Influence of Mo content on the friction and wear properties of gradient-structured TiVZrNbMo high-entropy alloy films

To mitigate the discrepancies between high-hardness High-Entropy Alloy (HEA) films with titanium matrix, gradient structures enable a continuous variation in mechanical properties, represent a promising approach. Herein, a novel composition gradient TiVZrNbMo HEA film was prepared, the effect of Mo on the microstructural evolution, mechanical and tribological properties was investigated. Elevated Mo content resulted in a refinement of the grain size, a reduction in lattice parameters, and enhanced solid solution strengthening. At a Mo content of 33 at.%, the gradient films achieved a maximum hardness of 9.5 GPa and demonstrated minimal wear (2.8 × 10^-6 mm³/(N·m)). The composition gradients mitigate the mismatch in modulus between the TiVZrNbMo HEA film and titanium, which provide a potential to enhance the tribological performance.