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

Abstract

Modelling of tertiary creep in single-crystal superalloys -operative over the majority of the temperature/stress regime of relevance -is assessed. Traditional, empirical approaches are useful for the prediction of component life; a modern trend is for more physically faithful models which account for microstructure and alloy composition. Calculations are made using different methods, to identify advantages/disadvantages, in an effort to approach best practice. The predictions are tested against experimental data. The creep resistance can be estimated to within approximately one-half of a Larson-Miller parameter, from an input of alloy composition, deformation conditions, and estimates of microstructural parameters, rate laws (and parameters therein), and physical constants. Different merit indices are considered to identify the most appropriate for compositional optimisation.

Processing, Microstructures and Mechanical Properties of a Ni-Based Single Crystal Superalloy

“…First, many processing steps are based on trial-and-error approaches, which lack microstructural evidence. Second, under service conditions, the microstructure would evolve and degrade under mechanical loading at various temperatures, which dictate the failure mechanisms of these superalloys [21][22][23][24][25][26][27][28]. For example, the well-known rafting and directional coarsening of the γ phase are observed both under service and laboratory conditions at sufficiently high temperatures under a wide range of applied stresses [29,30].…”