Nucleation and growth of graphite particles in ductile cast iron

Abstract Samples taken from three commercial runs of nodular cast iron, obtained from the same base metal, same nodularizing alloy, but different inoculants were studied. The percentages by weight of inoculant and nodularizing alloy were, respectively, 1.0% and 1.3%. In this way the nucleation and the growth of graphite nodules were studied by microstructural analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). In this way, we observed that the growth sequence of the graphite nodules was associated to the formation of complex silicates rich in aluminum, calcium and barium around the graphite cores, generating an interface favorable to the heterogeneous graphite solidification from these particles of size larger than critical radius. Therefore, the race 1 sample inoculated with FeSi75% presented the lowest amount of nodules/mm2 and, consequently, less elongation, since there is a direct relation between the elongation and the number of nodules/mm2.