Modified austempering effect on bending fatigue properties of Fe-0.6C-1.5Si-0.8Mn steel

The effect of a modified austemper coupled with interrupted quenching (IQ A us) on the bending fatigue properties of Fe-0.6C-0.5Si-0.8Mn steel has been studied to determine the validity of using IQ Aus steel in possible enviro nmentally conscious material applications. The bending fatigue stress of st eel can be improved by IQ Aus: conventional austenitization at 1133 K follo wed by interrupted quenching a 533 K and then austempering at 673 K for a r equired time followed by subsequent water quenching and 473 K tempering. Th e IQ Aus steel had a triple structure consisting of carbide-free upper bain ite, 26 vol.% retained austenite and 10 vol.% tempered martensite. Compared to the conventional austemper (Con Aus), the IQ Aus increased the bending fatigue limit stress. Compared to the quench and temper (QT), the IQ Aus sh owed a significantly decreased fatigue notch factor while there was little difference between the fatigue limit stress of both steels. The results are described and discussed in terms of fractography, etc..