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

Abstract

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 TixZrNbTaFeBy 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 TixZrNbTaFeBy 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 Ti15.2Zr0.9Nb1Ta1.2Fe1.1B33.8 coating. The hardness of TixZrNbTaFeBy 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 TixZrNbTaFeBy 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 Ti15.2Zr0.9Nb1Ta1.2Fe1.1B33.8 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.