THE PARTITIONING OF SUBSTITUTIONAL SOLUTE ELEMENTS DURING THE TEMPERING OF MARTENSITE IN CR AND MO CONTAINING STEELS

The partitioning of substitutional solute elements between cementite a nd ferrite during the tempering of martensite both in a commercial 2.2 Cr1Mo0.15C wt% steel and in a novel 2.2Cr1Mo0.4C wt% steel has been st udied using atom probe field ion microscopy. No partitioning of Cr, Mo and Mn was observed between the cementite and ferrite in the early st ages of tempering. No concentration spikes of substitutional solute el ements were found at the transformation interface on an atomic scale. The enrichment of Cr, Mn and Mo in the cementite during prolonged agei ng, before the onset of soft impingement, was found to be the same in both the low and high carbon alloys. The results provide further suppo rt for the theory that cementite precipitates from supersaturated ferr ite via a paraequilibrium displacive transformation mechanism.