Evolution of microstructure and properties of AlCoCrFeNi high-entropy alloy coatings fabricated at different laser power levels

In the present study, AlCoCrFeNi high-entropy alloy coatings were deposited on a Q355 steel substrate using a coaxial powder-feeding laser cladding technique. Subsequently, the evolution of the microstructure, mechanical properties, and corrosion resistance of these coatings produced at different laser power levels was then systematically investigated. Regardless of the laser power level, the results demonstrated that the coatings consistently comprised typical A2 and B2 phases. With increasing laser power, the surface quality of the coatings progressively improved, as evidenced by a reduction in the grooves formed during the cladding process. The hardness of the coatings initially increased with laser power, reaching a maximum value of 553 HV_0.2 at 1750 W. This peak hardness was attributed to optimal grain refinement. However, further increases in laser power resulted in a decrease in hardness due to grain coarsening. The friction coefficient was lowest at a laser power of 1750 W with a value of 0.48. The primary wear mechanisms were abrasive wear, oxidative wear, and adhesive wear. Electrochemical corrosion tests showed that the corrosion of the coatings was mainly due to galvanic and intergranular corrosion. The coating fabricated at 1750 W demonstrated the best protective performance, as evidenced by its lower corrosion potential and lower charge transfer resistance, indicating superior passivation film stability.