Microstructure and Mechanical Properties of Reactive-Air-Brazed 3YSZ/Crofer 22 APU Joints at Ambient Temperature

The growth of inventive high-temperature electrochemical devices such as solid oxide fuel cells constitutes a major task in brazing technology of ceramic–metal joints. In this work, reactive air brazing was used and the joining characteristics of 3YSZ with Crofer 22 APU have been systematically analyzed for three different brazing temperatures (1000, 1050 and 1100 °C) and two dwell times (5 and 30 min). The joints have been brazed successfully using the Ag–4CuO filler alloy. This braze filler metal was manufactured by an arc PVD (physical vapor deposition) process. Further, sufficient wetting of the zirconium oxide was achieved. The morphology of the oxide reaction layer at the steel side had a major influence on the shear strength of the brazed joints. A maximum average shear strength of 101 ± 4 MPa was obtained for a temperature of 1050 °C and a dwell time of 5 min.