Cause of Cracking on Nickel-based Single Crystal Alloy Turbine Blade

High pressure turbine blade of an engine cracked is made of nickel based single crystal alloy blade, the blade after vibration fatigue test at room temperature. The causes of cracking on blade were analyzed by means of macroscopic observation, metallographic examination and scanning electron microscope analysis. The results show that the fatigue cracking of inlet blade root and blade root stretch section was found. There were many small notches in the inner wall of air film holes of inlet blade root and the loose defects on the sub surface of blade root stretch section. The defects were easy to form crack sources, which promoted the crack initiation, and finally led to cracking failure after crack propagation.