Homogenization kinetics of a typical nickel-based superalloy

The kinetics analysis of homogenization in Inconel 718 superalloy needs much more attention. For instance, the activation energy of Laves phase dissolution has not been determined so far, which is required for characterization of the underlying mechanisms. In the present work, based on Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis, diffusion calculations, and experimental investigation of homogenization at different temperatures and holding durations, the kinetics of Laves phase dissolution was studied. The activation energy of 274.5 kJ/mol was determined in this respect, which is close to the activation energy for diffusion of Mo in Ni (288.15 kJ/mol). Moreover based on the diffusion coefficients, it was found that the diffusion of Mo in Ni is slower than those of Nb and Ti in Ni. These results were also supported by the calculations based on the diffusion distance and it was concluded that the back-diffusion of molybdenum in austenite is the controlling micro-mechanism for dissolution of the undesirable Laves phase in this common superalloy. [Display omitted] •Activation energy of 274.5 kJ/mol was determined for the dissolution of Laves phase.•Kinetic analysis was based on JMAK analysis, diffusion calculations, and experiment.•Back-diffusion of Mo is the controlling mechanism for Laves phase dissolution.