Synthesis and characterization of super-hard AlCrTiVZr high-entropy alloy nitride films deposited by HiPIMS

Abstract

Super-hard AlCrTiVZr high-entropy alloy (HEA) nitride films were synthesized by high power impulse magnetron sputtering (HiPIMS) without external heating. The effect of N2 gas low rate (FN), ranging from 0 sccm to 20 sccm, on the HiPIMS plasma discharge characterization, element concentration, deposition rate, microstructure, cross-sectional morphology, residual stress, and mechanical properties of films were explored. Results show that increasing FN increases the HiPIMS discharge current, accompanying with the decreased deposition rate. The saturated nitride (AlCrTiVZr)N films were obtained at FN = 8 sccm and higher, which exhibit a simple NaCl-type FCC structure. A continuous variation in the microstructure, from amorphous to columnar crystal structure, has been observed for these nitride films. It is discovered that the moderate FN of 0 sccm to 12 sccm leads to an enhanced bombardment with high-energy particles due to the increased plasma density, while the bombardment effect is weakened because of the decreased plasma energy as the FN is increased further. The nitride films deposited at FN = 12 sccm have super-hardness of 41.8 GPa and low wear rate of 2.3 × 10−7 mm3/Nm. Meanwhile, a change of preferred orientation from (2 0 0) to (1 1 1) is presented as the FN increases from 12 sccm to 20 sccm.