Corrosion behaviours in acidic solution of spheroidal cast irons highly alloyed with nickel or cobalt. Part 1: Elaboration and microstructures of the alloys - Archive ouverte HAL Accéder directement au contenu
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Corrosion behaviours in acidic solution of spheroidal cast irons highly alloyed with nickel or cobalt. Part 1: Elaboration and microstructures of the alloys

Kamel Meridja
  • Fonction : Auteur
Patrice Berthod

Résumé

Certainly the most used metallic a lloys are the ferrous ones. Initially issued in the liquid state from the reduction of iron ore, at the exit of blast furnaces [1] the liquid cast iron, mainly constitute d of Fe but containing also significant amounts in carbon (coke) and in silicon (gangue), may be directly dr iven to the foundr y workshop to be treated then poured in moulds to solidify with the shape wishe d for the wished pieces [2] or driven to the oxygen c onverter to lose the main parts of their carbon and silicon to become liquid steel [3]. In both cases the y can be enriched with supplementary elements to obtain more or less highly alloyed cast irons or steels for achieving special microstructures and properties [5]. This can be useful to achieve new mechanical beha viours as well as improve d corrosion resistance. Alloying cast irons with new elements, foreign to the composition at the exit of blast furnace often supposes that new liquid metal treatments must be done after the addition (inoculation for help graphite nuc leation, desulphurization then magnesium treatment for promoting the spheroidal growth of graphite…). But it was also demonstrated that it is possible to take a s pheroidal graphite cast iron (SG cast iron), rapidly remelting it, adding the new element, homogenizing a short time the liquid alloy before quickly solidifying it [5]. This was attempted here to obtain SG cast irons highly alloyed to either nickel or cobalt, in order to study the properties that they are able to bring. It appears thus possible to obtain, from parts of industrial SG cast iron, spheroidal graphite cast iron highly alloyed with nickel (at least until 25 wt.% Ni) and with cobalt (at least until 50 wt.%Co), following the procedure applied here. This was also observed (at least until 50% of SG industrial cast iron) with the reference xFe(1-x)Fe alloys were also produced in parallel in order to eventually distinguish a specific role of nickel or of cobalt, farer than the simple dilution of the origin nuclei for graphite (inoculation of the initial industrial cast iron). The corrosion properties, which now remain to extensively specify (Part 2 of this work [6]), were already partly observed here, not in an aqueous solution, but in contact with nitric acid diluted in ethanol. In this way these are the Ni-alloyed cast irons which appeared the most resistant (no visible attack after 10 seconds), followed by the cobalt-richest cast iron. This will be deeper investigated later, in acidic solutions, by long immersions and/or by using electrochemical techniques.
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hal-03271532 , version 1 (25-06-2021)

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  • HAL Id : hal-03271532 , version 1

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Kamel Meridja, Patrice Berthod. Corrosion behaviours in acidic solution of spheroidal cast irons highly alloyed with nickel or cobalt. Part 1: Elaboration and microstructures of the alloys. Eurocorr 2016, Sep 2016, Montpellier, France. ⟨hal-03271532⟩
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