Spheroidal graphite coalescence during thermal cycling in the ferritic domain of a high-silicon cast iron studied by optical microscopy and X-ray computed tomography

Mariana Alves Pegoraro (1) , Christophe Tenailleau (1) , André Ebel (1, 2) , Benoit Malard (1) , Jacques Lacaze (1)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
2 LCTS - Laboratoire des Composites Thermostructuraux

High-silicon cast irons remain ferritic at higher temperature than usual cast irons and present both better oxidation resistance and higher mechanical strength. Such a high-silicon spheroidal graphite cast iron was heat treated up to 50 h in total at 800 °C in two clifferent manners: under isothermal and cyclic conditions. Under the isothermal condition, the distribution of graphite inclusions did not vary significantly. On the contrary, temperature cycling led to spectactùar coalescence whose evolution was observed after 1000, 2000 and 3000 cycles.Quite unexpectedly, the largest graphite particles - that were growing because of coalescence - showed an irregular outer surface after 1000 cycles, which evolved in impressive dendritic instabilities and then large protuberances after 2000 and 3000 cycles. Optical microscopy andX -ray computed tomography (XCT) were used to quantitatively study these microstructural changes.

Mots clés: Alloys; Materials characterization; Optical microscopy; X-ray computed tomography; Spheroidal graphite coalescence; High-silicon cast iron

Domaines: Matériaux

Mariana Alves Pegoraro, Christophe Tenailleau, André Ebel, Benoit Malard, Jacques Lacaze. Spheroidal graphite coalescence during thermal cycling in the ferritic domain of a high-silicon cast iron studied by optical microscopy and X-ray computed tomography. Materials Today Communications, 2020, 25, pp.101422. ⟨10.1016/j.mtcomm.2020.101422⟩. ⟨hal-03165299⟩