Test of elaboration protocols for obtaining highly Co- or Ni -alloyed spheroidal cast irons from an industrial SGcast iron.Part B: second protocol. subpart 1: obtainedmicrostructures
The fabrication of spheroidal graphite cast irons (SG iron), also known as ductile iron, is rather complicated since it involves a series of liquid iron treatments difficult to do. For obtaining a laboratory special SG cast iron with particular chemical composition, a possible way of elaboration can be re-melting of an industrial SG cast iron together with additional the element(s) to incorporate. This was earlier successfully realized in the case of silicon. In this work these are cobalt and nickel (and also iron for comparison) which were wished to be added in equal content as iron, with additionally silicon and graphite with quantities calculated to do notmodify the final chemical composition. Unfortunately, here, the difficulty of incorporation of graphite led to increase both temperature and duration, with as result the loss of the spheroidal shape. Graphite was not nodular but its morphology as double in each alloy and varied with the nature of the added element. The metallic matrix was also dependent on the added element: ferrite-pearlitic, back centred cubic or austenitic. The responses to Nital etching, which also depended on the added element, suggest different corrosion resistance among the three alloys.