Abstract
(Al 1.5 CrNb 0.5 Si 0.5 Ti)N x high-entropy nitride coatings were designed and investigated in this study. Nitride coatings are deposited under a sufficient amount of nitrogen at 415°C on Si by direct current magnetron reactive sputtering from a non-equimolar Al 1.5 CrNb 0.5 Si 0.5 Ti high-entropy alloy target. The effects of substrate bias (V s ) on film structure and mechanical properties are studied. All these coatings have a single NaCl-type face-centered cubic structure and nearly stoichiometric ratio of (Al 1.5 CrNb 0.5 Si 0.5 Ti) 50 N 50 . A distinct refinement of microstructure of the films is observed when V s varies from 0 V to - 100 V. Typical columnar structure transits into a dense and featureless structure and grain size decreases from 70 nm to 5 nm. Similar refinement remains at larger bias(- 150 or - 200 V). At the same time, the residual compressive stress increases from near zero to - 3.9 GPa at - 150 V and then decreases to - 3.2 GPa at - 200 V. The hardness increases from 12 GPa at 0 V, peaks at 36 GPa at - 100 V, and then decreases to 26 GPa at - 200 V. The structural evolution strengthening mechanism are discussed and compared with equimolar high-entropy nitrides. © 2012 Elsevier B.V. All rights reserved.