Mechanisms of hardness enhancement in CrB2 thin films with varying VB2 concentrations

Transition metal borides are well-known for their high hardness, excellent wear resistance, chemical inertness, and electrical conductivity, making them promising for a wide range of applications. Understanding the interconnections between material structure, composition, and mechanical properties is essential for designing and synthesizing effective coatings. This study systematically investigates the structural and mechanical properties of CrB2 thin films with varying concentrations of VB2 (0-10 wt%), focusing on structure, hardness, elastic behavior and deformation characteristics mechanisms through atomic force microscopy and nanoindentation measurements. The results show that increasing VB2 content leads to the formation of island cluster structures, which significantly strengthens atomic bonds and, in turn, enhances the hardness of the thin films. As particle size decreases, the higher proportion of surface atoms and increased surface energy have a more pronounced effect on the mechanical properties. In particular, the addition of VB2 up to 10 wt% in CrB2 thin films results in a marked improvement in superhard properties. 26 % increase in hardness value is also influenced directly by the changes in Young's modulus and Poisson's ratio that depend on the VB2 concentration.