Abstract: The present study investigates the tempering response of bainitic microstructures isothermally transformed at 450 and 525 oC and a fully martensitic microstructure. A boron added 0.17 wt pct carbon steel with additions of Mo and V for secondary hardening was investigated. Thermal cycles to generate bainitic microstructures were developed based on dilatometry data. Microstructural characterization was performed using scanning electron microscopy and Mössbauer spectroscopy. Non-isothermal tempering provided information about austenite decomposition and cementite precipitation. Stages II and III of tempering shifted to higher temperatures for the bainitic microstructures as compared to the martensitic sample. Vickers micro-hardness assessed differences in peak hardening for high temperature tempering for the three microstructures. The bainitic microstructure transformed at 525 oC presented slower secondary hardening than the other conditions.
Authors: I. Vieira, D.L. Williamson, and E. De Moor
Keywords: Tempering, Bainite, Dilatometry, Mössbauer Spectroscopy