REACTION MECHANISM OF EARLY LIQUEFACTION STAGE OF SUS316/ INCONEL718-ZIRCALOY4 WITH AND WITHOUT OXIDE LAER

Abstract

The metallographic condition and influential factor of liquefaction between as-received/pre-oxidized Zircaloy and SUS/Inconel was examined by an isothermal annealing experiment with diffusion couples. Consequently, the liquefaction was confirmed at a eutectic point of Zr-Fe/Zr-Ni system around 75at%Zr and the kinetics was controlled by the mass flux of alloy’s elements to Zircaloy/liquid interface (dissolution rate of Inconel was 1.93 times of that of SUS). The oxide layer on Zircaloy delayed the onset of reaction for SUS, whereas it did not for Inconel. This may be attributable to lower activation energy of Ni in α-Zr(O) compared to that of Fe.