Tempering response of bainitic and martensitic microstructures

Abstract

The tempering response of fully martensitic microstructures has been well characterized. However, bainitic microstructures may also be found in quenched industrial materials and the present study investigates the tempering response of fully martensitic and fully bainitic microstructures. Specific thermal cycles were developed to generate both microstructures in a boron added 0.17 wt pct carbon steel. The tempering response was assessed through dilatometry and microstructural characterization was conducted using scanning electron microscopy and Mössbauer spectroscopy. The dilatometric analysis of the tempering response of the martensitic microstructures provided information about retained austenite decomposition and cementite precipitation whereas bainitic microstructures showed a less sensitive dilatometric response during tempering likely due to the low amount of carbon in solution and absence of retained austenite as measured by Mössbauer spectroscopy.