The Influence of Different Coatings on the Graphite Degeneration in the Superficial Layer of the Iron Castings

Résumé

The main objective of this experimenal reserch is to investigate new possibilities for reducing the graphite degeneration phenomenon in the superficial layer of iron castings.
For the experiment, a spheroidal graphite cast iron was poured in standard Quik-Cup moulds covered with various types of coatings. The sources of sulfur and oxygen used for coatings were based on FeS2 and Fe2O3, respectively. After applying the coatings with sulfur or oxygen sources on the inner surface of the cups and after drying them, coatings based on iron powder and carbon containing powder respectively, were applied to block sulfur or oxygen access from the mould to the liquid iron. The coatings effect was evaluated by measuring the thickness of graphite degenerated surface layer and also by graphite nodularity and graphite shape factors deplating in the surface layer of the cast samples. The experimental results show a protective effect of the coating based on iron powder against the sulfur source while the coating based on carbon containing powder exerts a protective effect against the oxygen source.