Brazing process of alumina ceramic to steel

Ceramics/metals joining is widely applied in aerospace and electronic industry,instruments,fuel cells fields.Al₂O₃ ceramic was brazed to Q235 steel in vacuum with active filler alloys Cu75Ti25,Cu70Ti30,Cu80Ti20 and Cu85Ti15,respectively.The bending strength of each specimen and the microhardness of the interface were tested,and the results showed that the Cu75Ti25 filler was the best ratio of filler metal,and the optimum brazing parameters were 1 100℃ and 20 minutes.At the optimized temperature,the active filler alloy melts sufficiently and fills joint gap,then mutually diffuse into ceramic and steel sides.The bonding interface is composed of three layers of reaction layer formed by microporous ceramics filled with liquid active alloy,Ti-Cu alloy layer and steel side diffused layer.XRD analysis shows that AlCu,Cu₃TiO₄,TiC,TiFe₂ phases form in the bonding zone,and the microstructure of bonding area is dense and there are no defects.Accordingly a good metallurgical combination of ceramic/steel is achieved.