Diffusion simulation in SUS 430 stainless steel interconnect with a MnCu coating at 800 ºC

(MnCu)3O4 spinel coatings are good candidates for Cr-positioning protection on stainless steel interconnect. The spinel coatings can be formed by sputtering MnCu metallic coatings followed by a hot oxidation treatment. To understand how the elements diffuse in the MnCu/steel system, a homogenization diffusion couple model was built with considering Mn oxidation at coating surface. According to the simulation, the diffusion of Fe from the steel substrate to the MnCu coating occurred, while Cr was almost trapped under the MuCu coating. Thermodynamic calculation explained why. In addition, an inward diffusion of Mn from the coating to the substrate also took place with formation of a concentration peak of Mn at the interface. The simulation results were compared with the experimental ones. The elemental diffusion behavior was discussed by considering the surface oxidation.