Creep-fatigue failure of an aero engine turbine blades

A fighter plane had undergone problems during flight. Initial investigation pointed out that one 2nd stage turbine blade was fractured. Metallurgical investigation revealed that the fractured blade was subjected to abnormally high stresses at elevated temperature. This situation led to the creep and created ‘w-cracks’ (triple point cracks) in the blade by the mechanism of grain boundary sliding. These cracks became the initiation sites of the fatigue cracks. The blade finally failed due to fatigue under low cycle fatigue (LCF) conditions.