Hardening mechanism and plastic deformation behavior in super-hard AlCrNbSiTiN high-entropy nitride nanocomposite coatings

The rapid development of industrial applications places severe demands on the mechanical properties of protective coatings. Unraveling the hardening mechanism and deformation behavior is essential for the design of advanced hard coatings. In this paper, a novel AlCrNbSiTiN high-entropy nitride (HEN) coating with an extremely low wear rate of 6.3 × 10⁻⁷ mm³N⁻¹m⁻¹ and super-hardness of 46 GPa was deposited. The variation of ion-bombardment energy induces the transformation of the nanocomposite structure and hardening mechanism. The plastic deformation behavior was revealed using <i>Ex situ</i> TEM observation and the MeN-Si₃N₄ nanocomposite structure is a critical contributor to the outstanding mechanical properties and resistance to deformation. Alterations of Si₃N₄ induce the transition of nanocomposite structure and hardening mechanism, and <i>Ex situ</i> TEM reveals MeN-Si₃N₄ is essential for excellent mechanical properties and resistance to the deformation of AlCrNbSiTiN coatings.