Modelling the in-service microstructural evolution of Ni-based superalloys for power generation

High temperature operation of power plant increases their efficiency and reduces emissions. Low gamma-prime fraction nickel-based superalloys, such as IN617, are becoming increasingly important in substituting for conventional steel components due to their better performance at higher temperatures. The aim of this work is to model the microstructural evolution in this alloy under typical operating conditions and relate this to its creep response. Although classified as solid solution strengthened alloys, they contain a range of different precipitates which contribute to the creep resistance, the most influential of these being gamma prime. The model is developed in three stages. Firstly, a precipitate-level variational model is derived to describe the nucleation and growth of individual particles and their interactions. The results are then passed up to a grain-level simulation where the response of a statistically significant particle ensemble is simulated via the evolution of particle distributions. The resulting model incorporates the effects of heat treatment and stress to give the simultaneous size and number evolution of the different phases in the material. This information is then used to construct plastic strain-temperature-time diagrams in order to estimate the creep rupture life of the material.