NbMoCrTi_xAl_y high entropy alloy (HEA) films were fabricated on Ti6Al4V substrates using magnetron sputtering technique, and their composition, microstructure, mechanical performance, and fretting wear behavior were systematically studied. With increasing Ti and Al concentrations, the films exhibited a stable single-phase body-centered cubic (BCC) structure, aligning closely with the thermodynamic calculations. The film hardness initially rose to a peak of 16.54 GPa, primarily driven by grain boundary strengthening and densification, before declining with further compositional changes. Fracture toughness improved to 2.49 MPa·m^1/2 due to Ti-induced toughening but decreased as result of Al-induced embrittlement. At a 50 μm displacement amplitude, fretting of the Ti6Al4V substrate occurred in partial slip regime, forming an annular wear scar with fatigue wear and abrasive wear as the dominant mechanisms. By comparison, the HEA films exhibited mixed slip behavior characterized by localized cracking or delamination at the contact center, with fatigue wear being the predominant mechanism. Notably, optimized films demonstrated exceptional abrasive wear resistance while effectively mitigating fatigue wear, owing to their high hardness and relatively improved fracture toughness. At a 150 μm displacement amplitude, both the substrate and films entered the gross slip regime, producing elliptical wear scars. However, the films were prone to failure under the combined effects of fatigue wear and abrasive wear. This could be attributed to their limited thickness and inadequate toughness, which result in low load-bearing and strain accommodation capacities.

中文翻译：

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磁控溅射法制备的 Ti6Al4V 钛合金薄膜的磁管喷溅制备的 NbMoCrTixAly 高熵合金薄膜的微动磨损行为

采用磁控溅射技术在 Ti6Al4V 衬底上制备了 NbMoCrTi_xAl_y 高熵合金 （HEA） 薄膜，并系统研究了其成分、微观组织、力学性能和微动磨损行为。随着 Ti 和 Al 浓度的增加，薄膜表现出稳定的单相体心立方 （BCC） 结构，与热力学计算密切相关。薄膜硬度最初上升到 16.54 GPa 的峰值，主要由晶界强化和致密化驱动，然后随着成分的进一步变化而下降。由于 Ti 诱导的增韧，断裂韧性提高到 2.49 MPa·m^1/2，但由于 Al 诱导的脆化而降低。在 50 μm 位移幅值下，Ti6Al4V 衬底在部分滑移状态下发生微动，形成以疲劳磨损和磨粒磨损为主要机制的环形磨损疤痕。相比之下，HEA 薄膜表现出混合滑移行为，其特征是在接触中心出现局部开裂或分层，疲劳磨损是主要机制。值得注意的是，优化的薄膜表现出优异的耐磨性，同时由于其高硬度和相对改进的断裂韧性而有效减轻了疲劳磨损。在 150 μm 的位移幅度下，基底和薄膜都进入粗滑状态，产生椭圆形磨损疤痕。然而，在疲劳磨损和磨粒磨损的共同作用下，薄膜容易失效。这可能是由于它们的厚度有限和韧性不足，导致承载和应变承受能力低。