Simulation of creep cavity growth in Inconel 718 alloy

Nickel base superalloys provide significant improvements relative to the limitations in the areas of creep resistance, oxidation, low cycle and high cycle fatigue resistance. Since these materials are being pushed to limits of their capability in gas turbine applications, accurate mathematical models are needed to predict the service lives of the high temperature components to prevent unscheduled outages due to sudden mechanical failures. The objective of the work presented in this paper is aimed at developing a methodology to perform creep cavity growth simulation in the components fabricated by the alloy IN 718. This work mainly focuses on studying the influence of surface diffusion and the grain boundary diffusion as competing mechanisms in creep cavity growth. The differential equations developed by considering the contribution from either of these diffusion modes have been solved numerically using a finite difference scheme to track the interface explicitly during the cavity growth process in the specified conditions of stress and temperature. The results of the simulation have been validated by performing creep and stress rupture tests of IN 718 samples.