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Thermally Sprayed Nickel-Based Repair Coatings for High-Pressure Turbine Blades: Controlling Void Formation during a Combined Brazing and Aluminizing Process

Institut für Werkstoffkunde (Materials Science), Leibniz Universität Hannover, An der Universität 2, 30823 Garbsen, Germany
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Academic Editor: Narottam P. Bansal
Coatings 2021, 11(6), 725; https://doi.org/10.3390/coatings11060725
Received: 28 April 2021 / Revised: 27 May 2021 / Accepted: 8 June 2021 / Published: 16 June 2021
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
Turbine blades must withstand severe loading conditions and damage can occur during operation due to heat, pressure, foreign objects and hot gas corrosion, despite the protective coatings applied onto the turbine blades. Instead of replacing the damaged components, maintenance, repair and overhaul are key to extend the total service life. Besides welding, the repair of turbine blades by brazing is an established repair process in the industry and involves many individual steps that often require a high degree of manual work. In the present study, a hybrid joining and coating technology was developed to shorten the state-of-the-art process chain for repairing turbine blades. With this approach, a repair coating, which consists of a filler metal, a hot gas corrosion protective layer and an aluminum top layer, is applied by atmospheric plasma spraying. The coated turbine blade then undergoes a heat-treatment so that a brazing and aluminizing process is carried out simultaneously. Due to diffusion and segregation processes, pores can occur in the heat-treated coating. In the present study, a full factorial design of experiment was performed to reduce the pores in the coating. The microstructure of the repair coating was investigated by optical- and scanning electron microscopy (SEM), and the impact of the process parameters on the resulting microstructure is discussed. View Full-Text
Keywords: aircraft overhaul; high-temperature brazing; aluminizing; hybrid technology; protective coatings aircraft overhaul; high-temperature brazing; aluminizing; hybrid technology; protective coatings
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MDPI and ACS Style

Nicolaus, M.; Möhwald, K.; Maier, H.J. Thermally Sprayed Nickel-Based Repair Coatings for High-Pressure Turbine Blades: Controlling Void Formation during a Combined Brazing and Aluminizing Process. Coatings 2021, 11, 725. https://doi.org/10.3390/coatings11060725

AMA Style

Nicolaus M, Möhwald K, Maier HJ. Thermally Sprayed Nickel-Based Repair Coatings for High-Pressure Turbine Blades: Controlling Void Formation during a Combined Brazing and Aluminizing Process. Coatings. 2021; 11(6):725. https://doi.org/10.3390/coatings11060725

Chicago/Turabian Style

Nicolaus, Martin, Kai Möhwald, and Hans Jürgen Maier. 2021. "Thermally Sprayed Nickel-Based Repair Coatings for High-Pressure Turbine Blades: Controlling Void Formation during a Combined Brazing and Aluminizing Process" Coatings 11, no. 6: 725. https://doi.org/10.3390/coatings11060725

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