Corrosion and fatigue failure analysis of a forced draft fan blade

The present work was carried out to investigate the failure mechanism of a power plant forced draft fan (FDF) blade made of 2014-T6 Al alloy, using visual examination, microstructural characterizations, study of the fracture surface and hardness testing. Based on the obtained results, surface defects including corrosion pits due to the existence of Cl ion and also erosion pits due to mechanical action of particles in the air entering from the filtration system and abrading on the fan blades surfaces, increased the probability of surface crack initiation. Cyclic loading and stress concentration on these surface defects influenced the fatigue life of the blade due to elevating the mean stress and resulted in fatigue failure of the investigated FDF component.

► Corrosion and erosion pits increased the probability of surface crack initiation.
► Propagation of fatigue cracks has resulted in failure of the investigated blade.
► The failure was not due to the mechanical properties degradation of the blade.