Structure and Electrochemical Properties of Laser Cladding Al₂CoCrCuFeNiTi_x High-Entropy Alloy Coatings

Al₂Co_xCrCuFeNiTi high-entropy alloy coatings were prepared on Q235 steel by laser cladding. The structure was tested by scanning electron microscopy; the corrosion resistances of the alloys were tested by electrochemical workstation. The results show that the microstructures of Ti_2.0 high entropy alloy are mainly equiaxed grains, spherical particles, white particles and "plum blossom" particles are distributed on it, columnar grains are located near the bonding zone. The corrosion resistance of Al₂CoCrCuFeNiTi_x high-entropy alloy coatings in 1 mol/L NaOH and 0.5 mol/L HCl solutions are excellent. In 1 mol/L NaOH solution, compared with Q235 steel, the corrosion current density of the coating decrease by 5 orders of magnitude, the corrosion potential increased by 0.03–0.34 V. In 0.5 mol/L HCl solution, compared with Q235 steel, the corrosion current density of the coating decreases, the corrosion potential increased by 0.06–0.14 V. With the increase of Ti content, the corrosion resistance of Al₂CoCrCuFeNiTi_x high-entropy alloy coating in 0.5 mol/L HCl solution is enhanced, while, in 1 mol/L NaOH solution, the corrosion resistance of the coatings decreased. Cyclic polarization curves showed that negative hysteresis loops appeared in Ti_0.5 high-entropy alloy coating in 1 mol/L NaOH solution and Ti_2.0 high-entropy alloy coating in 0.5 mol/L HCl solution, which indicated that the coatings has excellent pitting corrosion resistance.