Effect of rare earth oxide CeO2 on microstructure and surface properties of laser cladded CoFeCrNiSiB high-entropy alloy coatings

Abstract

CoFeCrNiSiB high-entropy alloy coatings with different content of REO (rare earth oxide) CeO2 were fabricated on the surface of corrosion-resistance steel plates by using laser cladding process. The surface properties of the cladded coatings including wear and corrosion resistance were evaluated by friction wear equipment and electrochemical workstation, respectively, while the microstructure was observed by scanning electron microscope, energy dispersive spectrometer, x-ray diffractor and transmission electron microscope. When the CeO2 content was not higher than 2%, the wear resistance and corrosion resistance of cladded coating was improved with the increased of CeO2 content. However, when the CeO2 content was between 2% and 4%, the wear resistance and corrosion resistance of cladded coatings decreased with the increased of CeO2 content. The corrosion resistance evaluation environment included 2 N(1 mol l−1) H2SO4 and 5 wt% NaCl solutions. Equi-axed grains of the cladded coatings got refined by adding CeO2, the grains were most refined at 2% in the range of 0%–4% CeO2 content. However, when too much CeO2 (>2%) was added, CeO2 would exist as an oxide in the intergranular area. Therefore, grain refinement could improve the surface properties of coatings, while the presence of intergranular oxides would make the surface properties of coatings worse.