Fabrication of TiZrNbTaFeN high-entropy alloys coatings by HiPIMS: Effect of nitrogen flow rate on the microstructural development, mechanical and tribological performance, electrical properties and corrosion characteristics

Abstract One TiZrNbTaFe and five (TiZrNbTaFe)N high entropy alloy coatings were deposited onto three different substrates using a high power impulse magnetron sputtering (HiPIMS) at different nitrogen gas flow ratios (RN2). The peak current and peak power density values of HiPIMS increased with increasing RN2. The crystalline nitride (TiZrNbTaFe)N coatings were obtained as grown using equal and higher than 10.0% RN2. The higher RN2 can promote a phase transformation from an amorphous state to face-centered cubic (fcc) structure. The fcc structured coatings exhibited a fine columnar microstructure and enhanced crystallinity. The highest hardness and reduced elastic modulus reached 36.2 GPa and 265  GPa, respectively, were found for the 32.0 at.% nitrogen contained (TiZrNbTaFe)N coating primarily due to its high residual stress and secondarily because of the formation of metal-nitride phase and the solid solution strengthening of various elements. The electrochemical properties of coatings in 3.5 wt.% NaCl aqueous solution at room temperature was studied using the potentiodynamic polarization and electrochemical impedance spectroscopy methods. We discovered that the highest corrosion polarization resistance of 3.08 ×106 Ω·cm2 was also obtained for 32.0 at.% nitrogen contained (TiZrNbTaFe)N coatings grown at RN2 of 10.0%. Based on these excellent properties, (TiZrNbTaFe)N high-entropy alloy nitride coating with 32.0  at.% nitrogen content can be used as a promising protective hard coating.