Structure and corrosion behavior of FeCoCrNiMo high-entropy alloy coatings prepared by mechanical alloying and plasma spraying

FeCoCrNiMo_x composite powders were prepared using the mechanical alloying technique and made into high-entropy alloy (HEA) coatings with the face-centered cubic phase using plasma spraying to address the element segregation problem in HEAs and prepare uniform HEA coatings. Scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry were employed to characterize these coatings’ microstructure and phase composition. The hardness, elastic modulus, and fracture toughness of coatings were tested, and the corrosion resistance was analyzed in simulated seawater. Results show that the hardness of the coating is HV_0.1 606.15, the modulus of elasticity is 128.42 GPa, and the fracture toughness is 43.98 MPa·m^1/2. The corrosion potential of the coating in 3.5wt% NaCl solution is –0.49 V, and the corrosion current density is 1.2 × 10⁻⁶ A/cm². The electrochemical system comprises three parts: the electrolyte, the adsorption and metallic oxide films produced during immersion, and the FeCoNiCrMo HEA coating. Over increasingly long periods, the corrosion reaction rate increases first and then decreases, the corrosion product film comprising metal oxides reaches a dynamic balance between formation and dissolution, and the internal reaction of the coating declines.