A laser-based anti-corrosion and wear-resistant material and repair process for repairing impact turbines.

Abstract

This invention belongs to the field of metallic materials technology, and relates to a laser-based anti-corrosion and wear-resistant material and repair process for repairing impact turbines. The material comprises the following components by mass percentage: Cr: 10-20%; Co: 10-20%; Nd: 1.5-2.5%; Ni: 3-8%; C: 0.01-0.2%; Nb: 0.1-1%; W: 1-5%; V: 0.1-1%; Mo: 0.8-1.2%; Mn: ≤3%; Ti: 0.01-0.1%; N: 0.10-0.5%; Si: 0.1-0.2%; P: 0.01-0.05%; Fe: balance. The repair method of this invention shortens the labor time required for programming irregularly shaped sections, simplifies the complex programming process, and greatly improves production efficiency. After laser repair, the turbine was tested by flaw detection, hardness testing and actual operation testing, all of which proved that the material’s erosion resistance and corrosion resistance met the requirements for normal use. No cracks, cavitation, wear or missing material appeared again in the repaired area.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, and relates to a laser anti-corrosion and wear-resistant material and repair process for repairing impact turbines, particularly a laser material and repair process that is erosion-resistant, corrosion-resistant, and has superior cladding performance. Background Technology

[0002] The runner is the key core component of a hydraulic turbine. An impulse turbine uses a special guide vane mechanism to draw a kinetic jet of water that impacts the runner's buckets, causing the runner to rotate and perform work, thus converting water energy into mechanical energy. Impulse turbines are suitable for high-head, low-flow power stations. They convert water from a pressurized pipeline into a high-speed jet through nozzles, impacting the runner tangentially and driving its rotation, which in turn drives the generator rotor to generate electricity. Because the bucket surface of an impulse turbine is subjected to continuous water impact during operation, and given the varying water quality at different hydropower stations, cavitation, wear, chipping, and even cracks or breakage of the bucket surface frequently occur. Once cracks appear, operational imbalances occur, rendering the turbine unusable and requiring replacement. my country is a vast country with numerous rivers, and most of its hydroelectric power stations utilize this type of impulse turbine. Currently, most impulse turbines are subject to impact and corrosion from various water qualities, requiring replacement of over a thousand units annually. Therefore, in order to meet the requirements of power generation, the water buckets of the impulse turbine usually need to have increased surface hardness and wear resistance, making it necessary to repair the impulse turbine.

[0003] For damage to turbine buckets, common repair methods include metal repair fluid and arc welding. Metal repair fluid repair is a frequently used method due to its simplicity and convenience, allowing for localized repairs. However, because the repair fluid does not form a metallurgical bond with the substrate, its bonding strength is weak, and the significant impacts during operation can cause the repaired metal to peel off. Arc welding can restore dimensions by depositing a layer of corrosion-resistant and wear-resistant material, thus altering the surface properties of the bucket. However, this method has a large heat-affected zone, and large-area arc welding may cause deformation of the bucket structure, leading to cracks and affecting its long-term service life.

[0004] Based on the operating conditions and material characteristics of impulse turbines, selecting a wear-resistant and corrosion-resistant repair material to ensure minimal thermal deformation, extend service life, and prolong maintenance cycles is an urgent issue to be addressed. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a laser-based anti-corrosion and wear-resistant material and repair process for impulse turbines. This repair material enables the repair of the water buckets in impulse turbines, and the repair process is simple to operate, highly adaptable, exhibits minimal thermal deformation, and is highly standardized. The repaired impulse turbines can meet the requirements of various water qualities and operating conditions, significantly reducing maintenance costs.

[0006] A laser-coated corrosion-resistant and wear-resistant material for impulse turbines, comprising the following components by mass percentage:

[0007] Cr: 10~20%; Co: 10~20%; Nd: 1.5~2.5%; Ni: 3~8%; C: 0.01~0.2%; Nb: 0.1~1%; W: 1~5%; V: 0.1~1%; Mo: 0.8~1.2%; Mn: ≤3%; Ti: 0.01~0.1%; N: 0.10~0.5%; Si: 0.1~0.2%; P: 0.01~0.05%; Fe: balance.

[0008] The material provided in this invention is prepared through processes such as vacuum melting, vacuum atomization, and screening, and has a particle size of -100 to +200 mesh.

[0009] The cobalt-chromium alloy powder provided in this invention is suitable for various fiber lasers. The cladding process parameters for repairing the powder material are as follows: a 4KW-6KW continuous fiber laser and a fully automatic rotary fixture are used for laser cladding. The laser cladding parameters are: power 3000-5000W, light plate diameter 4-6mm, cladding thickness 0.5-1.2mm, and cladding speed 8-15mm / s.

[0010] A repair process for an impulse turbine specifically includes the following steps:

[0011] Step 1: Use a rangefinder to measure the height and low points on the object's surface, and record the changes in focal length based on the different height and low points;

[0012] Step 2: Use a laser scanner to scan the entire surface of the object, collect data changes based on the surface shape, collect tree structure data, and construct a water bucket model drawing; use software to analyze the drawing, combine different focal lengths measured by the rangefinder, and program them uniformly.

[0013] Step 3: The programming instructions are transmitted to the robotic arm, which then performs laser cladding according to the program;

[0014] Step 4: Perform non-destructive testing after laser cladding to check the surface quality after laser cladding;

[0015] Step 5: Grinding and polishing to improve the gloss of the water basin surface, grind the surface smooth, and round the edges to reduce the impact of water flow.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0017] 1. The alloy matrix strengthening elements, grain refiner, and grain boundary strengthening elements are added, and the percentage content of each element is adjusted. Through these strengthening methods, the alloy matrix is ​​enhanced, and the grain boundary quality is improved, resulting in excellent overall performance. This achieves the goal of providing the turbine bucket with good erosion resistance, corrosion resistance, high hardness, and good toughness, while maintaining process stability and compositional uniformity, thus meeting the corrosion and wear resistance requirements of laser cladding for turbines.

[0018] 2. The purpose of this invention is to provide a laser repair material with erosion resistance and corrosion resistance for repairing the working parts of water turbine buckets using a laser cladding process. This laser repair material improves the erosion resistance and corrosion resistance of the cladding area by adding a significant amount of Cr and Co, thereby enhancing its mechanical properties. In particular, the alloy matrix is ​​strengthened by adding at least one of W and Mo elements, and most importantly, the addition of the rare earth element Nd (neodymium) improves the high-temperature performance, airtightness, and corrosion resistance of the alloy material. This alloy material exhibits excellent erosion resistance, corrosion resistance, and high hardness, and is very stable, not easily deformed or affected by external environmental factors. It is also relatively inexpensive and can be widely used.

[0019] Co possesses high strength and high-temperature performance, can withstand high impact and vibration, and is not prone to fatigue damage; Cr has good resistance to chloride ion corrosion, which can improve the corrosion resistance of the processed surface, adapt to various harsh working environments, and has excellent resistance to pitting and crevice corrosion; Ni has good resistance to inorganic acid corrosion, as well as good machinability and weldability, and no cracking sensitivity after laser cladding. The addition of N, P, and Si elements refines the grain, promotes slag removal, improves performance, prevents cracking, and improves the bonding strength of laser cladding; Mn can replace some Ni, which can reduce costs and improve strength; the addition of other elements can improve the hardness, strength, and toughness of the material, and at temperatures above 40°C, it can exhibit excellent corrosion resistance in solutions of various concentrations of hydrochloric acid, sulfuric acid, etc.

[0020] 3. The repair method of the present invention shortens the labor time of programming irregular shapes segment by segment, simplifies the complex programming process, and greatly improves production efficiency.

[0021] 4. After laser repair, the turbine was tested by flaw detection, hardness testing and actual operation testing, which proved that the material’s erosion resistance and corrosion resistance met the requirements for normal use. No cracks, cavitation, wear, missing material or other damage reappeared at the repaired part.

[0022] 5. This method achieves wear-resistant and corrosion-resistant properties on the surface of the turbine runner and bucket. Moreover, the repair process is simple to operate, highly adaptable, and has minimal thermal deformation. The repaired turbine meets normal operating requirements, and its resistance to erosion and corrosion is significantly improved. This method has great value in reducing the maintenance costs of turbine equipment in small power plants in my country. Attached Figure Description

[0023] Figure 1 A schematic diagram of an impulse turbine.

[0024] Figure 2 Schematic diagram of a single turbine bucket.

[0025] Figure 3 Example 1: Transformation of 7mm crack damage before repair.

[0026] Figure 4 Example 1: Transformation of 12mm crack damage before repair.

[0027] Figure 5 Example 1: Water turbine bucket working face that has been used for 2 years after laser repair. Detailed Implementation

[0028] A laser-coated corrosion-resistant and wear-resistant material for impulse turbines, comprising the following components by mass percentage:

[0029] Cr: 10~20%; Co: 10~20%; Nd: 1.5~2.5%; Ni: 3~8%; C: 0.01~0.2%; Nb: 0.1~1%; W: 1~5%; V: 0.1~1%; Mo: 0.8~1.2%; Mn: ≤3%; Ti: 0.01~0.1%; N: 0.10~0.5%; Si: 0.1~0.2%; P: 0.01~0.05%; Fe: balance.

[0030] The material provided in this invention is prepared through processes such as vacuum melting, vacuum atomization, and screening, and has a particle size of -100 to +200 mesh.

[0031] The cobalt-chromium alloy powder provided in this invention is suitable for various fiber lasers. The cladding process parameters for repairing the powder material are as follows: a 4KW-6KW continuous fiber laser and a fully automatic rotary fixture are used for laser cladding. The laser cladding parameters are: power 3000-5000W, light plate diameter 4-6mm, cladding thickness 0.5-1.2mm, and cladding speed 8-15mm / s.

[0032] A repair process for an impulse turbine specifically includes the following steps:

[0033] Step 1: Use a rangefinder to measure the height and low points on the object's surface, and record the changes in focal length based on the different height and low points;

[0034] Step 2: Use a laser scanner to scan the entire surface of the object, collect data changes based on the surface shape, collect tree structure data, and construct a water bucket model drawing; use software to analyze the drawing, combine different focal lengths measured by the rangefinder, and program them uniformly.

[0035] Step 3: The programming instructions are transmitted to the robotic arm, which then performs laser cladding according to the program;

[0036] Step 4: Perform non-destructive testing after laser cladding to check the surface quality after laser cladding;

[0037] Step 5: Grinding and polishing to improve the gloss of the water basin surface, grind the surface smooth, and round the edges to reduce the impact of water flow.

[0038] Example 1: Laser repair process of the water bucket of an impulse turbine in a power plant in Jiangsu Province.

[0039] Damage details: Two cracks are present on the working surface of the turbine bucket, with crack lengths of 7mm and 12mm respectively. Figure 3 , Figure 4 .

[0040] The process steps are as follows:

[0041] First, non-destructive testing is performed to detect the specific cracks. The cracks are then mechanically cleaned to expose the metallic luster of the granulator substrate. Non-destructive testing is then performed again, and if no cracks are found, the process moves on to the next step.

[0042] This material was used for laser cladding. A 4KW fiber laser was used for laser cladding, with the following parameters: power 3500W, optical plate diameter 4mm, cladding thickness 0.5~1mm, and cladding speed 8-10mm / s. The material composition was: Cr: 16.5%; Co: 13%; Nd: 1.75%; Ni: 6.65%; C: 0.02%; Nb: 0.15%; W: 2.1%; V: 0.1%; Mo: 1.15%; Mn: 1.15%; Ti: 0.02%; N: 0.15%; Si: 1.0%; P: 0.03%; Fe: balance.

[0043] Laser cladding process description: This invention incorporates the specific shape of the working surface of the turbine bucket (see...). Figure 1 , Figure 2 It employs a combination of a rangefinder, a laser scanner, and a robotic arm.

[0044] Step 1: First, use a rangefinder and laser scanner to collect data on the irregular shape of the work surface, and then analyze the data using software.

[0045] Step 2: (1) Program the irregular arc surface of the water tank in segments;

[0046] (2) The software calculates and records the data of the tangent position of each arc surface, the change of the torsion angle, the speed and angle.

[0047] (3) Programming: First, program the outer edge of the water bucket to form a closed ring. Then, program the ring in segments. Each segment must have the same focal length and the thickness of the overlapping part must be controlled within 0.5mm.

[0048] (4) The programming data and focal length are combined into program instructions;

[0049] (5) Optimize and adjust the laser power and various parameters, and connect the powder feeder and robot arm data.

[0050] The third step is to transmit the entire programming instructions to the robotic arm. The robotic arm changes the focal length at any time according to the requirements of each program segment and different data, and synchronizes the powder feeding with the focal length to perform laser cladding.

[0051] Step 4: Non-destructive testing after laser cladding to check for defects such as pores and cracks on the surface.

[0052] Step 5: Manually grind the surface after laser cladding to remove high points of laser cladding overlap. Grind and polish all surfaces, and make the edges between each arc smooth to ensure a smooth surface without high points.

[0053] Step 6: Packaging and shipping.

[0054] Because the working surface of the turbine bucket is an irregular shape with inner and outer circular arcs (see...) Figure 1 , Figure 2 The inner and outer arc surfaces of the water tank are irregular working surfaces, both subjected to water flow impact. This can lead to issues such as concave corners, inconsistent laser focal length, uneven powder feeding of metal materials, and inconsistent cladding thickness during laser cladding. The repair method of this invention shortens the labor time required for programming irregularly shaped sections, simplifies the complex programming process, and greatly improves production efficiency.

[0055] After laser cladding, the machined surface of the water turbine is restored by machining. After machining, the surfaces of other undamaged working parts are laser clad to perform anti-corrosion treatment on the water tank surface with a thickness of 0.5-1mm.

[0056] After laser cladding, the entire water tank is polished to create a smooth surface transition, reducing the impact of water flow and meeting usage requirements.

[0057] Both non-destructive testing and hardness testing were passed.

[0058] After being put into use, and then tested again two years later, there were still no water puddles, wear, cracks, or other defects (e.g.) Figure 5 (As shown in the figure), proving that the material's erosion resistance and corrosion resistance fully meet the design specifications.

Claims

1. A laser-resistant and wear-resistant material for an impact turbine, characterized in that, The material comprises the following components by mass percentage: Cr: 10~20%; Co: 10~20%; Nd: 1.5~2.5%; Ni: 3~8%; C：0.01~0.2%； Nb: 0.1~1%; W：1~5%； V：0.1~1%； Mo: 0.8~1.2%; Mn: ≤3%; Ti: 0.01~0.1%; N：0.10~0.5%； Si: 0.1~0.2%; P: 0.01~0.05%; Fe: balance; The material is prepared through vacuum melting, vacuum atomization, and screening processes, and the particle size is alloy powder with a particle size of -100 to +200 mesh. The alloy powder is suitable for various fiber lasers. The cladding process parameters for the repair application of the powder material are as follows: use a 4KW-6KW continuous fiber laser and a fully automatic rotary fixture for laser cladding. The laser cladding parameters are: power 3000-5000W, spot diameter 4-6mm, cladding thickness 0.5-1.2mm, and cladding speed 8-15mm / s.

2. A process for repairing an impulse turbine using the laser-coated anti-corrosion and wear-resistant material for impulse turbines as described in claim 1, characterized in that, Specifically, the following steps are included: Step 1: Use a rangefinder to measure the height and low points on the object's surface, and record the changes in focal length based on the different height and low points; Step 2: Use a laser scanner to scan the entire surface of the object, collect data changes based on the surface shape, collect tree structure data, and construct a water bucket model drawing; use software to analyze the drawing, combine different focal lengths measured by the rangefinder, and program them uniformly. Step 3: The programming instructions are transmitted to the robotic arm, which then performs laser cladding according to the program; Step 4: Perform non-destructive testing after laser cladding to check the surface quality after laser cladding; Step 5: Grinding and polishing to improve the gloss of the water basin surface, grind the surface smooth, and round the edges to reduce the impact of water flow.

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