Preliminary study on kinetics of carbon partitioning in a high Ni Q&P steel

Quenching and Partitioning (Q&P) treatment is a novel process to produce advanced high-strength steel. It is relatively difficult to investigate kinetic processes of the partitioning which normally complete after tens of seconds. Since the Mf (martensitic transformation finish temperature) of medium-carbon steels with high Ni content (9.8 wt%) is under room temperature, the kinetics of carbon partitioning can be studied around room temperature. In this study the carbon partitioning for a high Ni steel was investigated by means of Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analyzer (DMA) and X-ray Diffraction (XRD). The activation energy of carbon partitioning estimated from the DSC is 1.02 eV (98 kJ/mol) which is comparable with DMA result. The frequency dependence anelastic peaks observed in DMA measurement was also discussed in correlation with Snoek-Koster-like relaxation in high strength steels containing considerable residual austenite and martensite phases.

► Partitioning of medium-carbon steels with high Ni content (9.8 wt%) was studied. ► Kinetics of partitioning was investigated by Dynamic Mechanical Analyzer. ► Frequency dependent feature was correlated with Snoek-Koster-like relaxation.