In-situ characterization of tempering behaviors and alloying effects on tempering kinetics in high-carbon martensitic steels

Abstract

As-quenched martensite in carbon steels needs to be tempered to restore its ductility and toughness for practical applications. During tempering, a series of reactions causing changes in microstructure and properties are known to occur. In this study, in-situ neutron diffraction was combined with traditional calorimetric and dilatometric analyses to investigate the tempering behaviors and the effects of common alloying elements, i.e., Mn, Cr, Si, Al, on the kinetics in high-carbon martensite during continuous heating. The experimental results revealed that carbon clustering/segregation (0th stage) and metastable carbide precipitation (1st stage) were retarded by Al and Cr additions. Moreover, austenite decomposition (2nd stage) was retarded by Mn and Cr additions in the early step, whereas Al and Si additions also contribute to delaying the kinetics in the late step.