Creep-fatigue behavior at high temperature of a UDIMET 720 nickel-base superalloy

High temperature fatigue and creep-fatigue properties of the wrought nickel-base superalloy Udimet 720 have been investigated. Tests have been performed in air at 700 degrees C under stress control with a triangular signal for fatigue and with a trapezoidal one for creep-fatigue. The creep influence has been studied up to the failure for dwell times ranging from 1 to 50 s. The dislocation microstructures of the failed specimens have been studied by transmission electron microscopy (TEM), in function of increasing dwell time. Damage processes have been characterized on the fracture surface and on the gauge length of the different specimens using scanning electron microscopy (SEM). The introduction of the dwell time lowers the number of cycles to failure as compared to fatigue testing conditions and also reduces the total accumulated time at maximum stress as compared to creep conditions. (C) 2009 Elsevier Ltd. All rights reserved.