单相CoCrFeNi高熵合金的组成元素对其在NaCl溶液中的耐蚀性能的影响

High entropy alloys (HEAs) origin from a new alloy design concept with multi-principal elements, which have attracted significant interests in the past decade. The high configurational entropy in HEAs results in simple solid solutions with fcc and bcc structures. Especially, the single solid solution CoCrFeNi alloy exhibits excellent properties in many aspects, such as mechanical properties, thermal stability, radiation resistance and corrosion resistance. The excellent corrosion resistance of CoCrFeNi alloy is ascribed to the single-phase structure and uniform element distribution coupled with much higher Cr content than stainless steel. The single-phase structure and uniform element distribution can prevent the occurrence of localized corrosion, and higher Cr content can protect the alloy surface better with the form of oxidation film. Moreover, the corrosion resistance of CoCrFeNi-based HEAs, such as CoCrFeNiAl_x , CoCrFeNiCu_x , CoCrFeNiTi_x, have also been extensively investigated. In most CoCrFeNi-based HEAs, the elements of Co, Cr, Fe and Ni are with equal-atomic ratio. However, the equal-atomic ratio is not necessary to obtain satisfactory properties and to ensure the single fcc structure in Co-Cr-Fe-Ni system. Accordingly, it is essential to further consider the effect of alloying elements on the corrosion resistance in Co-Cr-Fe-Ni HEA. In this work, the effect of Co, Fe and Ni elements on the corrosion resistance of single fcc Co-Cr-Fe-Ni system with concentrated constitution but different atomic ratios in 3.5%NaCl solution are investigated by using LSCM and EIS. The potentiodynamic polarization results indicate that the increase of Fe and the decrease of Ni will decrease the passivation current density of the alloys when the Co and Cr contents are equal. With the increase of Co and the decrease of Ni, the alloys show smaller passivation current density and better corrosion resistance when the Fe and Cr contents are equal. With the decrease of Co and the increase of Fe and Ni, the alloys show higher corrosion potential and smaller corrosion tendency when the Cr content is constant. These results will be helpful for the design of corrosion resistant HEAs in NaCl aqueous solution.