Microstructural, Mechanical, and Electrochemical Properties of Quenched and Partitioned 3 wt% Mn Steel

Herein, an attempt has been made to investigate effect of C and Mn partitioning during quenching and partitioning heat-treatment process on microstructure, mechanical, and electrochemical properties of experimental 3 wt% Mn steel. The quenching and partitioning heat-treatment process was applied to the experimental steel with varying partitioning time periods ranging from 15 to 120 s at a constant partitioning temperature of 425 degrees C. The partitioning time period of 15 s resulted in a high volume fraction of supersaturated lath martensite with a small volume fraction of retained austenite. With increasing partitioning time period to 45-60 s, diffusion of C and Mn from martensite to retained austenite occurred resulting in the formation of decreased volume fraction of martensite phase with a reduced carbon and increased volume fraction of retained austenite phase with increased carbon. Partitioning for 90 s produced a moderate volume fraction of both lath martensite and retained austenite phases with nucleation of secondary phase, epsilon carbides. This phase transformation provided an optimum combination of 21% improved Vickers hardness and threefold improved impact toughness compared to as-received steel. Electrochemical properties of quenched and partitioned 3 wt% Mn steel were also evaluated in a 3 wt% NaCl solution. The highest corrosion resistance was achieved after prolonged partitioning of 120 s, whereas slightly low corrosion resistance was achieved after partitioning of 90 s.

Automated summary

This study investigates the effects of C and Mn partitioning on microstructure, mechanical, and electrochemical properties of experimental 3 wt% Mn steel during quenching and partitioning heat-treatment process. Different partitioning time periods resulted in varying volume fractions of martensite and retained austenite phases, with the formation of epsilon carbides. The optimal combination of increased hardness and impact toughness was achieved with a partitioning period of 90 seconds, along with improved corrosion resistance in a 3 wt% NaCl solution.