Superior corrosion resistance dependent laser energy density in (CoCrFeNi)₉₅Nb₅ high entropy alloy coating fabricated by laser cladding

The (CoCrFeNi)₉₅Nb₅ high entropy alloy (HEA) coatings were successfully fabricated on the substrate of Q235 steel by laser cladding technology. These (CoCrFeNi)₉₅Nb₅ HEA coatings possess excellent properties, especially its corrosion resistance is obviously better than that of some typical bulk HEA and common engineering alloys. In order to obtain appropriate laser cladding preparation process parameters, the effects of laser energy density on the microstructure, microhardness and corrosion resistance of (CoCrFeNi)₉₅Nb₅ HEA coating were emphatically studied. As the laser energy density increases, the precipitation of Laves phase in (CoCrFeNi)₉₅Nb₅ HEA coating gradually decreases, and the diffusion of Fe element in the substrate intensifies, which affects the integrity of the (CoCrFeNi)₉₅Nb₅ HEA, resulting in the microhardness of (CoCrFeNi)₉₅Nb₅ HEA coatings decreasing. Moreover, the relative content of Cr₂O₃, Cr(OH)₃, and Nb₂O₅ in the surface passive film of the coating decreases with the increasing of energy density, making the corrosion resistance decrease. This study demonstrates the controllability of high-performance HEA coating with laser cladding technology, which has certain guiding significance for laser cladding preparation of other CoCrFeNi-system HEA coatings.