Technical field
The present invention relates to the field of gas turbines, and more specifically, to a gas turbine blade remanufacturing and repair process.
Background technique
As an important power output device, gas turbines have been widely used in power generation, shipbuilding, aviation, and other industries. Its core part is mainly composed of three parts: compressor (i.e. compressor), combustion chamber, and turbine. The working process of a gas turbine is that the compressor continuously inhales air from the atmosphere and compresses it; the compressed air enters the combustion chamber, mixes with the injected fuel, and is burned to become high-temperature gas, which then flows into the gas turbine to expand and perform work, pushing The turbine impeller rotates with the compressor impeller, ultimately converting the chemical energy of the fuel into mechanical energy.
Gas turbine turbine blades are important components of gas turbines. The gas produced after the fuel and air are mixed and burned pushes the blades to do work, providing kinetic energy for the gas turbine. Nickel alloy is the main material used to make gas turbine blades. Nickel alloys used in gas turbine manufacturing generally have high durable strength, fatigue strength, and durable plasticity properties, and are highly stable in structure and mechanical properties at the operating temperature of the gas turbine device.
Due to long-term wear, impact, high-temperature gas, and thermal and cold fatigue, gas turbine blades will produce defects such as wear, corrosion, and cracks and become invalid and scrapped. The failure mechanisms are mainly cavitation, corrosion, wear, high-temperature oxidation, and fracture caused by fatigue. This places high requirements on the wear resistance, anti-corrosion performance, high-temperature oxidation resistance, and mechanical properties of the materials of gas turbine blades.
At present, the main repair method for failed gas turbine blades is fusion welding repair, which mainly includes argon arc welding, plasma arc welding, laser welding, micro-arc spark welding, etc. In addition, repair methods include brazing, laser cladding, powder metallurgy, etc. These methods are limited to restoring blade function and do not or only slightly improve the service life of the blade.
Contents of the invention
The purpose of the present invention is to overcome the above-mentioned shortcomings in the prior art and provide a method for remanufacturing and repairing failed gas turbine blades.
The present invention is a method for remanufacturing and repairing failed gas turbine blades. First, the laser cladding process is used to restore the size of the failed gas turbine blades, and then the shot peening process is used to perform shot peening treatment on the surface of the repaired gas turbine blades, and then plasma is used. The spraying process sprays a layer of cermet coating to obtain a new blade with a composite coating, which completes the remanufacturing of the gas turbine blade. Specifically, follow the following steps:
The first step: Use laser cladding technology to restore the dimensions of the failed gas turbine blades. The repair material uses low-melting point nickel-based alloy powder. The laser scanning power is 2.5~4KW and the scanning speed is 200~400mm/min;
Step 2: After the blade is laser cladding, the outer surface of the blade is shot peened. The shot peening material is a glass shot with a diameter of 0.8-1.2mm and a shot peening pressure of 0.4-0.5MPa. Shot peening time is 80-100s. Through shot peening, a 150 μm thick compressive stress subsurface layer is produced on the blade to improve the fatigue resistance of the material;
Step 3: Use plasma spraying technology to spray the gas turbine blades after the first and second steps. The spraying material is WC-12Co cermet powder, the powder particle size is 35-75μm, the plasma spraying power is 40KW, the spraying distance is 70-120mm, the main airflow is 30-40L/min, the thickness of the spray coating is 240μm-280μm on the windward side and 180μm-220μm on the non-windward side.
The gas turbine blades repaired by the process method of the present invention have good wear resistance and corrosion resistance, and can greatly increase the service life of the blades, and their service life is 2-3 times that of the original blades.
This invention uses three composite processes: laser cladding process, shot peening process, and plasma spraying process to repair gas turbine blades. It not only restores the size but also forms a layer of cermet coating on the surface of the blades, which greatly improves the service life of the gas turbine blades.
Detailed ways
The present invention will be further described below in conjunction with specific embodiments.
The present invention mainly involves three processes: laser cladding, shot peening, and plasma spraying, which are introduced as follows:
Laser cladding technology is a technology that has been widely used in recent years. Laser cladding refers to the rapid melting and solidification of selected coating materials on the surface of the cladding substrate in different ways under laser beam irradiation. Afterward, a surface coating with extremely low dilution and metallurgical bonding with the substrate is formed, which significantly improves the wear resistance, corrosion resistance, heat resistance, oxidation resistance, and other properties of the substrate surface, thereby achieving the purpose of surface modification or repair. Compared with processes such as surfacing, spraying, electroplating, and vapor deposition, laser cladding has the characteristics of small dilution, dense structure, good combination of coating and substrate, and many suitable cladding materials, so it is widely used.
Shot peening process
Shot peening is one of the effective methods to reduce part fatigue and improve service life. Shot peening is spraying a high-speed shot stream onto the surface of the part, causing plastic deformation on the surface of the part to form a reinforced layer of a certain thickness. Due to the existence of compressive stress on the surface of the part, part of the stress can be offset when the part is under load, thereby improving the fatigue strength of the part and extending the safe working life. Shot blasting materials mainly include steel shot and glass shot.
Plasma spraying process
Plasma spraying is a material surface strengthening and surface modification technology that can make the surface of the substrate have wear resistance, corrosion resistance, high-temperature oxidation resistance, electrical insulation, heat insulation, radiation protection, wear reduction, and sealing properties. Plasma coating technology uses a plasma arc driven by DC as a heat source to heat ceramics, alloys, metals, and other materials to a molten or semi-molten state, and spray them at high speed onto the surface of the pretreated workpiece to form a firmly adherent surface layer.
Plasma spraying technology is a new multi-purpose precision spraying method developed vigorously after flame spraying. It has the following characteristics:
① The energy beam is very concentrated and can melt all powders with high hardness and high melting point. Therefore, it can be used for a wide range of spraying materials and can be used to prepare a variety of coatings.
② Due to the high flight speed of spray particles, the resulting coating is smooth, dense, and has a high powder deposition rate.
③ During the spraying process, the matrix is not charged or melted, and the matrix and the spray gun move relatively fast, so that the matrix structure does not change. The shape and performance of the substrate will not be affected by heat.
④ The working gas is an inert gas, which protects the substrate and powder from oxidation, and there are few impurities in the coating.
⑤ Simple operation, low equipment maintenance cost, and good adjustment performance.
The invention uses laser cladding technology, shot blasting technology, and plasma spraying technology to repair failed gas turbine blades. There are mainly three process steps.
The first step: Use laser cladding technology to restore the size of the failed gas turbine blade. The repair material uses low melting point NiCrBSi nickel-based alloy powder. The laser scanning power is 2.5~4KW, and the scanning speed is 200~400mm/min.
The second step: shot peening the outer surface of the gas turbine blade after the first step. Glass shot is selected as the shot peening material, with a diameter of 0.8-1.2mm, a shot peening pressure of 0.4-0.5MPa, and a shot peening time of 80-100s. Through shot peening, a compressive stress subsurface layer of about 150 μm thick can be produced on the blade to improve the fatigue resistance of the material. Shot peening is also a process before plasma spraying. Through shot peening, the bonding strength between the plasma sprayed layer and the substrate can be improved.
The third step: Use plasma spraying technology to spray the gas turbine blades after the first and second steps. The spraying material is WC-12Co cermet powder, and the powder particle size is 35-75 μm. The plasma spraying power is 40KW, the spraying distance is 70-120mm, and the main airflow is 30-40L/min. The thickness of the spray coating is 240μm-280μm on the windward side and 180μm-220μm on the non-windward side.
The gas turbine blades repaired by the process method of the present invention have good wear resistance and corrosion resistance, and can greatly increase the service life of the blades, and their service life is 2-3 times that of the original blades.
