Influence of stress developed due to oxide layer formation on the oxidation kinetics of Zr-2.5%Nb alloy

Knowledge of oxidation kinetics of Zr alloys is extremely important because it helps to evaluate the lifetime of pressure tubes, which constitute an i ntegral part of the heat transfer system of many nuclear power stations. Th e presented diffusion model describes oxidation kinetics of zirconium alloy (Zr-2.5%Nb) under stress at the oxide/metal interface. A major assumption of this model is that the gas/oxide interface moves inwards into the oxide scale by creating a continuous network of internal defects (cracks, voids, etc.). A linear relation coupling the equations describing the evolution in the movement of the gas/oxide and oxide/metal interfaces was used as a fir st approach. After a certain period of time, the diffusion process obeys a pseudo-steady-state solution. A distance between gas/oxide and oxide/metal represents a thickness of the non-porous layer that remains constant during the pseudo-steady-state growth. An explanation of a possible transition be tween the parabolic and the cubic character of the oxidation kinetics is pr esented. (C) 1999 Published by Elsevier Science B.V. All rights reserved.