Properties of a new TiTaZrHfW( N) refractory high entropy film deposited by reactive DC pulsed magnetron sputtering

In the last decades, refractory high entropy thin films have attracted more attention due to their superior properties at high temperatures. Besides the thermal stability, these new materials present good mechanical properties at high temperatures, which is interesting compared to conventional alloys. TiTaZrHfW(N) films are deposited by reactive magnetron sputtering in various argon/nitrogen atmospheres. Optical emission spectroscopy is performed to analyze the target poisoning conditions and optimize the deposition parameters. The nitrogen flow rate ratio RN = ΦN2/(ΦN2 + ΦAr) is varied from 0 to 29 %. XRD analyses show a phase transition from amorphous to B1(NaCl) single phased films once the nitrogen is added. For all nitrides, an out-of-plane {111} preferential orientation is observed, except for RN = 9 %, for which it changes to {200}. The morphology of the films changes from compact to columnar when the nitrogen ratio exceeds 5 %. The hardness and Young's modulus are also studied and present evolution with maximum values, 29 GPa and 257 GPa for RN = 9 % respectively. All nitrides show good thermal stability under vacuum at 800 °C for 3 h, compared to nitrogen-free metallic film, for which phase transition occurs. Nitrides show improved oxidation resistance compared to that of metallic film.