The role of Dy doping on oxidation behavior of Co-40Mn/Co coating for solid oxide fuel cell metal interconnects

Co-38Mn-2Dy and Co-40Mn alloy coatings are prepared by using high-energy micro-arc alloying process (HEMAA) and a Co transition layer is firstly obtained on 304 SS. Microstructures and compositions of Co-Mn(Dy)/Co coatings after preparation and oxidation are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Coatings are the splash appearance and fine-grained structure with a metallurgical bonding to substrate. The addition of Dy in Co-Mn coating can effectively improve the oxide scale adhesion and reducing the high temperature oxidation rate of coating. The outward diffusion of Fe and Cr from substrate is remarkably suppressed by the external oxide layer for Co-38Mn-2Dy/Co coating. And Dy-rich oxides, Mn-rich oxides and oxide pegs are found in oxide layer after oxidation for 100 h, respectively. Co-rich oxides favor to form on the top scale because of high oxygen partial pressure. The value of area specific resistance (ASR) is measured to be low for Co-38Mn-2Dy/Co coating at 800 °C.