Mechanical durability of solid oxide fuel cell glass-ceramic sealant/steel interconnect joint under thermo-mechanical cycling

A testing method is developed to quantitatively determine the thermo-mechanical cycling life in oxidizing atmosphere for the joint between a solid oxide fuel cell glass-ceramic sealant and a ferritic stainless steel interconnect. Thermo-mechanical cycling tests are performed under cyclic shear or tensile loading in conjunction with cyclic temperature variance between 40 °C and 800 °C. Results reveal thermo-mechanical cycling life under both shear and tensile loadings increases with a decrease in end stress at 800 °C, for a certain end stress at 40 °C. Nevertheless, for a certain end stress at 800 °C, the tensile thermo-mechanical cycling life increases with a decrease in end stress at 40 °C, while the shear thermo-mechanical cycling life is independent of end stress at 40 °C. A difference in fracture pattern is also observed between shear and tensile loadings. For shear loading, fracture mainly takes place along the interface between glass-ceramic sealant and an oxide layer, such as BaCrO₄ or Cr₂O₃. However, for tensile loading, fracture mainly occurs within the glass-ceramic layer, following crack initiation at the interface of Cr₂O₃/sealant or Cr₂O₃/BaCrO₄.