The Effects of Dual Atmosphere Exposure Duration and Temperature on the Growth of Iron Oxide on Ferritic Stainless Steels

Abstract

In this study, the oxidation behavior of two ferritic steels with different amounts of chromium is examined under dual atmosphere exposure conditions. Experiments with varying time and temperature were carried out to understand the effects of these variables and difference in chromium concentration on severity and morphology of oxidation products. Higher amounts of alloyed chromium in the steel leads to better passivation against iron oxidation. With increased exposure time, however, the passivating scale breaks down leading to iron oxide overgrowth. This phenomenon appears more pronounced at lower temperatures and complete passivation of both steels was observed at the higher temperature (700°C) after 100 h of exposure. A hypothesis with regards to the presence of hydrogen during exposure is presented along with discussion on observed oxidation behavior.