Property evaluation of Ti_xZrNbTaFeB_y high entropy alloy coatings: Effect of Ti and B contents

High entropy alloy (HEA) coatings have been widely explored due to their unique properties as compared with conventional alloy coatings. In this work, an equimolar TiZrNbTaFe HEA target and a TiB₂ target were used to fabricate six Ti_xZrNbTaFeB_y HEA alloys with different Ti and B contents. The Ti and B contents were increased by adjusting the input power ratios of TiZrNbTaFe HEA and TiB₂ targets. The (Ti + B)/(Zr + Ta + Nb + Fe) ratio of the coatings increased from 0.91 to 11.61 as the TiB₂ to ZrTiNbTaFe HEA target input power ratio increased from 1.43 to 20. The Ti_xZrNbTaFeB_y coating kept its amorphous structure while the (Ti + B)/(Zr + Ta + Nb + Fe) ratio was less than 11.61. A nanocomposite microstructure consisting of TiB₂ nanocrystallites embedded in an amorphous TiZrNbTaFe matrix was obtained for the Ti_15.2Zr_0.9Nb₁Ta_1.2Fe_1.1B_33.8 coating. The hardness of Ti_xZrNbTaFeB_y coatings increased with increasing Ti and B contents. Good adhesion properties were found for coatings with higher (Ti + B)/(Zr + Ta + Nb + Fe) ratios. Each amorphous Ti_xZrNbTaFeB_y coating enhanced the corrosion resistance of bare 304 stainless steel substrate because of the dense microstructures to block the attack of corrosive electrolytes. The nanocrystalline TiB₂ structure found in the Ti_15.2Zr_0.9Nb₁Ta_1.2Fe_1.1B_33.8 coating exhibited a potential application as a protective coating in harsh environments due to its high hardness of 21 GPa, excellent adhesion, good wear resistance, and adequate anticorrosion property.