Failure study of an aircraft engine high pressure turbine (HPT) first stage blade

In jet engines, almost 50% of failures are located in the damage of turbine blades and discs. This paper presents the study to determine the root cause of the failure of a high-pressure temperature blade in a turbofan engine. Visual observation of the blades indicated that initially-one blade was fractured. Subsequently, detachment of the airfoil from this blade and its impact with the rest of the blades of the first turbine disc trigged a catastrophic damage to them and affected later stages blades. Chemical, microstructural and mechanical characterization determined that blade material corresponded to René 142 nickel superalloy. The observed fractographic characters by optical and scanning electron microscopy showed that the fracture of the first damaged blade was due to a thermo-mechanical fatigue mechanism. The fatigue phenomenon was initiated by corrosion pitting on the root surface of the mentioned blade and progressed due to the cyclic stresses and temperature gradients.