Exploring the effect of Ti and Al contents on the microstructural, mechanical, and corrosion resistance features of VNbMoTaWTiAlN refractory high entropy alloy coatings

High entropy alloys (HEAs) are a class of novel multicomponent alloys comprised of five or more elements in a single phase through entropy maximization. This work prepared five refractory-based (VNbMoTaWTiAl)N nitrogen-doped high entropy ally (RHEAN) coatings with various Ti and Al chemical compositions through a high power impulse magnetron sputtering technique. The effects of variable atomic percentage ratios of Ti and Al on the chemical composition, phase, microstructure, mechanical properties, and anticorrosion behaviors of the RHEAN coatings were studied. The work showed that all the coatings were amorphous due to the high ion bombardment effect by the high-energy HiPIMS plasma. The crystalline structures of coatings were destroyed and changed into amorphous by such high-energy ion bombardments. The variation of input powers of the TiAl target altered the film thickness, chemical composition, mechanical and corrosion resistance of the coatings. Meanwhile, the coating with the Ti, Al, and N ratios of 1.2, 0.9, and 1.0 showed the highest hardness of 14.6 GPa and a corrosion resistance 6.33 times better than bare 304 stainless steel, which presented a potential candidate for crucial corrosive environment applications.