High Temperature Oxidation of High Chromium White Cast Iron

Atmospheric high temperature oxidation behavior was studied on high chromium cast iron containing 2.2 to 4.1 % C and 19 to 26 % Cr at 953 to 1223 K. Though the Cr content of the matrix in 25 % chromium cast iron was fairly lower than that of stainless steel, the former exhibited a better oxidation resistance than the latter. Cr rich primary and eutectic M7C3, and also secondary carbide suppressed the progress of the oxidation of matrix. 25 % Cr eutectic specimens, composed of fine (matrix + M7C3) eutectic structures, showed the highest oxidation resistance. A protective continuous oxide layer of Cr2O3 was formed on the 25 % Cr specimens, while the oxide layer on the 20 % Cr specimens consisted mostly of Fe2O3.