Abstract

How oxide detachments occurred during high temperature oxidation of ametallic alloy may influence the determination of the parabolic constant kp?

Author(s): Patrice Berthod

The parabolic constant Kp is the most important kinetic constant characterizing the high temperature oxidation rate of superalloys. It is usually determined by plotting mass gain versus the square root of time which led, in the simplest cases where the mass gain kinetic faithfully followed the WagnerÂ’s law, to a slope to which Kp is related by a simple relationship. Unfortunately detachments of the external oxide scale occurred in most cases, with as results the existence of jumps in the mass gain curves. These ones become thus tricky to analyse for deducing Kp with accuracy. The topic of this work is to evaluate the impact of two parameters, the surface fraction affected by an oxide scale detachment and the instant at which it occurs, on the value of Kp determined classically, this by simulatingmass gain curves and jumps induced by scale detachment and analysing them.