Modeling of liquid phase formation due to the solid Zircaloy-4/solid Inconel 718 interaction

A diffusion model that describes the eutectic interaction between both as received and oxidized Zry-4 and Inconel 718 at high temperatures (1000 to 1400 deg C) is presented, which is an improvement of one previously developed for depicting this interaction. The instantaneous positions of the Zry-4/liquid and Inconel/liquid interfaces, taken from reported experimental work, are input data. The assumptions of this model are: the liquid phase grows by diffusion of the main element of each alloy in the liquid phase, there is no interaction between these elements during diffusion, neither convection nor solid state diffusion are considered, and volume changes during melting and interdiffusion are neglected. We calculate the solid/liquid interfaces concentration values and the interdiffuion coefficients in the melt for different temperatures according to experimental data. The liquid phase formation kinetics is measured with initial zirconium oxide layers of 0, 20, 45 and 100 μm to simulate the reactor operation condition. The initial oxide layer retards the liquid formation kinetics and this leads, after the application of the model, to different interfaces concentration values and interdiffusion coefficients. (author). 9 refs., 5 figs., 2 tabs