Interfacial reactions between Ni/430 stainless steel as the interconnect material and Ag–Cu alloy fillers in a solid oxide fuel cell system

Liquid/solid reaction couples were used to investigate the interface reactions between steel interconnect materials, such as Ni and 430 stainless steel (430SS), and Ag–Cu alloys used as fillers in a solid oxide fuel cell system. The Cu atoms diffused into the Ni side, forming a (Cu, Ni) solid solution at the Ag–Cu/Ni interface. The (Cu, Ni) solid solution acts a diffuse barrier that prevents the diffusion of Cu atoms into the Ni side. In the Ag–Cu/electroplating Ni/430SS couple, the reaction layer is the γ-(Fe, Ni) phase and the interface is smooth when the Cu content is less than 20 at.% in Ag–Cu alloys. As the Cu content increases over 20 at.%, the interface morphology becomes rougher and the reaction layers are (Cu, Ni)+ γ-(Fe, Ni) phases.