metallography dot com logo This is a continuation of the article by Janina Radzikowska, Senior Metallographer, The Foundary Research Institute (Instytut Odlewnictwa) Kraków, Poland . It was originally published by Buehler in Tech-Notes, Volume 2, Issue 2 and is reproduced here with the kind permission of the Editor, Mr. George Vander Voort, Director, Research and Technology, Buehler Ltd..

Nodular Iron
Ductile iron specimens can have a wide range of matrix structures depending upon composition and as-cast cooling rate. Figure 14 shows a fully ferritic matrix after etching with 4% nital. Figure 15 shows a specimen with a pearlitic matrix and ferrite surrounding the nodules, while Figure 16 shows an example where a very small amount of ferrite remains around each nodule.
ferritic matrix ductile iron 100x Figure 14. Fully ferritic matrix (note ferrite grain boundaries) of a ductile iron specimen etched with 4% nital, 100x.
ductile iron w/ferrite and pearlite 100x Figure15. Ductile iron specimen with substantial amounts of ferrite and pearlite etched with 4% nital, 100x.
ductile iron w/pearlitic matrix 100x Figure 16. Ductile iron specimen with a pearlitic matrix and a small amount of ferrite surrounding the nodules etched with 4% nital, 100x.

White Cast Iron

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