Spallation study of chromia scales thermally grown on pure chromium in synthetic air

Abstract

Pure chromium oxidized at 900 °C in synthetic air (p(O2) ~ 0.2 atm) during 30 min gives a chromia scale presenting significant spallation. Contrary to what has recently been observed at lower oxygen partial pressure (10−12 atm) Latu-Romain et al. (2018) [1, 2] showing a debonding of the scale localized at the metal/oxide interface, the decohesion in the present conditions occurs inside the oxide. Specifically, the separation of the scale takes place at the interface between an internal equiaxed subscale and an external columnar subscale. Thanks to theirs semiconducting properties (conduction and bandgaps) these subscales have been studied with photoelectrochemical techniques at macro- and micro-scales.