Abstract
The presence of M7C3 carbide in white iron enhances its wear resistance because of high hardness. Scanning electron microscopy (SEM) revealed its morphology as a pencil-like hexagonal structure. On the basis of the SEM observations, elemental distribution studies, and differential thermal analysis (DTA) of some heat-treated hypoeutectic white irons alloyed with Cr, Mn, and Cu, it is concluded that M7C3 carbides form as a result of attainment of a favorable condition in the liquid phase present at the austenite grain boundaries. Segregation of phosphorus in the intercellular regions and formation of a copper-rich intermetallic is responsible for the formation of this liquid phase. Austenite was found to nucleate first, followed by the nucleation and growth of M7C3 carbide in its vicinity, because of rejection of C and Cr during formation of austenite. The rosette structure generally observed is formed from the joining of M7C3 carbides by precipitation of secondary carbides.
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Kumar, V. Formation and morphology of M7C3 in low Cr white iron alloyed with Mn and Cu. J. of Materi Eng and Perform 12, 14–18 (2003). https://doi.org/10.1361/105994903770343411
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DOI: https://doi.org/10.1361/105994903770343411