Unusual tempering behavior of Fe-Cr-C martensite

Abstract

The tempering behavior of an as-quenched high Cr-high C steel consisting of lath martensite, retained austenite and carbide was studied. The change in the total austenite volume fraction was monitored during tempering by in situ neutron diffraction. The results were compared with those obtained by X-ray diffraction, scanning electron microscopy/electron back scatter diffraction and transmission electron microscopy observations and ex situ neutron diffraction. The volume fraction of the blocky austenite grains increased by tempering at 573 K, whereas the thin film austenite decomposed to ferrite and cementite. The tempering behavior of the blocky austenite grains is an unusual phenomenon.