Intermediate temperature creep damage mechanisms of a directionally solidified Ni-based superalloy
Maryam Torfeh, S.M.H. Mirbagheri, Jonathan Cormier, Jamshid Aghazadeh Mohandesi, Soheil Nakhodchi
Abstract
Microstructure evolution and damage mechanisms during the creep deformation of a directionally solidified Ni-based superalloy were evaluated. The creep deformation behaviour was studied along the longitudinal direction (i.e. along the solidification direction), at a moderate temperature of 870 °C, and applied stresses ranging from 310 to 450 MPa concerning the service conditions in industrial gas turbine blades. It was shown that at the lower stress levels of about 310 MPa, the average creep strain rate decreased by two orders of magnitude, while tertiary creep appeared as the dominant stage. Progressive coarsening of γ’ precipitates was also observed, meantime γ’ precipitate shearing was confirmed to occur over the evaluated range of stresses.