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As-Cast microstructures of {M-30Cr-0 to 5% C} ternary alloys. Part 1: Nickel-Base alloys

Patrice Berthod, Elise Souaillat, Oph�?�?�?�?�?�?�?©lie Hestin

High carbides fractions can be easily obtained in alloys, simply by choosing sufficiently high carbon contents in presence of a carbide-former metallic element. In this study, nickel alloys containing simultaneously high contents in carbon and chromium were preliminary studied by thermodynamic calculations, then elaborated by foundry. Their microstructures were observed by electron microscopy. The Ni-30Cr alloys with less than 2wt. %C display a hypoeutectic microstructure composed of matrix dendrites and eutectic M7C3 carbides. For carbon contents higher than 2-2.5 wt. %, coarse carbides have replaced the dendrites, and the double carbides population, eutectic and pro-eutectic, can be of two natures:M7C3 andM3C2. Ifmore than 4wt.%C is present, graphite appears and the increase in carbides with carbon is limited.