Short-Term High Temperature Oxidation of Lamellar Cast Iron

Abstract

The present study is focused on the oxidation behavior, at temperatures above 900 °C, of lamellar cast irons containing various amounts of species commonly present in these alloys (mainly P, S and Si) and less common metallic impurities (Cu and Cr). Oxidation kinetics were investigated from TGA tests performed in flowing air for four hours. The morphology, microstructure and composition of oxide scales were investigated by means of SEM and XRD. It was found that the oxidation kinetics and the microstructure of oxide scales strongly depend on composition and temperature. Slower oxidation kinetics is associated with the growth of oxide scales showing a two-layered microstructure consisting in an outer scale of hematite and magnetite and an inner scale of wustite and fayalite. Faster oxidation kinetics, usually linear, relates to the growth of a single stratified scale primarily composed of hematite, with a small amount of magnetite and a dispersion of silicon-rich precipitates, most likely amorphous silica.