The effects of defects on fatigue life variability of nickelbased powder metallurgy superalloy FGH96 were investigated by conducting fatigue tests in large sample case at different stress levels. The fatigue life distribution characteristics of FGH96 were obtained. The fatigue fracture analysis of all the tests by scanning electron microscopy showed: (1) the defects contributing to fatigue failure mainly were nonmetallic inclusions; (2) under higher stress levels (1200

1100MPa)

inclusion in the surface was the lifelimiting factor

resulting larger life variability; (3) in the middle stress levels (1000MPa)

crack initiation in the internal inclusion did not affect the fatigue life variability; (4) under lower stress level (900MPa)

fatigue crack was initiated in the internally

there were no effects of internal inclusions on fatigue life variability. Therefore

the defects need to be considered in the life prediction at higher stress level.