Comparison between impression creep and uni-axial tensile creep performed on nickel-based single crystal superalloys

The purpose of the present work is to build the relationship between impression creep and conventional uni-axial tensile creep in determining crystallographic creep parameters for face centered cubic (FCC) nickel-based single crystal superalloys. To this aim, the impression creep performed on [0 0 1]-, [0 1 1]-, and [1 1 1]-oriented nickel-based single crystal superalloys were respectively investigated and the data was compared with those obtained with uni-axial tensile creep counterparts. It shows that the determination of crystallographic creep stress exponent is independent of crystallographic orientations, and the results agree reasonably well between impression creep and uni-axial tensile creep. However, some reveres dependence of crystallographic orientation was observed between impression creep and uni-axial tensile creep, such as the steady-state punch velocity for impression creep and steady-state elongation rate for uni-axial tensile creep, and this induced different stress conversion factors among different crystallographic orientations.