As a key component in the power system, turbine blades work in harsh environments such as high temperature, high pressure, high-speed rotation and corrosive media for a long time. They are prone to wear, corrosion, cracks and other damages, which seriously affect the performance and reliability of the turbine. As an advanced surface repair technology, laser cladding technology provides an efficient and reliable solution for the repair of turbine blades.
1. How laser cladding technology works in turbine blade repair
(I) Preparation before repair
First, conduct a comprehensive inspection and evaluation of the damaged turbine blades to determine the type, location, degree and scope of the damage. Then, clean the blades to remove impurities such as oil, rust, dirt, etc. on the surface, and pre-treat the damaged parts by mechanical processing, sandblasting or laser cleaning to increase the bonding strength between the cladding layer and the substrate.
(II) Selection of cladding materials
Select appropriate cladding materials according to the working conditions and performance requirements of turbine blades. Commonly used cladding materials include nickel-based, cobalt-based, iron-based and other alloy powders, which have good wear resistance, corrosion resistance, fatigue resistance and high temperature performance.
(III) Laser cladding process
Fix the pre-treated turbine blade on the workbench of the laser cladding equipment, and adjust the distance and angle between the laser head and the blade surface. The cladding material powder is evenly transported to the laser beam action area through the powder feeding device. Under the action of the high-energy-density laser beam, the cladding material and the blade substrate surface are rapidly melted and mixed to form a molten pool. As the laser beam moves, the molten pool solidifies rapidly to form a cladding layer that is metallurgically bonded to the substrate. During the cladding process, the laser power, scanning speed, powder feeding speed, protective gas flow rate and other process parameters are precisely controlled through real-time monitoring and control systems to ensure the quality and performance of the cladding layer.
(IV) Post-repair processing
After the laser cladding is completed, the repaired turbine blade is subjected to subsequent processing, such as stress relief annealing, machining, polishing, etc., to eliminate the residual stress of the cladding layer, improve the surface flatness and dimensional accuracy, and meet the use requirements of the blade.
2. Application cases of laser cladding technology in turbine blade repair
(I) Gas turbine blade repair
After a gas turbine has been running for a period of time, the blades have been worn and corroded, resulting in a decrease in the performance of the gas turbine. Laser cladding technology was used to repair the blades, and cobalt-based alloy powder was selected as the cladding material. By optimizing the process parameters, a cladding layer with uniform thickness, dense structure and good bonding with the substrate was successfully prepared on the blade surface. After testing, the performance of the repaired blades was restored to the initial state, and the operating efficiency and reliability of the gas turbine were significantly improved.
(II) Steam turbine blade repair
During the long-term operation of a steam turbine, the blades were eroded and corroded by steam, and a large number of pits and cracks appeared on the blade surface. Laser cladding technology was used to repair the blades, and nickel-based alloy powder was selected as the cladding material. The surface quality of the repaired blades was good, and the hardness and wear resistance were significantly improved, which effectively extended the service life of the blades and reduced the maintenance cost.
3. The absolute advantage of laser cladding technology in turbine blade repair
(I) High repair quality
The laser cladding layer and the substrate are metallurgically bonded, with high bonding strength and not easy to fall off. The cladding layer has a dense and uniform structure, without defects such as pores and slag inclusions, and has good wear resistance, corrosion resistance and fatigue resistance. It can effectively restore the size and performance of the blade and improve the service life of the blade.
(II) Small heat-affected zone
During the laser cladding process, the laser beam energy is concentrated, the heating and cooling speeds are fast, the heat input is small, and the heat-affected zone of the substrate material is small, which will not cause deformation of the substrate material and deterioration of the structural properties, and can maintain the original accuracy and performance of the blade.
(III) Precise repair
The laser beam has good directionality and focusing, which can achieve precise repair of the damaged parts of the blade. It has unique advantages for blades with complex shapes and high dimensional accuracy requirements.
(IV) Strong adaptability
Laser cladding technology can be used to repair blades of various metal materials, whether it is cast iron, cast steel, stainless steel or titanium alloy, it can achieve good repair results. At the same time, this technology can also repair the blades in situ without disassembling them, greatly shortening the maintenance cycle and reducing maintenance costs.
(V) Green and environmental protection
During the laser cladding process, no chemical agents and electrolytes are required, and no pollutants such as wastewater, waste gas and waste residue are generated. It is environmentally friendly and meets the environmental protection requirements of modern manufacturing.
As an advanced surface repair technology, laser cladding technology has significant advantages and broad application prospects in turbine blade repair. By reasonably selecting cladding materials and process parameters and adopting scientific repair processes, damaged turbine blades can be effectively repaired, the performance and reliability of the blades can be improved, the service life of the blades can be extended, the maintenance cost can be reduced, and a strong guarantee can be provided for the safe and stable operation of the turbine. With the continuous development and improvement of laser cladding technology, it is believed that its application in the field of turbine blade repair will be more extensive and in-depth.
