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

Abstract

In this work, a novel FeCrMnVSix (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 FeCrMnVSix 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 Si2.0 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.