A Generic Microstructure-Explicit Model of Creep in Nickel-Base Superalloys

Abstract

Past approaches to modelling the creep behaviour of engineering alloys have been either totally empirical or, while having functional forms consistent with current understanding of deformation and fracture mechanisms, have been calibrated by comparison with an available creep database. They have not specifically included quantitative measures of the microstructural features that are thought to impart creep resistance to the alloys. The present paper reviews and extends a microstructure-specific model of creep in particle-strengthened alloys in which the model parameters are directly related to measurable characteristics of the microstructure of nickel-base superalloys. The model accounts for three previously identified changes in microstructure that occur during the creep of superalloys: (i) coarsening of the precipitate; (ii) the progressive increase in mobile dislocation density with accumulated creep strain; and (iii) the development of grain boundary cavities. The relative dominance of each will be demonstrated using a set of commercial alloys with specific alloy microstructures. It is emphasised that the model-generated curves are true predictions using input microstructural characteristics and are not empirically fitted to the creep data.