Investigation of nickel alloy fan blade failure in a flue gas desulfurization unit

- The investigated blade failed after only 5 years of operation instead of minimum of 20 years.
- Fatigue crack propagation was found and was accelerated by the presence of non-metallic inclusions and shrinkage porosity.
- The crack initiations were the result of casting defects that were exposed to the surface of the blade during machining.