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

• Published in: Materials science forum Vol. 925; pp. 12 - 19
• Main Authors: Thébault, Yannick, Lacaze, Jacques, Freulon, Alexandre, Guesser, Wilson Luiz
• Format: Journal Article
• Language: English
• Published: Pfaffikon Trans Tech Publications Ltd 01.06.2018; Trans Tech Publications Inc
• Subjects: Cast iron; Chemical and Process Engineering; Cooling; Cooling effects; Cooling rate; Engineering Sciences; Eutectoid reactions; Graphite; Materials; Product design; Graphite Shape; Eutectoid Transformation; Compacted Graphite Cast Iron; Eutectoid transformation; Graphite shape; Compacted graphite cast iron
• ISSN: 0255-5476; 1662-9752; 1662-9752; 1662-9760
• DOI: 10.4028/www.scientific.net/MSF.925.12

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.