Determining Retained Austenite Quantity and Composition with Heat Treatment Parameters in SAE52100 Steels
Ersoy Erişir Oğuz Gürkan Bilir Ahmet Efe Gezmişoğlu
AbstractInfluence of different austenitization conditions on retained austenite quantity and composition investigated on SAE 52100 steel. SAE 52100 steels are being widely used as bearing component regarding to their hardness and wear resistance. Traditional production cycle includes hot rolling, spheroidization, cold rolling, quenching from two phase region and tempering steps. This cycle results with martensitic matrix and undissolved course carbides. Course carbides maintain adequate wear performance but due to course carbides providing appropriate nucleation sites for crack propagation and growth this structure shows poor fatigue behavior. Previous studies showed better carbide size and distribution with experimental two step hardening cycle. This cycle results with considerable increase at retained austenite fraction. It’s well known that mechanically unstable retained austenite improves fatigue resistance in this type of steel. Transformation retained austenite to martensite caused by deformation eliminates local stresses and retards crack propagation and growth. XRD studies are carried on to determining retained austenite quantity with various austenitizing conditions. Computational simulations with Thermo-Calc and Dictra are used for predicting carbon concentration gradient of austenite during austenitization which determines retained austenite fraction at the end. A good correlation between XRD data and simulation results was obtained.