Creep and creep-fatigue behaviour of Udimet 720 at 850°C

The object of this study is to identify damage mechanisms operating at high temperature (850 degrees C) in Udimet 720, a nickel-based superalloy strengthened by gamma' Ni3Al precipitates. In addition to environmental effects, the extension of viscoplasticity may result in specific damage mechanisms, such as intergranular cavitation, wedge cracking and/or thermal coarsening of gamma' particles. The major mechanisms have been investigated using tensile smooth specimens, for creep and creep-fatigue loadings. The introduction of the relevant damage parameters in a model describing the viscoplastic behaviour of the material is tentatively discusssed.