Abstract
The formation and growth behavior of decarburized layer in spheroidal cast iron were investigated through heat-treatment at 973 to 1373 K for 86.4 to 345.6 ks in a steel pot with Fe and FeO powders.
The spheroidal graphite particles in the cast iron were found to disappear above the critical temperature of about 930 K, but below this critical temperature, disappearance was hardly observed and a FeO film was found to form on the surface. The Fe matrix phase did not oxidize and was stable at all test temperatures, since its affinity for CO2 gas is lower than that for carbon atoms.
It is presumed that at higher temperatures, the disappearance process of spheroidal graphite particles is controlled by the diffusion of carbon atoms through the matrix to the surface, and carbon atoms on the surface are removed by the generation of CO gas. However at lower temperatures, the FeO film is considered to form on the surface due to the easy formation of FeO.
