RuAviation

Over 47,000 passenger aircraft worldwide, and approximately 1,500 in Russia, take to the skies thanks to gas turbine engines. A critical component within their design is the turbine blades, which are subjected to significant stresses: high temperatures, erosion, and corrosion. Over time, this leads to wear and tear, necessitating refurbishment.

However, quality issues with protective coatings following refurbishment often arise, curtailing blade service life. Researchers at Perm Polytechnic University (PNIPU), in collaboration with engineers at UEC-Perm Engines, have proposed novel approaches to blade treatment that aim to boost their reliability and longevity.

“JS6K, a nickel-based alloy known for its creep-resistant properties, is used in the manufacture of the blades. It can withstand temperatures of up to 1,000°C and is the ideal material for gas turbine engines. However, even such a robust alloy requires protection from external environmental factors. To this end, aluminide coatings are applied to the blade surfaces. During refurbishment, the old coatings are removed, and new ones are applied following thorough surface preparation. Traditionally, shot peening has been used for this purpose, but it doesn’t always ensure coating uniformity, leading to defects and a reduced component lifespan,” the university stated.

PNIPU researchers conducted a series of experiments to determine how different surface preparation methods impact the quality of the protective coating. They compared three treatment techniques: shot peening, abrasive water jet machining, and polishing. Abrasive water jet machining yielded the best results, achieving a uniform layer depth within the range of 30-60 μm and avoiding surface defects.

Furthermore, the researchers identified the optimal atomiser pressure for applying the aluminium coating – 2.0 atmospheres. This value ensures the most effective distribution of the protective layer, ultimately increasing component durability. The developed recommendations have already been trialled at UEC-Perm Engines and have demonstrated their effectiveness.

The research findings will not only enhance the quality of blade refurbishment but also render the process more economically viable. For the aviation sector, where every component must perform under extreme conditions, high-quality refurbishment is of paramount importance. Further testing is planned in real-world engine operating conditions in the near future to validate the long-term effectiveness of the proposed methods.