Effects of nitrogen flow ratio on the structure and properties of reactively sputtered (AlMoNbSiTaTiVZr)Nx coatings

Abstract

(AlMoNbSiTaTiVZr)Nx films are reactively sputtered from an AlMoNbSiTaTiVZr equimolar target under varied nitrogen flow ratio (RN). The concentration of nitrogen increases rapidly at lower RN and then saturates at around 50 at% when RN reaches 33% and above. At lower RN (0% and 3%), film structures are amorphous and their cross-sectional microstructures are featureless. When RN is 11%, FCC nitride nanocrystals coexist with the amorphous phase. At higher RN (33% and above), films exhibit a single NaCl-type FCC structure having fine column structures and nanograins. The texture of the FCC structures changes from (1 1 1) to (2 0 0) as RN increases from 33% to 66%. Enhanced hardness is observed upon the addition of nitrogen due to the strong bondings between N and target elements. Compared with reported high-entropy alloy (HEA)/nitride films deposited without bias, (AlMoNbSiTaTiVZr)Nx exhibits the highest hardness and modulus both in its alloy and nitride states. This not only confirms the effectiveness of the present alloy design but also demonstrates that HEA design could provide a new route to enhance the mechanical properties of alloy and nitride films.