Study on electrochemical corrosion behavior of Y2O3-doped AlCrFeNiTi high-entropy alloy laser cladding coatings

To enhance the corrosion resistance of agricultural soil-contacting implements, particularly subsoiler shovels subjected to prolonged soil exposure, AlCrFeNiTi high-entropy alloy (HEA) coatings with varying additions of Y 2 O 3 (0, 3, 6, and 9 wt%) were fabricated on 65Mn steel substrates using laser cladding. The coatings were systematically investigated in terms of their microstructure and corrosion resistance. Phase composition was analyzed by X-ray diffraction (XRD). Microstructural features of both cross-sections and surfaces were examined using scanning electron microscopy (SEM). Furthermore, X-ray photoelectron spectroscopy (XPS) was employed to characterize the chemical composition and elemental oxidation states of the passive films formed after corrosion. Systematic probing of electrochemical corrosion tendencies was carried out upon both the uncoated substrates and those specimens layered with coatings, within an environment constituted by a 3.5 wt% NaCl solution maintained under uniform conditions. From these investigations, it emerges that the HEA coatings manifest predominantly as a phase typified by body-centered cubic (BCC) structure; concomitant with this is the generation of intermetallic composites comprising (Fe, Cr)–Al during the cladding sequence. The incorporation of Y 2 O 3 promoted the formation of Y–Ti–O complex oxides and facilitated the development of dense surface films containing Cr 2 O 3 and Al 2 O 3 . Furthermore, Y 2 O 3 doping improved the coating density, significantly reducing surface porosity and structural defects, thereby hindering the penetration of corrosive agents. The dominant corrosion mechanism of the Y 2 O 3 -doped coatings was identified as intergranular corrosion. Among all tested compositions, the coating with 9 wt% Y 2 O 3 exhibited the best corrosion resistance, characterized by a corrosion potential of −0.9682 V (vs. SCE), a corrosion current density of 5.621 × 10 −6 A cm −2 , and an impedance value of 2694.45 Ω cm 2 .