Enhancing Wear Resistance in Functionally Graded Metallic Components: Insights from Nanoindentation and Mechanical...

To manufacture metallic components with high wear resistance, treatments such as nitriding and carburising followed by quenching and tempering (NQT and CQT, respectively) are applied to various types of steel to increase the hardness (H) of the friction surface. However, the wear mechanism of the resulting functionally graded materials has not been fully understood. In this study, specimens of industrial 99.82% pure iron treated with NQT at 913 and 1033 K, and CQT at 1203 K, as well as hot-rolled sheets without heat treatment were examined by performing nanoindentation tests to measure changes in their H, reduced Young's moduli (E_r), elastic deformation energies (W_e), and plastic deformation energies (W_p) along the depth direction. The relationship between W_p/W_e and the elastic strain resistance (H/E_r) can be expressed for all specimens via the equation W_p/W_e = -1.0 + 0.16 (H/E_r)^-1. Furthermore, the obtained H/E_r av measured at 5 µm intervals based on the specimen profile and wear volume has a good correlation depending to the sliding distance, as confirmed by the results of the ring-on-plate sliding tests conducted for the carbon-treated, nitrogen-treated, and hot-rolled specimens. This study provides a new approach, using H/E_r parameters to identify the dominant factors affecting wear resistance at the initial stage of wear that may contribute to the development of wear-resistant materials.