Oxidation and Thermal Cracking Behavior of Compacted Graphite Iron under High Temperature and Thermal Shock

Compacted graphite iron (CGI) was subjected to high-temperature oxidation and subsequent thermal shock to investigate its oxidation and thermal cracking behavior. The two experiments were conducted to a maximum temperature of 650 °C in air. Mass changes and micro-observations were made during the experiments. Results showed that the oxidation kinetics of CGI followed the parabolic rate law approximately over three stages. The oxidation behavior of CGI showed special mechanism owing to the existence of graphite. The interconnected graphite structure contributed to the inner iron oxidation and decarburization through the graphite–matrix interface. It was found that thermal cracks always nucleated on the surface stress concentration areas. A mutually reinforcing effect was presented between thermal cracking and oxidation. In the thickness direction, the interconnected graphite-oxide network was detected, and it would act as the potential path for thermal crack propagation during subsequent thermal shock cycles.