Microstructure, hardness and corrosion resistance of Al2CoCrCuFeNiTix high-entropy alloy coatings prepared by rapid solidification

Abstract

The Al2CoCrCuFeNiTix high-entropy alloy coatings were prepared by laser cladding on Q235 steel surface. The microstructure, hardness and corrosion resistance were investigated by means of scanning electron microscopy with spectroscopy (SEM/EDS), transmission electron microscopy (TEM), micro/Vickers hardness tester and electrochemical workstation. Experimental results show that the cladding coating consists of cladding zone (CZ), bounding zone (BZ) and heat affected zone (HAZ). Al2CoCrCuFeNiTix high-entropy alloy coating was mainly composed of equiaxed grain; the distribution of chemical compositions is uniform. Alloy coating exhibited high hardness due to solid solution hardening and dispersion strengthening effect, the highest surface hardness of 988 HV, about 4.5 times as much as the substrate; the passivation film on Al2CoCrCuFeNiTix high-entropy alloy coating surface made the alloy have excellent corrosion resistance in 0.5 mol/L H2SO4 solution, the alloy coatings were appearing repassivation except Ti1.0 alloy coating. The coating have good corrosion resistance in 3.5% NaCl solution because Ti elements can maintain a stable state of purification. Circular polarization curves show that the Al2CoCrCuFeNiTix high-entropy alloy coating does not appear pitting in 0.5 mol/L H2SO4 and 3.5% NaCl solutions.