Microstructure and corrosion behavior of CeO2/FeCoNiCrMo high-entropy alloy coating prepared by laser cladding

In this work, FeCoNiCrMo high-entropy (HEA) coating and CeO2/FeCoNiCrMo composite coating were successfully prepared on the surface of TC4 alloy by laser cladding technology. The macromorphology, microhardness and corrosion resistance of FeCoNiCrMo coating with rare earth oxides CeO2 were characterized in detail. The addition of CeO2 powders reduced the crack sensitivity of HEA coating, and CeO2 did not change the phase composition of the coating (BCC phase). SEM analysis revealed that CeO2 was mainly distributed on the grain boundary, which refined the grain and improved the strength and toughness of the coating. Owing to the solution strengthening and dispersion strengthening effects of HEA coatings, the microhardness of HEA coating was enhanced by 2.7 times compared with TC4 substrate. In 3.5% NaCl solution, there were corrosion products generating on TC4 surface, while the corrosion form of HEA coating was pitting corrosion. After adding CeO2 powder, the refined grain structure formed higher density and more stable passive film, which inhibited pitting. Compared with TC4 alloy, HEA coating had lower corrosion current density and higher polarization impedance, which proved that FeCoNiCrMo coating could improve the corrosion resistance of TC4 alloy.