High-Temperature Corrosion of Cast Irons and Cast Steels in Dry Air

High Temperature Corrosion of Cast Alloys in Exhaust Environments I-Ductile Cast Irons

“…3a. However, voids, left by the oxidized graphite nodules, could not be seen, indicating that the oxide nodules and pits nucleate primarily at the graphite nodules as shown in a previous study including the oxidation kinetics for this alloy in dry air [1]. The outer Fe oxide then spread laterally to cover the rather thin Si-rich basal oxide.…”

“…Segregation is common in cast irons [18][19][20], graphitizing elements (Si, Ni, Cu,…) segregate close to the graphite nodules and solidify first whereas carburizing elements (Cr, Mo, Mn,…) are more likely to be enriched in the cell boundaries. For the SiMo studied here, such segregations have been found [1]. Furthermore, some Mo-rich (M 6 C) carbides were present in eutectic cells boundaries as well as some spherodized pearlite.…”

“…Furthermore, the volumetric changes associated with the phase transformation may promote cracking of the oxide scale [1,5] and lead to poor oxidation behavior. Still, the oxidation behavior remains interesting, first since 850°C is a reasonable peak temperature for diesel engines and, second to improve the general knowledge of the behavior of cast irons for example at very high temperature upon specific heat treatments [31].…”

“…The materials under investigation are four commercial cast alloys intended for exhaust systems of trucks and cars. Preliminary reference tests were performed in dry air [1]. It was shown earlier that the very coarse microstructure of these alloys, such as coarse carbides at the interdendritic regions as well as segregations of alloying elements through dendrites, did affect the oxidation behavior of the casting.…”

AES characterization of oxide grains formed on ductile cast irons in exhaust environments

“…16 The present study showed that the general oxidation features were similar in a diesel environment. For both alloys and gases the outer oxide consisted of nodules of haematite and magnetite, nucleated at the graphite nodules, that almost covered the alloys.…”