Study on the root causes for the premature failure of an aircraft turbine blade

A study on the root causes of the premature failure of a set of blades belonging to the high pressure turbine of an aircraft engine has been carried out. These blades were manufactured using a precipitation hardened nickel base alloy. The study consisted in a fractographic analysis by scanning electron microscopy and a microstructural examination by optical and scanning electron microscopy, identifying those phases which were present by means of X-ray energy dispersive spectrometry. Fractographic analysis revealed that failure of the first blade was due to thermo-mechanical fatigue, initiated at the internal cooling cavities. The presence of large size, cracked, hafnium and tantalum primary carbides on the fracture surfaces indicates that they have played an important role on the failure process, accelerating it. The other blades failed later by the impacts of the fragments lost from the first one.