Failure analysis of the 1st stage blades in gas turbine engine

The failure analysis of the first stage blades in a gas turbine made of nickel-base Inconel 738 is presented. The failure of the gas turbine occurred at approximately 1069 operating hours with 58 starts after the last overhaul. Several examinations were carried out to identify the blade failure’s root cause: macroscopic inspection, microscopic examination, and metallographic analysis. It is found that one of four fractured blades (the No. 62 blade) had initially cracked by a fatigue mechanism over a period of time, and then fractured by the overload at last moment and the other three fractured blades (the No. 63, No. 1 and No. 2 blades) are all instant fracture with the dendrite morphology, which resulted in the initiation of fatigue crack at the porosity metallurgical defects in the trailing edge of No. 62 blade due to the stress concentration aroused by these porosity defects and cavitations.