Integrated experimental and theoretical insights into the structural, mechanical, and thermal behavior of AlTiNbTaZrSiN coatings

Refractory AlTiNbTaZrSiN coatings were investigated to explore the composition-driven effects on their structure, mechanical, and thermal properties employing both experimental and computational techniques. Progressive substitution of Me (Nb + Ta + Zr + Si) in Al_1-x-zTi_x(Me)_zN (z ≥ 0.37) was found to induce a transformation from a single cubic structure to a dual cubic-wurtzite structure, with Si content identified as the primary driver of this transition. Increasing the Me content within the cubic-structured Al_1-x-zTi_x(Me)_zN resulted in a continuous increase in hardness (H), rising from ∼29.3 GPa for Al_0.45Ti_0.55N to ∼35.7 GPa for Al_0.41Ti_0.41(Me)_0.18N, accompanied by an improvement in indentation toughness. However, a rapid drop in mechanical properties was observed upon the formation of the wurtzite-AlN (w-AlN) in Al_0.40Ti_0.23(Me)_0.37N and Al_0.39Ti_0.17(Me)_0.44N. After thermal annealing, the compositional adjustments and the resulting entropy-enhanced state were shown to contribute to the delayed decomposition and age hardening in Al_0.40Ti_0.23(Me)_0.37N and Al_0.39Ti_0.17(Me)_0.44N at elevated temperatures, as supported by the thermodynamic evaluation of the integrated energy, entropy, and strain effects.