Characterization of cosputtered (TiZrHfY)Nx films

Abstract

Medium-entropy TiZrHfY alloy films and corresponding nitride (TiZrHfY)Nx films were fabricated through cosputtering. The Ti0.24Zr0.23Hf0.27Y0.26 film had the form of a hexagonal close-packed (HCP) solid solution with a mixing enthalpy of 9.09 kJ/mol, mixing entropy of 11.50 J/mol·K (1.38 R), atomic size difference of 7.72 %, and valence electron concentration of 3.73. Moreover, this film had a hardness of 6.0 GPa and an elastic modulus of 106 GPa. (TiZrHfY)Nx films with various stoichiometric ratios (x) were fabricated by adjusting the reactive gas flow ratio fN2 [N2/(N2 + Ar)] in the range 0.1–0.7. Adding N to the TiZrHfY matrix resulted in a change of phase from an HCP structure to a face-centered cubic phase. The (Ti0.23Zr0.18Hf0.24Y0.35)N0.71 film (with fN2 = 0.2) exhibited the most favorable mechanical properties, having a hardness of 19.1 GPa and an elastic modulus of 244 GPa. Moreover, the film had the highest critical loads (LC3 = 46.6 N) among the films analyzed in the scratch test. The anticorrosive properties of the TiZrHfY and (TiZrHfY)Nx films were evaluated using potentiodynamic polarization curves, obtained in 3.5 wt% NaCl aqueous solution. High polarization resistance of 1.1 × 106 Ω·cm2 was obtained for the (Ti0.23Zr0.18Hf0.24Y0.35)N0.71 film, which was 145 times higher than that of the bare SUS420 substrate. The (Ti0.23Zr0.18Hf0.24Y0.35)N0.71 film had the most favorable mechanical and anticorrosive properties of the surveyed (TiZrHfY)Nx films.