Microstructure, mechanical and corrosion properties of reactively sputtered (TiVCrZrNbMo)N high-entropy nitride coatings

High-entropy coatings (TiVCrZrNbMo)N were prepared using reactive DC magnetron sputtering to study the effect of nitrogen content on microstructure, mechanical and corrosion properties. The coatings were prepared using a single powder-metallurgical target with an equimolar elemental composition at various R N = N 2 /(Ar + N 2 ) flow ratios (0–50 %). The nitrogen content in the coatings varied between 0 and 51 at.%. The nitrogen-free coating exhibited an amorphous structure with featureless to fine-fibrous cross-sectional morphology, while the nitride coatings showed an fcc structure with columnar cross-sectional morphology. The coating deposited at a 30 % nitrogen flow ratio exhibited the maximum hardness (30.9 GPa) and elastic modulus (267 GPa). To study corrosion resistance, we conducted potentiodynamic polarization measurements of R N = 0, 10 and 40 % coatings in 0.1 M H 2 SO 4 . The metallic coating showed the lowest corrosion current density (0.18 μA/cm 2 ) and a stable passivating behavior up to 2.0 V vs. Ag/AgCl. The nitride coatings exhibited higher corrosion current density (6.0 μA/cm 2 for the 10 % coating and 1.3 μA/cm 2 for the 40 % coating) and underwent active corrosion, as indicated by the formation of a thick oxide layer. To further understand the corrosion behavior, we conducted X-ray photoelectron spectroscopy (XPS) on the coatings before and after the corrosion tests. It showed that the metallic coating formed a thicker native oxide layer than the nitride coatings prior to corrosion tests. Furthermore, the nitrogen-free coating contained a high content of passivating Nb (58 at.%) on the surface after the corrosion, which contributed to its higher corrosion resistance. • Max hardness (30.9 GPa) at 30 % N 2 flow ratio in (TiVCrZrNbMo)N coatings. • Nitrogen-free coating showed superior corrosion resistance in H₂SO₄. • Structure changed from amorphous to fcc with increasing nitrogen content.