A Novel Silver-Based Braze Sealant for Metal-Supported Solid Oxide Fuel Cells Applications

A proprietary Ag-Ge-Si braze system was developed by INER for use as high-temperature sealing materials for MS-SOFCs applications. For cross-sectional microstructures observation, filler/interconnect brazed joints revealed that there were evident inter-diffusion between the brazing filler and interconnect. Fe-Cr-Si phase was observed at the interface after brazing at elevated temperatures. As for the tensile and shear strength of interconnect joints, the results showed that the optimal joint strength were about 70 and 47 MPa, respectively after brazing at 850 °C for 30 min. The leak rates for the filler/interconnect brazed joints were tested respectively under the conditions of thermal aging (750 °C for 1,000 hours in He/air) and thermal cycling (200-750 °C for 30 cycles, 10 °C/min in He/air). Results indicated that the average leak rates are in the range of 10-5~10-4 mbar∙l/s/cm and the interface of Ag-Ge-Si/interconnect joints still remained rigidly contacted, meeting the hermetic requirements for the MS-SOFCs applications.