Effect of Cooling Rate on the Eutectoid Transformation in Compacted Graphite Cast Iron

Jacques Lacaze (1) , Yannick Thebault (1) , Alexandre Freulon (1) , Wilson Luiz Guesser (2, 3)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
2 UDESC - Santa Catarina State University
3 TUPY (BRAZIL)

Differential thermal analysis has been used to characterize the effect of cooling rate on the eutectoid transformation of a compacted graphite iron. The samples were machined out from an as-cast thermal cup, austenitized at 950°C and then cooled to room temperature at various rates within the range 1−55.5°C/min. It was found that even at the highest investigated cooling rate, significant amounts of ferrite could be observed. When comparing the microstructure before and after Nital etching on samples cooled at intermediate cooling rates, it appeared that ferrite formed preferentially along the worms. This is discussed in terms of graphite shape and microsegregation and this latter seems prevalent. Finally, analysis of the thermal records was performed to characterize the temperatures for the start of the stable and metastable eutectoid reactions which confirms the eutectoid transformation sets up in compacted graphite irons as in lamellar and spheroidal graphite irons.

Mots clés: Compacted graphite cast iron; Eutectoid transformation; Graphite shape

Domaines: Génie des procédés; Matériaux

Jacques Lacaze, Yannick Thebault, Alexandre Freulon, Wilson Luiz Guesser. Effect of Cooling Rate on the Eutectoid Transformation in Compacted Graphite Cast Iron. Materials Science Forum, 2018, 925, pp.12-19. ⟨10.4028/www.scientific.net/MSF.925.12⟩. ⟨hal-01984751⟩