Abstract: Refractory high-entropy alloys (RHEAs) possess exceptional strength and thermal stability, yet their limited wear resistance under tribological stress constrains broader applications. Here, we demonstrate a reactive atmosphere-assisted laser surface treatment (RA-LST) that generates a hierarchical gradient structure in a TiZrNbMoTa RHEA, yielding a dramatic enhancement in wear performance. Cross-sectional analysis reveals the formation of a ∼25 μm-thick gradient layer, where the coarse-grained, single-phase body-centered cubic (BCC) matrix transforms into a hierarchical architecture comprising: (i) a TiN-rich surface layer, (ii) stalactite-like (Zr, N)-enriched hexagonal close-packed domains interwoven with NbMoTa-rich BCC regions, and (iii) fine (Zr, N)-rich cellular networks within the BCC interior. This gradient microstructure elevates surface hardness from ∼5.8 to ∼10.4 GPa and accommodates frictional stresses through staged deformation pathways. Moreover, a self-adaptive tribolayer emerges dynamically during sliding, promoting stress dissipation while suppressing crack initiation and propagation. Consequently, the wear rate at room temperature is reduced significantly, from 1.23 × 10^-4 to 8.95 × 10^-6 mm³/(N m). These findings establish RA-LST as a versatile strategy to design hierarchical gradient structures that impart superior wear resistance to refractory alloys.

Key words: Refractory high-entropy alloy, Laser surface treatment, Gradient structure, Cellular structure, Sliding wear