measure and record the outer diameter of the damaged and undamaged parts of the repaired part; (2) Runout check: Using the bearing bushes at both ends as a reference, check and record the runout of the rotor journal to confirm that the rotor is not bent; (3) Remove the original coating by turning. The turning amount is 0.1 mm each time. When the composition of the turning part is consistent with the composition of the spindle material, a penetrant test is performed. If cracks are found, turn is continued until no cracks are found. (4) Rotor laser cladding: Fix the rotor on the cladding machine and then adjust the rotor to make the runout of the repaired part within 0.1mm; the laser cladding power is 2000~2600W, the circular spot size is 4.5~5mm, the overlap rate is 40%~50%, the cladding speed is 8~10mm / s, the protective gas is pure argon, the protective gas flow rate is 5~8L / min, the powder feeder speed is 1~1.2r / min, the powder feeding gas is pure argon, and the powder feeder flow rate is 6~7L / min; The powder used for laser cladding is an iron-based alloy powder. By weight percentage, the powder chemical composition is: C 0.2~0.36, Cr 18~18.5, Si 0.8~1.1, Ni 2.0~2.5, Fe balance; (5) Penetrant testing: After the repair area cools to room temperature, penetrant testing is performed on the repair location using the dye penetrant method. The test results are recorded. If defects are found, they need to be removed by grinding and then repaired by welding. (6) Turning treatment: The repair is precision machined and ground according to the drawing requirements; (7) Dye penetration testing: The carbon ring sealing position after processing shall be subjected to dye penetration testing again, and there shall be no metallurgical defects. (8) Dynamic balancing: The repaired rotor is dynamically balanced to achieve the corresponding grade; (9) Inspection: Check the dimensions of the repaired parts according to the drawings and record the results.

2. The process method for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring according to claim 1, characterized in that, The turbine rotor is a small, self-generating turbine rotor made of forged steel.

3. The process method for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring according to claim 1, characterized in that, Before laser cladding, the metal powder must be dried at a temperature of 100~120℃.

4. The process method for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring according to claim 1, characterized in that, Before laser cladding, the area to be repaired is preheated by flame preheating, with a preheating temperature of not less than 150℃.

5. The process method for preparing a wear-resistant layer on the sealing surface of a steam turbine rotor carbon ring according to claim 1, characterized in that, The equipment used for testing the chemical composition of the machined parts was a handheld XRF spectrometer.

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