Evaluation of Fracture Behavior of Oxide Scale Formed on Carbon Steel Using Indentation Test and Acoustic Emission Method

The fracture behavior of oxide scales formed on carbon steel with various structures was evaluated using indentation test and acoustic emission method. FeO scale on steel, which had relatively fragile and poor adhesion, became hard to crack with precipitation of fine Fe3O4 grain. However, FeO eutectoid transformation made surface of oxide scale fragile during the indentation test. This is because the volume expansion during the transformation applied tensile stress to surface Fe3O4, which became likely to crack from the surface.