Fractographical Insight into Heat-Treated Low Carbon Microalloyed API X65 Steel Fracture Mode

In this study, low carbon microalloyed API X65 steel was fully austenized and followed by room temperature quenching with subsequent re-heating at a temperature immediate below the martensite formation starting temperature. The heat-treatment process transformed the equiaxed ferritic microstructured to acicular ferrite microstructure with intercalated retained austenite. Fractography revealed that ductile mode of failure by deformation band induced finer dimple was changed to the inclusion induced large flowery dimples assisted by large number of microcracks due to the transformation in microstructure.