Study on creep damage evolution of braze sealant of solid oxide fuel cell by small punch test

Obtaining the creep properties of sandwich structure of brazed joint has always been a challenge. Based on Wen-Tu creep-ductility exhaustion model, a subroutine for creep damage evolution of braze sealant of solid oxide fuel cell (SOFC) was developed in the finite element model of small punch test (SPT) using ABAQUS software. The evolution and characteristics of creep damage of the brazed joint with 304 stainless steel as base metal were studied by combining experiment and finite element analysis. The relationship between the change rate of central creep deflection and the creep strain rate of the brazed joint under different loads was obtained. The evolution of creep damage and crack propagation of brazed joint in the small punch creep test is clarified. The results show that the main fracture mode of brazed joint under multiaxial stress is brittle fracture, and the creep crack originates at the lower surface of base metal, which is 0.85 mm far away from the center of SPT specimen, and gradually propagates to the upper surface of base metal and the lower surface of the solder layer until fractures.