Doughnut-like Cementite Formed on the {110} Surface of an Fe-3%Si Single Crystal under High Temperature Carburizing

Abstract

High temperature carburization was done using the {110} surface of an Fe-3%Si single crystal. The carbide morphology of specimen surface was observed by the scanning and transmission electron microscopes.
Doughnut-like cementite (Fe₃C) of 50-200 nm in carburizing temperatures of 1173-1273K was formed on the {110} surface of an Fe-3%Si single crystal, and they formed with the colonies of the fine particles of about 2-5 nm. The preferential formation of Fe₃C was quite different from the graphite formation that occured only under the high temperature carburization of past experiments.
The orientation relationship between the Fe₃C and iron matrix is considered to be [002]_Cementite//[011]_Fe. This relationship was consistent with that observed in the precipitation of Fe₃C during the tempering of steel by Nishida and Tanino.
It is considered that the {110} surface of an Fe-3%Si single crystal under the high temperature carburization formed with characteristic morphology of doughnut-like Fe₃C, due to the preferential formation of the coherency for the crystallographic plane of (011)_Fe and (002)_Cementite.