Micro-Indentation of oxidized low carbon steel to evaluate properties of oxides

During hot rolling process, an oxide scale grows at the surface of steel slabs. To avoid surface defects such as embedded scale at the end of the finishing mill, descaling stands are added in the production line to remove it using high-pressure water jets. Different steel grades show different descaling capacities and final surface qualities, which may depend on composition through oxide and interface toughness. The idea of this study is to measure the latter using micro-indentation to feed thermomechanical models of the descaling process. After indentation, Focused Ion Beam (FIB) is employed to observe cracking and delamination of oxidized specimen and to calculate adhesion of oxide thanks to an analytical formula. The experimental study confirms that alloying elements have a strong influence on the adhesion of oxide film and suggests that difficult-to-descale grades are those showing a large scatter of interfacial toughness. In parallel, numerical finite element (FEM) simulations of indentation are carried out using Abaqus (R) to have a better understanding of cracking mechanism and delamination of oxide.