Effect of Cu on microstructure and properties of Co₂CrFeNiMnCu_x high-entropy alloy coatings prepared by laser cladding

Abstract

High-entropy alloy coatings (HEACs) of Co2CrFeNiMnCu x ( x = 0, 0.25, 0.5, 0.75, 1.0, 1.25) were fabricated on Q235 steel surfaces by laser cladding. A portion of the HEACs ( x = 0, 0.5 and 1.25) displayed a dual-phase FCC structure, while the remaining portion ( x = 0.25, 0.75 and 1.0) exhibited a single-phase FCC structure. Furthermore, as the Cu content increased, the grain size of the coatings became finer and elongated. Due to the unique processing technology of laser cladding, the HEACs exhibited a hardness gradient from the top to the substrates. Cu segregated within the crystal and accumulated near the grain boundaries. The primary mechanism for protecting the steel substrate through coatings was passive films protection. Remarkably, the coatings demonstrated better anti-corrosion properties when the Cu content was 0.25, with a charge transfer resistance of 9.528 × 104 Ω cm2, corrosion potential of −0.387 V and corrosion current density of 3.125 × 10−7 A/cm2.