Reactive air brazing of 3YSZ ceramic to aluminized Crofer22H stainless steel using Ag–CuO fillers

Abstract

In this work, an effective protected Al₂O₃ layer was fabricated first on the surface of Crofer22H by reactive air aluminization to suppress cathodic poisoning in solid oxide fuel cells. Then, the reactive air brazing of aluminized Crofer22H to 3YSZ ceramics was carried out by using Ag–CuO fillers. The effects of CuO content and brazing temperature on the interfacial microstructure and mechanical properties of the joints were studied in detail. The results indicated that maintaining a continuous Al₂O₃ layer was the prerequisite for achieving a reliable joint. And the interfacial reaction gradually became intense with the increase of CuO content, and the continuity of the Al₂O₃ layer was disrupted as it was increased to 6 mol%. The well-connected joints could be achieved when brazing at 970–1100°C with Ag–2CuO filler. The interfacial microstructure did not obviously change with increasing temperature, and the joint strength was stable at ∼35 MPa. While the interfacial reaction gradually weakened with increasing temperature as brazing with Ag–4CuO filler, the well-connected joints were obtained when brazing above 1000°C, and the maximum shear strength of ∼44.3 MPa was obtained when brazing at 1050°C for 30 min.