HiPIMS and RF magnetron sputtered Al0.5CoCrFeNi2Ti0.5 HEA thin-film coatings: Synthesis and characterization

High entropy alloy (HEA) thin-film coatings have gained popularity in surface engineering applications because of their excellent physical, mechanical, and electrochemical properties. Several factors affect thin-film coating density and microstructure, but most notably, the energy of the species impacting the substrate (adatoms); therefore, the deposition process is crucial. Hardness, wear resistance, toughness, corrosion-resistant, and high/low-temperature behavior can be significantly influenced by the microstructure of thin-film coatings. In radio frequency (RF) magnetron sputtering, plasma can be maintained throughout the chamber at lower pressure, so fewer ionized gas collisions occur, and coatings are deposited more efficiently. In comparison, the high-power impulse magnetron sputtering (HIPIMS) coating process produces much denser, harder, and smoother coatings than conventional thin-film deposition techniques. This study utilized RF magnetron sputtering and HiPIMS techniques to deposit Al0.5CoCrFeNi2Ti0.5 HEA thin-film coatings. The coatings presented an FCC structure with a (111) preferred orientation, and their surfaces changed from nodular to fine microstructures. The crystallite sizes and surface roughness decreased to 13.27 and 1.33 nm, respectively, based on FWHM and AFM analyses. The lower working pressures were beneficial for obtaining coatings with good properties. Furthermore, the Al0.5CoCrFeNi2Ti0.5 HEA thin-film coatings improved the corrosion resistance of the SS 304 substrate. In summary, HiPIMS and RF magnetron sputtering processes allow for better control of the properties of Al0.5CoCrFeNi2Ti0.5 thin-film coatings, enhancing their potential use in extreme environments.