Gradient design mediated wear mechanism transition in FeCoCrNi-Mo/Nb high-entropy alloy coatings for elevated-temperature tribological applications

To combat synergistic high-temperature wear-oxidation failure in critical components (e.g., gas turbines), this study designs laser-clad FeCoCrNi-Nb gradient high-entropy alloy coatings (Nb-GHEA). The monolithic gradient architecture integrating a Laves-phase-dominated surface, nanoscale eutectic transition, and ductile FCC substrate. The coating achieves oxidation resistance at 800 °C (mass gain: 0.056 mg·cm −2 ), attributed to sluggish diffusion forming an adherent Cr 2 O 3 -NbO 2 scale and dynamic Nb 4+ /Nb 5+ redox-mediated crack healing. Furthermore, it exhibits an ultra-low wear rate (9.29 × 10 −7  mm 3 ·N −1 ·m −1 ), friction coefficient (0.2207), and impact toughness (115.8 J) at this temperature. These enhancements primarily originate from multi-layer structure synergy, which transitions the dominant wear mechanism from adhesion to mild abrasion. This work establishes Nb-GHEA as a solution for critical tribological components under extreme conditions