Nanoscopic origin of the dissipative friction forces on a diamond tip sliding on magnetite surfaces

Fundamental understanding of friction forces at the micro/nanoscale continues being a challenge in tribology. This work reports on the friction behavior of the outermost magnetite layers grown on a nitrided ferrous alloy studied by two different and independent experimental methods: nanoindentation followed by unidirectional sliding and friction force microscopy. Macroscopic mechanical properties involving hardness (H) and Young modulus (E), such as the plastic deformation parameter (H3/E2) and the elastic strain to failure (H/E), as well as surface roughness cannot explain the lack of influence of the friction coefficient on the outermost magnetite layer thickness. Moreover, the observed energy dissipation phenomenon is consistent with phononic non-conservative damping forces.