2018 Volume 58 Issue 1 Pages 123-131
To investigate the heterogeneous nucleation of graphite on rare earth non-metallic inclusions during the solidification of cast iron, Fe-4.1mass%C-2.5mass%Si and S-added Fe-4.1mass%C-2.5mass%Si-0.01mass%S alloys are contact-melted and solidified on RE2O3 (RE; La, Yb) substrates. Regarding the Fe-4.1mass%C-2.5mass%Si alloy, XRD analysis and SEM observation results show that graphite, with an overall orientation in the  direction, precipitates at the alloy/substrate interface. In addition, formation of nodular graphite with rare earth sulfides as the heterogeneous nuclei is observed in the bulk alloy. In the 0.01%S-added specimens, precipitation of graphite at the alloy/substrate interface is observed to be significantly weakened compared to reference specimens. Such precipitation behavior is considered to be due to the increased formation of nodular graphite in the bulk as a result of S addition. Based on these results, the precipitation behavior of graphite on rare earth compounds is discussed.