Microstructure and tribological properties of (AlCrTiV)Nx high-entropy alloy films prepared by magnetron sputtering

Abstract

High-entropy alloy (HEA) films of (AlCrTiV)N_x with varying N content were deposited on 316 substrates using magnetron sputtering technology. The aim is to examine the influence of N content on the microstructure, mechanical properties, and tribological performance of the films. Results reveal that the introduction of N facilitates the transformation of the films from an amorphous state to a single FCC phase structure. As the N₂ flow rate increases, a columnar crystal structure emerges in the film cross-section, accompanied by a decrease in film thickness and a reduction in grain size. During the experimentation, the four metal elements (Al, Cr, Ti, V) combine with N to form quaternary nitrides (Al, Cr, Ti, V)N, which alter the surface morphology and quality of the films, resulting in increased surface roughness. Following the introduction of N, the hardness and elastic modulus of the films are enhanced; however, both properties exhibit an overall decreasing trend with rising N content. The maximum values, recorded at the N₂ flow rate of 2 sccm, are 14.6 GPa for hardness and 298.5 GPa for elastic modulus. At this flow rate, the friction coefficient is 0.257, while the wear rate reaches its minimum value of 3.5 × 10⁻⁶ mm³/N·m, indicating optimal anti-friction and wear resistance performance. As the N₂ flow rate increases, the wear mechanism transitions from oxidative wear to a combination of oxidative and abrasive wear. Notably, Cr₂O₃ constitutes the largest proportion of the wear debris products, attributable to its strong oxidation properties.