Abstract Scope |
The rotating turbine disks, spools, and seals in the hot section of gas turbine engines are typically made of Nickel-base superalloys. These components operate at high temperatures resulting in dirt accumulation, oxidation, and hot corrosion, and must be cleaned during overhaul to enable inspection and repair. It was found that the typical cleaning solutions used may dissolve the fine carbides present in some superalloys with potential impact on Low Cycle Fatigue (LCF), but that prior shot peening can mitigate this effect. It was also found that, for the highest operating temperatures, grain boundary oxidation may occur in some superalloys and the resultant very fine grain boundary oxides near the surface may be removed by the cleaning process with potential impact on LCF, but that post-cleaning shot peening can address this effect. Studies also showed that more aggressive cleaning solutions may be possible but their impacts on surface condition must be carefully assessed. Finally, it was shown that ultrasonic energy can improve the productivity of the cleaning solutions but must be introduced with proper care to prevent unintended resonance vibration risk to the part. |