Enhanced high‐temperature wear and erosion resistance of hard‐yet‐tough AlCrSiN coatings via Nb addition

Abstract Achieving the simultaneous optimization of high hardness and fracture toughness remains a critical challenge for protective coatings operating under extreme conditions. This study systematically investigates the effect of Nb alloying on the microstructure and properties of AlCrSiN coatings. It was demonstrated that the addition of an appropriate amount of Nb significantly enhances fracture toughness while maintaining high hardness, overcoming the inherent strength‐toughness trade‐off in hard coatings. Density functional theory calculations revealed that Nb solid solution enhanced metallic bonding characteristics by broadening the spatial distribution of delocalized electrons, elucidating the fundamental mechanism for the toughness improvement. Nb alloying also improved the high‐temperature performance of the coatings. By suppressing the precipitation of the soft w‐AlN phase, the thermal stability was elevated to 1100°C, enabling excellent wear resistance to be retained even at 800°C. The Nb‐content‐modulated hardness–toughness synergy was identified as the determining factor for the erosion resistance, driving a transition in the erosion failure mode from brittle fracture to a ductile wear‐dominated process. This research provides a crucial foundation for designing and fabricating tough–hard integrated physical vapor deposition coatings with superior wear and erosion resistance.