Hot corrosion resistance of AlCoCrFeNi2.1 coatings at 900 °C

By examining the grain size effects of AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) coating and assessing the residual stress state on the coating surface, it is found that grain refinement significantly enhances grain boundary diffusion capability, reduces the critical concentration of elements required to form a protective oxide film, and strengthens the self-healing capability of the Al 2 O 3 oxide layer. This, in turn, improves the integrity and stability of the oxide layer on the coating surface, thus enhancing the hot corrosion resistance of the coatings. Additionally, a synergistic effect arises between low-angle grain boundaries and uniformly distributed dislocations, enabling the rapid formation and stable growth of the oxide layer, which contributes to its compactness and continuity, further enhancing hot corrosion resistance of the coatings. Moreover, the protective effect of residual compressive stress on the AlCoCrFeNi 2.1 EHEA coating surface surpasses the influence of microstructural characteristics such as grain size, low-angle grain boundary volume fraction, and dislocation density. Therefore, in high-temperature corrosion environments, the rational design and control of residual compressive stress provide an effective approach to improving the hot corrosion resistance of AlCoCrFeNi 2.1 EHEA coatings.