Experimental characterization and mechanical modeling of creep induced rafting in superalloys

A constitutive model has been developed for the high temperature mechanical behavior of single crystal superalloys, including rafting and its consequences. The flow stress depends on the γ channel width via the Orowan stress. An evolution equation for channel widening during high temperature straining has been derived and calibrated with measurements. Therein, rafting is assumed to be driven by the relaxation of internal stresses. The model is able to represent the mechanical softening at high stresses consecutive to rafting. The model has been applied to simulate rafting during uniaxial creep in several crystal orientations, in notched specimens as well as in cyclically loaded specimens.

► A viscoplastic model for single crystal superalloys has been developed.
► The model has been designed to predict the kinetics of rafting at high temperature.
► The model accounts for the strength reduction consecutive to rafting.
► The model has been calibrated with creep tests and verified with complex loadings.
► The model has been applied to the alloy CMSX-4 at 950 °C and 1050 °C.