Tailoring high-temperature oxidation resistance of FeCrMnVSi_x high entropy alloy coatings via building Si-rich dendrite microstructure

In this work, a novel FeCrMnVSi_x (x = 0, 0.5, 1.0, 1.5, 2.0) high entropy alloy (HEA) coatings with dendrite structure were successfully designed and prepared by laser cladding technology. The evolution law of the coatings' microstructure and high-temperature oxidation resistance behavior were systematically studied, and the influencing mechanism of Si in FeCrMnVSi_x HEA was proposed. Results showed that the HEA coatings were dense and uniform, exhibiting the characteristics of metallurgical bonding. And the HEA coatings had a single BCC solid solution structure. Moreover, the addition of Si aggravated the degree of lattice shrinkage and lattice distortion of HEA. Based on the non-equilibrium solidification effect of the laser cladding, the Si-rich dendritic structure was formed in the coating, which was strengthened with the increase of Si content. Additionally, the high-temperature oxidation resistance of HEA coatings was significantly improved. The Si_2.0 HEA coating reduced the mass gain by about 75%, compared to the substrate. The excellent oxidation resistance was attributed to the thermodynamically preferential oxidation of Si in Si-rich dendritic structures, further forming a dense SiO₂ layer on the surface of the HEA coatings.