Decarburization of an Iron 0.8 w/o Carbon Alloy in the Presence of a Wustite Scale

Abstract

The decarburization kinetics have been investigated for an austenitic Fe‐0.81 w/o C alloy in the presence of a wustite scale exposed to a carbon dioxide atmosphere or vacuum at 950°C. During the stage of linear reaction kinetics in carbon dioxide, iron oxidation was approximately tenfold more rapid than carbon oxidation. The latter reaction occurred predominately with carbon dioxide rather than by reduction of wustite. The primary rate‐controlling steps in decarburization were reaction steps at the alloy surface with a small resistance possibly occurring to the passage of carbon oxides by pores in the scale. The maximum area affected by porosity in a scale was 2–3%. Under vacuum decarburization conditions, the effectiveness of the pores in the wustite scale as a means of transport for carbon oxides was dependent on its thickness and the concentration of carbon at the metal/oxide interface.