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Abstract: Reliable Si3N4/Si3N4 joints were obtained using Cuph name="sbnd" />Ti as filler alloy. The effect of holding time on interfacial microstructure and bonding strength of the joints was investigated. All the joints consist of continuous reaction layer (fine-grain TiN), discontinuous reaction layer (coarse-grain TiN), Cu-based solid solution and reaction products. Prolonged exposure to the elevated temperature causes the thickness of the discontinuous reaction layer to increase, due to the coarsening of TiN grains. And the amount of Pdincreases instead of Ti With the increase of holding time, the bonding strength of the joints decreases. The formation of a reaction layer with a suitable thickness promotes the improvement of bonding strength of joints. [Copyright &y& Elsevier]

Abstract: Si3N4 ceramic has been joined successfully to itself by brazing in a vacuum at 1373–1573K holding for 1.8ks using a Cu76.5Pd8.5Ti15 alloy filler. By observation and analysis of the microstructure of the joints, it is found that the joints comprise three parts: (1) a continuous reaction layer of TiN between Si3N4 and filler alloy, (2) a discontinuous reaction layer containing TiN, Pd2Si and Ti5Si3 connecting the continuous reaction layer, and (3) the Cu-based solid solution in the mid of the joint and some reaction products (TiN, Pd2Si, PdTiSi and Ti5Si3) in the solution. With increasing brazing temperature, both the thickness of the continuous reaction layer and amount of reaction phases increase, which improves the bending strength of the joints. When the brazing temperature surpasses 1473K, voids are formed in the joint because of the decomposition of the Si3N4 ceramic, leading to a decrease of the bond strength. The room-temperature bending strength of the joint brazed at 1423K reaches a maximum value of 155.8MPa. [Copyright &y& Elsevier]