Structural and mechanical properties of multi-element (AlCrMoTaTiZr)Nx coatings by reactive magnetron sputtering

Abstract (AlCrMoTaTiZr)Nx high-entropy films were deposited on silicon wafer and cemented carbide substrates from a single alloy target by reactive RF magnetron sputtering under a mixed atmosphere of Ar and N2. The effect of nitrogen flow ratio RN on chemical composition, morphology, microstructure, and mechanical properties of the (AlCrMoTaTiZr)Nx films was investigated. Nitrogen-free alloy film had an amorphous structure, while nitride films with at least 37 at.% N exhibited a simple NaCl-type FCC (face-centered cubic) structure. Mixed structures occurred in films with lower nitrogen contents. Films with the FCC structure were thermally stable without phase decomposition at 1000 °C after 10 h. The (AlCrMoTaTiZr)N film deposited at RN = 40% exhibited the highest hardness of 40.2 GPa which attains the superhard grade. The main strengthening mechanisms for this film were grain-size and solid-solution strengthening. A residual compressive stress of 1.04 GPa was small to account for the observed hardness. The nitride film was wear resistant, with a wear rate of 2.8 × 10− 6 mm3/N m against a loaded 100Cr6 steel ball in the sliding wear test. These high-entropy films have potential in hard coating applications.