Thermal Stability of Retained Austenite in High-carbon Steels during Cryogenic and Tempering Treatments

A variety of quenching, cryogenic and tempering treatments were conducted to assess the effect of cryogenic treatment on the thermal stability of retained austenite (RA) during tempering processes in high carbon steel. Optical and electron scanning microscopes, transmission electron microscopy coupled with X-ray diffractions were employed to determine the morphology, fraction and carbon concentration of RA. It is confirmed that pre-cryogenic treatment is crucial which strongly affects the carbon concentration and dislocation density in RA and thus consequently the stability of RA. However, the carbon concentration is the most dominant one especially in relatively higher temperature tempering processes.