Inhibition of grain coarsening up to 1000 °C in (AlCrNbSiTiV)N superhard coatings

High-entropy nitride films were deposited by reactive sputtering from an AlCrNbSiTiV equimolar alloy target. The films persisted in single solution phase with an NaCl structure and retained their nanograin size, even after annealing at 1000 °C for 5 h. The films were superhard (>40 GPa), and have a high entropy effect that stabilizes the solution phase, and a severe-lattice-distortion effect that inhibits nanograin coarsening. The proposed inhibition mechanism for such high-entropy nitride coatings is based on thermodynamics.