Simulated Service Test Behaviour of Various Internal and External Coatings Applied on CF6-50 First Stage Turbine Blades

摘要

CF6-50 first stage turbine blade life is limited by the external Codep B coating life and corrosion attack in the uncoated cooling passages. Improvement of blade life might be obtained by application of an external overcoat on top of Codep B and by application of an internal coating. The current investigation was directed to simulated service testing and evaluation of various externally and internally applied coatings which were commercially available. The test results indicate that the application of external overcoats in most cases improved the corrosion behavior of the CF6-50 blades. The best external protection was offered by the application of an Al/Si slurry type of coating on top of Codep B. The application of internal coatings also improved considerably the corrosion performance of the CF6-50 blade. Internal corrosion was virtually eliminated by the application of Al/Si or Al gas phase coatings.