Effect of Multi-Step Austempering Treatment on the Microstructure and Mechanical Properties of a High Silicon Carbide-Free Bainitic Steel with Bimodal Bainite Distribution

The effect of multi-step austempering treatments on the microstructure and mechanical properties a novel medium carbon high silicon carbide-free bainitic steel was studied. Five different isothermal treatment processes were selected, including single-step above martensite start temperature (at 350 °C 370 °C, respectively), three kinds two-step routes (370 + 300 250 °C). In comparison with adopting process, bimodal-size distribution ferrite without obtained. Bainitic transformation studied using dilatometry both for specimens completely characterised by electron microscopy (SEM TEM), X-ray diffraction (XRD) standard tensile tests. response samples subjected to superior those treated at single temperature.