A New Approach to Modeling of Creep in Superalloys

Abstract

A new theory of superalloy creep is presented. It is argued that ' particles in superalloys do not play a rate-controlling role during creep. They are hypothesized to act as composite reinforcements regardless of their size. The rate-controlling role is ascribed to dislocation related obstacles such as nodes, jogs or kinks.The basic constitutive law based on this premise is shown to be capable of representing the time to strain data of a wide range of superalloys. Equations for primary and tertiary creep are developed based on the composite concept and are shown to predict the creep behavior of DS-GTD111 TM a superalloy commonly used in gas turbines. The new approach is also shown to be capable of explaining a wide range of observations reported in the literature. The implications of these findings in terms of the effect of microstructure on creep behavior are discussed.

Critical assessment 31: On the modelling of tertiary creep in single-crystal superalloys

“…A critique on the usefulness of the different models is challenging for a number of reasons. Oruganti [33,46] pointed out that cases of poor correspondence between experiments and model predictions are often attributed to gaps in understanding damage mechanisms rather than to the basic constitutive creep laws used. As such, the critical assessment of these laws is of importance.…”