Slightly hypereutectic grey irons (< 4.5%CE), solidified in resin and metal moulds, after an addition of iron powder, either alone or with Ca,Ba,Al-FeSi inoculation (double treatment) were characterized by structure. Iron powder had a role in limiting the carbide presence, while the supplementary inoculation led to the fewest carbides in metal mould samples. No carbides were in resin mould solidification, while graphite morphology progressed from (C + B) in the base iron up to the type (B + A) in double treated iron. Polygonal (Mn,X)S compounds acting as graphite nuclei, whose characteristics depended on the applied treatment, were found: larger size/low compactness [base iron], irregular polygonal with tendency to the highest size and complex morphology [iron powder treatment] and compact polygonal/smallest size [double treatment]. Iron powder has a negative influence on the graphite nuclei and eutectic cell characteristics, but favours austenite dendrite formation, as a reinforcement for eutectic cells. It has a limited graphitizing effect, witnessed only at high cooling rates. A double addition [iron powder + inoculant] appears to be an efficient treatment, with beneficial effects on both the austenite and graphite nucleation, affecting the final structure and chill tendency.