Effects of nitrogen content on microstructures and mechanical properties of (AlCrTiZrHf)N high-entropy alloy nitride films

Abstract The (AlCrTiZrHf)N high-entropy alloy nitride films were synthesized by reactive magnetron sputtering. The effects of different N2 flow rates on the microstructures and mechanical properties of (AlCrTiZrHf)N films were studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), nanoindentation, coating friction and wear tester. The results show that the AlCrTiZrHf high-entropy alloy film presents an amorphous state. With the increase of the N2 flow rate, the (AlCrTiZrHf)N high-entropy alloy nitride films transform to a face-centered-cubic (FCC) structure. When the N2:Ar ratio is 5:4, the hardness and elastic modulus of the films reach 33.1 GPa and 347.3 GPa, respectively. The strengthening effect is mainly attributed to the formation of saturated metal-nitride phases and the solid-solution strengthening of various elements. Meanwhile, the (AlCrTiZrHf)N film exhibits the low friction coefficient and superior wear resistance. Based on the excellent properties of high-entropy alloy nitride films, the (AlCrTiZrHf)N film presents a potential application in protective coating.