Effect of Rare Earth La2o3 on the Microstructure and Corrosion Resistance of Cocrfenimosi High Entropy Alloys

Abstract

In this work, the effect of incorporation of trace amounts of La2O3 into the CoCrFeNiMoSi high-entropy alloy system on its corrosion resistance in neutral cl ionic salt solutions was systematically investigated. CoCrFeNiMoSi high-entropy alloy (HEA) coatings and CoCrFeNiMoSi-0.5% La2O3 HEA coatings were prepared by laser melting technique. The microstructure, phase composition, and electrochemical corrosion performance were characterized by X-ray diffraction, scanning electron microscopy, electrochemical workstation, and X-ray photoelectron spectroscopy. The experimental results showed that the microstructure consisted mainly of face-centered cubic structure (FCC), body-centered cubic structure (BCC), and Si-rich intermetallic compounds. Among them, the incorporation of La2O3 promoted the formation of the FCC phase. In comparison to the CoCrFeNiMoSi HEA coating, the CoCrFeNiMoSi-0.5% La2O3 HEA coating increased the corrosion potential by 158 mV and reduced the self-corrosion current density by one order of magnitude. The XPS data showed a significant increase in the Cr content and oxide content of the passive film in the presence of La2O3 in the HEA, making the passivated film more protective. Therefore, the potential application of rare earth lanthanum oxide to effectively improve the corrosion resistance of HEA coatings.

Keywords: High Entropy Alloys, Electrochemical Corrosion, Rare-earth, Laser cladding, Passive film