Progressive entropy engineering in AlTiHfNbTaZrN: Achieving superior thermomechanical properties through lattice distortion and thermodynamic kinetic factors

High-entropy nitride coatings garnered significant attention by overcoming the earlier thermal decomposition of TiAlN. Combining DFT calculations and experimental studies, we demonstrate all AlTiHfNbTaZrN coatings adopt a rock salt structure, driven by energetic preference and entropy stabilizing. Increasing Me content (Me=Hf+Nb+Ta+Zr) enhances hardness progressively from ∼28.4 GPa of Al_0.45Ti_0.55N to ∼36.9 GPa of Al_0.38Ti_0.14(Me)_0.48N, attributed to lattice distortion. Toughness improvements correlate with Ta/Nb-induced metallic bonding. Thermal stability improves with peak hardness at ∼37.9 GPa for Al_0.38Ti_0.14(Me)_0.48N after annealing to 1100 °C, surpassing ∼32.8 GPa of Al_0.45Ti_0.55N after 900 °C. Decreased activation energies indicate no hysteretic diffusion effect with increased entropy and distortion, while Me substitution strengthens ionic bondings with nitrogen to offset lattice expansion and brings increased average diffusion energies for non-Al metal atoms. Furthermore, greater strain energy between c-AlN and parent nitrides hinders the precipitation of Al atoms. These entropy-engineered coatings outperform TiAlN, making them ideal for cutting tools.