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Introduction to the Application of Thermal Spraying Technology in Gas Turbine Maintenance
Release time:
2020-11-21 22:47
Source:
Gas Turbine Maintenance
Gas turbine power generation is becoming a hot topic in China’s power industry. Today, the development level of the gas turbine industry has become an important indicator of a country’s industrial advancement. As low-pollution emission technologies for gas turbines continue to evolve, gas turbines fueled by natural gas—and their combined-cycle systems—have emerged as the new favorites in 21st-century power-generation equipment. How to reach new heights in energy-sector development has become the pursuit of Chinese power professionals. Addressing the issue of heavy-duty gas turbines being subject to foreign control is both a national imperative and the shared dream of all Chinese power engineers. For a long time, developed Western nations have strictly controlled the export of high-tech products to China; among these, high-power gas-turbine technology has undoubtedly been a key focus of their protection efforts—whether it involves the manufacture of new units, the maintenance of older ones, or the production and repair technologies for critical components.
1 Gas Turbine Maintenance Technology
1.1 Major Maintenance Technologies
Aerospace-derived gas turbines boast excellent performance, advanced manufacturing technology, and a complex process and structural design. They place extremely stringent demands on repair techniques and processes, necessitating major overhauls at the factory. The key process technologies employed in these overhauls encompass seven aspects:
1.1.1 Disassembly and Assembly Techniques
To repair gas turbines at the factory, it is first essential to have the capability to disassemble and reassemble them. It is crucial to achieve high efficiency while simultaneously avoiding secondary damage to the gas turbine. This technique requires skilled technicians and a large inventory of specialized tools and equipment.
1.1.2 Component Cleaning Technology
Cleaning is primarily used to remove contaminants adhering to the surface of parts, including rust layers, oxide scales, dirt, carbon deposits, oil stains, paint, silicone, and other residues. The cleaning effectiveness must meet the requirements for part inspection and non-destructive testing. Cleaning methods include: organic solvent cleaning, chemical solution cleaning, steam cleaning, high-pressure water cleaning, sandblasting, and vibratory polishing for surface finishing. Parts that have undergone cleaning must be dried in a drying oven.
1.1.3 Detection Technology
Detection technologies are primarily used to identify cracks on the surfaces and within the interiors of parts. These nondestructive testing techniques include visual inspection, dimension measurement, fluorescent penetrant testing, magnetic particle testing, eddy current testing, and radiographic testing. Fluorescent penetrant testing is mainly employed for detecting surface cracks in parts; magnetic particle testing is used to detect surface and near-surface cracks in ferromagnetic parts; eddy current testing is utilized for detecting cracks in threaded holes of parts; and radiographic testing is applied to detect defects in a small number of welded repair components. Advances in signal and image processing technologies, along with system automation, have enhanced detection capabilities and reliability, enabling estimations of component lifespans and precise calculations of inspection intervals between components. In recent years, significant progress has been made in the miniaturization of probe heads, greatly improving the applicability of endoscopic monitoring technologies.
1.1.4 Welding Technology
Welding technologies mainly include inert gas shielded welding, electron beam welding, plasma arc welding, linear welding, vacuum welding, laser welding, and brazing. Among these, plasma arc welding can restore repaired parts to the performance of new components and is primarily used for repairing sealing devices. Tungsten inert gas (TIG) welding is employed for overlay welding of blade-type sealing components, with an extremely small heat-affected zone. High-tech brazing is used to braze nickel-palladium alloys and cobalt-based brazing alloys, making the repaired parts even more wear-resistant than the original ones. Laser welding ensures higher measurement accuracy, enabling strict control over deformation, diameter, and dimensions of the joint area.
1.1.5 Coating Technology
Gas turbines commonly employ high-temperature coating technologies to enhance performance, improve reliability, and extend service life. Among the critical hot-end components, turbine blades are coated with thermal barrier coatings on their surfaces; the blade interiors are coated with oxidation- and heat-corrosion-resistant coatings; turbine shrouds are coated with sealing coatings; and blade tips are coated with wear-resistant coatings. The primary coating-spraying techniques include vacuum spraying, laminar-flow spraying, supersonic plasma spraying, as well as physical and chemical vapor deposition. Given that the cost of high-temperature alloys and blade fabrication far exceeds the cost of coatings, it is of great importance during maintenance to remove coatings—either locally or entirely—and then repair the blades, ensuring that the original properties of the blade substrate remain intact while allowing for safe continued use.
After GE Aviation began using chromium-rich coatings at its maintenance facility in Singapore, blade scrap rates decreased by 2%. Platinum-aluminum coatings can enhance the reliability of blades under harsh high-temperature conditions, while ceramic coatings can prevent molten salt from eroding the coating substrate at high temperatures.
1.1.6 Finishing Technology
Mechanical machining and repair processes include turning, boring and milling, and grinding. Turning is primarily used for machining the diameters of parts such as sealing rings before and after coating, as well as for precision machining of flanges on casing components following their replacement. Boring and milling are mainly employed for repairing parts such as holes, slots, bosses, and shaft journals. Grinding is primarily used for precision finishing of part surfaces after repairs involving electroplating or coating.
1.1.7 Commissioning Technology
Test runs are a critical step in gas turbine maintenance—they serve as a crucial check on the effectiveness of turbine repairs and directly affect the turbine’s operational performance. The aerodynamic design of a gas turbine test stand must be able to perfectly simulate actual field operating conditions, and it must also incorporate stringent noise control measures.
1.2 Maintenance Technology R&D
The primary goal of R&D in maintenance technologies is to continuously reduce the lifecycle costs of gas turbines and to restore—or even enhance—their performance. In light of this, OEMs and maintenance companies place great importance on the development of maintenance technologies. For example, GE Aviation invests between 30 million and 91.4 million U.S. dollars annually in R&D for maintenance technologies. To date, it has developed more than 15,000 different maintenance technologies and methods. Moreover, the warranty period for some components after repair has even been doubled. GE’s R&D efforts are primarily focused on seven key areas: engine cleaning, chemical treatments, inspection methodologies, machining technologies, welding techniques, material repair using cold metal arc spray deposition technology, and other related advanced technologies.
Lufthansa, as a user, is developing maintenance technologies with the aim of addressing frequent failures, reducing costs, and improving efficiency. Currently, 3D printing technology and integrated fault diagnosis techniques are also advancing rapidly in the field of gas turbine maintenance. As the geometry of gas turbines becomes increasingly complex, more reliance will be placed on robots to carry out repetitive monitoring and repair tasks.
Materials - Equipment - Processes - Solutions
We have accumulated extensive experience in coating applications, and we are now replicating these successful case studies. We will guide you through the entire coating manufacturing transition process, ensuring: rapid production start-up; a reliable supply solution that covers everything—from materials and equipment to processes; coating trials conducted either at your site or at our technology center; and consistently high coating quality and efficiency.
Relevant Information
The complete set of plasma-sprayed equipment has been shipped to the customer’s site in Thailand.
Core spraying equipment: SX-80 plasma spray main unit, with a 15,000℃ flame suitable for multiple materials including zirconia and silicon carbide; powder feeding accuracy of ±1%, and coating thickness tolerance ≤ ±5 μm. Environmental protection support system: Customized soundproof booth + pulse dust collector—effectively addressing spray noise pollution while achieving highly efficient dust recovery, compliant with Thai environmental standards. Automated equipment: 6-axis industrial robot + intelligent spray cart, enabling precise spraying of complex workpieces and automated loading/unloading, boosting production efficiency by 40%.
On-site engineers provide hands-on training, focusing on the core operations of plasma spraying equipment such as the SX-80. Sanxin has customized a complete solution for its customers, including an automated spraying robotic arm, a soundproof booth, and a dust removal system—ensuring both high spraying efficiency and compliance with environmental standards.
Guangzhou Sanxin Thermal Spraying Turntable Shipment
Guangzhou Sanxin Company manufactures single-station and multi-station thermal spray turntables, which can be paired with plasma equipment, supersonic equipment, and arc equipment. We offer rapid, customized production tailored to customer requirements and product dimensions. A thermal spray turntable is a high-precision rotary worktable specifically designed for thermal spraying processes—including flame spraying, plasma spraying, and arc spraying. By providing controllable rotational speed and exceptional stability, it ensures uniform coating thickness on the workpiece surface, thereby enhancing spraying efficiency and quality.
SX-80 plasma equipment is being used at a customer site in Russia.
SX-80 plasma equipment is being used at a customer site in Russia.
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