Evolution in microstructure and corrosion behavior of AlCoCrxFeNi high-entropy alloy coatings fabricated by laser cladding

AlCoCrxFeNi high-entropy alloys (HEAs) coatings were prepared on the surface of 45# steel by laser cladding with different contents of Cr (x = 0.50, 0.75, 1.00, 1.50, 2.00). A model was established to estimate the content of each component in the coatings, based on which three parameters including mixing entropy (△Smix), net driving factor (Ω) (Ω = Tm⋅△Smix/|△Hmix|Ω=Tm⋅Smix/|△Hmix|), and atomic size difference (δ) were calculated to precisely predict phase constituents in the coatings. The evolution in microstructure and corrosion behavior of the coatings with the change in x was investigated comprehensively. Results indicated that the dilution rate of the coatings was gradually increased with the increase in x. The coatings with x = 1.00 and 1.50 were composed of a single solid solution with the face-centered cubic (FCC) structure. A small number of fine equiaxial FeAl3 particles were also observed in the coatings with x = 0.50, 0.75, 2.00. Corrosion resistance of the coatings was improved first and then decreased with the increase in x in the electrochemical tests carried out in 0.1 mol L−1 HCl and 3.5 wt% NaCl solutions. The similar phenomenon was observed in the immersion tests. The optimum corrosion resistance was obtained in the coating with x = 1.50, in which the content of Cr reached the maximum value. Corrosion resistance of 45# steel could be considerably improved by laser cladding an AlCoCrxFeNi HEA coating on its surface.